(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, body weight 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 l 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 l 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 hyper-chloraemia (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 l 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.