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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The pressure volume loop...

In the pressure-volume loop below, cardiac work is best represented by: the area of the curve the slope of the line from points C to D the distance of the line from points C to D the slope of a line from points A to D .. .. ... .... ... .... .... .... In the pressure-volume loop below, cardiac work is best represented by: the area of the curve Cardiac work is the product of pressure and volume and is linearly related to myocardial oxygen consumption. Cardiac work is best represented by the area of the curve of a pressure-volume loop.

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