Aeromedical Evacuation

MAJ Tom Garigan

Fort Benning, Georgia

October 1997

Outline:

• Capabilities of Ground and Air Transport
• Medical Considerations
• Determining the Mode of Transport
• Preparing for Transport
• Reference Information

Types of Transport

• Ground Ambulance
• Fixed Wing
• Rotary Wing

Ground Evac Advantages:

• door-to-door
• can stop
• can divert
• few weather restrictions
• affordability
• availability
• accidents less serious
• better internal lighting than UH-60

Ground Evac Disadvantages

• motion sickness
• rocking due to high center of gravity
• accelerations and decelerations
• traffic/tactical situation
• higher accident rate than aircraft
• noise, vibration 69-75 dB (ICU: 58-70dB)
• monitoring limitations
• supply limitations

Helicopter Evac Advantages

• Faster transport: 1/2 to 1/3 that of ground
• Avoid road problems
• Smoother trip
• Lower accident rate
• Long-range communications
• More patients
• Specialized transport teams

Helicopter Evac Disadvantages

• Require LZ
• Cramped workspace
• Motion sickness
• Weather limitations
• Effects of altitude
• Crew Fatigue is greater risk
• Effects on equipment:
  • vibration
  • altitude
  • electrical problems
• Cost
  • $1.5+ million/year per aircraft
  • per 100 miles (1991)= $2000
• Range limits: 150-400 miles
• Over-evacuation: too far to rear

Fixed Wing Evac Advantages

• Speed
• Distance
• Larger Cabin Area
• Fly above weather
• Cabin Pressurization @8000 feet
• More medical team members

Fixed Wing Evac Disadvantages

• Airport needed
• Transfer between modes of transport
• Time to mobilize
• Effects of altitude
• Costs
• Equipment limitations

Time of Trip is determined by more than Speed of Vehicle

• time to mobilize transport team
• alert
• flight plan
• ground run-up
• time for team to get patient
• transport to LZ/airstrip
• transferring patient from vehicle to aircraft
• time spent in stabilization for transport
• distance and weather from LZ to MTF
• number of transfers (ground-->air-->ground)

Air Evac When:

• "the speed of transport, skill of the medical team, and/or ability of the [aircraft] to overcome environmental obstacles is likely to contribute to an improved patient outcome."

Physiologic Effects of Transport

• Hypoxia
• Dysbarism
• Humidity
• Acceleration
• Vibration
• Noise
• Cold
• Third-spacing

Hypoxia

• Minimal issue for < 1500 feet
• Cabin pressures (enclosed aircraft)
  • usually < 8000 feet
  • depressurization may be fatal
• Patient's functional level, and DLCO may not be a good predictor of patient's change in PaO2 with altitude

Dysbarism

• Sea Level: 1 liter
• 3000 meters: 1.5 liters
• 9600 meters: 3.0 liters
• Gas expansion in body spaces may be life-threatening

Acceleration

• May cause blood pooling
• Esp. during takeoff and landing

Humidity

• Decreases with altitude
• Drying of:
  • mucus membranes
  • skin
  • eyes
  • bronchopulmonary surfaces

Vibration

• Stress and fatigue on:
  • patient
  • staff
• Fracture displacement
• Bleeding from wounds
• Effects on equipment
• Loosen attachments

Noise

• Crew and patient stress
• Interferes with vital signs and physical exam

Cold

• Temp drops with altitude
• Endangers neonates, infants

Third-Spacing

• Lower ambient pressure: Leakage of fluid from intra-vascular to extra-vascular space:
• edema
• dehydration
• hypovolemia

Considerations, by Organ System

• Cardiovascular
• Pulmonary
• CNS
• Gastrointestinal
• Genitourinary
• Orthopedic

Cardiovascular: Issues

• Hypoxia:
  • ischemia, cardiac failure, shock
• Don't fly > 8000 feet
• No apparent hemorrhage risk after thrombolytics
• Activity-sensing Pacemaker malfunction

