Anesthesiology
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The efficacy of hydroxocobalamin (vitamin B12a) as a specific, nontoxic antidote in acute cyanide poisoning was tested. Guinea pigs receiving lethal intravenous NaCN injections were treated with either vitamin B12a or saline solution. There was a statistically significant antidotal effect of the vitamin. No toxic effect was observed with large doses of the vitamin.
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Halothane-induced contractures in isolated muscle fibers from swine susceptible to malignant hyperthermia (MHS) were significantly less when fibers were incubated in KRB plus 6.2 x 10(-6) M dantrolene sodium prior to the administration of 4 per cent halothane. Administration of dantrolene sodium at the time of maximum contraction to NHS fibers in which contractures had been induced by halothane significantly increased the rate of relaxation of these fibers compared with similar fibers not treated with dantrolene sodium. This study indicates possible prophylactic and therapeutic value of dantrolene sodium in malignant hyperthermia and suggests that the previously reported effectiveness of dantrolene sodium in preventing and treating halothane-induced contractures may be due, at least in part, to its direct effect on muscles.
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Hemodynamic response to ganglionic blockade with pentolinium during N2O-halothane anesthesia in man.
Hemodynamic and blood-gas variables were studied before and after pentolinium tartrate administration in six patients anesthetized with nitrous oxide-halothane and maintained at PaCO2 35-40 torr. Measurements were made prior to induction of anesthesia; before and 10, 20, and 60 minutes after administration of pentolinium (0.3 mg/kg); 15 minutes after return of arterial blood pressure to control values. Mean arterial blood pressure (MAP) was significantly decreased at 20 (P less than 0.02) and 60 (P less than 0.001) minutes, in association with significant decreases in systemic vascular resistance (SVR) (P less than 0.05 and P less than 0.005). ⋯ Fifteen minutes after return of MAP to control levels, SVR was 11.5 per cent lower, while CO was still significantly higher (P less than 0.02) than control values. Following ganglionic blockade with pentolinium during halothane-N2O anesthesia, HR is a valuable index of changes in CO, while the HR X ASP index may be utilized to evaluate changes in MVO2. Assessment of myocardial performance during controlled hypotension is possible by the use of routinely available measurements.
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Twenty patients requiring ventilation for acute respiratory failure were studied to determine whether intrapulmonary shunt fraction (Qs/Qt) measured at an inspired oxygen concentration (FIO2) of 1.0 differs from Qs/Qt measured at the clinically indicated FIO2 and, if so, the mechanism by which this occurs. Qs/Qt increased from 15.5 +/- 1.8 per cent (mean +/- SE) at the clinically indicated inspired oxygen fraction (FIO2 0.3-0.6) to 21.7 +/- 2.1 per cent after 20 minutes at FIO2 1.0. Functional residual capacity (FRC) decreased by 6 +/- 6 per cent and total compliance (CT) by 10 +/- 6 per cent. ⋯ Patients with increased PCWP showed smaller increases in Qs/Qt with 100 per cent oxygen. These findings suggest two mechanisms responsible for the increase in Qs/Qt: 1) redistribution of blood flow to nonventilated areas, resulting from the vasodilating effect of an increased oxygen tension in the vessels of hypoxic lung segments; 2) resorption atelectasis. Of the total change in Qs/Qt observed during ventilation with oxygen, 63 per cent was calculated to be due to factors other than a decrease in FRC. (Key words: Ventilation, positive end-expiratory pressure; Oxygen, pulmonary shunt and; Lung, compliance; Lung, shunts.)