Chapter 13

• 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...

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