Enoxaparin: Regional and Neuraxial Catheter Management

Educational Objectives

The goal of this program is to improve outcomes of regional anesthesia in patients on anticoagulation therapy. After hearing and assimilating this program, the clinician will be better able to:

1. Reduce risks for hemorrhage and nerve injury during regional anesthesia in patients taking anticoagulant agents.
2. Adhere to guidelines for regional anesthesia in patients taking anticoagulant agents.
3. Ensure early detection of neuraxial and perineural hemorrhage.

Summary

Reasons for anticoagulation: patients undergoing major surgery are at significant risk for thrombotic complications; humoral and mechanical effects that interrupt normal physiologic homeostasis persist despite clinicians’ best efforts; reports show 5% to 12% of patients with hip fractures experience fatal pulmonary emboli; a high proportion of patients who present to the emergency department with hip fracture are placed on an anticoagulant agent because the risk for emboli outweighs that associated with these medications; in hospitalized patients, risk for clot-related complications is elevated because of reduced mobility (related to, eg, comorbidities, recent invasive procedures, attachment to tubes and lines, fractures); additionally, surgical procedures induce a hypercoagulable state; risk is compounded in the presence of comorbid conditions

Enoxaparin: approved by the Food and Drug Administration (FDA) in 1993; after its introduction, >30 cases of hematoma-related paraplegia following neuraxial anesthesia (NA), predominantly in elderly women, were reported within a short period; in 1997, the FDA issued a warning about risks associated with NA procedures in patients taking enoxaparin; closed claims reviews demonstrate an increasing number of such events leading to litigation; >60% of closed claims for spinal cord injury involve NA; a retrospective review of 1,500,000 blocks suggested that traumatic needle placement was a significant contributor to these events; many patients had coagulation abnormalities; a large proportion of the incidents were detected at catheter removal (hemorrhages at this time are associated with rapid onset of symptoms)

Quantification of anticoagulant practices: a recent analysis (Bos EME, 2020) concluded that errors in the application of antihemostatic agents (ie, inappropriate timing or dosing) were responsible for a significant number of closed claims; another cited cause was failure of surveillance (ie, delay in diagnosis or misinterpretation of symptoms reported to care providers)

Pharmacokinetics: enoxaparin is commonly used for inpatients and during the preoperative period as bridge therapy for agents with longer half-lives; it is a low-molecular-weight heparin with anti-factor Xa and antithrombin activity; enoxaparin inhibits normal hemostatic functions (eg, release of von Willebrand factor and other factors); measurement of antifactor Xa activity is possible within a relatively short period of time; however, there are currently no clinical recommendations addressing the degree to which factor Xa activity effects the risk-benefit ratio of regional anesthesia procedures; the peak level of enoxaparin is achieved in 3 to 5 hr; the elimination half-life is approximately 3 to 6 hr; there is no renal function decrement; renal insufficiency may create difficulty in predicting the action of enoxaparin and increase the elimination half-life to ≤16 hr; in the absence of clinical trial data, pharmacokinetic data are used to drive clinical recommendations

Guidelines for regional anesthesia: published by the American Society of Regional Anesthesia and Pain Medicine (ASRA) in 2018; enoxaparin is primarily addressed with regard to NA, despite the fact that current practice has shifted to greater reliance on peripheral nerve blocks

Timing of anticoagulant dosing for NA: for patients fully anticoagulated on a treatment dose of enoxaparin, guidelines recommend waiting ≈5 elimination half-lives for resolution of 97% to 98% of the drug's activity; patients on prophylaxis dosing regimens may require only 2 elimination half-lives

To view Dr. Jaffe’s memory aid for enoxaparin, please follow this link:

Non-NA or peripheral nerve blocks: at some placement sites, risk for uncontrolled bleeding is high because compression cannot be applied; this issue is covered in the 2018 ASRA guidelines, but only with regard to para-NA blocks (deep and close to the spine), not superficial peripheral blocks

Peri-NA blocks: patients who receive a lumbar plexus block or psoas compartment block while on enoxaparin are at risk for significant blood loss and retroperitoneal hematoma; ASRA recommended following the same guidelines as those for NA blocks when performing peri-NA or deep plexus blocks in patients taking anticoagulant medications; direct injury to a nerve is not discussed in the guidelines

Timing issues: include the start time for the waiting period before performing the block or removing the catheter, and how long to wait before resumption of anticoagulation after the block or after catheter removal; the speaker recommends once-daily dosing for patients with indwelling catheters

