Anatomical location of SCI

The most common site of traumatic SCI is the cervical portion of the spinal cord, accounting for approximately 60% of all traumatic SCI, followed by lumbar and thoracic. Thoracic cord injuries are less common due to the increased biomechanical support offered to this portion of the cord by the thorax.

Level of injury

A SCI can be described as having a neurological level, which is determined by detailed assessment of motor and sensory function. The sensory level is the most caudal, intact dermatome for both pinprick and light touch sensation. The Medical Research Council’s muscle power scale (MRC scale) is used to assess motor function. The motor level is the lowest key muscle function that has a muscle function strength of at least three (corresponding to active movement against gravity), providing the key muscle functions represented by segments above that level are judged to be intact. The neurological level of a SCI is the most caudal level at which the individual has both intact sensation and muscle function strength of at least three.

Complete versus incomplete SCI

If examination confirms that sensory or motor function is preserved at the S4–S5 level (sacral sparing), then the injury is described as incomplete. In contrast, loss of such function confirms a complete spinal cord injury.

ASIA spinal injury classification system ( Figure 1 )

The American Spinal Injury Association has published an International Standard for Neurological Classification of Spinal Cord Injury (ISNCSCI, or more commonly known as the ASIA score). This document grades injuries according to their neurological level and extent of SCI. It is usually performed with 72 hours of the time of injury. The ASIA system has gained widespread use as a means of accurately quantifying the severity and prognosis of SCI.

ASIA score and spinal injury assessment.

Common spinal cord injury syndromes

Paraplegia describes a reduction in motor and/or sensory function in the lower limbs with varying truncal involvement, resulting from damage to the cord at a thoracic or lumbar level. In contrast, tetraplegia refers to a reduction in motor and/or sensory function in all limbs, often resulting from a cervical cord injury.

Central cord syndrome is a distinct presentation that tends to affect older individuals with degenerative cervical vertebral disease. It classically occurs following traumatic hyperextension of the cervical spine, with transient compression of the cord resulting in damage to the central portion of the cervical cord. Clinically, this presents as an incomplete injury with sensory and motor dysfunction affecting the upper limbs more than the lower limbs. Central cord syndrome is the most common incomplete SCI.

Initial assessment

Pre-hospital handover information is vital. Knowledge of mechanism of injury can alert the resuscitation team to a possible level of SCI as well as other potential injuries, particularly if the patient has a reduced conscious level or has a sensory deficit. The primary survey should be completed with minimal mobilization of the patient. Spinal column immobilization using a cervical collar, blocks and tape, and maintaining alignment of the spinal column by logrolling, are crucial in preventing exacerbation of the primary SCI. A single log-roll is used to examine the back and spine, perform a PR exam, and remove the patient from a spinal board or scoop. Logrolls should be performed with adequate numbers of trained staff and clear instructions from the team leader to ensure a neutral spine position at all times. Collars, blocks and tape are frequently applied at the scene of a trauma, but can still be applied in the emergency department if they are not present and concerns regarding cervical spine stability arise. Patients may be poorly compliant with immobilization for a number of reasons, including pain, head trauma, a full bladder and drugs (recreational or prescribed). Such patients should be encouraged to lie flat and remain still, but should not be restrained or forcibly held down. Similarly, a patient’s neck should not be forced in to a neutral position to apply a collar, and a deformity should never be reduced or manipulated in this setting.

During the primary survey, it is important to remember that SCIs often result from significant mechanisms, and therefore other injuries are common. Up to a third of polytrauma patients also have a SCI. Furthermore, patients may be unable to feel pain from other injuries below the level of their SCI, and so other injuries are frequently missed. Throughout the initial management, remember that an expanding area of ischaemia in the spinal cord can result in an ascending neurological deficit and manifest as clinical deterioration for up to several days after the injury. Patients may lack the ability to vasoconstrict or shiver, and can rapidly lose body heat, and so should remain covered as much as possible during initial assessment and resuscitation.

