Fortunately, the risk of spinal hematoma after epidural analgesia is low. However, the increasing use and variety of anticoagulants in the perioperative setting demand an understanding and appre- ciation of the risk versus benefit of neuraxial analgesia in antic- oagulated patients. In 2002, ASRA held its Second Consensus Conference on Neuraxial Anesthesia and Anticoagulation.31 This is the most recent peer-reviewed consensus identifying agents of concern and formalizing a practice guideline. Table 11–7 sum- marizes ASRA’s recommendations.
Warfarin
For patients on chronic oral anticoagulation (warfarin), the antico- agulant therapy must be stopped (ideally 4–5 days before the planned procedure) and the prothrombin time/International Normalized Ratio (PT/INR) measured before initiation of neuraxial block. ‘‘Caution’’ needs to be taken when performing neuraxial techniques in patients recently discontinued from chronic warfarin therapy. Practitioners do not have a unified recommendation for the optimal INR before placing a central neuraxial needle, but ideally close to normal should be safe.
For patients receiving both low-dose warfarin (<5 mg) and continuous epidural analgesia, it is advised to monitor PT/INR on a daily basis. Before removal of the catheter, a PT/INR should be checked if warfarin has been administered for more than 36 hours postoperatively. It is allowable to remove catheters when the INR is less than 1.5. The warfarin dose should be withheld or reduced for patients with epidurals in place and an INR greater than 3.0. It is also advised to monitor routine neurologic testing of sen- sory and motor function during epidural analgesia infusion.
The concurrent use of medications affecting other components of clotting mechanisms (aspirin, other nonsteroidal anti-inflammatory drugs [NSAIDs], ticlopidine, clopidogrel, unfractionated heparin, and low-molecular-weight heparin [LMWH]) may increase the risk of bleeding complications without influencing the PT/INR.
Subcutaneous Heparin
Patients receiving subcutaneous heparin thromboprophylaxis do not seem to be at increased risk for epidural analgesia. The practi- tioner must weigh the benefits of an epidural for postoperative analgesia, and if favorable, the consensus supports that action. In cases requiring intraoperative heparin anticoagulation (e.g., hep- arin bolus before placement of aortic cross-clamp), a delay of at least 1 hour after epidural placement is recommended.
LMWH
LMWH presents a distinct problem. There is not an accepted lab- oratory test to determine the extent of a patient’s anticoagulation while receiving LMWH. Monitoring of the anti-Xa level is not recommended because the anti-Xa level is not predictive of the risk of bleeding. For patients who receive perioperative LMWH, the practitioner needs to coordinate and communicate with the
Table 11^4.Recommended Dosing for Depodur
Type of Surgery Dose
Lower abdominal surgery 10–15 mg (1.0–1.5 ml) Elective cesarean section 10 mg (1 ml)
Pelvic surgery 10–15 mg (1.0–1.5 ml)
Lower extremity surgery 15 mg (1.5 ml)
Table 11^ 5.Common Side Effects of Epidural
Analgesia
Opioids Local Anesthetics
Nausea and vomiting Hypotension
Urinary retention Motor block
Pruritus Systemic toxicity
Respiratory depression Dysphoria
Sedation
Gastrointestinal dysfunction
surgical service to optimize the time interval between neuraxial needle placement and administration of LMWH. Antiplatelet or oral anticoagulant medications administered in combination with LMWH may increase the risk of spinal hematoma, and it is best to avoid combination therapy at this time. Education of the entire patient care team is necessary to avoid such drug combinations. An alert mechanism via pharmacy or nursing must be in place to inform the anesthesia provider when patients are receiving anticoagulation. On the day of surgery, traumatic needle or catheter placement may signify an increased risk of spinal hematoma but does not necessitate postponement of surgery. However, initiation of LMWH therapy should be delayed for 24 hours postoperatively.
