British journal of anaesthesia
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We investigated the cerebral haemodynamic effects of 1 MAC desflurane anaesthesia in nine male patients scheduled for elective coronary bypass grafting. For the measurement of cerebral blood flow (CBF) a modified Kety-Schmidt saturation technique with argon as inert tracer gas was used. Measurements of CBF were made before induction of anaesthesia and 30 min after induction under normocapnic, hypocapnic and hypercapnic conditions in sequence. ⋯ Hypo- and hypercapnia caused a 22% decrease and a 178% increase in CBF, respectively. These findings may be interpreted as the result of two opposing mechanisms: cerebral vasoconstriction induced by a reduction of cerebral metabolism and a direct vasodilator effect of desflurane. CBF alterations under variation of PaCO2 indicate that cerebrovascular carbon dioxide reactivity is not impaired by application of 1 MAC desflurane.
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Alpha2-adrenergic agonists given intrathecally result in antinociception and intracerebroventricularly (ICV) in sedation. To examine whether different alpha2-adrenergic receptor subtypes differentially mediate antinociception and sedation, we measured the relative potency of three alpha2-adrenergic agonists, dexmedetomidine (DMET), clonidine (CLON) and UK-14.304 (UK), after spinal and ICV administration. Each agonist was given either alone or in the presence of systemically administered yohimbine, which acts as a competitive alpha2-antagonist in unanaesthetized rats. ⋯ Again, yohimbine pretreatment produced a right shift of the ICV sedation dose-response curves (UK > DMET > CLON). Thus, we conclude that the spinal analgesic effects of DMET, CLON and UK appear to be mediated by two sites. After ICV delivery, DMET, CLON and UK appear to act at a common supra-spinal site to produce sedation and this site resembles that acted upon by UK in the spinal cord.
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The aim of this study was to determine for how long the duration of action of increments of mivacurium can be influenced by previous pancuronium administration. Fifteen patients, ASA I or II, undergoing general anaesthesia for major abdominal surgery were investigated. The post-tetanic count (PTC) was measured at the adductor pollicis muscle. ⋯ The mean duration of the second dose of pancuronium was 53 min (SD 13 min) and of the first dose of mivacurium, 66 min (SD 14 min) (P < 0.01). The duration of action of further mivacurium boluses decreased significantly until the fifth dose. It took 222 minutes (95% confidence interval 190, 253 min) after the second pancuronium dose before the duration of action of mivacurium returned to normal values and became constant and predictable.
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We describe a 3-yr-old patient in whom a central venous catheter (CVC) was inadvertently inserted into a persistent left superior vena cava (PLSVC). This congenital anomaly was diagnosed using transthoracic echocardiography. The aetiology and the implications for the anaesthetist are discussed.
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The perioperative pharmacokinetics of transdermally-delivered fentanyl were compared in 10 young adult (mean [range] age 32.7, [25-38] yr) and eight elderly (mean [range] age 73.7 [64-82] yr) patients following abdominal surgery. Transdermal fentanyl patches designed to release 50 micrograms h-1 were applied 2 h preoperatively and left in place for 72 h. ⋯ Mean maximum plasma concentrations were 1.9 ng ml-1 and 1.5 ng ml-1 in the younger and elderly groups respectively (ns). There were no differences in the time at which maximum plasma concentrations occurred (tmax), elimination half-life after patch removal, or AUC(0-infinity).