Anesthesiology
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Comparative Study
Clinical characteristics of desflurane in surgical patients: minimum alveolar concentration.
Desflurane (formerly I-653) is a new inhalaticnal anesthetic with a promising pharmacokinetic profile that includes low solubility in blood and tissue, including fat. Since its lipid solubility is less than that of other volatile agents, it may have lower potency. Low solubility would be expected to increase the rate at which alveolar concentration approaches inspired concentration during induction as well as to increase the rate of elimination of desflurane from blood at emergence. ⋯ The MAC of desflurane in O2 was 7.25 +/- 0.0 (mean +/- SD) in the 18-30-yr age group, and 6.0 +/- 0.29 in the 31-65-yr group; the addition of 60% N2O reduced the MAC to 4.0 +/- 0.29 and 2.83 +/- 0.58, respectively. The median time from discontinuation of desflurane to an appropriate response to commands was 5.25 min. Desflurane appears to be a mild airway irritant but was well tolerated by all patients.
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Comparative Study
The neuromuscular effects of desflurane, alone and combined with pancuronium or succinylcholine in humans.
The neuromuscular effects of desflurane administered alone were studied in ten healthy human volunteers aged 20-27 yr. Also, the dose-response relationships of pancuronium and succinylcholine in surgical patients during anesthesia with desflurane (n = 13) were compared to those during isoflurane anesthesia (n = 14). In the volunteers, we measured the mechanical response of the adductor pollicis muscle to stimulation of the ulnar nerve in a train-of-four (TOF) sequence at 2 Hz and at tetanic frequencies of 50, 100, and 200 Hz, each administered for 5 s. ⋯ The doses of pancuronium that depressed T1 amplitude by 50% (ED50) were similar during anesthesia with 1.25 MAC desflurane, 10.5 +/- 2.8 micrograms/kg (mean +/- SD) and 1.25 MAC isoflurane, 12.3 +/- 5.0 micrograms/kg. The ED50 doses of succinylcholine were similar during anesthesia with desflurane 132 +/- 76 micrograms/kg and isoflurane 123 +/- 36 micrograms/kg. We conclude that desflurane significantly depresses neuromuscular function and augments the action of pancuronium and succinylcholine to a degree similar to that of isoflurane.
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Comparative Study
Kinetics of desflurane, isoflurane, and halothane in humans.
The low solubility of desflurane in blood and tissues suggests that the partial pressures of this agent in blood and tissues should approach the inspired partial pressure more rapidly than would the blood and tissue partial pressures of other potent inhaled anesthetics. We tested this prediction, comparing the pharmacokinetics of desflurane with those of isoflurane, halothane, and nitrous oxide in eight volunteers. We measured the rate at which the alveolar (endtidal) (FA) concentration of nitrous oxide increased towards an inspired (FI) concentration of 65-70%, and then measured the concurrent increase in FA and mixed expired concentrations (FM) of desflurane, isoflurane, and halothane at respective FI values of 2.0%, 0.4%, 0.2%. ⋯ Time constants for a five-compartment mammillary model for halothane and isoflurane differed for the lungs, fat group, and hepatic metabolism, and exceeded those for desflurane for all compartments. In summary, we found that FA/FI of desflurane increases more rapidly and that FA/FA0 decreases more rapidly in humans than do these variables with other available potent anesthetics. We also found that desflurane resists biodegradation in humans and so may have little or no toxic potential.
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Cardiac morbidity and mortality after coronary artery bypass graft (CABG) surgery continue to be significant problems. To determine the prevalence, characteristics, and prognostic importance of postoperative myocardial ischemia after CABG surgery, the authors monitored 50 patients continuously for 10 perioperative days with the use of two-lead electrocardiography (ECG). ECG changes consistent with ischemia were defined as a reversible ST depression of 1 mm or greater or an elevation of 2 mm or greater from baseline, lasting at least 1 min. ⋯ Five adverse cardiac outcomes occurred on the day of surgery; all five were preceded by postoperative ischemia, three by intraoperative ischemia before bypass, and none by preoperative ischemia. Patients with late postoperative ischemia did not have an adverse cardiac outcome. The authors conclude the following: 1) ischemia is more prevalent postoperatively than preoperatively or intraoperatively before bypass; 2) the incidence of postoperative ischemia peaks shortly after revascularization, during which time it is symptomatically silent, difficult to detect, and related to adverse cardiac outcome; 3) late postoperative ischemia also is silent, but it is less prevalent and not associated with in-hospital adverse cardiac outcome; and 4) a relationship between ischemia and persistently elevated postoperative heart rate may exist and warrants additional investigation.