Background
3% hydrogen peroxide (H2O2) is widely used to irrigate wounds and was observed clinically to be more effective at cleaning off blood than normal saline. Our hypothesis was that this was due to a direct effect of H2O2 on fibrin clot formation and degradation. We decided to investigate the mechanism using an in-vitro model.

Material and Methods
We performed coagulation assays with normal saline, 1% and 3% final concentrations of H2O2 to investigate its effect on fibrin clot formation as determined by spectrophotometer absorbance readings at 425nm wavelength. Effect on fibrinolysis was studied by immersing and agitating blocks of fibrin clot in normal saline, 1%, 3% and 10% H2O2 solutions. We took photographs, samples for protein assay and clot dimensions at set time intervals. We performed scanning electron microscopy on fibrin clots to examine clot structure.

Result
Fibrin clots immersed in 1%, 3% and 10% H2O2 demonstrated 0.09mm3/min (+/-0.14SD, n=4), 0.25mm3/min (+/-0.13SD, n=4) and 0.14mm3/min (+/-0.04SD, n=2) rate of volume loss whereas those immersed in the normal saline increased in volume by 0.02mm3/min (+/- 0.13SD, n=4). H2O2 reduced the rate of initial increase in light absorption, an indicator of fibrin clot formation, in a dose dependent manner (NaCl; 0.20/min, 1% H2O2; 0.08/min, 3% H2O2; 0.02/min).

Conclusion
We have shown that the efficacy of H2O2 in cleaning blood from wounds may be related to its effects on the coagulation pathway, in a concentration dependent manner, by a currently undescribed mechanism.