Neurosurgery 1992-98 November 1992, Volume 31, Number 5 918 Monitoring of Brain Tissue Pressure with a Fiberoptic Device Clinical Study AUTHOR(S): Gambardella, Giuseppe, M.D.; d'Avella, Domenico, M.D.; Tomasello, Francesco, M.D. Neurosurgical Clinic, University of Messina, Messina, Italy
(1-5,8,10-12) with this device appears to indicate that it is a simple and reliable system for ICP monitoring. Claims of substantial advantages over other devices presently in use, particularly with regard to its capability to measure brain parenchymal pressures, have also been made (3,8). The purpose of the present study was twofold. First, we report on our clinical experience using intracerebrally placed fiberoptic microtransducers to perform routine monitoring of brain tissue pressure in a general neurosurgical practice. Second, we explore regional relationships in brain tissue pressure in patients in particular clinical situations.
ABSTRACT: CONTINUOUS MONITORING OF brain tissue pressure can now be achieved with intracerebral placement of fiberoptic microtransducers. This study was undertaken to test the safety, accuracy, and reliability of this relatively new type of intracranial pressure (ICP) monitoring. Initially, the fiberoptic device was compared with a concurrently functioning intraventricular catheter in 18 patients. The results from the two methods corresponded closely over a wide range of pressures, and the correlation coefficient approached 1.0. Subsequently, this monitor was used for routine measurement of ICP in a series of almost 200 neurosurgical patients at risk of intracranial hypertension. The tracings showed good wave forms and consistent absolute values of ICP. No instances of hemorrhage, mechanical failure, or other complications were associated with this monitor, except one case of infection, which was not directly attributable to the device per se. When bilateral intraparenchymal pressures were recorded in patients with unilateral mass lesions, significant transitory pressure differentials between the ipsilateral and contralateral sides were documented. It is concluded that monitoring intraparenchymal pressure with the fiberoptic device offers safe and reliable ICP recordings for routine neurosurgical practice. In patients with unilateral masses, ICP should be measured in close proximity to the lesion. KEY WORDS: Brain tissue pressure; Fiberoptics; Intracranial pressure Intracranial pressure (ICP) monitoring is now widely accepted in the management of a variety of neurosurgical patients at risk of intracranial hypertension, especially those with hydrocephalus and severe head injuries. The ICP monitoring devices currently in use include epidural and subdural monitors, subarachnoid screws and bolts, and ventricular catheters. Advantages and problems with all of these devices have been recognized and thoroughly reviewed; the accuracy, reliability, and risk-benefit ratio of each device are still the object of debate in the relevant literature. The need for improved methods of ICP monitoring continues. The fiberoptic device represents a relatively new technical development in this field. The preliminary experimental and clinical experience
Downloaded from https://academic.oup.com/neurosurgery/article-abstract/31/5/918/2549012 by guest on 05 March 2018
PATIENTS AND METHODS In the last few years, recordings of brain tissue pressure were carried out at the neurosurgical clinic of the University of Messina in 209 patients in various clinical situations using the Camino intraparenchymal fiberoptic device and either the 420 OLM intracranial pressure monitor (Camino Laboratories, San Diego, CA) or, more recently, the V420 (Camino Laboratories) monitor. For preliminary validation studies, the device was used in conjunction with a traditional ICP monitor connected to an intraventricular catheter in 18 patients in whom a ventriculostomy had been performed as part of the routine management of hydrocephalus. The intraparenchymal device was used as the sole monitor of ICP in 191 patients of both sexes, but predominantly male, ranging in age from 2 to 79 years. In six of these subjects harboring a unilateral supratentorial expanding mass not treated surgically, concurrent bilateral comparative measures of the intraparenchymal pressure were performed. The Camino fiberoptic device and its assembly, implantation, and use have been fully described previously (2,3). In brief, the microtransducer was introduced through a burr hole in the right frontal region. After puncture of the dura and coagulation of the arachnoid membranes, the tip of the device was inserted a few centimeters into the white matter. In patients who underwent the insertion of an intraparenchymatous microtransducer and an intraventricular catheter, the intraventricular catheter and the microtransducer were introduced through separate burr holes. In the six patients who underwent bilateral recording, two intraparenchymal fiberoptic devices were simultaneously inserted bilaterally into the frontal white matter. In all cases, the transducer was calibrated immediately before use. RESULTS Validation studies In the preliminary part of this investigation, the fiberoptic device was used along with a traditional intraventricular ICP monitor. During these studies, particular attention was given to ensure that the fiberoptic device and the intraventricular monitor originated consistent ICP values and wave forms, both at baseline and during the course of therapeutic manipulations such as hyperventilation, cerebrospinal fluid withdrawal, or drug administration. For the purpose of data analysis and statistical
Redistribution of this article permitted only in accordance with the publisher’s copyright provisions.
