Monitoring of Patients with Head Injuries GEORGE T. TINDALL, M.D., JOHN M. PATTON, M.D., M.P.H., JAMES J. DUNION, B.S., AND MARK S. O'BRIEN, l\1.D. A major medical problem is the increasingly high incidence of head injuries. The frequency of head injuries in the United States from all types of trauma including industrial, motor vehicle, and household accidents in 1971 was 8,039,000, which included 1,888,000 skull fractures and intracranial injuries (58). The mortality in 1973 from head injuries of all types was 40,000, and another 1,300,000 persons were disabled (43). Statistics from 1966 revealed that 70 per cent of automobile accident victims incur head injury of some type (42), and more recent data (1973) (58) showed that 50 per cent of all motorcycle-related deaths are due to head injury. From these data, one can readily appreciate the magnitude of problems associated with craniocerebral trauma. Although recent reduction in speed limits on U. S. freeways has resulted in a noticeable decrease in the incidence of head injury, nevertheless, craniocerebral trauma remains a major neurosurgical problem. In recent years, it has become established that the management of head injury is considerably facilitated by continuous monitoring of several physiological parameters, especially intracranial pressure (ICP) (36, 50) and certain respiratory functions (10). For instance, elevated ICP can be recognized early and treated effectively by several methods when continuous ICP recordings are available. It is well known that certain pathological changes in the brain are caused either directly or indirectly by marked elevations of ICP. In an autopsy study, Sevitt (52) found that transtentorial herniation of the hippocampal uncus was the cause of death in 34 per cent of 250 patients who died as a result of automobile accidents. Further, he noted that this pathological change was a secondary event due to cerebral edema, a finding which implies that neurosurgical intervention at some point in its development may favorably affect the clinical course of the patient. Thus, it is our opinion that when continuous monitoring of several physiological parameters is performed, alterations in the anatomical, physiological, and metabolic parameters of the central nervous system (CNS) consequent to trauma may be detected early and various medical and surgical therapies begun before irreversible CNS damage has occurred. Diagnostic evaluation, monitoring, and therapeutic management are important and interrelated processes in the total care of head-injury patients 332

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and essentially each process is begun when the physician initially receives the patient. For example, assessment and correction of an obstructed airway and subsequent evaluation of its patency by determining arterial blood gases involve all three processes-evaluation, management, and monitoring. Thus throughout the stages of diagnostic evaluation and treatment, monitoring techniques serve to assess the patient's condition. In this report, the indications, criteria for patient selection, and techniques for monitoring patients with acute head injury will be described. Additionally, the initial diagnostic evaluation of patients with head injury, monitoring of infants and children, and the potentially valuable role of computers in monitoring head injury patients will be enumerated. DIAGNOSTIC EVALUATION-ADULTS*

Patients with a head injury that produces a loss of consciousness or a skull fracture with or without unconsciousness should be seen and evaluated by a neurosurgeon. The following studies should be performed in patients evaluated for head injury.

History The exact details of the trauma and an account of the patient's state of consciousness immediately after injury are important and often are overlooked in the rush to care for the injured person. If the patient is stuporous or comatose, a history should be obtained from any available witness. A history of amnesia concerning the accident indicates a significant degree of cerebral dysfunction as does the history of unconsciousness after the accident, even if the patient is alert at the time of examination in the hospital.

Examination Complete physical and neurological examinations should be carried out on all patients with head injuries. The physician should carefully evaluate: (1) airway, (2) level of consciousness, (3) presence of focal neurological signs, and (4) presence of shock and multiple injuries including spinal cord injury. AIRWAY

In the patient with relatively minor head trauma who is alert or only slightly drowsy, there is usually no reason for concern over the status of the airway. In patients with more serious injury and who are stuporous or comatose, it becomes important to ensure that a patent airway exists. When signs of upper airway obstruction (retraction, stridor, cyanosis, etc.) are

* For purposes of this report which contains a section on evaluation and monitoring of pediatric cases, all patients over the age of 15 years are considered as adults.

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present, an endotracheal tube should be inserted whenever simpler corrective measures such as suctioning or changing position do not adequately relieve the obstruction. Maintenance of an adequate airway and oxygenation as determined by serial arterial blood gas determinations prevents hypoxia and hypercarbia, both of which contribute to increased ICP. Once the airway is established, a means of positive pressure breathing should be available such as an Ambu bag (Air-Shields, Inc., Matboro, Pa.) or an intermittent positive pressure ventilator. A cuffed endotracheal tube is desirable so that positive pressure breathing may be accomplished if needed in resuscitation or the administration of anesthesia. When an endotracheal tube cannot be inserted readily, a tracheostomy should be performed. While the latter procedure may be lifesaving, one should be aware that complications (bleeding, pneumothorax, tracheal stenosis, etc.) may accompany tracheostomy (51). ESTABLISHING LEVEL OF STUPOR AND COl\IA

There is a need for a simple, practical classification of stupor and coma, as the level of consciousness is one of the more important indicators of the head injured patient's condition. The classification shown in Table 19.1 is one that is in use at our institution and is based on the patient's state of awareness and response to name calling and light and deep painful stimuli. Such a classification serves not only to determine the level of consciousness and the effects of therapy but also as a base line for subsequent examinations. In our hands, this classification has proved to be sufficiently detailed to accurately describe a patient's condition and yet is not so unwieldy as to discourage its use. In addition, it is a concise and effective method of communicating with other physicians and paramedical personnel. NEUROLOGICAL EXAMINATION

A complete neurological examination should be performed and all abnormal signs noted, thus documenting any focal CNS damage. The optic fundi should always be examined, but, in general, mydriatic drugs should not be used to facilitate this examination since pupillary paralysis removes an important indicator of 3rd nerve and brain stem malfunction in the head injured patient. Light pain is applied to the face, neck, trunk, and all extremities using light pin-prick. Deep pain is tested by firm supraorbital pressure, firm squeezing of the anterior axillary fold, or testicular compression. It is important to note the patient's response-s-whether appropriate or inappropriate-during both light and deep pain testing. The physician should be aware that occasionally a falsely lateralizing hemiplegia (i.e., ipsilateral to the lesion) occurs in patients with acute head injury, particularly those with a subdural or epidural hematoma, This

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TABLE

19.1

Grades of Stupor and Coma Responds Appropriately to: Grade

State of Awareness

--Drowsy, lethargic, indifferen t and uninterested I and/or belligerent and uncooperative; does not lapse into sleep when left undisturbed

Calling Name

Light Pain

Deep Pain

Yes

Yes

Yes

2

Stuporous; will lapse into sleep when not disturbed; may be disoriented to time, place, and person

No

Yes

Yes

3

Deep stupor; requires strong pain to evoke movement

No

No

Yes

4

Does not respond appropriately to any stimuli; may exhibit decerebrate or decorticate posturing; retains deep tendon reflexes

No

No

No

5

Does not respond appropriately to any stimuli; flaccid; no deep tendon reflexes

No

No

No

finding was first described in 1929 by Kernohan and Woltman (26) and results from compression of the cerebral peduncle against the edge of the tentorium cerebelli opposite to a supratentorial mass lesion. Unilateral dilatation of a pupil during the first several hours after injury usually correctly indicates the side of an acute expanding intracranial lesion (47). PHYSICAL EXAl\IINATION

A careful examination should be made of the head and neck. Evidence of hemorrhage either behind the ear or in the upper eyelid usually indicates a basal skull fracture. Inspection of the nostrils and external auditory canals should be carried out for the presence of blood and/or cerebrospinal fluid (CSF). Pain and stiffness in the neck often indicate associated cervical spine fractures which frequently are overlooked in the patient with multiple trauma. Hypotension rarely is the result of a closed head injury and usually is a consequence of bleeding into the thorax, abdomen, or into the area of a long bone fracture. The etiology of the blood loss is determined by using an 18 gauge needle for immediate abdominal and chest.taps, which may reveal the presence of nonclotting blood (24). However, the absence of blood does not rule out an intra-abdominal or thoracic injury.

