Gamma-hydroxybutyrate poisoning: clinical diagnosis versus laboratory findings.

Introduction: Patients poisoned with gamma-hydroxybutyrate may need urgent medical treatment. The clinical manifestations are heterogeneous, and the level of consciousness is often unstable, with fluctuations between agitation and coma. We aimed to investigate the accuracy of the clinical diagnosis of gamma-hydroxybutyrate poisoning compared to laboratory findings in blood samples.

Methods: We did a prospective observational study, including patients ≥16 years of age admitted to hospital with a clinical diagnosis of gamma-hydroxybutyrate poisoning. The diagnosis was established by the doctor treating the patient based on the clinical information and/or information from the patient and/or the patient's companions. Blood samples were taken at admission and analyzed using ultra high-performance liquid chromatography-tandem mass spectrometry.

Results: There were 87 patients with a median age of 35 years (IQR: 30-42 years), and 58.6% (51/87) were male. Gamma-hydroxybutyrate was found in blood samples taken from 60 (69.0%) patients. The median Glasgow Coma Scale of all patients on arrival at hospital was 6 (IQR: 3-10), and 53.3% of the patients who tested positive for gamma-hydroxybutyrate presented with a Glasgow Coma Scale of 3. The Glasgow Coma Scale was significantly lower (P <0.001) among patients who tested positive for gamma-hydroxybutyrate, and was inversely correlated with gamma-hydroxybutyrate concentrations. Among the 60 patients testing positive for gamma-hydroxybutyrate, 28 (46.7%) needed treatment in an intensive care unit, and three (5.0%) required endotracheal intubation. In 58 (96.7%) of the 60 patients who tested positive for gamma-hydroxybutyrate, other drugs were also found, most frequently amfetamines, cocaine, and benzodiazepines.

Discussion: The frequent co-consumption of other psychoactive drugs makes the clinical diagnosis of gamma-hydroxybutyrate challenging, and poisoning with other central nervous system depressants was frequently observed among those patients testing negative for the gamma-hydroxybutyrate.

Conclusions: In only two out of three patients with clinically suspected gamma-hydroxybutyrate poisoning was gamma-hydroxybutyrate found in a blood sample, indicating that clinicians might overdiagnose gamma-hydroxybutyrate poisoning.