The only consistent clinical features in 1,140 cases of short-acting barbiturate overdosage were CNS depression with and without respiratory depression, hypotension, and hypothermia. Seven states of intoxication were defined and then scored, using a modification of the Glasgow coma scale. There was a linear correlation between the "intoxication score" and the mean serum short-acting barbiturate concentration in 688 cases tested. The following serum short-acting barbiturate concentrations may be expected for nonaddicted patients having no medical complications contributing to cerebral depression and intoxicated with only short-acting barbiturate: less than 6 μg/mL, alert; 8+/-2 μg/mL, drowsy; 14+/-3 μg/mL, stuporous; 18+/-2 μg/mL, coma 1; 22+/-2 μg/mL, coma 2; 26+/-2 μg/mL, coma 3; and 34+/-6 μg/mL, coma 4. The serum concentrations will be lower if the patient has ingested an additional sedative or has a complication contributing to cerebral depression, and higher if the patient is addicted to a sedative-hypnotic drug.
McCarron MM, Schulze BW, Walberg CB, Thompson GA, Ansari A. Short-Acting Barbiturate OverdosageCorrelation of Intoxication Score With Serum Barbiturate Concentration. JAMA. 1982;248(1):55–61. doi:10.1001/jama.1982.03330010029026