6 - Cardiovascular Management of ARDS

Summary

Introduction

ARDS is often thought of as primarily a pulmonary disease. However, ARDS has a profound effect on the cardiovascular system, and cardiovascular management can have a profound impact on physiologic status and outcome in ARDS for several reasons. First, oxygen delivery to the whole body is a product of arterial oxygen saturation, oxygen-carrying capacity of the blood, and cardiac output. It follows that management of cardiac output and hemoglobin are just as important as achieving high arterial oxygen saturations by ventilator management. Second, ARDS is characterized by a large intrapulmonary shunt and therefore is a setting where mixed venous oxygen saturation has a direct impact on arterial oxygenation. Cardiac output, as a component of oxygen delivery and oxygen consumption, plays a key role in determining mixed venous oxygen saturation – emphasizing the importance of cardiovascular management. Third, in the early exudative phase of ARDS, a low pulmonary capillary wedge pressure can decrease the rate of edema formation and thus have an impact on oxygenation and outcome. Therefore, finding the lowest pulmonary capillary wedge pressure that gives an adequate cardiac output is a focus of cardiovascular management of ARDS.

Conversely, ventilator strategy can have a profound impact on cardiovascular function. For example, ARDS can be associated with significant pulmonary hypertension, which can be exacerbated by positive airway pressures. This effect, plus the direct transmission of high airway pressures to right atrial pressure, can significantly decrease venous return. Thus, ARDS is a pulmonary disease where cardiopulmonary interaction is exceedingly important and where cardiovascular management is fundamental to excellent care.