Medical Indications for evacuation
In general, the reasons to initiate the evacuation of a patient from a sea-going vessel are:
- Medical conditions which are of such nature that lasting invalidity or death may result and for which treatment on board is not feasible.'
- Medical conditions in which the diagnosis is not yet certain, but the symptoms of which can be characterised as being potentially dangerous, with a risk of invalidity or death. The risk of potential invalidity is sometimes one which needs careful assessment. For example the decision whether and by which mode a patient is evacuated may differ depending whether a critically injured finger is the fifth or the second one, and whether it is on the patient’s dominant hand.
Every evacuation, whether ship-to-shore, ship-to-ship or ship-to-helicopter is associated with complications related to physical movement from bed to stretcher. Even in the confined surroundings of a hospital such transfers with an immobilised patient are known to be associated with complications. These may range in severity from the pulling out of intravenous lines or dislocation of immobilisation splints to life-threatening ones such as the pulling out of endotracheal tubes or accidents involving the entire stretcher-with-patient during the transfer, while hanging in the air by lines between one craft onto another.
If the patient is suspected of having a disease which may possibly come under the International Health Regulation (WHO) for communicable diseases (implemented July 2007), it is essential for the TMAS doctor to notify all parties concerned, namely the respective RCC and the evacuation organisation. The captain, under these circumstances, is under a legal obligation to notify the Port Authorities of the port he is heading to.
Medical contraindications against evacuation with helicopter
There are no absolute medical contraindications to medical evacuation. Of paramount concerns are the urgency of treatment, the uncertainty of diagnosis, and an estimate of the effects of treatment delay or deferral on the patient's prognosis. Stabilization of the patient prior to evacuation cannot be overemphasized. These principles more than any other influence the final therapeutic outcome. On occasion, it may be prudent to delay evacuation in order to stabilize the patient.
An evacuation by helicopter is associated with a number of physical conditions that may have an adverse effect on the medical condition of the patient to be evacuated. These factors comprise:
Reduced atmospheric pressure
Rescue helicopters that are involved in Medevac operations normally do not have pressurised cabins. The maximum altitude at which they fly, especially on short hauls, is usually less than 2000 metres above sea level. The atmospheric pressure on board during the flight is, however, reduced to some degree. The result of this is that the gases present within the body tend to expand in accordance with Boyle's law. If unable to escape, this pressure may rupture the containing walls of the cavity or impair the circulation inside the wall, causing local hypoxia and possibly subsequent necrosis. It is good custom to inflate the cuff of an endotracheal tube with saline rather than air to prevent rupture due to relative over-pressure, the same goes for the balloon of a urinary catheter.
The use of inflatable splints poses similar problems. The relative over-pressure inside the splint will increase, resulting in a tourniquet-effect. There is a well-documented incident in which MAST trousers were used to stabilize a wounded patient. After the flight, the patient's feet were pulseless which ultimately lead to bilateral lower extremity amputations.
Special consideration to this must be taken in cases of suspected (tension) pneumothorax. If the condition can be diagnosed by the helicopter doctor, it is evidently wise to relieve the pressure beforehand by a thoracic drain.
Large unreduced hernias, volvulus, intussusception, and ileus are particularly susceptible to trapped gas phenomena. The circulation of the involved bowel loop may be severely compromised from trapped gas expansion. Insertion of a nasogastric tube may be good precaution.
In cases involving trauma in the oro-facial region, oedema of the nasopharynx may trap the air confined in the sinuses causing pain during the flight. Administration of nasal decongestants may be a sensible precaution to take.
In cases involving a skull fracture, air trapping may also be a factor to take into account. If air has entered the cranial cavity, aeromedical evacuation must be accomplished at cabin altitudes maintained at as near sea level as possible. This is also the case in trauma cases where an intracerebral haemorrhage or cerebral oedema may present.
This reduced pressure is also of marked importance in patients with caisson disease/decompression sickness after diving accidents: if the level of decompression is already a problem at sea level will be even more so with the reduced atmospheric pressure inside a helicopter.
