The nonlinear potency of sub-MAC concentrations of nitrous oxide in decreasing the anesthetic requirement of enflurane, halothane, and isoflurane in rats.

The effect of nitrous oxide (N2O) on the MAC of enflurane, halothane, and isoflurane was determined in male rats. Each rat received either enflurane, halothane, or isoflurane, along with 0%, 15%, or 75% N2O. Anesthetic equilibration was verified by mass spectrometry sampling of end-tidal gases. MAC was determined at each N2O concentration by the standard tail clamp method. The N2O dose-response data for each animal were fit by a second-order polynomial equation to estimate the value of a second-order coefficient. A linear dose-response would result in a value of zero, whereas the extent to which the data deviate from nonlinearity would be reflected by an increase in the value of this coefficient. The null hypothesis, that the second-order coefficient should be zero, was tested by a one-sample two-tailed t test. The volatile anesthetic requirement decreased as the N2O concentration increased; however, it did not do so linearly. For each of the three volatile anesthetic groups, the second-order coefficients were consistently greater than zero (P less than 0.05). These data are not consistent with the accepted presumption that the summation of N2O with volatile anesthetics is linear.

Enflurane in anaesthesiological practice.

Enflurane was given as the principal inhalatory agent in general anaesthesia in 75 patients aged from 17 to 55 years for gynaecological operations. Anaesthesia was conducted with muscle relaxation administering the drug in concentration of 0.2-1% vol. (mean maintenance concentration 0.6%). No cardiovascular, hepatic and renal disturbances were observed. The serum glucose level increased by a mean value of 64.8% during enflurance anaesthesia, however, it did not cross the renal threshold. Enflurane failed to ensure postoperative analgesia. The drug may be used as a valuable supplement to the presently used anaesthetic agents.

[Clinical evaluation of the new anesthetic "Ethrane"]. / Evaluation clinique d'un nouvel agent anesthésique "l'éthrane"

Seventy-four patients aged 14 months to 71 years, classified as ASA I and II were anesthetised with Ethrane for surgical interventions of mean duration 117 minutes. With the exception of 5 patients who were directly anesthetised with Ethrane, the others received Ethrane after induction with Penthiobarbitone. Maintenance of anesthesia was ensured with 1 to 4p. 100 concentrations of Ethrane and 33p. 100 oxygen and 66p. 100 nitrous oxide. Tracheal intubation was facilitated by injection of 1 mg/kg of succinylcholine. Induction with enflurane is rapid with no phenomena of excitation or irritation of the ear passages. The cardiovascular apparatus is stable with no arrythmia but an increase in heart rate of 11 to 50p. 100 is noted and in 41p. 100 of the cases hypotension of 35p. 100 of the intitial value. During spontaneous ventilation, a type of rapid and superficial respiration is observed with a flow volume of 5.3 ml/kg for an average frequency of 25/min. The arterial blood gases show slight hypercapnia. Myorelaxation is significant and better than that obtained with halothane. Coming round poses few problems apart from agitation in adolescents. Response to simple orders appears at 13 minutes. Trembling and rigidity occur in 41p. 100 of the cases for 5 to 30 minutes. From the hepatic point of view, no lastin enzyme changes were noted and no renal toxicity was demonstrated. Ethrane appears to be a good anesthetic agent but the few advantages mentioned means that it does not fulfil ideal conditions.

[The place of enflurane in neuro-anesthesia]. / Place de l'enflurane en neuro-anesthésie

In neuro-anaesthesia, anaesthetic agents must be in accordance with certain criteria necessary to the preservation of the integrity of the brain. Therefore it was in such a perspective that we re-appraised the effects of enflurane upon cortical irritability, metabolism, cerebral blood flow and intracranial pressure. We reached the following conclusions: in normocapnia, and with optimal clinical concentrations, this drug remains the best anaesthetic agent since it has no harmful effect either upon metabolism or upon cerebral blood flow. However, in hypertensive cerebral lesions, caution is called for an it seems advisable to combine Enflurane with mild doses of fentanyl. Finally, anaesthesia with enflurane is followed by a rapid and smooth return to consciousness, a valuable factor in neurosurgery where post-operative neurological watching matters very much.