Effects of Low-Dose Ketamine and Thiopentone on Cardiac Performance and Myocardial Oxygen Balance in High-Risk Patients

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Abstract
Induction of anesthesia may pose a significant hazard to patients with critical cardiovascular status. Ketamine is the drug of choice for maintaining cardiovascular performance during induction of anesthesia in severely ill surgical patients. The relative changes in the hemodynamic effects of ketamine and thiopentone were compared during the first 30 min of anesthesia induction measured by thoracic impedance cardiography. Twelve adult high-risk surgical patients, ASA [American Society of Anesthesiologists] class III-IV, were induced with thiopentone and fentanyl or with infusion of ketamine. Cardiac output decreased to 69% in the thiopentone group (P < 0.05) but was hardly affected in the ketamine group. The preejection period to left ventricular time (PEPI) and the preejection period index ratio increased significantly after thiopentone (P < 0.05), while ketamine caused only minimal changes in left ventricular performance. The diastolic pressure time index to systolic pressure time index ratio decreased significantly in both groups.