Conclusion: despite following ASRA guidelines, some incidence of NA hematoma or injury is inevitable; individualization of care planning and clinical judgment are crucial; use of >1 anticoagulant agent creates additive risk; risk may be reduced by use of smaller needles with fewer passes and less technically difficult procedures; nerve injury secondary to a hematoma typically present with sensorimotor block as the primary symptom, as opposed to pain; in cases of, eg, traumatic event in a high-risk patient, consider use of an opioid-only infusion instead of local anesthetic; it is important to heed patient reports of symptoms and intervene early

Readings

Bos EME, Posner KL, Domino KB, et al. Haematoma, abscess or meningitis after neuraxial anaesthesia in the USA and the Netherlands: A closed claims analysis. Eur J Anaesthesiol. 2020; 37(9):743-751. doi:10.1097/EJA.0000000000001260; Cheney FW, Domino KB, Caplan RA, Posner KL. Nerve injury associated with anesthesia: a closed claims analysis. Anesthesiology. 1999 Apr;90(4):1062-9. doi: 10.1097/00000542-199904000-00020. PMID: 10201678; Henshaw DS, Turner JD, Forest DJ, et al. Residual enoxaparin activity, anti-Xa levels, and concerns about the American Society of Regional Anesthesia and Pain Medicine anticoagulation guidelines. Reg Anesth Pain Med. 2017; 42(4):432-436. doi:10.1097/AAP.0000000000000617; Horlocker T, Vandermeuelen, E, Kopp S, et al. Regional anesthesia in the patient receiving antithrombotic or thrombolytic therapy. American Society of Regional Anesthesia and Pain Medicine Evidence-Based Guidelines (Fourth Edition). Reg Anesth Pain Med. 2018; 43:263-309; Kietaibl S, Ferrandis R, Godier A, et al. Regional anaesthesia in patients on antithrombotic drugs: Joint ESAIC/ESRA guidelines. Eur J Anaesthesiol. 2022; 39(2):100-132. doi:10.1097/EJA.0000000000001600; Solari F, Varacallo M. Low molecular weight heparin (LMWH) [updated]. StatPearls Publishing. 2022 Jul 19. Available from: https://www.ncbi.nlm.nih.gov/books/NBK525957/; Tryba M. European practice guidelines: thromboembolism prophylaxis and regional anesthesia. Reg Anesth Pain Med. 1998; 23(6 Suppl 2):178-182. doi:10.1016/s1098-7339(98)90144-4.

Disclosures

For this program, the following relevant financial relationships were disclosed and mitigated to ensure that no commercial bias has been inserted into this content: Dr. Jaffe has been a consultant for Pacira BioSciences, Inc and Konica Minolta U.S.A. Members of the planning committee reported nothing relevant to disclose. Dr. Jaffe's lecture includes information related to the off-label or investigational use of a therapy, product, or device.

Acknowledgements

Dr. Jaffe was recorded at the 69th Annual Convention and Conclave of the American Osteopathic College of Anesthesiologists, held in Palm Beach, FL on September 28, 2021, and presented by the American Osteopathic College of Anesthesiologists. For information about upcoming CME activities from this presenter, please visit www.aocaonline.org. Audio Digest thanks the speakers and presenters for their cooperation in the production of this program.

CME/CE INFO

Accreditation:

The Audio- Digest Foundation is accredited by the Accreditation Council for Continuing Medical Education to provide continuing medical education for physicians.

The Audio- Digest Foundation designates this enduring material for a maximum of 1.00 AMA PRA Category 1 Credits™. Physicians should claim only the credit commensurate with the extent of their participation in the activity.

Audio Digest Foundation is accredited as a provider of continuing nursing education by the American Nurses Credentialing Center's (ANCC's) Commission on Accreditation. Audio Digest Foundation designates this activity for 1.00 CE contact hours.

Lecture ID:

AN643901

Expiration:

This CME course qualifies for AMA PRA Category 1 Credits™ for 3 years from the date of publication.

Instructions:

To earn CME/CE credit for this course, you must complete all the following components in the order recommended: (1) Review introductory course content, including Educational Objectives and Faculty/Planner Disclosures; (2) Listen to the audio program and review accompanying learning materials; (3) Complete posttest (only after completing Step 2) and earn a passing score of at least 80%. Taking the course Pretest and completing the Evaluation Survey are strongly recommended (but not mandatory) components of completing this CME/CE course.

Estimated time to complete this CME/CE course:

Approximately 2x the length of the recorded lecture to account for time spent studying accompanying learning materials and completing tests.