Neurosurgery 31; 918-922, 1992
Routine clinical use After completion of preliminary validation studies, in which no complications were associated with the use of this monitor and brain tissue pressure correlated well with ventricular pressure acutely and over a clinically relevant time period, we used the fiberoptic device as the sole monitor of ICP in 191 patients in various clinical situations. The patients were studied over periods ranging from 11 to 74 hours, as clinically indicated. Table 3 summarizes the average length of monitoring for each group of patients, and their clinical diagnoses. The tracings showed good wave forms and absolute values for ICP consistent with each clinical situation. On the basis of information provided by this monitor, routine management decisions were made that correlated well with the patient's clinical evolution and outcome. No instances of hemorrhage, mechanical failure, or other complications were associated with this monitor. On only one occasion was an infection related to the use of the fiberoptic system. The probable cause was the involuntary withdrawal of the device by an uncooperative patient, causing cerebrospinal fluid leakage and meningitis. Careful fixation of the device to the head prevented this problem in subsequent cases. Bilateral brain tissue pressure recording In general, in the six subjects with unilateral mass lesions, who underwent simultaneous bilateral recording of brain tissue pressure, tracings from the two fiberoptic devices corresponded closely with each other. In four instances, however, transient significant gradients in pressure between the two sides were observed, averaging 10 to 20 mm Hg, and lasting no more than 1 to 2 hours (Fig. 2). When these gradients again became equilibrated, the differential pressures were no longer observed. The occurrence of such gradients in pressure prompted rapid rescanning of the patients and was found to be associated with an acute increase in the volume of the ipsilateral mass
Downloaded from https://academic.oup.com/neurosurgery/article-abstract/31/5/918/2549012 by guest on 05 March 2018
lesion (namely, an acute subdural hematoma, a delayed intracerebral hematoma, and two cases of worsening of perilesional edema). DISCUSSION Debate continues in the relevant literature about the risk-benefit and cost-effectiveness ratios of ICP monitoring. None of the methods currently in use for monitoring ICP is ideal, each having advantages and disadvantages. The major advantages of monitoring ICP from within the brain parenchyma by means of the transducer-tipped fiberoptic probe are as follows: it is easy to place and to use; it is solid state, which alleviates the problems common to fluid-filled systems; and it allows direct measurement of brain tissue pressure in patients with compressed or dislocated ventricles in which registration of intraventricular pressure may be difficult or precluded. In the present study, we first evaluated the accuracy of this monitor by comparing it with readings obtained by a standard method of ICP recording, namely, ventricular catheter monitoring. We found that the fiberoptic system provides characteristic ICP wave forms, has a rapid response rate during the course of various therapeutic manipulations, and correlates well with ventricular pressure, both acutely and over a clinically relevant period of time. A correlation coefficient approaching 1.0 was obtained when the two sets of data were compared. In general, the brain tissue pressure was slightly lower (within 1-2 mm Hg) than the ventricular fluid pressure. Although this observation does not mirror others' experience (6,8), similar findings, based on a large clinical series, have recently been reported (9). Such discrepancies are possibly a function of the device, or could be accounted for by the positional difference in the two devices. Since the correspondence between paired measurements of intraventricular and brain tissue pressure was judged satisfactory, we subsequently evaluated the safety and clinical reliability of this device in a series of almost 200 neurosurgical patients. The tracings showed characteristic wave forms and brain tissue pressures consistent with the different clinical situations. On the basis of the information provided by this monitor, routine management decisions were made that correlated well with the patient's clinical evolution and outcome. No instances of hemorrhage, mechanical failure, or other complications were associated with this monitor, with the exception of one case of infection that was not directly attributable to the device per se. This technique is therefore a reliable method of measuring ICP, and it is now a routine procedure in our department. Two main disadvantages deserve some comment: first, the fiberoptic probe must be used along with a ventriculostomy when cerebrospinal fluid drainage is clinically required; second, the microtransducer cannot be recalibrated in situ and, therefore, the accuracy of readings over a rather long period of time may be questionable. Although accurate drift studies have shown that for short-term
Redistribution of this article permitted only in accordance with the publisher’s copyright provisions.
evaluation, mean ICP values (diastolic pressure plus one-third pulse pressure) were calculated for both systems from a 3-minute recording period measured at 3-hour intervals and averaged to produce 180 data points. Table 1 charts the number of observations of the two pressure recordings in intervals of 5 mm Hg. The predominant feature is the high number of readings on or about the diagonal of equity. The results from the two methods corresponded closely over a wide range of pressures; also, the relative change in ICP observed in response to any of the therapeutic manipulations was very similar in both devices. The intraventricular pressure averaged 17.71 ± 4.86 mm Hg and the intraparenchymal pressure averaged 15.81 ± 4.93 mm Hg. For purposes of comparison, linear regression analysis was used to examine the absolute ICP values from the ventriculostomy and from the intraparenchymal transducer. The correlation coefficient for each study ranged from 0.586 to 0.996. For the complete data set, the correlation coefficient was 0.946 (Table 2 and Fig. 1).
4.
5.
6.
7.
8.
9.
10.
11. Received, December 19, 1991. Accepted, February 14, 1992. Reprint requests: Domenico d'Avella, M.D., Neurosurgical Clinic, Policlinico Universitario, 98100, Messina, Italy. REFERENCES: (1-14) 12. 1.
2.
3.
Cathey SL, Chadduck WM: The Camino intracranial pressure monitor: Performance in experimental and clinical trials. Neurosurgery 21:116, 1987 (abstr). Chambers IR, Mendelow AD, Sinar EJ, Modha P: A clinical evaluation of the Camino subdural screw and ventricular monitoring kits. Neurosurgery 26:421-423, 1990. Crutchfield JS, Narayan RK, Robertson CS, Michael LH: Evaluation of a fiberoptic intracranial pressure monitor. J Neurosurg 72:482- 487, 1990.
Downloaded from https://academic.oup.com/neurosurgery/article-abstract/31/5/918/2549012 by guest on 05 March 2018
13. 14.
