NPMS obstetrical patient safety bundle
The proposed NPMS VTE reduction bundle is comprised of 4 elements.7 The first is “readiness,” which essentially calls for every US obstetrical unit to develop a risk assessment strategy at 4 time points in pregnancy: 1) first prenatal visit; 2) all antenatal admissions; 3) immediate postpartum state; and 4) hospital discharge. The NPMS authors suggest using of one of 2 VTE risk scoring systems. The modified Caprini Risk Assessment Model quantifies VTE risks among perioperative patients assigning points for various risk factors including pregnancy and the first postpartum month.9 However, the difference in VTE occurrence between the highest and lowest Caprini categories is modest, 1.94% versus 0%, though the model did identify pregnancy and the puerperium to be a major VTE risk period (odds ratio 8.32; 95% CI:1.02–67.8).
The Padua Prediction Score was developed to assess VTE risk among nonobstetrical Italian internal medicine patients.10 Again points were assigned for various thrombotic risk factors, none of which were pregnancy-related, and patients designated as either at high or low risk, among whom VTE occurred in 7.5% and 0.3%, respectively. These scoring paradigms’ predictive accuracy is compromised by the variable use of various mechanical and pharmacological thromboprophylaxis among the populations studied.
The second element of the NPMS bundle is “recognition” of at-risk patients using risk assessment strategies. The authors reviewed criteria from ACOG, the American College of Chest Physicians (ACCP), and that of the RCOG, described above.
The third element, “response,” emphasizes that at-risk patients receive appropriate thromboprophylaxis. The NPMS authors base recommendations on a selective mix of Caprini, Padua, ACOG, ACCP, and RCOG strategies that can be divided into 5 categories:
Outpatient antepartum patients
They suggest that antepartum patients who have had multiple prior VTE episodes, or 1 prior VTE event associated with either a co-existent high-risk inherited thrombophilia or APA syndrome, receive treatment doses of LMWH or unfractionated heparin (UFH). Prophylactic doses of LMWH or UFH are indicated in those with a prior idiopathic VTE, prior VTE associated with a low-risk inherited thrombophilia, prior VTE while pregnant or taking oral contraceptives (OCs), or in patients without prior personal VTE history who have a family history of VTE associated with a high-risk thrombophilia or APA syndrome.
Patients with antepartum hospitalizations
All patients not already receiving outpatient thromboprophylaxis, admitted to the hospital for at least 72 hours, and who are not at risk for bleeding should receive prophylactic LMWH or UFH. The latter is preferred if delivery is imminent. Hospitalized antepartum patients at risk for bleeding should receive pneumatic compression devices in lieu of heparin.
Patients with vaginal deliveries
Among such patients with a history of VTE or a thrombophilia (the NPMS authors do not discriminate between high- and low-risk types), pneumatic compression devices should be used in the intrapartum period followed by LMWH or UFH postpartum prophylaxis. Women at high risk for VTE based on RCOG or Padua criteria should also be considered for LMWH or UFH.
Patients with cesarean deliveries
All such patients not otherwise receiving LMWH or UFH should have pneumatic compression devices until fully ambulatory. The NPMS authors also recommend pharmacological thromboprophylaxis for women with risk factors based on either RCOG or Caprini criteria. However, they go further to state “Given the challenges in consistently identifying women with risk factors and issues related to poor compliance with mechanical devices, hospitals may choose a strategy in which all women undergoing cesarean birth receive postoperative thromboprophylaxis with unfractionated or low-molecular-weight heparin unless there is a specific contraindication.” This strategy would necessitate that more than a million US women each year receive post-cesarean heparin for some unspecified interval.
The NPMS authors recommend 6 weeks of treatment with LMWH or UFH therapy for postpartum patients with multiple prior VTE episodes or those with a prior VTE and either a high-risk inherited thrombophilia or APA syndrome. Six weeks of prophylactic LMWH or UFH therapy is recommended for women with a prior idiopathic or “provoked” VTE, one occurring while pregnant or on OCs or in the setting of a low-risk thrombophilia. For patients without a prior VTE, 6 weeks of prophylactic heparin therapy is also recommended for those with a family history of VTE associated with a high-risk thrombophilia, a family history of VTE when the patient herself has a low-risk inherited thrombophilia, and in any patient with a high-risk thrombophilia or APA syndrome.
The authors also address the thorny issue of heparin use in pregnant patients needing neuraxial anesthesia and recommend delaying anesthesia for 4 hours and preferably 6 hours after a prophylactic (5,000 U) dose of UFH, 6 hours after a dose of therapeutic UFH, 12 hours after a prophylactic LMWH dose, and 24 hours after a therapeutic LMWH dose. They provide recommendations for delays in postpartum epidural catheter removal or spinal needle placement after various doses of LMWH and UFH. They recommend stopping low-dose aspirin therapy for the prevention of pre-eclampsia at 35 to 36 weeks’ gestation.
The final element of the NPMS bundle is “Reporting and Systems Learning.” The authors opine that institutional and practitioner adherence to these policies be periodically audited and that each VTE event be reviewed to determine if care was optimal. Complications of thromboprophylaxis should also be reviewed and reported.