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
Key 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.
Glasgow Coma Score
Score |
Eye Opening |
Verbal |
Motor |
|---|---|---|---|
6 |
Obeys commands |
||
5 |
Speech orientated , localises to pain |
||
4 |
Spontaneous eye opening |
Confused speech |
Withdrawal to pain |
3 |
Eye open to speech |
Incoherent words |
Abnormal flexion to pain |
2 |
Eyes open to pain |
Only sounds |
Extends to pain |
1 |
No eye opening |
No sounds |
No movements |
Tests
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 in the Emergency Department
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.
