Table 1.

Closed mono-compartment mathematical marginal model simulating the body water space of distribution

Variables	Day 0	Day 1	Day 2	Day 3	Day 4	Day 5
Patient’s resulting variables
Na+ (mEq/L)	140	142	148	151	146	144
Cl- (mEq/L)	100	108	114	117	113	111
Fluid balance (mL)	-	6000	0	800	800	0
Cumulative fluid balance (mL)	-	6000	6000	6800	7600	7600
Distribution water volume and electrolyte data
Vd (L)	36	42	42	43	44	44
Total mass of Na+ (mEq)	5040	5964	6216	6493	6424	6336
Total mass of Cl- (mEq)	3600	4536	4788	5031	4972	4884
Fluids output
Diuresis (mL)	-	2000	1200	1200	1200	2000
Urinary Na+ (mEq/L)	-	30	50	70	90	110
Urinary Cl- (mEq/L)	-	30	50	70	90	110
Fluids input
Volume	6000	2000	2000	2000	2000	2000
Na+ (mEq/L)	154	154	154	0	0	0
Cl- (mEq/L)	154	154	154	0	0	0

The main assumptions of this model are the absence of feces, sudoresis, renal replacement therapy, and the absence of Gibbs-Donnan effect. This patient was resuscitated with 4000 mL of 0.9% saline and received additional 2000 mL of 0.9 fluids during the Day 0. He received an amount of 0.9% saline during day 1 and day 2, afterwards the same 2000 mL of volume was infused without electrolytes due to hypernatremia. Vd: Denotes distribution volume.