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X-rays

In all patients who experience head injury, the physician should obtain good quality skull x-rays in the anteroposterior (AP), lateral, and anteroposterior half-axial (Towne) projections to demonstrate skull fractures, to determine the pineal position (if calcified), and to visualize foreign bodies (bone or missile fragments) within the cranial cavity. Additionally, when the head injury has been more than minor in nature, cervical spine films, especially in the lateral projection, should be made to exclude the possibility of a fracture-dislocation of the cervical spine (23). Shrago (53) has commented on the association of cervical spine injuries in head injury, and has noted that 53 per cent of patients with upper cervical spine injuries have concomitant head injuries. Echoencephalography

Echoencephalography is a valuable screening test, but is not a definitive diagnostic procedure. Properly done, echoencephalography accurately determines whether or not the midline structures have shifted. A negative (midline) echoencephalogram does not definitively rule out an acute expanding intracranial lesion since not all traumatic hematomas cause a shift of the midline structures. On the other hand, a positive echoencephalogram (midline shift> 3 mm.) strongly indicates an expanding lesion which should be further investigated by cerebral angiography. As echoencephalography is not a definitive examination, it should not be considered a necessary diagnostic step in the evaluation of head injury patients. Cerebral Angiography

Cerebral angiography is the most definitive procedure* currently available for evaluating patients with acute head injuries and is recommended in adult head injury patients who have one or more of the following indications: 1. Grade 2 or greater level of stupor and coma during period of initial examination. 2. Focal neurological signs, e.g., hemiparesis, unilateral dilatation of pupil, etc. 3. Pineal shift of 3 mm. or more on an AP skull film. 4. Echoencephalogram midline shift of 3 mm. or more. 5. Gunshot wounds of the brain.

* Continued clinical experience with computerized transaxial tomography may ultimately show that this diagnostic procedure is a more practical means for evaluating acute head injury patients than cerebral angiography. Only time and experience can answer this question.

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The history of a previous allergic or chemotoxic reaction (33) to an iodide contrast study contraindicates angiography. Bilateral cerebral angiography can be performed with either the direct carotid or the transfemoral catheter technique. Both methods can be carried out using local anesthesia and percutaneous techniques. We prefer the transfemoral method, but either method yields films of good diagnostic quality, with a low incidence of morbidity and mortality (56, 59). Head injury patients who are suspected of having a rapidly expanding acute extradural or subdural hematoma and who are showing a progressive decrease in their level of consciousness should undergo immediate trephination. In these cases, the risk of irreversible CNS changes does not permit the neurosurgeon to obtain the usual diagnostic studies such as skull x-rays, cerebral angiography, etc. Radioactive Brain Scanning

In acute head injuries there may be uptake of radioactivity by lesions of soft tissues and bones, a finding which may either obscure or mimic increased activity within the brain itself. Also, considerable time and patient cooperation are required in order to obtain a satisfactory diagnostic brain scan. Because of these reasons, radioactive brain scanning is not a practical tool in the diagnostic management of acute head injuries. The more important and useful indications of the scan are in traumatic lesions with a subacute or chronic evolution, such as some brain contusions and intracerebral and chronic subdural hematomas (40). Electroencephalography

In the initial management of acute head injuries, electroencephalography is of little diagnostic value. However, during the subacute and chronic phases of head injury, it may demonstrate focal abnormalities which would indicate the presence of discrete areas of brain damage or unilateral hematoma (10). Pneumoventriculography

Air ventriculography has been recommended by Vries and co-workers (61) as a diagnostic procedure in evaluating acute head injury. A frontal twist drill ventriculostomy provides a means of withdrawing a small amount of CSF and instilling air into the ventricular system in an attempt to demonstrate midline shifts. While this method may yield important information, there are certain drawbacks to the technique which should be considered. Bilateral traumatic lesions, e.g., acute subdural hematoma, may cause no midline shift and could be missed with this method. Also, Cooper and

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Hulme (11) have demonstrated that the injection of small volumes of air (5 ml.) into the ventricular system can initiate a significant increase in ICP in certain patients with intracranial lesions, although this risk can be minimized by prior removal of a volume of CSF equal to the amount of air to be injected. While this diagnostic procedure may have application in certain clinical situations, we believe that further evaluation of the method is indicated before it can be recommended as a routine part of the diagnostic evaluation of the head injured patient. Pneumoencephalography Pneumoencephalography has no application in the diagnostic management of acute head injuries. In subacute or chronic cases, however, this procedure may demonstrate post-traumatic anatomical changes due to communicating hydrocephalus, localized porencephaly, or cortical atrophy. Trephination Trephination is a procedure which may be both diagnostic and therapeutic. If, for instance, the arteriogram is unsatisfactory and the clinical findings indicate the possibility of a subdural or epidural hematoma, the neurosurgeon should perform diagnostic trephination. Three appropriately spaced trephine openings (frontal, temporal, and parietal) are placed on each side of the head and the dura mater is opened to inspect the subdural space and underlying cerebral cortex. Some authors have recommended using twist drill openings as a diagnostic technique in acute head injury. On the basis of a large clinical experience, Rand and colleagues (48) concluded that the procedure has a high degree of sensitivity and specificity and is relatively safe. Further, these authors point out that in certain clinical situations, such as a chronic subdural hematoma, this procedure may be the only treatment necessary. Lumbar Puncture It is our opinion that lumbar puncture should not be performed routinely in patients with acute head injury because of the potential risks to the patient and the limited diagnostic value of the procedure. While the presence of blood in the CSF probably indicates that a cerebral contusion and/or a laceration has occurred (29), there is no clear correlation between the presence or degree of subarachnoid hemorrhage and the severity or prognosis of the head injury. The pressure recorded from the lumbar subarachnoid space often does not accurately reflect the actual level of ICP (32) and in patients with elevated ICP, particularly when there is a predominately unilateral supratentorial mass lesion and an associated transtentorial hernia-

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tion, there is the possibility that lumbar puncture may precipitate an abrupt clinical deterioration (13). PATHOPHYSIOLOGY OF CRANIOCEREBRAL TRAUMA

