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...administered alterations cardiac output are noted. Central venous pressure (CVP) changes in the respiratory cycle also can be assessed during fluid resuscitation. The PAC additionally can be useful when weaning patients with cardiac dysfunction from mechanical ventilation. In these patients, the reduction in positive pressure leads to greater venous return and pulmonary edema occurs frequently. Using the PAC, you may be able to detect tricuspid and mitral regurgitation with large waves in the CVP and pulmonary artery occlusion pressure tracings, respectively. In patients with hepatorenal syndrome, a PAC may be needed to ensure adequate intravascular resuscitation.
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Perhaps the most common use for the right heart catheter, or the pulmonary artery catheter (PAC), in the ICU is to determine fluid status in patients with shock and cardiac failure. In shock states, adequate resuscitation and maximization of oxygen delivery are usually the goals. In heart failure, the goal may be to eliminate fluid overload and maximize cardiac performance, as measured by cardiac index (Cl). Other common uses of the PAC include differentiation of diffuse infiltrates (cardiogenic versus noncardiogenic pulmonary edema) and evaluation of renal failure (prerenal versus intrinsic failure).
The PAC also can help classify prerenal azotemia by flagging hypovolemia and relaying whether the ongin is cardiogenic, hepatorenal, or septic. Additional uses of the PAC include diagnosis of cardiac tamponade, constrictive pericarditis, and ventricular septal defect (VSD); differential diagnosis of arrhythmias (atrioventricular [AV] block, atrial flutter); and detection and treatment of right ventricular (RV) failure (RV infarct, pulmonary embolism [PE], primary pulmonary hypertension). While in the pulmonary artery occlusion pressure (PAOP) position, the PAC can aspirate blood useful in the detection of lymphangitic carcinoma, tumor emboli, or amniotic fluid embolism. (1)
The accuracy of the clinical examination in estimating cardiac output (CO) and PAOP has been poor (42% to 66%), (2-5) despite the degree of physician experience. Although data obtained from PAC recordings have prompted changes in therapy in one half to two thirds of patients, a positive impact on outcome has been difficult to demonstrate in most clinical settings.
Because the use of the PAC in the critically ill patient is controversial, a better understanding of its role as an adjunct to the history, physical examination and laboratory results, and central venous pressure (CVP) is needed, and well-designed protocols that examine PAC use and associated therapies are imperative. I think it is unlikely that the PAC will replace the history and clinical examination; the best use of the PAC may be as a diagnostic adjunct and a guide to therapy.
In part 1 of this article, which appeared in the January 2003 issue of The Journal of Critical Illness, I reviewed technical aspects of the PAC, including its insertion, complications associated with its use, transducer zeroing and leveling, signal transduction, and primary and calculated measurements. In this concluding part, I discuss the PAC in the clinical setting, including its use in ICU patients with shock, cardiac failure, and renal failure.
Shock
In shock states, CO can be classified as high, normal, or low and is associated with high, normal, or low filling pressures. Patients with reduced CO have either cardiogenic or hypovolemic shock. Cardiogenic shock may be a result of primary left ventricular (LV) failure, which can occur after a myocardial infarction (MI).
However, cardiogenic shock may be caused by diastolic dysfunction, increased afterload (aortic stenosis, hypertrophic cardiomyopathy), acute valvular dysfunction (papillary muscle rupture, acute mitral regurgitation, endocarditis), or RV failure (RV infarct, PE, acidosis, hypoxic pulmonary vasoconstriction) (Table). When the left side of the heart is failing, PAOP and right atrial pressure (RAP) are elevated; however, when the right side of the heart is falling, only RAP is elevated.
Shock resulting from decreased venous return but normal cardiac function occurs in settings of high and low RAP. (6) Elevated RAP with reduced CO may indicate either right heart failure or impeded venous return. Impediments to venous return include cardiac tamponade (equalization of diastolic pressures during PAC insertion should occur), constrictive pericarditis, tension pneumothorax, massive pleural effusions, positive pressure ventilation, positive end-expiratory...
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