Hyperosmolar coma due to exclusive glucose accumulation: recognition and computations.

AIM

To avoid electrolyte derangements during correction of hyperosmolar coma (HC), PNa(PREDICTED) at the end of correction is presently estimated from plasma glucose (P(G), mM/L). When the rise in plasma osmolality (Posm) is entirely due to glucose addition (G(A), mM) to the extracellular volume (ECV), this PNa prediction can be improved by correctly estimating G(A) and any associated water loss (DeltaV), while excluding any concomitant Na loss (DeltaNa).

METHODS

Indicating with (0) the normal conditions, with (1) the HC,DeltaPosm=P(G1)xECV1 establishes an exclusive G(A) accumulation. We derived the equations for computing G(A), DeltaV and PNa(PREDICTED). Computer simulations of HC were performed by adding the known G(A) while subtracting the known DeltaV and DeltaNa in different combinations, obtaining exact values of PNa(1) and P(G1). Applying our formulas, we recognized and discarded all cases with concomitant DeltaNa, and we computed G(A), DeltaV and PNa (PREDICTED) from PNa(1) and P(G1), as if they had been measured in patients. We extended these same calculation algorithms to 68 patients with HC.

RESULTS

In computer simulations, true and calculated G(A), DeltaV and PNa(PREDICTED) were identical, such that regression and correlation coefficients were 1 (P < 0.0001). Out of the 68 patients recruited, 13 fulfilled the boundary conditions of an exclusive G(A) addition. The true values, obtained by balance studies performed on these patients, were not different from and significantly correlated with the calculated data (R(2) = 0.99, P < 0.001).

CONCLUSION

Our new model system for HC and the new formulas improve to near exactness the accuracy in estimating PNa(PREDICTED), helping the physician to avoid unwanted electrolyte derangements during treatment.