Anaesthesia
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The primary goal of this study was to determine the median effective dose (ED50 ) of spinal chloroprocaine for labour analgesia. Thirty-eight parturients requesting neuraxial analgesia were enrolled. ⋯ Effective analgesia was defined as a score ≤ 10 mm within 15 min on a 100-mm visual analogue pain scale. Using the isotonic regression estimator method, the ED50 of chloroprocaine for the spinal component of a combined spinal-epidural for labour was calculated to be median (95%CI) 12.0 (9.3-17.0) mg.
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Randomized Controlled Trial
A randomised double-blind trial of phenylephrine and metaraminol infusions for prevention of hypotension during spinal and combined spinal-epidural anaesthesia for elective caesarean section.
Metaraminol infusion for hypotension prevention during spinal anaesthesia for Caesarean section is non-inferior to phenylephrine infusion.
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Observational Study
Effects of acute controlled changes in end-tidal carbon dioxide on the diameter of the optic nerve sheath: a transorbital ultrasonographic study in healthy volunteers.
Transorbital ultrasonographic measurement of the diameter of the optic nerve sheath is a non-invasive, bed-side examination for detecting raised intracranial pressure. However, the ability of the optic nerve sheath diameter to predict acute changes in intracranial pressures remains unknown. The aim of this study was to examine the dynamic changes of the optic nerve sheath diameter in response to mild fluctuations in cerebral blood volume induced by changes in end-tidal carbon dioxide. ⋯ With hypercapnia, there was a significant increase in optic nerve sheath diameter, with a mean (SD) increase from baseline 4.2 (0.7) mm to 4.8 (0.8) mm; p < 0.001. On return to normocapnia, the optic nerve sheath diameter rapidly reverted back to baseline values. This study confirms dynamic changes in the optic nerve sheath diameter with corresponding changes in carbon dioxide, and their reversibly with normocapnia.
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Randomized Controlled Trial
Sevoflurane-induced isoelectric EEG and burst suppression: differential and antagonistic effect of added nitrous oxide.
The objective of this study was to investigate whether nitrous oxide influenced the ED50 of sevoflurane for induction of isoelectric electroencephalogram (ED50isoelectric ) differently from its influence on the ED50 of sevoflurane for electroencephalogram burst suppression (ED50burst ). In a prospective, randomised, double-blind, parallel group, up-down sequential allocation study, 77 ASA physical status 1 and 2 patients received sevoflurane induction and, after tracheal intubation, were randomly allocated to receive sevoflurane with either 40% oxygen in air (control group) or 60% nitrous oxide in oxygen mixture (nitrous group). The ED50isoelectric in the two groups was determined using Dixon's up and down method, starting at 2.5% with 0.2% step size of end-tidal sevoflurane. ⋯ The values for ED50burst were 3.05 (95%CI, 2.66-3.90)% and 3.02 (95%CI, 3.00-3.05)% in nitrous group and control group, respectively (p = 0.52). The addition of 60% nitrous oxide increases ED50isoelectric , but not the ED50burst of sevoflurane. Neither result indicates an additive effect of anaesthetic agents, as might be expected, and possible reasons for this are discussed.