ASRA Guidelines for Neuraxial Anesthesia

Obstetrics/Anesthesia Combined Conference

Amy Powers Woods, M.D.Department of Anesthesiology, UTSW

August 25, 2010

To summarize anesthesia preop…• 38 yo G4P3 at 38 wks gestation– A1 Diabetes Mellitus– Previous C-section x3– Hx of partially occlusive femoral DVT in LLE• Was on Lovenox until 7/12/10• Changed to Heparin 10,000u SQ TID

– Last dose 7/29 at 1330

– Desires permanent sterilization– Physical exam unremarkable, VSS– Most recent labs 7/12/10 Hct 30.1

• Presented on 7/30/2010 for repeat C-section/BTL

Third Consensus Conference on Regional Anesthesia and Anticoagulation

As published in Regional Anesthesia and Pain Medicine, Vol 35, No 1, January-February 2010, pp 64-101

Strength and Grade of ASRA Recommendations

• Strength of Evidence– A: Randomized, clinical trials and meta-analyses– B: Observational and epidemiologic studies– C: Case reports and expert opinion

• Grade of Recommendation– 1: General agreement in efficacy– 2: Conflicting evidence or opinion on the usefulness– 3: General agreement that procedure is not useful

(and may be harmful)

Spinal Hematoma

• Definition: Symptomatic bleeding within the spinal neuraxis

• Actual incidence of spinal hematoma is unknown– Extensive literature search by M. Tryba (1993)• 13 cases after 850,000 epidural anesthetics (<1:150,000)• 7 cases after 650,000 spinal anesthetics (<1:220,000)

– Study was prior to routine thromboprophylaxis• Recent epidemiologic surveys suggest the risk is higher

Risk Factors for Spinal Hematoma• Literature review (1906 – 1994) by Vandermeulen et al– 61 cases of spinal hematoma associated with epidural

or spinal anesthesia (60% in most recent decade)

• 42 of 61 (68%) had evidence of hemostatic abnormality– 25 had heparin (UFH or LMWH), additional 5 PRESUMABLY had

heparin (vascular procedures, etc.)– 12 had evidence of coagulopathy, thrombocytopenia, or were

treated with antiplatelet medications, oral anticoagulants, thrombolytics, or dextran 70 immediately before or after neuraxial anesthetic

• 15 of 61 (25%) needle or catheter placement difficult• 15 of 61 (25%) needle or catheter placement bloody

– Overall, 53 of 61 (87%) either a clotting abnormality or needle placement difficulty was present.

Neurologic Outcome with Spinal Hematoma

• Vandermeulen’s literature review– Neurologic outcome reported

for 55 of 61 cases• Progression of sensory or motor

block (68%)• Bowel or bladder dysfunction

(8%)• NOT severe radicular back pain

– Spinal cord ischemia tended to be reversible in pts who underwent laminectomy within EIGHT hrs of onset of symptoms

Antithrombotic Therapy and Pregnancy

• Parturients 5 to 50x more likely to develop VTE than non-pregnant counterparts

• PE continues to be one of the most common causes of maternal death in U.S. and U.K.

• Risk factors for VTE in parturients include increasing age, prolonged immobilization, obesity, thrombophilia, previous VTE, and C-section

• The six-week period following delivery has an even higher rate of thrombosis and PE than pregnancy itself

Unfractionated IV and SQ Heparin• Heparin binds antithrombin (AT) and

accelerates its ability to inactivate thrombin (factor IIa), factor Xa, and factor IXa

• Larger molecular wt heparins will inhibit both IIa and Xa, while smaller wts only inhibit Xa

Unfractionated IV and SQ Heparin• Onset of action– IV – immediate onset of action– SQ – 1-2 hrs delayed **

• Half-life is 60-90 minutes• Anticoagulant effect– Both dose- and molecular size-dependent– Not linear, increases disproportionately with

increased doses– Monitored with aPTT (1.5-2x normal)– Reversed with protamine (1mg to every 100u)

Risk Factors for Spinal Hematoma in the Heparinized Patient

• Ruff and Dougherty (1981)– 342 pts who received therapeutic heparin after

lumbar puncture• 7 of 342 developed spinal hematomas• 3 risk factors identified

– Less than 60-minute time interval between administration of heparin and lumbar puncture

– Traumatic needle placement– Concomitant use of other anticoagulants (aspirin)

• Risk factors verified in subsequent reviews of case reports

Stafford-Smith M. Impaired haemostasis and regional anesthesia. Can J Anaesth. 1996; 43: R129-141.

Low-Molecular Weight Heparin (LMWH)

• Properties different from UFH– Inability to monitor

anticoagulant effect– Prolonged half-life (3-

4x UFH)– Incomplete reversal

with protamine– Prolonged therapy

associated with accumulation of anti-Xa activity

Neuraxial Anesthesia in the Patient Receiving LMWH

• Bergqvist et al (1992 & 1993)– European study– 19 articles involving 9013 pts who received LMWH

thromboprophylaxis and neuraxial anesthesia– ONE case of spinal hematoma was reported– Important note: European dosing is once daily

• May 1993: U.S.A. approved dosing regimen 30mg every 12 hours– Nearly 60 spinal hematomas were tallied by FDA from

1993 to 1998!

