Scoliosis surgery
Stem
A 14-year-old girl, 52 kg, with adolescent idiopathic scoliosis and a 62° right thoracic curve is scheduled for a T4 to L1 posterior spinal fusion with pedicle screws. She is otherwise healthy, plays soccer without dyspnea, and her hemoglobin is 13.2 g/dL. The surgeon plans somatosensory and motor evoked potential monitoring and expects 4 to 5 hours in the prone position.
Question
What is your anesthetic plan for this fusion?
Ideal answer
HeadlineCord, blood volume, eyes: TIVA for readable motor potentials, a blood-loss plan.
- Propofol 50–250 mcg/kg/min with remifentanil. Volatile at most half a MAC if at all, no nitrous oxide;1 one intubating relaxant dose, worn off for baselines; none during screws and correction.2
- Arterial line, two large IVs, cell salvage, two units crossmatched, for steady fusion bleeding; tranexamic acid 20 mg/kg over 20 minutes, about 1 g, then 10 mg/kg/h.2
- MAP 60–65 in exposure, above 70 before correction, for cord perfusion.2
- Prone, head neutral, at or above the heart. Padded frame, globes free and checked;3 kept warm.
- Methadone 0.1–0.2 mg/kg at induction, about 5 to 10 mg, or surgeon-given intrathecal morphine, plus acetaminophen and low-dose ketamine infusion.2
Watch for: Signals, MAP, blood loss, hematocrit, temperature together: signal changes are often physiological.
Breaking down the answer
- Lead with the cord — the catastrophic complication is paraplegia; naming it first shows judgment and sets the order of everything else.
- Monitoring dictates the anesthetic — total intravenous anesthesia because volatile agents, nitrous oxide and relaxants depress motor signals; dexmedetomidine can as well, while ketamine can enhance them.2 A steady level matters as much as the choice: no boluses at critical moments.
- Antifibrinolytic — tranexamic acid reduces blood loss in fusion; regimens vary between institutions, so I name mine.2,1
- Blood pressure follows the surgery — permissive during exposure, higher before rods go in, because correction stretches the cord.2,1 Changes if: the center skips deliberate hypotension and holds a higher MAP throughout; I agree the target with the surgeon and neurophysiologist.
- Vision loss — long prone cases with large blood loss are the high-risk setting; head position and eye checks are the modifiable factors, and high-risk patients are told beforehand.3
- Lung function by curve size — restrictive defects become measurable around 70° and symptomatic near 110°; at 62° and running, she needs no PFTs.1 Changes if: neuromuscular scoliosis, with weak respiratory muscles and more postoperative ventilation.
Follow-up question
During rod rotation, the neurophysiologist reports that lower-extremity motor evoked potentials have fallen by more than 80% bilaterally; upper-extremity signals are unchanged. MAP is 64 and hemoglobin 8.9. What do you do?
Follow-up answer
HeadlineA significant alert: bilateral leg motor loss over 80% with unchanged arms points to the cord, not anesthesia.1 I tell the room and stop correcting.
I confirm no relaxant or volatile was given and check the leads. Then cord perfusion: MAP above 80 or 20% over baseline with phenylephrine, hematocrit above 30 with blood, temperature above 36.5 °C.1 I ask the surgeon to release the correction. If signals do not return, we do a wake-up test, which takes 20 to 30 minutes; some teams give methylprednisolone 30 mg/kg, benefit unproven.2 I reassess with repeat signals and a neurologic exam on emergence.
Pitfalls that cost points
- Running 1 MAC of sevoflurane and blaming the monitoring when signals fade.
- Treating a signal loss as technical before raising the blood pressure.
Rapid-fire
Q: When is fusion recommended? A: Usually for curves greater than 40°.2
Q: What are the SSEP alert criteria? A: Amplitude down more than 50% or latency up more than 10%.1
Q: Naloxone for a wake-up test? A: 1 mcg/kg every 5 minutes if she is slow to wake.2
Q: What does direct pressure on the globe cause? A: Retinal artery occlusion, which is why I check the eyes periodically once she is prone.3
Q: Who goes to the PICU? A: Signal changes, loss above a third of blood volume, neuromuscular scoliosis or ventilation needs.1
Numbers to know
| Item | Value |
|---|---|
| Propofol (TIVA) | 50–250 mcg/kg/min with remifentanil2 |
| Tranexamic acid (SPA) | 20 mg/kg over 20 min (max 2 g), then 10 mg/kg/h2 |
| Volatile limit | ≤0.5 MAC2 |
| MAP | 60–65 exposure; >70 before correction2 |
| Rescue after alert | MAP >80 or +20%, Hct >30, temp >36.5 °C1 |
| Methadone | 0.1–0.2 mg/kg2 |
| Intrathecal morphine | 3–5 mcg/kg2 |
Links
- Neuromonitoring: SSEPs, MEPs and anesthetic choice, Postoperative visual loss and prone positioning, Massive hemorrhage and transfusion, Peripheral nerve injury and positioning, Muscular dystrophies and myotonias
- SPA Case Guide: Posterior Spinal Fusion for AIS (2025); ASA Practice Advisory for Perioperative Visual Loss Associated with Spine Surgery (2019)
Sources
- 1.Pediatric Posterior and Anterior Spinal Fusion · UCSF Department of Anesthesia · anesthesia.ucsf.eduInstitutional guide; its TXA regimen (10 mg/kg load, 1 mg/kg/h) is lower than the SPA guide's.
- 2.Posterior Spinal Fusion for Adolescent Idiopathic Scoliosis (SPA Case Guide) · Society for Pediatric Anesthesia, 2025 · pedsanesthesia.org
- 3.Practice Advisory for Perioperative Visual Loss Associated with Spine Surgery 2019 (summary) · ASA (via Guideline Central), 2019 · guidelinecentral.com
Facts on this page were checked against these sources on Oct 15, 2026. Guidelines change; confirm doses against current institutional protocols.