Fluid and electrolyte overload in critically ill patients: An overview

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.

Table 2 Potential complications of fluids and electrolytes overload

Organ system	Complication	Main modifiable risk factor	Pathophysiological mechanism
Central nervous system	Delirium	Hypernatremia	Excessive sodium load Kidneys inability to excrete excess sodium load
Renal/metabolic	Worse recovery of renal function	Cumulative fluid balance/higher CVP	Renal edema, reduced perfusion pressure
	Worsening acute kidney injury	Unbalanced solutions	Chloride-induced renal vasoconstriction
	Worsening acidemia	Unbalanced solutions	Solution SID relative to plasma SID Kidneys inability to excrete excess chloride load
Respiratory	Impaired gas exchange Altered pulmonar and chest wall mechanics Increased work of breathing	Cumulative fluid balance/higher CVP/higher EVLW	Lung edema
Gastrointestinal	Ileum	Cumulative fluid balance	Bowel edema
	Hepatic congestion	Higher CVP	Hepatic congestion
	Increased intra-abdominal pressure (may induce by itself more organ dysfunctions)	Cumulative fluid balance	Visceral edema (bowel, renal, etc.), ascites
Hemostasis	Increased bleeding	Unbalanced solutions	Acidemia secondary to chloride load
Wound healing	Impaired wound healing	Cumulative fluid balance	Local edema
Hemodynamics	Worse microcirculatory blood flow	Higher CVP	Reduced perfusion pressure

CVP: Central venous pressure; SID: Strong ion difference; EVLW: Extravascular lung water.