Variability of BAC/BrAC, BAC/SAC and SAC/BrAC Ratios During Absorption and Elimination of Alcohol

A group of 38 volunteers participated in 74 experiments with multiple collection of blood and saliva samples and simultaneous breath testing. BAC/BrAC, BAC/SAC and SAC/BrAC ratios were calculated for every sampling time for each examined person in each experiment. It gave 975 values of the distribution ratio of ethanol for each system. The mean values of BAC/BrAC ratio calculated for absorption and elimination phases differed significantly (1822.1±315.9 and 2330.9±384.7, respectively, t=19.0, p<0.001). BAC/BrAC ratio slightly grows with increase of ethanol concentration in absorption phase (BAC/BrAC = 1583±60 + 466±110 x BAC, r=0.26, p<0.001) and with fall of ethanol concentration during elimination (BAC/BrAC = 2758±40 – 836±75 x BAC, r=-0.39, p<0.001). The difference in BAC/SAC ratio in both phases was also statistically significant (832±0.152 and 1.037±0.157, t=18.1, p<0.001). SAC/BrAC ratio did not show any dependency on the phase (2217.6 ± 384.6 and 2264.3 ± 357.4, t=1.81, p>0.05). Both in the absorption and elimination phase the SAC/BrAC ratio value felt with alcohol concentration (absorption: SAC/BrAC = 2572±66 – 595±104 x BrAC, r=-0.34, p<0.001; elimination SAC/BrAC = 2514 ± 33 – 517±64 x BrAC, r=-0.29, p<0.001). Introduction Reliable, valid and non-invasive methods of the sobriety testing are important in forensic, work place, medical and research settings (1). To date mainly breath testing is used for this purpose. In the eighties evidential breath alcohol instruments were approved for law enforcement purposes and threshold limits of breath alcohol concentration (BrAC) were introduced alongside the existing statutory blood alcohol concentration (BAC) limits (2). Nevertheless measurements of breath alcohol may not be accurate in some cases, i.e. in febrile or hypothermic patients, unconscious victims, or patients with bronchopulmonary disease (3). At the present time there is increasing emphasis on saliva as a biological specimen for analysing drugs of abuse, therapeutic agents, ethanol, environmental chemicals and many endogenous substances (4). The ratio of blood flow to tissue mass of the salivary gland is so large, the concentration of alcohol entering saliva reflects the concentration in arterial blood (5). It is very favourable because acute alcohol effects on the brain function are correlated with the concentrations in this type of blood. It is a reason the saliva /blood ratio of ethanol is not constant during pharmacokinetic phases because saliva primarily reflects the arterial and not the venous branch of blood circulation system (6). The saliva specimens serve as substitutes for blood, and the analytical finding is usually translated into the presumably equivalent blood alcohol concentration. The aim of this study was to estimate the variability of breath/blood, saliva/blood and saliva/breath ethanol distribution coefficients and to assess the possibility of saliva analysis as a direct method for sobriety testing. Material and Methods A group of 38 volunteers (26 men and 12 women, aging 23 – 60 years at the beginning of the study) participated in 74 experiments. The volunteers were social drinkers with no history of alcohol abuse. The subjects in each experiment consumed alcohol in the form of 40 % v/v vodka, within 15 minutes, two hours after last meal. They received a dose of ethanol: men – 0.7 g and women – 0.6 g of ethanol/kg of body weight. After inserting a catheter into a large cubical vein, blood samples were taken at 15 minutes intervals. Simultaneously the mixed saliva secretion samples were collected and breath alcohol concentration was measured using Alcometr A 2.0. Blood and saliva alcohol concentrations were determined by means of headspace gas chromatography using Perkin Elmer Autosystem apparatus equipped with autosampler HS 40. Separation was achieved on a 0.2% Carbowax 1500 / Graphpack-GC column under isothermal conditions (100 °C). The temperature of the flame ionization detector (FID) was 200 °C. A 0.2 ml blood or saliva was mixed with 1.8 ml of 0.002 g/l 2methyl-2-propanol (tert-butyl alcohol) used as internal standard (IS). The samples were incubated in the autosampler for 22 minutes at 60 °C. Chromatograms were received and calculations were done using Turbochrom computer program. The statistical analysis were performed with use of STATISTICA software (Statsoft Inc., Tulsa, OK, USA). Results The study covered 74 experiments with multiple collection of blood and saliva samples and simultaneous breath testing. The samples were collected up to time when BrAC felt below 0.1 mg/l. Moreover the results with BAC and SAC lower than 0.2 g/l were rejected. This operation was done because of the great uncertainty in estimation of partition coefficients below these values. It gives 975 results of alcohol concentration in each specimen. 256 of them was classified as absorption phase while the rest as elimination one. The maximum ethanol concentration in blood was the criterion for division of the data. In Figure 1 the mean values of BAC/BrAC, BAC/SAC and SAC/BrAC ratios calculated for absorption and elimination phases were compared.