Anaesthesia and intensive care
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Small doses of epidural and intrathecal opioids produce effective and prolonged analgesia postoperatively, although the quality of analgesia does not differ from when conventional routes are used. The different opioids differ only in the speed of onset and duration of action, and in the incidence of side-effects. 'Minor' complications such as nausea, vomiting, pruritus and retention of urine are relatively common. ⋯ It is commoner after morphine and after intrathecal administration, and is also associated with advanced age, concomitant use of other central depressant drugs, respiratory disease and large doses. Because of the potentially lethal nature of this complication, it is recommended that the epidural and intrathecal routes of administration are used only when patients can be closely and constantly observed postoperatively.
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The degree of neuromuscular blockade that occurs in an individual patient following the administration of competitive neuromuscular blocking agents cannot be accurately predicted because of the large individual variation in the pharmacokinetics and pharmacodynamics of these agents. Without monitoring of the neuromuscular blockade, this unpredictability predisposes to the occurrence of residual curarisation with its potentially lethal consequences. Variable rate continuous infusion of a short-acting competitive neuromuscular blocking agent with monitoring of the neuromuscular blockade is a flexible and accurate method for maintaining a precise degree of neuromuscular blockade during prolonged surgical procedures which ensues reliable reversability of the residual neuromuscular blockade. A system for the continuous infusion of atracurium with manual monitoring of the neuromuscular blockade is described, together with the results of a study demonstrating its efficacy.
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Anaesth Intensive Care · Feb 1987
ReviewThe role of pharmacokinetics in anaesthesia: application to intravenous infusions.
Pharmacokinetic concepts describe the relationship between drug dose and resulting plasma concentration. A drug's pharmacokinetic profile can be described by distribution and elimination half-lives, initial volume of distribution, steady-state distribution volume, and metabolic and distributional clearance. ⋯ The most rapid method of achieving a constant plasma concentration involves using a variable rate of drug infusion that adjusts for the metabolic clearance and distribution of the drug. Computer-driven infusion pumps can be used to rapidly achieve, then maintain, constant plasma concentrations of a drug.