It is well known that both thiopental sodium and propofol reduce the cerebral metabolic rate. The author investigated whether these drugs have similar effects on neurobiochemical compounds by using 1H-NMR, which enables noninvasive in vivo measurements of brain biochemistry.

Six healthy white New Zealand rabbits (2.5-3.0 kg) were studied. A marginal ear vein was punctured for continuous intravenous infusion. Spontaneous breathing was maintained during the anesthesia. Neurobiochemical compounds such as N-acetylaspartate (NAA), choline-containing compounds (Cho), creatine plus phosphocreatine (Cr), myoinositol (MI), and lactate were examined at 30, 45 and 60 min during intravenous anesthesia induced with thiopental sodium (n = 3) and propofol (n = 3).

The signals of NAA, Cho, Cr and MI were unchanged during thiopental anesthesia, but the NAA signal was reduced at 45 and 60 min, and that of Cr was reduced from 30 min until the end of the propofol anesthesia. The Cho signal was increased at 45 and 60 min during propofol anesthesia. Thiopental sodium signal were detected through the study, but propofol was detected only at 30 min. On comparing metabolic ratios in the two groups, the ratio of NAA/Cr was reduced and those of Cho/Cr and MI/Cr were higher in propofol group than in the thiopental sodium group.

Our results suggest that thiopental sodium has a cerebral protective function. Howerver, further study is needed upon the cerebral protective function of propofol anesthesia. Propofol is more useful for total intravenous anesthesia than thiopental sodium.