The coronary circulation in human septic shock

Abstract

Reversible myocardial depression, manifested by ventricular dilatation and decreased ejection fraction, is common in human septic shock. A proposed mechanism, based on animal studies, is myocardial ischemia resulting from inadequate coronary blood flow. Coronary flow observations have not been reported for human septic shock. To determine whether myocardial depression in human septic shock is associated with reduced coronary flow, thermodilution coronary sinus catheters were placed in seven patients with septic shock for measurements of coronary flow and myocardial metabolism. Four of the seven patients developed myocardial depression. These patients had coronary flow similar to or higher than that of control subjects and similar to that of the other three patients, who did not develop myocardial depression. None of the patients had net myocardial lactate production. In general, compared with values in control subjects, the oxygen content difference (arterial minus coronary sinus) was narrowed, and the fractional extraction of arterial oxygen was diminished. This pattern of disordered coronary autoregulation is analogous to the pattern of arteriovenous shunting in other organs in patients with septic shock. The preservation of coronary flow, the net myocardial lactate extraction, and the increased availability of oxygen to the myocardium argue against global ischaemia as the cause of myocardial depression in human septic shock.