Gambardella G, d'Avella D, Staropoli C, Toscano S, Tomasello F: Bilateral intraparenchymal pressure in patients with unilateral supratentorial mass lesions. Proceedings of the Eighth International Symposium on Intracranial Pressure: ICP and Craniospinal Dynamics, Rotterdam, The Netherlands, June 16-20, No. 039, 1991 (abstr). Gambardella G, Caruso G, Staropoli C, Tomasello F, Grisoli F, Vincentelli F, Venuti FS: Intérêt du monitorage informatisé de la pression intra-crânienne en neurotraumatologie. Aggressologie 29:343348, 1988. Horwitz N: Comment to Chambers IR, Mendelow AD, Sinar EJ, Modha P: A clinical evaluation of the Camino subdural screw and ventricular monitoring kits. Neurosurgery 26:421-423, 1990. Iannotti F, Hoff JT, Schielke GP: Brain tissue pressure: Physiological observations in anesthetized cats. J Neurosurg 60:1219-1225, 1984. Ostrup RC, Luerssen TG, Marshall LF, Zornow MH: Continous monitoring of intracranial pressure with a miniaturized fiberoptic device. J Neurosurg 67:206-209, 1987. Piek J, Bock WJ: Continous monitoring of supratentorial cerebral tissue pressure in neurosurgical routine (experiences with 125 patients). Proceedings of the Eighth International Symposium on Intracranial Pressure: ICP and Craniospinal Dynamics, Rotterdam, The Netherlands, June 16-20, No. 003, 1991 (abstr). Robertson CS, Narayan RK, Contant CF, Grossman RG, Gokaslan ZL, Pahwa R, Caram P, Bray RS Jr, Sherwood AM: Clinical experience with a continous monitor of intracranial compliance. J Neurosurg 71:673680, 1989. Statham P, Midley S, Dearden M, Miller JD: A clinical evaluation of the Camino intraparenchymal pressure transducer. Proceedings of the Eighth International Symposium on Intracranial Pressure: ICP and Craniospinal Dynamics, Rotterdam, The Netherlands, June 16-20, No. 021, 1991 (abstr). Sundbarg G, Nordstrom CH, Messeter K, Soderstrom S: A comparison of intraparenchymatous and intraventricular pressure recording in clinical practice. J Neurosurg 67:841-845, 1987. Weaver DD, Winn HR, Jane JJ: differential intracranial pressure in patients with unilateral mass lesions. J Neurosurg 56:660-665, 1982. Yano M, Ikeda Y, Kobayashi S, Otsuka T: Intracranial pressure in head-injured patients with various intracranial lesions is identical throughout the supratentorial intracranial compartment. Neurosurgery 21:688-692,
Redistribution of this article permitted only in accordance with the publisher’s copyright provisions.
ICP monitoring, this device exhibits relatively little drift (average daily drift, ±0.6 mm Hg) (3), we did not prolong our studies for more than 3 days, and suggest that after this time, the fiberoptic device should be replaced. With regard to the issue of the compartmental pressure relationships in patients harboring unilateral supratentorial mass lesions, our results, although based on a limited number of patients, corroborate and confirm previous clinical observations by Yano et al. (14) that the supratentorial space can generally be considered one compartment, regardless of the differences in localization of chronic or slowly evolving unilateral mass lesions. The present data, however, do not support the experimental observations of Crutchfield et al. (3) that acute pressure changes between the brain parenchyma ipsilateral and contralateral to an expanding mass occur simultaneously and at the same rate bilaterally. Conversely, in our experience, an abrupt increase in volume in one hemisphere results in a significant acute increase in ipsilateral brain tissue pressure. This unequal pressure distribution may last for 1 to 2 hours. Subsequently, such gradients become equilibrated and differential pressures are no longer observed. These clinical observations, similar to those reported by Weaver et al. (13), are in keeping with the concept of "local pressure," the pathogenesis of which, involving cerebrospinal fluid dynamics, regulation of cerebral blood flow, or viscoelastic properties of the brain, has been extensively discussed (7,13,14). In conclusion, intraparenchymatous pressure monitoring with the fiberoptic device offers simple, reliable and quantitative ICP recordings for routine neurosurgical practice. In patients with supratentorial unilateral lesions, ICP monitoring should include assessment in areas in close proximity to the mass lesion. Presented in part at The Eighth International Symposium on Intracranial Pressure: ICP and Craniospinal Dynamics, Rotterdam, The Netherlands, June 16-20, 1991.
COMMENTS This paper confirms the reliability and safety of intraparenchymal recordings of intracranial pressure, based on experiences with almost 200 patients in whom the monitor was used. However, controversy over compartmentalization of the supratentorial spaces continues. Six patients had bilateral brain tissue recordings showing pressure differentials averaging 10 to 20 mm Hg that were transient and became equilibrated in 1 to 2 hours. Historically, the literature has reflected some confusion on this issue. Using a Richmond bolt, Weaver et al. (3) found a definite difference in four patients, with much higher pressure recordings on the side of the mass. Yano et al. (4), using another subarachnoid pressure device bilaterally in 15 head-injured subjects, found comparable readings on each side. Marshall (2), commenting on the Yano et al. report, indicated that when he and his colleagues used the Richmond bolt, a gradient differential was noted similar to that reported by Weaver et al. (3), but that bilateral ventriculostomy readings in the same subjects reflected no difference on the two sides. He wondered whether there was some technical reason why the Richmond bolt readings were disparate. Finally, in a solitary dog experiment, Crutchfield et al. (1), recording with a bilateral intraparenchymal Camino device, found no heightened pressure related to the side of induced increase in mass. Norman H. Horwitz Washington, District of Columbia REFERENCES: (1-4) 1.
