Normal saline...the bad aspects

The 2008 GIFTASUP report has come out strongly against the routine use of 0.9% saline, principally because of the risk of developing hyperchloraemic metabolic acido- sis.
This starts with the greater contribution of adding 154 mmol/L of chloride to a plasma concentration of around 100mmol/L compared to adding 154mmol/L sodium to a plasma concentration of 140 mmol/L. The relative increase in chloride concentration provides a disproportionate rise in strong anions reducing the bicarbon- ate concentration as predicted by the Stewart equations.

In addition to the acidosis, saline produces a number of other problems. Abdominal discomfort is occasionally experienced and there is some research evidence that saline produces reduced gastro- intestinal perfusion compared to balanced solutions.
Hyperchloraemia produces an increase in renal eicosanoid release leading to renal vasoconstriction and reduced glomerular filtration rate.
With a calculated osmolality of 308mOsm/kg, saline is slightly hyperosmolar compared to plasma but this is probably not clinically signifi- cant. The measured osmolality using a micro-osmometer is 286 mOsm/kg, implying that saline is not fully ionised at 0.9% concentration.

The GDA for dietary salt is 6 g per day for an adult, so a litre of saline with 9 g/L is 11⁄2 times the GDA.

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