Anesthesia for Ankylosing Spondylitis Undergoing Spine Instrumentation
Awake fiberoptic intubation is the safest and recommended approach for securing the airway in AS patients undergoing spine instrumentation, as it allows continuous neurological monitoring while achieving a definitive airway in the context of anticipated difficult intubation and high risk of cervical spine injury. 1
Preoperative Airway Assessment
The primary anesthetic challenge in AS patients is airway management due to:
- Fixed cervical spine deformity with decreased or absent mobility, often in a flexed position 2, 1
- Temporomandibular joint involvement limiting mouth opening 2
- Potential cricoarytenoid cartilage involvement causing upper airway compromise 2
- Extreme fragility of cervical vertebrae prone to fracture with hyperextension, risking spinal cord transection and quadriplegia 2, 1
Critical pitfall: Never attempt conventional laryngoscopy with neck extension in AS patients, as this can cause catastrophic cervical spine fracture and quadriplegia 2.
Recommended Anesthetic Technique
Primary Approach: Awake Fiberoptic Intubation
Awake fiberoptic intubation should be performed as the first-line technique for the following reasons:
- Maintains continuous neurological monitoring throughout intubation 1
- Avoids dangerous neck manipulation 2, 1
- Allows immediate assessment of neurological function before proceeding 1
- Provides definitive airway control in patients with severe cervical deformity 2
Intraoperative Neurophysiological Monitoring
Multimodal neurophysiological monitoring (somatosensory and motor evoked potentials) is strongly recommended during spine instrumentation surgery in AS patients due to their high risk for neurological deterioration 3, 1.
Alternative: Regional Anesthesia Considerations
While regional anesthesia may be considered for lower extremity procedures, it is NOT recommended for spine instrumentation surgery for several reasons:
- Spinal anesthesia has a 23.8% failure rate in AS patients due to spinal ossification and ankylosis 4
- Epidural anesthesia has even higher failure rates (100% in one series) 4
- Neuraxial techniques do not address the airway management challenges 4
- Spine instrumentation requires prone positioning and prolonged surgery, making general anesthesia necessary 3
One case report documented epidural failure in AS necessitating conversion to general anesthesia, highlighting the unreliability of neuraxial techniques 5, 2.
Preoperative Medical Optimization
Disease-Modifying Drug Management
Anti-TNF agents and other DMARDs should be interrupted preoperatively according to their specific half-lives to reduce infection risk 3. However, the exact timing is not specified in the guidelines and should account for:
- Increased wound infection risk with anti-TNF therapy 1
- Need to balance infection risk against disease flare 3
NSAIDs Perioperatively
NSAIDs do not need to be discontinued for surgery 5. The ASAS/EULAR guidelines specifically state that NSAID administration on the evening before surgery does not affect perioperative bleeding or complication rates 5.
Additional Preoperative Assessment
Mandatory preoperative evaluations include:
- Bone quality assessment when feasible, as AS patients have increased fracture risk 3
- Cardiac assessment for conduction abnormalities and aortic regurgitation common in AS 1
- Pulmonary function testing for restrictive lung disease from chest wall rigidity 3, 1
- Renal function given chronic NSAID use 3
Postoperative Management
Enhanced recovery protocols should include:
- Early oral intake to minimize complications 3
- Early mobilization when surgically appropriate 3
- Aggressive multimodal pain control to facilitate early mobilization 3
Summary Algorithm
- Preoperative: Assess airway difficulty, optimize medical comorbidities, interrupt DMARDs appropriately, continue NSAIDs 3, 1
- Induction: Awake fiberoptic intubation as primary technique 2, 1
- Intraoperative: Multimodal neurophysiological monitoring throughout 3, 1
- Postoperative: Enhanced recovery with early mobilization and aggressive pain control 3