2.
3. 4.
Crutchfield JS, Narayan AK, Robertson CS, Michael LH: Evaluation of a fiberoptic intracranial pressure monitor. J Neurosurg 72:482-487, 1990. Marshall LF: Comment on Yano M, Ikeda Y, Kobayashi S, Otsuka T: Intracranial pressure in head-injured patients with various intracranial lesions is identical throughout the supratentorial compartment. Neurosurgery 21:692, 1987. Weaver DD, Winn HA, Jane JJ: Differential intracranial pressure in patients with unilateral mass lesions. J Neurosurg 56:660-665, 1982. Yano M, Ikeda Y, Kobayashi S, Otsuka T: Intracranial pressure in head-injured patients with various intracranial lesions is identical throughout the supratentorial compartment. Neurosurgery 21:688-692, 1987.
noted four instances of transient significant pressure discrepancies between the two hemispheres--the phenomenon of plastic deformity and slow pressure transmission that has previously been well described. The important contribution made in this study, however, is that in each of these instances, a specific pathological process was disclosed on follow-up imaging studies to explain these observations and to highlight the importance of having made the observations. The accuracy of the Camino device in comparison to intraventricular monitoring was documented with a correlation coefficient greater than 0.90 for 17 of 18 patients. Presumably, the 18th patient exhibited considerable transient differentials. While the pressure correlation between the two devices is linear, a mean pressure difference of nearly 1 mm Hg was noted. Furthermore, the regression slope is not a 45degree slope, since the mean pressure difference between the two devices is 4.5 mm Hg at the low end, but only 1.0 mm Hg at the more important upper end. The reliability of the Camino device over time is left in question. The authors refer to previously published data suggesting an average baseline drift of ±0.6 mm Hg per day for Camino devices, but they did not tell us what baseline drift they actually observed in their patients after clinical use at sometimes elevated pressures. The manufacturer refers to a maximum drift of 3 mm Hg per day, and Narayan et al. (2) reported a maximum drift of 2 mm Hg and a mean drift of 0.75 mm Hg per 8-hour shift. These authors were sufficiently concerned about baseline drift that they advocate not using this form of monitoring for more than 3 days. Consideration of the clinical usefulness of the Camino device includes questions of its accuracy and its baseline stability, but also a consideration of the fact that the device is not fluid coupled. While this obviates some of the problems associated with fluid coupling, it denies the user the opportunity for in situ confirmation of baseline accuracy and for doing volumetric pressure testing of ICP compliance or reserve, which has been shown to correlate nicely with impending decompression (1). The authors observed no infections related specifically to ICP monitoring in their small group of patients, but they give no detailed discussion of the relative risk-benefit ratio of intraparenchymal monitoring (including the necessity of brain penetration and the risk of brain abscess) versus the use of subdural catheter monitoring devices. Harold A. Wilkinson Worcester, Massachusetts REFERENCES: (1,2) 1.
This paper further confirms the clinical usefulness of the Camino intracranial pressure (ICP) monitor for short-term clinical use, but it also adds valuable information to our understanding of the pathophysiology of raised ICP. In a series of 6 patients with bilateral ICP monitoring, the authors
Downloaded from https://academic.oup.com/neurosurgery/article-abstract/31/5/918/2549012 by guest on 05 March 2018
2.
Guertin SR, Gordon GJ, Levinsohn MW, Rekate HL: Intracranial volume pressure response in infants and children: Preliminary report of a predictive marker in metabolic coma. Crit Care Med 10:1-4, 1982. Narayan RK, Bray RS, Robertson CS, Gokaslan ZL, Grosman RG: Experience with a
Redistribution of this article permitted only in accordance with the publisher’s copyright provisions.
1987.
Redistribution of this article permitted only in accordance with the publisher’s copyright provisions.
new fiberoptic device for intracranial pressure monitoring. Presented at the annual meeting of the American Association of Neurological Surgeons, Dallas, Texas, May 3, 1987.
Downloaded from https://academic.oup.com/neurosurgery/article-abstract/31/5/918/2549012 by guest on 05 March 2018
Redistribution of this article permitted only in accordance with the publisher’s copyright provisions.
Figure 1. Linear regression analysis for measurements of intraventricular (cerebrospinal fluid) pressure compared with measurements of brain tissue pressure.
Downloaded from https://academic.oup.com/neurosurgery/article-abstract/31/5/918/2549012 by guest on 05 March 2018
Table 1. Intraparenchymatous Pressure Compared with Intraventricular Pressure
Downloaded from https://academic.oup.com/neurosurgery/article-abstract/31/5/918/2549012 by guest on 05 March 2018
Redistribution of this article permitted only in accordance with the publisher’s copyright provisions.
Figure 2. Chart recording showing bilateral simultaneous brain tissue pressure in a patient with a unilateral supratentorial expanding mass: top, tracing contralateral to the mass; bottom, tracing ipsilateral to the mass. Transient marked differential ICPs are noted with elevation on the ipsilateral side.
Table 3. Clinical Diagnoses and Average Length of Monitoring in 209 Patients
Downloaded from https://academic.oup.com/neurosurgery/article-abstract/31/5/918/2549012 by guest on 05 March 2018
Redistribution of this article permitted only in accordance with the publisher’s copyright provisions.
