Computation of the excess glucose and Na deficit of hypo-osmolar hyponatremic hyperglycaemia

Exact computations of glucose accumulation (GA,mM) and Na anions deficit (δNa, mEq) can be obtained in hypo-osmolar hyponatremic hyperglycaemia (HHH), where plasma osmolality (POsm) is lower than normal.In this condition, GA - δNa = δPOsm × TBW (total body water).GA is given by plasma glucose concentration (PG₁ ) times extra-cellular volume (ECV), calculated as TBW-ICV (the known intra-cellular volume).The changes in solute content can then be computed from their concentrations. This model was verified on computersimulated patients to whom GA was added in variable amounts,lower than those of δNa subtracted, generating known ICV,ECV,PNa₁,and PG₁ .True computer-generated values were identical(the correlation coefficient R² = 1, p<0.0001) to those computed from solute concentrations with our formulas.These same calculations were applied to patients with HHH, using exclusively the measured PNa₁ and PG ₁ to compute solute and solvent changes.The results were significantly correlated to true data obtained by balance studies (R² = 0.89, p<0.001).The mathematical model correctly computes δNa and GA in HHH, where patients can therefore benefit from accurate replacement strategies.