(Ab)normal saline and physiological Hartmann's solution: a randomized double-blind crossover study

In this double-blind crossover study, the effects of bolus infusions of 0.9% saline (NaCl) and Hartmann's solution on serum albumin, haematocrit and serum and urinary biochemistry were compared in healthy subjects. Nine young adult male volunteers received 2-litre intravenous infusions of 0.9% saline and Hartmann's solution on separate occasions, in random order, each over 1 h. Body weight, haematocrit and serum biochemistry were measured pre-infusion and at 1 h intervals for 6 h. Biochemical analysis was performed on pooled post-infusion urine. Blood and plasma volume expansion, estimated by dilutional effects on haematocrit and serum albumin, were greater and more sustained after saline than after Hartmann's solution (P 105 mmol/l), which was sustained for >6 h, while serum chloride concentrations remained normal after Hartmann's (P <0.001 for difference between infusions). Serum bicarbonate concentration was significantly lower after saline than after Hartmann's (P =0.008). Thus excretion of both water and sodium is slower after a 2-litre intravenous bolus of 0.9% saline than after Hartmann's solution, due possibly to the more physiological Na(+)/Cl(-) ratio in Hartmann's solution (1.18:1) than in saline (1:1) and to the hyperchloraemia caused by saline.