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Spine Surgery — Prone, Blood Loss, MEPs
TEXTSpecialty I · 10 min read
Prone positioning physiology + MEP-friendly TIVA + blood conservation. POVL prevention is the long-term sentinel.
After this lesson you can
3 min read9 sections- Plan prone positioning + POVL prevention.
- Manage blood loss + EBL goals.
- Use neuromonitoring (SSEP, MEP).
- Anticipate post-op pain management.
Prone positioning physiology
Increased airway pressure + atelectasis.
Reduced FRC.
Wilson frame or jelly rolls leave abdomen free less IVC compression.
Verify ETT depth after positioning (neck flexion advances tube).
Reposition if hemodynamic compromise persistent.
Watch for facial edema progressing throughout case.
POVL prevention
- long prone spine surgery
- blood loss
- hypotension
- anemia
- head neutral (Mayfield pins or face cradle, no direct globe pressure)
- head not below heart
- MAP within 20% baseline
- Hgb >9
- position checks every
30-60 min
Ischemic optic neuropathy most common mechanism.
TIVA for MEPs
Standard TIVA: propofol 75-150 mcg/kg/min + remifentanil 0.1-0.3 mcg/kg/min + low-dose ketamine 0.15 mg/kg bolus + 0.15 mg/kg/hr.
No maintenance NMB (need motor signal).
Single intubating dose of NMB acceptable — let wear off.
SSEPs more forgiving (tolerate 0.5-1 MAC volatile).
BAEPs most resistant.
Plan technique to specific monitoring needs.
MEP signal loss algorithm
- 1) notify surgeon (may need to release distraction/hardware)
- 2) raise MAP (vasopressor + volume) target ≥80-90
- 3) maintain Hgb >9-10 (transfuse if needed)
- 4) normalize PaCO₂
- 5) verify position
- 6) confirm anesthetic not over-deep
Recovery in 15-20 min reassures; persistent loss Stagnara wake-up test or termination.
Blood conservation
- pre-op iron + EPO for anemic patients
- TXA
30 mg/kgload + infusion (or single bolus) - cell saver
- controlled hypotension (carefully — MEP signal concerns)
- euvolemic hemodilution
- restrictive transfusion thresholds
Communication with surgeon on bleeding tolerance + transfusion threshold.
Posterior spine + scoliosis cases can have 30-50% EBV blood loss.
Opioid-sparing multimodal
Pre-op gabapentinoid + acetaminophen + NSAID (where surgeon comfortable).
- ketamine
0.15 mg/kgbolus +0.15 mg/kg/hr - dexmedetomidine
0.5 mcg/kg/hr - lidocaine
1.5 mg/kg/hr infusion
- ERECTOR SPINAE PLANE BLOCK at T5-T8 level (covers thoracic spine surgery)
- paravertebral block
- or intrathecal morphine
200-300 mcgby surgeon at end of case
Reduces opioid by 50%+ + faster mobilization + earlier discharge.
Pre-op imaging review + position planning
Pre-op neuro exam DOCUMENTED in detail before induction — provides baseline for any post-op deficit.
C-spine cases: discuss with surgeon about awake fiberoptic if instability, neuromonitoring needs, head-pin position.
- confirm Wilson frame vs Jackson table vs face cradle
- determine arm position (tucked vs extended on arm boards)
- confirm head positioning device + eye protection plan
Airway + IV access in the prone position
ETT secured both with tape AND a stay-suture or tongue blade against teeth wired in (cannot rely on tape alone — facial edema dislodges tape).
Verify ETT depth with chest auscultation pre + post turning.
Reinforced (wire-wound) ETT mandatory to prevent kink.
Two functional large-bore IVs IDEAL in arms positioned + accessible (either tucked with tubing run out, or extended on arm boards).
Arterial line strongly recommended for major spine cases (long, blood loss, MAP-critical for spinal perfusion).
Document everything before turning.
Pre-emergence + extubation planning
Major spine surgery: airway edema from prone position + facial edema from gravity + long duration consider DELAYED EXTUBATION if facial edema severe, with airway leak test (deflate cuff, listen for audible leak with PIP applied).
No leak = significant edema; consider keeping intubated overnight + extubating in ICU when edema resolves.
Post-op neuro exam protocol: if any motor deficit detected on emergence, immediately notify surgeon — possible hardware impingement on cord requires emergent return to OR.
Document neuro exam at handoff to PACU.
⚠ Common pitfalls
- Prone with eye pressure — POVL is devastating + permanent; use horseshoe headrest correctly.
- Hypotension with anemia in prone — multiplies POVL risk; maintain MAP + Hb.
- Volatile >0.5 MAC during MEP monitoring — suppresses signal.
- Aggressive crystalloid replacement — facial + airway edema before extubation.
💎 Clinical pearls
- TIVA preserves MEPs; sub-MAC volatile sometimes acceptable for SSEP-only cases.
- Antifibrinolytic TXA reduces blood loss in major spine — give 10-20 mg/kg load + 1-2 mg/kg/hr.
- MEP loss → raise MAP first, check positioning, then surgical team intervention.
- Pre-extubation cuff-leak test in long prone cases — extubate over a tube exchanger if edema.
Recap
- TIVA preserves MEPs; sub-MAC volatile sometimes acceptable for SSEP-only cases.
- Antifibrinolytic TXA reduces blood loss in major spine — give 10-20 mg/kg load + 1-2 mg/kg/hr.
- MEP loss → raise MAP first, check positioning, then surgical team intervention.
- Pre-extubation cuff-leak test in long prone cases — extubate over a tube exchanger if edema.
Mark each section done to complete the module.