true when these devices penetrate the electrical barrier provided by the skin and reside within the heart. Therefore, all electrical devices connected to a patient should be attached to a common ground with proper ground wires and threepoint plugs. Most newer devices isolate the patient input circuitry from the power supply, thus providing extra protection should the ground fail. Finally, careful inspection of electrical equipment and connections, and correction of deficiencies

are prudent measures to ensure patient safety. Though nurses and doctors cannot be expected to acquire or be burdened by the expertise of biomedical engineering, some understanding of the use of hemodynamic monitoring equipment may circumvent frustration and wasted time, and contribute to safe and improved management of the critically ill. A more detailed discussion of the issues raised may be found in the references.

I thank Mr. Brian Winchester for technical advice and Mrs. Lolita Sutarno and Mrs. Janis Lukey for secretarial help.

References 1. SCHROEDER JS, DAILY EK: Techniques

in Bedside Hemodynamic Monitoring, Mosby, St Louis, Mo, 1976 2. PIEMME TE: Pressure measurement: electrical pressure transducers. Prog Cardioi'asc Dis 5: 574, 1963 3. MENDEL D: A Practice of Cardiac Catheterization, 2nd ed, Blackwell Sci Publ, Oxford, 1974

Hemodynamic monitoring: catheter insertion techniques, complications and trouble-shooting RONALD S. BAIGRIE, MD;* CHRISTOPHER D. MORGAN, MDt

Hemodynamic monitoring is an important aspect of contemporary intensive care of the critically ill patient. The potential problems associated with invasive monitoring fall into two general categories: those related to technical pitfalls and those related to patient complications. An awareness of these problems combined with technical expertise and an understanding of cardiovascular physiology can minimize complications and make hemodynamic monitoring a safe and useful procedure. La surveillance hemodynamique est un aspect important des soins intensifs actuels des patients gravement malades. Les problemes potentiels associes aux techniques envahissantes de surveillance se classent en deux categories generales: ceux qui sont relies aux embflches techniques et ceux qui sont relies aux complications du patient. Une connaissance de ces problemes associee a une expertise technique et a une comprehension de Ia physiologie cardiovasculaire peut minimiser les complications et faire de Ia surveillance hemodynamique une procedure sOre et utile.

Invasive hemodynamic monitoring has become an important aspect of modern intensive care.1'2 The techniques involved are relatively safe and easy in experienced hands. However, there are potential problems, which can be classified as * Director, coronary care unit, Toronto General Hospital and assistant professor of medicine, University of Toronto tOntario Heart Foundation research fellow in cardiology, Toronto General Hospital Reprint requests to: Dr. Ronald S. Baigrie, Toronto General Hospital, 101 College St., CW 1-104, Toronto, Ont. M5G 1L7

technical sources of error and patient-related complications; it is to these two areas that this paper is addressed. Technical sources of error Equipment failure There is always the possibility of failure of the technical equipment required for hemodynamic monitoring. This unfortunate occurrence is not only a source of frustration for personnel but also a potential hazard to the patient. It is difficult to justify the insertion of indwelling catheters when the time, effort and expense are wasted because of ma-

chine breakdown. There are a number of ways to minimize equipment failure: (a) always check all electrical systems for malfunction immediately before inserting catheters; (b) have medical engineering personnel carry out frequent preventive maintenance servicing on the equipment; and (c) either keep back-up equipment on hand or ensure that the supplier can quickly service or replace malfunctioning parts. It is important to be sure that the commercial product that is initially purchased is reliable, well recommended and supported by a service contract and personnel who can react in a reasonable time. Newer monitoring systems have a modular design of amplifiers and preamplifiers that allows for quick replacement of nonfunctioning modules. Obviously monitoring equipment must be carefully treated and abusive handling avoided. This may be achieved by staff education programs and in-service courses given by the manufacturer's sales representatives at the time of installation and periodically thereafter. Much of the apparent machine malfunction that occurs is due to the attempts of untrained personnel to calibrate or ad-

CMA JOURNAL/OCTOBER 6, 1979/VOL. 121 885

just the system. Anyone using the equipment should be familiar with it and conversant with simple testing procedures. Responsibility for equipment care must be taken by a physician, nurse, technician or biomedical engineering group, as found in larger hospitals. It is recommended that all transducer connectors, cables, on-off switches as well as oscilloscopes and chart recorders be periodically tested for integrity and function. There is now a great variety of systems available for intravascular pressure monitoring. Each has a closed fluid system that eventually interacts with a pressure transducer that converts the mechanical signal to an electrical one. The electrical system will be damped if the fluidfilled component contains air bubbles, which collect in the connecting tubing, the dome of the pressure transducer or the catheter. Following calibration all fluid-filled systems should be flushed to clear from the pressure tubing any blood that may have accumulated during this procedure. By tightening all connectors and making sure that all stopcocks are appropriately set, one can minimize leakage and subsequent signal damping and catheter clotting. If there is any doubt about the electronic calibration a mechanical check can be done by introducing an aneroid manometer into the system. Electrical interference should be assessed promptly by the electrical department of the institution. Inaccurate balancing and calibration The recording of intravascular pressures requires that they be re-

