Cardiovascular effects of anesthetic induction with ketamine. 
Anesthetic induction with ketamine has been reported to maintain or improve cardiovascular performance in severely ill patients.  Using invasive cardiovascular monitoring, we studied physiologic responses to a single dose of ketamine in 12 critically ill patients.  Six patient demonstrated decreases in ventricular contractility, and four had decreases in cardiac output.  Mean arterial blood pressure decreased in four patients.  Pulmonary venous admixture increased in four of six patients, while oxygen consumption decreased in eight of 11 patients.  Thus, a single dose of ketamine produced decreases in cardiac and pulmonary performance and in peripheral oxygen transport in this group of patients.  It is proposed that in severely ill patients, preoperative stress may alter the usual physiologic responses to ketamine administration, and adverse effects may predominate.  Ketamine, therefore, should be used with caution for induction of anesthesia in critically ill and in acutely traumatized patients until additional studies and further information on cardiovascular responses to ketamine are available.