Cardiovascular: Management

• Hypovolemia:
  • transport feet first in fixed-wing aircraft due to negative G-forces
• Warm IV fluids
• Bring monitors, defibrillators
• Watch for constricting clothing
• Magnet over activity-sensing pacemaker

Pulmonary: Issues

• Gas expansion:
• Pneumothorax
• Endotracheal tubes
• Hypoxia
• Neonates
• Monitoring difficult
• cyanosis, pallor, breath sounds

Pulmonary: Management

• Proper lighting
• Pulse oximeters
• Oxygen, humidified
• Fill ET tube cuffs with water
• Suction device
• Chest tubes with Heimlich valves/drainage collection
• Bring X-Rays
• Altitude Restrictions

CNS: Issues

• Hypoxia:----> cerebral vasodilation
• Vibration----> aggravate injury of spine, brain
• Intracranial air---> expansion
  • absolute contraindication?

CNS: Management

• R/O intracranial air
• elevate head to 30 degrees
• immobilize
• pre-plan for airway management
• hyperventilate
• head first to prevent excess blood flow to brain

Gastrointestinal: Issues

• Trapped air:
  • hernia, ileus, volvulus, post-op, obstruction
• weakened viscus:
  • surgery, diverticulitis, ulcer, inflammation

Gastrointestinal: Management

• NG Tubes
• to suction, or unclamped
• Extra colostomy bags

Genitourinary: Issues:

• Expansion of gas in FFoley or collection systems
• Expansion of intestinal gas---> pressure on bladder---> incontinence
• Difficulties voiding when supine

Genitourinary: Management:

• Fill Foley balloons with water
• Vent collection systems
• Foley or Texas catheters

Orthopedic: Issues

• Motion: may displace fractures
• Extremity Swelling

Orthopedic: Management

• Bivalve casts
• NO Air casts!
• Spring tension traction instead of weights

Hematologic

• Hgb < 7 is relative contraindication:
  • Transfuse to 10 mg/dL
• Sickle Cell: may have crisis as low as 4000 ft:
  • O2 is mandatory

Ophthalmologic:

• Air trapped in eye from surgery or trauma:
  • increase intraocular pressure
• herniation of globe contents
• Ocular hypoxia
  • increase intraocular pressure
• pupillary constriction
• retinal vasodilation----> hemorrhage

Ophthalmologic: Management

• Fly < 5000 feet altitude
• Oxygen for > 4000 feet
• Eye lubricants
• Keep supine
• Morphine may constrict pupil---> harmful post-op or post-trauma

Maxillofacial: Issues

• Barosinusitis
• Barotitis
• If jaws are wired:
• bring wire cutters
• place patient on side, head down
• tracheotomy/cricothyrotomy capability

Burns: Issues

• Hydrate prior to transport
• Maintain urinary output
• NG Tube (1/4 of burn patients get ileus)
• Dress burns
• Full pulmonary assessment before flight
• Risk of compartment syndrome

OB: Issues

• Hypoxia:
  • Uterine irritability
• Fetal pO2 at 10,000 feet:
  • 29.3 ---> 23.6
  • Partial compensation for 30 minutes
• Fetal outcomes by air evac to tertiary care center:
  • Same as with conventional evac
• Specialized Transport Teams:
  • Anticipate need

Pediatrics: Issues

• Children = 7% of all patients needing evac within 24 hrs.
• Specialized transport teams at tertiary centers
• For one-way transport:
  • Incubator
  • Pediatric medications & supplies
  • VS & monitoring capability
  • Warming capability

Relative Contraindications to Air Transport

• Pneumothorax within 72 hrs except if chest tube in place
• Tracheostomy unless humidified O2 in place
• Severe Anemia, Hgb < 7, Hct < 21
• Sickle Cell Disease
• Recent Acute Blood Loss: Hct < 30
• Active Hematemesis
• MI in past 10 days, or complications in past 5 days
• Uncontrolled dysrhythmia
• Pacemaker (must be prepared to adjust en route)
• Eye surgery or trauma (keep < 1500 feet)
• CVA within 7 days
• Intracranial air
• Spinal injury unless Stryker frame
• Upper/lower jaw immobilization (have quick release)
• Beyond 34th week of pregnancy unless medically necessary
• Infectious stage of serious communicable disease or fever > 39.4 without known source
• Circumferential casts (bivalve)
• General surgery within 5 days
• Unlikely to survive the flight due to terminal illness or mortal injury