lated to zero atmosphere. With the information. The right side of the patient supine the zero reference figure shows the high-fidelity preslevel should be the midpoint of sure wave form achievable once the right atrium, which is arbitrarily damping is corrected. Fig. 2 is an taken as either the middle of the example of a factitious pressure chest or a point 5 cm perpendicu- curve obtained by overinflation of larly below the sternal angle. It is the balloon on a Swan-Ganz imperative that all subsequent read- catheter; it implies either excesings be made at the same point. sive air (more than 1.5 ml) in the This is particuarly important in balloon or peripheral positioning measuring right heart and mean pul- of the catheter tip such that if a monary capillary wedge pressure normal inflation volume is used for (PCW) since right heart pressures arteriolar occlusion it may be excesare at a lower absolute value than sive. The excessive balloon inflation left heart pressures. An alteration may also cause pulmonary artery of 1 cm above or below the zero trauma and can be avoided by obreference level produces a change serving the pressure curve and the of 1.36 mm Hg in the recorded resistance to balloon inflation. Figs. intravascular pressures. This is a 1 and 2 are obvious examples of very common and avoidable source how misleading data, if not interof error. preted properly, can lead to inappropriate therapy and complications Problems of data collection and for the patient. Potent newer vasointerpretation active drugs can cause rapid and Two important sources of error profound changes in hemodynain the collection of data from hemo- mics. An optimal pressure wavedynamic monitoring are the col- form display allows immediate delection of inaccurate data and the tection of unexpected hemodynamic misinterpretation of appropriately changes. measured information. An imporPressure wave-form signal damptant prerequisite of optimal hemo- ing may be caused by air bubbles dynamic monitoring is an under- in the system, clotting at the cathstanding of fundamental hemody- eter tip, low signal sensitivity, loose namic principles and the meaning connections (stopcocks and pressure of pathophysiologic alterations, as tubing), catheter tip impingement on discussed elsewhere in the sympo- the vessel wall, excessive or asymsium. metric balloon inflation and periThe problem of misleading data pheral pulmonary arterial placeis critical and raises the issue of ment of a Swan-Ganz catheter. wave form interpretation. Space does not allow for an exhaustive Patient-related complications expos6 of this issue, but two examples will be cited. In Fig. 1 it Problems related to techniques of can be seen that overdamping of an catheter insertion arterial pressure curve could lead These complications are related to misinterpretation of physiological to the particular technique and

FIG. 1-Systemic arterial pressure wave form. With severe damping there is distortion of the analogue signaL After partial correction moderate damping remains. Complete correction of excess damping is depicted by the high-fidelity tracing. 886 CMA JOURNAL/OCTOBER 6, 1979/VOL. 121

catheter used and the anatomic site that is chosen. For the purposes of this discussion they will be divided into complications related to systemic arterial and pulmonary artery catheterization techniques. Systemic arterial catheterization: Intra-arterial pressure may be satisfactorily determined by cannulation of a central or a peripheral artery. Catheterization of major central arteries is generally restricted to the catheterization laboratory. In the intensive care setting intra-arterial monitoring is usually accomplished by cannulation of the radial, dorsalis pedis, femoral or brachial artery. Arterial cannulation not only allows pressure monitoring but also permits sampling of arterial blood, thus avoiding repeated arterial puncture. When possible, it is advisable to ensure that adequate collateral circulation exists when arterial cannulation is performed. For example, Allen's test3 is a useful bedside maneuver for assessing the adequacy of the collateral circulation to the hand. The hand is made ischemic and the palm is subsequently blanched by firm compression on the radial and ulnar arteries. If release of the ulnar artery is accompanied by suffusion of the hand within 5 seconds, a well developed collateral circulation exists. Since radial arterial cannulation is the most common method of intravascular systemic arterial pressure monitoring, it will be described

