Driving under influence of nitrous oxide - a case series

The increasing recreational use of nitrous oxide (N₂O) is also evident on the roads. Since there is very little data on driving under the influence of N₂O, this study aimed to characterize traffic-related N₂O cases in Germany by determining its blood concentrations and co-consumption of other substances as well as assessing documented driving behavior and psychophysical impairment. Fourty-four positive blood samples from traffic cases with suspicion of driving under the influence of N₂O, as well as the documents enclosed, including police and medical reports, were evaluated. Issues of participating in road traffic under the influence of N₂O are discussed.

Routine toxicological screening (drugs and alcohol) was performed at the Forensic Toxicological Center in Munich (Germany), while N₂O concentrations were determined by headspace-gas chromatography/mass spectrometry at the Institute of Legal Medicine in Hamburg-Eppendorf (Germany).

In 34 out of the 44 cases, positive results for N₂O were obtained in concentrations ranging from 0.10 to appr. 13 mL N₂O/L whole blood. Unlike previous reports, the present study combines analytical findings with observations of unusual behavior occurring while driving, during a police stop, or during blood sampling. Thirteen subjects were involved in a traffic accident, whereas among the remaining subjects, driving abnormalities such as weaving across lanes or red-light violations were observed. Also, other psychophysical performance deficits were identified, among others somnolence, confusion, disorientation, impaired cognitive responsiveness, lack of concentration, slurred speech or balance problems. Such deficits indicate an impairment of the central nervous system that is incompatible with the safe operation of a vehicle.

The determination of N₂O in the blood samples of road users proves recent exposure and provides important forensic-toxicological evidence when interpreting accidents or erratic driving following suspected N₂O use. Analytical verification increases the evidentiary value and should therefore be routinely performed in cases where there is suspicion of N₂O use.