Fluid Rate Is Important As Much As Fluid Tonicity: An Experimental Study.

Objective: There is no study evaluating the effect on plasma osmolality of both fluid tonicity and high fluid rate at the same time. The aim of this experimental study was to determine the change in the plasma osmolality by different fluid tonicity and rate, and to suggest the safest and the most appropriate fluids based on the plasma osmolality for medical situations requiring fluid therapy with high or maintenance rates.

Materials and methods: The rats were randomly divided into seven groups (six rats in each group): [D₅] D₅ administered at 100 ml/kg/24h; [D₅150] D₅ administered at 150 ml/kg/24h; [D₅(½)100] D₅ 0.45% NaCl administered at 100 ml/kg/24h; [D₅(½)150] D₅ 0.45% NaCl administered at 150 ml/kg/24h; [D₅(1)100] D₅ 0.9% NaCl administered at 100 ml/kg/24h; [D₅(1)150] D5 0.9% NaCl administered at 150 ml/kg/24h; [Control group] non-treated control rats. Intracardiac blood samples were collected from all the groups at the end of 24 h.

Results: [D₅(1)150] and [D5(½)100] were the group closest to the control group in terms of both sodium (P = .937; P = .699, respectively) and effective osmolality (P = 1, P = .818, respectively).

Conclusion: Our results showed that 0.9% NaCl and 0.45% NaCl solutions might be the safest and the most appropriate fluids to maintain normal plasma osmolality in medical situations requiring fluid therapy with high or maintenance rates, respectively.