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Chapter 9 Anticoagulation
A 74-year-old female presents for a total hip replacement. She has a past medical history of atrial fibrillation, hypertension, moderate renal insufficiency (CrCl 46 ml/min), and osteoarthritis. She is currently taking rivaroxaban 15 mg daily, metoprolol 50 mg BID, and lisinopril 20 mg daily.
Objectives
1. Review the current recommendations for regional anesthesia in the setting of anticoagulation.
2. Discuss the patient characteristics that affect anticoagulant therapy.
3. Contrast the recommendations for superficial peripheral nerve block with those for neuraxial and deep blocks.
4. Explain the management of a patient who is anticoagulated and has an indwelling neuraxial catheter.
5. Describe the reversal of specific anticoagulants.
1. Review the current recommendations for regional anesthesia in the setting of anticoagulation
Spinal hematoma remains the most concerning and catastrophic adverse event that can occur in patients receiving neuraxial anesthesia. In an attempt to decrease the risk of spinal hematoma, the American Society of Regional Anesthesia and Pain Medicine (ASRA) has published three practice advisories pertaining to the use of regional anesthesia in the anticoagulated patient. A summary of the most recent ASRA guidelines (2010) is presented in Table 9.1 [1].
Summary of 2010 ASRA guidelines.
| Drug | Neuraxial anesthetic guidelines | Wait time for needle insertion after drug cessation | Wait time after needle or catheter removal |
|---|---|---|---|
| Thienopyridines derivatives | Actual risk unknown. | Suggest 7 days for clopidogrel and 14 days for ticlodipine. | Restart as soon as adequate hemostasis is achieved. |
| Warfarin | Initiation: Single dose >24 h ago or two doses given = check INR before proceeding (<1.5). Chronic use: Normal INR | Initiation: INR <1.5 or within 48 h. Monitor. Discontinuation: 5 days with a normal INR. | Can start warfarin at the same time as needle insertion or catheter removal. |
| Heparin | Safe with 5,000 U SQ BID. >10,000 U. Proceed but monitor for PTT. >4 days check platelet count. | 2–4 h. For IV or TID dosing, consider monitoring for 12 h. | Ideal to delay first dose after block. 1 h to heparinize for vascular procedures. |
| Low molecular weight heparin (i.e., enoxaparin, dalteparin, tinzaparin) | No evidence for routine checking of anti-Xa level. Female, elderly, renal impairment and concomitant anticoagulants are associated with increased risks of spinal hematoma. | Wait 12 h for low dose. Higher doses (bridging therapy, DVT treatment, postoperative prophylaxis): 24 h. | 24 h after bloody or difficult placement. BID dosing: 24 h first dose. Daily dosing: 8 h then 24 h after. Remove catheters >12 h after last dose but 4 h before next dose. |
| NSAIDs | Single agent: No added risk. | No interference. | No interference. |
| GpIIb/IIIa antagonists | Contraindicated within 4 weeks of surgery. Risk with neuraxial anesthesia unknown. | Abciximab: 24–48 h suggested. Eptifibatide and tirofiban: 4–8 h suggested. | Unclear. |
| Fibrinolytics/thrombolytics | Never “except highly unusual circumstances…” | Avoid given no data. Wait at least 10 days. | Avoid given no data. |
| Herbal medications | Garlic, ginkgo, and ginseng all increase bleeding but clinical studies are lacking. | No interference as single agent. | No interference as single agent. |
Since 2010, newer anticoagulants have gained widespread use for treatment and prevention of venous thromboembolism (VTE), atrial fibrillation (AF), and acute coronary syndrome(ACS). Despite the increased use of these novel anticoagulants, guidelines pertaining to regional anesthesia remain lacking. Consequently, the cessation and resumption of these agents in relation to neuraxial anesthetics and indwelling catheters are based largely on the evaluation of pharmacokinetic properties. In general, an elimination period of five half-lives, or 97% clearance of the drug, is considered an acceptable time lapse after drug cessation to allow for safe performance of neuraxial techniques without an increased bleeding risk [2]. Selective emerging novel oral agents, not presented in the ASRA guidelines, with implications for regional anesthesia are highlighted below [2–3]. The 4th edition of Regional Anesthesia in the patient receiving antithrombotic or thrombolytic therapy is expected to be published in 2015. Therefore one should refer to current published recommendations for up-to-date guidance.
Rivaroxaban (Xarelto®)
Mechanism: oral factor Xa inhibitor
Peak effect: 2.5 to 4 h
Half-life: 5 to 9 h (healthy) and 9 to 13 h (elderly)
Plasma concentration increased by 24% in patients weighing less than 50 kg
Clearance: 33% renal, 66% fecal/biliary + other metabolism
Five half-lives clearance:
Resumption of drug after indwelling catheter removal (based on two half-lives interval minus time to peak effect of drug) [2, 4]: 5.5 to 21.5 h
Monitoring (most sensitive): anti-factor Xa assay – not readily available or recommended
Reversal: prothrombin complexes (PCC)
Apixaban (Eliquis®)
Mechanism: oral factor Xa inhibitor
Peak effect: 1 to 2 h
Half-life: 15 h
Clearance: 25% renal, 75% fecal/biliary + other metabolism
Five half-lives clearance:
– 3 to 4 days with CrCl >50 ml/min
– 4 to 5 days with CrCl 15 to 50 ml/min
Resumption of drug after indwelling catheter removal: 7 to 23 h [2, 4]
Monitoring (most sensitive): anti-factor Xa assay – not readily available or recommended
Dabigatran (Pradaxa®)
Mechanism: oral direct thrombin inhibitor
Peak effect: 2 h
Half-life: 12 to 14 h (healthy), 14 to 17 h (elderly), and 28 h (end-stage renal disease [ESRD])
Clearance: 80% renal clearance, 20% fecal
Plasma concentration 50% higher in elderly vs. young
Low body weight could be a risk factor for bleeding
Five half-lives clearance:
Neuraxial blockade:
Current ASRA draft recommendations suggest a 5-day cessation prior to neuraxial instrumentation.
Manufacturer advises against use of drug with neuraxial blockade [5]
Considered contraindicated with indwelling epidural catheters per manufacturer
Resumption of drug after indwelling catheter removal: 6 to 22 h [2, 4]
– Monitoring: thrombin time
– Reversal: hemodialysis
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