The tube is a real one-compartment pharmacokinetic curve rendered along the time axis (t = 0 is the surgical incision). After the infusion completes, tissue concentration rises to a peak and then decays by true first-order elimination — concentration halves every drug half-life, exactly as it does in blood plasma:
C(τ) = Cpeak · 0.5^((τ − τpeak) / t½) τ = minutes since infusion start
redose triggered when τ since last dose ≥ 2·t½ (only if the case is still open)
after blood loss > 0 mL: C ×= (1 − 0.35·bloodLoss/3000) once, mid-procedure
Cefazolin (t½ ≈ 1.7 h) needs a redose after roughly 2×1.7 ≈ 3.4 h if the case runs long; vancomycin's much longer half-life (≈ 6 h) rarely triggers one. The translucent horizontal plane marks the minimum-inhibitory-concentration (MIC) reference at 25% of peak — two half-lives of decay — the same threshold guidelines use to justify the "redose at 2×t½" rule. The vertical blue plane is the incision instant; the teal/amber shelf on the floor is the guideline-compliant infusion-start window for the selected agent (15–60 min before incision for cefazolin, 60–120 min for vancomycin).
- Infusion start — slides the whole decay curve left/right relative to the fixed incision plane; watch the curve's height at the blue plane change.
- Agent — swaps both the half-life (decay slope) and the compliant window (floor shelf position).
- Procedure duration — extends the timeline past incision; once it crosses 2 half-lives from the last dose, a purple redose marker appears and the curve resets to peak.
- Blood loss — applies a one-time dilution drop to the curve partway through a sufficiently long procedure, visible as a step down in the tube.
- Drag the background to orbit the camera; scroll to zoom.