British journal of anaesthesia
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The effect of thumb preload on adductor pollicis muscle compound action potential (ECAP) was assessed after supramaximal ulnar nerve stimulus during steady isoflurane anaesthesia in 20 ASA I-II patients without neuromuscular block. During thumb preload, the peak-to-peak amplitude of the ECAP increased by 0.9 mV, to 9.5 (SD 2.2) mV (P < 0.01), because of the increased height of the negative half-wave. ⋯ Without preload, the first dorsal interosseus muscle peak-to-peak amplitude was 13.0 (4.3) mV. Thus thumb preload may not be the solution to improved monitoring of neuromuscular block by ECAP.
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Ten patients were studied for each of the sizes 2, 3 and 4 laryngeal mask airways (LMA) in order to calculate the pressure exerted by the cuff upon the pharyngeal mucosa. Using a non-invasive method of comparing intracuff pressures recorded both in vitro and in vivo, the transmitted pharyngeal mucosal pressures were calculated over the clinical range of injection volumes. ⋯ The intracuff pressures recorded with the mask in situ at these normal injection volumes were in the range 103-251 mm Hg. The calculated transmitted mucosal pressures were substantial for all three sizes of cuff and potentially exceeded the capillary perfusion pressure of the adjacent pharyngeal mucosa, despite apparent pharyngeal accommodation to the mask.
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Previous studies have reported that malignant hyperthermia susceptibility is caused in some families by inherited variation in a gene located on the short arm of chromosome 19 near to, or identical with, the ryanodine receptor gene (RYR1); this is expressed in skeletal muscle as a calcium release channel of the sarcoplasm reticulum. In other families, a gene in this location is excluded, but the locations of the genes involved have not yet been defined. ⋯ The results presented here strongly suggest that the gene for malignant hyperthermia susceptibility in one or more of these three British families is located in the same region of chromosome 19q, although further work is required to decide whether or not the RYR1 gene itself is causative in these families. As genetic heterogeneity could not be excluded, we cannot yet recommend the use of DNA markers to replace in vitro contracture tests in the diagnosis of malignant hyperthermia susceptibility.
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Case Reports
Use of esmolol in the postbypass management of hypertrophic obstructive cardiomyopathy.
In patients suffering from hypertrophic obstructive cardiomyopathy (HOCM), any catecholamine release during anaesthesia may aggravate the severity of the outflow tract obstruction and compromise cardiac output. In this event the situation may be improved by beta block. Esmolol, an ultra-short-acting beta-blocker (half-life 9 min) appears to be a suitable agent for this purpose. We describe its use in the perioperative management of a patient who underwent surgical correction of HOCM.
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Randomized Controlled Trial Comparative Study Clinical Trial
Preoperative drinking does not affect gastric contents.
We have compared the effect of allowing free clear fluids until the time of oral premedication with conventional preoperative fasting. In a prospective, randomized trial, the residual volume and pH of gastric contents after induction of anaesthesia were measured in 100 elective surgical patients allocated randomly to a group in whom the intake of free clear fluids up to the time of premedication was measured (mean 388 ml in 6 h before surgery) or a control group who were fasted for 6 h. ⋯ Problems with aspiration or regurgitation were not encountered. We believe that allowing elective surgical patients to drink clear fluids until 2 h before anaesthesia may enhance patient comfort without compromising safety.