- Recent randomized trials found that use of a pulmonary artery catheter (PAC) did not influence the mortality of high-risk surgical patients or critically ill patients with shock or acute respiratory distress syndrome (ARDS).
- Insertion of a PAC is associated with a low incidence of serious complications. Of potentially greater risk to the patient than insertional complications are errors in recording and interpreting hemodynamic data that lead to faulty clinical decisions. Several studies have shown that there are serious deficiencies in the understanding of basic aspects of hemodynamic monitoring among physicians and nurses who use the PAC.
- Incomplete wedging can lead to marked overestimation of the actual pulmonary artery wedge pressure (Ppw) and always should be suspected when the measured Ppw exceeds the pulmonary artery diastolic pressure (Ppad). However, with pulmonary hypertension, incomplete wedging may be present despite a positive Ppad–Ppw gradient and should be suspected when the latter markedly narrows in comparison with previous values.
- Careful inspection of the PAC waveforms may be helpful in the diagnosis of underlying cardiac disorders: Acute mitral regurgitation results in prominent v waves in the Ppw tracing, pericardial tamponade is characterized by equalization of the Ppw and right atrial pressure (Pra) and by blunting of the y descent in the atrial waveform, tricuspid regurgitation often leads to a broad cv wave and a prominent y descent, and both constrictive pericarditis and restrictive cardiomyopathy result in prominence of both the x and y descents in the atrial waveform.
- Over the range of values most often seen in the ICU, neither the Pra nor the Ppw provides a reliable indicator of the adequacy of preload and of fluid responsiveness. However, the change in Pra with a spontaneous breath may be a useful indicator of fluid responsiveness in that failure of the Pra to fall with inspiration predicts that the patient is unlikely to benefit from a fluid challenge.
- Positive end-expiratory pressure (PEEP) causes the measured Ppw to overestimate transmural left atrial pressure; the effect of PEEP on transmural pressure can be quantified by calculating the percentage of alveolar pressure that is transmitted to the pleural space during a positive-pressure breath. Active expiration also causes the measured Ppw to overestimate transmural pressure and usually results in much greater errors than does applied PEEP.
- Thermodilution cardiac output (Q̇t) can be measured by the intermittent bolus method or continuously with a modified catheter. Several noninvasive and minimally invasive methods of measuring (Q̇t) are also available.
- Venous oxygen saturation in the pulmonary artery (SvO2) or superior vena cava (ScvO2) serves as a global indicator of the adequacy of O2 delivery relative to tissue O2 demands.
Although the pulmonary artery catheter (PAC) has been in use for more than 30 years,1 its value in management of critically ill patients remains controversial. Different studies have concluded that use of the PAC is associated with increased mortality,2,3 has no effect on mortality,4,5 or decreases major morbidity.6,7 Several prospective, randomized studies have been initiated within the last few years in an effort to better define the impact of the PAC on patient outcome.8 Three trials have been completed, and none found an impact of the PAC on mortality.9–11 The appropriateness of these trials has been questioned,8,12,13 and it has been suggested that efforts instead should be directed toward improvement of the standard of practice through intensive educational efforts, institution of more stringent accreditation policies, and evaluation of newer monitoring techniques before proceeding with expensive and time-consuming randomized clinical trials.8,12,13 The latter view is based in part on evidence that ICU nurses and physicians who use the PAC may have significant deficiencies in knowledge about some of the most fundamental aspects of hemodynamic monitoring,14,15 raising concern that the value of the PAC may be difficult to assess if data are not collected and interpreted optimally.16
We believe that carefully designed prospective clinical trials may provide some guidance regarding appropriate use of the PA catheter but are unlikely to clarify with certainty whether an individual patient who is critically ill and hemodynamically unstable will benefit from the information available from a PAC. At least for the time being, ICU physicians should continue to assess the benefits and risks of catheterization on a case-by-case basis, including in the decision analysis the applicability of alternative, less invasive methods of hemodynamic assessment.17,18 We share the view that the PAC is an “occasionally useful tool” that can be of value in guiding therapy of selected critically ill patients, especially when empirical therapeutic trials have proven unsuccessful or are considered hazardous.19 Implicit in this view, however, is the understanding that hemodynamic data must be collected accurately by ICU nurses and must be interpreted by physicians who are knowledgeable about cardiopulmonary pathophysiology. Faulty clinical decisions based on inaccurate or misinterpreted data may be a greater risk to the patient than the procedure per se. This chapter reviews clinical use of the PAC in the ICU, with particular emphasis on principles of data acquisition and interpretation and on the practical application of PAC-derived data in guiding therapy. Where appropriate, comparisons between the PAC and alternative methods of hemodynamic assessment will be discussed.
There are no absolute indications for PA catheterization. However, a PAC sometimes may aid in the diagnosis and management of a number of common clinical conditions (Table 13-1). These include cardiogenic and distributive shock, severe acute respiratory distress syndrome (ARDS), pulmonary edema of uncertain etiology, oliguric renal failure, perplexing lactic acidosis, and unexplained pulmonary hypertension. Preoperative insertion of a PAC also has been advocated for patients undergoing cardiac surgery and for high-risk patients undergoing major noncardiac operations. However, one large prospective study found no benefit to routine placement of a PAC before cardiac surgery and concluded that ...