Determining the Mode of Transport:

• Assess the Medical Needs of the Patient
• Assess the Options for Transport

Assess the Medical Needs

• Diagnoses
• Level of care needed vs. available
• Urgency: Time to referral hospital
• Access to emergency rx en route
• Special equipment needed for transport
• Will the transport worsen the patient's condition?

Assess the Modes of Transport

• Speed
• Capabilities
• Skill of medical crew/quality of care in-flight
• Physiologic effects
• Safety/Risks
• Route/access to fixed facilities en route

After Choosing Mode of Evac:

• Brief Crew on:
  • Urgency & Time Constraints
  • Altitude Restriction
• Medications and supplies
  • including Oxygen
• Monitoring needs
• Accompanying Personnel
• Prepare the Patient
  • Stabilize
• Physician orders for:
  • monitors
  • supportive and emergency rx
  • accompanying personnel
  • what to do if patient's condition worsens
• Secure the patient
• Medical records, X-Rays, labs
• Consent

Preparing the Aircraft

• Accessories
• litter straps, clamps, flashlights, earplugs
• Security
• Loose items secured
• Communication with Cockpit

Equipment Problems

• electromagnetic

• all US Govt items are tested

• vibration
• air in IV bags, tubing, equipment
• noise
  • dopplers
  • stethoscopes
• risk of interference with aircraft systems
• Potential incompatibility
  • Among services, nations, civilian and military evac systems :
    • Training
    • Supply/Equipment
    • Communications
    • Patient Tracking

Medical Equipment Airworthiness Testing

• Ft. Rucker
• Brooks AFB
  • Armstrong Lab
  • www.al.wpafb.af.mil/cf-proj.htm
  • heat/cold/altitude/humidity/EMI/electrical safety/vibration/rapid decompression/actual flight testing

Responsibilities of the Receiving Institution:

• Credentials of receiving medical staff
• If sending a transport team:
  • Appropriate equipment
  • Specialized training in flight physiology and air transport
  • Treatment protocols

Air Force: Review of Evac, CONUS 1993- problems occuring during evac are generally due to pressure changes, and hypoxia:

• Lack of O2 ordered
• Lack of altitude restriction
• Lack of physician documentation of care required
• No records or summary
• Attendant skills must match patient needs
• Accomplish procedures pre-flight

USAF Problem Patients:

• Infectious Disease
• Unlikely to survive flight
• Terminally ill, unless accompanied by a physician
• Acute Anemia
• Sickle Cell Crisis
• MI within 10 days, or complicated; unless accompanied by a physician
• PTX < 24 hrs off tube, or < 72 hrs spont. resolution

IF PATIENT DIES IN FLIGHT--> PLANE LANDS

Some Reference Information:

• Aircraft Capacities
• Loading of Aircraft
• Categories of Precedence
• Army MEDEVAC Request

Rotary Wing Evac

• UH-60 (Blackhawk)
  • normal: 4 litter, 1 ambulatory
  • max: 6 litter, 1 ambulatory
  • or: 7 ambulatory
• UH-60 with Rescue Hoist
  • 3-4 litter, 1 ambulatory
  • or: 4 ambulatory
• UH-60Q
  • "Off-the-shelf" technology
  • litter supports mounted on sidewalls
  • lighting
  • medical suction
  • molecular sieve O2 generator
    • 24 L/minute, of 94% O2
• UH-1H ("Huey")
  • normal: 3 litter, 4 ambulatory
  • max: 6 litter
  • or: 9 ambulatory
• CH-47 Chinook
  • 24 Litter
  • or 31 Ambulatory
• CH-53
  • 12 litter

Fixed Wing Evac- US Army:

