Chapter 53. Pulmonary Artery (Swan-Ganz) Catheterization

The routine clinical catheterization of the pulmonary artery was made possible by the pioneering work of H.J.C. Swan and William Ganz. Together they developed the soft, balloon-tipped, flow-directed pulmonary artery catheter (PAC) that bears their names.1 Prior to the work of Swan and Ganz, pulmonary artery catheterization was performed using a stiff catheter that required fluoroscopic guidance and was associated with a high complication rate. The Swan-Ganz PAC allows reliable and continuous measurement of hemodynamic parameters to be performed safely, even in critically ill patients.2–4 While complications are uncommon, they can occur. The optimal application of the PAC, both its insertion and interpretation of the data, requires appropriate training and skill.5–7

This chapter concentrates on the technique of PAC insertion. Obtaining central venous access is a necessary prerequisite for this technique and is discussed in Chapter 49. A detailed discussion of the interpretation of the abundant variety of data that the PAC may provide is beyond the scope of this chapter.8 The interpretation of data is discussed primarily as it concerns PAC insertion and associated complications.

The PAC is advanced into the right atrium from a venous access site in the neck, chest, upper extremity, or lower extremity. The balloon near the tip of the catheter is inflated during its insertion. The balloon follows the flow of blood through the right heart—from the right atrium through the tricuspid valve into the right ventricle, then up the right ventricular outflow tract through the pulmonic valve into the pulmonary artery, and from there into a branch of the pulmonary artery (Figure 53-1).

When the PAC is correctly positioned, inflating the balloon near its tip will occlude the forward blood flow to that arterial segment (Figure 53-2). The lumen opening at the tip of the PAC will therefore measure the downstream pressure in that vessel, rather than pulmonary artery pressure. Because the pulmonary circulation has no valves, the pressure that the PAC tip measures beyond the inflated balloon is equal to the pressure in the pulmonary capillaries. This pressure is, in turn, equal to the pressures in the pulmonary veins and the left atrium. During diastole, when the mitral valve is open, this pressure is equal to the left ventricular diastolic pressure. The left ventricular end-diastolic pressure is a very important parameter because it is the best clinical indicator of preload. Thus, measurement of the pulmonary capillary wedge pressure (or pulmonary artery occlusion pressure, as it is sometimes called) provides an excellent assessment of left ventricular filling without the need to catheterize the left side of the heart.

The PAC may also be used to measure cardiac output using the thermodilution method. The tip of the PAC has a temperature-sensitive probe. When a given volume of cold saline is injected into the right atrial port of the PAC, it cools the temperature of the blood flowing past the catheter tip. If the cardiac output is high, the cold saline is mixed with and carried along by a larger flow of blood so that the temperature change detected at the PAC tip is smaller and dissipates faster. If cardiac output is low, the cold saline mixes with a smaller volume of blood and the temperature change is more apparent and slower to dissipate.

The major advantage of the PAC is that it provides accurate measurements of hemodynamic parameters such as pulmonary capillary wedge pressure and cardiac output. This is particularly useful in critically ill patients, as the clinical estimation of these parameters is frequently incorrect.9–13 The PAC may be used for diagnostic or therapeutic purposes. Diagnostically, the PAC is usually used in situations where clinical judgment alone cannot reliably determine the physiologic basis for hemodynamic instability, pulmonary edema, or reduced urine output. Therapeutically, the PAC may help to direct therapy in patients in whom noninvasive clinical parameters are insufficient guides of treatment efficacy. The most common clinical indications for the PAC in medical and surgical patients are listed in Table 53-1.

It should be noted that despite the prevalence of PAC use, few prospective studies have documented improved clinical outcomes with the PAC except in perioperative surgical patients. Retrospective studies have suggested that the use of the PAC may be associated with worse outcomes.14–17 Over the last 10 years, this question has been further studied in randomized controlled trials as a result of the retrospective data suggesting worse outcomes with the use of PAC. In all of these trials, PACs do not appear to improve survival or decrease length of stay. However, these trials also do not confirm the suggestion of worse outcomes with the use of PAC. As with any intervention, the Emergency Physician must carefully assess the potential benefits and risks in making the decision to place a PAC. There is an actual cost and potential complications associated with placement of these catheters.21–28

There are no circumstances in which PAC insertion is absolutely contraindicated. Insertion of a PAC may be relatively contraindicated in cases where the risks of obtaining vascular access (e.g., severe bleeding diathesis) or of passing the catheter (e.g., a mobile thrombus in the right heart or right-sided endocarditis) outweigh the potential benefits of obtaining the data the PAC provides.

