Canadian Anaesthetists' Society journal
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The effect of epidural morphine on the duration of action of epidural 2-chloroprocaine was studied in a double-blind fashion in 30 patients following elective Caesarean section. When compared to epidural saline controls (n = 15), patients (n = 15) who received epidural morphine (4.0-5.0 mg) did not experience a prolongation or reduction in the duration of the somatic or sympathetic nervous system blockades produced by epidural 2-chloroprocaine.
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In 150 Sprague-Dawley rats, morphine and fentanyl dose-effect curves were determined for the following three end points--prevention of purposeful movement response to a noxious stimulus (PM), loss of righting reflex (RR), and prevention of heart rate increase to a noxious stimulus (HR). Accordingly, for each agent, three series of experiments were performed with intravenous administration of the following doses: morphine--3-10 mg X kg-1 for PM, 3-10 mg X kg-1 for HR, 35-55 mg X kg-1 for RR; fentanyl - 5-15 micrograms X kg-1 for PM, 18-30 micrograms X kg-1 for RR, 200-400 micrograms X kg-1 for HR. ⋯ The ratios of RR ED50 to PM ED50 were 7.8 for morphine vs 2.4 for fentanyl (p less than 0.001), the ratios of HR ED50 to PM ED50 were 1 and 33, respectively (p less than 0.001). These results suggest that blockade of movement response to noxious stimulation (which is usually regarded as an index for analgesic action of opioids) and blockade of heart rate increase to noxious stimulation (which is one of the goals of anaesthesia) is not necessarily induced by intravenous narcotic anaesthetics through the same mechanism.(ABSTRACT TRUNCATED AT 250 WORDS)
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To assess the effects of isoflurane on chemical regulation of ventilation, we studied the ventilatory responses to (1) hyperoxic hypercarbia, (2) isocapnic hypoxaemia, and (3) a single half vital capacity breath of carbon dioxide 20 per cent in oxygen in 12 human subjects, awake and sedated or anaesthetized with isoflurane, 0.1 or 1.1 MAC. Sedation did not alter ventilation nor the ventilatory response to hypercarbia but reduced the responses to hypoxaemia and to the half vital capacity breath of CO2. ⋯ The results indicate that isoflurane reduces ventilatory responses to several chemical drives and that it selectively impairs those responses mediated by peripheral chemoreceptors. In these respects, isoflurane is similar to halothane and enflurane.
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Comparative Study
Neostigmine antagonism of succinylcholine phase II block: a comparison with pancuronium.
To assess the efficacy of neostigmine antagonism of succinylcholine phase II block, succinylcholine infusions were given to 17 patients for durations varying from 44 to 192 minutes. A control group (17 patients) received a pancuronium infusion for similar times. Ninety per cent neuromuscular block was maintained in these two groups by adjustment of the infusion rates and, in a third group, with intermittent doses of pancuronium. ⋯ Ten minutes after the infusion was stopped, atropine and neostigmine were given to all patients who received pancuronium and to 11 patients in the succinylcholine group whose train-of-four ratio (T4/T1) was less than 0.7. During the subsequent 15 minutes, recovery was more rapid in the succinylcholine group than in either the pancuronium-infusion or pancuronium-bolus groups. It is concluded that succinylcholine-induced phase II block can be safely and rapidly antagonized with neostigmine.