Depending on the severity of injury and other factors, craniocerebral trauma produces several primary and secondary changes in the brain. It is important that the physician who intends to monitor and treat these patients acquires a basic understanding of the important pathophysiological changes occurring in moderate and severe degrees of craniocerebral trauma. In this section some of the more important alterations in certain physiological parameters will be considered. Intracranial Pressure and Cerebral Hemodynamics In 1901 Cushing (12) reported the results of his experiments showing the effects of increased ICP. He demonstrated that an acute elevation of ICP caused a compensatory increase in arterial pressure whenever the level of ICP was raised above diastolic blood pressure. This response, which is initiated by neural ischemia, has been termed the Cushing response or reflex. Since the studies made by Cushing, numerous clinical investigations have demonstrated that elevated levels of ICP can occur without causing clinically significant effects on pulse, respiration, systemic blood pressure, or level of consciousness (7). For instance, in one well controlled clinical study in 13 unanesthetized subjects, CSF pressure was raised to an average level of 920 mm. H 20 without causing significant change in the vital signs or other clinical parameters (19). Thus, the inability of the usual clinical variables such as vital signs or level of consciousness to indicate elevated ICP emphasizes the importance of continuously monitoring this parameter in head injury patients. An extensive number of clinical and animal studies have been made to determine the effects of head injury upon cerebral blood flow (CBF), cerebral metabolism, and cerebral autoregulation. In general, the more severe the degree of brain injury, the more impairment one finds in cerebral hemodynamics. However, there are many exceptions. To date, there does not exist a consistent correlation between severity and prognosis of head injury in a given case and quantitative data for CBF, cerebral metabolism, and cerebral autoregulation. Bruce and associates have investigated these physiological parameters in a series of comatose patients, the majority of whom had head injuries (8). These investigators determined CBF, ICP, cerebral perfusion pressure, cerebral autoregulation, and cerebral metabolism (as indicated by the cerebral metabolic rate for oxygen, CMR0 2) in 22 patients. They were

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unable to show that any of these variables could be used routinely to predict either the progression of a neurological lesion or survival of the patient. For example, in these patients, there was a 54 per cent mortality rate in those patients whose ICP was less than 30 mm. Hg, and a 44 per cent rate in those whose ICP was greater than 30 mm. Hg. Further, in some patients who had impaired cerebral autoregulation there was a good recovery, whereas others with intact autoregulation were moribund. Values for CBF also varied greatly, and in only 25 per cent of patients with a known unilateral mass lesion was the regional CBF (rCBF) reduced in the area of the lesion. On the basis of these findings, it is our belief that monitoring of CBF, cerebral metabolism, and evaluation of the status of cerebral autoregulation should probably remain investigational procedures until further information and experience are available. An important pathological contribution was made by Graham and Adams (18) who demonstrated ischemic brain damage in 55 per cent of their series of fatal head injuries. These patients showed focal lesions in the neocortex, basal ganglia, hippocampus, or cerebellum, usually in areas of arterial boundary zones, the so-called "watershed areas," thus leading these authors to conclude that a decreased cerebral perfusion pressure may be the etiology of these lesions. Respiratory System

Respiratory alterations are common in comatose patients with severe head injury. Hyperventilation associated with respiratory alkalosis is a frequent respiratory abnormality and was observed by Huang and associates (21) in 52 of 68 patients with severe head injury. As would be expected, arterial blood CO 2 values were usually below normal range. Several investigators have demonstrated a correlation between ICP w aves and respiratory waves in head injury patients (31, 4], 57). In one clinical study it was found that a transient increase in expired CO 2 preceded the ICP wave in 77 per cent of the ICP waves analyzed (57). The increase in the expired CO2 begins approximately 9.0 seconds before the ICP wave and usually follows an irregular respiratory pattern. During the ICP wave, there is usually a decrease in respiratory rate and depth. These respiratory changes have been discussed in detail elsewhere (37). Moody and Mullan (41) concluded from their studies that alteration in the respiratory pattern is one of the earliest clues to deterioration in the head injury patient's condition. Further, they believe that early changes in respiration are too subtle to be detected by either continuous or intermittent bedside observations, thus providing further rationale for continuous monitoring by instrumentation.

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Fluid and Electrolyte Abnormalities Following craniocerebral trauma there is usually retention of sodium lasting t\VO to three days. Serum sodium determinations do not always reflect this retention, but urinary sodium quantitation will reveal a decreased excretion of this electrolyte (9, 45). In general, sodium retention is more pronounced in severely injured patients. Following the period of sodium retention, a mild natriuresis phase of four to seven days' duration occurs (38, 4Ei). Several patterns of persisting and clinically significant sodium imbalance have been described (38). The syndrome of inappropriate secretion of antidiuretic hormone which is frequently seen in head injury patients may cause additional neurological deficits from the retention of water and associated hyponatremia (5, 9). The usual findings in this syndrome are serum hyponatremia (less than 135 mEq. per liter) and serum hypotonicity (less than 280 mOsm. per liter) with a concomitantly elevated urine sodium (25 mEq. per liter or more) and a urine osmolality greater than serum osmolality. Neurological deficit is caused both by intracellular hyponatremia and by additional cerebral edema from the excessive water load. Water intoxication from overhydration may be seen in head injured patients in coma who have been subjected to the excessive administration of intravenous fluids. Characteristic findings are a serum sodium of less than 130 mEq. per liter and serum osmolality of less than 280 mOsm. per liter (39). Although hypernatremia occurs less frequently than hyponatremia, it is not infrequent and has been reported in five to 10 per cent of head injured patients (45). Most commonly this is a dehydrational type of hypernatremia caused by several factors including inadequate fluid intake in comatose patients, diabetes insipidus, excessive renal water loss, or excessive extrarenal losses through skin, lungs, or gastrointestinal tract.

Hematological Abnormalities Disseminated intravascular coagulopathy (DIC) is a dramatic, but fortunately, rare complication that may occur in association with craniocerebral trauma. DIC is an acquired state in which the conversion of fibrinogen to fibrin is accelerated. During the process of fibrin formation multiple plasma coagulation factors are depleted. The factors most often affected are Factor VIII (AHF) , Factor V, Factor II (prothrombin), and blood platelets in addition to fibrinogen (16). When consumption of the procoagulants exceeds their production, platelets and other coagulation factors may be significantly reduced to below hemostatic levels and consequently, excessive bleeding may occur.

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Goodnight and co-workers (16) studied a group of 13 patients who had cerebral tissue destruction as a result of head injury. Kine patients bled extensively and three others showed laboratory evidence of DIC. All of their patients had considerable destruction and necrosis of cerebral tissue, 10 of which were caused by gunshot wounds of the head. Endocrinological Abnormalities Rarely, diabetes insipidus, usually in a transitory form, may occur following head injury. In a series of 3000 cases of head injury, Clark (9) reported only eight cases of diabetes insipidus, all presumably the result of pituitary damage at the time of injury (9). Kornblum and Fisher (30) observed one or more lesions in the pituitary gland in 62 of 100 patients with craniocerebral trauma. Specifically, capsular hemorrhage was seen in 59 cases, hypophyseal stalk hemorrhage in six, laceration of the stalk in one, posterior lobe lesions in 42, and ischemic necrosis of the anterior lobe in 22 cases. The 42 lesions involving the posterior lobe included hemorrhage, necrosis, gliosis, and fibrosis. Only t\VO patients in this latter group developed clinical diabetes insipidus, and both cases had massive pituitary necrosis involving both lobes. In view of the frequency of these pathological findings in the pituitary in severe head injury, it is surprising that endocrine disturbances and/or diabetes insipidus are not encountered more frequently. "Neurogenic" hypernatremia has been produced by specific lesions in the paraoptic (34) and ventromedian (55) nuclei of the hypothalamus. Clinically, this syndrome is characterized by insidiously developing hypernatremia in a patient who has sustained a frontal lobe or rostral brain stem injury. Welt and associates (63) and Engstrom and Liebman (14) have questioned the existence of this particular clinical entity and have suggested that the occurrence of severe water deficit and hypernatremia in the stuporous or comatose patient may be caused by impaired ability to experience or express the sensation of thirst. MONITORING OF HEAD INJURY PATIENTS

