(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 < 0.01). At 6 h, bodyweight measurements suggested that 56% of the infused saline was retained, in contrast with only 30% of the Hartmann's solution. Subjects voided more urine (median: 1000 compared with 450 ml) of higher sodium content (median: 122 compared with 73 mmol) after Hartmann's than after saline (both P = 0.049), despite the greater sodium content of the latter. The time to first micturition was less after Hartmann's than after saline (median: 70 compared with 185 min; P = 0.008). There were no significant differences between the effects of the two solutions on serum sodium, potassium, urea or osmolality. After saline, all subjects developed hyperchloraemia (> 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.