[Analgesia and sedation in intensive care patients]

Analgesia and sedation with the associated reduction of undesired vegetative reactions are important components in the therapeutic regimen of intensive care patients. None of the sedative drugs available can fulfil every one of the criteria expected of an "ideal" sedative. Four commonly used drug combinations have been established as standards: 1. opioid and neuroleptic, 2. opioid and benzodiazepine, 3. ketamine and benzodiazepine, and 4. opioid and propofol. In everyday use one must take not only the specific side-effects of a drug into consideration but also its pharmacokinetic properties. These are often markedly altered in critically ill patients who have impaired functions of vital organs. The pharmacokinetics of a drug is affected by disturbed renal or hepatic function, interactions with other drugs, altered protein binding and the induction or inhibition of metabolic enzymes. The best method of drug administration is by motor-driven pump, with which large fluctuations of the dosage can be avoided. Constant ratios of drug combinations are not recommended, since the pharmacokinetics of each drug is affected to a different degree in the critically ill patient. Withdrawal symptoms, can occur for example after prolonged administration of benzodiazepines, can often be avoided by slowly reducing the dose or by switching to a short-acting substance. In some patients (e.g. those with a history of alcohol abuse) a massive increase of the drug dose is not indicated when the effect is not adequate. Instead, an entirely different substance should be employed and the administration of less frequently used drugs should be considered. Despite detailed knowledge of the altered pharmacokinetics in critically ill patients, the drugs should be dosed as dictated by the situation, true to the anaesthesiologists' adage: "Dosage according to effect!"