A PAC is not indicated in situations where it will provide no diagnostic information that cannot be acquired by less invasive means. For example, while a PAC may be helpful in diagnosing or treating patients with mitral regurgitation or ventricular septal defects following myocardial infarction, echocardiography may be sufficiently diagnostic and may obviate the need for a PAC. The same can be true in cases of cardiac tamponade. The PAC may also be superfluous in situations where it will provide little or no therapeutic guidance. The insertion of a PAC is not necessary if a therapeutic trial of fluid administration restores urine output and blood pressure in a hypovolemic patient who has normal cardiac function. Other contraindications include patients with: cardiac dysrhythmias, implanted pacemakers or defibrillators, pulmonary hypertension, right-sided endocarditis, right-sided intracardiac valvular abnormalities, right-sided prosthetic heart valves, right-sided intracardiac thrombi, or severe hypotension. A PAC should not be inserted if the appropriate equipment is unavailable or if personnel experienced with the insertion and interpretation of the PAC data are not present.19,20

• Povidone iodine or chlorhexidine solution
• Sterile gloves and gown
• Face mask and cap
• Saline or dextrose solution with or without heparin (1 to 2 U/mL)
• Pressure bag with manometer
• Pressure tubing
• Pressure transducer for distal port (CVP port optional)
• Stopcocks and occlusive caps for each port of PAC
• Fluid infusion tubing for sheath sideport and for PAC ports
• PAC
• Balloon inflation syringe
• Catheter sleeve
• Sterile dressing for site
• Electrocardiogram (ECG) and pressure monitor

The materials required to place a percutaneous introducer sheath are available in commercially prepared prepackaged kits. Refer to Chapter 49 for the details regarding the placement of the introducer sheath. Note that many PACs require an 8.5 French introducer sheath. In addition, it is desirable to use an introducer sheath that allows the sterile protective sleeve over the PAC to be affixed securely to the sheath.

The PAC consists of a balloon lumen that ends in a balloon just proximal to the catheter tip, a distal lumen that opens at the end of the PAC, a lumen that opens approximately 30 cm proximal to the tip, and a thermister (Figure 53-3). Many PACs have one or more additional lumens opening proximal to the tip. Some of these lumens are designed to accommodate a cardiac pacing wire. A 3 mL syringe with a safety stop at 1.5 mL is supplied with each PAC. This syringe is used to inject air into the balloon. Distances from the tip of the PAC are indicated by linear markings on the shaft. By the standard designation, each thin line represents 5 cm increments and each thick line 10 cm increments.

Routine laboratory studies are advisable prior to PAC insertion in nonemergent circumstances. Hematologic abnormalities (e.g., severe anemia, thrombocytopenia, and coagulation system deficiencies) can increase the risk or adverse consequences of bleeding. Electrolyte derangements (e.g., hyperkalemia, hypokalemia, and hypomagnesemia) that may predispose to arrhythmias should be identified and corrected when possible.

Explain to the patient and/or their representative the risks, benefits, and complications of the procedure. Obtain informed consent for the procedure if possible. The use of mild sedation may be advantageous in some patients. Place the patient supine if possible. Continuous ECG monitoring is essential. Pulse oximetry should be routinely monitored. Arterial pressure monitoring is often desirable in patients receiving a PAC. Apply supplemental oxygen. Equipment and personnel necessary for assisting with the PAC insertion procedure and for managing potential complications should be immediately available. This should include equipment for emergency airway management and emergency cardiac pacing.

The choice of which central venous access site to use for PAC insertion must be individualized. The preferred sites are the right internal jugular vein or the left subclavian vein. The PAC tends to float into the desired position more easily from these two sites. The left internal jugular vein and the right subclavian vein are acceptable alternatives. The femoral vein may also be used. The femoral approach may be quite difficult without fluoroscopic guidance of the catheter. The external jugular veins, basilic veins, and axillary veins are additional alternatives that carry the same difficulty.

It is essential that strict sterile technique be maintained throughout the insertion procedure. The Emergency Physician and their assistant should be wearing sterile gloves, a sterile gown, a face mask, and a cap. A large sterile field is necessary, as is close attention to the long PAC, which can easily become contaminated. It is also very important to take all necessary precautions with syringe needles, scalpel blades, and suture needles to prevent a needlestick injury.

