Gammahydroxybutyrate (GHB) Toxicity



Background

Synthesised in 1960 GHB was initially used as an anaesthetic agent, it has also been used as a muscle building agent in withdrawal states and as a psychoactive drug of abuse. GHB is a chemical compound structurally similar to the inhibitory brain neurotransmitter GABA.


Clinicall features in toxicity

  • Patients often have a characteristic history of collapse with or without seizure whilst out socialising.
  • Low GCS scores and respiratory depression.
  • History of GHB ingestion is described by friends or witnesses 
  • Rapidly absorbed from GI tract
  • Effects occur 15-60 mins post ingestion and usually resolve in 3-9 hours

Central nervous system symptoms

  • mild: nystagmus, dizziness, ataxia to
  • severe: coma, respiratory failure, apnoea, death

Typically, short period of euphoria followed by a rapid and profound decline in the level of consciousness.

Seizure like activity and myoclonus.

Pupillary findings are variable.

Respiratory symptoms

  • Respiratory depression
  • Aspiration: In addition to above signs of aspiration

Gastrointestinal symptoms

  • Nausea, Vomiting

Cardiovascular

  • Bradycardia (related to the depressed level of consciousness. Reversed with atropine).
  • Hypotension (often co-ingestion of alcohol)
  • Consider other toxic substance if hypotension not readily resolved by stimulation or atropine

Other

  • Mild hypothermia has been reported in about 70% of cases.

Investigations

Laboratory not available; wide differential diagnoses require wide range of tests.

  • Check BM
  • ECG - sinus bradycardia, AF, RBBB, 1st degree HB, U-waves
  • ABG - mild respiratory acidosis or hypercapnia
  • Head CT and C-spine x-rays as indicated
  • FBC, U&Es, blood glucose - hypokalaemia, hyponatraemia and hyperglycaemia
  • Perform a pregnancy test in females of childbearing age

Management

Mainstay is supportive treatment:

Airway

Maintain airway ± BMV as necessary. Call for help. Conservative approach to intubation

Breathing

Naloxone - no proven benefit but not harmful helps exclude opiate OD

Circulation

Cardiac monitoring: 

  • arrhythmias and conduction deficits noted frequently.
  • atropine to treat symptomatic bradycardia that is unresponsive to stimulation

Disability

Control convulsions with benzodiazepine

  • Reversal of GHB - induced CNS depression is controversial
  • Physostigmine may reverse sedation in some clinical trials but
  • The risks of physostigmine use (eg, bradycardia, asystole, seizures) may outweigh the benefits.

Other measures as indicated by patients condition e.g. warmers for hypothermia


Outcomes

  • Most patients recover fully within six hours
  • Fully recovered patients may be discharged home with appropriate observation for 24 hours
  • Awareness of other issues such as sexual assault is important.

Content by Dr Íomhar O' Sullivan 20/08/2003. Reviewed by Dr ÍOS 20/08/2004, 18/05/2005, 13/05/2007. Last review Dr. ÍOS 18/09/14 .