Effect of Heparin on Activated Partial Thromboplastin Time in Patients Undergoing Gynecologic or Obstetric Surgery

Abstract

The exaggerated prolongation of the activated partial thromboplastin time (APTT) by heparin prophylaxis for postoperative thromboembolism may cause bleeding complications. We examined the effects of various doses of unfractionated heparin on the APTT in patients who underwent a gynecologic or obstetric operation. A total of 68 patients who underwent a gynecologic operation (n = 47) or a cesarean section (n = 21) with risk factors for thromboembolism received a continuous intravenous infusion of unfractionated heparin (110–285 IU/kg/day) after surgery until the patient was mobilized the next day. A group of 61 postoperative patients who did not receive heparin served as controls. The APTT was measured in these 129 patients preoperatively and on postoperative day 1. A clinical deep vein thrombosis occurred in only 1 patient, who was in the control group. No bleeding complications occurred in any patient. The percent change in the APTT was significantly correlated with the dose of heparin administered (p < 0.001). Compared with the control group, the mean APTT was not prolonged in the patients who received heparin at 110–149 IU/kg/day. It was prolonged significantly in the patients who received heparin at greater than 150 IU/kg/day. An exaggerated prolongation of the APTT, defined as an APTT greater than 150% of the preoperative value, was found in 0 of 32 patients in the 110–149 IU/kg/day group, 1 of 28 patients (3.6%) in the 150–199 IU/kg/day group and 2 of 8 patients (25%) in the 200–285 IU/kg/day group. The continuous postoperative administration of intravenous heparin at less than 200 IU/kg/day does not result in an exaggerated prolongation of the APTT.

Prolonged activated partial thromboplastin time in thromboprophylaxis with unfractionated heparin in patients undergoing cesarean section

“… 5 demonstrated that subcutaneous unfractionated heparin adjusted to keep APTT between 31.5 and 36 s (110–130%) induced a significant reduction in the incidence of postoperative DVT after total hip replacement without increasing bleeding complications. In a large study of heparin‐thromboprophylaxis, unfractionated heparin was subcutaneously administered to maintain APTT at 2–5 s above the institute control, 11 which corresponded to 31.9–34.9 s in the present study population, agreeing well with the present postoperative APTT median of 33.8 s. Our previous data, 7 together with a review of the published reports, suggested that APTT should be adjusted to between 110–150% of the baseline after gynecologic surgery and CS 7 . Combining all of these data, APTT should be adjusted to at most <45 s, within approximately 150% of the baseline level.…”

“…Prolongation of APTT >150% was found in 0% (0/32), 3.6% (1/28), and 25% (2/8) in the 110–149, 150–199, 200–285 IU/kg/day groups, respectively, and with the former two groups combined together (110–199 IU/kg/day), exaggerated prolongation of APTT occurred in 1.7% (0 + 1/32 + 28) 7 . The body mass index for the CS group ( n = 21) in our previous study was 31.4 just before delivery, 7 and thus 110–199 IU/kg/day may correspond to the heparin dose used presently, which is 10 000 IU/day. Thus, the previously reported incidence rate of exaggerated APTT prolongation of 1.7% 7 was lower than our value of 7.1%.…”

“…Thus, clarifying the incidence rate of APTT of >150% is clinically important, but few studies have focused on it. Previously, our group 7 studied APTT prolongation in women with intravenous continuous unfractionated heparin administration after gynecologic surgery or CS. Prolongation of APTT >150% was found in 0% (0/32), 3.6% (1/28), and 25% (2/8) in the 110–149, 150–199, 200–285 IU/kg/day groups, respectively, and with the former two groups combined together (110–199 IU/kg/day), exaggerated prolongation of APTT occurred in 1.7% (0 + 1/32 + 28) 7 .…”

“…Previously, our group 7 studied APTT prolongation in women with intravenous continuous unfractionated heparin administration after gynecologic surgery or CS. Prolongation of APTT >150% was found in 0% (0/32), 3.6% (1/28), and 25% (2/8) in the 110–149, 150–199, 200–285 IU/kg/day groups, respectively, and with the former two groups combined together (110–199 IU/kg/day), exaggerated prolongation of APTT occurred in 1.7% (0 + 1/32 + 28) 7 . The body mass index for the CS group ( n = 21) in our previous study was 31.4 just before delivery, 7 and thus 110–199 IU/kg/day may correspond to the heparin dose used presently, which is 10 000 IU/day.…”

“…Thromboprophylaxis with heparin, especially with unfractionated heparin, sometimes induces hemorrhagic complications, for which previous studies have mainly targeted Caucasian populations 2,5,6 . Little data are available for the Japanese population 7 . Previously, our group showed that prophylactic intravenous infusion of unfractionated heparin did not lead to severe hemorrhagic complications in Japanese women undergoing gynecological/obstetrical surgery, but some patients showed a marked prolongation of activated partial thromboplastin time (APTT); 7 however, the study population was small ( n = 68), especially after CS ( n = 21) 7 …”