Body Fluid Balance Calculator by Inputs and Outputs

Body Fluid Balance Calculator

Intake

IV Fluids

Oral Intake

Blood Products

Output

Urine Output

Drain Output

Estimated Insensible Losses

Fluid Balance: –

Awaiting input

Enter at least one intake value.

Calculates fluid balance from sodium concentrations which indicate net 0.9% saline, and free water losses (GI, urine, etc) and gains (IV fluids, PO, etc).

Why Use

Daily changes in total body weights and total intakes and outputs do not correlate ( Testani 2015 ) and include both volume and water components, making those measures less accurate for assessing fluid balance. Calculating net changes in volume and water may allow for better management of volume status and changes in serum sodium concentrations.

When to Use

Hospitalized patients with parenteral and/or enteral intake.

Formula

Total 0.9% saline gain/loss = sum of saline gain/loss for all body fluids/solutions Total free H₂O gain/loss = sum of H₂O gain/loss for all body fluids/solutions Body fluid LOST Sodium content, mEq/L 0.9% saline gain/loss, mL Free H₂O gain/loss, mL Gastric 49.0 [Na⁺] x volume / -154 -1 x volume - saline gain/loss Biliary 185.0 [Na⁺] x volume / -154 -1 x volume - saline gain/loss Pancreatic 156.0 [Na⁺] x volume / -154 -1 x volume - saline gain/loss Small bowel 117.0 [Na⁺] x volume / -154 -1 x volume - saline gain/loss Diarrhea, nonosmotic 69.0 [Na⁺] x volume / -154 -1 x volume - saline gain/loss Sorbitol-based osmotic diarrhea 63.0 [Na⁺] x volume / -154 -1 x volume - saline gain/loss Lactulose-based osmotic diarrhea 26.0 [Na⁺] x volume / -154 -1 x volume - saline gain/loss Osmotic diarrhea - PEG 13.0 [Na⁺] x volume / -154 -1 x volume - saline gain/loss Pleural or peritoneal fluid 137.0 [Na⁺] x volume / -154 -1 x volume - saline gain/loss Wound drainage 137.0 [Na⁺] x volume / -154 -1 x volume - saline gain/loss Dialysis net ultrafiltrate* 134.0 [Na⁺] x volume / -154 -1 x volume - saline gain/loss Urine Enter [Na⁺]** [Na⁺] x volume / -154 -1 x volume - saline gain/loss Insensible losses 0 [Na⁺] x volume / -154 -1 x volume - saline gain/loss Other body fluid Enter [Na⁺] [Na⁺] x volume / -154 -1 x volume - saline gain/loss *Exclude pRBCs; enter pRBC volume under parenteral solutions given. **If available (otherwise, use 65 mEq/L as default). Parenteral (IV) solutions administered Sodium content, mEq/L 0.9% saline gain/loss, mL Free H₂O gain/loss, mL Packed RBCs* 154.0 (0.6 x 4 x 154 + (1 - 0.6) x [Na⁺]) x volume / 154 0 Plasma, cryoprecipitate, platelets, or IVIG** 154.0 [Na⁺] x volume / 154 volume - saline gain/loss 5%, 20%, 25% albumin*** 154.0 [Na⁺] x volume / 154 volume - saline gain/loss 0.9% saline 154.0 [Na⁺] x volume / 154 volume - saline gain/loss 0.45% saline 77.0 [Na⁺] x volume / 154 volume - saline gain/loss Plasma-lyte A 140.0 [Na⁺] x volume / 154 volume - saline gain/loss Ringer's lactate 130.0 [Na⁺] x volume / 154 volume - saline gain/loss D5W 0 [Na⁺] x volume / 154 volume - saline gain/loss NaHCO₃ concentrate**** 1000.0 [Na⁺] x volume / 154 volume - saline gain/loss 100 mEq NaHCO₃ in 1L D5W 100.0 [Na⁺] x volume / 154 volume - saline gain/loss Injectable sodium phosphates***** 4000.0 [Na⁺] x volume / 154 volume - saline gain/loss TPN Enter [Na⁺] [Na⁺] x volume / 154 volume - saline gain/loss *1 unit of pRBCs ~ 350 mL; Hct ~ 60% in 0.9% saline; 1 mL pRBC ~ 2.8 mL 0.9% saline. **1 unit of platelets ~ 250 mL; 1 unit of FFP ~ 250 mL. ***Albumin after equilibration is similar to 0.9% saline. ****[Na⁺] is 50 mEq/50 mL. *****[Na⁺] is 4000 mEq/mL. Enteral solutions administered Sodium content, mEq/L 0.9% saline gain/loss, mL Free H₂O gain/loss, mL Pulmocare 57.0 [Na⁺] x volume / 154 volume - saline gain/loss Nutren 2.0 56.5 [Na⁺] x volume / 154 volume - saline gain/loss Fibersource HN 52.2 [Na⁺] x volume / 154 volume - saline gain/loss Impact Peptide1.5 50.9 [Na⁺] x volume / 154 volume - saline gain/loss Nutren Pulmonary 50.8 [Na⁺] x volume / 154 volume - saline gain/loss Isosource HN 48.7 [Na⁺] x volume / 154 volume - saline gain/loss Diabetisource AC 46.1 [Na⁺] x volume / 154 volume - saline gain/loss Novasource Renal 41.1 [Na⁺] x volume / 154 volume - saline gain/loss Osmolyte 40.4 [Na⁺] x volume / 154 volume - saline gain/loss Jevity 40.0 [Na⁺] x volume / 154 volume - saline gain/loss Replete Fiber 38.1 [Na⁺] x volume / 154 volume - saline gain/loss Ensure 36.8 [Na⁺] x volume / 154 volume - saline gain/loss Nepro 36.7 [Na⁺] x volume / 154 volume - saline gain/loss Peptamen 35.8 [Na⁺] x volume / 154 volume - saline gain/loss Suplena 34.3 [Na⁺] x volume / 154 volume - saline gain/loss Vivonex RTF 30.4 [Na⁺] x volume / 154 volume - saline gain/loss TwoCal HN 15.0 [Na⁺] x volume / 154 volume - saline gain/loss Beneprotein 3.9 [Na⁺] x volume / 154 volume - saline gain/loss Renalcal 3.4 [Na⁺] x volume / 154 volume - saline gain/loss Other enteral solution* Enter [Na⁺] [Na⁺] x volume / 154 volume - saline gain/loss *Determine whether IV medications are in 0.9% saline or D5W.

