Introduction: Venous thromboembolic events (VTE) are a concern for morbidity and mortality in patients undergoing laparoscopic bariatric surgery. While VTE prophylaxis is recommended in bariatric surgery, data regarding monitoring and appropriate dosing of low molecular weight heparins are limited. Enoxaparin prophylactic doses from 30 mg to 60 mg q12h have been used in this population. Our hypothesis was that higher prophylactic enoxaparin doses (60 mg) would yield more appropriate anti-Xa concentrations than the 40 mg dosage in bariatric surgery patients.
Methods: Patients undergoing laparoscopic bariatric surgery between during a 5 month period at 1 institution by 2 surgeons were was either enoxaprin 40 mg or 60 mg every 12 hours. Anti-Xa levels were obtained four hours after first and third doses. Therapeutic levels were defined as 0.18 to 0.44 units/mL. Paired and unpaired t-tests as well as chi-squared tests were utilized for statistical analysis as appropriate.
Results: First dose mean anti-Xa concentrations were 0.173 and 0.261 in the 40 mg and 60 mg groups respectively (p < 0.005). Compared to third dose mean anti-Xa levels which were 0.21 and 0.43 respectively (p < 0.001). After the third dose of enoxaparin there was a statistically significant difference in the percentage of patients with anti-Xa concentrations that remained sub-therapeutic, 44% vs. 0% in the 40 mg vs. 60 mg group (p = 0.02). However, there were no supratherapeutic anti-Xa concentrations 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; however, there were no bleeding events in these patients.
Conclusion: Enoxaparin 60 mg every 12h was superior to 40 mg every 12 hours in achieving therapeutic anti-Xa concentrations and avoiding subtherapeutic anti-Xa concentrations. However, there were a number of supratherapeutic levels in the 60 mg group. Future studies with larger numbers evaluating the relationship of anti-Xa concentrations and outcomes in morbidly obese patients are needed.
Program Number: P056