Anesthesia for Spine Surgery

Nicole Weiss, MDMarch 23, 2012

Concerns for Spinal Surgery?

Neuromonitoring &/or Wake-Up TestSignificant Blood Loss Requiring TransfusionPostoperative Vision LossSpinal Trauma- Cervical Spine Injury & Spinal ShockPostoperative Airway CompromiseVenous Air EmbolismPreserving Spinal Cord PerfusionBronchial Blocker to Assist in Anterior & Lateral Thoracic Procedures

Case OneA 16 y/o female is undergoing instrumentation and fusion for scoliosis.

What anesthetic would you pick for this case & why?

In the middle of the case, motor evoked potentials are lost on the right side.

What is the next step?

Pick the number of hours of spinal cord ischemia that is associated with virtually no

recovery of neurologic function

1.One Hour2.Two Hours3.Three Hours4.Four Hours

Which of the following regimens will provide for

the fastest wake-up?1.Propofol & Remifentanil

2.Propofol & Sufentanil

3.Desflurane & Sufentanil

4.Desflurane & Remifentanil

Loss of Motor FunctionEtiology of the loss of motor function during surgery

Trauma, Ischemia, Hematoma, Compression

After three hours of critical ischemia there is usually no neurologic recovery

When patients awaken paraplegic there is little chance of full neurologic recovery

Prevention: Neuromonitoring & The Wake-Up Test

The Ideal RegimenPreserves SSEPs & MEPs while maintaining an adequate depth of anesthesia

Allows for a quick wake-up to assess motor function

Ensures that the patient can be kept comfortable even during a wake-up test

Intraoperative Wake-Up Test and Postoperative Emergence in Patients Undergoing Spinal Surgery: A Comparison of

Intravenous and Inhaled Anesthetic Techniques Using

Short-Acting AnestheticsRCT published in 2004 Anesthesia & Analgesia54 patients assigned to one of the following regimens:

Propofol & Remifentanil Propofol & Sufentanil Desflurane & Remifentanil

Intraoperative Wake Up Test

Steps for a Wake-Up/Stagnara Test

Discontinue all anestheticsReverse neuromuscular blockadeIf spontaneous respirations don’t occur, administer naloxone (in low increments)Stabilize head to prevent extubationEnsure upper extremity movement prior to lower extremity movementBe ready to re-anesthetize

Case Two52 y/o female with h/o of chronic low back pain admitted for a transpedicular osteotomy with a posterior approach, T12-L4. Baseline Hgb/Hct of 10/30.

Initial Concerns?

Transfusion RequirementsThree Factors Predict Need for Transfusion

Age Greater than Fifty Preoperative Hemoglobin Less than Twelve Transpedicular Osteotomy

Ways to Decrease Intraoperative Blood Loss Induced Hypotension Operative Tables (Jackson & Wilson Frame) Antifibrinolytic Activated Factor VII Cell Salvage Hemodilution

Which of the following antifibrinolytics has been shown to be the most effective in reducing blood loss?

1.Tranexamic Acid2.Aminocaproic Acid3.Aprotinin

AntifibrinolyticsAprotinin

Studies consistently show that it decreases blood loss Withdrawn from the market after studies revealed a

potential increase in mortality, perioperative renal failure, myocardial infarction and cerebral vascular accident after use

Study may have weaknesses

Tranexamic Acid & Aminocaproic Acid Studies Inconclusive

Case Three55 y/o male admitted for a lumbar spine surgery with a posterior approach. PMH is significant for peripheral vascular disease, diabetes and a prior TIA. The surgeon notes that the surgery will likely take ten hours and have an EBL of 2-3Liters.

Besides the likely need for transfusion, what is your first concern?

True or False?

Deliberate hypotension is associated withperioperative vision loss ?

1. True2. False

In spinal surgeries, the most common cause of

postoperative vision loss is…

1.Cortical blindness2.Posterior Ischemic Optic Neuropathy3.Acute Angle Glaucoma4.Anterior Ischemic Optic Neuropathy5.Retinal Vascular Occlusion6.Expansion of a vitrectomy bubble

Post Operative Vision Loss

Proposed Risk Factors of PIONPatient Factors

Male Diabetes Peripheral Vascular Disease

Operative Factors Prolonged Duration in Prone Position Large EBL Anemia Venous Congestion of Head Hypotension Prolonged Use of Vasopressors Type and Amount of Fluid Replacement Blood Transfusion

External Pressure?

ASA Practice Advisory for Perioperative Visual Loss Associated with Spine SurgeryThere is a subset of patients who undergo spine procedures while they are positioned prone and receiving general anesthesia that has an increased risk for the development of perioperative visual loss. This subset includes patients who are anticipated preoperatively to undergo procedures that are prolonged, have substantial blood loss, or both (high risk patients)Consider informing high-risk patients that there is a small, unpredictable risk of perioperative visual loss.The use of deliberate hypotensive techniques during spine surgery has not been shown to be associated with the development of perioperative visual loss.Colloids should be given along with crystalloids to maintain intravascular volume in patients who have substantial blood loss.At this time, there is no apparent transfusion threshold that would eliminate the risk of perioperative visual loss related to anemiaHigh risk patients should be positioned so that their heads are level with or higher than the heart when possible. In addition their heads should be maintained in a neutral forward position when possible.Consideration should be given to the use of staged spine procedures in high risk patients.

