Transport of patients with spinal injuries
Dr TERRY MARTIN, Director of CCAT Aeromedical Training, gives us some important information about a common but always tricky type of repatriation.
Spinal injuries
Whether acting as the sole escort for a spinal patient or as part of a team, the flight nurse needs a thorough understanding of the pathophysiology of spinal trauma in order to make sensible and efficacious clinical decisions.
The most difficult cases are those with injury to the spinal cord and associated sympathetic chain. Normal physiology can be grossly deranged in these patients and the exact nature of the dysfunction depends on the level and severity of the damage.
Aeromedical escorts involved with secondary and tertiary transfers will be expected to have a comprehensive knowledge and understanding of the injury or condition before departure. This usually requires an in-depth face-to-face handover between the flight medical team and a senior neurosurgeon (or orthopaedic surgeon in some centres), as well as a senior member of the nursing team.
ATLS/Advanced Trauma Care for Nurses (ATCN) skills and expertise are essential, but the knowledgeable flight team will also take special aeromedical factors into consideration. Like all critically ill patients, spinal patients are particularly susceptible to the stresses of flight - that is, the hypoxic environment at altitude, gas expansion, "abnormal" accelerations, vibration and variations in temperature.
In essence, they have a number of potential issues and complications which, unless managed pre-emptively, can lead to significant deterioration en route. The most appropriate way to consider these issues is by the traditional "ABC" approach.
Airway and Breathing
"C3, 4 and 5 keep the diaphragm alive" is a familiar saying that reminds us of the innervations of the major muscle of respiration. Impaired ventilation is a common consequence of diaphragmatic paralysis, especially as intercostal muscles (innervated by T1 to T12) are also affected.
Since subsequent hypoxia may be exacerbated in any patients with accompanying chest injuries, a full pre-flight pulmonary assessment is essential to ensure that those patients requiring supplemental oxygen or ventilation are identified and appropriately managed.
Monitoring of oxygen saturation is essential, and measurement of end tidal carbon dioxide will help identify hypoventilation (which will be seen as hypercapnia) in those at risk. Regular suction of the airway may be essential to prevent aspiration in those who are conscious and a cuffed endotracheal or tracheostomy tube will be required in those who are not.
Circulation - neurogenic shock
Trauma in the high thoracic and cervical spine often involves damage to the sympathetic chain and loss of sympathetic responses below the level of the lesion. Since vascular "tone" (that is, the amount of constriction) is controlled by the sympathetic nerves, blood vessels become dilated.
On the other hand the vagus parasympathetic nerves which usually balance the vasomotor tone are unaffected by the spinal damage since they leave the brain above the injured zone. Hence vasomotor control becomes unbalanced. Sympathetic drive to the heart usually causes a tachycardia. Without sympathetic drive, the lack of opposition to vagal influence on the heart produces a bradycardia.
Bradycardia
This combination of unopposed vagal (parasympathetic) stimulation and loss of vascular tone results in neurogenic shock. This state is pathognomically characterised by "hypotension in the presence of bradycardia".
Such "relative" hypovolemia caused by vascular dilation and venous pooling will exacerbate the physiologic effect of any true fluid losses. Hence, intravenous access is essential and should be in place before the journey is started.
The bradycardia caused by unopposed vagal influence may progress to asystole when the vagus is further stimulated by such procedures as the placement of an oropharyngeal or nasopharyngeal airway, nasogastric tube or urinary catheter. Atropine, a potent parasympatholytic agent, may be administered prior to all such manoeuvres, and the ECG should be monitored throughout the transfer.
Pulmonary thromboembolism
The spinally injured patient with circulatory impairment is also at risk of pulmonary thromboembolism, which may result in ventilation/perfusion mismatches, hypoxia, acute right-sided heart failure and pulseless electrical activity (electromechanical dissociation). Patients without other acute traumatic injuries at risk of bleeding should therefore be stabilised on anticoagulant therapy prior to departure.
The risk of emboli is greatest during the second and third weeks after injury. Gentle massage may stimulate sluggish circulation and elastic stockings should be worn to minimise the risk of deep venous thrombosis.