Table 2. Readings from 18 Patients Who Underwent Concurrent Intraparenchymal and Intraventricular Monitoring
(1-5,8,10-12) with this device appears to indicate that it is a simple and reliable system for ICP monitoring. Claims of substantial advantages over other devices presently in use, particularly with regard to its capability to measure brain parenchymal pressures, have also been made (3,8). The purpose of the present study was twofold. First, we report on our clinical experience using intracerebrally placed fiberoptic microtransducers to perform routine monitoring of brain tissue pressure in a general neurosurgical practice. Second, we explore regional relationships in brain tissue pressure in patients in particular clinical situations.
ABSTRACT: CONTINUOUS MONITORING OF brain tissue pressure can now be achieved with intracerebral placement of fiberoptic microtransducers. This study was undertaken to test the safety, accuracy, and reliability of this relatively new type of intracranial pressure (ICP) monitoring. Initially, the fiberoptic device was compared with a concurrently functioning intraventricular catheter in 18 patients. The results from the two methods corresponded closely over a wide range of pressures, and the correlation coefficient approached 1.0. Subsequently, this monitor was used for routine measurement of ICP in a series of almost 200 neurosurgical patients at risk of intracranial hypertension. The tracings showed good wave forms and consistent absolute values of ICP. No instances of hemorrhage, mechanical failure, or other complications were associated with this monitor, except one case of infection, which was not directly attributable to the device per se. When bilateral intraparenchymal pressures were recorded in patients with unilateral mass lesions, significant transitory pressure differentials between the ipsilateral and contralateral sides were documented. It is concluded that monitoring intraparenchymal pressure with the fiberoptic device offers safe and reliable ICP recordings for routine neurosurgical practice. In patients with unilateral masses, ICP should be measured in close proximity to the lesion. KEY WORDS: Brain tissue pressure; Fiberoptics; Intracranial pressure Intracranial pressure (ICP) monitoring is now widely accepted in the management of a variety of neurosurgical patients at risk of intracranial hypertension, especially those with hydrocephalus and severe head injuries. The ICP monitoring devices currently in use include epidural and subdural monitors, subarachnoid screws and bolts, and ventricular catheters. Advantages and problems with all of these devices have been recognized and thoroughly reviewed; the accuracy, reliability, and risk-benefit ratio of each device are still the object of debate in the relevant literature. The need for improved methods of ICP monitoring continues. The fiberoptic device represents a relatively new technical development in this field. The preliminary experimental and clinical experience
Downloaded from https://academic.oup.com/neurosurgery/article-abstract/31/5/918/2549012 by guest on 05 March 2018
PATIENTS AND METHODS In the last few years, recordings of brain tissue pressure were carried out at the neurosurgical clinic of the University of Messina in 209 patients in various clinical situations using the Camino intraparenchymal fiberoptic device and either the 420 OLM intracranial pressure monitor (Camino Laboratories, San Diego, CA) or, more recently, the V420 (Camino Laboratories) monitor. For preliminary validation studies, the device was used in conjunction with a traditional ICP monitor connected to an intraventricular catheter in 18 patients in whom a ventriculostomy had been performed as part of the routine management of hydrocephalus. The intraparenchymal device was used as the sole monitor of ICP in 191 patients of both sexes, but predominantly male, ranging in age from 2 to 79 years. In six of these subjects harboring a unilateral supratentorial expanding mass not treated surgically, concurrent bilateral comparative measures of the intraparenchymal pressure were performed. The Camino fiberoptic device and its assembly, implantation, and use have been fully described previously (2,3). In brief, the microtransducer was introduced through a burr hole in the right frontal region. After puncture of the dura and coagulation of the arachnoid membranes, the tip of the device was inserted a few centimeters into the white matter. In patients who underwent the insertion of an intraparenchymatous microtransducer and an intraventricular catheter, the intraventricular catheter and the microtransducer were introduced through separate burr holes. In the six patients who underwent bilateral recording, two intraparenchymal fiberoptic devices were simultaneously inserted bilaterally into the frontal white matter. In all cases, the transducer was calibrated immediately before use. RESULTS Validation studies In the preliminary part of this investigation, the fiberoptic device was used along with a traditional intraventricular ICP monitor. During these studies, particular attention was given to ensure that the fiberoptic device and the intraventricular monitor originated consistent ICP values and wave forms, both at baseline and during the course of therapeutic manipulations such as hyperventilation, cerebrospinal fluid withdrawal, or drug administration. For the purpose of data analysis and statistical
Redistribution of this article permitted only in accordance with the publisher’s copyright provisions.
