British journal of anaesthesia
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Randomized Controlled Trial Clinical Trial
Amrinone can accelerate the cooling rate of core temperature during deliberate mild hypothermia for neurosurgical procedures.
We investigated the effects of i.v. amrinone on intraoperative changes of core temperature during deliberate mild hypothermia for neurosurgery. The patients in a control group (n=10) did not receive amrinone and patients in the amrinone group (n=10) received amrinone 5 microg kg(-1) min(-1) after a loading dose of 1.0 mg kg(-1). Anaesthesia was maintained with nitrous oxide in oxygen, propofol and fentanyl. ⋯ Tympanic membrane temperatures between 30 and 90 min after cooling were significantly lower in the amrinone group than in the control group. During cooling, the times taken to cool to 35 degrees C and to the lowest temperature were significantly shorter in the amrinone group than in the control group. These results suggest that i.v. amrinone can accelerate the cooling rate of core temperature during deliberate mild hypothermia for neurosurgical procedures.
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Randomized Controlled Trial Comparative Study Clinical Trial
Comparison of pattern of breathing with other measures of induction of anaesthesia, using propofol, methohexital, and sevoflurane.
We assessed change of the pattern of breathing as a marker of induction of anaesthesia, using a method of maintaining spontaneous breathing throughout the induction period. We compared this index with a measure used clinically, the lash reflex, and measures used for drug investigations such as loss of grip of an object, cessation of finger tapping, and loss of arm tone. Ninety female patients (mean age 32 (17-63) yr, mean weight 63 (10) kg) were randomly allocated to induction of anaesthesia using propofol, methohexital, or sevoflurane. ⋯ The mean time to change in breathing pattern was 47 (20) s for propofol, 53 (14) s for methohexital, and 78 (29) s for sevoflurane. Although the time to achieve each end point was different, all the end points (except the lash reflex) appeared to provide similar measures of induction of anaesthesia. The pattern of breathing is an early sign of the onset of anaesthesia.
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Acute lung injury after oesophagectomy is well recognized but the risk factors associated with its development are poorly defined. We analysed retrospectively the effect of a number of pre-, peri- and post-operative risk factors on the development of lung injury in 168 patients after elective oesophagectomy performed at a single centre. The acute respiratory distress syndrome (ARDS) developed in 14.5% of patients and acute lung injury in 23.8%. ⋯ Features associated with the development of ARDS included a low pre-operative body mass index, a history of cigarette smoking, the experience of the surgeon, the duration of both the operation and of one-lung ventilation, and the occurrence of a post-operative anastomotic leak. Peri-operative cardiorespiratory instability (measured by peri-operative hypoxaemia, hypotension, fluid and blood requirements and the need for inotropic support) was also associated with ARDS. Acute lung injury after elective oesophagectomy is associated with intraoperative cardiorespiratory instability.
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Randomized Controlled Trial Clinical Trial
Clonidine decreases propofol requirements during anaesthesia: effect on bispectral index.
Assessment of the effect of clonidine on depth of anaesthesia is difficult because clonidine combines analgesic, sedative and direct haemodynamic effects. We thus evaluated the influence of clonidine on the bispectral index (BIS) and its potential dose-sparing effect on propofol. After induction of anaesthesia with target-controlled infusion of propofol and obtaining an unchanged bispectral index (pre-BIS), clonidine 4 microg kg(-1) or placebo was administered randomly to 50 patients in a double-blind manner. ⋯ Administration of clonidine resulted in a decrease in the BIS from 45 (SD 4) to 40 (6) (P<0.001), which allowed a reduction of propofol target concentration from 3.3 (0.6) to 2.7 (0.7) microg ml(-1) (P<0.001) and measured propofol concentration from 2.9 (0.6) to 2.5 (0.7) kg ml(-1) (P=0.009) in order to maintain the pre-BIS value. During subsequent surgery, propofol requirements were reduced by 20% (P=0.002) in the clonidine group and a similar amount of remifentanil was used in each group. The increase in anaesthetic depth given by clonidine can therefore be measured with bispectral EEG analysis and allows reduction of the propofol dose to achieve a specific depth of anaesthesia.
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If the in vivo effects of anaesthesia are mediated through a specific receptor system, then a relationship could exist between the regional changes in brain metabolism caused by a particular agent and the underlying regional distribution of the specific receptors affected by that agent. Positron emission tomography data from volunteers studied while unconscious during propofol (n=8) or isoflurane (n=5) anaesthesia were used retrospectively to explore for evidence of relationships between regional anaesthetic effects on brain glucose metabolism and known (ex vivo) regional distribution patterns of human receptor binding sites. ⋯ Isoflurane's reductions positively correlated only with muscarinic (acetylcholine) binding density (r=0.85, P<0.05). These findings are consistent with the hypothesis that some of propofol's in vivo anaesthetic effects may be mediated through a GABAergic mechanism and suggest some of isoflurane's in vivo effects might involve antagonism of central acetylcholine functioning.