in detail.4'5 To avoid obscuration of the radial pulse, only a small amount of local anesthetic is administered, by an aseptic technique. The nondominant hand is preferred. The skin is then punctured with a no. 18 hypodermic needle to promote passage of the cannula and reduce the risk of stylet occlusion by skin fragments. With the artery stabilized by hyperextension of the wrist, a flexible cannula with a stylet (for example, a 5-cm Deseret Angiocath®, 20 GA [Deseret Pharmaceutical Co., Sandy, Utah]) is introduced at an angle of approximately 300 and advanced to the artery. Successful entry is evident when the stylet chamber fills with bright red blood. The stylet and cannula are advanced a further 2 mm to ensure that the cannula as well as the stylet are within the artery, as evidenced by the fact that blood continues to fill the system. The stylet is then stabilized and the cannula should advance effortlessly over the stylet into the lumen of the vessel. Significant resistance usually indicates that the cannula is not in the lumen and necessitates slight withdrawal or complete repositioning. The stylet is then removed and a good position is confirmed by vigorous pulsation of blood from the cannula. The pressure monitoring system is connected and the system flushed. The patency of the artery and function of the pressure measurement system are judged by the presence of an appropriate un-

damped wave form on the display apparatus. The cannula is then firmly secured and all connections are tightened to avoid leakage. The adequacy of the distal blood flow to the hand is reassessed on completion of the procedure. If percutaneous puncture is unsuccessful or technically difficult, radial artery cannulation may be achieved by surgical exposure and direct puncture of the vessel. Continuous flushing with a heparinized solution provided by an Intraflo® device (Sorensen Research Company, Salt Lake City, Utah) is desirable to ensure continued patency.8 Many factors can lead to complications of arterial catheterization: the use of large tapered catheters, prolonged cannulation, traumatic insertion or removal, insecure fixation, frequent manipulation, poor or absent ulnar collateral flow and infrequent observation. Specific complications seen with arterial cannulation include thrombotic occlusion,7'8 hemorrhage, hematoma,8 local tenderness,9 distal ischemia, vasospasm,1' infection,8'11 aneurysm, Osler's node formation,lz peripheral embolism,5 skin necrosis and cerebral embolism.13 Distal emboli, usually clotted blood or air, may be avoided by withdrawing the blood prior to flushing when a clot is suspected and maintaining the system free of bubbles. Arterial damage is best avoided by atraumatic insertion and attentive catheter care. Distal placement of the stop-

FIG. 2-."Overwedging". From left to right: phasic puim onary capillary wedge pressure (PCW) wave form, mean PCW wave form, mean PCW, calibration markers, phasic PCW, overwedged distortion of mean PCW by excessive balloon inflation, corrected PCW and phasic PCW. Overwedging can lead to pulmonary arterial complications. CMA JOURNAL/OCTOBER 6, 1979/VOL. 121

887

cock connecting the arterial catheter to the pressure tubing permits atraumatic arterial blood sampling and flushing. Obviously infection is best avoided by treating the catheter insertion procedure like any other surgical procedure, using sterile technique (gloves, mask, cap and gown) and a prophylactic antibiotic spray or ointment.14 As well, catheter care protocols are suggested to ensure periodic cleaning and redressing, which allows inspection (see appendix). The best way to assess the functional integrity of the system is to observe the oscilloscope for an undamped arterial pressure signal. Firm but flexible catheter fixation is required, and this is particularly important in uncooperative or stuporous patients. If there is any question that the hand is ischemic, as suggested by pallor, cyanosis or pain, the catheter should be removed and another site used. The following are ways to avoid complications of arterial cannulation: * Perform Allen's or Doppler's test. * Insert and maintain the catheter under sterile conditions. * Avoid excessive arterial trauma. * Maintain a continuous flush system free of air. * Don't flush - aspirate! * Change site if distal ischemia is present. * Observe continuous pressure wave-form display. * Inspect and dress frequently. * Ensure stability of catheter and site. Pulmonary artery catheterization: Bedside monitoring of pulmonary artery pressure has been facilitated by the development of the SwanGanz catheter,15 which permits catheterization of the pulmonary artery by the use of the flotation principle and thus usually eliminates the need for fluoroscopy. The flexible shaft of the catheter and the inflated balloon protecting the catheter tip reduce mechanical stimulation of the endocardium, thereby leading to a minimal frequency of arrhythmia. With correct positioning the phasic pulmonary artery pressures are continuously monitored, and intermittent determination of the PCW is permitted by balloon inflation. The multilu-

men catheter has other features, including electrodes for cardiac pacing and a thermistor for measurement of the cardiac output by thermodilution. Both central and peripheral veins are available for catheter introduction. In general, central veins are cannulated by a modification of the percutaneous Seldinger technique,16 while peripheral veins, such as the commonly used antecubital vessels, are approached by surgical cutdown. The relative advantages and disadvantages of using the various sites of access are briefly summarized in Table I. Factors including operator experience, the local pattern of practice and the particular patient also influence the site of vascular access. Certain precautions should be taken when attempting pulmonary artery catheterization. Continuous electrocardiographic monitoring is essential because of the small but definite risk of significant arrhythmia. Adjustment of the volume control of the cardiac monitor provides the operator with both audible and visual clues to the presence of cardiac dysrhythmia. A defibrillator should be in the room and ready to use. Pressure transducers need adequate warm-up time to establish electrical stability and should be zeroed and calibrated after this has occurred. All air bubbles should be excluded from the pressure monitoring fluid-filled line to per-