The modern era of neurosurgical patient monitoring was begun by Ryder and colleagues in 1952 (50). They reported for the first time the use of indwelling ventricular and subarachnoid catheters connected to external transducers for continuous measurement of ICP. Similar techniques were soon used by other investigators including Lundberg (36) who published a classic monograph on ICP monitoring in 1960. Cooper and Hulme (11) also made an important contribution by emphasizing the importance of "plateau waves," including their correlation with intracranial mass lesions. Thus, the excellent work of these and many other investigators has established the value of continuous patient monitoring. It remains for present

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workers to establish practical and reliable methodology and to further investigate the clinical and pathophysiological aspects of elevated ICP in head injury.

Criteria for Monitoring-Patient Selection Criteria for patient selection are one of the first considerations in monitoring. Patients who have experienced a cerebral concussion * with or without a nondepressed skull fracture, who are either alert or only slightly drowsy and show no abnormal neurological signs at the time of the initial examination are hospitalized for 24 to 48 hours and then discharged provided there are no complications or adverse changes in their condition. In these patients. periodic evaluation of neurological status, level of consciousness, and vital signs constitutes adequate monitoring. In patients with more serious injury, ICP and other special parameters should be continuously monitored in addition to those mentioned above. Specifically, the following patients should have monitoring: 1. Patients with gunshot wound of the brain. 2. Patients who have had a subdural, epidural, or intracerebral hematoma evacuated or a depressed fracture elevated and who have associated cerebral contusion] or edema as determined at surgery and/or who have a depressed level of consciousness postoperatively (Grade 2 or greater). 3. Patients with closed head injury (cerebral contusion) who are Grade 2 or greater in regard to level of consciousness and in whom cerebral angiography is normal. Parameters to be monitored in the above categories of head injury patients include the following: 1. Neurological status. 2. Level of stupor and coma. 3. Intracranial pressure. 4. Endotracheal CO2 level. 5. Electrocardiogram. 6. Blood pressure. 7. Heart rate. 8. Respiratory rate and depth. 9. Temperature. 10. Arterial blood gases (pC0 2, p02) and pH.

* Concussion-A clinical syndrome characterized by immediate and transient impairment of neural function, such as alteration of consciousness, disturbance of vision, equilibrium, etc., due to mechanical forces (1). t Contusion-A structural alteration of the brain usually involving the surface, characterized by extravasation of blood cells and death of tissue, with or without edema. Clinical manifestations of the contusion depend on the area and extent of the injured tissue (1).

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11. 12. 13. 14. 15. 16.

Serum electrolytes. Serum osmolality. Urine electrolytes. Urine osmolality. Fluid intake and output. Hematological studies-fibrinogen level, platelet count, protamine paracoagulation test, prothrombin time, Factor V level, and Factor VIII level. 17. Other-complete blood count (CBC), urinalysis, blood urea nitrogen (BUN). Rationale and Methodology for Monitorinq

The rationale for and the specific details of monitoring some of these parameters follows: INTRACRANIAL PRESSURE

The value of continuous ICP recording in the clinical management of patients with head injury is well established (10, 36, 50). Continuous ICP measurement in head injury patients serves not only to indicate the need to institute therapy to reduce elevated ICP but also monitors the effectiveness of therapy. Many well controlled investigations have shown that clinical signs, particularly vital signs, are unreliable in indicating the rise in I CP that often follows severe head injury (7, 19). Consequently, a method of directly monitoring ICP has obvious advantages as clinical management can be more securely based if ICP is directly and continuously measured. ICP monitoring can also provide some indication of the location of the lesion in severe craniocerebral trauma. For instance, in a head injury patient who is comatose and decerebrate and who has a normal ICP, it is likely that the lesion is a primary brain stem injury. It is important that ICP recordings be made directly from the intracranial cavity as estimates of ICP based on pressure recordings in the lumbar subarachnoid space are unreliable and often dangerous (32). Although a wide variety of techniques and devices are available for monitoring ICP, the following discussion will be limited to those methods which can be applied in a routine neurosurgical practice. 1. Intraventricular catheters. Several investigators including Lundberg (36), Langfitt and co-workers (31), and Ryder and associates (50) have successfully used intraventricular catheters connected to an external strain gauge to measure ICP. In this method, a twist drill opening is made in the skull and a catheter (e.g., a No.5 pediatric feeding tube, a Scott cannula, etc.) is carefully inserted into the lateral ventricle. Kaufmann and Clark (25) have described

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an ingenious technique with the skull opening in the forehead 5 cm. above the nasion and 3 cm. to the right of the midline. After satisfactory placement of the catheter within the ventricle, appropriate connections are made to an external transducer and amplifier-recording system. The advantages of the intraventricular technique are that the technique is relatively easy and safe; the recording equipment and catheters usually are available in most hospitals; reliable values for ICP can be obtained; and elevated ICP can be acutely reduced by allowing CSF to escape through the catheter. The disadvantages include occasional blocking of the catheter and potential infection. As the incidence of infection increases with the length of time the catheter remains in the ventricle, it should not remain in place longer than three to five days except under unusual circumstances. 2. Subarachnoid screw. Vries and co-workers (60) have reported the successful use of this method for continuously measuring ICP in 56 patients, the majority of whom had head injury. The length of recording averaged seven days and no infection occurred in this series. The technique for insertion of the subarachnoid screw is relatively simple. A p,~ -in. twist drill hole is made in the skull (coronal) through a l-cm. scalp incision using local anesthesia. The exposed dura mater is opened and a hollow screw is threaded into the drill opening to a point that places the tip 1 mm. below the surface of the dura mater. The skin incision is closed and a dressing placed around the shaft of the screw. In order to monitor ICP, appropriate connections with plastic tubing are made between the subarachnoid screw and an external transducer. The principal advantages of the method include its relative simplicity, accuracy in recording ICP, and the fact that it is not necessary to place the device into a ventricle. Occasionally, the pressure tracings dampen out and it is necessary to flush a small quantity of sterile saline through the system into the subarachnoid space. Thus, there is the potential for infection with this technique. 3. Rickham reservoir with attached intraventricular cannula. Currently, we are using a method consisting of a closed Rickham reservoir (The Holter Co., King of Prussia, Pa.) seated in a burr hole and attached to an intraventricular catheter for continuous monitoring of ICP (Figs. 19.1, A-C, and 19.2, A, B). The principal advantage of this technique over other methods is that a reliable IC.P tracing can usually be obtained and the technique allows one to frequently change the external catheter connectors, thus significantly reducing the potential of introducing infection. One disadvantage of the method is that insertion of the reservoir requires a minor surgical procedure. Using local anesthesia, a small curved incision is placed over the right frontal region and a ~'8-in. trephine opening is made immediately anterior