Risk Factors for Spinal Hematomas With LMWH Thromboprophylaxis

Fibrinolytic and Thrombolytic Therapy• Plasma half-life of

these meds is only hours, but thrombolytic effect may last days

• Max depression of fibrinogen and plasminogen at 5 hours

• Contraindication to thrombolytic therapy includes surgery OR puncture of non-compressible vessels within 10 days

Case Report

• An 84 yo man received an uncomplicated epidural steroid injection in the morning. He developed chest pain later that day, was admitted to the hospital, diagnosed with acute myocardial infarction, and treated with tissue plasminogen activator and heparin. He subsequently developed back pain and paraplegia. MRI demonstrated an epidural hematoma extending from T10 to the sacrum.

• Avoid thrombolytic drugs for at least 10 days after puncture of noncompressible vessels

• Avoid neuraxial anesthesia in pts with recent thrombolytic therapy (no clear timeline)

• Perform frequent neuro checks (no less than q 2hrs) when thrombolytic therapy is given unexpectedly to pt with recent neuraxial anesthesia

• Check a fibrinogen level prior to removal of indwelling catheter

Oral Anticoagulants (Warfarin)• Interferes with the synthesis of

vitamin K-dependent clotting factors (II, VII, IX, X)

• Clinical experience suggests 40% factor necessary for normal coagulation

• INR of 1.5 corresponds to 40% of Factor VII

• Warfarin should be stopped for 4-5 days AND the INR normalized (<1.5) prior to neuraxial anesthesia.

• PT/INR should be checked daily if warfarin and neuraxial catheter are used concurrently– PT/INR should be checked before catheter removal if

the last dose were within 36 hrs– Catheter removal may be attempted when INR is < 1.5

• If INR were >3, the next dose of warfarin may need to be withheld for an indwelling catheter

Antiplatelet Medications

Abciximab, eptifibatide, tirofiban

NSAIDs,

• NSAIDs (and aspirin) represent no significant added risk for the development of spinal hematoma.

• Avoid neuraxial techniques if NSAIDs are used concurrently with medications that affect clotting mechanisms.– COX-2 inhibitors have little effect on platelets.

• Do not perform neuraxial anesthesia within 14 days of ticlid therapy or 7 days of plavix therapy.

• Avoid neuraxial techniques until platelet function has returned in pts receiving GP IIb/IIIa inhibitors.

• Garlic– Reduces blood pressure, thrombus formation, and serum lipid

and cholesterol levels– Inhibits in vivo platelet aggregation is dose-dependent fashion– Time to normal hemostasis after discontinuation – 7 days

• Ginkgo– Cognitive disorders, peripheral vascular disease, vertigo, tinnitus,

and altitude sickness– Inhibits platelet activating factor– Time to normal hemostasis after discontinuation – 36 hrs

• Ginseng– Protects against effects of stress– May inhibit the coagulation cascade– Time to normal hemostasis after discontinuation – 24 hrs

• These represent no added risk for spinal hematoma

• Essentially, there is insufficient evidence to make risk assessments. It is best to avoid neuraxial techniques in this population.

Back to our case….• Lovenox converted to heparin at 35/36 wks EGA• Last heparin was given 7/29 at 1330 (>24 hrs prior to

case)• Combined Spinal-Epidural chosen– Uneventful, atraumatic placement– Injection on 7/30 at 1441

• C-section and Bilateral Tubal Ligation– Uneventful, normal EBL

• Epidural removed 7/30 at 1530• Heparin 5000u SQ q 12h restarted 8/1 at 1600• Converted to Lovenox 80mg q 12h on 8/2 at 1800, to be

continued for 6 wks postpartum

Obstetric Management per ASRA

• No later than 36 wks, switch to LMWH or UFH• At least 36 hrs before induction of labor or C-

section, convert LMWH to UFH.• Discontinue UFH 4-6 hrs before anticipated

delivery.• Postpartum, resumption of prophylaxis (5000u

UFH SQ BID) should not resume until 12 hrs after epidural removal for SVD, or 24 hrs post C-section.– If higher doses are required, prophylaxis should be

delayed for at least 24 hrs.

What to Remember• Heparin prophylactic BID dosing is not a

contraindication to neuraxial anesthesia• TID dosing may represent increased risk, so vigilance is

needed.• Try to avoid neuraxial techniques for more than 1-2

after heparin SQ, as this correlates to peak drug effect• LMWH not quite as simple

– Low dose: Wait 10-12 hrs after last dose. Restart no sooner than 2 hrs after needle placement. Indwelling catheters ok, just delay removal 10-12 hours after last dose and don’t restart until 2 hrs after cath removal.

– High dose, BID dose: Wait 24 hrs after last dose. Restart no sooner than 24 hrs postop. Indwelling catheters not as safe.

What to Remember

• Remember BID dosing of LMWH represents an increased risk of spinal hematoma with neuraxial anesthesia

• Convert to UFH at least 36 hrs prior to planned delivery

• Discontinue UFH 4-6 hrs prior to planned delivery

• Resume UFH 12 hrs post SVD, 24 hrs post C/S

Thanks! Any Questions?