Anaesthesia
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Clinical Trial Controlled Clinical Trial
Accuracy of pulse oximetry in patients with low systemic vascular resistance.
In order to assess the accuracy of pulse oximeters in patients with septic shock, we compared 80 paired readings of oxygen saturations taken from pulse oximeters and oxygen saturations obtained from co-oximetry in patients receiving intensive therapy with indwelling pulmonary artery flotation catheters. Comparison between groups with low or normal systemic vascular resistance indices showed a small (1.4%) but significant (p < 0.001) underreading of the saturation from the pulse oximeter in the presence of a low systemic vascular resistance. With normal or high systemic vascular resistance pulse oximeter readings correlated well with co-oximetry. We hypothesise that the main cause of this underreading is because the pulse oximeter is sensing pulsatile venous flow due to the opening of arteriovenous channels in the skin in septic states.
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We have followed the progress of 12 anaesthetic trainees as they learnt how to perform fibreoptic nasotracheal intubation with the aid of an endoscopic video camera system. Each trainee had a structured teaching session on a bronchial tree model, viewed an instructional videotape and then performed 20 nasotracheal intubations on anaesthetised oral surgery patients. Trainees were required to perform the endoscopies under full visual control and to demonstrate airway anatomy as they advanced the fibrescope. ⋯ The best fit value for the first endoscopy time was 132s, and after the 18th (two half-lives) it was 49 s. We analysed the theoretical basis for deriving a learning curve from raw data. This information could form a rational basis for the design of fibreoptic training programmes using video imaging systems.
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Randomized Controlled Trial Comparative Study Clinical Trial
Serum glutathione S-transferase concentrations and creatinine clearance after sevoflurane anaesthesia.
The effects of sevoflurane and isoflurane on serum glutathione S-transferase concentrations and creatinine clearance were compared in 50 ASA I-III patients aged over 18 years undergoing body surface surgery of 1-3 h predicted duration. Patients randomly received sevoflurane (n = 24) or isoflurane (n = 26) in nitrous oxide and oxygen (FIO2 = 0.4) via a nonrebreathing system. ⋯ Patients received significantly less (p < 0.05) sevoflurane (1.0 MAC-h) than isoflurane (1.5 MAC-h). Using serum glutathione S-transferase concentrations and creatinine clearance as markers of hepatic and renal function respectively, no statistically significant differences were identified between the groups.
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Randomized Controlled Trial Clinical Trial
Effect of the size of a tracheal tube and the efficacy of the use of the laryngeal mask for fibrescope-aided tracheal intubation.
We randomly allocated 60 patients with normal airways into three groups to compare the ease of fibrescope-aided tracheal intubation using 8.0-mm internal diameter (group F8) and 6.0-mm (group F6) reinforced tracheal tubes and to evaluate the efficacy of the laryngeal mask as an aid for fibreoptic tracheal intubation (group L). In group F8 tracheal intubation was optimal in 2 of 20 patients and in two patients in whom intubation over the fibrescope was difficult the attempts resulted in inadvertent oesophageal intubation. ⋯ In both groups F6 and L tracheal intubation was completed within less than about 1 min. We conclude that conventional fibrescope-aided tracheal intubation with a 6.0-mm tracheal tube is easier than with an 8.0-mm tube and that the laryngeal mask facilitates fibrescope-aided tracheal intubation.
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Comparative Study Clinical Trial Controlled Clinical Trial
A comparison of the Invos 3100 and the Critikon 2020 near-infrared spectrophotometers as monitors of cerebral oxygenation.
Assessment of cerebral oxygenation using near-infrared spectroscopy in intensive care is increasing. We compared the ability of the Invos 3100 and the Critikon 2020 monitors to produce stable and consistent readings of regional cerebral oxygen saturation in resting volunteers. Failure to obtain any stable reading with the Critikon occurred in eight out of 18 subjects (44.4%) and with the Invos in three out of 15 subjects (20%). ⋯ The within-monitor variability was significantly higher for the Invos (p = 0.0124). Neither monitor is able to give stable and consistent readings over time, particularly in male subjects. The unacceptably high failure rate of the recently introduced Critikon 2020 will limit or prevent its clinical use.