Anesthesia and analgesia
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Anesthesia and analgesia · May 2003
Clinical TrialEvaluating surrogate measures of renal dysfunction after cardiac surgery.
Renal insufficiency after cardiac surgery is associated with increased mortality, morbidity, and length of intensive care unit stay. A convenient surrogate measure would facilitate the evaluation of renal-protective therapies. We evaluated two measures: the 72-h change in serum creatinine (Cr) (DeltaCr(72h)) and the percentage 72-h change in calculated (Cockcroft-Gault equation) Cr clearance (%DeltaCrCl(72h)). We randomly selected 2000 individuals who underwent aortocoronary bypass, valve surgery, or both at the Toronto General Hospital between May 1999 and August 2000. The variables were analyzed with frequency histograms and normal probability plots. Their association with dialysis, mortality, and prolonged intensive care unit stay was determined by using receiver operating characteristic (ROC) curves. DeltaCr(72h) was skewed to the right, whereas %DeltaCrCl(72h) was normally distributed. ROC curve areas showed DeltaCr(72h) to be a good predictor of dialysis (0.98), death (0.83), and prolonged hospitalization (0.74). %DeltaCrCl(72h) had similar ROC curve areas for predicting dialysis (0.97), death (0.82), and prolonged hospitalization (0.74). ROC curve areas did not differ significantly with respect to mortality (P = 0.89), dialysis (P = 0.49), or prolonged hospitalization (P = 0.85). Both variables were correlated with patient-relevant outcomes. Mathematical transformation of DeltaCr(72h) to %DeltaCrCl(72h) results in a normal distribution that is amenable to parametric statistical tests. DeltaCr(72h) and %DeltaCrCl(72h) may be used as surrogate outcomes in future trials. ⋯ A convenient surrogate measure of renal function is needed for evaluating renal-protective therapies in cardiac surgery. We evaluated the performance of serum creatinine concentration and calculated creatinine clearance for predicting dialysis, mortality, and prolonged hospitalization. Both measures were correlated with clinical outcomes. Creatinine clearance had the advantage of a distribution suitable for parametric statistical tests.
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Anesthesia and analgesia · May 2003
Halothane and isoflurane have additive minimum alveolar concentration (MAC) effects in rats.
Studies suggest that at concentrations surrounding MAC (the minimum alveolar concentration suppressing movement in 50% of subjects in response to noxious stimulation), halothane depresses dorsal horn neurons more than does isoflurane. Similarly, these anesthetics may differ in their effects on various receptors and ion channels that might be anesthetic targets. Both findings suggest that these anesthetics may have effects on movement in response to noxious stimulation that would differ from additivity, possibly producing synergism or even antagonism. We tested this possibility in 20 rats. MAC values for halothane and (separately) for isoflurane were determined in duplicate before and after testing the combination (also in duplicate; six determinations of MAC for each rat). The sum of the isoflurane and halothane MAC fractions for individual rats that produced immobility equaled 1.037 +/- 0.082 and did not differ significantly from a value of 1.00. That is, the combination of halothane and isoflurane produced immobility in response to tail clamp at concentrations consistent with simple additivity of the effects of the anesthetics. These results suggest that the immobility produced by inhaled anesthetics need not result from their capacity to suppress transmission through dorsal horn neurons. ⋯ Despite differences in their capacities to inhibit spinal dorsal horn cells, isoflurane and halothane are additive in their ability to suppress movement in response to a noxious stimulus.
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Anesthesia and analgesia · May 2003
The diagnosis of obstructive sleep apnea as a risk factor for unanticipated admissions in outpatient surgery.
The goal of this study was to determine whether the preoperative diagnosis of obstructive sleep apnea (OSA) is an independent risk factor for perioperative complications in patients undergoing nonotorhinolaryngologic outpatient surgical procedures. We used existing databases to identify 234 patients with polysomnography-confirmed OSA who had outpatient surgical procedures in the years 1997 through 2000. Control patients were matched for type of anesthesia, age, sex, body mass index, surgical procedure, and surgical date. Their perioperative medical records were reviewed. There was no significant difference in the intraoperative management of OSA and control patients, except that the laryngeal mask airway was less likely to be used in OSA patients. There was no significant difference in the rate of unplanned hospital admissions (23.9% versus 18.8%; odds ratio, 1.4; 95% confidence interval, 0.8-2.5) or other adverse events (2.1% versus 1.3%; odds ratio, 1.7; 95% confidence interval, 0.4-7.0) between OSA and non-OSA patients. Further, when admission did occur, it was generally unrelated to cardiac or respiratory events. In this retrospective analysis, the preoperative diagnosis of OSA was not a risk factor for either unanticipated hospital admission or for other adverse events among patients undergoing outpatient surgical procedures in a tertiary referral center. ⋯ In patients scheduled for outpatient surgery in a large academic practice, the diagnosis of obstructive sleep apnea confirmed by polysomnography was not an independent risk factor for unanticipated hospital admission or for other adverse perioperative events.
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Anesthesia and analgesia · May 2003
Randomized Controlled Trial Comparative Study Clinical TrialRecovery of neuromuscular function after cardiac surgery: pancuronium versus rocuronium.
The use of pancuronium in fast-track cardiac surgical patients may be associated with delays in clinical recovery. Our objective in this study was to evaluate the incidence and severity of residual neuromuscular blockade after cardiac surgery in patients randomized to receive either pancuronium (0.08-0.1 mg/kg) or rocuronium (0.6-0.8 mg/kg). Eighty-two patients undergoing cardiopulmonary bypass were randomized to a pancuronium (n = 41) or rocuronium (n = 41) group. Intraoperative and postoperative management was standardized. In the intensive care unit, train-of-four (TOF) ratios were measured each hour until weaning off ventilatory support was initiated. Neuromuscular blockade was not reversed. After tracheal extubation, patients were examined for signs and symptoms of residual paresis. When weaning of ventilatory support was initiated, significant neuromuscular blockade was present in the pancuronium subjects (TOF ratio: median, 0.14; range, 0.00-1.11) compared with the rocuronium subjects (TOF ratio: median, 0.99; range, 0.87-1.21) (P < 0.05). Patients in the rocuronium group were more likely to be free of signs and symptoms of residual paresis than patients in the pancuronium group. Our findings suggest that the use of longer-acting muscle relaxants in cardiac surgical patients is associated not only with impaired neuromuscular recovery, but also with signs and symptoms of residual muscle weakness in the early postoperative period. ⋯ The use of long-acting muscle relaxants in fast-track cardiac surgical patients is associated with significant residual neuromuscular block in the intensive care unit, including signs and symptoms of residual paresis.