British journal of anaesthesia
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Randomized Controlled Trial Comparative Study Clinical Trial
Effects of extradural block: comparison of the properties, circulatory effects and pharmacokinetics of etidocaine and bupivacaine.
Five healthy, unmedicated male volunteers, aged 19-25 yr, participated in a double-blind, crossover study. Each subject received, on separate occasions and via a catheter placed at L2, 1.5% etiodocaine HCl20 ml with adrenaline 5 mug/ml, or 0.75% bupivacaine HCl 20 ml with adrenaline 5 mug/ml for extradural analgesia. In addition, in order to calculate the absorption rate of the local anaesthetic agent, each subject received on two further occasions etidocaine HCl 75 mg and bupivacaine HCl 75 mg respectively by i.v. infusion, over a period of 10 min. ⋯ For etidocaine these measurements remained below control values for 120-210 min after injection. The mean maximum arterial plasma concentration of etidocaine was 1.52 +/- 0.64 mug/ml, at 14 +/- 2 min and of bupivacaine was 1.35 +/- 0.63 mug/ml, achieved at 20 +/- 4 min. The systemic absorption of both drugs occurred in a biphasic pattern with a fast and slow half-life of 0.3 and approximately 8 h respectively.
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Cerebral circulation and metabolism during Althesin anaesthesia were studied in seven healthy patients. Althesin was given in a single dose of 0.1 ml/kg and thereafter infused at a constant rate of 0.3 ml/kg/h. During Althesin infusion, the cerebral blood flow (CBF), the cerebral metabolic rate for oxygen (CMRo2) were 29 +/- 10 ml/100 g/min and 1.7 +/- 0.4 ml/133 g/min, respectively. ⋯ During CBF measurement, the mean cerebral perfusion pressure, cerebral vascular resistance (CVR) and arterial carbon dioxide tension (PaCO2) were 89 +/- 16 mm Hg, 3.4 +/- 1.3 mm Hg/ml/100 g/min, and 36 +/- 9 mm Hg, respectively. The relationship between CBF and PaCO2 were studied and it was found that during Althesin anaesthesia reactivity of cerebral vessels to the alteration of PaCO2 was maintained. It is concluded that Althesin caused cerebral metabolic depression which was accompaned by a decrease in CBF and an increase in CVR.
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In ventilated anaesthetized rabbits the relationship between the oesophageal pressure and the intrapleural pressure, measured with an air-filled balloon system, was studied. A balloon 15 mm long and 3 mm diameter detected 95% of the measured intrapleural pressure, provided the balloon was positioned accurately. In babies undergoing IPPV, the best balloon position was in the lower third of the oesophagus. When synchronous spontaneous respiration occurred in the course of IPPV the mean of intrapleural pressure remained negative in spite of positive ventilating pressures in the range 30-45 cm H2O.