Airway

Ensuring adequate oxygenation is vital in preventing ischaemia and secondary cord injury. Airway compromise may occur for a variety of reasons, including obstruction by foreign bodies or vomitus. Additionally, patients with cervical and thoracic cord injuries will have impaired intercostal and/or diaphragmatic function, causing respiratory failure that may require invasive or non-invasive support. Airway assessment prior to intubation can be difficult if the patient is in a hard collar or uncooperative. A collar will restrict mouth opening, jaw movements, and neck extension, as well as limiting a visual inspection of the patient’s chin and neck. Patients may be at increased risk of aspiration given their unfasted status, the effect of prehospital drugs that can slow gastric emptying such as opioids, or autonomic dysfunction resulting in paralytic ileus and loss of gastroesophageal sphincter tone.

Endotracheal intubation may be difficult for a multitude of reasons, and the involvement of medical staff with experience in managing difficult airways is recommended. Patients may have facial injuries or swelling that may make laryngoscopy difficult, oedema or haematoma from a fracture site, or there may be foreign bodies, blood or vomit in the airway. Reduced GCS or respiratory failure may add time pressures and additional stress to the situation. If time allows, transferring the patient to a familiar environment such as theatre may be beneficial. An intubation checklist, such as the one published by the Difficult Airway Society, should be used. The choice of drugs and airway equipment best to use in this situation is a matter of opinion, but should be a technique with which the operator is familiar. It should adhere to the principles of maintaining adequate oxygenation throughout, avoiding movement of the cervical spine and avoiding hypotension. In our institution, this would be a two-person technique as it is very difficult for one person to administer anaesthesia, intubate and ensure spinal immobilization. Manual in-line stabilization (MILS) is used to stabilize and maintain alignment of the spinal cord while the front of the collar is opened to allow adequate mouth opening for laryngoscopy. Cricoid pressure is best avoided if there is a known or suspected cervical cord injury. After a period of preoxygenation, anaesthesia is induced intravenously and muscle relaxation is administered. Suxamethonium is absolutely contra-indicated after 48 hours due to potentially fatal hyperkalaemia secondary to upregulation of acetylcholine receptors in denervated muscle. It is permissible to use in the acute setting, but can still cause profound bradycardia, particularly with lesions above T6. High dose (1.0 mg/kg) rocuronium may be a safer alternative. A videolaryngoscope is then used to visualize the vocal cords, with a difficult airway trolley nearby in case of difficulty. The use of a gum elastic bougie or stylet should be considered to allow minimal force laryngoscopy and minimal neck extension. Intubation using a fibreoptic scope – either awake or asleep – is an alternative to videolaryngoscopy. The perceived benefit of an awake technique is the ability to monitor for changes in neurological symptoms during laryngoscopy. An awake fibreoptic technique can be considered if the patient is stable and co-operative, and the necessary expertise is present. Note that blood or secretions in the airway can impair both videolayngoscopy and fibreoptic techniques. Once endotracheal intubation is confirmed, the tube should be secured using tape or a tie that does not compress the neck. Hypotension during induction should be avoided and treated promptly as this can cause secondary cord injury.

Breathing

Breathing is variably affected depending on the level and severity of the lesion. Lesions above T8 start to impede ventilation, as progressively more of the intercostal muscles become paralysed. The diaphragm is innervated by C3–C5, and lesions at this level can result in acute respiratory failure requiring immediate intubation. Lower cervical lesions will spare the diaphragm but result in complete intercostal paralysis, which can cause a paradoxical indrawing of the chest during inspiration. There is decreased vital capacity, decreased functional residual capacity – resulting in more rapid desaturation during laryngoscopy – and a poor cough. Depending on the mechanism of injury, other factors may contribute to hypoxaemia such as chest trauma, aspiration or smoke inhalation. Serial physical assessment and arterial blood gas sampling help in identifying clinical deterioration. Patients with cervical or high thoracic injuries, in which the diaphragm plays a crucial role in ventilation, are better nursed flat as the diaphragm is pushed upwards into the chest by the abdominal contents, permitting maximal movement during inspiration.

