Anesthesia for Substance Abuse

SUBSTANCE ABUSE

Behavioral disorders from abuse of psychotropic (mind-altering) substances may involve a socially acceptable drug (alcohol), a medically prescribed drug (eg, diazepam), or an illegal substance (eg, cocaine). Characteristically, with chronic abuse, patients develop tolerance to the drug and varying degrees of psychological and physical dependence. Physical dependence is most often seen with opioids, barbiturates, alcohol, and benzodiazepines. Life-threatening complications primarily due to sympa-thetic overactivity can develop during abstention.

Knowledge of a patient’s substance abuse pre-operatively may prevent adverse drug interactions, predict tolerance to anesthetic agents, and facilitate the recognition of drug withdrawal. The history of substance abuse may be volunteered by the patient (usually only on direct questioning) or deliberately hidden.

Anesthetic requirements for substance abusers vary, depending on whether the drug exposure is acute or chronic (see Table28–4). Elective proce-dures should be postponed for acutely intoxicated patients and those with signs of withdrawal. When surgery is deemed necessary in patients with physical dependence, perioperative doses of the abused sub-stance should be provided, or specific agents should be given to prevent withdrawal. In the case of opioid dependence, any opioid can be used, whereas for alcohol, a benzodiazepine is usually substituted due to the reluctance of hospital pharmacies to dispense

alcohol-containing beverages to patients. Alcoholic patients should receive B vitamin/folate supplemen-tation to prevent Korsakoff ’s syndrome. Tolerance to most anesthetic agents is often seen, but is not always predictable. For general anesthesia, a technique pri-marily relying on a volatile inhalation agent may be preferable so that anesthetic depth can be readily adjusted according to individual need. Awareness monitoring should be likewise considered. Opioids with mixed agonist–antagonist activity should be avoided in opioid-dependent patients because such agents can precipitate acute withdrawal. Clonidine is a useful adjuvant in the treatment of postoperative withdrawal syndromes.

Patients routinely present acutely intoxicated for emergency surgery following trauma related to sub-stance abuse. Patients have often consumed more than one class of intoxicating agent. Acute cocaine intoxi-cation may produce hypertension secondary to the increase in central neurotransmitters, such as norepi-nephrine and dopamine. Hypertension and arrhyth-mias can occur perioperatively. Chronic abusers deplete their sympathomimetic neurotransmitters, potentially developing hypotension. Amphetamine abusers have similar anesthetic concerns, as amphet-amines also affect the sympathetic nervous system. Patients on chronic prescribed opioid therapy, or those taking medications illicitly, have substantiallyincreased opioid postoperative requirements. Multimodal approaches to pain control are useful perioperatively, and patients should be started on maintenance methadone as soon as possible.Consultation with pain management and addic-tion specialists is often indicated.