British journal of anaesthesia
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Comparative Study
Propofol for induction and maintenance of anaesthesia: comparison between younger and older patients.
The propofol requirements for the induction and maintenance of anaesthesia were compared in groups of younger and older patients. Side effects, influence on the cardiovascular system and recovery times were compared between 20 unpremedicated ASA I-III, 25-40-yr-old patients and 20 65-80-yr-old patients all scheduled to undergo elective surgery. After induction with propofol, anaesthesia was maintained with a continuous infusion of the drug. ⋯ Side effects were more pronounced in the younger patients. Influences on the cardiovascular system were definite, but mild. The younger patients awoke sooner: 7.8 v. 14.3 min (P less than 0.01) after the discontinuation of the infusion of propofol.
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The usefulness of measuring respiratory flow in the airway and at the chest wall and of measuring respiratory input impedance (Z) to monitor high frequency ventilation was investigated by computer simulation using a monoalveolar 10-coefficient model. The latter included a central airway with its resistance (Rc) and inertance (lc), a resistive peripheral airway (Rp), a lumped bronchial compliance (Cb), alveolar gas compliance (Cgas), lung tissue with its resistance (RL) and compliance (CL), and chest wall resistance (RW), inertance (lw) and compliance (Cw). Gas flow in the peripheral airway (Vp), shunt flow through Cb (Vb), gas compression flow (Vgas) and rate of volume change of the lung (VL) and of the chest (VW) were computed and expressed as a function of gas flow in the central airway (Vc). ⋯ A reduced lung or chest wall compliance produced little change in Vp/Vc and Z except at very low frequencies; however, it decreased the phase lag between Vw and Vc. Finally, an increased airway wall compliance decreased Vp/Vc, but had little effect on Z and Vw/Vc. It is concluded that measuring respiratory impedance may help in detecting some, but not all of the conditions in which peripheral flow convection is decreased during high frequency oscillations.
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The influence of renal failure on the disposition of morphine and its metabolites was studied in nine patients with end-stage renal failure undergoing transplantation, and compared with five healthy anaesthetized patients. All patients received morphine sulphate pentahydrate 10 mg i.v. over 30 s, as part of a balanced anaesthetic technique. Venous blood samples were collected for up to 24 h, and plasma concentrations of morphine, morphine-3-glucuronide (M3G), and morphine-6-glucuronide (M6G) assayed by a differential radioimmunoassay method. ⋯ However, the volume of distribution at steady state was greater in the control group (241 litre v. 141 litre; P = 0.002). The peak concentrations of M3G and M6G were greater in the renal transplant patients (P = 0.001 and P = 0.01, respectively), as were the AUC (0-24 h) (P = 0.002 and P = 0.002). M6G has been shown to possess analgesic properties in both man and experimental animals, and therefore the increased AUC for M6G may contribute to the prolonged effect seen with morphine when given to patients with impaired renal function.
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Randomized Controlled Trial Comparative Study Clinical Trial
In vivo assessment of percutaneous local anaesthetic preparations.
This study has demonstrated greater efficacy of a new percutaneous amethocaine preparation relative to Eutectic Mixture of Local Anaesthetics (EMLA). Initially, a double-blinded trial was undertaken on each preparation individually against placebo, as the recommended method of application was different for EMLA (2.5 g applied for 60 min under an occlusive dressing) and the amethocaine formulation (0.5 g applied for 30 min). Thereafter, the two preparations were compared directly, in a double-blinded study using a standardized application for both formulations. ⋯ The amethocaine preparation produced significant anaesthesia (chi-square, P less than 0.001) after 30 min application. Furthermore, the amethocaine formulation demonstrated both increased rapidity of action and increased duration of effect, as determined by a two-tailed unpaired t test, in comparison with EMLA when application times of both 30 and 60 min were used for each preparation. The results of this study indicate that the amethocaine preparation provided more rapid and prolonged anaesthesia than EMLA.