Patients who require mechanical ventilation may have a protracted period of ventilation and may benefit from a tracheostomy, allowing discontinuation of sedative medications. Percutaneous tracheostomy may be difficult due to inability to extend the neck, thus surgical tracheostomy may be preferable. Patients with complete lesions above C2 will often require long term ventilation. Patients with lesions below C5 are potentially weanable in the long-term, as the initial flaccid paralysis of the intercostal muscles develops in to spasticity and splints the chest during inspiration. Patients with lesions at C3–C5 are variable.

Patients with cervical lesions should be managed in an appropriate critical care setting in the short term, even if unintubated, due to the high potential for deterioration. Evidence suggests that higher tidal volumes of between 10 and 20 ml/kg of ideal bodyweight, higher than the more familiar ARDSnet recommendations of 6–8 ml/kg, are beneficial for these patients. ^, These higher volumes can help to prevent atelectasis and mucous plugging, and reduce time to weaning. Peak airway pressures usually remain within normal limits due to flaccid paralysis of respiratory muscles. The critical care team must consider the potential risks of using these higher tidal volumes, such as barotrauma and acute lung injury, on a case-by-case basis.

Circulation

Neurogenic shock is common in patients with SCI above the level of T6, due to the loss of sympathetic outflow to the peripheral vasculature resulting in vasodilation, bradycardia and hypotension. Lesions at this level can also result in severe bradycardia or even asystole during vagally-stimulating procedures such as laryngoscopy or suctioning, and chronotropic medications such as atropine or glycopyrrolate may be required. Neurogenic shock is resistant to fluid resuscitation, and usually requires vasopressor and potentially inotropic support to maintain cord perfusion and prevent secondary injury. Invasive blood pressure monitoring by means of an arterial line is recommended, and a central venous catheter allows for administration of vasoactive drugs and monitoring of central venous pressure. In addition to neurogenic shock, other forms of shock may be present as a result of sepsis or haemorrhage, and so patients may present with a mixed clinical picture. Patients will be unable to mount an appropriate response to haemorrhage/hypovolaemia, and may be asymptomatic of any other major injuries.

Disability – neurological assessment

If there is a motor or sensory injury apparent on primary survey then a full neurological examination should be performed. Use of the ASIA scoring system allows the user to easily describe an injury, and will aid communication with the local spinal injury centre. If the patient is too physiologically unstable to comply with a thorough assessment then this will have to be delayed, but gross movements and sensory deficits prior to anaesthesia should be documented. A full neurological examination includes motor and sensory examination, reflexes, examination of the back and a rectal examination. The latter two should ideally be performed at the same time as the patient is being log rolled off the spinal board to minimize unnecessary movements.

If there is a clinical concern over possible SCI then urgent neuroimaging is warranted. In the case of a polytrauma patient, CT scan from head to mid calves – including the whole spine – is performed to exclude other injuries of which the patient may be asymptomatic. NICE guidelines recommend assessing the cervical spine using the Canadian C-spine rules, and if a cervical injury is suspected then a CT of the cervical spine is required. CT scans will recognize bony injury but are poor for assessing the cord itself and, for example, would not diagnose cord oedema or haematoma. An MRI scan is therefore required for the patient with clinical manifestation of SCI, with or without an abnormal CT. MRI will diagnose both vertebral and cord pathology but takes much longer, is often in a location distant from the emergency department, and can be a challenging environment to provide an anaesthetic given the limitations of working next to a powerful magnet. For these reasons, CT is the initial investigation of choice, but an urgent MRI may be required to exclude indications for immediate surgery, such as vertebral haematoma.

Screening tools such as the Canadian C Spine Rules aid in decision making around imaging where there is a possibility of SCI based on mechanism of injury.

Steroids

The main studies regarding steroid use are the National Acute SCI Studies (NASCIS) 1, 2 and 3. NASCIS 1 showed no difference in outcome between high and low dose steroid groups, but did not include a control group. NASCIS 2 compared steroid, naloxone and placebo. A controversial post-hoc analysis suggested steroids within 8 hours of injury did provide some benefit, but subsequent trials were unable to replicate this. NASCIS 3 compared steroid treatment for 24 or 48 hours and found no difference between the groups. However, the studies did find clinically significant increases in complication rates, including wound infections, pneumonia, and sepsis, in the steroid groups. As such, steroids are not currently recommended in the treatment of SCI.

