British journal of anaesthesia
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Randomized Controlled Trial Comparative Study Clinical Trial
Maternal inspired oxygen concentration and neonatal status for caesarean section under general anaesthesia. Comparison of effects of 33% or 50% oxygen in nitrous oxide.
The relationship between maternal FIO2 and umbilical venous PO2, PCO2, pH and neonatal Apgar and TSR (time to sustained respiration) scores was studied in 35 patients undergoing Caesarean section under general anaesthesia. Patients were allocated randomly to breathe an FIO2 of either 0.5 or 0.33. ⋯ No differences were found between groups for 1- or 5-min Apgar scores or TSR values. It is concluded that no difference in fetal outcome or acid-base status can be detected when maternal FIO2 is decreased from 0.5 to 0.33, and that the use of 33% oxygen in 66% nitrous oxide appears to be safe for neonates who have not suffered fetal distress before delivery.
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Comparative Study
Potency of atracurium and vecuronium at the diaphragm and the adductor pollicis muscle.
Train-of-four stimulation was applied to the ulnar and phrenic nerves in 18 adult patients anaesthetized with nitrous oxide and halothane in oxygen. The response of the adductor pollicis and the diaphragm were measured. Incremental doses of atracurium and vecuronium were given, with an infusion to replace drug lost by elimination or distribution. ⋯ The mean (SEM) ED50 ratios were 1.56 (0.16) for atracurium and 1.47 (0.16) for vecuronium. ED90 ratios were 1.93 (0.29) and 1.55 (0.17) for atracurium and vecuronium, respectively. It is concluded that both atracurium and vecuronium exhibit a similar degree of sparing of the diaphragm.
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Randomized Controlled Trial Comparative Study Clinical Trial
Maximum FIO2 during caesarean section.
Forty patients undergoing elective and emergency Caesarean section (excluding severe fetal distress) were divided into four groups to receive 50% oxygen, 50% nitrous oxide, and 0.5% halothane (group 1, controls) or 100% oxygen supplemented by 1.5 x MAC of halothane, enflurane or isoflurane (groups 2,3,4, respectively) reducing to 1.0 x MAC 5 min after induction. The umbilical venous PO2 in the oxygen-only groups was higher than in the oxygen-nitrous oxide groups, this difference reaching statistical significance when the patients in the oxygen-only groups were combined. ⋯ Improved cardiovascular stability was demonstrated in the elective high-oxygen groups. The technique is safe and warrants further study, since there are no important ethical objections.
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Comparative Study
Comparison of neuromuscular blockade in the diaphragm and the hand.
Neuromuscular blockade was recorded in the diaphragm and in the adductor pollicis muscle using unilateral supramaximal stimulation of phrenic and ulnar nerves and measurement of the mechanical effect of each. After administration of atracurium 0.4-0.5 mg kg-1 to 10 patients, both onset and recovery of neuromuscular blockade in the diaphragm occurred before that in adductor pollicis and there was a linear relationship between recovery in diaphragm and adductor pollicis. After administration of vecuronium 0.08-0.1 mg kg-1 to a further 10 patients, paralysis occurred in the diaphragm before adductor pollicis in all except one patient, in whom it occurred simultaneously. Reappearance of adductor pollicis twitch occurred in six patients after all four twitches had returned in the diaphragm, but the rate of recovery of twitch height in the diaphragm was more rapid than in adductor pollicis in every patient.
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A mother with the Klippel-Feil syndrome, congenital hydrocephalus and increased intracranial pressure presented for delivery by Caesarean section at 33 weeks because of pre-eclampsia. Anaesthetic management comprised awake intubation using the fibreoptic bronchoscope, followed by induction and maintenance of general anaesthesia for the delivery of a live male infant. This case report describes the problems arising under these circumstances and the relative merits of different anaesthetic techniques.