A randomized double-blind comparison of fentanyl- and sufentanil-oxygen anesthesia for abdominal aortic surgery.

Twenty-four patients undergoing abdominal aortic surgery for aneurysm or occlusive vascular disease entered a randomized, double-blind protocol comparing high-dose narcotic anesthesia with fentanyl (125 micrograms/kg) or sufentanil (25 micrograms/kg). All patients received perioperative beta-adrenergic blockade therapy. Hemodynamic and electrocardiographic (leads II and V5) responses to induction, intubation, skin incision, aortic cross-clamping, and declamping were studied. Sufentanil produced a transient decrease in mean arterial pressure and a significant reduction of systemic vascular resistance during induction. However, no significant hemodynamic differences were observed between the two groups during intubation, or at any other time during surgery. To maintain mean arterial pressure within 20% of the awake control value, the fentanyl group required an average infusion of 1.0 +/- 1.1 micrograms/kg/min of nitroglycerin compared with 1.7 +/- 2.8 micrograms/kg/min for the sufentanil group. Low-dose isoflurane was required in 30% of patients in the fentanyl group, compared with 41% of the sufentanil group, for control of blood pressure. The multiple-bolus technique of narcotic administration resulted in a wide but parallel range of plasma concentrations from induction to the end of surgery with both narcotics. Mean plasma fentanyl concentrations varied between 7.2 +/- 1.4 ng/mL and 26.5 +/- 7.9 ng/mL, and mean sufentanil plasma concentrations varied between 1.0 +/- 0.1 ng/mL and 10.6 +/- 7.2 ng/mL throughout surgery. Within this range of narcotic serum levels, the authors were unable to identify a specific threshold level for either narcotic above which hemodynamic responses were consistently attenuated. A low incidence (4.5%) of intraoperative myocardial ischemia was observed.(ABSTRACT TRUNCATED AT 250 WORDS)

Acceleration of digoxin clearance by activated charcoal.

The effect of repeated oral doses of activated charcoal on intravenous digoxin kinetics was evaluated in a randomized, crossover study. Ten healthy subjects received infusions of 10 micrograms/kg digoxin alone and with 225 gm activated charcoal over 40 hours. Multiple serum digoxin concentration determinations were made after each dose by radioimmunoassay. Noncompartmental kinetic analysis was used. Digoxin clearance increased an average of 47% (range -2% to 119%) during charcoal treatment, from 12.2 +/- 2.0 to 18.0 +/- 2.9 L/hr. The volume of distribution at steady state decreased from 495 +/- 196 to 375 +/- 162 L, and the terminal t1/2 was shortened from 36.5 +/- 11.8 to 21.5 +/- 6.5 hr during charcoal treatment. Likewise, mean residence time decreased, from 41.1 +/- 20 to 19.9 +/- 7.8 hr. Kinetic predictions would suggest greater proportional increases in digoxin clearance in patients with renal impairment. We conclude that repeated doses of charcoal enhance the clearance of digoxin and should be considered for use in digoxin toxicity.

Effects of naloxone on exercise performance.

This study was designed to investigate the effects of naloxone on athletic performance in humans. Two groups of elite middle-distance runners performed a maximal or a submaximal exercise protocol following the double-blind intravenous injection of either naloxone (0.15 mg X kg body wt-1) or saline. The maximal test (group M) was comprised of a short-duration treadmill run to maximal intensity; the submaximal test (group S), a prolonged submaximal treadmill run to exhaustion. O2 uptake, heart rate, ventilation, and perceived exertion were determined during each test. Perception of pain was assessed after exercise by use of a modified McGill pain questionnaire. No significant differences between placebo and naloxone treatments were found in any of the measured variables at the usually accepted 5% (P = 0.05) confidence level; however, evidence suggesting differences (i.e., P = 0.1 to 0.05) in these important respects was observed. In group M, maximal exercise performance measured by maximal O2 consumption was not different between placebo and naloxone; results suggest that VE was increased (P = 0.08) following naloxone, but only at the final work stage. In group S, exercise performance time was reduced following naloxone (P = 0.09), whereas the affective component of pain was increased (P = 0.06); no differences in the measured physiological variables were observed. These results suggest the following: 1) the opiate receptor-endorphin system may alter the perception of pain associated with prolonged high-intensity submaximal exercise with a resultant significant effect on performance; and 2) it may play a role in the control of ventilation during maximal exercise.