[Gamma-hydroxybutyric acid--significance for anesthesia and intensive care medicine?].

Gamma-hydroxybutyric acid (GHB) as a natural component of the mammalian brain was first introduced in clinical anaesthetic practice more than 30 years ago. Although GHB induced a reliable state of sedation and anaesthesia without depressing either respiratory or cardiocirculatory parameters or liver and kidney function, the drug was nearly displaced from clinical practice because of its prolonged duration of action. The results of recent clinical studies indicate a re-evaluation of GHB in emergency and critical care medicine. GHB is regarded as a natural neuronal transmitter with circuits which synthesise, accumulate and release GHB. Specific binding sites have also been demonstrated and identified. GHB is completely metabolized in the liver to the natural substrates carbon dioxide and water without accumulation in central or peripheral tissues. The reduction of energy metabolism and its possible properties as an "oxygen radical scavenger" may be of therapeutic benefit if tissues are exposed to hypoxia or reperfusion. Therefore, the application of GHB seems to be of advantage in states of traumatic brain injury with cerebral oedema or ischaemic lesions of brain or extraneural tissues. In hypovolaemic states or in patients with impaired cardiovascular function, the pressure effects of GHB may be beneficial for the prevention of tissue damage and may improve survival in the case of cardiocirculatory resuscitation. In the intensive care unit, GHB might be a favourable alternative to established sedative agents. Occurrence of side effects such as tolerance and withdrawal syndromes after the application of sedative drugs, an impaired metabolism with the accumulation of metabolites in the case of liver or kidney dysfunction as well as an insufficient regulation of natural sleep may be diminished by the application of GHB. The results of various clinical studies also suggest that GHB may be useful in the treatment of alcohol and opiate withdrawal syndrome. However, further studies are necessary to specify the proposed indications of GHB in anaesthesiology and critical care medicine.