Nitrous oxide-isoflurane anesthesia causes more cerebral vasodilation than an equipotent dose of isoflurane in humans

To compare the cerebral vascular and metabolic effect of an isoflurane-nitrous oxide mixture to an equipotent dose of isoflurane at 1.1 minimum alveolar anesthetic concentration (MAC), and to study the interaction between nitrous oxide and isoflurane anesthesia, we measured right middle cerebral artery blood flow velocity (V mca) and cerebral arteriovenous oxygen content difference (AVDO2) in six healthy patients during normocapnia and normothermia under the following sequence of steady-state anesthetic conditions: Condition A, 0.5 MAC of isoflurane, Condition B, 0.5 MAC of isoflurane + 0.6 MAC of N2O, Condition C, 1.1 MAC of isoflurane + 0.6 MAC of N2O, and Condition D, 1.1 MAC of isoflurane. The study entry sequence was randomized. V mca and AVDO2 during 1.1 MAC of isoflurane (Condition D) was 48 +/- 7 cm/s and 3.9 +/- 0.6 vol%, respectively. Substituting 0.6 MAC of isoflurane with an equipotent concentration of N2O (Condition B) resulted in an increase in both V mca and AVDO2 of approximately 20% (P < 0.05). These findings suggest that the increase in flow was accompanied by an even greater increase in metabolic rate. Adding 0.6 MAC of N2O to 1.1 MAC of isoflurane (Condition C) also increased V mca (P < 0.05). We conclude that N2O is a more potent cerebral vasodilator than an equipotent dose of isoflurane alone in humans.

Sedation by infusion: a clinical trial in cardiac surgery patients

The problem of sedation and analgesia for ventilator-dependent patients was examined in this study. Twenty subjects undergoing elective coronary revascularization surgery at a major medical center were studied. They ranged in age from 49 to 83 years. A randomized, prospective research design was used to place subjects in either an experimental group or a control group. Standard postoperative analgesia with intravenous increments of morphine and midazolam in the control group was compared to treatment with a titratable sufentanil-midazolam infusion in the experimental group. In both groups, hemodynamic variables were measured at selected intervals, sodium nitroprusside consumption was measured, and time to extubation was noted. Data analysis demonstrated no statistically significant differences between the experimental and control groups. The more costly sedative-analgesic infusion appeared to be comparable to conventional treatment with incremental morphine and midazolam based on the results of this study.