mit immediate pressure wave-form displays of high fidelity when catheters are inserted. The transducer should be at the level of the middle of the right atrium - that is, the midaxillary line in the fourth intercostal space. In the hypotensive or unstable patient it is preferable that arterial cannulation precede catheterization of the pulmonary artery, thus allowing detection and treatment of important blood pressure changes that may occur during right heart catheterization. Since surgical cutdown on the antecubital vein is a commonly used peripheral venous technique it will be described in detail.17 The median basilic vein is preferred and is entered approximately 2 cm above the skin crease of the elbow. This vein offers ready access to the axillary vein and to the superior vena cava. Although either arm can be used, the left is more convenient when arterial cannulation is also to be done, and its use takes advantage of the natural curve of the catheter. Catheterization is a surgical procedure and should be carried out with adequate sterilizing and draping of the surgical site. Under local anesthetic an incision 1 to 2 cm long is made in the antecubital fossa over the median basilic vein, which is then isolated by blunt dissection. The vessel is controlled proximally and distally by absorbable suture in the standard fashion. Prior to venotomy the catheter is flushed

Table I-Comparison of vascular access routes for pulmonary artery catheterization Vein Antecubital17

Advantages Safest method Best if patient receiving anticoagulant or bleeding Patient need not be supine at time of catheter insertion

Disadvantages Wound infection Phlebitis, sterile or septic Venospasm Difficulty entering intrathoraci c vein Spontaneous wedging Limited reuse of vein

Internal jugular'819

Large central vein Constant anatomy Short, direct route to right side of heart Stable catheter position Best central technique in patient on ventilator

Local hematoma Carotid puncture Thoracic duct injury on left Pneumothorax

Subclavian2021

As for intern.I jugular vein

Pneumothorax Hemothorax Subclavian arterial puncture Thoracic duct injury on left

Femoral'7

Easy access

Not practical bedside technique Risk of infection Risk of thromboembolism Fluoroscopy required

888 CMA JOURNAL/OCTOBER 6, 1979/VOL. 121

and wiped with sterile saline. Balloon integrity is assessed by inflating the balloon for 1 minute under sterile water or saline. Venotomy is performed by means of a transverse scissor cut. The catheter is inserted quickly and smoothly, and passed to the superior vena cava, with the 10-cm-length indicators on the catheter shaft used as a guide. The catheter tip will usually lie in the superior vena cava approximately 40 cm from the right antecubital fossa and 50 cm from the left. The distal lumen of the catheter is aspirated, flushed and attached to the pressure monitoring system. The characteristic venous wave form and its variation during inspiration and coughing confirm the intrathoracic position. The balloon is inflated and the catheter smoothly advanced; catheter passage should be effortless. In succession the right atrial, right ventricular and pulmonary arterial pressures are measured. The PCW should be obtain. able only with full balloon inflation (to 1 or 1.5 ml). A thorough knowledge of the normal pressure wave forms for the right heart is clearly necessary, and a typical example is illustrated in Fig. 3. The catheter tip uncommonly needs to be advanced more than 15 or 20 cm from the right atrium to the proper position in the pulmonary artery. The criteria for recognition of the PCW are an atrial pressure wave form, a pressure that is less than the mean pulmonary artery pressure (PAP) and arterialization of aspirated blood. If more than the usual amount of catheter is required to achieve the wave form appropriate for that length, intravascular looping or knotting should be suspected.

Once a satisfactory position is achieved the catheter is secured in the vein, the skin incision closed and a suitable dressing applied. An external catheter may be secured by being taped to the arm. The amount of catheter residing in situ should be recorded and the catheter position confirmed by chest roentgenography or fluoroscopy. Attention to this detail will reduce the likelihood of subsequent spontaneous wedging due to peripheral migration of the catheter tip, which is promoted by blood flow and catheter shaft softening. Withdrawal of the catheter from the right heart should be performed quickly, with the balloon deflated. Following each inflation the balloon should be allowed to deflate passively, as this provides evidence of balloon integrity and avoids trauma to the latex secondary to syringe aspiration of the air. The percutaneous catheter insertion technique, as practised in the internal jugular, subclavian and femoral veins, is performed as follows: Once the vein is selected, the overlying skin and subcutaneous tissue are anesthetized. A stab wound is made in the skin with a scalpel blade to facilitate passage of the catheter. The vein may then be punctured with a 5- or 1 0-ml syringe filled with flush solution attached to either a no. 16 needle or a standard 5-cm-long Teflon® (DuPont, Parkersburg, West Virginia) cannula and needle. Once blood is freely aspirated from the vein the syringe is removed and a guidewire inserted through the needle. If the standard Teflon® cannula needle is used, the central needle stylet is removed prior to passage of the guidewire. With the

