Post-operative central anticholinergic syndrome.

Central anticholinergic syndrome is defined as an abDiagnosis rests on clinical features, exclusion of other conditions, and a positive response to a solute or relative reduction in cholinergic activity in centrally acting cholinesterase inhibitor, usually the central nervous system [1]. In anaesthetic practice physostigmine [1]. the syndrome was originally described in connection The incidence of the post-operative syndrome has with drugs with central anticholinergic actions, such as been estimated as 9.4% after general anaesthesia and hyoscine butylbromide (scopolamine) [2]. Later, many 3.3% after regional anaesthesia with sedation [1], other drugs with no direct anticholinergic effects were although an incidence as high as 40% has been implicated. This may be by modulation of other neuroclaimed [5]. In their paper in this issue of the journal [6], transmitters which reduce cholinergic activity, but the Link et al. report an incidence of 1.9% in a broad mechanisms by which the syndrome occurs have not mix of 962 adults after general anaesthesia, with a been fully explained [1]. subgroup of women recovering from major gynaeThe reported clinical features of the central anticological surgery having an incidence of 10%. These cholinergic syndrome in the post-operative period are figures are in stark contrast with experience in the UK non-specific. If they are all components of the synwhere central anticholinergic syndrome is diagnosed drome the central nervous system would be widely rarely. United Kingdom anaesthetists are either uninvolved (Table 1). There are said to be two forms of aware of the syndrome, or do not believe it exists. the syndrome: hyperactive or depressed. Peripheral Choice of anaesthetic technique and drugs may anticholinergic symptoms may also occur but could be an important determinant of reported incidence. by masked by peripheral cholinesterase inhibitors. Anaesthetists who use long acting drugs (benzodiazepines or barbiturates) will see a large number of Table 1. Reported clinical features of post-operative patients who recover slowly from anaesthesia. Link et central anticholinergic syndrome al. state that less than 3% of their study population were given droperidol as part of their anaesthetic, Agitation Emotional instability but eight of 18 patients with the syndrome received Amnesia Muscular inco-ordination or between 2.5 and 25 mg. The total number of patients weakness given diazepam and phenobarbitone premedication is Ataxia Nausea and vomiting not stated, but nine of 18 affected patients received Asynergia Hyperpyrexia one of these drugs. What constitutes normal recovery Dysarthria Hyperalgesia Clouded Sensorium Convulsions from anaesthesia and a definition of what is abConfusion Opisthotonus∗ normally prolonged are not stated. Clearly, the earlier Excitement Torticollis∗ that features of the syndrome are sought the higher Somnolence Tetraplegia† will be their incidence in the post-operative period. Coma Stimulation or depression of Interindividual variations in anaesthetic drugs and ventilation technique, as well as variations in pharmacokinetics Apprehension Stereotyped movements and pharmacodynamics, must also be taken into acHallucinations Fatigue count. Illusions/delusions Diminished power of concentration Delirium Medium or long term mental From the clinical features it is obvious that the impairment list of differential diagnoses is long. As there is no Paranoia Decreased reaction times diagnostic test, the diagnosis is made by exclusion EEG-behaviour dissociation of hypoxia, hypercapnia, hyperthermia, hypothermia, urea and electrolyte and acid-base disturbances, enTable modified from Rupreht and Dworacek 1989 [1]. Other references: ∗ [3], †[4]. docrine abnormalities, and neurological disturbance