Anaesthesia
-
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.
-
Randomized Controlled Trial Comparative Study
A randomised crossover simulation study comparing the impact of chemical, biological, radiological or nuclear substance personal protection equipment on the performance of advanced life support interventions.
Recent incidents involving chemical, biological, radiological and nuclear substances have stressed the importance of sufficient personal protection equipment for medical first-responders. Modern lightweight, battery-independent, suit ensembles may prove superior to the current protective suit used in the UK. This study compared the powered respiratory protective suit (PRPS ensemble) with a lightweight suit consisting of a SARATOGA® Multipurpose CBRN Protective Coverall Polyprotect 12 in conjunction with the Avon C50 Respirator/Avon CBRNF12CE filter canister and butyl rubber protective gloves (Polyprotect 12 ensemble). ⋯ Total mean (SD) completion time for the five interventions was significantly longer for the PRPS compared with the Polyprotect 12 ensemble (204 (53) s vs. 149 (36) s, respectively; p < 0.0001). Participants rated mobility, noise, heat, vision, dexterity and speech intelligibility significantly better in the Polyprotect 12 ensemble compared with the PRPS ensemble. The combination of a lightweight Polyprotect 12 suit and an Avon C50 air-purifying respirator is preferable to the powered respiratory protective suit during simulated emergency life support, due to a combination of shorter task completion times and improved mobility, communication and dexterity.
-
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.