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Anaesthesia for drug misusing patients

Anaesthesia for drug misusing patients
Colin Berry
General points
  • In the United Kingdom around 1 in 4 of the population aged over 16 has taken an illegal drug at some stage (10 million people).
  • Misuse of street drugs is not isolated to inner cities and areas of social deprivation.
  • Consider drug misuse in all patients requiring emergency surgery and anaesthesia. An accurate drug history is unlikely to be forthcoming.
  • Drug misuse may contribute to a reduced conscious level even if other causes are present (especially trauma).
  • Drug addicts are exposed to high risks of infective complications associated with intravenous drug abuse. HIV (6% in London) and viral hepatitis (up to 60%) are commonest. Bacterial endocarditis is rare but serious, and associated with pulmonary abscesses, embolic phenomena from vegetations, and vasculitis.
  • Drugs in common use fall into four groups (see table). Combinations of drugs are common, often with alcohol.
Street drugs in common use
Drug Clinical signs
Cannabis Tachycardia, abnormal affect (e.g. euphoria, anxiety, panic or psychosis), poor memory and fatigue (chronic use)
Stimulants—cocaine, amphetamines, ecstasy Tachycardia, labile blood pressure, excitement, delirium, hallucinations, hyperreflexia, tremors, convulsions, mydriasis, sweating, hyperpyrexia exhaustion, coma
Hallucinogens—LSD, phencyclidine, ketamine Sympathomimetic, weakly analgesic, altered judgement and perceptions, toxic psychosis, dissociative anaesthesia
Opioids—morphine, heroin, opium Euphoria, respiratory depression, hypotension, bradycardia constipation pinpoint pupils, coma
Anaesthesia
  • High index of suspicion—especially in trauma.
  • Difficult venous access—intravenous drug users may be able to direct you to a patent vein. May need central venous cannulation or cut-down for relatively minor procedures. Consider gas induction.
  • Take full precautions against infection risk.
  • Plan postoperative analgesia with patient preoperatively—see below.
  • Resistance to opioids.

P.221


Opioid misusing patient
  • Patients who are misusing opioids should expect the same quality of analgesia as other patients. Combinations of regional nerve blocks and NSAIDs may avoid the need for opioids.
  • If opioids are the only method of providing analgesia they should be administered in the same way as for normal patients with doses titrated to effect (see p. 988 for a suitable dosing regime).
  • A small group of ‘ex-addicts’ will have great fears about being prescribed opioids if they have been ‘cured’ of their addiction. This should not become an obstacle to treating postoperative pain, but opioids should clearly not be given without first obtaining consent.
  • Do not attempt detoxification perioperatively! Opioid addicted surgical patients should be supported by specialist addiction services during the perioperative period (usually contactable via the local psychiatric services).
Cocaine and crack cocaine
  • Cocaine toxicity is mediated by central and peripheral adrenergic stimulation. Presenting symptoms include tachycardia, hypertension, aortic dissection, arrhythmias, accelerated coronary artery disease, coronary spasm, infarction, and sudden death. Intracerebral vasospasm can lead to stroke, rigidity, hyperreflexia, and hyperthermia. Inhalation of cocaine can cause alveolar haemorrhage or pulmonary oedema.
  • Psychiatric symptoms range from a feeling of elation and enhanced physical strength to full toxic paranoid psychosis.
  • Patients needing surgery following ingestion of cocaine may need intensive care management whilst they are stabilized. Most of the life-threatening side-effects of cocaine are due to vasospasm and can be reversed using combinations of vasodilators, antiarrhythmic agents and alpha/beta-blockers titrated against effect using full invasive monitoring.
  • Combination local anaesthetic/vasoconstrictors (or any vasopressor) should be avoided. Tachycardia or hypertensive crisis may result. If vasopressors are required in theatre use very small doses and titrate against response.
  • Intra-arterial injections of cocaine have lead to critical limb and organ ischaemia. Successful treatment has included regional plexus blockade, intravenous heparin, stellate ganglion block, intra-arterial vasodilators or urokinase, and early fasciotomy.
Ecstasy (3, 4, methylenedioxymethamphetamine (MDMA))
  • Approximately 20 people die from taking ecstasy annually in the United Kingdom.
  • Hyperthermia (>39 °C), disseminated intravascular coagulation, and dehydration are common features.
  • Hyperthermia has been linked to a combination of dehydration and hyperactivity. Excessive ADH release may also cause hyponatraemia leading to coma. Treatment involves carefully monitored fluid and electrolyte replacement.
Further reading
Cheng DCH (1994). The perioperative care of cocaine abusing patients. Canadian Journal of Anaesthesia, 41, 883–7.

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