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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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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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.
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The veterinary neurosteroid anaesthetic Saffan has the same formulation as Althesin now withdrawn from human use and is a mixture of two neurosteroids, alphadolone, and alphaxalone. The molecular structures of these two pregnanes and their properties as i.v. anaesthetics were reported to be similar. Preliminary experiments showed that alphadolone caused powerful antinociceptive effects without sedation when given i.p. ⋯ These effects were reversed at the level of the spinal cord by intrathecally-administered bicuculline (10 pmol). We conclude that a metabolite of alphadolone acetate produced in the liver leads to antinociceptive effects after i.p. and intragastric administration of the parent compound. This antinociception involves spinal cord GABA(A) receptors, even though the drug was administered via a non-spinal route.
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The primary objective of this study was to determine in vivo tissue/blood partition coefficients of propofol for use in physiological modelling of its pharmacokinetics. The sheep was used as an animal model. In the main series of experiments, crossbred ewes received a bolus of propofol 1% (Diprivan) followed by an infusion during which blood concentrations were measured at intervals. ⋯ Tissue/blood partition coefficients depend on the amount of triglyceride which accumulates in blood from the propofol vehicle; for blood, free of added triglyceride, the following coefficients were calculated: brain, 3.23; heart, 5.94; kidney, 2.46; spleen, 1.86; semimembranosus muscle, > or = 1.61; triceps muscle, > or = 1.47. Calculated tissue/water coefficients were 35 times greater. There was indirect evidence of extraction of propofol by the lungs.