Decreased oxygen tension
The decreased oxygen tension associated with reduced atmospheric pressure may also have significant adverse effects. Oxygen saturation is decreased only slightly in unpressurized aircraft flying below 2000m. However, this reduction can be relevant in patients with whom tissue oxygenation at sea level was already critical. Patients at risk include those with anaemia, often because of recent acute blood loss, impaired pulmonary function, cardiac failure and instable angina pectoris. This factor can normally be compensated by administering extra low-flow oxygen from a pressurised tank; the readings from a portable oxygen saturation meter serving as guideline.
Especially in bad weather, motion sickness can affect anyone, but the implications in a critically ill patient can be important. The incidence is high in helicopter flights and also in evacuations by smaller vessels. The vagal effect on a critical circulation is not in the best interests of the patient. In many conditions where the upper gastrointestinal tract is involved, the extra strain of vomiting can have adverse consequences on the patient’s condition. Examples of these are suspected or overtly bleeding gastric or duodenal ulcers, injuries involving the abdominal or thoracic wall or of the orofacial area such as a mandibular fracture. In the latter, the risk of aspiration must be taken into account, especially if the mandibular fracture has been immobilised by a bandage or a wire.
Administration of antihistamines (25 to 50 mg of meclizine, 50 mg of cyclizine or 50 mg of dimenhydrinate) or "scopoderm" (0.6 mg of scopolamine mg[jc1] of d-amphetamine) prior to the flight may reduce these symptoms if not medically contraindicated. Because these medications need time to take its effect, administration may be advised by the TMAS doctor before the arrival of the evacuation crew.
The relative humidity at altitude is also reduced. Dehydration may represent a risk to the unconscious, marginally hydrated patient. Patients with tracheostomies or those who must breathe through their mouths may require humidified air or oxygen to prevent drying of respiratory secretions. Corneal drying in comatose patients may be averted by holding their eyelids closed by adhesive tape.
Special care must be taken when evacuating psychiatric patients who risk becoming uncooperative or even violent during the evacuation process. It may in some instances be a safe precaution to have them strapped in a litter and/or sedated during the flight.
Costs involved in an evacuation
Although not of prime importance assuming the indication of an evacuation is sound, it is still wise to keep in mind that a medical evacuation can involve costs in the order of tens of thousands of dollars. Very often the costs of the evacuation and patient transport are considered running costs of the respective navy or other state-run organization conducting the evacuation.
A captain requesting a medical evacuation will primarily have the patient’s benefits in view. But one must keep in mind that other interests may also influence his request; not in the least can commercial or financial motives play a role in the matter. For a fishing vessel, having to bring the patient to a port even nearby, implies that they will have to suspend their fishing activities for a while and will also make them encounter other costs such as fuel, harbour dues etc. A passenger ferry, if it needs to return to port to offload a patient, will cause all the passengers, trucks with merchandise etc. a delay of hours, thus having important consequences for many parties involved and not in the least the reputation of the shipping line. Some shipping companies may have chosen to insure themselves against these costs; many consider these as part of the overall running costs of the company, similar to a delay due to bad weather.
In making the decision as to which mode of evacuation is chosen, one must keep in mind that there may be financial motives for the captain to urge for medical evacuation by a third party instead of delivering the patient by their vessel although the latter may, medically speaking, be the safest and preferable option. It can sometimes imply that the severity of the case such as reported by the officers may to some extent be over-estimated or reported as such, so as to force the decision toward evacuation by a third party.
Preparing for transport
It is important that all relevant information should be collected and accompany the patient, preferably in a plastic sealing or envelope. It is essential that these comprise:
- passport, seaman’s book, vaccination book
- Medical Reports. This should include minimally:
- details of onset of illness or injury
- description of medical findings and a log of the development of these in the course of lapsed time, especially concerning the vital
- signs as blood pressure, breathing frequency, Glasgow Coma Scale etc.
- Therapeutic measures taken, especially which medication was administered? (morphine!)
- All correspondence with a TMAS or with doctors in previous ports concerning the patient should be printed and included.
- Personal belongings as the patient is unlikely to immediately return to the vessel. If practicable and time permitting, his suitcase and personal effects should be packed and sent along with him.