British journal of anaesthesia
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Comparative Study Clinical Trial Controlled Clinical Trial
Comparison of bispectral index, 95% spectral edge frequency and approximate entropy of the EEG, with changes in heart rate variability during induction of general anaesthesia.
We have compared bispectral index (BIS), 95% spectral edge frequency (SEF) and approximate entropy (ApEn) in 37 patients during induction and recovery from a short general anaesthetic. Heart rate variability (HRV) was also compared during induction only. These indices were noted at the start of induction, when a syringe held between the thumb and fingertips was dropped, at insertion of a laryngeal mask or tracheal tube (tube insertion), at incision, at the end of surgery, on return of the gag reflex and when the patient could follow a verbal command. ⋯ Using logistic regression, the indices were compared both individually and in combination as to the power of distinguishing awake (at pre-induction) from asleep (at tube insertion) states. BIS had the best predictive power, with a sensitivity of 97.3%, specificity 94.4%, positive predictive value 94.7% and negative predictive value 97.1%. A combination of the indices conferred no additional predictive advantage.
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We measured directly mucosal pressures against the cuff and non-cuff portions of the tracheal tube in different head-neck positions and tested the reliability of calculated mucosal pressures, in vivo intracuff pressures and cuff volume as determinants of directly measured mucosal pressures. We studied 10 anaesthetized, paralysed adult patients. An 8.5-mm, high volume, low pressure PVC tracheal tube was used. ⋯ In vivo intracuff pressures and calculated mucosal pressures were moderate predictors of measured mucosal pressures; cuff volume was a poor predictor. We conclude that tracheal mucosal pressures were highest anteriorly, that non-cuff portions of the tube exerted substantial mucosal pressures and that the rotated position caused a greater increase in tracheal mucosal pressure than the extended or flexed position. Indirect methods of measuring mucosal pressure were of moderate predictive value.
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Editorial Comment Historical Article
'The only man to have all his work done by Friday was Robinson Crusoe' (anon)
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Comment Letter Case Reports
Anaesthesia for caesarean section in severe pulmonary hypertension.