What is the Gold Standard for Anticoagulants in Spine Surgery?

Gilbert Kim
Henry Ahn, M.D., FRCSC
University of Toronto Spine Programme, St. Michael's Hospital
Toronto, ON

Spinal operations vary tremendously in terms of complexity, length of time under anesthetic, levels decompressed and fused, and surgical approach (anterior/posterior/combined approaches) depending on the pathology being treated. Because of the diverse range of spinal operations and pathology that is treated, there is no single gold standard2.

However, there are evidence-based guidelines for spinal cord injured patients, representing a potential "gold standard", but only applicable to this highest risk subgroup where up to 81% of patients can develop DVTs if not treated6. Guidelines recommend pharmacological anticoagulant prophylaxis for spinal cord injured patients with low-molecular-weight heparin (LMWH) for three months7. Other patient groups have no such similar evidence-based guidelines2.

The lack of a gold standard for patients without a spinal cord injury is due to several factors. The incidence of deep venous thrombosis and pulmonary embolism in this group is not known and varies depending on the study from 0% to 15.5%8. Many of these patients are asymptomatic. Data is also predominantly based on level III studies rather than level I randomized control trials1. Incidence rates can vary depending on how the DVT is diagnosed: with some studies screening with ultrasonography or venography and others utilizing only clinical criteria. Patients also vary tremendously. Risks of DVT and PE for patients having microdiscectomy are negligible whereas an elderly patient with underlying comorbidities may have a significantly elevated risk from undergoing a decompression/fusion for myelopathy or neurogenic claudication.

Given that there is no single gold standard, there are a number of different treatment options. These include the use of thromboembolic stockings or intermittent sequential pneumatic compression and/or low-molecular-weight heparin prophylaxis4,5. However, spine patients with neurologic injury are at potential risk of epidural hematomas from prophylactic anticoagulation. As a result, prophylactic anticoagulation should be reserved for patients who have risk factors for DVT/PE and can be combined with mechanical methods for prophylaxis2,8. The indications include: 1) combined anterior/posterior approaches, 2) prolonged bed rest including traction, 3) previous thromboembolic events, 4) cancer, 5) older age (>60), 6) obesity and 7) oral contraceptive use2,9. However, the increase in risk, given a risk factor or combination of risk factors for thromboembolic events, is not known. For patients without any risk factors, TEDS or pneumatic compression devices without anticoagulation maybe suitable1.

There are also no gold standards if a clinically significant DVT or PE occurs1,1,3,8. Therapeutic levels of intravenous heparin or low-molecular-weight heparin can lead to high rates of bleeding complications such as epidural hematomas and draining wound hematomas1,3. As a result, some centres advocate the use of inferior vena cava filters as an alternative to therapeutic anticoagulation if a thromboembolic event occurs in the first week after surgery followed by anticoagulation afterwards3.

There are no evidence-based guidelines for screening9. Venography is the most accurate, but it is invasive and not often used clinically. Screening is most commonly done with Doppler ultrasound within the first week after major spinal surgery4,5,9. DVTs detected by screening tests, situated below the knee, have significantly lower risks of pulmonary embolism9. Screening can be performed in patients with risk factors for thromboembolic events prior to discharge4,5,9. There is no evidence: 1) that screening is beneficial in reducing the incidence of pulmonary embolism, 2) when to screen, and 3) for whom screening should be performed.

In summary, there is a lack of level I and level II evidence which is required to develop "gold standards" or evidence-based guidelines for patients undergoing elective spinal surgery. More prospective high quality level research is needed with multiple centres to increase sample sizes to assess incidence rates and the treatment effects of thromboembolic prevention strategies.

References

  1. Barnes B., Alexander J.T., Branch C.L., Jr.: Postoperative Level 1 anticoagulation therapy and spinal surgery: practical guidelines for management. Neurosurg Focus 17:E5, 2004
  2. Brambilla S., Ruosi C., La Maida G.A., et al: Prevention of venous thromboembolism in spinal surgery. Eur Spine J 13:1-8, 2004
  3. Cain J.E., Jr., Major M.R., Lauerman W.C. et al: The morbidity of heparin therapy after development of pulmonary embolus in patients undergoing thoracolumbar or lumbar spinal fusion. Spine 20:1600-1603, 1995
  4. Ferree B.A., Stern P.J., Jolson R.S., et al: Deep venous thrombosis after spinal surgery. Spine 18:315-319, 1993
  5. Ferree B.A., Wright A.M.: Deep venous thrombosis following posterior lumbar spinal surgery. Spine 18:1079-1082, 1993
  6. Geerts W.H., Jay R.M., Code K.I., et al: A comparison of low-dose heparin with low-molecular-weight heparin as prophylaxis against venous thromboembolism after major trauma. N Engl J Med 335:701-707, 1996
  7. Geerts W.H., Pineo G.F., Heit J.A., et al: Prevention of venous thromboembolism: the Seventh ACCP Conference on Antithrombotic and Thrombolytic Therapy. Chest 126:338S-400S, 2004
  8. Schizas C., Neumayer F., Kosmopoulos V.: Incidence and management of pulmonary embolism following spinal surgery occurring while under chemical thromboprophylaxis. Eur Spine J 17:970-974, 2008
  9. West J.L., III, Anderson L.D.: Incidence of deep vein thrombosis in major adult spinal surgery. Spine 17:S254-S257, 1992

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