Use of thromboelastography to guide thromboprophylaxis after caesarean section.

BACKGROUND

Thromboprophylaxis is commonly required following caesarean section. However the effect of thromboprophylactic dosages of subcutaneous heparin on coagulation is unknown because conventional laboratory tests are largely unaffected. The aim of this study was to determine if thromboelastography could detect and quantify the effect of unfractionated heparin on coagulation profile when given at the time of surgery.

METHODS

Nineteen women undergoing elective caesarean section were recruited. Blood samples collected before and after administration of subcutaneous unfractionated heparin 7500 IU underwent thromboelastography using both plain and heparinase cuvettes. Anti-factor Xa levels were also measured.

RESULTS

There was a significant difference in R times between plain and heparinase samples (-10.6%, P=0.0072) indicating that thromboelastography could detect an effect of unfractionated heparin. Compared to baseline there were significant decreases of R times in plain (-20.4%, P=0.033) and heparinase (-28.8%, P=0.0001) samples despite the administration of unfractionated heparin. Anti-factor Xa levels were virtually undetectable (mean 0.01 U/mL).

CONCLUSION

Thromboelastography was able to detect and quantify the effect of unfractionated heparin on blood coagulability, an effect not detected by conventional laboratory tests. Thromboelastography demonstrated a pro-coagulant effect of surgery that was only partially mitigated by the use of unfractionated heparin. In this study, at a dose of 7500 IU subcutaneous unfractionated heparin appears to have little anticoagulant effect.