Neurosurgery 31; 918-922, 1992
Routine clinical use After completion of preliminary validation studies, in which no complications were associated with the use of this monitor and brain tissue pressure correlated well with ventricular pressure acutely and over a clinically relevant time period, we used the fiberoptic device as the sole monitor of ICP in 191 patients in various clinical situations. The patients were studied over periods ranging from 11 to 74 hours, as clinically indicated. Table 3 summarizes the average length of monitoring for each group of patients, and their clinical diagnoses. The tracings showed good wave forms and absolute values for ICP consistent with each clinical situation. On the basis of information provided by this monitor, routine management decisions were made that correlated well with the patient's clinical evolution and outcome. No instances of hemorrhage, mechanical failure, or other complications were associated with this monitor. On only one occasion was an infection related to the use of the fiberoptic system. The probable cause was the involuntary withdrawal of the device by an uncooperative patient, causing cerebrospinal fluid leakage and meningitis. Careful fixation of the device to the head prevented this problem in subsequent cases. Bilateral brain tissue pressure recording In general, in the six subjects with unilateral mass lesions, who underwent simultaneous bilateral recording of brain tissue pressure, tracings from the two fiberoptic devices corresponded closely with each other. In four instances, however, transient significant gradients in pressure between the two sides were observed, averaging 10 to 20 mm Hg, and lasting no more than 1 to 2 hours (Fig. 2). When these gradients again became equilibrated, the differential pressures were no longer observed. The occurrence of such gradients in pressure prompted rapid rescanning of the patients and was found to be associated with an acute increase in the volume of the ipsilateral mass
Downloaded from https://academic.oup.com/neurosurgery/article-abstract/31/5/918/2549012 by guest on 05 March 2018
lesion (namely, an acute subdural hematoma, a delayed intracerebral hematoma, and two cases of worsening of perilesional edema). DISCUSSION Debate continues in the relevant literature about the risk-benefit and cost-effectiveness ratios of ICP monitoring. None of the methods currently in use for monitoring ICP is ideal, each having advantages and disadvantages. The major advantages of monitoring ICP from within the brain parenchyma by means of the transducer-tipped fiberoptic probe are as follows: it is easy to place and to use; it is solid state, which alleviates the problems common to fluid-filled systems; and it allows direct measurement of brain tissue pressure in patients with compressed or dislocated ventricles in which registration of intraventricular pressure may be difficult or precluded. In the present study, we first evaluated the accuracy of this monitor by comparing it with readings obtained by a standard method of ICP recording, namely, ventricular catheter monitoring. We found that the fiberoptic system provides characteristic ICP wave forms, has a rapid response rate during the course of various therapeutic manipulations, and correlates well with ventricular pressure, both acutely and over a clinically relevant period of time. A correlation coefficient approaching 1.0 was obtained when the two sets of data were compared. In general, the brain tissue pressure was slightly lower (within 1-2 mm Hg) than the ventricular fluid pressure. Although this observation does not mirror others' experience (6,8), similar findings, based on a large clinical series, have recently been reported (9). Such discrepancies are possibly a function of the device, or could be accounted for by the positional difference in the two devices. Since the correspondence between paired measurements of intraventricular and brain tissue pressure was judged satisfactory, we subsequently evaluated the safety and clinical reliability of this device in a series of almost 200 neurosurgical patients. The tracings showed characteristic wave forms and brain tissue pressures consistent with the different clinical situations. On the basis of the information provided by this monitor, routine management decisions were made that correlated well with the patient's clinical evolution and outcome. No instances of hemorrhage, mechanical failure, or other complications were associated with this monitor, with the exception of one case of infection that was not directly attributable to the device per se. This technique is therefore a reliable method of measuring ICP, and it is now a routine procedure in our department. Two main disadvantages deserve some comment: first, the fiberoptic probe must be used along with a ventriculostomy when cerebrospinal fluid drainage is clinically required; second, the microtransducer cannot be recalibrated in situ and, therefore, the accuracy of readings over a rather long period of time may be questionable. Although accurate drift studies have shown that for short-term
Redistribution of this article permitted only in accordance with the publisher’s copyright provisions.
evaluation, mean ICP values (diastolic pressure plus one-third pulse pressure) were calculated for both systems from a 3-minute recording period measured at 3-hour intervals and averaged to produce 180 data points. Table 1 charts the number of observations of the two pressure recordings in intervals of 5 mm Hg. The predominant feature is the high number of readings on or about the diagonal of equity. The results from the two methods corresponded closely over a wide range of pressures; also, the relative change in ICP observed in response to any of the therapeutic manipulations was very similar in both devices. The intraventricular pressure averaged 17.71 ± 4.86 mm Hg and the intraparenchymal pressure averaged 15.81 ± 4.93 mm Hg. For purposes of comparison, linear regression analysis was used to examine the absolute ICP values from the ventriculostomy and from the intraparenchymal transducer. The correlation coefficient for each study ranged from 0.586 to 0.996. For the complete data set, the correlation coefficient was 0.946 (Table 2 and Fig. 1).
4.
5.
6.
7.
8.
9.
10.
11. Received, December 19, 1991. Accepted, February 14, 1992. Reprint requests: Domenico d'Avella, M.D., Neurosurgical Clinic, Policlinico Universitario, 98100, Messina, Italy. REFERENCES: (1-14) 12. 1.
2.
3.
Cathey SL, Chadduck WM: The Camino intracranial pressure monitor: Performance in experimental and clinical trials. Neurosurgery 21:116, 1987 (abstr). Chambers IR, Mendelow AD, Sinar EJ, Modha P: A clinical evaluation of the Camino subdural screw and ventricular monitoring kits. Neurosurgery 26:421-423, 1990. Crutchfield JS, Narayan RK, Robertson CS, Michael LH: Evaluation of a fiberoptic intracranial pressure monitor. J Neurosurg 72:482- 487, 1990.
Downloaded from https://academic.oup.com/neurosurgery/article-abstract/31/5/918/2549012 by guest on 05 March 2018
13. 14.
