Emergency War Surgery NATO Handbook: Part III: General Considerations of Wound Management: Chapter XIII: Aeromedical Evacuation

Special Considerations

United States Department of Defense
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Individual patients, each with his own peculiar problems, will, require special considerations. Scheduling the evacuation, managing the patient in transit, arranging special attendants and equipment, programing rest stops, and determining appropriate destination hospitals are all vital considerations in the safe, rapid movement of the battle casualties.

Although the exigency of a given situation may require a patient to be evacuated earlier and for longer distances than ordinarily would be deemed advisable, the rule should be to await adequate clinical stability prior to subjecting the patient to what could turn out to be an arduous, clinically risky, prolonged trip.

1. Tracheostomy care: Tubes should be of proper size. When mechanical respirators are to be used, cuffed tracheostomy tubes are usually required. Because of the low humidity of the aircraft cabin atmosphere, the use of a humidification device is recommended to avoid the production of dry mucous plugs and to assure proper tracheal care during flight. Humidity levels in the pressurized cabin are around 5-20%. At these levels, insensible losses and drying of the tracheobronchial tree, especially in those with tracheostomy, are considerably increased. The ultrasonic nebulizer is the most efficient apparatus at this time. A heat aerosol nebulizer is probably the second-best apparatus.

   Mucous plugs and encrustations must be removed promptly to avoid respiratory distress and obstruction. The use of tracheostomy tubes that do not have cleaning cannulae should be avoided. Rubber and plastic tracheostomy tubes normally do not have cleaning inner tubes or cannulae, The periodic instillation of 2 ml. of sterile isotonic saline solution into the tracheostomy with prompt aspiration enhances the cleansing of the airway.

   In emergency situations during transit, endotracheal intubation is usually safer and quicker than tracheostomy and is well tolerated by the patient. Prompt use of such tubes usually eliminates the need for tracheostomy. A T-tube, if available, should be attached to the endotracheal tube or tracheostomy tube during evacuation to provide humidity and reduce the likelihood of mucous plugging and encrustation. The balloon of a cuffed tube should be inflated with air, not water.

