Comparison of two low-molecular-weight heparin dosing regimens for patients undergoing laparoscopic bariatric surgery

Venous thromboembolic events (VTE) are a morbidity and mortality concern for patients undergoing laparoscopic bariatric surgery. Although VTE prophylaxis is recommended in bariatric surgery, data with regard to monitoring and appropriate dosing of low-molecular-weight heparin are limited. Enoxaparin prophylactic doses ranging from 30 to 60 mg every 12 h have been used for this population. The authors hypothesized that higher prophylactic enoxaparin doses (60 mg) would yield more appropriate heparin antifactor Xa (anti-Xa) concentrations than the 40-mg dosage for bariatric surgery patients.

Patients undergoing laparoscopic bariatric surgery by two surgeons during a 5-month period at one institution received enoxaprin 40 or 60 mg every 12 h. Anti-Xa levels were obtained 4 h after the first and third doses. Therapeutic levels were defined as 0.18 to 0.44 U/ml. Paired and unpaired t-tests and chi-square tests were used for statistical analysis as appropriate.

The first-dose mean anti-Xa concentration was 0.173 U/ml in the 40-mg group and 0.261 U/ml in the 60-mg group (p < 0.005), compared with the third-dose mean anti-Xa levels of 0.21 and 0.43 U/ml, respectively (p < 0.001). After the third dose of enoxaparin, the percentage of patients with anti-Xa concentrations who remained subtherapeutic showed a statistically significant difference: 44% in the 40-mg group versus 0% in the 60-mg group (p = 0.02). However, no supratherapeutic anti-Xa concentrations were observed in the 40-mg group, whereas 57% of the third-dose levels in the 60-mg group were supratheraputic. The highest anti-Xa level was 0.54 U/ml, but none of the patients with this level experienced bleeding events.

Enoxaparin 60-mg every 12 h was superior to a dosage of 40 mg every 12 h in achieving therapeutic anti-Xa concentrations and avoiding subtherapeutic anti-Xa levels. However, the 60-mg group had a number of supratherapeutic levels. Future studies evaluating the relationship of anti-Xa concentrations and outcomes with larger numbers of morbidly obese patients are needed.