British journal of anaesthesia
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Randomized Controlled Trial Clinical Trial
MAC reduction of isoflurane by sufentanil.
We have shown previously that a plasma fentanyl concentration of 1.67 ng ml-1 reduced the MAC of isoflurane by 50%. By comparing equal degrees of MAC reduction by sufentanil, we may determine the potency ratio of these opioids. Seventy-six patients were allocated randomly to receive predetermined infusions of sufentanil, and end-tidal concentrations of isoflurane in oxygen. ⋯ The MAC reduction of isoflurane produced by sufentanil was obtained using a logistic regression model. A sufentanil plasma concentration of 0.145 ng ml-1 (95% confidence limits 0.04, 0.26 ng ml-1) resulted in a 50% reduction in the MAC of isoflurane. At a plasma concentration greater than 0.5 ng ml-1, sufentanil exhibited a ceiling effect.
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Randomized Controlled Trial Comparative Study Clinical Trial
Cricoid pressure impedes placement of the laryngeal mask airway and subsequent tracheal intubation through the mask.
We have studied 40 patients to see if cricoid pressure affects the success rate of ventilation through, and the position of, the laryngeal mask and subsequent fiberscope-aided tracheal intubation. Adequate ventilation of the lungs was produced through the laryngeal mask in 19 of 20 patients in the control group, but in only 10 of 20 patients in the cricoid pressure group (P < 0.002). ⋯ Release of cricoid pressure after placement of the laryngeal mask improved the view of the glottis, but tracheal intubation was still difficult because of laryngeal deviation. These results show that cricoid pressure impedes placement of the laryngeal mask and subsequent fiberscope-aided tracheal intubation.
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Randomized Controlled Trial Clinical Trial
Retrobulbar block fails to prevent an increase in serum cortisol concentration on emergence from anaesthesia after cataract surgery.
We have studied 30 elderly patients undergoing cataract surgery, allocated randomly to receive general anesthesia, local anaesthesia by retrobulbar block or general anaesthesia combined with retrobulbar block given after induction. Retrobulbar block alone prevented the increases in circulating cortisol and glucose values which occurred in those patients receiving general anaesthesia alone. Retrobulbar block given after induction of general anaesthesia, however, suppressed the cortisol and glucose response during surgery, but did not prevent a marked increase in cortisol concentrations during the immediate postoperative period. The results suggest a hormonal response to emergence from anaesthesia which has hitherto been masked by the stress response to surgery itself.
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Randomized Controlled Trial Clinical Trial
Nitrous oxide does not influence operating conditions or postoperative course in colonic surgery.
We studied 150 patients undergoing elective colonic surgery; they were allocated randomly to undergo artificial ventilation with either air-oxygen or nitrous oxide-oxygen during surgery. Eleven patients were excluded. Preoperative management, surgery and postoperative analgesia were similar in both groups. ⋯ The air-oxygen group required a continuous infusion of propofol of 4-6 mg kg-1 h-1 whereas the nitrous oxide-oxygen group required only 1-2 mg kg-1 h-1. There were no differences between the groups in duration of anaesthesia, distension of the bowel and postoperative bowel function. The postoperative hospital stay was similar for both groups.
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Randomized Controlled Trial Clinical Trial
Optimum dose of neostigmine at two levels of atracurium-induced neuromuscular block.
There is controversy about the optimum dose of neostigmine for antagonizing neuromuscular block. We have studied 57 patients undergoing gynaecological surgery to establish a dose-response relationship when neostigmine was given to antagonize atracurium-induced block. Anaesthesia was induced with thiopentone and fentanyl and maintained with nitrous oxide and enflurane in oxygen and neuromuscular block was produced with a bolus of atracurium 0.5 mg kg-1. ⋯ There was little benefit in increasing the dose of neostigmine from 40 micrograms kg-1 to 80 micrograms kg-1 when antagonizing profound neuromuscular block. When light block was antagonized, neostigmine 20 micrograms kg-1 was the optimum dose. We suggest that smaller doses of neostigmine than are given commonly produce adequate antagonism of atracurium-induced neuromuscular block.