Other important considerations
Thermoregulation: Vasomotor lability and sensory impairment prevent adequate thermoregulation and patients may be prone to both hypothermia and heat intolerance. Great care should be taken to ensure that the cabin environment is comfortable for the patient, especially in smaller aircraft which often have poor cabin heating. The patient also requires thermal protection from both heat and cold during the ground phases of the transport.
Decubitus ulcers: In combination, paralysis and impaired sensation may lead to pressure sores, especially when the tissues are under-perfused and hypoxic. Care should be taken to ensure that the patient is lying on a soft, smooth surface and that no hard objects or intrusions impinge on the patient's skin.
Extra diligence is required to treat those areas at particular risk. Soft fluid packs over the heels and ankles or sheepskin booties are helpful, but don't substitute for frequent movement of the patient to disperse the load onto other areas. Most authorities agree that patients should be moved at least once every two hours.
Lifting and moving devices: Arrangements for the safe turning of the patient must be made when the journey will exceed two hours. Simple arrangements may include the use of a rigid backboard or vacuum mattress, cervical collar and head restraint.
The board/patient unit is periodically turned from side to side to relieve pressure areas and help ventilation by recruiting closed alveoli. Although transfer on a spinal board is preferable for prehospital patients being moved to an initial receiving facility, this mode of carriage is uncomfortable in those with residual sensation and may cause pressure sores in patients with sensory loss.
Modern spinal boards offer a degree of protection with soft padding, but the problem still occurs with long transfers. A scoop (clamshell) stretcher is useful for safely transferring patients between stretcher types and between stretchers and beds, but should not be used in place of a turning frame or vacuum mattress.
The patient should be alternately rotated 30 degrees to each side of the long axis of the body interspersed with periods lying supine. Most patients can be transported satisfactorily on a vacuum mattress conformed to the patient's body contours and lined with a sheepskin blanket.
Cervical traction: A patient whose cervical spine has already been stabilised may well have traction tongs in situ and, like any form of skeletal traction, cervical traction must be maintained by a closed system. Free-hanging weights are susceptible to accelerations and to the effects of increased gravitational forces, and their use may cause pain and further damage such as distraction injury. They should not be used at any stage in the transfer of patients by air.
Gastrointestinal considerations: At altitude, stomach gas volume expands and this may splint the diaphragm, causing impairment of ventilation and increasing the risk of aspiration. A freely draining nasogastric tube should therefore be placed before flight, and a pro-kinetic such as metoclopramide may be useful to help empty the stomach. However, conscious patients are more prone to motion sickness and a more reliable anti-emetic should also be used, such as cyclizine.
Micturition: If a urinary catheter is in situ, it may be best to replace it before departure since sensory loss will mask a full bladder caused by a blocked tube and catheter replacement in flight can be difficult. A further advantage to an indwelling catheter is the ability to measure hourly urine output as a guide to the adequacy of circulating volume.
Post traumatic stress disorder: Conscious patients with spinal injuries require reassurance, tact and psychological support. Flight medical personnel should therefore tell patients and relatives about why such fastidious precautions are being taken. This will help invoke trust.
Reassurance that the appropriate standard of care is being given even though the patient is in between hospitals is essential. Most lay people will view the transport phase as a move from one place of safety to another, with a stressful and dangerous period of uncertainty between the two, and they may well judge the aeromedical crew against the hospital staff that they have probably come to know quite well.
It is therefore not advisable for flight escorts to enter into discussion about the likely outcome of the patient's injuries, and all enquiries should be politely referred to the receiving medical team, stating that they are the experts in the next stage of the patient's care and, as such, will soon be in possession of more information.
If comments are made, they may be quoted, or - worse - misquoted later, especially if the patient, family member or legal representative is looking for possible blame factors for the patient's condition.
Summing up
Armed with knowledge of the pathophysiology of spinal cord injury, safe and efficacious transfers can be completed as long as proper preparation and appropriate prophylactic measures are taken. However, the transfer phase is often seen as an interruption in "proper hospital management" and flight medical crew must be on their guard at all times.
Finally, as a defence against unnecessary litigious involvement, it is essential to document the transfer thoroughly, especially details of the handover examination and any discussions with the patient or family.