Chronic Spinal Cord Injury

This topic appeared as an SAQ in September 2017; most of the marks were for knowing the pathophysiological organ system effects of spinal cord injury, with the benefits of RA and the use of suxamethonium making up the rest.

It reappeared as a CRQ in March 2023 (53% pass rate), where marks were lost on doses of induction agents and the safety of using suxamethonium.

Resources

Patients with chronic spinal cord injury have multiple comorbidities and complex pathophysiological changes associated with their injury
There has been an increase in survival in the first 2yrs post-injury, but long-term survival remains less than an age-matched population

ASIA score at 72hrs the most sensitive predictor of long - term prognosis
Leading causes of death are respiratory, cardiovascular (40%) and genitourinary issues

Respiratory

The degree of ventilatory dysfunction depends on the level and completeness of the lesion

Level	Effect
Above C3	Complete dependence on mechanical ventilation due to phrenic nerve denervation
C3 - C5	Variable dependence on mechanical ventilation due to diaphragmatic and accessory muscle impairment
C6 - 8	ntermittent NIV often required Diaphragmatic and accessory muscle function is adequate for inspiratory effort Intercostals and abdominal wall muscles are paralysed, impair forced exhalation and cough, increasing secretion retention and risk of LRTI
Thoracic	Intercostals and abdominal wall muscles are paralysed, impair forced exhalation and cough, increasing secretion retention and risk of LRTI

Lung mechanics

Increased VC when supine; greater displacement of abdominal contents due to abdominal wall paralysis
Reduced FVC and FEV₁ leads to restrictive lung defect
Reduced RV, TLC and FRC
There may be reduced chest wall and lung compliance in cervical injuries owing to intercostal muscle spasticity
Increased risk of OSA

Ventilatory support

20% require a tracheostomy owing to prolonged mechanical ventilation
Ventilatory support required for:

Respiratory muscle fatigue
Impaired secretion clearance
Respiratory complications e.g. pneumonia / atelectasis

Autonomic dysreflexia

A clinical emergency characterised by a massive, disordered autonomic response to certain stimuli below the level of the lesion
Stimuli include bladder (80%) distension, bowel distension, acute intra-abdominal pathology, UTI, pressure ulcers, sexual activity
There is a loss of regulation of sympathetic output by input from higher centres
There is compensatory parasympathetic activation down to the level of the lesion, resulting in bradycardia and vasodilation above the lesion

Symptoms	Signs
Headache	Severe hypertension (BP ↑≥20%)
Flushing	Myocardial ischaemia
Sweating	Arrhythmias
Nasal congestion	Raised ICP
Chills	Pulmonary oedema
Piloerection	Seizures
Pallor	Intracranial haematoma

The development of ADR is affected by:

Level of lesion

Incidence 50 - 70% in those with lesions above T6
Those with lesions above T6 have a greater severity of symptoms as there is involvement of the splanchnic circulation, which vasoconstricts during episodes

Completeness of injury

Higher frequency in complete injuries

Duration since the injury

Most commonly observed ≥1yr after injury but can be experienced sooner (especially with higher lesions)

Management of autonomic dysreflexia includes:

Exclusion of bladder or bowel distension
10mg SL nifedipine
20mg IV hydralazine slowly or 20mg diazoxide 2nd line
IV infusion of GTN, magnesium or phentolamine 3rd line

Cardiovascular

Pathology	Notes
Arrhythmias	Vagal hypersensitivity predisposes to bradyarrhythmias in the first 5 weeks after injury
Cardiovascular disease	↑ Risk due to lack of physical activity, esp. if ↑age and higher/complete lesions
Thermoregulation	Impaired due to ↓sensory input to higher centres, ↓ sympathetic control of vascular tone and ↓ sweating
VTE	High risk in first 3 months (85% in first 3 months without prophylaxis) Risk reduces thereafter but may increase in the peri-operative period
Anaemia	Reduced blood volume and anaemia (50%)
Postural hypotension	Due to reduced blood volume, lower limb pooling and altered baroreceptor reflex
IV access	Difficult due to atrophic, hyper-aesthetic skin and reduced cutaneous blood flow

Neurological

Extra - junctional nAChR; suxamethonium should be avoided after 24hrs until 6 months
Chronic pain (65%)

Nociceptive (MSK structures, viscera)
Neuropathic (spinal cord, nerve damage)

Depression ± drug addiction ± suicide

Renal

Neurogenic bladder

Impaired sensorimotor innervation of the bladder
Reduced bladder capacity | incomplete emptying | chronic retention
Detrusor-sphincter dyssynergia