2. Cranial tongs: Special attention should be paid to the proper seating of the tongs. Traction must be maintained by a closed system, preferably with a spring device such as the Collins' spring. In the absence of a spring device, traction may be maintained by heavy rubber tubing tied to the litter frame. To prevent sudden jerking of the tongs, free hanging weights must not be left attached during flight.
3. Skin traction: Stockinette glued to the skin can be utilized to maintain traction during evacuation. Traction is maintained by rubber tubing interposed between the stockinette and a plasterincorporated wire loop. The surgeon who orders the evacuation of the patient is responsible for removing weights and substituting a self-contained traction device before aeromedical transfer.
4. Chest tubes: Ideally, patients should not be evacuated by air with chest tubes in place, nor should they be evacuated within 72 hours after removal of the tube Absence of pneumothorax must be demonstrated by a chest roentgenogram just before movement. On the other hand, when necessary, chest tubes may be left in position during evacuation but should be equipped with functioning valves, such as the Heimlich valve Pressurization of the aircraft to ground level is desirable if such patients must be moved. Thoracic patients that require assisted ventilation should not be placed in air evacuation channels.
5. Nasogastric tubes: All patients requiring nasogastric suction at ground level should have similar protection during flight. The combination of one's basic medical problems coupled with air swallowing due to anxiety or pain, and the reduced barometric pressure at high altitudes results in hollow viscera gas expansion that can cause complications. Failure to decompress the stomach can result in pain from distention of hollow viscera, dehiscence, and, most significantly, vomiting and aspiration with serious pulmonary complications. Increased abdominal pressure under a restricting body cast can also result in vomiting and aspiration.
6. Plaster casts: When evacuating patients with circular plaster casts, all such casts should be appropriately bivalved before movement. This allows for swelling of soft tissue, permits rapid emergency access to secondary hemorrhage, and may facilitate escape through emergency hatches in the event of an emergency. It is helpful to evacuation chain personnel when casts are labeled. Such inscriptions should include the date and type of injury, the date of surgery and cast application, and a simple sketch of the bone injury.
7. Stryker frame: Such frames may be used for transfers by air. Patients should be turned during travel as ordered by the referring surgeon.
8. Catheter care: Indwelling catheters in use before transfer should be left in place during transfer. Instructions for specific care enroute both at the staging area and aloft should be provided to the medical evacuation teams. Every attempt should be made to maintain urinary output above 1,500 ml per day.
9. Hypothermia blankets: Patients requiring hypothermia blankets before evacuation should have this therapy continue enroute. Equipment is normally available aboard the aircraft to continue such treatment. Convulsions, high fever, and respiratory distress can be expected to develop if this principle is not followed.
10. Circulating blood volume and oxygenation: The hematocrit is not a reliable indicator of the adequacy of circulating blood volume The casualty is most likely to be hypovolemic or hypervolemic during the, first 3-4 days post injury. Homeostatic mechanisms have usually restored the circulating volume to normal after this period. Oxygenation problems at ground level will be increased at higher altitudes. Patients having hematocrits of 30% or below should not be transferred under any but the most urgent situation. If transfer must be accomplished, proper supplies for transfusions should accompany the patient with orders for the use of blood enroute. Measurement Of pO₂ should be used as a criterion of air evacuability in the seriously ill patient. Levels below 60 mm Hg are considered a contraindication to movement. It has been demonstrated that wounded patients can have dangerously low arterial pO₂ at sea level without any clinical indication of hypoxia. One U.S. Air Force casualty study revealed that none of the casualties with an arterial pO₂ of 35-40 mm Hg and normal pH was cyanotic, although some were mildly tachyneic. At this level of pO₂, arterial saturation was approximately 70 %; however, many of these patients did not have enough reduced hemoglobin (5 gm/100 ml) to become cyanotic. This sort of situation at sea level is particularly dangerous in flight. At altitudes of 35,000 feet, the cabin is pressurized down to about 8,000 feet equivalent, or 564 mm Hg. At this pressure, alveolar air pO₂ is about 69 min Hg, or 33% less than sea level. An arterial pO₂ that was 50 at sea level is dangerously low at 8,000 feet.
11. Cerebrospinal leak: A wound draining cerebrospinal fluid at ground level will drain slightly faster at higher altitudes. These wounds are not a contraindication for transfer.
12. Abdominal surgery patients: Experience shows that premature evacuation of casualties shortly after abdominal surgery carries a high morbidity. Patients with wounds and injuries of the abdomen are best retained at the facility in which they have undergone their initial surgical care until complications have been controlled, bowel functions have returned, and the wound is healing. These requirements are seldom met in fewer than seven days.
13. Vascular injuries: Patients with vascular injuries require special attention and immobilization. Casts should be bivalved to provide emergency access to the area. When circumstances permit, primary repair or graft cases should not be transferred for 14 or more days after repair, unless the wound has been closed and is healing without evidence of infection. Patients should have the repair date and type of repair inscribed on the castor dressing.
14. Burns: Burn patients may be transferred at any time during their care; however, as in all severely wounded patients, transfer is unwise until the blood volume has been restored and the patient's condition is stable. The best time for this category of patient to travel is 4-7 days postburn, when diuresis has begun and the complications of fever and infection have not yet presented. Burns greater than 40%, or lesser burns associated with severe injuries, ordinarily should have a surgeon in attendance. Preparation for transfer should include:
    1. Airway assurance by whatever means necessary.
    2. Functioning intravenous pathway.
    3. Adequate urinary output.
    4. Fresh burn dressings.
    5. Immobilization of associated injuries as indicated.
    6. Functioning nasogastric tube if any gastrointestinal dysfunction exists.
    7. Complete medical records, particularly accurate fluid balance sheets.
15. Maxillofacial Injuries: During transportation, these patients should be placed in a semiprone position on the litter. If there are upper respiratory difficulties, or if they are likely to develop during transportation, tracheostomy should be performed before evacuation. If tracheostomy or endotracheal intubation is not performed, the patient with a maxillofacial injury must be evacuated with an attendant especially instructed in the possibilities of respiratory obstruction and in techniques for dealing with it.

    Patients with major maxillofacial wounds require special preparation before evacuation to the intermediate or reconstructive care facility. If possible, infections should be under control, no significant fever should be present, and the patient's general condition should be sufficiently stable to withstand the evacuation. All packing should be removed before evacuation, or specific instructions should accompany the patient concerning location, number, and types of packs with recommendations for time of removal. If intermaxillary fixation has been utilized, the patient should be retained for several days after surgery, taking a liquid diet, and tolerating fixation well before evacuation. If intermaxillary elastics are utilized, some type of pullout cords are indicated. In an alert patient who has a tracheostomy or absence of several anterior teeth, there is little likelihood of aspiration of emesis; therefore, any type of suitable fixation is acceptable.

16. Dressing changes: A patient who has had a debridement of a combat wound is considered to have a clean wound. The dressings should not be changed without good reason except in an operating room at the time of probable delayed primary closure. Contamination of the open wound may occur when the dressing change is conducted under less-than-optimal conditions. Neither the odor nor the staining of a dressing from blood or serum is an indication for a dressing change Dressing changes are indicated only for serious complications, such as bleeding, unusually high fever, increasing pain, or swelling. The decision for a dressing change should be made by a physician.
17. Medications: Certain medications, such as antibiotics, narcotics and analgesics, should have a recorded "stop order" to avoid an undesirable extension of this course of therapy. It is essential that the physician ordering evacuation complete the flight tag accurately to assure antibiotic therapy continuation on schedule or discontinuation as required. Some medications are not normally available in standard supply, and when these are to be continued during patient transfer, an adequate supply must accompany the patient.
18. Medical attendants: Medical attendants, assigned to accompany seriously ill patients, should accompany those patients to the destination hospital. The attendant, in addition to providing clinical services enroute, is a vital link in the continuity of care between medical echelons. This is best accomplished by personally interfacing with the receiving medical officers and providing those clinicians with well-documented and complete medical records.

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