Patients on preoperative LMWH should be assumed to have altered coagulation status. Placement should occur at least 10 to 12 hours after the last prophylactic LMWH dose and 24 hours after the last therapeu- tic dose. Neuraxial techniques should be avoided in patients who received LMWH 2 hours preoperatively (peak anticoagulant activity). Postoperative LMWH is a particular concern for practitioners administering continuous epidural analgesia. A twice-daily dosing regimen is associated with increased risk of bleeding. Therefore, in- dwelling catheters should be removed before initiating this LMWH thromboprophylaxis dosing regimen. Single daily dosing allows for safe maintenance of epidural catheters. Catheters should be removed a minimum of 10 to 12 hours after the last dose of LMWH. Subsequent LMWH dosing should be delayed a minimum of 2 hours after catheter removal.
Other Agents
Fondaparinux and other factor Xa inhibitors are potent agents and efficacious in DVT prophylaxis. Currently, there are little clinical data regarding risk of hematoma and neuraxial analgesia. Thus, it is recommended to avoid placement of central neuraxial needles and indwelling catheters in patients receiving these medications. Antiplatelet agents, such as the thienopyridine derivatives ticlo- pidine and clopidogrel, should be discontinued 14 and 7 days, respectively, before initiation of epidural analgesia. Glycoprotein IIb/IIIa inhibitors are contraindicated within 4 weeks of surgery. Epidural analgesia is contraindicated in patients receiving fibrinolyt- ic and thrombolytic therapy. Not enough information is available on thrombin inhibitors such as desirudin, lepirudin, and argatroban to make a proper risk assessment, and it is best to avoid neuraxi- al analgesia in patients receiving these medications. NSAIDs, cyclooxygenase-2 inhibitors, and herbal drugs used alone do not seem to increase risk of hematoma associated with epidural analgesia.
CONCLUSIONS
Epidural analgesia is a well-established modality for providing post- operative pain relief. Data from individual trials, meta-analysis, expert opinion, and personal application generally support improved outcomes by numerous measures. Not all studies show a clearly demonstrable benefit. This chapter provides supportive
Table 11^7.ASRA Guidelines for Regional Anesthesia in the Anticoagulated Patient
From American Society of Regional Anesthesia and Pain Medicine. Consensus Statements, Second Consensus Conference on Neuraxial Anesthesia and Anticoagulation.http://www.asra.com/consensus-statements/2.html(accessed 1/21/2007).
Table 11^6.Complications Related To Epidural Anesthesia and Analgesia
N Cardiac Arrest Respiratory Failure Seizures Peripheral Neuropathy Cauda Equina Syndrome Central Neurologic
Event Meningitis Death Epidural (nonobstetric) 5561 0 (0.0–0.5) 0 (0.0–0.5) 1 (1.8) (0.0–0.9) 0 (0.0–0.5) 0 (0.0–0.5) 0 (0.0–0.5) 1 (1.8) (0.0–9.0) 0 (0.0–0.5) Epidural (obstetric) 29732 0 (0.0–1.0) 3 (1.0) (0.0–2.7) 2 (0.7) (0.0–2.4) 0 (0.0–1.0) 0 (0.0–1.0) 0 (0.0–1.0) 0 (0.0–1.0) 0 (0.0–1.0)
Values expressed as N (N/10,000), (95% confidence interval [CI]).
Adapted from Auroy U, Benhamou D, Bargues L, et al. Major complications of regional anesthesia in France. Anesthesiology 2002;97:1274–1280.
83 III ACUTE PAIN
data for specific procedures and suggestions for a dosing scheme, highlights side effects, and reinforces the concerns of perioperative anticoagulation for thromboprophlaxis in patients with indwelling central neuraxial catheters.
R
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Chapter 12
CONTINUOUS
PERIPHERAL
NERVE
CATHETER
TECHNIQUES
Eric M. May and Martin L. DeRuyter
INTRODUCTION
Regional analgesia has been shown to be an effective therapy for postoperative analgesia in numerous clinical scenarios. Continuous
infusions of local anesthetic via perineural catheters not only capitalize on this technique but also extend the therapeutic window for several days. Patients have better outcomes, require less opioids, and can continue therapy at home in most situations. In this chapter, we describe various upper and lower extremity blocks and the placement of catheters for continuous infusions.