The influence of circulating blood volume on blood ethanol concentrations in a rat model

In the medicolegal field, whether a victim was under the influence of ethanol at the time of an accident or injury is an important issue. However, trauma victims may have lost a large amount of blood, or received cardiopulmonary resuscitation or infusions of fluid or blood, making it difficult to interpret the ethanol concentration at the time of sampling. We, therefore, investigated changes in ethanol elimination in a rat model in which variations in circulating blood volume were induced by means of slow hemorrhage or infusion. Animals were divided into four experimental groups: hemorrhage (H), infusion (I), hemorrhage and infusion (H&I), and control (C). All rats were administered ethanol (1 g/kg body weight) intravenously over a period of 5 minutes. Blood (group C and group I: 0.2 ml, group H and group H&I: 0.5 ml/300gBW) was collected from rats in each group every 10 minutes for 4 h. Every 10 minutes after 30 minutes to 4 h of the ethanol administration, the rats in the infusion groups were administered saline (group I: 0.5 ml/300gBW, group H&I: 1.0 ml/300gBW). The concentration of ethanol in the blood samples was determined by using head-space gas chromatography. We found that the ethanol elimination rate did not differ between the groups, indicating that variations in body fluid due to bleeding or infusion have little to no effect on blood ethanol concentrations. Blood ethanol levels obtained after a prolonged state of shock or agonal, however, may need to be cautiously interpreted.