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Cervical spine clearance in the unconscious patient

Created: 22/5/2007
 

Cervical spine clearance in the unconscious patient



Dr John Griffiths DICM MRCP FRCA MA 
CriticalCareUK Editor


Focus on cervical spine injury

Cervical spine injury (CSI) complicates 2-5% of cases of polytrauma. CSI is considerably more common in the following groups:

  • Head injury: cervical spine and head injury may be associated in up to one third of cases.
  • Non-contiguous spinal injuries: one traumatic spinal injury will be associated with a second anatomically unconnected injury in up to 40% of cases.
  • Supraclavicular fractures: excluding facial fractures.

Across the United Kingdom an estimated 1,000 new cervical cord injuries occur per year, principally as a result of road traffic accidents. Moreover, 100 head injuries per 100 000 population occur per year. Modern trauma care appropriately assumes that CSI is present until it is excluded. Conscious trauma patients who are able to report symptoms and meet recognized screening criteria can be regarded as having a stable cervical spine. However, most patients with multiple injuries who are ultimately admitted to the ICU are frequently rendered unconscious or sedated, intubated, or have a serious head injury and are not appropriate for the clinical exclusion of CSI.

Focus on the techniques to "clear" the cervical spine

Cervical injury may be excluded using any of five techniques:

1. Clinical signs and symptoms

2. Plain Radiographs

3. Computerised Tomography (CT)

4. Dynamic Fluoroscopy

5. Magnetic resonance Imaging (MRI)


Since clinical exclusion of CSI is unproved and often impossible in patients with multiple injuries, reliable imaging of the cervical spine is imperative. The three view cervical series (lateral, anteroposterior and odontoid) has many technical limitations in intubated patients producing a functional sensitivity of 90%. CT alone has sensitivity similar to plain radiographs. However, plain cervical radiography combined with CT is extremely sensitive; less than 1% of injuries will be missed. Combined screening with plain radiographs and directed CT may have a false negative rate as low as 0.1%, including serious ligamentous injuries.

Dynamic fluoroscopy is a pragmatic and evolving technique involving passive manipulation of the cervical spine under real-time fluoroscopic imaging. However, for dynamic fluoroscopy to detect one further injury beyond plain radiographs and directed CT, the number needed to treat is in excess of 500 and has a false negative rate of 0.33%. A recent study also found that only 4% of dynamic studies visualised the entire cervical spine. Current considered opinion, therefore, is that the technique lacks conclusive evidence regarding its use in screening CSI in unconscious patients with multiple injuries.

The use of MRI requires a more difficult and distant transfer of a critically ill patient from the ICU in addition to all the problems of ferromagnetic compatibility for monitoring and the provision of anaesthesia. It is estimated that only half of modern MRI units in the UK presently have scheduled anaesthetic provision, making the screening of critically ill patients unsafe. Furthermore, while felt to be sensitive for soft tissue, MRI frequently lacks specificity and sensitivity for posterior element injuries and fractures. MRI is therefore unlikely to become routine for screening injuries of the cervical spine among critically ill patients for the foreseeable future.


Table 1.

General Principles of combined plain radiography and CT screening for CSI

· Suboptimal and anatomically incomplete imaging, combined with misinterpretation account for the largest number of missed injuries

· The craniocervical and cervicothoracic junctions frequently "conceal" injuries and 25% of plain films are technically inadequate. CT allows evaluation of these sites, especially among intubated patients

· CT typically detects more fractures, plain films detect more malalignments; the two modalities performing in a complimentary fashion

· The three view cervical plain radiography series and directed CT consistently detect >99% of CSI

· Entire cervical spine CT may detect injuries in a further 8-14% of patients

· CT scanning does not add excessive time to trauma evaluations and is time and cost-effective

· High resolution CT at 1.5-2mm collimation and pitch may be the best compromise between sensitivity, scan-time and radiation dose



Focus on consensus for “clearing” the cervical spine

A recent survey of Northern Ireland's intensivists and trauma surgeons showed diverse practices. This survey showed that 12.5% of clinicians believed that plain radiography was adequate to exclude cervical injury. Other workers have shown that 48% of UK intensive care units and 12-16% of American specialists were prepared to clear an unconscious patient's cervical spine by using a solitary lateral plain radiograph. The lack of consensus regarding optimal evaluation applied to the common scenario of "clearing" the cervical spine in the ICU or emergency department is evident. All existing guidelines and recommendations in this field remain level 2-3 recommendations, and are summarized in Box 1. However, Morris et al propose that the screening and excluding injury of the cervical spine in unconscious patients with multiple injuries by plain radiography and directed CT is sufficiently sensitive and widely available to be recommended for routine use in most trauma units. Moreover, trauma units with access to a helical, multiplane CT scanner should routinely image the entire cervical spine at high resolution since the number needed to treat to detect a further injury beyond directed scanning may be only 8 to 22 patients. The recent recommendations of Morris et al are shown in figure 1. These have been incorporated into a consensus statement from the Intensive Care Society and could form a national minimum standard of imaging and management of an unconscious patient with a suspected CSI.