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A.

c. Rickham Reservoir and Scalp Vein Needle

-- Lat. Ventricle

FIG. 19.1. A, location of burr hole, anterior to coronal suture and 2 em. from midline, for insertion of ventricular catheter. B, closed Rickham reservoir with attached Holter ventricular catheter in frontal horn of lateral ventricle. C, intracranial pressure (ICP) monitoring device in place with external connections to transducer.

to the coronal suture and 2 cm. from the midline. The dura mater is opened and a Holter ventricular catheter (The Holter Co., King of Prussia, Pa.) is inserted into the frontal horn of the right lateral ventricle. After proper placement, the catheter is connected to a closed Rickham reservoir which is seated in the burr opening and the skin incision is closed. Following wound closure, a 23-gauge needle with soft catheter attached (Abbott butterfly, Abbott Laboratories, North Chicago, Ill.) is inserted percutaneously into

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FIG. 19.2. A, lateral, and B, anteroposterior plain skull x-rays showing lOP monitoring device in place.

the Rickham reservoir, taped to the scalp, and connected to a pressure transducer (Model 1280C-02 ,Hewlett Packard Medical Electronics Division, Waltham, Mass.) for pressure recording. Every twelve hours thereafter, the 23-gauge needle butterfly and external tubing are replaced because we believe that the frequent replacement of a fresh, sterile external needle and catheter reduces the potential of infection. Wyler and Kelly (66) have shown that patients with ventriculostomies who are prophylactically treated with antibiotics have a significantly lower incidence of infection and we now routinely place our patients on ampicillin 500 mg. every six hours while the monitoring device is in place. We have now used this method in 30 head injured patients. Reliable ICP recordings have been obtained in 27 of these patients and in no case has a ventriculitis, meningitis, or wound infection occurred. Following completion of monitoring, the patient is taken to the operating room, and using local anesthesia, the small wound is opened and the Rickham reservoir with attached ventricular catheter is removed. 4. Other devices for monitoring [CPo These include the Numoto switch (44), solid state transducers, and the passive resonance radio transmitter (4). These devices are inserted into the epidural or subdural space. The

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passive resonance circuit is fragile, requires compensation for changes in body temperature and barometric pressure, and after long term use has a tendency to leak. For these reasons, passive resonance circuit transducers are not generally applicable to clinical use. One outstanding advantage of the ventricular catheter and the Rickham reservoir method over the subarachnoid screw or solid state transducer is that elevated ICP may be abruptly reduced to normal values by aspirating ventricular fluid. The following is a case summary of a patient with craniocerebral trauma that illustrates the potential value of continuous ICP recording. Case 1. A 26-year-old man sustained craniocerebral trauma during an assault and was admitted to Grady Memorial Hospital. At the time of admission, examination showed a mild contusion above the right ear and blood in the right external auditory meatus. His level of consciousness was Grade 2 (see Table 19.1). He had no focal neurological deficits. Blood pressure was 160/70 and heart rate 80 and regular. He was admitted to the Neurosurgical Intensive Care Unit for observation. Approximately seven hours after admission he had a right focal seizure which became generalized and following the seizure he was noted to be less responsive. His left pupil measured 6 mm. in diameter and the right, 4 mm. Both pupils were equally reactive to light. He also was noted to have weakness of the right side of the face. Bilateral carotid angiography was performed and was interpreted as normal (Fig. 19.3, A, B).

FIG. 19.3. A, anteroposterior, and B, lateral carotid angiograms in a patient with Grade 2 stupor following a closed head injury. These were interpreted as being within normal limits.

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r FIG. 19.4. A and B. Repeat carotid angiograms in the same patient as in Figure 19.3, six days after admission showing elevation of the left middle cerebral artery branches suggestive of a left temporal lobe mass lesion. A pediatric feeding tube inserted through a right frontal twist drill ventriculostomy is shown in the right lateral ventricle.

Over the next five days the patient's mental status did not significantly change. He remained in Grade 2 stupor, easily arousable but confused and disoriented. He responded appropriately to tactile stimulation. His left pupil remained slightly larger than the right one. At 3 a.m. on the sixth hospital day he was noted to be completely unresponsive to severe painful stimulation and both pupils were approximately 5 mm. in diameter and nonreactive to light. An emergency right frontal twist drill ventriculostomy was made and a No.5 pediatric feeding tube was inserted into the right lateral ventricle. The opening pressure was 450 mm. H 20 . Approximately 5 ml. of ventricular fluid were withdrawn with slight improvement in his clinical status. He then underwent repeat bilateral carotid angiography. There was a 19-mm. left to right shift of the internal cerebral vein with an associated left to right shift of the anterior cerebral arteries. No extra-axial mass was identified. The left middle cerebral artery branches were elevated, suggesting a left temporal lobe mass lesion (Fig. 19.4, A, B). The patient was taken immediately to the operating room and a left temporal craniectomy carried out with evacuation of a 50-rol. intratemporal hematoma. Additionally, a left temporal lobectomy was performed. Postoperatively, he had a right hemiparesis with greater involvement in the arm. However, he responded appropriately and was oriented to person and place. Over the next three weeks his mental status fluctuated between a Grade 1 and a Grade 2 stupor and his right hemiparesis

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gradually improved. When seen in follow-up clinic two and one-half months after his admission he was alert and oriented. Neurological exam was normal except for a slight right facial weakness.

Comment: The apparent development of a temporal lobe mass between the time of the first and second angiograms may have been due to the delayed occurrence of an intracerebral hemorrhage or to the development of marked cerebral edema around the lesion which was not large enough to reflect itself on the original angiogram. The latter explanation appeared more likely preoperatively. It is believed that continuous monitoring, particularly of ICP and respiratory status, in this case carried out from the time of admission, would have shown definite alterations in these parameters well in advance of the abrupt change in his level of consciousness and neurological status. RESPIRATORY SYSTEM

Routine clinical monitoring of the rate, depth, and adequacy of respiration can be accomplished by measuring the following parameters: 1. Per cent endotracheal CO2 • The continuous analysis of CO 2 can be accomplished with a small endotracheal catheter connecting the patient's airway to an infrared CO 2 analyzer. In the absence of an alveolar-capillary perfusion block, the end expiratory CO 2 approximates the level of arterial pC02. Thus, this relatively simple technique provides a constant check on the adequacy of the respiratory exchange. Infrared CO 2 analyzer-recorders are commercially available and are relatively simple to use and to maintain. 2. Impedance pneumotachometer. The rate and pattern of respiration is monitored by recording left arm/right arm impedance changes across the chest through a standard Lead 3 electrocardiogram (EKG) patient cable and utilizing currently available respiration modules. This method enables one to follow changes in respiration which often cannot be appreciated by visual monitoring of chest wall movement. S. Arterial blood gas deterrnination. Periodic measurements of arterial pC02, P02, and pH are valuable in that they provide the most accurate measure of the adequacy of ventilation. The effectiveness of elevated carbon dioxide levels in elevating ICP and CBF is well known. Langfitt and coworkers (31) have shown that intracranial pressure waves can be initiated by hypercapnia, and Paul and associates (46) have shown that spontaneous pressure waves are not usually generated when arterial pC02 is kept below 30 mm. Hg. Hypoxia is also a potential cause for cerebral vasodilatation. However, Revere hypoxia with p02 in the range of 30 to 40 mm. Hg is necessary for there to be significant cerebral vasodilatation on the basis of hypoxia alone (49).

