Articles: anesthetics.
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Comparative Study Clinical Trial Controlled Clinical Trial
Intraocular pressure changes during rapid sequence induction of anaesthesia: comparison of propofol and thiopentone in combination with vecuronium.
Intraocular pressure (IOP) was measured during rapid sequence induction of anaesthesia using thiopentone or propofol as the induction agent and vecuronium for neuromuscular blockade. Vecuronium was administered in a dose of 0.15 mg kg-1 approximately 35 s before the induction agent. IOP was measured with a handheld applanation tonometer before anaesthesia, following administration of the induction agent, immediately after tracheal intubation and cuff inflation and 1, 2 and 3 min later. ⋯ IOP following intubation in patients in whom anaesthesia was induced with thiopentone was not significantly different from baseline values, but showed a significant increase from the pressure before intubation. In contrast, IOP after intubation in the propofol group remained not only significantly less than the baseline value, but also showed only a minimal and insignificant change in comparison with values before intubation. The frequency of side effects was low in both groups except for a significantly greater reduction in arterial pressure in those receiving propofol.
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Cerebral blood flow, cerebral oxygen consumption, lactate and glucose metabolism were measured in 13 patients during anaesthesia with nitrous oxide, oxygen and enflurane 0.5% and after 30 minutes infusion of propofol. The mean blood concentration of propofol was 4.06 micrograms/ml. ⋯ Cerebral oxygen consumption decreased by 18.25%. Changes in the electro-encephalograph were related to the blood levels of propofol.
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Twenty patients, ASA grades 1 and 2, aged 18-65 years were admitted to an open study to investigate the ease of tracheal intubation after induction of anaesthesia with propofol without the use of muscle relaxants after the chance observation that propofol 2.5 mg/kg allowed easy laryngoscopy and tracheal intubation. Satisfactory intubation conditions were achieved in 19 patients.
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The effects of a bolus injection of propofol on mean intracranial pressure were studied in six adult, comatose patients who had severe head injuries. Propofol 2 mg/kg was given intravenously over 90 seconds when the mean intracranial pressure reached or exceeded 25 mmHg. Arterial blood gas values, heart rate and central venous pressure remained stable at all measurements. ⋯ The mean (SEM) intracranial pressure decreased statistically significantly (p less than 0.05) at 30 seconds and at 1 and 2 minutes, from 25 (3) to 11 (4) mmHg. The cerebral perfusion pressure decreased statistically significantly from 92 (8) mmHg at all measurements (p less than 0.05). The lowest value at 3 minutes was 50 (7) mmHg but in four patients at that time the perfusion pressure was below 50 mmHg.
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The pharmacokinetics of a constant rate infusion of propofol were studied in 11 patients who received total intravenous anaesthesia for ENT surgery. Alfentanil was administered as an exponentially decreasing infusion using a computer-assisted infusion device with a constant target plasma alfentanil concentration of 300 ng/ml. Propofol was infused at a constant rate of 6 mg/kg/hours. ⋯ Only three data sets were significantly underestimated after the infusion was stopped (mean bias 11.9% (SD 25.5]. The elimination half-life of alfentanil was approximately 75 minutes (SD 21). We conclude that alfentanil does not interfere with the pharmacokinetic profile of propofol but that propofol induces higher plasma alfentanil concentrations than expected.