Frequent UTIs - the most common cause of sepsis in spinal cord injury patients
Vesico-ureteric reflux and nephrolithiasis
Long term catheterisation / suprapubic catheter required

Gastrointestinal

Delayed gastric emptying
Constipation
Gastric or bowel distension
Abdominal pain
Rectal bleeding
Gallstones ± other biliary complications

Musculoskeletal

Spasticity

Can be provoked by minor stimuli
Typically treated with baclofen (GABA_B receptor agonist) ± benzodiazepines

Contractures
Osteoporosis

60% at 15yrs post - injury
A third of patients experience a fracture
Necessitates careful handling and positioning

Pressure ulcers

Due to a blend of unrelieved pressure, poor nutrition, muscle atrophy and altered dermal blood flow

Spinal fixation may be performed to obtain stability

May make airway management difficult
May preclude neuraxial anaesthesia

Perioperative management of the patient with chronic spinal cord injury undergoing surgery

Emergency presentations are often delayed in their diagnosis, owing to atypical presentations
Surgeries typically include general (e.g. for bowel obstruction, acute biliary issues, appendicitis) or orthopaedic (limb fractures, pressure sore debridement)

Elective surgeries include:

Urological: cystoscopy ± Botox injections for neurogenic bladder ± suprapubic catheter change
General: bowel defunctioning
Spinal: stabilisation of spinal injuries, IT baclofen pump insertion

History and examination

Level of injury
Completeness of injury
Time since injury
Presence of autonomic dysreflexia; known triggers, frequency of attacks
History of spasms/contractures
History of OSA/NIV, recent LRTI

Airway assessment

Review of previous anaesthetic charts
Note presence of tracheostomy and type/size etc.
Note previous C-spine issues
Note previous long-term ventilation or signs of tracheal stenosis

Investigations

Bloods

FBC: anaemia is common
U&E: renal impairment and electrolyte disturbances are common
±LFTs
ABG: if concerns regarding ventilation, especially if on long-term assisted ventilation

Swabs/cultures; many are MRSA colonised

Lung function tests/spirometry

Baseline vital capacity may indicate necessity for post-operative assisted ventilation

CXR if hypoventilation or active infection
MRI may be indicated if long - term ventilation and concern re: tracheal stenosis

ECG if concern re: IHD or dysrhythmia

Anaesthetist on standby

I.e. no immediate anaesthetic presence, may be appropriate if:

Surgery below the level of the lesion
Complete lesion
No autonomic dysreflexia
No muscle spasms

Neuraxial and regional anaesthesia

E.g. spinal, epidural, brachial plexus block
Benefits include:

Avoids intubation, which may be difficult if previous complications e.g. tracheostomy, tracheal stenosis
Reduces risk of aspiration, which may be high due to delayed gastric emptying
Avoids deteriorating lung function and post-operative pulmonary complications
Avoids autonomic dysreflexia
Avoids unopposed parasympathetic response to airway instrumentation, which can cause bradycardia and asystole
Reduced opioid use and associated respiratory depression

Difficulties include:

Challenging positioning due to contractures
Presence of bony deformities or spinal metal work
Checking block level and effectiveness

Unable to assess sensory block below level of lesion
Degree of muscle tone may be helpful; relaxation of spasticity/hypertonia

Greater implications from the complications of blocks e.g. phrenic nerve paralysis from BPB in those with impaired respiratory function

Premedication

Avoid:

Sedative pre-medication - can reduce respiratory drive
Anticholinergic pre-medication - not effective in reducing autonomic dysreflexia

Nifedipine pre-medication may be effective

Monitoring

AAGBI as standard
May need A-line or CO monitoring if major surgery involving fluid shifts

Anaesthetic agents

Typically require lower doses of induction agents are required, due to lower blood volume and muscle mass
No evidence any one induction agent is superior to any other
Non - depolarising NMBA ok
Maintenance with TIVA or volatile agents

Airway management

Anticipate difficult airway
Ensure safe neck positioning
Low threshold for awake tracheal intubation
In those with existing uncuffed tracheostomies, switch for a cuffed tracheostomy

Care bundle

Meticulous positioning owing to increased risk of pressure injuries
Maintenance of normal temperature
Intra-operative VTE prophylaxis
Antibiotic prophylaxis as indicated

Multi-modal analgesia depending on the surgery, although avoid opioids where possible as may exacerbate existing respiratory issues
May need planned period of NIV post-operatively e.g. HDU
Ventilation may be aided by recovery in supine position (for those with cervical injuries)