guidewire inside the vein the needle or cannula is removed over the guidewire and a dilator and sheath are advanced over the guidewire into the vein. The guidewire is subsequently removed with the dilator. Caution should be exercised to maintain control of the extravascular portion of the guidewire at all times. It is wise to ensure that the catheter will advance through the sheath prior to its insertion. The sheath should be one French size larger than the catheter shaft in order to accommodate the slightly greater diameter created by the balloon at the tip of the catheter. The catheter is passed through the sheath into the large central vein. It is important to keep the sheath covered just prior to catheter insertion to avoid air embolism, particularly with the internal jugular or the subclavian site. This can happen if the venous pressure is low or if the intrathoracic pressure is lowered dramatically by inspiration, and may be avoided by having the patient keep his or her head down. The catheter is then passed through the sheath and advanced to the pulmonary artery with the use of pressure monitoring. When the internal jugular or subclavian vein is used the right atrium is usually reached with 15 cm or less of catheter and, following balloon inflation, satisfactory catheter placement in the pulmonary artery is achieved with approximately 40 to 50 cm of catheter. When the appropriate position is obtained, the sheath is withdrawn, the shaft of the catheter secured with sutures and a suitable dressing applied. Reported complications from Swan-Ganz catheterization include cardiac arrest,22 failure to obtain the

FIG. 3-Pressure wave forms encountered during right heart catheterization using a Swan-Ganz catheter. CMA JOURNAL/OCTOBER 6, 1979/VOL. 121 889

PAP or the PCW,""' arrhyth"'i catheter displacement,16 pulmonary infarction27 (F. Hagemeijer: personal communication, 1979), perforation of pulmonary artery,u infection, pulmonary artery thrombosis,29 air embolism, endocarditis,'." catheter knotting,". eccentric balloon inflation,38 balloon rupture23'28 and avulsion of the tricuspid apparatus." Local complications, which include inflammation, infection, phlebitis, pain and swelling, likely relate to insertion technique and the consequences of a foreign body in situ. Complications are less frequent when a high level of expertise is frequently exercised. Cardiac arrest rarely occurs as a complication of this technique. Failure to obtain the PCW is more frequent than failure to obtain the PAP.12 These failures are less frequent as expertise increases. Arrhythmia is common during the passage of the catheter through the right atrium and ventricle."""' To minimize the chances of ventricular arrhythmia one should never deflate the catheter balloon during forward passage through the ventricle. Coiling of the catheter in the right ventricle may also lead to ventricular arrhythmia. If arrhythmia occurs spontaneously during continuous monitoring the catheter may be the cause; its position must then be verified by pressure monitoring and fluoroscopy or chest roentgenography. Venospasm is a potential problem with the antecubital vein cutdown technique and generally occurs if catheter insertion is prolonged or painful. Methods to relieve spasm include* the application of local anesthetic to the catheter surface or intravenous administration of anesthetic, mechanical force, stiffening the catheter either by cooling or with a guidewire, sublingual administration of nitroglycerin and sedation of the patient. Removing the catheter and allowing the vein to relax often reverses spasm. Another impediment to catheter placement is tortuosity of the axillary or the subelavian vein; if difficulty is encountered at this level it may be overcome with the use of a fluoroscopy unit. Although inability to position and maintain the catheter in the pulmonary artery occurs infrequently, there are