Fig 1. Proposed algorithm to clear the cervical spine in unconscious trauma patients

Adapted from Morris C G et al. BMJ 2004



Focus on the complications of spinal protection precautions

"Spinal protection precautions" include spinal boards for transfer, prolonged nursing in a supine position on a firm mattress, the application of cervical collars, lateral restraints, head tapes, and surgical stabilisation of identified injuries as indicated. The benefit conferred by routine application of some of these elements, particularly spinal boards and cervical collars has been questioned. Most neck injuries involve the C6-7 region and since emergency collars only extend down to the level of C7, these collars may not afford any direct protection. In fact they have the potential to add to the stresses on the damaged segment. By immobilising the upper cervical spine the collar will create a long lever which transfers the forces generated by head movements directly to the injured area of the neck.

Long spinal boards are an aid for extrication and not spinal immobilisation and should be removed on initial assessment. Many in-hospital practitioners may not be aware of the risks a patient is exposed to by being left on a hard board for a prolonged period. In addition they may not be aware of the period of time on a board in the pre-hospital environment. Unconscious patients and those with significant spinal injuries represent the most vulnerable groups in that they are clearly unable to complain and cannot move to redistribute pressure whilst lying supine. Long spinal boards are associated with significant cutaneous complications and furthermore remove the natural lordoses of the lumbar and thoracic spines.

An emergency cervical collar has an important function in alerting carers to the need to avoid stresses on the neck by always moving the body and head in one piece i.e. ‘log- rolling’. As long as this rule is followed the collar is safe when used on a recumbent patient.

The more common complications of prolonged immobilisation and spinal precautions are listed in Table 2. Most of the complications are poorly recorded, acting synergistically to produce less apparent or attributable adverse events.


Table 2

Complications of prolonged immobilisation and spinal precautions


Cutaneous pressure ulceration

Elevated intracranial pressure and venous obstruction

Difficult intubation and loss of the airway

Difficulty in obtaining central venous access

Inability to provide good oral care

Failed enteral nutrition

Gastrostasis, reflux, and pulmonary aspiration

Restricted physiotherapy regimens

Thromboembolism

Increased risk of cross infection


Focus on skin ulceration in immobilised patients

Cutaneous pressure ulceration is common and increases with prolonged use of collars, particularly after 48-72 hours, and may occur in up to 55% of patients. The requirement for skin grafting has been reported by 18.8% of specialists. Additional risk factors for cutaneous necrosis include prolonged periods of immobilisation, lack of posture change, and the use of spinal boards. "Pressure sores" are a significant cause of morbidity, and sometimes mortality, that require prolonged time to heal—each ulcer costing about £17000.


Key Learning points

  • Prolonged immobilisation on a long spinal board and use of a cervical collar are associated with notable morbidity most commonly secondary to cutaneous pressure necrosis.
  • The removal of cervical collars and patients' mobilisation should be a priority for management of an unconscious patient with a suspected CSI.
  • At the present time no general consensus exists with regard to the optimal evaluation.
  • A national framework for investigation and management is a future possibility.
  • There remains a need for an adequately powered, prospective comparison of all diagnostic modalities that would guide and justify any possible recommendations.


Box 1: Existing management guidelines and protocols

Advanced trauma life support (ATLS) guidelines and cervical spine injury

"For patients who are comatose, have an altered level of consciousness, or are too young to describe their symptoms: all such patients should at least have a lateral and AP c- spine x-ray. Whenever possible, an open-mouth view also should be obtained. If the entire c- spine can be visualised and is found to be normal, the collar can be removed after appropriate evaluation by a neurosurgeon or orthopaedic surgeon.... When in doubt, leave the collar on... a cervical computed tomography scan can be obtained somewhat later."

Eastern Association for the Surgery of Trauma (EAST) guidelines

"A three view spine series supplemented by thin cut axial computed tomography images with sagittal reconstruction through suspicious areas or inadequately visualised areas provides a false negative rate of less than 0.1%... computed tomography alone, MRI and flexion/extension radiographs have all been shown to miss injuries and have not been shown to be more accurate...."

Revised EAST guidelines and cervical spine injury
The most recent EAST guidelines were issued in 2000 and recommend dynamic fluoroscopy in unconscious patients:

"Altered mental status and return of normal mental status not anticipated for 2 days or more (eg severe traumatic or hypoxic brain injury).... Plain films... axial computed tomography images at 3mm intervals with sagittal reconstruction from the base of the occiput through C2... if normal, flexion/extension lateral cervical spine fluoroscopy...."



Key References

American College of Surgeons Committee on Trauma.
Advanced trauma life support for doctors student course manual.
Chicago: American College of Surgeons, 1997.

EAST Ad Hoc Committee on Practice Management Guideline Development.
Practice management guidelines for trauma from the Eastern Association for the Surgery of Trauma.
J Trauma 1998;44: 941-6.

Eastern Association for the Surgery of Trauma.
Determination of cervical spine stability in trauma patients.
Winston-Salem: EAST, 2000. http://www.east.org/tpg.asp

Morris CG, McCoy E.
Cervical immobilisation collars in ICU: friend or foe?
Anaesthesia 2003;58: 1051-3.

Morris CG, McCoy E.
Clearing the cervical spine in unconscious polytrauma victims; balancing risks and effective screening.
Anaesthesia 2004;59: 464-82.

Morris CG, McCoy W, Lavery GG.
Spinal immobilisation for unconscious patients with multiple injuries.
BMJ 2004; 329: 495- 499.

Gupta KJ, Clancy M.
Discontinuation of cervical spine immobilisation in unconscious patients with trauma in intensive care units—telephone survey of practice in south and west region.
BMJ 1997;314: 1652-5.


ArticleDate:20070522
SiteSection: Article
 
   
    
                                            
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