Insert a percutaneous introducer sheath into the central venous system. Refer to Chapter 49 for the complete details regarding the insertion of the sheath. If the patient already has a single-lumen or multi-lumen central venous catheter inserted, it may be exchanged for an introducer sheath. Remove any bandages and dressings on the catheter and skin access site. Thoroughly prep the catheter, skin access site, and surrounding skin with povidone iodine or chlorhexidine solution and allow it to dry. Drape a sterile field. Discontinue any infusions through the catheter. Open an introducer sheath kit. Cut any sutures securing the catheter to the skin. Insert a guidewire through the hub of the distal port and into the central venous circulation. Withdraw the catheter over the guidewire. Insert and secure the percutaneous sheath over the guidewire as described in Chapter 49.

Set up a bedside sterile table and open the PAC kit. Remove the protective sleeve. It allows later repositioning of the PAC while maintaining sterility. Place the sleeve over the catheter and slide it far back (>60 cm) from the catheter tip. Attach the balloon inflation syringe to the PAC. Inflate the balloon once to confirm the integrity of the balloon. It is a good idea to inflate the balloon in a full bowl of sterile saline and observe for air bubbles to ensure that there are no leaks or gross eccentricities. Allow the balloon to deflate passively. Deflation by aspirating air from the balloon should be avoided as it places undue stress on the balloon. Flush the PAC ports with sterile saline and attach a stopcock to each port. Attach the pressure tubing to the distal port. Flush the entire apparatus, including the PAC and the pressure monitoring system, with sterile saline to ensure that no air remains in any part of the system. Have an assistant set up, calibrate, and level the transducer. Hand the proximal end of the PAC to an assistant to attach to the ECG monitor. Finally, shake the tip of the PAC while observing the pressure waveform on the monitor to confirm that the monitoring system is operative.

Insert the PAC through the diaphragm on the introducer sheath, taking care to orient the natural curve of the catheter toward the right ventricular outflow tract. Continue to advance the PAC until it is inserted 10 to 15 cm and exits the sheath. This ensures that the balloon is not inflated within the sheath. Stop advancing the PAC. Inflate air into the balloon and lock the pressure release valve. The PAC should never be advanced through the central venous system with the balloon deflated, as this may provoke ectopy or injure the heart or other vascular structures. Conversely, the PAC should always be withdrawn with the balloon deflated.

Pay close attention to the distance markings on the PAC and to the pressure waveform on the monitor when advancing the PAC. Typical pressure waveforms are illustrated in Figure 53-4. The average distances from the different catheter insertion sites into each chamber of the heart are listed in Table 53-2. Advance the PAC into the right atrium (Figure 53-4A). Continue to advance the PAC into the right ventricle, which will be apparent by an abrupt change in the pressure waveform (Figure 53-4B). Continue to advance the PAC into the pulmonary artery outflow tract, again confirmed by a change in the pressure waveform (Figure 53-4C). Passing the PAC through the right ventricle may produce some ventricular ectopy, which is generally uncomplicated. Advance the PAC a few centimeters further to produce a wedge tracing (Figure 53-4D). Deflate the balloon. This will result in the reappearance of the pulmonary artery waveform. If the wedge tracing persists, withdraw the PAC with the balloon deflated until the pulmonary artery waveform reappears. Whenever it is unclear where the tip of the PAC is located, deflate the balloon and withdraw the PAC to a spot where the waveform is recognizable. Take notice of the distance marking. Inflate the balloon and advance the PAC until the desired tracing is obtained.

Difficulties in passing the PAC into the pulmonary artery may occur in patients with pulmonary hypertension, significant tricuspid regurgitation, or markedly dilated right heart chambers. Instruct the patient to inspire slowly and deeply to increase venous return to the right heart. This may allow the PAC to be advanced successfully. Tilting the patient's head upward and repositioning the patient on their left side may also be helpful. Fluoroscopic guidance may be necessary if repeated attempts are unsuccessful.

Pull up the protective sleeve over the catheter and secure it to the introducer sheath. It is important not to advance the PAC itself during this manipulation. Begin any infusions through the PAC. Secure the PAC, dress the access site, and document correct positioning by obtaining an anteroposterior chest radiograph. The assessment and aftercare of the skin puncture site is described in Chapter 49.

