Water and sodium metabolism during intravenous re-feeding in the malnourished rabbit

Twenty-three New Zealand rabbits were starved until a mean weight loss of 21% was achieved and then re-fed parenterally with two different total parenteral nutrition (TPN) formulae: a standard formula (Group SF, n = 12) containing 100 ml/kg/day of water, 7 mEq/day of sodium and 70% of non-protein calories as glucose; and a modified formula (Group MF, n = 11) containing 70 ml/kg/day of water, no sodium and 70% of non-protein calories as fat. After 6 days of parenteral nutrition, Group SF showed a higher weight gain than Group MF (10 +/- 5.8% vs. 1.4 +/- 5%; p = 0.001) and serum albumin concentration in Group SF was lower than in Group MF (25.9 +/- 4.2 vs. 32 +/- 4.5 g/l; p = 0.004). There was a close correlation between weight gain and water and sodium balances (r(2) = 0.714; p = 0.0001 and r(2) = 0.447; p = 0.0005, respectively). In Group SF, a close correlation was found between the free water clearance and water balance (r(2) = 0.711, p = 0.0006). In conclusion, in Group MF water and sodium restriction led to a better nutritional response in terms of improving serum albumin concentrations and minimising weight gain, probably due to less expansion of the extracellular fluid compartment in this group.