Anaesthesia
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Randomized Controlled Trial Clinical Trial
Prophylactic amrinone for weaning from cardiopulmonary bypass.
This prospective, randomised, double-blind, controlled clinical study was performed at a single tertiary referral centre to test the hypothesis that the prophylactic administration of amrinone before separation of a patient from cardiopulmonary bypass decreases the incidence of failure to wean, and to identify those patients who could be predicted to benefit from such pre-emptive management. Two hundred and thirty-four patients, scheduled to undergo elective cardiac surgery, were randomly allocated to receive either a bolus dose of 1.5 mg x kg(-1) amrinone over 15 min, followed by an infusion of 10 microg x kg(-1) x min(-1), or a bolus of placebo of equal volume followed by an infusion of placebo. Treatment with amrinone or placebo was initiated upon release of the aortic cross-clamp, before weaning from cardiopulmonary bypass. ⋯ Significantly fewer patients failed to wean in the group that received prophylactic amrinone than in the control group (7 vs. 21%, p = 0.002). Amrinone improved weaning success regardless of left ventricular ejection fraction, although this benefit was statistically significant only in the group with left ventricular ejection fractions > 55%. Of the 32 patients who failed to wean from cardiopulmonary bypass, 14 had normal pre-operative left ventricular ejection fractions.
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We studied 20 anaesthetic assistants applying simulated cricoid pressure with the left or right hand in random order. Simulated cricoid pressure was continued for up to 5 min with one hand and then, after resting, with the other hand. Applied pressure was measured at intervals and the subjects were blind to the results. ⋯ Cricoid pressure was released before 5 min in three cases, two left-handed and one right-handed. Our results demonstrate that anaesthetic assistants apply a lower force than is classically taught and are able to maintain the force with either hand for a sustained period. Application with the left hand is justified where clinically indicated but may have a lower margin for error than when applied with the right hand.
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Randomized Controlled Trial Clinical Trial
The effect of sevoflurane on implicit memory: a double-blind, randomised study.
Forty-eight gynaecological patients were randomly allocated to three groups (target end-tidal sevoflurane concentration 1.2, 1.5 or 2%), and into subgroups for positive or neutral suggestion. Anaesthesia was induced by inhalation of sevoflurane in oxygen. When the target concentration was achieved, the bispectral index, computed from a bi-frontal electroencephalogram, was noted. ⋯ Priming increased the likelihood of identifying words in the 1.2% group only, i.e. there was evidence of implicit memory in this group. There was no evidence of a therapeutic effect of positive suggestion (p = 0.3), but the power of this part of the study was low. The bispectral index did not achieve statistical significance as an indicator of susceptibility to priming.
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We investigated the use of measurements of serum concentrations of the cardiac proteins troponins I and T as biochemical markers of myocardial cell damage in 80 patients undergoing vascular or major orthopaedic surgery. Holter electrocardiographic monitoring was carried out before surgery and for 3 days after surgery. Blood samples for troponins I and T and creatine kinase-MB isoenzyme were taken on each of these 4 days. ⋯ There were no associations between postoperative ischaemia and cardiac protein concentrations. The relative odds for the associations of major adverse outcome at 3 months after surgery and postoperative ischaemia or increased serum concentrations of the three proteins were 5.39 [95% confidence intervals 1.16-27.67] for postoperative ischaemia; 5.64 [1.07-31.00] for creatine kinase-MB isoenzyme; 17.00 [2.20-116.54] for troponin T and 13.20 [1.12-135.00] for troponin I. We found troponin T to be the only prospective marker for both major and minor cardiovascular complications (relative odds 10.65 [1.26-252.88]).
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We studied 30 unpremedicated patients undergoing muscle biopsy under femoral nerve block to determine sedation levels reached with a Diprifusor target-controlled propofol infusion, in order to establish the equivalent of the ED50 for different levels of depth of sedation. Infusion was started at 0.8 microg x ml(-1) and altered by increments of 0.1 microg x ml(-1) after equilibrium between target and calculated concentrations, until the desired level of sedation was reached. ⋯ At sedation level 3, several patients exhibited spontaneous movement, hindering surgery. Oxygen supplementation is recommended for sedation at level 4.