In presenting the Consensus Bundle on venous thromboembolism (VTE), published in this edition of Anesthesia & Analgesia,a the National Partnership for Maternal Safety (NPMS) has taken an important step toward mitigating a key risk to patient safety: maternal death from VTE.1 The authors should be congratulated for critically reviewing the relevant literature and for synthesizing the existing diverse guidelines into a plan that includes 4 implementable domains: readiness, recognition, response, and reporting systems. As with any new patient care-related recommendations, the introduction of the bundle brings with it anticipated benefits for obstetric patients but also significant unintended consequences.
Specifically, if the reduction of the maternal VTE rate is associated with the increased risks related to neuraxial anesthesia, such as epidural hematomas and increased use of obstetric general anesthesia, then this change in maternal care could undermine decades of safety advancements in obstetric anesthesia.
WHAT ARE THE UNINTENDED CONSEQUENCES OF THE BUNDLE?
Enhanced screening and expanded indications for thromboprophylaxis increase the odds that a pregnant woman will have recently received a dose (low or high) of anticoagulant when her need for urgent cerclage, nonelective cesarean delivery, or labor analgesia arises. In addition, some of these women on “prophylactic” regimens will now receive a dose of up to 10,000 U of unfractionated heparin subcutaneous twice a day in the third trimester, or more than 40 mg per day of enoxaparin subcutaneous. Complicating the situation further, a recent guideline from the American Society of Regional Anesthesia available as a mobile app, but as yet unpublished, suggests a 4- to 6-hour delay before block placement or epidural catheter removal after a low-dose (ie, 5000 U) unfractionated heparin subcutaneous administration.b Taken together, these concomitant practice advisories constrain anesthetic management and will likely prompt anesthesia providers to deny or delay providing neuraxial anesthesia for fear of causing an epidural hematoma, in favor of less-effective alternative methods for labor analgesia and general anesthesia for surgical procedures.
HOW TO EVALUATE AND MITIGATE COMPETING RISKS?
How should anesthesiologists balance the (infrequent and truly immeasurable) risk of an epidural hematoma in women receiving pharmacologic thromboprophylaxis (commission) against the risks associated with the absence of neuraxial analgesia and anesthesia (omission)?
In a recent publication, the disparate yet analogous risks of receiving or not receiving neuraxial anesthesia in obstetric patients with thrombocytopenia (platelet count of <100,000/mm3) were evaluated.2 Similar to the case of the pregnant woman receiving thromboprophylaxis, the concern was how to balance the risk of proceeding with neuraxial anesthesia and possibly increasing the likelihood of an epidural hematoma because of impaired coagulation versus proceeding with general anesthesia with its attendant risks.3 In combined data from 2 institutions (173 cases) and from previously published series (326 cases) of thrombocytopenic women receiving spinal or epidural anesthesia, there were no cases of epidural hematoma (95% confidence interval, 0%–0.6%) compared with a much greater, aggregate serious morbidity rate of 6.5% (95% confidence interval, 2.1%–14.5%) among women receiving obstetric general anesthesia.2
Unfortunately, there is limited data to support precise recommendations for VTE prophylaxis dosing in pregnant or postpartum women or the appropriateness of initiating neuraxial anesthesia in this context. The existing guidelines from professional societies for initiating neuraxial anesthesia for a broad range of anticoagulant doses and drugs do not integrate the more favorable pharmacokinetic profile of anticoagulation in pregnancy and do not consider the competing risks of denying neuraxial blockade in the obstetric clinical context. To bridge this gap, the Society of Obstetric Anesthesia and Perinatology (SOAP) has convened a multinational, multidisciplinary task force to produce a consensus framework to guide decision making on anesthetic management in pregnant and postpartum women on thromboprophylaxis, incorporating the unique clinical and physiologic aspects of this population. The core principles that govern the anesthetic care of these women are the same as those invoked in our everyday practice: consideration of all available evidence, multidisciplinary collaborative care planning, and focus on optimal communication.
In the meantime, we applaud the NPMS committee for endorsing the lower dose (5000 U unfractionated heparin, subcutaneous, twice daily) or, alternatively, mechanical compression as acceptable thromboprophylaxis for hospitalized antepartum women who are often at high risk of early and precipitous delivery. Contemporary obstetric and anesthesia practice in the United States has been to administer 5000U of unfractionated heparin, subcutaneous, twice daily and not delay neuraxial procedures. The epidural hematoma rate in obstetric patients has historically been extremely low,4–8 and the recent SOAP Serious Complication Repository confirms a 1:251,463 rate.9 For patients receiving higher doses of unfractionated heparin (ie, >10,000 U per day), it is currently suggested that an activated partial thromboplastin time guide the appropriate time to administer a neuraxial anesthetic. We should acknowledge that this approach has significant limitations; we do not know when peak plasma levels of unfractionated heparin occur, particularly in morbidly obese women with variable subcutaneous absorption, and the reliability of activated partial thromboplastin time to predict bleeding risk in the term pregnant women is not well established. Nevertheless, we are likely to continue to rely on this laboratory test, which has served us well in our practice to date, until there is an evidence-based alternative.