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BLOOD PRESSURE

This important parameter can be monitored as follows: 1. Catheter technique. In this method, a catheter is inserted into either a

radial or brachial artery and connected to a pressure transducer. This method is accurate and allows for continuous registration of arterial blood pressure. Its principal disadvantages are that it is an uncomfortable, invasive technique, and it can only be used for relatively short periods of time. In special situations, such as monitoring the patient during either surgery or periods "Then special studies (e.g., cerebral blood flow determinations) are being obtained, the catheter technique is the method of choice for continuous measurement of arterial pressure. 2. Sphygmomanometer, manual. In the majority of situations, the tim.e tested method of obtaining blood pressure with a sphygmomanometer and auscultatory techniques is used for obtaining blood pressure. This method has the advantages of noninvasiveness and availability but provides only intermittent rather than continuous measurement of blood pressure. 3. Sphygmomanometer, automatic. Commercial devices are available that will inflate the arm cuff at regular intervals, perceive the Korotkov sounds using a special sensor, and automatically either display a digital readout or register on a recording system or both. These devices relieve the nursing staff of the responsibility for obtaining this parameter and also provide for more frequent and regular measurements of blood pressure. However, technical problems often occur with these devices and the individual blood pressure monitors and recorders are expensive. HEART RATE, EKG, AND TEMPERATURE

These parameters can be monitored easily from surface electrodes attached to the skin and require no special comment. OTHER FEATURES

Ideally, the monitoring system should have certain features such as instant digital readout and a display oscilloscope so that changes in vital signs can be easily observed and followed by the nursing staff. Also, a pen or thermal recorder should be part of the system so that a permanent record of the various parameters can be obtained. CLINICAL LABORATORY STUDIES

Certain clinical laboratory studies are important in the management of patients with head injuries, and in specific instances may provide a valuable guide for therapy. These investigations include: 1. Serum and urine electrolytes and osmolalities. The determination of

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serum N a, Cl, K, and CO 2 and serum and urine osmolalities and BUN should be performed frequently, often daily, along with hourly measurement of intake and output during the acute phase of recovery from head trauma, It is common to find marked abnormalities indicating the need for abrupt revision of fluid and electrolyte therapy (9). In the evaluation of intracellular water deficits which may not produce clinically obvious dehydration, frequent urinary Na, Cl, and K levels will provide a guide for replacement of these ions (17). 2. Hematological studies. Monitoring for hematological abnormalities should include admission studies of hemostatic function including fibrinogen level, platelet count, protamine paracoagulation test, prothrombin time, and Factor V and Factor VIII levels. When instances of obvious bleeding disorders occur or when laboratory studies indicate a reduction of one or more coagulation factors, daily monitoring of these coagulation factors is probably indicated, at least until normal laboratory values are reestablished. 3. Nitrogen balance. On occasion, a patient with a severe head injury may have a sharply negative nitrogen balance indicating massive loss of body protein. Azotemia, reversal of the albumin-globulin ratio, and weight loss are the clinical indicators of this state. Caloric intake must exceed 1000 calories per day and include the essential amino acids to provide maximal sparing of body protein (65). 4. Endocrine studies. Plasma cortisol levels are usually markedly elevated in head injured patients, just as they are in patients w ith traumatic, surgical, or physical stress (28). In an occasional patient, hypothalamic centers for steroid release or the pituitary gland itself may be inactivated by direct or indirect trauma, thus eliminating the normal steroid stress response. Glucose catabolism is inhibited by elevated steroid levels (27); this is manifested by elevated blood glucose and decreased plasma insulin levels in patients during the first five days following head injury. As in any type of stress, diabetes mellitus may be unmasked in the head injured patient, but this is rarely a major clinical problem. SPECIAL STUDIES AND INVESTIGATIVE PROCEDURES IN HEAD INJURED PATIENTS

Certain parameters which have been investigated in head injured patients and which may ultimately prove to have considerable value in the clinical management of these patients include cerebral blood flow and cerebral metabolism determinations and evaluation of the status of cerebral autoregulation. Presently, these parameters are investigational measures and are not applicable for routine clinical monitoring in head injury patients.

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EVALUATION AND :l\IONITORING OF INFANTS AND CHILDREN 'VITH HEAD INJURY

Because of the special problems occasionally presented by infants and children with head injury (e.g., management of chronic subdural hematoma) and the fact that craniocerebral trauma is common in the pediatric age group, it is believed appropriate to devote a separate section of this chapter to the diagnostic evaluation and monitoring of infants and children.

Criteria for Admission to Hospital The indications for admission of infants and children wit.h head injury to the hospital are similar w ith few exceptions to the criteria applied to adults and include: 1. Head injury that produces loss of consciousness, regardless of duration. 2. Head injury that produces persistent vomiting, persistent headache, and/or retrograde amnesia. 3. Presence of skull fracture-linear or depressed; simple or compound. 4. Suspected "battered child" syndrome. Whenever there is doubt as to whether the child can be cared for and observed at home or should be admitted to the hospital, the child should be observed in the hospital. This decision should not be influenced by the level of intelligence or degree of cooperation of the parents. The duration of hospital stay should be individualized and is determined by the severity of injury. The importance of an exact history of the injury along with a thorough neurological examination has been emphasized in the section dealing with adult head injuries and applies as "Tell to children. The classification of stupor and coma (Table 19.1) is equally applicable to the pediatric age group and provides a quantitative guide to establishing a neurological base line and evaluating response to therapy.

Diagnostic Evaluation X-RAYS

As in adults, all infants and children with craniocerebral trauma should have x-rays which routinely include anteroposterior, lateral, and anteroposterior half-axial -(Towne) projections of the skull and a lateral projection of the cervical spine. CEREBRAL ANGIOGRAPHY

Cerebral angiography is the definitive diagnostic procedure in both infants and childrenwith craniocerebral trauma. However, this procedure is

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not indicated in every infant or child who is obtunded and has a focal neurological deficit. Frequently, the level of consciousness and focal deficit will begin to clear over a 12- to 24-hour period of observation. If the patient either deteriorates or fails to improve during this period of time, then angiography is indicated. The procedure will establish whether or not a focal intracranial lesion exists as well as showing its location, thus allowing the neurosurgeon to plan a definitive surgical approach. Technical refinements in angiographic procedures, particularly the perfection of the transfemoral catheter method, are currently such that cerebral angiography can be carried out in any infant or child, regardless of age. SUBDURAL TAP

Although the subdural tap has teen used frequently in evaluating infants with craniocerebral trauma, we believe that this diagnostic procedure is not indicated in acute head injury because of the limited diagnostic value and the potential hazards of the procedure. * Cortical vessels and cerebral tissue may be lacerated by the needle tip. The needle may fail to enter a subdural accumulation of blood which may be located at a site away from the anterior fontanelle and thus give the physician an erroneous impression as to diagnosis. Further, even when the needle enters the hematoma, clotted blood usually will not flow through the needle. ICP