Gambardella G, d'Avella D, Staropoli C, Toscano S, Tomasello F: Bilateral intraparenchymal pressure in patients with unilateral supratentorial mass lesions. Proceedings of the Eighth International Symposium on Intracranial Pressure: ICP and Craniospinal Dynamics, Rotterdam, The Netherlands, June 16-20, No. 039, 1991 (abstr). Gambardella G, Caruso G, Staropoli C, Tomasello F, Grisoli F, Vincentelli F, Venuti FS: Intérêt du monitorage informatisé de la pression intra-crânienne en neurotraumatologie. Aggressologie 29:343348, 1988. Horwitz N: Comment to Chambers IR, Mendelow AD, Sinar EJ, Modha P: A clinical evaluation of the Camino subdural screw and ventricular monitoring kits. Neurosurgery 26:421-423, 1990. Iannotti F, Hoff JT, Schielke GP: Brain tissue pressure: Physiological observations in anesthetized cats. J Neurosurg 60:1219-1225, 1984. Ostrup RC, Luerssen TG, Marshall LF, Zornow MH: Continous monitoring of intracranial pressure with a miniaturized fiberoptic device. J Neurosurg 67:206-209, 1987. Piek J, Bock WJ: Continous monitoring of supratentorial cerebral tissue pressure in neurosurgical routine (experiences with 125 patients). Proceedings of the Eighth International Symposium on Intracranial Pressure: ICP and Craniospinal Dynamics, Rotterdam, The Netherlands, June 16-20, No. 003, 1991 (abstr). Robertson CS, Narayan RK, Contant CF, Grossman RG, Gokaslan ZL, Pahwa R, Caram P, Bray RS Jr, Sherwood AM: Clinical experience with a continous monitor of intracranial compliance. J Neurosurg 71:673680, 1989. Statham P, Midley S, Dearden M, Miller JD: A clinical evaluation of the Camino intraparenchymal pressure transducer. Proceedings of the Eighth International Symposium on Intracranial Pressure: ICP and Craniospinal Dynamics, Rotterdam, The Netherlands, June 16-20, No. 021, 1991 (abstr). Sundbarg G, Nordstrom CH, Messeter K, Soderstrom S: A comparison of intraparenchymatous and intraventricular pressure recording in clinical practice. J Neurosurg 67:841-845, 1987. Weaver DD, Winn HR, Jane JJ: differential intracranial pressure in patients with unilateral mass lesions. J Neurosurg 56:660-665, 1982. Yano M, Ikeda Y, Kobayashi S, Otsuka T: Intracranial pressure in head-injured patients with various intracranial lesions is identical throughout the supratentorial intracranial compartment. Neurosurgery 21:688-692,
Redistribution of this article permitted only in accordance with the publisher’s copyright provisions.
ICP monitoring, this device exhibits relatively little drift (average daily drift, ±0.6 mm Hg) (3), we did not prolong our studies for more than 3 days, and suggest that after this time, the fiberoptic device should be replaced. With regard to the issue of the compartmental pressure relationships in patients harboring unilateral supratentorial mass lesions, our results, although based on a limited number of patients, corroborate and confirm previous clinical observations by Yano et al. (14) that the supratentorial space can generally be considered one compartment, regardless of the differences in localization of chronic or slowly evolving unilateral mass lesions. The present data, however, do not support the experimental observations of Crutchfield et al. (3) that acute pressure changes between the brain parenchyma ipsilateral and contralateral to an expanding mass occur simultaneously and at the same rate bilaterally. Conversely, in our experience, an abrupt increase in volume in one hemisphere results in a significant acute increase in ipsilateral brain tissue pressure. This unequal pressure distribution may last for 1 to 2 hours. Subsequently, such gradients become equilibrated and differential pressures are no longer observed. These clinical observations, similar to those reported by Weaver et al. (13), are in keeping with the concept of "local pressure," the pathogenesis of which, involving cerebrospinal fluid dynamics, regulation of cerebral blood flow, or viscoelastic properties of the brain, has been extensively discussed (7,13,14). In conclusion, intraparenchymatous pressure monitoring with the fiberoptic device offers simple, reliable and quantitative ICP recordings for routine neurosurgical practice. In patients with supratentorial unilateral lesions, ICP monitoring should include assessment in areas in close proximity to the mass lesion. Presented in part at The Eighth International Symposium on Intracranial Pressure: ICP and Craniospinal Dynamics, Rotterdam, The Netherlands, June 16-20, 1991.
COMMENTS This paper confirms the reliability and safety of intraparenchymal recordings of intracranial pressure, based on experiences with almost 200 patients in whom the monitor was used. However, controversy over compartmentalization of the supratentorial spaces continues. Six patients had bilateral brain tissue recordings showing pressure differentials averaging 10 to 20 mm Hg that were transient and became equilibrated in 1 to 2 hours. Historically, the literature has reflected some confusion on this issue. Using a Richmond bolt, Weaver et al. (3) found a definite difference in four patients, with much higher pressure recordings on the side of the mass. Yano et al. (4), using another subarachnoid pressure device bilaterally in 15 head-injured subjects, found comparable readings on each side. Marshall (2), commenting on the Yano et al. report, indicated that when he and his colleagues used the Richmond bolt, a gradient differential was noted similar to that reported by Weaver et al. (3), but that bilateral ventriculostomy readings in the same subjects reflected no difference on the two sides. He wondered whether there was some technical reason why the Richmond bolt readings were disparate. Finally, in a solitary dog experiment, Crutchfield et al. (1), recording with a bilateral intraparenchymal Camino device, found no heightened pressure related to the side of induced increase in mass. Norman H. Horwitz Washington, District of Columbia REFERENCES: (1-4) 1.
