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

We prospectively studied orthopedic patients with either large or small blood loss who also received vancomycin prophylaxis to determine the effect of intraoperative volume shifts on serum vancomycin concentrations. There were 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 and controls was 4.4 L and 1.0 L, respectively. Mean intraoperative fluid resuscitation, excluding blood products, was 12.4 L and 5.1 L, respectively. There was a modest inverse correlation between blood loss and intraoperative serum half-life of vancomycin. Although controls maintained slightly higher intraoperative vancomycin concentrations at each time-point, there was no statistically significant difference between the groups with regard to absolute concentrations or rate of decline. After 8 hours, the serum vancomycin concentration exceeded the MIC-90 for Staphylococcus aureus by approximately eightfold in all but one case patient. This was a morbidly obese patient with massive blood loss. Thus, blood loss during orthopedic procedures has minimal effects on intraoperative kinetics of vancomycin. Redosing is rarely indicated, although a preoperative 1.5 gram-dose should be considered for patients weighing more than 90 kg.