:M~ONITORING

TECHNIQUE IN INFANTS AND CHILDREN

ICP monitoring is indicated in infants and children who show no angiographic evidence of a focal mass lesion and who fail to improve over the initial 12- to 24-hour period. In infants and children with open anterior fontanelles or patent coronal sutures, the scalp is prepped and draped in the usual manner 'with the patient in the supine position and the head brow up. A special 4-in., 20-gauge polypropylene ventricular cannula (Cordis Corp., Miami, Fla.) is passed percutaneously through the anterior fontanelle or the coronal suture and the underlying dura mater with the trocar stylet. The trocar stylet is then replaced by a blunt stylet and the cannula passed into the anterior horn of the lateral ventricle. The LUERLOK (Becton, Dickinson and Co., Rutherford, N. J.) connector of the cannula is then attached to the external pressure transducer. The forehead approach is used in older children with closed sutures. The advantage to this approach is that the scalp does not need to be shaved and a small ventricle is more easily tapped along its axis. The forehead is

* While contraindicated in the diagnostic evaluation of acute craniocerebral trauma, the subdural tap is an excellent therapeutic procedure in chronic subdural hematoma of infancy (see below). Indeed, when these cases are associated with markedly increased ICP, a subdural tap provides an immediate decompression and can be lifesaving.

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prepped with povidone-iodine (Betadine, The Purdue Frederick Company, Yonkers, N. Y.) and is draped. A transverse stab "round is made 2.5 em. lateral to the midline and 2 cm. above the orbital ridge. A twist drill hole is made and the 20-gauge polypropylene cannula is passed through the dura using the trocar stylet. This stylet is then replaced with the blunt stylet and the cannula is passed in a posteromedial direction to enter the anterior horn. The LUER-LOK end of the cannula is then connected to the external pressure transducer. AP and lateral skull x-rays are obtained for confirmation of cannula placement. If the ICP remains normal over a 24-hour period, the intraventricular cannula is removed. If the ICP is persistently elevated (>30 mm. Hg) the patient is treated as described below. In this case the catheter is allowed to remain in place for no longer than five days because of the possibility of infection. If the ICP remains elevated at the end of this time, a closed Rickham reservoir with attached Holter ventricular catheter is seated in the burr hole as described above and the ICP is measured as long as indicated. Prophylactic antibiotics are used in the pediatric cases in a manner similar to that for ventricular shunt procedures. Value of Pressure Measurement in Management of Chronic Subdural Hematoma of Infants and Children

A frequent and troublesome problem is the management of chronic subdural hematoma in infants and children. In these cases, we have used intermittent measurement of pressure in the subdural hematoma itself as an important guide in management. In infants and children in whom either the anterior fontanelle or the coronal sutures are open, an initial percutaneous subdural tap (23-gauge butterfly needle) is performed and the opening pressure in the hematoma measured. The reduction of pressure and not the fluid volume determines the quantity of subdural hematoma fluid to remove. It is our opinion that the subdural pressure should be reduced no lower than half the initial opening pressure. Bilateral taps are not performed at the same sitting. The opposite side is tapped on the following day and if subsequent taps are necessary, the two sides are alternated. Whenever the opening pressure in the subdural hematoma is 100 rom. H 20 or less «8 rom. Hg) we believe that it is unnecessary to continue tapping. Following each procedure, the level of consciousness, anterior fontanelle tension, and clinical signs (e.g., irritability, vomiting, etc.) are carefully monitored. If the clinical situation improves, the anterior fontanelle remains flat, and there is no abnormal progression of head circumference, then no further subdural taps are performed. The head circumference and neurological development are closely followed for at least six months.

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When the clinical situation is not improved by this method of management over a reasonable period of time (seven to 10 days), then a repeat cerebral angiogram is performed to determine the depth of the subdural hematoma and the size of the ventricles. Occasionally, particularly in refractory cases, it may be necessary to shunt the subdural fluid into the peritoneal cavity. Chronic subdural hematomas in children with closed cranial sutures are treated like those in adults, with burr hole or twist drill drainage. l\IEDICAL TREATlVIENT OF PATIENTS WITH HEAD INJURY

A comprehensive section on therapy of head injury is beyond the scope of this chapter. Nevertheless, it is appropriate to briefly cite our method for treating sustained ICP elevations (> 30 mm. Hg) in adult and pediatric patients with craniocerebral trauma in whom a surgical lesion has been excluded or treated by appropriate surgical therapy. Even though low or normal pressures may carry a poor prognosis w hen they are caused by focal lesions in critical areas such as the brain stem, for all practical purposes, the medical management of head injury is essentially the control of increased ICP when it occurs. It should be emphasized that such control is considerably facilitated by continuous monitoring of ICP. Although it is sometimes difficult to know exactly "Then specific therapeutic modalities should be used to lower increased ICP, we have arbitrarily decided that a sustained mean ICP of 30 nun. Hg or more indicates the level at which specific treatment should begin. This is supported by an autopsy study conducted by Adams and Graham (2) who have shown in a small series of 35 patients who had increased ICP during life that focal necrosis of the parahippocampal gyrus occurred in 100 per cent of patients whose ICP was greater than 40 mm. Hg, whereas no instance of necrosis occurred in those patients whose ICP did not exceed 20 mm. Hg. When ICP remains above 30 nun. Hg, our treatment regimen includes: 1. Hyperventilation is employed either by assisted or controlled ventilation, to lower pAC02 to the 25 to 30 mm. Hg range, utilizing frequent arterial blood gases to monitor the pAC0 2 • 2. We use a hypertonic 20 percent solution of mannitol in distilled water (McGaw Laboratories, Evanston, Ill.) which is administered intravenously in a dosage of 1 to 2 gm. per kg. over a 30- to 60-minute period. When administered in this way there follows a prompt diuresis and usually a fall in ICP to normal values, with a gradual return of ICP to pretreatment levels over the next five and one-half to eight hours (64). Those patients who fail to respond to this treatment are usually not benefited by repeated courses of mannitol. Patients who receive mannitol should be monitored with twice daily serum and urine osmolalities to prevent excessive extracelhilar dehydration and acidosis.

