All of us know what MEDEVAC is, especially, how it is carried out in our own country. However, complications are always in ambush. Let us read what Italian 112 and 118 organizations issued some days ago on how to treat complications during an air ambulance delivery.

Treating a critical patient on an aircraft is absolutely difficult and requires well-prepared practitioners. In Italy, the EMS organizations of 118 and 112 issued a paper on the various complications which can occur during MEDEVAC and how to behave in case (at the end of the article the authors).

Compared to the HEMS or SAR, when MEDEVAC – medical evacuation or transport – is carried out with a fixed-wing aircraft and underlines the combination of a ground vehicle and an air ambulance aircraft. This is quite different from HEMS, for example. Firstly because it is provided with a rotating-wing aircraft (helicopter) and secondly, it can provide care from the precise point where the patient is localized and delivery him/her to the more suitable medical facility.

When do the fixed-wings MEDEVAC deliveries are provided? When the secondary long-distance transfer of more or less critical patients, primary long-distance intervention on patients located in isolated areas and in case of organs transport or healthcare teams for clinical needs in far locationsì.

In particular, during a MEDEVAC delivery, the patient is often critical, which requires more attention. Guido Villa, Marco Botteri and Roberta Boni issued for 118 AREU, Emergenza 112 and Italian national organization 118 a paper on 12 June 2020 that highlights the complications and the resolutions.

 

Nasal intubation, the problems that could occur during a flight

Prolonged nasal intubation can provoke major problems for a transported patient in MEDEVAC. The main issue comes from the pain that altitude changes can cause. Essential is to keep checking the patient’s vital signs, in particular, if the patient cannot communicate. It has happened that, during MEDEVAC flight, in extreme cases, some military doctors discharged middle ear pressure using the steel spindle of an 18 G catheter and performing a myringotomy.

However, this kind of procedure involves considerable risk if performed on an unstable aircraft. Normally, it is not recommended. The patient’s loading and unloading manoeuvres are dangerous, while you risk accidental extubation. That’s why a fixation of the endotracheal tube or tracheotomy is only as necessary as the
particular attention during these phases.

An accidental kneeling of the tube or the sudden increase of secretions can obstruct the airways and make the condition even more complicate than this. The practitioner has to find a remedy to the problem very quickly and competently. It is suggested to check the cuff pressure of intubated patients during MEDEVAC flight. Its variations could influence in this very particular environment.

 

Airway problems during MEDEVAC flights: how to manage them?

They are the most complex ones to manage in MEDEVAC flights. Generally, they can be linked to the flight altitude, or to the availability of supplementary oxygen (more information in another paragraph below).

Oxygen can be administered both by a non-invasive method or directly by artificial ventilation in closed circuit. The real contraindication to the flight remains the undrained pneumothorax before take-off, for the severe risk of hypertension during direct flight. In doubtful cases, it is appropriate to be able to maintain in the correct pressurization in the cabin, i.e. no more than 2500 feet. It corresponds to a much lower flight altitude, which results in lower speed and higher flight fuel consumption.

In already artificially ventilated patients, the entire respiratory assistance parameters will have to be calibrated once the cruising altitude is reached, working on the monitoring available (FiO2 – SpO2 – EtCO2 – Vol/min – Pressures reached in the circuit – circulator data). For the rest, it should be added that it is necessary to intubate previously on the ground a patient who also has a medium chance of worsening on the respiratory or neurological side during the flight, in order to not incur more difficult manoeuvres onboard the carrier.

On these subjects, it is also essential to position a filter placed between the pipe and the connection to the fan, for adequate humidification of the airways even for short distances. This would reduce the risks of occlusion of the natural and artificial airways. Sometimes it may be useful to insert an NG tube to avoid stomach dilation at altitude with the associated ventilatory difficulties.

 

Cardiovascular alterations during MEDEVAC

The cardiovascular system can suffer the influence of flying with aircraft during a MEDEVAC delivery. Even in healthy subjects, there is an increase in heart rate, blood pressure, peripheral vasoconstriction and decreased oxygen saturation and tissue exchange. These changes are very slight on healthy subjects, but they can be the first suggestion of more relevant and dangerous negative clinical phenomena in patients with cardiovascular disease.

Therefore, it is appropriate to carefully monitor even patients with low clinical commitment and administering O2 flows in advance that compensate for the decreased availability of oxygen at altitude with reduced tissue oxygenation. It is also important to remember that drop-in infusions are not possible in aircraft, so it is necessary to use pressure bags.

For infusion fluids and/or battery-operated infusion pumps for administering medication. With regard to the problem of PMs or endothoracic ICDs, there are no special reports, while the use of an AED via self-adhesive plates is not contraindicated, but using the usual precautions of the case, in particular by closing the free oxygen supply and always warning the flight crew first.

 

MEDEVAC with trauma and neurological complicate patients

Patients with neurological problems delivered with a MEDEVAC type of transport have to be carefully monitored for their state of consciousness and other elements that include mobility, the risk of epileptic crises and the control of the pain. Given that the coma is not in itself a contraindication on the fly, its depth and the causes of it
symptomatology are extremely relevant in deciding the patient’s condition for flight.