• U-21 Ute
  • 10 ambulatory
  • or 3 litter, and 3 ambulatory
• C-12 Huron
  • 8 ambulatory
  • or 2 litter, 4 ambulatory

Fixed Wing Evac- US Air Force:

• C-9A Nightingale= DC-9
  • dedicated MEDEVAC aircraft
  • Sea level cabin pressurization to 18,340 feet
  • 40 litter or 40 ambulatory
• C-130
  • 50 litter & 27 ambulatory
  • or 74 litter
  • or 92 ambulatory
  • Sea level cabin to 19,500 feet
  • some models only 11,900 feet
• C-141 Starlifter
  • 103 litter
  • or 168 ambulatory
  • combination of both
  • Sea level cabin to 21,500 feet
• C-5 Galaxy
  • 70 ambulatory in aft passenger compartment
  • C-17A
  • 44 litter, 48 ambulatory, 10 medical personnel

Items commonly available on USAF medevac- peacetime

• humidified O2
• suction
• Collins traction
• backrests
• limited medical tools
• AMBU bag with masks
• laryngoscopes
• needles, syringes

Items available on USAF medevac- on request (peacetime)

• infant incubator
• oxygen analyzer
• cardiac monitor/defib
• ventilator
• hypothermia blanket
• croup tent
• IV infusion pump

Items provided by sender: (3-5 day supply)

• Meds
• IV's
• Hyperal
• Special diets
• Dressings

Civil Reserve Air Fleet (CRAF)

• Boeing 767 conversion kits
  • > 60 total expected
  • Conversion within 24 hrs of notification
  • 87 (short) or 111 (long) litters
  • 2-4 flight nurses plus 6 aeromedical technicians
  • 75 oxygen sources, 12 hr. capacity
• MD-80
  • 45 litters
  • 2 nurses, 3 techs

Loading Plan for Large Aircraft

• Place injured limb towards middle
• Sitting/Semi-prone position requires 2 litter spaces
• Male/Female privacy
• Middle tier is more accessible for care
• Patients needing assistance: near exit
• Neuropsych cases under observation
• TB & other communicable diseases: in rear
• Agitated/altered consciousness: bottom tiers
• Cough, airsickness: bottom tier; with ventilation

Loading Plan for UH-60

• Critically Ill: Bottom tier
  • for treatment
  • for first off-loading
• If requiring in-flight care: top tier (in 4-litter configuration)
• IV patients: any tier
• Hare traction splints: bottom tier

Loading Plan for UH-1H

• Critically Ill: Bottom

• for treatment
• for first off-loading

• IV patients: Bottom
• Hare traction splints: load on floor of aircraft

Army Medevac Request

• Line 1-Location of pickup site (6 digit grid)
• Line 2- Radio frequency, call sign, suffix
• Line 3- Number of patients, by precedence
• Line 4- Special equipment required (hoist, penetrator, special litter)
• Line 5- Number of patients by type (litter, ambulatory)
• Line 6- Wartime: Security of pickup zone (enemy- none, possible, present) Peacetime: type of injury or illness
• Line 7- Method of marking pickup site
• Line 8- Patient's nationality & status (US? Military? EPW?)
• Line 9- Wartime: NBC Contamination Peacetime: Terrain description at pickup site

LZ

• > 30 feet diameter
• Slope < 15 degrees
• Mark obstacles with red panels or lights
• Obstacle height clearance ratio 10:1

Priorities of Evac: Army:

• Urgent: evac within 2 hrs to save life, limb, eye
• Urgent-Surgical: require immediate surgery
• Priority: decline after 4 hrs
• Routine: no decline in 24 hrs

Priorities of Evac: Air Force:

• Urgent: divert aircraft, or launch aircraft on alert
• Priority: Pickup within 24 hours
• Routine: Pickup within 72 hours; may be in transport for 3-5 days.

Air Force Medical Regulating Offices

• CONUS- Scott AFB, IL
• Pacific- Yokota AFB, Japan
• Europe- Rhein-Main AFB, Germany

Return to the top of the page