British journal of anaesthesia
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Randomized Controlled Trial Clinical Trial
Nitrous oxide-mediated activation of the EEG during isoflurane anaesthesia in patients.
We have studied the effects of nitrous oxide on EEG burst suppression patterns during stable isoflurane anaesthesia in 13 ASA I patients. After induction of anaesthesia with propofol, the concentration of isoflurane was increased with continuous EEG monitoring to burst suppression level (mean end-tidal concentration of isoflurane, 1.7 (SD 0.2)%), and kept constant during the study. During surgery, isoflurane in air and oxygen (FIO2 0.35), or isoflurane in 65% nitrous oxide in oxygen were given to each patient for 30 min, in random order. ⋯ The proportion of EEG suppression time was measured after a washin or washout period of at least 15 min for nitrous oxide. There was a significant decrease in the proportion of EEG suppression time (from 69.5 to 43.7%) when air was replaced by nitrous oxide. We conclude that the EEG effects of isoflurane and nitrous oxide are not additive and that nitrous oxide opposes the depression of isoflurane on the central nervous system.
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Thirty-two women underwent major gynaecological surgery with a midazolam-alfentanil total i.v. anaesthetic regimen. Adequacy of anaesthesia was assessed using a "pressure, rate, sweating and tears" (PRST) scoring system in conjunction with the isolated forearm technique (IFT). The IFT revealed that 72% of patients responded during surgery, but none had spontaneous, unprompted postoperative recall for the event. ⋯ Twenty patients, asked specifically during surgery to indicate the presence or absence of pain, experienced pain at some time during their surgical procedure. The PRST score could not be used to predict when a patient was awake. This low-dose i.v. anaesthetic technique cannot be recommended for general use.
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Randomized Controlled Trial Clinical Trial
Use of alfentanil with propofol for nasotracheal intubation without neuromuscular block.
We have investigated the effect of augmentation of propofol with alfentanil for nasotracheal intubation without neuromuscular block in 60 patients undergoing short elective maxillo-facial procedures as outpatients. After administration of glycopyrronium 5 micrograms kg-1 i.v., anaesthesia was induced with propofol 2.5 mg kg-1, or alfentanil 20 micrograms kg-1 and propofol 2.5 mg kg-1. ⋯ This difference was not significant. The cardiovascular response to intubation was attenuated in the alfentanil group.
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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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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.