Erythrocyte stability in ethanol-saline solutions.

Sir,—In a clinical evaluation of ethanol as an anaesthetic agent, Isaac and Dundee (1969) and Dundee and coworkers (1970) established that 8% w/v (10% v/v) ethanol in Hartmann's solution was the most satisfactory concentration for i.v. infusion in man and was associated with a low frequency of thrombophlebitis. Sanderson and co-workers (1970) confirmed that in vitro ethanol solutions in concentrations of 2.0-2.5 mol litre" (approximately equivalent to 10% v/v) in Hartmann's solution are least likely to cause erythrocyte lysis. Studies in our laboratory have shown that in vitro haemolysis of human erythrocytes is prevented (less than 5%) in 0.9% sodium chloride solution containing 0.0-10.0% v/v ethanol (Ku and Cadwallader, 1974). Also, our determination of "haemolytic" isotonic coefficients indicated that ethanol at the 10% v/v concentration provided a stabilizing effect on erythrocytes. Higher concentrations of ethanol, however, caused lysis; haemolysis was initiated in 11% v/v ethanol and was complete when the concentration reached 14% v/v. To examine this more closely, we obtained from the forearm veins of several 22-46-yr-old Caucasian and Oriental subjects 10 different blood samples, which were placed in 0.9% (0.154 mol litre") sodium chloride solutions containing various concentrations of ethanol. After 45 min at 37 °C, the maximum ethanol concentration which was not associated with haemolysis was 10.1% v/v + SD 0.52. These data confirm that 10% v/v is an optimum infusion concentration for ethanol in an isotonic vehicle and that higher concentrations cause haemolysis.