Distribution of ethanol and water between plasma and whole blood; inter- and intra-individual variations after administration of ethanol by intravenous infusion.

Hospital patients (n = 17) received 0.216 mmol/min kg body weight of ethanol as an intravenous infusion over 60 min. At fixed time intervals during and after administration, two consecutive samples of whole blood (5 ml each) were taken from a cubital vein. The plasma fraction was obtained by centrifugation of one of the tubes. The concentrations of ethanol in whole blood and plasma were determined by headspace gas chromatography and the water contents of the specimens by desiccation. The mean plasma:whole blood ratio of ethanol was 1.10:1, range 1.03:1 to 1.24:1 (n = 159). The components of variance (SD) within subjects and between subjects were 0.0293 (CV 2.7%) and 0.0165 (CV 1.5%) respectively. The 95% confidence interval ranged from 1.03:1 to 1.16:1 for a single new determination in a subject from the same population. The average water content in plasma and whole blood were 91.8% w/w (SD 0.49) and 80.1% w/w (SD 1.03) respectively. Neither the mean plasma:blood ratio of ethanol nor the water content of the specimens depended on sampling time after ethanol administration.