several other conditions that may make the procedure difficult, including tricuspid regurgitation, dilation of the right atrium or right ventricle and severe pulmonary hypertension. Pulmonary artery trauma, thrombosis, pulmonary infarction and pulmonary artery rupture have been reported.27-29 These complications are almost always preventable. The balloon should never be inflated when the catheter is already recording a PCW. Persistent recording of the PCW indicates the need to withdraw the catheter. Hagemeijer (personal communication, 1979) reported a 10% frequency of pulmonary infiltration, presumably secondary to pulmonary artery occlusion, in the first 200 patients undergoing Swan-Ganz catheterization; the rate fell to 5% in the second 200 patients. Both marantic and septic endocarditis may occur; marantic endocarditis is usually seen in the critically ill patient in whom catheterization is prolonged.'0-'2 Eccentric balloon inflation'6 and balloon rupture""' may occur. To avoid rupture one should never inflate the balloon beyond the manufacturer's specifications. Rupture can be suspected when injected air is not recoverable and can be confirmed by the inability to recover 1 ml of injected saline. Catheter knotting and malposition are readily detected by chest roentgenography with a portable unit or by fluoroscopy. Catheter knotting is dangerous and generally occurs during overzealous, rapid insertion when there is inattention to the pressures recorded at specific catheter lengths. The length of catheter required to reach the right atrium, right ventricle and pulmonary artery will vary according to the site of insertion. The internal jugular and subclavian approaches require less catheter in situ, whereas more catheter is required to reach the pulmonary artery from the antecubital or femoral vein. A convenient way to estimate the amount of catheter to be inserted is to place the catheter on the sterile drape over the patient in the expected position it will assume at the time of insertion. The catheter should be easily removable; if resistance is met, catheter knotting should be suspected and confirmed by fluoroscopy. Occasionally

890 CMA JOURNAL/OCTOBER 6, 1979/VOL. 121

thoracotomy is required because of knotting, but there are other techniques of unknotting these catheters.34 Each catheter should be inspected for integrity at the time of removal, and if sepsis is suspected the distal few centimetres of catheter and the site of insertion should be swabbed for culture. It is unusual for a catheter to become severed and the distal portion to be lost in situ, but a technique for catheter fragment retrieval has been described.22 Occasionally one of the proximal fluid channels is broken; a technique for catheter repair has been suggested.'7 Pulmonary artery catheters yield high-fidelity pressure wave forms that should be continuously displayed. Unless there is direct nursing observation the pressure wave form signal that is being displayed at the bedside should be available for scanning at the central nursing station. This improves the chances of early recognition of damping, wedging and disconnection between catheter and pressure transducer; thus, if pressure wave forms are not of acceptable quality the system should be inspected and a solution sought. Electrical hazards A number of potential electrical hazards exist in the intensive care unit, where there are many types of equipment. For example, a critically ill patient may be attached to any of the following: cooling blanket, respirator, ear oximeter, intra-aortic balloon pump, thermodilution cardiac output computer, arterial and pulmonary artery physiological pressure monitoring lines, electrocardiograph, rectal temperature probe and electrical infusion pump. The physiological pressure monitoring lines, thermistor wire and electrical infusion pump are connected to the patient through conductive fluids. The patient is also resting on a metal bed, perhaps with the added hazard of electrical controls. Cross-currents can form between the various electrical devices and may increase if grounding is inadequate or if there is a current leak in the equipment. Although these cross-currents are usually small (less than 100 mA) and innocuous when applied externally, if they are delivered internally via a cardiac pacemaker or a ther-

mistor they may be sufficient to generate electrical stimuli to the heart. The fewer the electrical devices at the bedside, the less the opportunity for cross-currents to occur and the lower the potential for electrical harm to the patient. Any conductive fluids spilled on the floor or on the bedsheets can ground the patient or unit personnel in contact with the patient and should be removed. Problems related to electrical hazards have been minimized by better equipment electronics (that is, by isolation circuits) as well by better understanding and surveillance by hospital engineers. However, like radiation, electricity is invisible and usually silent, and because of this it always poses a potential hazard.38'39 Conclusion This communication has reviewed the problems associated with hemodynamic monitoring. The potential complications consist of technical sources of error and complications related directly to the patient. Most are avoidable. An understanding and respect for the technology and the hemodynamic principles as well as rigid quality control by experienced staff should keep hemodynamic monitoring the safe and useful tool it has become in the management of the critically ill patient.

5. BROWN AE, SWEENEY DB, LUMLEY J: Percutaneous radial artery can-

nulation. Anaesthesia 24: 532, 1969 6. GARDNER RM, WARNER HR, TOR-

ONTO AF, et al: Catheter-flush system for continuous monitoring of central arterial pulse waveform. J Appi Physiol 29: 911, 1970 7. DOWNS JB, RACKSTEIN AD, KLEIN

EF JR, et al: Hazards of radial-artery catheterization. Anesthesiology 38: 283, 1973 8. GARDNER RM, SCHWARTZ R, WONG

HG, et al: Percutaneous indwelling radial-artery catheters for monitoring cardiovascular function. Function study of the risks of thrombosis and infection. N Engi J Med 290: 1227, 1974 9. WARD RJ, GREEN HD: Arterial puncture as a safe diagnostic aid. Surgery 57: 672, 1965 10. DALTON B, LAyER MB: Vasospasm with an indwelling radial artery

cannula. Anesthesiology 34: 194, 1971 11. STAMM WE, COLELLA JJ, ANDERSON RL, et al: Indwelling arterial catheters as a source of nosocomial bacteremia. An outbreak caused by flavobacterium species. N Engi J Med 292: 1099, 1975 12. MICHAELSON ED, WALSH RE: Osler's node - a complication of prolonged arterial cannulation. N Engi J Med 283: 472, 1970 13. LOWENSTEIN E, LITTLE JW, HING HL: Prevention of cerebral embolization from flushing radial artery cannulas. N Engi J Med 285: 1414, 1971 14. ZINNER SH, DENNY-BROWN BC,