Once it is possible to make up for organ deficiencies due to the inactivation of the CNS, medical transport results to be carried out with the theoretical exception of rapidly evolving injuries, when not checked prior to transportation as well. The true absolute contraindications on the fly remain the severe pneumocephalus (serious risk of expansion of the same in catastrophic consequences) and high intracranial pressure (PIC), which cannot be reduced with the appropriate therapy before departure or uncontrollable during the delivery.

In traumatic cases, and if a suspicious spinal cord injury may be a risk, the most appropriate immobilization can be should be carried out by vacuum mattress with a thin sheet interposed between the patient and the contact surface of the immobilizer. This would prevent any danger and avoids the possible decubitus to which these patients are very susceptible, particularly on long stretches.

The same attention should be paid to all patients who have peripheral neurological diseases, both sensitive and motor. In all the patients described above (and in particular in coma patients) it is always advisable to check the need for of positioning an SNG of adequate caliber, if not already in place, in order to hold the stomach and prevent the possibility of vomiting.

They may consider catheterising the urinary tract for monitoring of diuresis, often a spy of dehydration of the subject and indirectly of functionality homeostatic. For persons at risk of a crisis, it is appropriate to undertake or modulate an appropriate antiepileptic therapy prior to departure to avoid the problems of such crises in flight, often due to the imbalances in the irritating thorns of the transfer situation. Finally, in particular, in full conscience, should always be evaluated before the departure and reassessed during the trip the pain of which is affected the patient, in order to carry out a correct and proper check-up.

 

Other various cases of critical health condition in MEDEVAC deliveries

There are many other cases of patients who might be transported with a MEDEVAC method and among them suffering from other diseases requiring an airborne medical transfer to The following is a description of the essential problems inherent in subjects with polytrauma, with burns, with dysbarism, with abdominal surgical problems or with an ongoing pregnancy.

TRAUMA: in addition to what we said previously and in particular the control of vital functions, they have to pay attention to the proper positioning of the patient on a vacuum mattress. Depending on the ascending of the aircraft, practitioners have to deflate progressively air contained shall be carried out systematically during the flight, for one natural loss of consistency with the ascent of the vector to altitude. Patients with head trauma should preferably go housed on the aircraft stretcher with the head in the direction of the plain’s takeoff, while those with a bad guy pressure control for relative hypovolemia should have the head on the side of the tail of the aircraft. With regard to drainage already present, it is necessary to use the beak valve of flute (Heimlich) for chest drains with sterile bagging and repeated patency checks and of secretion collection with an electric pneumatic suction system. Also for drainage abdominals, no interposed valve, the same care must be taken.

BURNS: same precautions for patients with trauma, the following should be added to the caution of the safe, large-caliber venous route(s) and increased thermal control (monitoring of the possible with endogenous probe) and protection from stress ulcer, frequent in these patients.

DYSBARISM: excluding patients with severe Acute Gas Embolism who have an absolute contraindication to immediate fixed-wing air transport if they have not previously been stabilised or treated in a hyperbaric chamber, who has been found to suffer from Decompression Disease (MDD – that includes 90% of cases of dysbarism) can also be transported in the first few hours if it is intended to be subjected to early treatment in an equipped hyperbaric chamber more than 250 km away from the place of the event, not quickly reachable by other means or by other surface or wing means rotating (preferable).

The therapy to be implemented before and during medical transport includes continuous oxygen therapy at 100% FiO2, infusion of at least 500 ml of Ringer lactate/acetate and/or of Dextran 40, administration of acetylsalicylic acid up to 1 g/day per os or 500 mg e.v. of lysine acetylsalicylate) and hydrocortisone 500 mg e.v. x 4 or dexamethasone 8 mg e.v. repeatable. During the flight the pressurisation altitude should be as low as possible (possibly at sea level) and continued administration of the current therapy; some authors also suggest the use of enoxaparin 4000 U.I. sc.

ABDOMINA SURGERY: the postoperative abdominal surgery patient itself does not have specifics contraindications also to long-distance transfers but it should be remembered that some interventions leave a certain amount of air inside the abdomen so that the expansion of this air trapped at high altitude can cause discomfort and in some cases, real emergency situations that are not easily controlled. Occluded or sub occluded patients who have not yet been operated on can also highlight situations of real difficulty clinic for the severe tension on the walls of the intestinal loops caused by a severe meteorism in strong raise.

In cases of such severe abdominal problems, it is suggested in advance to maintain or increase the descent to a flight altitude of around 22,000 feet for sufficient pressurisation in the cabin to reduce patient symptoms and/or the use of an SNG and a rectal defensive probe.

PREGNANCY: until the 36th week of a regular pregnancy, the stretcher-supported health care transport does not present risks neither for the foetus nor for the pregnant woman; the recommendation concerns the use of a decubitus predominantly left side and the use of pre-emptive graduated elastic stockings. Beyond this period are one or two experienced birth attendants (e.g. Midwife + Anesthesiologist or Neonatologist) and the availability of a special birthing kit, which includes health care facilities for both the mother and the baby than for the unborn child.

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