What are the anesthetic considerations for a patient with a spinal cord injury at or above the T6 (thoracic 6) level?

Anesthetic Considerations for Spinal Cord Injury

For patients with spinal cord injury at or above T6, the primary anesthetic concern is preventing autonomic dysreflexia (AD), which is best achieved through neuraxial blockade (spinal or epidural anesthesia) to block afferent pathways, while carefully managing hemodynamic instability and respiratory compromise that are inherent to these injuries. 1

Critical Pathophysiology: Autonomic Dysreflexia

Autonomic dysreflexia is a life-threatening emergency occurring in patients with spinal cord injuries at or above T6, characterized by severe hypertension, reflexive bradycardia, headache, and sweating triggered by noxious stimuli below the injury level. 2, 3, 4, 5

• AD results from overstimulation of sympathetic reflex circuits in the upper thoracic spine when afferent pathways are intact below the injury but descending inhibitory control is lost 4
• The condition can be fatal if uncontrolled, with hypertensive crises potentially leading to stroke, myocardial infarction, or death 3, 5
• Common triggers include bladder distension, bowel manipulation, surgical stimulation, and any noxious stimulus below the injury level 3, 4

Airway Management Strategy

Remove the anterior portion of the cervical collar while maintaining manual in-line stabilization during intubation to optimize glottic exposure while minimizing cervical spine movement. 1, 6

Intubation Technique Selection

• Videolaryngoscopy with manual in-line stabilization is the preferred first-line approach for emergency intubation, as it reduces cervical spine movement compared to direct laryngoscopy 1, 6
• Use rapid sequence induction with direct laryngoscopy and a gum elastic bougie if videolaryngoscopy is unavailable or the operator lacks experience 1
• Fiberoptic intubation with spontaneous ventilation minimizes cervical spine movement most effectively but requires patient cooperation and is incompatible with emergency situations 1
• Avoid the Sellick maneuver during intubation as it may increase cervical spine movement 1

Muscle Relaxant Selection: Critical Timing

Succinylcholine can be safely used within 48 hours of acute spinal cord injury, but is absolutely contraindicated beyond this timeframe due to risk of life-threatening hyperkalemia from upregulated acetylcholine receptors. 1

• After 48 hours post-injury, denervation leads to proliferation of extrajunctional acetylcholine receptors throughout muscle membranes, causing massive potassium release with depolarizing agents 1
• Use rocuronium or other non-depolarizing agents for rapid sequence induction after the 48-hour window 1

Hemodynamic Management: Specific Targets

Maintain systolic blood pressure >110 mmHg during initial assessment and mean arterial pressure ≥70 mmHg continuously during the first week post-injury to prevent secondary neurological deterioration. 6

Cardiovascular Instability Patterns

• Injuries above T6 cause loss of sympathetic tone, resulting in neurogenic shock with hypotension and bradycardia 3, 4
• Paradoxically, these same patients are at risk for severe hypertension from autonomic dysreflexia when stimulated below the injury level 2, 3, 4
• Monitor for bradycardia during airway manipulation and surgical stimulation, which may require anticholinergic treatment 3, 4

Anesthetic Technique Selection Algorithm

For Surgery Below the Level of Injury

Neuraxial anesthesia (spinal or epidural) is the most effective technique for preventing autonomic dysreflexia by blocking afferent pathways that trigger the reflex. 2, 3

• Isobaric spinal anesthesia is particularly advantageous because it minimizes cephalad spread and allows more predictable control of block height in patients where sensory level cannot be assessed 2
• The level of neuraxial blockade is difficult to detect clinically in SCI patients, creating risk of excessively high blocks with hypotension when hyperbaric solutions are used 2
• Spinal anesthesia has proven safe, effective, and technically simple in this population, with one series of 13 patients showing zero incidence of AD despite 4 having prior AD history 2

General Anesthesia Considerations

If general anesthesia is chosen, maintain sufficient depth to suppress autonomic dysreflexia, but anticipate significant hypotension and respiratory dysfunction. 3, 7

• Deep general anesthesia with potent volatile agents can prevent or treat AD but carries similar hypotension risk as neuraxial techniques 2, 3
• Vasodilators like sodium nitroprusside may fail to control AD-induced hypertension 2
• General anesthesia is necessary for operations above the injury level or when neuraxial techniques are contraindicated 3, 7

For Complete Injuries: Special Consideration

Patients with complete low spinal cord injuries (below T6) undergoing surgery below their injury level may not require anesthesia if they have no history of autonomic dysreflexia or troublesome spasms, but an anesthesiologist must be present for monitoring. 3, 7

• This approach requires careful patient selection and continuous monitoring for unexpected cardiovascular or respiratory changes 3, 7
• Sedation with benzodiazepines may be sufficient for some procedures in this subset 7

Respiratory Management Protocol

Identify respiratory complications immediately as they are life-threatening in high cervical injuries, and implement a comprehensive ventilatory weaning bundle for cervical injuries. 1, 6

Ventilatory Weaning Bundle Components

• Apply an abdominal contention belt during spontaneous breathing periods to improve diaphragmatic function 1
• Provide active physiotherapy with mechanically-assisted insufflation/exsufflation devices for bronchial secretion clearance 1
• Administer aerosol therapy combining beta-2 mimetics and anticholinergics 1

Tracheostomy Timing

Perform early tracheostomy within 7 days for upper cervical injuries (C2-C5) when prolonged ventilatory support is anticipated; for lower cervical injuries (C6-C7), attempt extubation first and only perform tracheostomy after failed extubation attempts. 1, 6

• Early tracheostomy in high injuries combined with aggressive respiratory physiotherapy has been associated with better neurological recovery at 1 year 1
• Tetraplegic patients often tolerate supine positioning better than sitting due to gravitational effects on abdominal contents and inspiratory capacity 1

Critical Pitfalls to Avoid

Airway Management Errors

• Never leave the cervical collar fully in place during intubation—this worsens glottic visualization and increases failed intubation risk without providing additional spine protection 1, 6
• The actual risk of secondary spinal cord injury from airway management is extremely low (0.34% in 1,177 patients), so do not delay necessary airway interventions 1, 6

Hemodynamic Errors

• Failing to maintain systolic blood pressure >110 mmHg increases mortality risk in acute SCI 6
• Underestimating the severity of autonomic dysreflexia can lead to catastrophic hypertensive complications including stroke 3, 4, 5

Medication Errors

• Using succinylcholine beyond 48 hours post-injury risks fatal hyperkalemic cardiac arrest 1
• Topical anesthetics alone do not block stretch receptors and will not prevent autonomic dysreflexia 2

Neuraxial Technique Contraindications

• Regional anesthetic techniques are absolutely contraindicated in patients with clinically significant anticoagulation, thienopyridine antiplatelet therapy, or low-molecular-weight heparins due to catastrophic neuraxial hematoma risk 8

Multidisciplinary Preparation

Implement multidisciplinary planning and optimization of human factors before airway management, including team briefing, equipment preparation, and role assignment. 1, 6

• Early transport to Level 1 trauma centers within the first hours after trauma reduces morbidity and mortality and enables earlier surgical intervention 6
• Comprehensive pressure ulcer prevention must begin in the acute phase 6