Pearls / Pitfalls

Normal saline may not always be the most appropriate replacement fluid, depending on the clinical scenario (see Next Steps for details). Water has a minimal effect on volume in decompensated heart failure, but does cause changes in serum sodium concentrations ( Konstam 2007 ).

Management

Principles for treatment of concurrent sodium and water disorders: Hyponatremia Normal plasma [Na+] Hypernatremia Hypovolemia* Give isonatremic solution for volume expansion. Replace ongoing sodium losses. Restrict free water. Do not replace water losses (unless plasma [Na+] rises too rapidly). Give isonatremic solution for volume expansion. Replace ongoing sodium and free water losses. Give isonatremic solution for volume expansion. Replace ongoing sodium losses. Replace ½ free water deficit (decrease [Na+] <8-10 mEq/L per day). Replace ongoing water losses. Euvolemia* Replace ongoing sodium losses with isonatremic solution. Loop diuretic to impair urine concentrating ability. Restrict free water. Do not replace water losses. Replace ongoing sodium and free water losses. Replace ongoing sodium losses with isonatremic solution. Replace ½ free water deficit and all ongoing free water losses. Hypervolemia* Restrict sodium. Loop diuretic for volume and impaired urine concentrating. Restrict free water. Do not replace ongoing free water losses. Restrict sodium. Loop diuretic for volume overload. Replace ongoing free water losses. Restrict sodium Loop diuretic for volume overload. Replace ½ free water deficit and all ongoing free water losses. *The patient’s volume status requires assessment based on the clinical findings. Table and figure adapted from Kaptein Clinical Nephrology 2016 . Examples: A patient with heart failure and anemia with hypernatremia is being treated with oral “fluid” restriction and diuretics. Q: What is the most likely consequence? A: Most oral liquids are primarily free water. So you have restricted free water which will worsen hypernatremia, but not improve the heart failure. The patient has 2 liters of urine output. Q: What is the free water loss? A: Approximately 1 liter. The patient has 1 liter of ultrafiltrate removed by hemodialysis. Q: What is the free water loss? A: Minimal. A patient with heart failure and anemia with hypernatremia receives 1 unit of pRBCs (350 mL). Q: How much urine output with a diuretic is necessary to be volume even? A: Saline equivalent volume of pRBCs is 2.8 times the volume of pRBCs, and urine output with a diuretic is ½ of 0.9% saline, so urine output must be approximately 5 to 6 times the volume of pRBCs given to be volume even. Q: How much ultrafiltrate is necessary to be volume even? A: Saline equivalent volume of pRBCs is 2.8 times the pRBC volume given so approximately 1 liter of ultrafiltration is required since ultrafiltrate is approximately 0.9% saline.

Advice

Volume replacement may include sodium-containing solutions like 0.9% saline, sodium bicarbonate, buffered solutions like Ringer’s lactate, Plasmalyte, and blood products including albumin, fresh frozen plasma, platelets, and packed red blood cells. Free water replacement may include oral or nasogastric solutions which contain primarily water, or IV 5% dextrose in water. Remember, packed RBCs remain in the intravascular compartment, while all other inputs and losses equilibrate between the intravascular and extravascular compartment.