Transcript Spinal Cord Stimulator and Anticoagulation

Spinal Cord Stimulator
and Warfarin
Humphrey Lam MD
Vanderbilt University Medical Center
Department of Anesthesiology, CA-2
Case Presentation
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76 y/o female with a history of atrial fibrillation on warfarin, lumbar degenerative disc
disease, s/p lumbar laminectomies of L2-S1 back in 2007. She presented at that time
with lower back pain, bilateral foot numbness, as well as left leg pain. The back pain
had subsided since her surgery, and the left leg pain was milder, but the foot numbness
never truly went away. She then noted an increase in lower back pain and had an acute
episode of bilateral lower extremity numbness from the knees down. The sensation
slowly returned, but has intermittent relapses of the same symptoms. A MRI was
obtained that showed multilevel disease most severe at L5-S1 with decreased signal
noted in the left neural foramina; contrast enhancement encasing the L5 nerve root,
likely indicating scar formation.
Lower back pain is 5/10 on the pain scale, 7/10 on worse days. She is able to walk 2-3
miles a day, or for at least 45 minutes.
Interventions thus far- ESI x2 prior to surgery, left L5 TF Epidural Injection, RACZ
Caudal Epidural Adhesiolysis
What’s next? The patient will have a spinal cord stimulator trial. If she demonstrates
a good response, then she may benefit from a long-term implant.
Spinal Cord Stimulator
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Neurostimulation sprung from the pioneering work on SCS for the treatment
of pain at the University Hospitals of Cleveland in the 1960s by Dr. Norman
Shealy
Used to treat pain from failed back surgery, radicular pain, complex regional
pain syndrome, vascular insufficiency, peripheral neuropathy, headache,
angina, abdominal pain, and pelvic pain.
Spinal Cord Stimulation Complications in Order of Decreasing Frequency
 COMPLICATIONREPORTED FREQUENCY (BY REFERENCE)
 Lead migration with need for revision 7%,[18] 10%,[19] 5%,[20] 14%,[21] 11%[22]
 Lead breakage with need for revision 13%,[18] 23%,[19] 0%,[20] 13%,[21] 6%[22]
 Infection 4%,[19] 7%,[20] 3%,[21] 5%[22]
 Neurologic injury Case reports, rare [24,25]
Atrial Fibrillation
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Found in 1 % of persons > 60 years to more than 5 percent of patients > 69 years.
lifetime risk of developing atrial fibrillation after age 40 has been found to be 26.0 percent for
men and 23.0 percent.
4 things to consider are treatable contributing factors, control of the ventricular rate, prevention
of recurrences, and prevention of thromboembolic episodes
risk of systemic emboli as a result of circulatory stasis
risk of stroke in patients with nonvalvular atrial fibrillation is five to seven times greater than that
in controls without atrial fibrillation
Risk factors that predict stroke in patients with nonvalvular atrial fibrillation include- previous
stroke or transient ischemic attack (relative risk, 2.5), diabetes (relative risk, 1.7), history of
hypertension (relative risk, 1.6), and increasing age (relative risk, 1.4 for each decade). Patients
with any of these risk factors have an annual stroke risk of at least 4 percent if untreated.
< 60 years of age without any clinical risk factors or structural heart disease do not require
antithrombotic therapy for stroke prevention because of their low risk.
stroke rate is < 2 percent/year in patients between the ages of 60 and 75 years with lone atrial
fibrillation. These patients may be adequately protected from stroke by aspirin therapy.
>75 years patients with atrial fibrillation, anticoagulation should be used with caution and
carefully monitored because of the potentially increased risk of intracranial hemorrhage
Warfarin
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Oral anticoagulant that acts on vitamin K dependent
clotting factors (II, VII, IX, X)
Activity level of 40% for each factor is adequate for
normal or near normal hemostasis (INR < 1.5)
PT and INR are most sensitive to factors VII and X
INR >1.2 occurs when factor VII activity is reduced to
55% of baseline
Age, diet, race, drug interactions, sex, body weight, and
comorbidities
ASRA Guidelines
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Warfarin must be stopped 4-5 days prior to the procedure
PT/INR should be measured prior to the neuraxial procedure
Concurrent use of meds that affect the clotting cascade should
be checked
Patients on low-dose warfarin therapy during epidural analgesia
should have their PT/INR monitored daily
Neuraxial catheters should be removed when the INR is <1.5
Neurological testing should be performed routinely on patients
on warfarin therapy
Reduce or withhold warfarin dose in patients with indwelling
catheters with an INR >3
References
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Horlocker, Terese T. et al. Regional Anesthesia in the Anitcoagulated Patient:
Defining the Risks (The Second ASRA Consensus Conference on Neuraxial
Anesthesia and Anticoagulation). Regional Anesthesia and Pain Medicine
2003, 28: 172-197
Braunwald's Heart Disease: A Textbook of Cardiovascular Medicine, Peter
Libby et al. 8th ed.
Raj's practical management of pain/editors, Honorio T. Benzon…[et al.]. 4th
ed.
Shah, RV and Kaye AD. Bleeding risk and interventional pain management.
Current Opinion in Anesthesiology 2008, 21:433-438
Woods DM et al. Complications of neurostimulation. Techniques in
Regional Anesthesia and Pain Management 2007, 11:178-182