PRO/CON: A Pulmonary Artery Catheter Should Be Routinely Used in All Patients Undergoing Cardiac Surgery

CON:

Julia Labovsky, MD
Fellow, Cardiothoracic Anesthesia
Department of Anesthesia and Critical Care
University of Chicago

Since its introduction over thirty years ago, the pulmonary artery catheter (PAC) has become a frequently utilized tool for perioperative monitoring of the cardiac surgical patient. The ability of the PAC to provide data to detect ischemia, measure cardiac output, and assess volume status potentially affords additional optimization of perioperative care. While there are few risks of placing a PAC, the benefits of a PAC remain to be seen in terms of prospective, randomized trials. In light of the lack of data to support improved outcome, the cost of placing such a monitor, and the additional risk, PACs should not be routinely used in all cardiac surgical patients.

The data derived from PAC measurements may provide benefits for the cardiac surgical patient, including potential detection of ischemia, calculation of cardiac output, and assessment of volume status. In the past, it has been suggested that an increase in pulmonary capillary wedge pressure (PCWP) or the presence of a "c" wave or a "v" wave could potentially detect ischemia as a result of changes in ventricular compliance. However, in a study by Haggmark et al, these criteria did not, in fact, reliably predict ischemia(1). Thus, an elevation in PCWP is not specific for ischemia and may occur as a result of increased afterload or decreased pulmonary compliance. If monitoring for ischemia is desired, then more sensitive and specific methods such as EKG analysis or transesophageal echocardiographic (TEE) monitoring for wall motion abnormalities should be employed.

The ability to estimate intravascular volume status by the PCWP is another purported use of the PAC. In absence of mitral valve disease, positive end-expiratory pressure, and lung paranchymal disease, the PCWP may provide a good estimate of left atrial pressure and left ventricular end-diastolic pressure, which are surrogates for left ventricular end-diastolic volume, or preload. In patients with normal left ventricular function, there is good correlation between central venous pressure (CVP) and PCWP, when following trends in intravascular volume changes, as was shown by Mangano(2). If monitoring volume status is an indication for placing a PAC, it should be reserved for patients with depressed left ventricular function (ejection fraction less than 40%).

Once central venous access is secured, the complication rate of an indwelling PAC is fairly low. During placement of a PAC, dysrhythmias are frequent, but often resolve once the catheter is advanced or withdrawn. While serious possible complications include pulmonary infarction (0.1-5.6%), pulmonary rupture (0.1-1.5%) and sepsis (0.7-11.4%), the incidence of these complications is fairly low. Deaths attributed to a PAC are estimated to be 0.02-1.5%, as assessed by the Task Force for Guidelines on Pulmonary Artery Catheterization(3).

Due to the relatively low risk of the PAC and the additional data that the PAC provided, the use of PACs in cardiac surgery became popular despite the lack of prospective, randomized trials to quantify improved outcome. In fact, Tuman(4) is a prospective study of high-risk cardiac surgical patients who received either CVP or PAC monitoring, revealed no significant difference in overall mortality, need for postoperative intra-aortic balloon pump support, postoperative myocardial infarction, renal dysfunction, or neurologic events and the length of stay in the intensive care unit (ICU) was longer in the PAC group. While this study was not randomized, and later placement of a PAC was allowed in the CVP group if it became clinically necessary, there was no significant difference in the perioperative risk factors between the two groups to suggest that patients who were selected to receive the PAC had a greater severity of illness.

The benefit of the PAC was strongly questioned in 1996, when an observational study by Connors et al(5) revealed that the PAC was associated with increased morbidity and mortality and increased utilization of resources in a population of medical and surgical ICU patients. While this was not a randomized study and thus probably contained an element of bias, it certainly raised concerns among clinicians and called for better studies on this issue.

Recently, a prospective, randomized study by Sandham et al(6) assessed the benefits of the PAC in high-risk surgical patients requiring intensive care. The patients were ASA class III or IV, having major abdominal, thoracic, vascular, or orthopedic surgery. Physiologic goals of the PAC group included optimization of oxygen-delivery index, cardiac index, PCWP, heart rate, and hematocrit. Cross-over was not permitted. In the PAC group, goal-directed therapy resulted in a greater use of inotropic agents, vasodilators, antihypertensive agents, packed red blood cells, and colloid. The investigators demonstrated no significant difference in length of hospital stay, mortality, myocardial infarction, left ventricular failure, arrhythmia, pneumonia, renal insufficiency, hepatic insufficiency, or sepsis. There was a significant difference in the incidence of pulmonary embolism, however, of 0.8% in the PAC group.

While the design and results of the above study are impressive, there remains a need for prospective, randomized trials to assess the benefit of the PAC in cardiac surgical patients. Why have these trials not been undertaken? Despite the lack of improved outcome data, placement of a PAC in cardiac surgery has become standard of care in some institutions. Once such a practice becomes routine, it is difficult to deviate from that for investigational purposes because of concerns that one of the groups may suffer a worse outcome. Also, the use of the PAC has become routine in most surgical ICUs at some institutions. Thus, clinicians supervising the ICU may not feel as comfortable as the anesthesiologist when managing a hemodynamically labile patient without a PAC. In order to execute such a change in practice, agreement on postoperative monitoring will have to be made between the intraoperative and postoperative physicians.

The use of a PAC is associated with higher costs, greater utilization of resources, and with increased risks, though of low incidence. Due to the lack of data to suggest improved outcome, the routine use of a PAC in cardiac surgery cannot be justified. Most certainly, if TEE is utilized intraoperatively by trained personnel, information from a PAC will not be required. Under these circumstances, the decision whether or not to utilize a PAC is based on whether or not it will be required in the immediate postoperative period (when TEE is discontinued). A practice of reserving the PAC for patients in which CVP will not correlate with PCWP or waiting until a clinical need develops is a better strategy until prospective, randomized studies determine whether there is benefit in cardiac surgical patients.

References

1. Haggmark S, et al: Comparison of hemodynamic, electrocardiographic, mechanical and metabolic indicators of intraoperative myocardial ischemia in vascular surgical patients with coronary artery disease. Anesthesiology 70:19-25, 1989

2. Mangano, DT: Monitoring pulmonary arterial pressure in coronary artery disease. Anesthesiology 53:364-70, 1980

3. Roizen, MR et al: Practice guidelines for pulmonary artery catheterization. Anesthesiology 78:388-94, 1993

4. Tuman KJ, et al: Effect of pulmonary artery catheterization on outcome in patients undergoing coronary artery surgery. Anesthesiology 70:199-206, 1989

5. Connors AF et al: The effectiveness of right heart catheterization in the initial care of critically ill patients. JAMA 276:889-897, 1996

6. Sandham JD, et al: A randomized, controlled trial of the use of pulmonary-artery catheters in high risk surgical patients. N Engl J Med 348:5-14, 2003.


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