BRAUN P, et al: Risk of infection with intravenous indwelling catheters: effect of application of antibiotic ointment. J infect Dis 120: 616, 1969 15. SWAN HJC,

We thank Dr. Paul W. Armstrong for editorial review and Mrs. Lucy Rapp for secretarial assistance. Special recognition is given to Rhonda Littner, RN, Janice Lech, RN and Pat Fitzgerald, RN for their preparation of the appendix. References 1. SWAN HJC, GANZ W: Use of balloon flotation catheters in critically ill patients. Surg Glitz North Am 55: 501, 1975 2. BUCHBINDER N, GANZ W: Hemodynamic monitoring: invasive tech-

niques. Anesthesiology 45: 146, 1976 3. ALLEN EV: Thromboangiitis obliterans: methods of diagnosis of chronic occlusive arterial lesions distal to the wrist with illustrative

cases. Am J Med Sci 178: 237, 1929 4. BARTLETT RM, MUNSTER AM: An improved technique for prolonged arterial cannulation. N Engl J Med

279: 92, 1968

GANZ W, FORRESTER

J, et al: Catheterization of the heart in man with use of a flow-directed balloon-tipped catheter. N Engi J Med 283: 447, 1970 16. SELDINGER SI: Catheter replacement of the needle in percutaneous arteriography: new technique. A cta

Radiol 39: 368, 1953 17. GROSSMAN W: Cardiac Catheterization and Angiography, Lea & Febiger, Philadelphia, 1974, p 16 18. DEFALQUE RJ: Percutaneous catheterization of the internal jugular vein. Anesth Anaig (Cleve) 53: 116, 1974 19. DAILY P0, GRIEPP RB, SHUMWAY NE: Percutaneous internal jugular vein cannulation. Arch Surg 101:

534, 1970 20. NADJMABADI MH: Subclavian approach for cardiac catheterization with balloon tipped pulmonary arterial catheter - reply. Am J Car-

did 41: 613, 1978 21. BORJA AR: Current status of infraclavicular subclavian vein catheterization. Ann Thorac Surg 13: 615, 1972

22. ALDRIDGE HE, LEE J: Transvascular removal of catheter fragments from the great vessels and heart. Can Med Assoc J 117: 1300, 1977 23. ARCHER G, COBB LA: Long term pulmonary artery pressure monitoring in the management of the critically ill. Ann Surg 180: 747, 1974 24. GEHA DG, DAVIS NJ, LAPPAS DG:

Persistent atrial arrhythmias associated with placement of a SwanGanz catheter. A nesthesiology 39: 651, 1973 25. ABERNATHY WS: Complete heart block caused by a Swan-Ganz catheter. Chest 65: 349, 1974 26. ToUSsAINT GPM, BURGESS JH, HAMPSON LG: Central venous pressure and pulmonary wedge pressure in critical surgical illness: a comparison. Arch Surg 109: 265, 1974 27. FOOTE GA, SCHABEL SI, HODGES M:

Pulmonary complications of the flow-directed balloon-tipped catheter. N Engi J Med 290: 927, 1974 28. CHUN CMH, ELLESTAD MH: Perforation of the pulmonary artery by a Swan-Ganz catheter (C). N Engi J Med 284: 1041, 1971 29. YORRA FH, OBLATH R, JAFFE H, et

al: Massive thrombosis associated with use of the Swan-Ganz catheter. Chest 65: 682, 1974 30. GREENE JF, FITZWATER JE, CLEM-

MER TP: Septic endocarditis and indwelling pulmonary artery catheters. JAMA 233: 891, 1975 31. GREENE JF, CUMMINGS KC: Aseptic thrombotic endocardial vegetations: a complication of indwelling pulmonary artery catheters. JAMA 225: 1525, 1973 32. PACE NL, HORTON W: Indwelling pulmonary artery catheters: their relationship to aseptic thrombotic endocardial vegetations. JAMA 233: 893, 1975 33. LIPP H, O'DONOGHUE K, RESNEKOV

L: Intracardiac knotting of a flowdirected balloon catheter. N Engi J Med 284: 220, 1971 34. MOND HG, CLARK DW, NESBITT SJ,

et al: Technique for unknotting an intracardiac flow-directed balloon catheter. Chest 67: 731, 1975 35. SMIm WR, GLAUSER FL, JEMISON

