British journal of anaesthesia
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Randomized Controlled Trial Comparative Study Clinical Trial
Effects of midazolam and diazepam as premedication on heart rate variability in surgical patients.
We have examined the effects of midazolam 0.06 mg kg-1 i.m. and diazepam 0.2 mg kg-1 orally as premedication on the spectral components of heart rate (HR) variability in 24 elderly patients aged 65-87 yr and 24 young patients aged 18-35 yr undergoing elective surgery. The low-frequency/high-frequency (LF/HF) ratio of HR variability increased after arrival in the operating room in elderly patients who received no premedication, but not in young patients. ⋯ However, diazepam increased the low-frequency component and the total power of HR variability in both young and elderly patients. We conclude that cardiac sympathetic nerve activity increased after arrival in the operating room in the elderly, that midazolam or diazepam reduced this increase and that diazepam caused an increase in the total power of HR variability that has not been observed for other agents.
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A postal survey of previous paediatric anaesthetic training, current paediatric experience and management of an infant pyloromyotomy was undertaken among consultant anaesthetists in the UK. A total of 851 questionnaires were returned, giving a response rate of 31%; 352 (41%) consultants had at least one paediatric list each week, 180 (21%) anaesthetized more than one infant less than 6 months old each month and 373 (44%) had obtained more than 6 months' specialist training. ⋯ Choice of technique was related to the duration of specialist paediatric training and when it was received, but not to current paediatric anaesthetic experience. The results are discussed in relation to recently published recommendations on paediatric anaesthetic services.
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We have studied the effects of extracranial ischaemia and intracranial hypoxia on measurement of cerebral oxygenation using near-infrared, reflectance-mode, cerebral oximetry (Invos 3100 cerebral oximeter) in healthy adult subjects. Under stable systemic conditions, scalp ischaemia induced by a pneumatic tourniquet caused an apparent reduction in mean regional cerebral oxygenation (rSO2) from mean 72 (SD 6)% to 59 (7)% (n = 8, P < 0.001). rSO2 returned to control values within 1 min of release of the tourniquet. Local scalp ischaemia induced by rapid frontalis muscle exercise caused a significant reduction (4.5 (2)% in rSO2 (n = 12, P < 0.001). ⋯ There was a significant correlation between the percentage reduction in rSO2 and SpO2 during hypoxia (r = 0.81, P < 0.001). We conclude that the Invos cerebral oximeter was capable of detecting tissue hypoxia deep to the scalp under carefully controlled conditions but that it also was affected significantly by changes in extracranial blood flow and oxygenation which may affect its reliability in clinical practice. Further work is necessary to define those situations in which cerebral oximetric monitoring is useful and valid.
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The incidence of myocardial ischaemia during tracheal intubation and extubation was compared using ambulatory ECG monitoring in 60 patients undergoing a variety of different surgical operations. Seven patients had myocardial ischaemia after tracheal intubation and seven patients during tracheal extubation. The patients who developed myocardial ischaemia during tracheal extubation had significantly greater rate-pressure products immediately before tracheal extubation (P < 0.05) and 1 min after tracheal extubation (P < 0.01) compared with those patients who did not develop myocardial ischaemia during extubation.