Cardiovascular dysfunction in multisystem organ failure: Focus on septic shock

We have reviewed some of the issues relevant to understanding the cardiovascular physiologic derangement most commonly seen with MSOF, which is septic shock. The standard pulmonary artery catheter derived hemodynamics are useful. The evolution of physiology in survivors of sepsis seems to follow a predictable pattern. Preshock ability to mobilize DO₂, VO₂, and CI is followed in the acute 24-hour decompensation phase by the ability to reduce heart rate and increase CI and peripheral vascular tone. Further information is provided by volume, rather than pressure-flow oriented monitoring. Both systolic and diastolic left ventricular dysfunction are evident early in sepsis and a uniform inadequate response to volume challenge has been documented. Survivors manifest acute reversible cardiac dilation and reduction in ejection fraction. Overall, the majority of patients who expire due to sepsis demonstrate reduced ventricular compliance, tachycardia, and refractory peripheral vasodilation resulting in persistent shock or rapidly progressive MSOF. Less than a third of mortalities are associated with hypodynamic state. Considerable information is available as to regional circulation and metabolic function. The global oxygen metabolism demonstrates pathologic dependence of oxygen consumption and oxygen delivery; this seems to hold for vital organ systems. Myocardium shows profound coronary vasodilation and shift in substrate utilization to lactate. The possibility of endogenous myocardial substrate utilization exists with unclear implications as to cardiac function or relationship to circulating levels of myocardial depressant substances. Respiratory muscle blood flow and oxygen consumption increase drastically and can be beneficially modified by standard therapeutic interventions. Vasoactive drugs have predictable effects on oxygen metabolism and regional circulations. Their selective use can beneficially affect diastolic compliance, gas exchange, renal blood flow, and the ability to provide adequate fluid resuscitation. Positive pressure ventilation, PEEP, and nutritional infusions produce predictable hemodynamic changes that are frequently not considered in the assessment of patients in septic shock.