Haemoglobin and blood pressure targets

Optimal targets are currently unknown. There is some evidence that maintaining a mean arterial pressure of >85 for 5–7 days results in a more favourable outcome, but the evidence for this is weak. Noradrenaline, phenylephrine or metaraminol are generally the vasopressors of choice, with dopamine if inotropy is also required. ^, It is also not known if the usual restrictive haemoglobin target of 7–9 in critical care patients is appropriate, or whether we should be aiming for higher haemoglobin concentrations to improve oxygen delivery to the ischaemic spinal cord. The effect of cardiac disease on this is also not known, and an individualized approach is recommended.

Surgery

Neurosurgical intervention may benefit some patients with acute SCI. Surgery may be indicated to decompress a mass lesion causing progressive neurological deficit, or to fix an unstable injury. The aims of SCI surgery are to prevent any further damage or secondary injury, allow removal of immobilization devices and precautions, and allow rehabilitation to begin. The timing of surgery is controversial, although earlier surgery may reduce duration of hospital stay and associated complications. In cases of incomplete lesions, neurophysiological monitoring is often used during surgery to reduce the risk of further damage.

Role of spinal injury centre

Patients with significant injuries are best managed in specialized spinal injury units (SIUs). These centres allow access to an expert multidisciplinary team of spinal injury physicians, spinal surgeons, neurologists, anaesthetists, nursing staff, specialist physiotherapists, psychologists and occupational therapists. Patients cared for in SIUs have reduced mortality, reduced length of stay, better functional outcomes and lower rates of complications, compared to patients managed in general hospitals. National guidelines recommend that transfer to the appropriate SIU should take place as soon as is safely possible. Factors that may delay transfer include the requirement for management of other injuries, or multi-organ failure rendering the patient too unwell to transfer. In this event, the responsible clinicians should liaise with the SIU as soon as possible for advice on management of the SCI and organize transfer as soon as these issues have been resolved. Some SIUs will accept patients who are intubated, mechanically ventilated or on sedative or vasopressor infusions, so this should not necessarily prevent transfer. Transfer to a SIU should be performed by an appropriately trained and experienced member of staff, and care should be taken to ensure the patient is immobilized, pressure areas are well padded, and a full neurological examination (if possible) is documented.

Further management

A key aim in the acute management of SCI is to prevent the complications of immobility. Pressure sores can develop over a matter of hours, and have potentially devastating consequences if they become infected. Regular positional changes and the use of pressure-relieving mattresses can minimize the chance of pressure sores developing. SCI patients are at high risk of thromboembolism, and thromboprophylactic measures such as mechanical compression devices and low molecular weight heparin should be started as soon as possible. Most patients will require a urinary catheter, and there is no evidence to suggest this should be avoided in cases of priapism. A nasogastric tube can help with nausea and vomiting in cases of delayed gastric emptying and paralytic ileus, and also allow for early feeding. Loss of sympathetic flow to the GI tract results in increased gastric acid production, and so pharmacological gastric protection is necessary. Bowel care, including laxatives and suppositories, is often required. Thermoregulation is impaired below the level of the injury, and patient temperature needs to be monitored and controlled. Normoglycaemia should be targeted. Neuropathic pain is common following acute SCI and this should be managed appropriately.

Long-term management of these patients includes specialized rehabilitation and physiotherapy programmes, along with patient and family education, home and transport modifications, and consideration of psychosocial implications.

Prognosis and outcomes

Individuals who sustain SCI are understandably anxious to know if their symptoms will improve and how this will affect their lives. Fortunately, with high quality care, there is a significant rate of improvement in symptoms and function. Around 10% of patients who are ASIA A at presentation will improve to ASIA B or better, but up to 50% of ASIA B patients will improve to ASIA C or D, with the majority of C and D patients being ambulatory by discharge. The majority of patients with incomplete injuries (ASIA B-D) are functionally independent at 1 year. The highest rates of mortality in SCI are among older patients, those requiring long-term ventilation and those with high cervical cord injuries. For many of those who survive, alterations and modifications have to be made in terms of occupation, social function and living accommodation.

