In a clinical in vivo study, wound blood collected from an autologous reinfusion drain of patients undergoing elective total knee arthroplasty was examined to investigate if hydrogen peroxide bone surface preparation had an adverse effect on blood destined to be reinfused. The post-operative drain blood of thirty-eight patients was collected after pre-implantation bone preparation being performed either with or without the use of hydrogen peroxide. Filtered drain blood samples were analyzed and mean results for treatment / control groups respectfully were: haemoglobin (g/L) 98.6/100.9, p=0.7221; haemoglobin change from baseline (g/L) -39.1/-32.9, p=0.2117; MCV (fL) 94.6/93.1, p=0.2897; MCV change from baseline (fL) 2.0/2.5, p=0.6417; potassium (mmol/L) 4.5/4.6, p=0.8212; free haemoglobin (g/L) 1.2/1.3, p=0.4387; methaemoglobin (%) 0.2/0.2, p=0.8112; presence of echinocytes (%) 14/18, p=1.0000. These were all within safe limits for reinfusion. Under the study conditions, application of hydrogen peroxide followed by thorough lavage of the knee joint did not appear to result in any untoward degradation of the extravasated blood that might preclude its use for postoperative autologous drainage blood reinfusion.