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3. Glucosteroids are used empirically in patients with moderate to severe head injury. Although steroids decrease cerebral edema associated with brain tumors (15), their effectiveness in head injury has not been conclusively proven. We are currently using dexamethasone in a dosage of 10 mg. intravenously on admission followed by 4 mg. intramuscularly every six hours in both adult and pediatric patients for five days postinjury, followed by a tapering dose over the next two days. 4. Removal of small amounts of ventricular fluid often may significantly 10V\'er the ICP. Access to the ventricular system is one of the major advantages of measuring ICP by an indwelling ventricular cannula as described earlier. ROLE OF COMPUTERS IN l\JI0NITORING

The continuous monitoring of numerous physiological parameters in several patients over a period of many days leads to the accumulation of large volumes of data. Thus, there is a need for a system to perform meaningful and accurate on-line data acquisition, retrieval, and analysis. The technology for accomplishing this task with computers is available (62) and the remainder of this publication will be concerned with the establishment of a computerized intensive care unit that can readily accommodate head injured and other seriously ill neurosurgical patients. To illustrate the possibility of designing systems for neurosurgical monitoring, a prototype design for a computerized intensive care monitoring system which is completely free of additional requirements for computer facilities will be described. Since the actual physical layout of the proposed system is of minor importance, we have illustrated (Fig. 19.5) how this system could be implemented in one of the existing neurosurgical wards in Grady Memorial Hospital in Atlanta, Georgia. Presently, continuous monitoring on this ward is done with standard commercially available systems without the aid of computers. The three areas of primary interest in the proposed system include the general neurosurgical 'Yard, intensive care unit, and research facility. It is intended that the individual patient rooms on the ward will be connected to the system only through special purpose terminals. These are small, inexpensive keyboards for entering pertinent clinical information, such as periodic measurements of vital signs. Larger textual entries such as progress reports can be entered at larger, more efficient terminals located at the nurses' station or in the physicians' office adjacent to the ward. At the central station in the intensive care unit there is a monitoring console which selectively displays parameters from individual beds. Each patient bed has the basic physiological monitoring controlled by a microprocessor, which in turn interfaces with other components of the system. The research room is set aside for special investigations such as regional

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Nurses Station

D Research and Treatment

D

T

~ Terminal

Deed

FIG. 19.5. Schematic of neurosurgical ward at Grady Memorial Hospital, Atlanta Georgia, showing design of proposed computer-assisted monitoring unit.

cerebral blood flow (rCBF) determinations and for special procedures such as twist drill ventriculostomies. This area will house most of the electronic computer equipment. Methods for Data Analysis

The patient's clinical status and the severity of craniocerebral trauma determine the extensiveness and complexity of monitoring required. An efficient monitoring system must be flexible enough to monitor patients on an individualized basis. However, when several parameters are continuously monitored, the large amount of data generated makes the interpretation of changes in the parameters an increasingly difficult task for the physician (54). STATISTICAL ANALYSIS

Some investigators have proposed that statistical analysis methods be used for preliminary data screening and analysis (3). Several possible methods exist, and they all have in common the ability to compress the mass of minute to minute data and present it to the physician in a more comprehensible form. TREND ANALYSIS

A representative method of achieving a degree of predictive capability for the monitored parameters is trend analysis (20). This method is based on the analysis of successive discrete measurements of physiological par-

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ameters and determines the probability that an observed value is significantly different from a predicted value. The assumption is first made that a one period ahead prediction of the value of a given parameter can be made by using an exponentially weighted average of past measurements. The difference between the actual measurement and the predicted value is then subjected to a test of statistical significance to determine the probability that such a difference could occur by chance alone. If the probability is very low ( < 1 per cent), the clinician may assume that the difference is not due to a chance occurrence but rather to some change in the physiological system which requires further evaluation and treatment. The emphasis with this method is on the occurrence of statistically significant changes before normal limits have been exceeded. HISTOGRAMS

Another technique of immediate usefulness to head injury patient monitoring has been described by Janny and colleagues (22). They approach the analysis of data created by long term continuous monitoring of ICP by constructing pressure histograms. The histogram is a graphical display of the amount of time the ICP is at certain levels. This technique is not restricted to ICP measurements, of course, but could be applied to any parameter that is recorded at discrete intervals. 11([aintenance of Up to Date Patient Records

The presence of the patient record on a computer file allows the over-all data management system to monitor the acquisition of clinical information (6). For instance, one recurrent problem is the tendency for clinical laboratory values to get lost, misread, slowed down in transit, etc. Using an on-line system, many of these problems can be avoided. When a laboratory request is initiated, a notation is made in the computer that a test has been ordered. The system can then monitor the efficiency with which the results are returned; if too long a period passes with no results, attention is called to this fact. Further, when the results are received from the laboratory, the incoming data can be subjected to a variety of validity tests. Lindberg (35), for instance, has described a way in which a laboratory data transmission system can accomplish validity tests. A final advantage of having a large scale minicomputer available in a hospital monitoring and information system is the almost unlimited possibility of adding on special purpose projects. Procedures such as regional cerebral blood flow determinations already demand the use of a computer. SU1VIlVIARY

A practical protocol for evaluating and monitoring head injured patients has been presented. It has been stressed that monitoring is an ongoing

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process which begins with the initial evaluation and continues throughout the patient's hospital stay. The level of monitoring and thus the parameters to be monitored are determined on an individualized basis according to the patient's clinical status and his level of stupor and coma. It has been suggested that for mild head injuries, adequate monitoring includes periodic evaluation of the neurological status and vital signs; but the more severely injured patients require extensive and frequent monitoring of a large number of clinical and physiological parameters. Among the many parameters, the continuous monitoring of ICP and the respiratory system are perhaps the most useful indicators of the patient's condition. Several methods for continuous ICP monitoring which are readily adaptable to most neurosurgical practices have been discussed. These include the intraventricular catheter, subarachnoid screw, and the closed Rickham reservoir connected to a ventricular catheter. In our institution, the Rickham reservoir has been used to monitor ICP and at the time of this report, satisfactory ICP recordings have been obtained in 27 of 30 head injury patients. Although this method requires a small surgical procedure, we believe that the decreased incidence of infection, the rapid access to ventricular fluid, and its potential for long term monitoring justify its use. Suggestions for monitoring other physiological parameters have also been presented. Particular emphasis has been placed on the management of infants and children with head injuries. The clinical entity of chronic subdural hematoma in infants and children has been used to illustrate the value of lOP monitoring as a guide to further treatment. Finally, we have briefly discussed the place of computers in day to day patient care, research, and monitoring. REFERENCES 1. Ad Hoc Committee to Study Head Injury Nomenclature. A glossary of head injury including some definitions of injuries of the cervical spine. Clin. N eurosurg., 12: 388-394, 1966. 2. Adams, H., and Graham, D. I. The relationship between ventricular fluid pressure and the neuropathology of raised intracranial pressure. In Intracranial Pressure: Experimental and Clinical Aspects, edited by M. Brock, and H. Dietz, pp. 250-253. Springer-Verlag, Berlin, 1972. 3. Afifi, A. A., Rand, W. M., Palley, N. A., Shubin, H., and Weil, M. H. A method for evaluating changes in sets of computer monitored physiological variables. Comput. Biomed. Res., 4: 329-339, 1971. 4. Atkinson, J. R., Shurtleff, D. B., and Foltz, E. L. Radio telemetry for the measurement of intracranial pressure. J. N eurosurg., 27: 428-432, 1967. 5. Bartter, F. C., and Schwartz, W. B. The syndrome of inappropriate secretion of antidiuretic hormone. Am. J. Med., 42: 790-806,1967. 6. Bowden, K. F., and MacCallum, I. R. A computer based approach towards an

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7. 8.

9. 10. 11.

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MONITORING: HEAD INJURIES

CLINICAL NEUROSURGERY

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MONITORING: HEAD INJURIES

Monitoring of patients with head injuries.

A practical protocol for evaluating and monitoring head injured patients has been presented. It has been stressed that monitoring is an ongoing proces...
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