No influence of large volume blood loss on serum vancomycin concentrationsduring orthopedic procedures

We prospectively studied orthopedic patients with either targe or small blo od loss who also received vancomycin prophylaxis to determine the effect of intraoperative volume shifts on serum vancomycin concentrations. There wer e 6 index patients in the large blood loss group (greater than 2 L), and 7 in the control group (less than 2 L). Mean estimated blood loss for index a nd controls was 4.4 L and 1.0 L, respectively. Mean intraoperative fluid re suscitation, excluding blood products, was 12.4 Land 5.1 L, respectively. There was a modest inverse correlation between blood loss and intraoperativ e serum half-life of vancomycin. Although controls maintained slightly high er intraoperative vancomycin concentrations at each time-point, there was n o statistically significant difference between the groups with regard to ab solute concentrations or rate of decline. After 8 hours, the serum vancomyc in concentration exceeded the MIC-90 for Staphylococcus aureus by approxima tely eightfold in all but one case patient. This was a morbidly obese patie nt with massive blood toss. Thus, blood loss during orthopedic procedures h as minimal effects on intraoperative kinetics of vancomycin. Redosing is ra rely indicated, although a preoperative 1.5 gram-dose should be considered for patients weighing more than 90 kg.