P: Ruptured chordae of tricuspid valve: the consequence of flowdirected Swan-Ganz catheterization. Chest 70: 790, 1976 36. SHIN B, McASLAN C, AYELLA RI:

Problems with measurement using the Swan-Ganz catheter. A nesthesiology 43: 474, 1975 37. KITCHEN

AG,

ARMSTRONG

PW:

Swan-Ganz catheter repair. Circulation 54: 163, 1976 38. WHALEN RE, STARMER CF: Electric shock hazards in clinical cardiology. Mod Concepts Cardiovasc Dis 36: 7, 1967 39. TAYLOR KW: Electrical hazards throughout the hospital. Mod Med

Can 26: 19, Sept 1971

CMA JOURNAL/OCTOBER 6, 1979/VOL. 121 891

Appendix-Trouble-shooting problems in hemodynamic monitoring Problem Incorrect calibration or zero drift

Cause Transducer membrane not level with patient's mid-chest

Prevention and treatment Relevel transducer and recalibrate.

Maintaining catheter patency

Lines under high back pressure

Use heparinized flush solution (normal saline) with 500 U of heparin per 500 ml. Mount flush solution in pressure bag at 200 to 300 mm Hg. Use Intraflo® device in series with connecting tubing and flush. Do intermittent manual flushing with Intraflo® device.

Damped or lost pressure recording (inspect immediately)

Air in transducer or tubing

Aspirate catheter and flush system free of air bubbles. Tighten all connections and flush system. Aspirate catheter and flush using 5 to 10 ml of solution in syringe Inspect catheter and tubing for kinks or bends. Improve anchorage; splint where necessary. Attempt aspiration but do not flush; catheter usually must be replaced. Open transducer by adjusting all stopcocks in system. Recalibrate and ensure proper monitor settings.

Leak in system Blood clot at distal tip of catheter Kinked tubing or catheter Fully clotted catheter (failure to flush after blood is withdrawn) Transducer not open to catheter Incorrect calibration or gain control

Bleeding From catheter or connecting tubing Leak in system Improper fixation or vessel trauma From insertion site Catheter removed accidentally Broken catheter Spontaneous aawedgingPv of SwanGanz catheter

Painful insertion site

Hematoma after catheter removal Cold, painful, ischemic hand (radial a.tery cannulation) Balloon rupture (Swan-Ganz)

Tighten all connections and flush system. Inspect insertion site. Correct fixation and apply local pressure until bleeding stops. Advise doctor of this problem. Apply local pressure to insertion site and advise Uncooperative or disoriented patient doctor. If catheter is reinserted, ensure adequate fixation. Advise doctor to repair or replace.37 Usually due to trauma Balloon left inflated Staff must recognize difference between pulmonary artery and pulmonary capillary wedge pressure tracings. Distal migration of catheter Deep breathing, coughing or positional change by patient may dislodge the catheter; if not, advise doctor to reposition catheter. Observe chest roentgenogram for pulmonary infiltrates. Local inflammation or infection Inspect insertion site and take swab for culture. Ensure insertion and removal by aseptic technique. Inspect insertion site daily and replace topical antibiotic. If pain is excessive advise doctor regarding Excessive motion due to poor fixation changing insertion site. Local bleeding from vessel Apply local pressure until bleeding stops; if not successful advise doctor. Radial arterial thrombosis Advise doctor regarding anticoagulant therapy and catheter removal. Air injected into balloon not recoverable; unable Fill balloon with 1 ml of flush solution; if not to obtain pulmonary capillary wedge pressure recoverable, balloon is ruptured and should no longer be filled with air.

Urinary temperature and factitious fever

The differential diagnosis of fever of unknown origin sonietimes includes factitious, or spurious, fever. Patients may be quite ingenious at "cooking" the body temperature, and the diagnosis of factitious fever may be difficult to make. Checking the temperature of freshly voided urine may be the solution. Urinary temperatures are consistently within 1 to 1 .50C of simultaneously measured oral temperatures. By meas-

892 CMA JOURNAL/OCTOBER 6, 1979/VOL. 121

uring oral and urinary temperatures in healthy volunteers and patients with febrile illnesses, it has been found that a urinary temperature below the 99% confidence limit for the recorded oral temperature is diagnostic of factitious fever. Moral: modern medical Miinchausens must move more meticulously; medics may mnaster Machiavellian malingerers. U

Hemodynamic monitoring: catheter insertion techniques, complications and trouble-shooting.

true when these devices penetrate the electrical barrier provided by the skin and reside within the heart. Therefore, all electrical devices connected...
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