2.
3. 4.
Crutchfield JS, Narayan AK, Robertson CS, Michael LH: Evaluation of a fiberoptic intracranial pressure monitor. J Neurosurg 72:482-487, 1990. Marshall LF: Comment on Yano M, Ikeda Y, Kobayashi S, Otsuka T: Intracranial pressure in head-injured patients with various intracranial lesions is identical throughout the supratentorial compartment. Neurosurgery 21:692, 1987. Weaver DD, Winn HA, Jane JJ: Differential intracranial pressure in patients with unilateral mass lesions. J Neurosurg 56:660-665, 1982. Yano M, Ikeda Y, Kobayashi S, Otsuka T: Intracranial pressure in head-injured patients with various intracranial lesions is identical throughout the supratentorial compartment. Neurosurgery 21:688-692, 1987.
noted four instances of transient significant pressure discrepancies between the two hemispheres--the phenomenon of plastic deformity and slow pressure transmission that has previously been well described. The important contribution made in this study, however, is that in each of these instances, a specific pathological process was disclosed on follow-up imaging studies to explain these observations and to highlight the importance of having made the observations. The accuracy of the Camino device in comparison to intraventricular monitoring was documented with a correlation coefficient greater than 0.90 for 17 of 18 patients. Presumably, the 18th patient exhibited considerable transient differentials. While the pressure correlation between the two devices is linear, a mean pressure difference of nearly 1 mm Hg was noted. Furthermore, the regression slope is not a 45degree slope, since the mean pressure difference between the two devices is 4.5 mm Hg at the low end, but only 1.0 mm Hg at the more important upper end. The reliability of the Camino device over time is left in question. The authors refer to previously published data suggesting an average baseline drift of ±0.6 mm Hg per day for Camino devices, but they did not tell us what baseline drift they actually observed in their patients after clinical use at sometimes elevated pressures. The manufacturer refers to a maximum drift of 3 mm Hg per day, and Narayan et al. (2) reported a maximum drift of 2 mm Hg and a mean drift of 0.75 mm Hg per 8-hour shift. These authors were sufficiently concerned about baseline drift that they advocate not using this form of monitoring for more than 3 days. Consideration of the clinical usefulness of the Camino device includes questions of its accuracy and its baseline stability, but also a consideration of the fact that the device is not fluid coupled. While this obviates some of the problems associated with fluid coupling, it denies the user the opportunity for in situ confirmation of baseline accuracy and for doing volumetric pressure testing of ICP compliance or reserve, which has been shown to correlate nicely with impending decompression (1). The authors observed no infections related specifically to ICP monitoring in their small group of patients, but they give no detailed discussion of the relative risk-benefit ratio of intraparenchymal monitoring (including the necessity of brain penetration and the risk of brain abscess) versus the use of subdural catheter monitoring devices. Harold A. Wilkinson Worcester, Massachusetts REFERENCES: (1,2) 1.
This paper further confirms the clinical usefulness of the Camino intracranial pressure (ICP) monitor for short-term clinical use, but it also adds valuable information to our understanding of the pathophysiology of raised ICP. In a series of 6 patients with bilateral ICP monitoring, the authors
Downloaded from https://academic.oup.com/neurosurgery/article-abstract/31/5/918/2549012 by guest on 05 March 2018
2.
Guertin SR, Gordon GJ, Levinsohn MW, Rekate HL: Intracranial volume pressure response in infants and children: Preliminary report of a predictive marker in metabolic coma. Crit Care Med 10:1-4, 1982. Narayan RK, Bray RS, Robertson CS, Gokaslan ZL, Grosman RG: Experience with a
Redistribution of this article permitted only in accordance with the publisher’s copyright provisions.
1987.
Redistribution of this article permitted only in accordance with the publisher’s copyright provisions.
new fiberoptic device for intracranial pressure monitoring. Presented at the annual meeting of the American Association of Neurological Surgeons, Dallas, Texas, May 3, 1987.
Downloaded from https://academic.oup.com/neurosurgery/article-abstract/31/5/918/2549012 by guest on 05 March 2018
Redistribution of this article permitted only in accordance with the publisher’s copyright provisions.
Figure 1. Linear regression analysis for measurements of intraventricular (cerebrospinal fluid) pressure compared with measurements of brain tissue pressure.
Downloaded from https://academic.oup.com/neurosurgery/article-abstract/31/5/918/2549012 by guest on 05 March 2018
Table 1. Intraparenchymatous Pressure Compared with Intraventricular Pressure
Downloaded from https://academic.oup.com/neurosurgery/article-abstract/31/5/918/2549012 by guest on 05 March 2018
Redistribution of this article permitted only in accordance with the publisher’s copyright provisions.
Figure 2. Chart recording showing bilateral simultaneous brain tissue pressure in a patient with a unilateral supratentorial expanding mass: top, tracing contralateral to the mass; bottom, tracing ipsilateral to the mass. Transient marked differential ICPs are noted with elevation on the ipsilateral side.
Table 3. Clinical Diagnoses and Average Length of Monitoring in 209 Patients
Downloaded from https://academic.oup.com/neurosurgery/article-abstract/31/5/918/2549012 by guest on 05 March 2018
Redistribution of this article permitted only in accordance with the publisher’s copyright provisions.
Table 2. Readings from 18 Patients Who Underwent Concurrent Intraparenchymal and Intraventricular Monitoring
