What is spinal shock, its clinical presentation, and the recommended acute management (including MAP targets and medication choices)?

Spinal Shock: Definition, Clinical Presentation, and Acute Management

Definition and Pathophysiology

Spinal shock is the temporary loss or depression of all spinal reflex activity, muscle tone, and autonomic function below the level of a spinal cord injury, occurring immediately after sudden cord transection or severe injury. 1, 2

• The condition results from sudden disruption of descending pathways that normally modulate spinal cord reflexes 2
• Duration varies significantly: typically resolves in 3-6 months but can persist for 1-2 years 3
• The end of spinal shock is marked by return of reflex activity, though debate exists whether this is signaled by bulbocavernosus reflex, deep tendon reflexes, or detrusor activity 4

Clinical Presentation

Neurological Features

• Complete loss of motor function below the injury level 1
• Absent or severely depressed deep tendon reflexes caudal to the lesion 2
• Loss of all sensory modalities below the injury 1
• Flaccid paralysis of skeletal muscles 1

Cardiovascular Manifestations (Neurogenic Shock)

• Hypotension with systolic blood pressure <90 mmHg or MAP <70 mmHg in injuries above T6 5
• Bradycardia (distinguishes neurogenic from septic shock, which presents with tachycardia) 5
• Loss of sympathetic tone causing distributive shock 6
• The incidence of neurogenic shock is approximately 29% in cervical SCI when appropriate hemodynamic and laboratory criteria are applied 6

Autonomic Dysfunction

• Loss of vasomotor control and temperature regulation 1
• Bladder areflexia requiring catheterization 3
• Gastrointestinal dysfunction 1
• Respiratory compromise in high cervical injuries 7

Acute Management Protocol

Hemodynamic Management: MAP Targets

Maintain MAP >85 mmHg for the first 5-7 days post-injury, though evidence supports a minimum threshold of MAP >70 mmHg as sufficient. 3, 8, 5

Evidence-Based Rationale:

• The American Association of Neurological Surgeons/Congress of Neurological Surgeons recommends MAP >85 mmHg for 5-7 days, though this is based on limited evidence from uncontrolled studies 3, 8
• French guidelines recommend the more conservative target of MAP >70 mmHg, noting insufficient evidence for higher targets 3, 8
• Spinal perfusion pressure >50 mmHg correlates with better 6-month neurological outcomes 3
• The correlation between MAP and neurological improvement is strongest in the first 2-3 days after admission 3, 8

Monitoring Requirements:

• Place an arterial catheter for continuous blood pressure monitoring - studies show MAP falls below target approximately 25% of the time without invasive monitoring 3, 8, 5
• Avoid all episodes of systolic blood pressure <90 mmHg until day 5-7 3
• Target systolic blood pressure >110 mmHg, as hypotension is an independent mortality factor 3, 5

Pharmacological Management

Vasopressor Therapy

• Use vasopressors to maintain MAP targets when fluid resuscitation is inadequate 5
• Titrate to maintain MAP ≥70 mmHg (or ≥85 mmHg per institutional protocol) 3, 8

Methylprednisolone: DO NOT USE

Steroids are NOT recommended for acute spinal cord injury and should be avoided. 3, 7, 5

• The Congress of Neurological Surgeons and American Association of Neurological Surgeons issued strong recommendations against methylprednisolone in 2013 7, 5
• NASCIS trials showed no lasting neurological benefit 3
• Significantly increased infectious complications: 7% infection rate with steroids vs 3% with placebo 3
• Higher rates of wound infections (3-times higher with high-dose MPSS) 3
• Propensity score analysis of large Canadian cohort found no benefit on one-year motor function but more pulmonary and urinary infections 3

Surgical Intervention

Perform emergency surgical decompression within 24 hours of neurological deficit to improve long-term neurological recovery. 3, 7

• Early surgery (<24 hours) associated with 8.9-fold increased relative risk of neurological recovery 3
• Reduces pulmonary complications including atelectasis and pneumonia 3
• Ultra-early surgery (<8 hours) may further reduce complications and increase recovery chances in stable patients 3

Transfer to Specialized Care

Transfer all patients with traumatic spinal cord injury (including those with transient neurological recovery) to a specialized spinal cord injury unit immediately. 3, 7, 5

• Specialized care reduces morbidity and long-term mortality (GRADE 2+ recommendation) 3, 5
• Only 20-50% of SCI patients arrive within the critical 24-hour window for optimal surgical intervention due to transfer delays 7

Urological Management

Remove indwelling catheters as soon as medically stable and initiate intermittent catheterization. 3

• Intermittent catheterization reduces long-term urinary tract infections, urolithiasis, and improves continence 3
• Begin once daily diuresis volume is adequate 3
• Use micturition calendar to optimize catheterization frequency 3

Risk Stratification Timing

Delay formal risk stratification and urodynamic studies until spinal shock resolves and neurological condition stabilizes. 3

• Spinal shock typically resolves in 3-6 months but may take up to 1-2 years 3
• Urodynamic testing during spinal shock provides unreliable data 3
• Patients at risk for autonomic dysreflexia (injuries at T6 or above) require hemodynamic monitoring during any urological procedures 3

Prevention of Secondary Complications

Pressure Ulcer Prevention

• Reposition every 2-4 hours with pressure zone checks 3
• Use high-level prevention supports (air-loss mattress, dynamic mattress) 3
• Visual and tactile checks of all at-risk areas daily 3
• Early mobilization once spine is stabilized 3

Rehabilitation

• Begin comprehensive rehabilitation from the first days of injury 7
• Stretching for at least 20 minutes per zone 3
• Immediate physical and occupational therapy enhances neurotrophic factors promoting axonal regeneration 7

Critical Pitfalls to Avoid

• Never use methylprednisolone - increases infections without neurological benefit 3, 5
• Never allow MAP to fall below 70 mmHg during the first week - associated with worse neurological outcomes 3, 5
• Never delay transfer to specialized centers - most patients miss the 24-hour surgical window 7
• Never perform risk stratification during active spinal shock - results are unreliable and should wait until resolution 3
• Never manage without arterial line monitoring - intermittent cuff pressures miss 25% of hypotensive episodes 3, 8