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EBV is estimated from body weight using age- and sex-stratified factors, reflecting the known decline in blood volume per kilogram from infancy through old age.

Adiposity correction (adults). Adipose tissue is poorly vascularised, so blood volume per kilogram falls as BMI rises — actual-weight factors overestimate EBV in obese patients by 20–35%. The table values above hold at a normal BMI (~22); above that, the factor is scaled by the Lemmens indexed-blood-volume shape, anchored to the age/sex table so it stays continuous. Underweight patients are not inflated. Requires height; children are not adjusted.

Patient parameters auto-fill with 50th percentile reference values when age is entered. All values are editable.

Hb colour thresholds on the vitals strip are age-stratified to reflect physiologically appropriate transfusion triggers.

Used to calculate the fasting deficit (at full rate) and the intraoperative metabolic requirement for paediatric patients ≤10 kg.

GA reduces metabolic rate by ~25–50%. Reduced rates for adults and adolescents; paediatric patients ≤10 kg use full Holliday-Segar (conservative).

Accumulated fluid loss during NPO period at Holliday-Segar rate. Distributed across the first 3 intraoperative hours.

Contemporary evidence suggests deficits are smaller than historically assumed. The toggle in Patient Setup reflects this variability.

Evaporative losses from surgical exposure. Varies substantially with surgery type and extent.

The balance sheet is expressed in crystalloid-equivalents. Under GA, only ~33% of infused crystalloid remains intravascular (Hahn volume kinetics). Colloids, albumin, PRC, FFP, cryo, and platelets are 100% intravascular — ~3× as effective as crystalloid per mL.

RBC mass balance, integrated in 10-minute steps. Blood lost at any moment carries the current haemoglobin, not the baseline — so losses compound (exponential decay under isovolaemic replacement) rather than falling linearly to zero at one blood volume. FFP, cryo and platelets expand plasma volume without contributing RBCs.

Isovolaemic check: losing one full blood volume with volume-for-volume replacement leaves e⁻¹ ≈ 37% of red cell mass. Protein-free water (urine, drainage) leaves the extracellular space at the same 33% vascular share that crystalloid enters it, so replacing urine mL-for-mL with crystalloid is volume-neutral. Fasting, maintenance and insensible are balance-sheet terms and do not drive the vascular model.

Extended Hiippala dilution model. Clotting-factor mass is tracked in "mL of normal plasma equivalent" and lost with plasma at its current concentration each step (compounding), using the same intravascular volume as the Hb model.

Fibrinogen tracked with a dedicated mass balance (grams) using the same corrected plasma volume. Fibrinogen is the first coagulation factor to reach critical levels during haemorrhage.

Cryoprecipitate content varies widely by supplier (Canada ~366 mg/10 mL; USA ~250 mg/15 mL; Australia ~320 mg/36 mL), so it is entered in units; mL entry is converted at the Canadian Blood Services figure. Fibrinogen concentrate dosing: 3–4 g adult · 70 mg/kg paediatric (RiaSTAP/Haemocomplettan) when baseline is unknown.

EBV-based platelet mass balance. Total platelets in the body = count × EBV, depleted proportionally with blood loss, restored by transfusion. Scales correctly with patient size.

Platelet product is ~65% plasma by volume, contributing partial factor mass and ~2 g/L fibrinogen to the coagulation model. Citrate modelled at 0.8× per 250 mL unit (slightly less than PRC).

Ca²⁺ is modelled as a mass-balance with physiological buffering. Total plasma Ca²⁺ is ~2.4 mmol/L: ~45% ionized, ~40% albumin-bound, ~15% complexed. Crystalloid dilutes albumin simultaneously — less binding releases bound Ca²⁺, partially buffering the ionized drop. Blood loss alone leaves Ca²⁺ concentration unchanged (mass and volume fall proportionally). Citrate is cleared by the liver within about an hour, so its effect depends on the rate of product administration, not the cumulative total. Donor plasma (FFP, cryo, platelets) carries a normal calcium load, bound on arrival and ionised as citrate clears; PRC additive solution carries none.

Citrate in blood products chelates Ca²⁺, causing hypocalcaemia during rapid transfusion. CaCl₂ preferred via central line; Ca gluconate safe peripherally.

TXA inhibits plasminogen activation. Benefit is time-sensitive — CRASH-2 demonstrated no benefit beyond 3 hours from bleeding onset.

Volume of packed red cells to raise Hb from current to target level. PRC Hb assumed 200 g/L (~60–65% haematocrit).

Saved cases are kept in this browser's local storage only — nothing leaves the device unless you export it. Each record freezes the patient setup, every hour's entries, any actual labs entered, and the estimates as computed by the app version at the time of saving, so later model revisions never silently rewrite historical data. Reopening a case recomputes live with the current model; the CSV keeps the frozen values and records the app version.

Enter no patient identifiers (name, MRN, DOB). The paired estimate/actual columns are the dataset for validating and recalibrating the models. Back up to JSON before clearing site data or changing devices.

Saved cases are kept in this browser's local storage only — nothing leaves the device unless you export it. Each record freezes the patient setup, every hour's entries, any actual labs entered, and the estimates as computed by the app version at the time of saving, so later model revisions never silently rewrite historical data. Reopening a case recomputes live with the current model; the CSV keeps the frozen values and records the app version.

Enter no patient identifiers (name, MRN, DOB). The paired estimate/actual columns are the dataset for validating and recalibrating the models. Back up to JSON before clearing site data or changing devices.

All values are estimates only based on mathematical models. They support clinical decision-making and do not replace direct patient assessment or laboratory results. Coagulation, Ca²⁺, and Hb estimates must be confirmed with point-of-care or laboratory testing before initiating blood product or calcium therapy. Intended for use by qualified anaesthesia professionals.