British journal of anaesthesia
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Randomized Controlled Trial Comparative Study Clinical Trial
Effect of naloxone on the loss of consciousness induced by i.v. anaesthetic agents in man.
The effect of a specific opioid antagonist, naloxone, was studied in two comparable groups of patients who received i.v. the dose of an anaesthetic agent required to produce loss of consciousness in 50% of subjects. The first group received naloxone 0.006 mg kg-1 5 min before induction of anaesthesia; the second group received a similar volume of saline solution. ⋯ The differences in percentage of unconscious patients between the naloxone-treated group and the control group were statistically significant for diazepam, ketamine and propanidid. Naloxone did not modify the induction of anaesthesia with thiopentone or Althesin.
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The venous plasma concentration-time profiles of thiopentone were measured simultaneously over the first 30-40 min after induction of anaesthesia, in blood obtained from an arm vein and a vein in the foot, in nine healthy full-term women undergoing Caesarean section. Patients were tilted laterally to the left by from 8 to 18 degrees during the procedure. In all but two of the patients, the profiles from the arm and foot were virtually identical, suggesting that aortocaval compression was absent or insignificant. Therefore, the large intersubject variability in volume of distribution of thiopentone at Caesarean section is unlikely to be the result of aortocaval compression.
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Seventy-five patients requesting extradural analgesia for the relief of pain in labour underwent an ultrasound scan to measure the depth to the extradural space. There was a high degree of correlation between these measurements and the subsequent depth of insertion of the Tuohy needle. The advantages of the technique in clinical practice and as an aid to teaching, are discussed.