Canadian Anaesthetists' Society journal
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The effects of anaesthetic agents, per se, on the asphyxiated foetus are difficult to quantitate clinically. Anaesthesia is often necessary in foetal distress, however, to effect a rapid delivery. To investigate the effect of general anaesthetic agents commonly used for Caesarean section we administered these agents to 18 chronically prepared pregnant ewes with asphyxiated foetuses in utero. ⋯ There were no significant differences between Groups B and C in foetal pH, PCO2, or PO2. Two foetuses in the nitrous oxide group died after ten minutes of anesthesia, but the aetiology of the sudden demise is unclear. We conclude that general anaesthesia abolishes the foetal response to umbilical cord occlusion and does not improve foetal oxygenation or acid-base status.
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Foetal heart rate and tocodynamic monitoring of the uterus was performed in five pregnant patients undergoing urgent or emergency surgery unrelated to their pregnancy. All received general anaesthesia with halothane or enflurane and nitrous oxide. ⋯ Since continuous intraoperative monitoring of foetal heart rate in pregnant patients is technically feasible during peripheral surgery and during many intra-abdominal procedures, attempts should be made to monitor foetal heart rate in all anaesthetized parturients to assure that the anaesthetic is not causing foetal insult. Postoperative monitoring of uterine tone is useful in the diagnosis and treatment of postoperative premature labor.
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The role of osmotic brain dehydration in the early reduction of intracranial pressure (ICP) following mannitol administration has recently been questioned and a decrease in cerebral blood volume (CBV) proposed as the mechanism of action. To evaluate this hypothesis, relative CBV changes before and after mannitol infusion were determined by collimated gamma counting across the biparietal diameter of the exposed skull in six dogs. Red blood cells were labelled with chromium-51. ⋯ The administration of saline, although associated with an increase in TBV (18 per cent), was not associated with any significant change in CBV, ICP, MAP or CVP. The increase in relative CBV persisted for 15 minutes after mannitol infusion, while the ICP returned to control within five minutes and continued to decrease. This study supports the fact that after rapid mannitol infusion, ICP begins to decrease only once the dehydrating effect has counteracted the increase in brain bulk caused by the increase in cerebral blood volume.
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Clinical Trial Controlled Clinical Trial
Epidural morphine prophylaxis of postoperative pain: report of a double-blind multicentre study.
In a double-blind placebo-controlled trial, 154 subjects, having intraperitoneal surgery or Caesarean section, and 53 patients undergoing lower limb orthopaedic surgery, received epidural morphine, 5 mg in 10 ml 0.9 per cent NaCl, or placebo, 10 ml 0.9 per cent NaCl, intraoperatively to determine duration of action and efficacy in preventing postoperative pain. Epidural morphine gave significantly longer postoperative analgesia (greater than 11 h) than placebo (3-6 h) in both groups (p less than 0.05) and patients who received morphine required less postoperative analgesic. Obstetric subjects experienced longer pain relief (18.3 +/- 1.3 h) than patients undergoing non-obstetric intraperitoneal surgery (9.2 +/- 1.2 h) (p less than 0.001). ⋯ Respiratory depression occurred in 2-7 per cent of subjects who received morphine; unpredictable in onset, it responded rapidly to naloxone. Epidural bupivacaine, if employed for the surgical procedure, appeared to prolong epidural morphine analgesia. We consider epidural morphine useful in preventing postoperative pain, but its use demands close observation of respiratory rate in a high density nursing area.