Airway and respiratory management

Gastroparesis resulting from autonomic dysfunction may increase the risk of gastroesophageal reflux. This may guide the clinician towards airway devices, such as cuffed endotracheal tubes, that offer a greater degree of protection against aspiration. Previous cervical spinal fixation may reduce neck extension and make laryngoscopy more challenging. Furthermore, those patients who underwent tracheostomy in the aftermath of their initial SCI may develop subglottic stenosis thus making intubation more difficult. The avoidance of depolarizing muscle relaxants is wise given that these can cause significant hyperkalaemia and cardiac arrest in this population due to proliferation of acetylcholine receptors. The use of non-depolarizing muscle relaxants is preferable. There is an increased prevalence of obstructive sleep apnoea in individuals with SCI, and this is an established risk factor for difficult airway management. Cervical and thoracic SCI will, to differing extents, impair respiratory function as a result of diaphragmatic and intercostal muscle weakness, causing a corresponding reduction in FVC and FEV1. Given their increased risk of atelectasis and lower respiratory tract infection, post-operative critical care admission should be considered, and the possibility of prolonged mechanical ventilation discussed with the patient.

Circulation

Autonomic dysfunction following cervical and high-thoracic SCI can result in hypotension and bradycardia. Individuals are at increased risk of orthostatic hypotension and thus care should be taken when manoeuvring them into an upright position. Intraoperative hypotension is more common and the ability to compensate for hypovolaemia is impaired, resulting in significant hypotension. In cases where there is likely to be significant fluid shift or bleeding, invasive blood pressure monitoring should be considered.

Neurological function

Chronic pain and depression are common among those living with SCI. Chronic pain may result from muscle spasms and contracture, or may be neuropathic in nature. Resultant chronic analgesic use may make acute and postoperative pain more difficult to control. Autonomic dysfunction can lead to impaired bowel and bladder function, and long-term urinary catheterization and consequent infection is common.

Autonomic dysreflexia (AD) is a medical emergency that occurs in up to 90% of patients with SCI at T6 or above. A triggering event, usually occurring below the neurological level of the SCI, causes an aberrant autonomic response resulting in unmatched parasympathetic overactivity above the level of the SCI. This is manifested by facial flushing, headache, anxiety, sweating, hypertension and bradycardia. Although the causes of AD are legion, most cases are caused by bladder or bowel issues such as urinary retention or faecal impaction, and these factors should be actively excluded. Prompt recognition and management of AD is essential as, if untreated, it can precipitate seizures and intracranial haemorrhage.

Treatment involves removing the trigger and managing the blood pressure until the episode subsides. Tight clothing or devices should be loosened, the bladder should be emptied or catheter checked to be patent, bowels emptied and skin checked for any pressure areas. The patient should be sat up or have their head elevated and legs lowered. If there is painful stimulus, then adequate analgesia should be given. For severe episodes, a short acting antihypertensive agent such as GTN may be required.

Musculoskeletal and soft tissue issues

Osteoporosis as a result of immobility is common and increases the risk of fractures. Pressure sores are a common reason for readmission following SCI, and can result in life-threatening infection and the need for surgery. Extreme care should be taken to avoid pressure ulceration, especially during long surgical cases. Patients can suffer from limb flexion deformities, and IV access can be difficult.

Anaesthetic and analgesic techniques in SCI

Regional anaesthetic techniques such as spinal anaesthesia or epidural analgesia are recognized as being safe in patients with SCI, and may have the additional advantage of reducing the likelihood of AD in patients having surgical stimulation below the level of the cord lesion. Spinal and epidural anaesthesia may be technically challenging for a variety of reasons including abnormal anatomy, the presence of metalwork following spinal fixation surgery, difficulties in assessing the block, and orthostatic hypotension may occur if sat upright for a procedure. Epidural analgesia is safe and effective in women with SCI who are experiencing pain during labour. It may be worth leaving the epidural in situ for a period after delivery as post-partum uterine contraction may precipitate AD.