For thromboprophylaxis with low molecular weight heparin (LMWH), current recommendations suggest a 12-hour delay for low-dose LMWH, or 24-hour delay for high-dose LMWH, before the safe administration of neuraxial anesthesia.8 However, “gray zones” of uncertainty remain, for example, if a patient requests an epidural for labor analgesia between 10 and 12 hours after a low dose of LMWH. Such scenarios present patients and providers with difficult choices that will require proactive planning, excellent communication, and ultimately, decision making that accounts for the competing risks of anesthesia for delivery if a neuraxial anesthetic is to be denied.
Labor without neuraxial analgesia increases the risk for severe pain, circulating catecholamines, and the likelihood of a general anesthetic in the event of an urgent cesarean delivery, which can be particularly detrimental to a mother with severe preeclampsia and her fetus. Recent analyses of state-based temporal trends suggest that even though the frequency of severe morbidity associated with neuraxial anesthesia decreased, the frequency of severe complications attributed to general anesthesia for cesarean delivery has not changed.10 The risks of general anesthesia are life-threatening. Failed intubation,11 airway obstruction, or hypoventilation, most commonly during emergence and recovery, and postoperative respiratory depression each contribute to the anesthesia-related deaths.12,13 Should neuraxial anesthesia become less common and obstetric general anesthesia become more common, then recrudescence of critical events may emerge in this increasingly high-risk population. Furthermore, although not life-threatening, cesarean delivery under general anesthesia carries with it a 1:670 risk of accidental awareness under anesthesia,14 fetal exposure to general anesthesia, increased postoperative pain, and a missed opportunity to experience the birth.
Finally, it is ultimately uncertain how the low-frequency, high-impact risk of VTE compares with those risks associated with the alternatives to neuraxial anesthesia for the average pregnant or postpartum woman; there may be some women (eg, with anatomic features or history of difficult intubation) for whom the risk of airway complications with general anesthesia may outweigh any marginal benefit of more aggressive pharmacologic thromboprophylaxis.
WHAT IS THE RESOLUTION?
We propose that this bundle presents the opportunities for expanded, collaborative care of pregnant, and postpartum women, rather than for restricted anesthetic options. Of critical importance to obstetric anesthesiologists, the bundle supports (1) consistent and proactive multidisciplinary communication about appropriate anticoagulant doses and stop times on the basis of consideration of risks, benefits, and potential restrictions on neuraxial anesthesia, especially if delivery is imminent, and (2) the continued practice of using nonsteroidal antiinflammatory drugs after cesarean delivery with neuraxial anesthesia, despite the addition of low-dose unfractionated heparin or LMWH. The second is important given the vital role of nonsteroidal antiinflammatory drugs in opioid-sparing, multimodal pain management strategies.
As the bundle is rolled out in each institution or health system, obstetric anesthesiologists should be at the table to help formulate local policies and procedures. Anticoagulation status should be addressed at each patient sign-out. Individual patient care plans, particularly in high-risk patients in the gray areas of anticoagulant dosing choices, should be made in consultation with the anesthesia providers and, whenever feasible, with the patients themselves. The SOAP consensus statement will be useful to help anticipate the downstream effects on neuraxial anesthesia readiness based on different anticoagulation scenarios. Well-constructed institutional policies may be needed to make certain that covering teams can successfully carry out individual care plans and limit intraprofessional conflict and confusion. Most importantly, regular, ongoing multidisciplinary communication is required throughout the day and night to ensure that evolving plans for delivery or surgical intervention appropriately inform optimal anticoagulation and anesthetic management. Only in this way, anesthesiologists will be able to continue to provide high-quality neuraxial analgesia and anesthesia for women while supporting the NPMS thromboprophylaxis initiatives.
Name: Lisa Leffert, MD.
Contribution: This author helped write the manuscript.
Name: Ruth Landau, MD.
Contribution: This author helped write the manuscript.
This manuscript was handled by: Jill Mhyre, MD.
a “The Consensus Bundle on Venous Thromboembolism (VTE) is being simultaneously published in Obstetrics & Gynecology, the Journal of Obstetric Gynecologic and Neonatal Nursing, and the Journal of Midwifery & Women’s Health.”
b American Society of Regional Anesthesia and Pain Medicine (2014) ASRA Coags Regional (Version 1.5) [Mobile application]. Available: https://itunes.apple.com/us/app/asra-coags/id858796572?mt=8; accessed July 5, 2016.
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