Transfusion & hematology

Surgical blood loss calculator

Estimate measured blood loss from suction canister, sponge weight, and lavage subtraction. Convert that loss into mL/kg and percent estimated blood volume. Educational decision-support only.

Assumes 1 g sponge weight gain is approximately 1 mL blood/fluid. Subtract lavage only when it was captured in the measured total.

Educational support only. Verify intraoperative estimates clinically.
Safety checks
  • Blood loss estimates are imprecise and must be interpreted with perfusion parameters.
  • Do not delay transfusion planning in unstable patients while refining arithmetic.
  • Verify whether lavage, urine, ascites, or other fluids contaminated the estimate.
  • This tool does not determine transfusion need by itself.
Basis and limits
  • Formula: blood loss = max(suction - lavage, 0) + max(wet sponge weight - dry sponge weight, 0).
  • Estimated blood volume: default dog 90 mL/kg, cat 60 mL/kg. Use custom values when hospital protocol differs.
  • Percent loss: blood loss / estimated total blood volume × 100.
Formula audit trail

Calculation steps will appear here for verification.

Related tools
Transfusion Volume CalculatorEstimate PRBC or whole blood volume.Fluid Bolus CalculatorResuscitation bolus planning.Normal ValuesPCV, perfusion, and vital references.