Blood pressure, not cardiac output, determines blood loss during induced hypotension.

Cardiac output characteristically decreases during trimethaphan infusion but is well maintained or increased during sodium nitroprusside infusion. We postulated that at similar levels of mean arterial pressure, sodium nitroprusside might be associated with greater blood loss than trimethaphan due to the increase in cardiac output. We studied 20 young healthy patients scheduled for bilateral sagittal osteotomies of the mandible. Ten subjects received trimethaphan and 10 subjects received sodium nitroprusside. Using halothane (0.8% to 1%) and nitrous oxide (60%) for maintenance of anesthesia, trimethaphan or sodium nitroprusside was infused to maintain mean arterial pressure between 55 to 60 torr. Cardiac output was measured in five subjects in each group. Heart rate and cardiac output increased significantly and total peripheral resistance decreased significantly during sodium nitroprusside infusion when compared to trimethaphan infusion. There were no significant differences in duration of hypotension or in blood loss. We conclude that operative blood loss during induced hypotension is determined by mean arterial pressure, not cardiac output.

Induction of general anesthesia with diazepam or thiopental: a comparison of the cardiorespiratory effects.

Detailed cardiorespiratory studies were performed in 10 volunteers in whom general anesthesia was induced with thiopental 3 mg/kg and diazepam 0.4 mg/kg.Minimal changes in blood pressure were noted with both agents. Depression of total peripheral resistance lasted in excess of 20 minutes with diazepam but had returned to control levels with thiopental, elevations in cardiac rate and output were most evident and lasted longer with diazepam. In the healthy volunteer induction of anesthesia with diazepam causes alterations in cardiovascular parameters which are more profound than with thiopental. The data presented is in contrast to that obtained when patients with cariovascular disease are studied.With diazepam, considerable individual variation and long recovery times were confirmed.Following extensive clinical use, a detailed study demonstrated minimal cardiovascular depression following intravenous induction of sedation with diazepam, in patients who had prior cardiovascular disease. Subsequent studies suggested that diazepam would be a more suitable alternative for induction of general anesthesia in patients with cardiovascular disease. This was confirmed by Ikram and Rubin. It has been used extensively for sedative techniques in dentistry, and therefore it was logical to extend this concept to the induction of general anesthesia by intravenous diazepam. It was decided to evaluate the use of intravenous diazepam for induction of general anesthesia and to compare the detailed cardiovascular and respiratory effects of this drug with thiopental.

Cardiorespiratory effects of outpatient anesthesia for oral surgery: trichloroethylene-halothane.

The cardiorespiratory effects of trichloroethylene supplementation of nitrous oxide-oxygen anesthesia, with simultaneous use of halothane at induction as needed, were studied in outpatient oral surgery patients undergoing dental extractions under general anesthesia. The technique produced no deleterious cardiovascular effects that could be attributed to the combined use of these agents. Elevations of blood pressure, stroke volume, and peripheral resistance indicated light anesthesia. The versatility of halothane combined with the absence of nephrotoxic and hepatotoxic breakdown products of trichloroethylene provides a satisfactory technique for outpatient oral surgery. The agents appear pharmacologically complimentary in that halothane lacks analgesic properties and postoperative shivering occurs, while induction with trichloroethylene is slow and tachypnea is a problem.

Human cardiorespiratory and analgesic effects of intravenous diazepam and local anesthesia.

The only clinically detectable cardiovascular changes after intravenous diazepam administration are a moderate fall in systolic blood pressure and a rise in pulse rate. But it will produce significant cardiovascular changes, principally the lowering of total peripheral resistance and stroke volume. The drug has a long history of safety but is not totally innocuous. It is suggested that if diazepam is used in combination with methohexital, consideration should be given to the additive effects on total peripheral resistance.