Question 7 from the second paper of 2001 asks the candidates to list some drug withdrawal states which might be encountered in the ICU, and to list the principles of their management. The LITFL page on drug withdrawal states in the ICU is a good brief introduction, and closely resembles the college model answer. Greater detail than that is probably undesirable, as it may lead the candidate into confusion and despair. However, that is what we do here at Deranged Physiology.

Generally speaking, this topic is poorly covered in the critical care literature. One can find isolated articles dealing with alcohol or opiates, but little in the way of a broad overview. Even Oh's Manual fails to address this issue. The best resource for this seems to be Goldfranks' Manual of Toxicologic Emergencies (2007), where Chapter 15 deals with principles of withdrawal management. In this summary, I will use the structure offered by this resource; it cleverly organises its withdrawal syndromes by the receptor being affected. Another textbook chapter of note is Withdrawal Syndromes  (Ch. 70) from the Ford's Clinical Toxicology (2001).  These two chapters were used to compile the table below,  and ensuing discussion of management principles. Of the published articles I have managed to scrape together, the most detailed seems to be Tetrault and O'Connor's "Substance abuse and withdrawal in the critical care setting" (Critical care clinics, 2008).

 
Withdrawal Syndromes organised by Neurotransmitter  System
Receptor
system
Drugs Clinical withdrawal syndrome Management options
GABAA Alcohol
Barbiturates
Benzodiazepines
Organic solvents
CNS excitation (agitation, tremor, hallucinations, delirium, seizures) 
Autonomic stimulation (tachycardia, hypertension, hyperthermia, diaphoresis)
Benzodiazepines
Dexmedetomidine
GABAB GHB
Baclofen
Dyskinesia, seizures, hypertension, hallucinations, psychosis, and coma. Benzodiazepines
Opioid Opiates Diarrhoea, mydriasis, nausea, yawning, lacrimation, rhinorrhoea and piloerection.
Increased autonomic sympathetic activity.
Importantly, there is no seizures, fever, or altered mental status.
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 -
Cannabinoid Cannabis Agitation, insomnia, poor gut motility Mirtazapine ?

Adverse effects of drug withdrawal on ICU management

  • Agitation:
    • Increased need for sedation owing to agitation
      • Thus, longer periods of intubation and slower weaning from ventilation
      • Thus, increased risk of VAP
    • Haemodynamic toxicity of sedatives
      • Increased total body oxygen consumption and increased demand on the myocardium
      • Thus, increased CO2 production
      • Thus, increased ventilation demands
  • Seizures
    • CNS toxicity
    • May go unrecognised if the patient is paralysed
  • Resistance to the effects of routinely used sedatives and analgesics
    • Use of higher doses may lead to toxicity, eg. propofol infusion syndrome

Generic management strategies for drug withdrawal in the ICU

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.

References

Jenkins, Donald H. "Substance abuse and withdrawal in the intensive care unit: Contemporary issues." Surgical Clinics of North America 80.3 (2000): 1033-1053.
 
Kosten, Thomas R., and Patrick G. O'Connor. "Management of drug and alcohol withdrawal." New England Journal of Medicine 348.18 (2003): 1786-1795.
 
Tetrault, Jeanette M., and Patrick G. O'Connor. "Substance abuse and withdrawal in the critical care setting." Critical care clinics 24.4 (2008): 767-788.