Question 7

College Answer

Drug withdrawal states in ICU patients may be more common than is generally appreciated. They include –

•    Alcohol

•    Tobacco (nicotine)

•    Narcotic (heroin, morphine)

•    Benzodiazepines

•    Caffeine

•    Other street drugs (cocaine etc)

Principles of their management include –

•    prevention (avoid prolonged high dose narcotics, benzodiazepines

•    detection/diagnosis (be alert for signs eg agitation, tachycardia, fever)

•    sedation (may be necessary to control systemic effects)

•    replacement/substitution (eg nicotine patch)

•    support (airway and respiration, fluid replacement)

•    simple measures such as but firm communication, reality orientation, visible clock and presence of a relative contribute to reassurance of the patient.

Discussion

The following withdrawal syndromes seem relevant:

Withdrawal Syndromes organised by Neurotransmitter  System

Receptor	Drugs	Clinical withdrawal syndrome	Management options
GABAA	Alcohol Barbiturates Benzodiazepines Organic solvents	CNS excitation (agitation, tremor, hallucinations, seizures)  Autonomic stimulation (tachycardia, hypertension, hyperthermia, diaphoresis)	Benzodiazepines Dexmedetomidine
GABAB	GHB Baclofen	Dyskinesia, seizures, hypertension, hallucinations, psychosis, and coma.	Benzodiazepines
Opioid	Opiates	CNS excitation (agitation, tremor, hallucinations) Diarrhoea, mydriasis, nausea. Autonomic stimulation (tachycardia, hypertension, hyperthermia, diaphoresis)	Clonidine Dexmedetomidine
Adenosine	Caffeine	Head-ache (cerebral vasodilation), fatigue, and hypersomnia (motor inhibition)	-
Nicotinic acetylcholine receptor	Nicotine	Agitation, insomnia, poor concentration, poor gut motility, poor feed tolerance.	Varenicline?
Noradrenenaline	Amphetamines	Agitation, dysphoria, somnolence	-
Dopamine	Cocaine	Anhedonia, irritability, exhaustion	-
Cannabis		Agitation, insomnia, poor gut motility	Mirtazapine ?

The college presents an excellent summary of the generic principles of managing drug withdrawal:

•    prevention
•    detection/diagnosis
•    sedation
•    replacement

In greater detail:

Prevention

In this context, "prevention" is not some sort of grassroots social work movement to gets the kids off their street drugs, but rather the push towards intelligent use of opiates and benzodiazepines in the ICU. Rationalising the infusions should prevent the development of iatrogenic withdrawal syndromes. Fortunately, the ICU environment typically does not favour true psychological addiction, as the pleasurable context of drug use is not present.

Detection

In this context, detection describes vigilant monitoring for drug withdrawal:

• History (i.e. discussing drug use with the family)
• Examination (looking for features suggestive of drug use, eg. track marks)
• Biochemistry (eg. the pre-intubation urine drug screen)
• Index of suspicion (keeping drug withdrawal in the list of differentials when assessing a patient with tachycardia, delirium, fever, or failure to wake)

Supportive management

The supportive management of drug withdrawal aims to reduce the harm from the physiological and psychological consequences of withdrawal:

• Sedation (for comfort)
• Analgesia (to combat post-opioid hyperalgesia)
• Control of physiological derangements (eg. clonidine to block the sympathetic storm of opiate withdrawal)
• Protection of the CNS from seizures (i.e. in benzodiazepine and alcohol withdrawal)

Replacement and substitution

The aim is to replace the drug of addiction with a less harmful substance which offers submaximal receptor stimulation, so that the symptoms of withdrawl are ameliorated and the harm of pursuing the addiction is reduced. Examples of this include methadone and varenicline.