Case FourA 27 y/o male s/p MVA is brought to the operating room for an emergent decompression for traumatic cervical spinal cord injury.

What is your initial concern?? Securing the Airway

True or False?A patient with a recognized, unstable cervical spine injury has an increased risk for neurologic injury following intubation.

1.True2.False

What is the best technique for securing the airway in an

extremely unstable cervical spine?

1.Awake Fiberoptic2.Direct Laryngoscopy 3.Fast Track LMA4.Glidescope

Thoughts??

What FiO2 has been associated with a higher risk of surgical site infection in spine surgery?

1. no association2. < 30%3. < 50%4. < 70 %5 .< 90%

During the case the surgeon asks you to modify your inspired gas concentrations to decrease the risk of a surgical site infection.

Securing the Airway Maintain neutral neck position

Greatest movement in the atlanto-occipital junction and the junction of the first two cervical vertebrae

If the patient has a recognized unstable cervical spine, intubation is not associated with an increased risk of neurologic deterioration

Superior Technique for Intubation? Awake Fiberoptic, Direct Laryngoscopy, Glidescope, Fast Track

LMA All techniques are acceptable in experienced hands

Case Control StudyJohns Hopkins, 2009104 patients with surgical site infections compared to 104 random patients without surgical site infectionsCompared multiple factors, including an FiO2>50FiO2 is a MODIFIABLE risk factor02 vital to oxidative leukocyte processes

CASE SIXA patient is brought to the OR for an aortic dissection. The patient is on dabagatran. How should you reverse the anticoagulation? 1.Administer FFP2.Administer Platelets3.Administer Cryoprecipitate4.Dialyze the patient5.Administer protamine

Dabigatran is a….1. Direct Thromin Inhibitor2. GIIb/IIIa Inhibitor3. Platelet Aggregation Inhibitor4. Fibrinolytic Agent

How long after the last dose of dabagatran should you wait before placing an epidural?

1.8 hours2.10 hours3.24 hours4.34 hours5.72 hours

Pradaxa (dabigatran)Direct Thrombin InhibitorAlternative to warfarin for prevention of stroke, DVT80% renally excreted unchanged Administered PODoes not require INR monitoringPTT is prolonged, but it is not linear and does not correlate to the level of anticoagulationEcarin clotting time most accurate

Dabigatran & the Emergent Surgical Pt

Currently no way to fully reverse the anticoagulation

A monoclonal antibody is being developed

For active bleeding Hemostasis Transfuse as needed Maintain diuresis (renally cleared) Dialyze (62% can be cleared in 2 hours) Factor VII?

One recent case report suggests a high dose of 7.2mg/kg may have helped reverse

General SurgeryHalf life 8 hours in a healthy patientHalf life up to 17 hours in patients with renal failure

Dabigatran should be stopped 1-5 days prior to surgery

Bleeding risk & type of surgery Renal function of the patient

Regional AnesthesiaNeuraxial Techniques & Direct Thrombin Inhibitors (2010 ASRA Practice Advisory)

ASRA: Insufficient evidence. Suggest avoidance of neuraxial techniques.

German Society for Anaesthesia & Belgian Association for Regional Anesthesia:

Needle placement 8-10 hours after last dose. Delay subsequent doses 2-4 hours after needle placement

American College of Chest Physicians: No Recommendations

“Although there have been no reported spinal hematomas, the lack of information regarding the specifics of block performance and the prolonged half-life warrants a cautious approach.”

Questions??

ReferencesBaldus, C. Can We Safely Reduce Blood Loss During Lumbar Pedicle Subtraction Osteotomy Procedures Using Tranexamic Acid or Aprotinin. Spine. 2010; 35: 235-239.Barash, P. Clinical Anesthesia, 6th ed. 2009.Bitar, W. Critical ischemia time in a model of spinal cord section. A study performed on dogs. European Spine J. 2007;16:563-572.Black, Susan. Perioperative Manaement of Patients Undergoing Spine Surgery. Anesthesiology 2011. Farrokhi, M, et al. Efficacy of Prophylactic Low Dose of Tranexamic Acid in Spinal Fixation Surgery: A Randomized Clinical Trial. J. of Neurosurgical Anesthesiology .2011;23:290-296.Grottke, O, et al. Intraoperative Wake-Up Test and Postoperative Emergence in Patients Ungergoing Spinal Surgery: A Comparison of Intravenous and Inhaled Anesthetic Techniques Using Short-Acting Anesthetics. Anesthesia & Analgesia. 204;99:1521-7.Jaffe, R. Anesthesiologist’s Manual of Surgical Procedures, 4th ed. Lipincott Williams & Wilkins, 2009.Roth, S. Perioperative visual loss: what do we know, what can we do? British Journal of Anesthesia. 2009. 109; 31-40.