As mentioned in the introduction to this chapter, a detailed discussion of PAC data interpretation cannot be undertaken here. However, anyone who places or uses PACs in the management of critically ill patients should be familiar with the standard information provided by the PAC. The data generated by the PAC can be divided into two categories. The first set of information comprises data that are directly measured and include the right-sided heart pressures, thermodilution cardiac output, and blood gas obtained from a mixed venous sample from the distal pulmonary artery port. These data, including normal values, are listed in Table 53-3. The second set of data comprises the variables that are mathematically derived from the measured data (Tables 53-4 & 53-5). These provide information crucial to understanding cardiac and pulmonary physiology and pathology. Today, this information is routinely available on an instantaneous basis as part of computer software packages that accompany the monitoring equipment. PAC users should become familiar with both sets of information and their application in different clinical situations. The reader is advised to consult a current textbook of cardiology or critical care medicine for a more detailed description of the hemodynamic data provided by the PAC.

In addition to the complications associated with obtaining central venous access and with prolonged use of indwelling catheters (Chapter 49), complications may occur during or after the insertion of the PAC. The complications directly related to the PAC may be divided into those that are associated with catheter insertion and those associated with long-term maintenance (Table 53-6). Both sets of complications can be further divided into those problems where there has been systematic study and the incidence of complications has been published and those that have been observed and published as case reports but the actual incidence of which is unknown.

Problems with tracing quality may occur due to problems involving the catheter itself or other parts of the system. Catheter problems include positioning too distal or not distal enough, balloon rupture, or clot formation at the tip. Problems elsewhere in the system include air in the lines, loose connections, failure of the transducer, failure of the wires, or failure of the monitor. The system should be zeroed and calibrated again to confirm the accuracy of the pressure values if abnormally high or low values are obtained. Sometimes it is just not possible to obtain a good wedge tracing despite repeated attempts. In such cases, the pulmonary diastolic pressure may be used as a surrogate for the wedge.

A right bundle branch block may occur due to impact of the PAC with the right side of the septum during insertion. This is usually transient. Even if it persists for hours, it is well tolerated in most patients. However, superimposition of a right bundle branch block in the presence of a preexisting left bundle branch block leaves the patient with complete heart block. This complication can result in severe bradycardia and hemodynamic embarrassment. It is important to be prepared to institute temporary transcutaneous or transvenous pacing when placing a PAC in patients with a left bundle branch block.

Arrhythmias during insertion, most commonly premature ventricular beats, are usually due to irritation of the right ventricle. This is especially true of the outflow tract. Premature ventricular contractions are usually well tolerated unless sustained ventricular tachycardia or ventricular fibrillation occurs. Slight withdrawal and redirection of the PAC is usually adequate. Arrhythmias after insertion may be due to catheter loops in the right heart, which will be apparent on the chest radiograph and can be corrected by careful withdrawal of the PAC until the loop is removed. Arrhythmias may also occur if the PAC tip slips back into the right ventricle. In this case, the pressure tracing will show a typical right ventricular waveform. Readvancement of the PAC into the pulmonary artery should eliminate the arrhythmias.

Other potentially serious but rare complications during placement include injuries to the great vessels, trachea, lymphatic duct, vagus nerve, or phrenic nerve as well as a pneumothorax, hemothorax, hemomediastinum, and cardiac perforation. On occasion, the PAC can become knotted intravascularly or within the heart during placement. This requires an Interventional Radiologist to unknot it or surgical removal if this fails.

The most serious complications related to long-term maintenance of the PAC are pulmonary artery rupture, pulmonary artery infarction, and catheter infection. Pulmonary artery rupture is usually the result of the catheter becoming overwedged and/or the balloon over-inflated. Pulmonary infarction has been seen primarily in patients with mitral regurgitation or pulmonary hypertension and may be avoided if the duration of balloon inflation is kept to a minimum. Catheter infection occurs in 1% to 5% of PAC placements and can be minimized by strict sterile maintenance of the PAC as well as continually reevaluating the need for the PAC and keeping the placement time as short as possible. The majority of PACs should be used for 72 hours or less.

Since its introduction four decades ago, the PAC was initially embraced by Emergency Physicians and Critical Care Physicians for its ability to provide real time information regarding variables such as cardiac output and pulmonary capillary wedge pressure at the bedside. PAC use had become common practice. However, over the last 15 years this has come into significant question. At this point, the utility of the PAC is unclear. The PAC has not led to improved outcomes, decreased mortality, or decreased ICU length of stay. Thus, its use as common practice cannot be supported. However, there are still many clinical situations for which the use of the PAC may benefit the Emergency Physician to make crucial decisions. The PAC is a tool in the armamentarium of any clinician taking care of critically ill patients. Therefore, it is important to be well versed in the information that it provides and its application in the clinical context of the disease state that they are managing.