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Flow Calculator

Calculate required blood flow using BSA or patient weight.

Input Parameters

Select a method and enter patient data.

Clinical Context & Significance

Establishing an appropriate pump flow is one of the most fundamental tasks during cardiopulmonary bypass. The goal is to provide sufficient systemic oxygen delivery ($DO_2$) to meet the metabolic demands of the tissues while minimizing the traumatic effects of the extracorporeal circuit on blood components.

BSA Calculation

This tool uses the DuBois & DuBois formula: $BSA (m^2) = 0.007184 \times Height(cm)^0.725 \times Weight(kg)^0.425$. While multiple formulas exist (Mosteller, Haycock), the DuBois formula remains a clinical standard in cardiac surgery.

Standard Targets

  • Adults: Typical Cardiac Index of 2.2 - 2.4 L/min/m².
  • Pediatrics: Higher indexed flows are required due to higher relative metabolic rates (2.8 - 3.2 L/min/m²).
  • Temperature: indexed flow requirements decrease as the patient is cooled, following the $Q_10$ principle.

Clinical Note: While BSA-based flow is a starting point, true adequacy of perfusion should be assessed using mixed venous saturation ($SvO_2$), lactate levels, and oxygen delivery ($DO_2I$) — see the GDP Dashboard for advanced monitoring.

Clinical Guide to Body Surface Area (BSA) & CPB Blood Flow Rates

Physiological Principles & Clinical Context

Cardiopulmonary bypass (CPB) aims to maintain systemic perfusion and cellular respiration in the absence of physiological heart action. To establish appropriate perfusion goals, the clinical perfusionist calculates the patient's Body Surface Area (BSA), which correlates cellular metabolic demands with somatic size. The target systemic blood flow rate is then determined by multiplying the BSA by a desired Cardiac Index (typically 2.2 to 2.4 L/min/m² for normothermic adults, or up to 3.0 L/min/m² for pediatric patients). Precise flow rates prevent cerebral hyperperfusion or systemic hypoperfusion during bypass.

Clinical Targets & Safe Ranges

  • •Standard Cardiac Index: 2.2 to 2.4 L/min/m² for normothermic adult bypass procedures.
  • •Pediatric Cardiac Index: 2.5 to 3.0 L/min/m² to meet elevated basal metabolic requirements.
  • •Cerebral Perfusion Flow: Typically 500 to 1000 mL/min during selective anterograde cerebral perfusion.
  • •Hypothermic flow reduction: Standard reductions can be planned under deep hypothermia (e.g., 1.2 to 1.8 L/min/m²) based on metabolic Q10 principles, provided DO₂I is closely monitored.

Mathematical Formulation

  • ƒDuBois Formula: BSA (m²) = 0.007184 × Height (cm)^0.725 × Weight (kg)^0.425
  • ƒMosteller Formula: BSA (m²) = √[ (Height (cm) × Weight (kg)) / 3600 ]
  • ƒBSA-Based Target Flow: Target Flow (L/min) = BSA (m²) × Desired Cardiac Index (L/min/m²)
  • ƒWeight-Based Target Flow: Target Flow (L/min) = [ Weight (kg) × Flow Index (mL/kg/min) ] / 1000

Academic & Clinical References

  1. DuBois D, DuBois EF. A formula to estimate the approximate surface area if height and weight be known. Arch Intern Med. 1916;17:863–871.
  2. Mosteller RD. Simplified calculation of body-surface area. N Engl J Med. 1987;317(17):1098.
  3. Gravlee GP, Davis RF, Kurusz M, Utley JR. Cardiopulmonary Bypass: Principles and Practice. 4th ed. Philadelphia: Lippincott Williams & Wilkins; 2015.