AEROMEDICAL EVACUATIONConsiderations for providing exceptionalcare in unusual places

Dr Wilfred Lim MBBS, MMed(Anaes), DAvMed(UK), FAMS, FANZCA, FACAsM

Aviation Medicine Physician and Anaesthetist

Aeromedical Transfer Systems

On Scene Primary Facility Tertiary Hosp. Home / Rehab

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- HEMS / SAR- Specialist Trauma Teams

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- HEMS- Air Ambulances

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- Air Ambulances- Commercial Airline

On Scene Primary Facility Tertiary Hosp. Home / Rehab

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Unstable

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Aeromedical Transfer Systems

- HEMS / SAR- Specialist Trauma Teams

- HEMS- Air Ambulances - Air Ambulances

- Commercial Airline

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Outcomes & Benefits

HEMS improve outcomes in major traumaGalvagno. JAMA. 2012;307(15), Stewart. Acad Emerg Med. 2011;18(11)

Benefits to non-trauma Access to definitive therapy for STEMI　

C. Grines. Air PAMI Trial JACC, 2002 39(11)

Stroke -- “time is brain” Combat casualty care

Benefit of delivering more advanced, time-sensitive treatments to critical trauma patients during transport Morrison. Ann Surg. 2013;257(2)

Cost effectiveness HEMS must provide 15% RRR in mortality in order to offset

higher costs, transport risks and over-triage Delgardo. Ann Emerg Med. 2013;62(4)

Indications

Local facility inadequate Air transfer is indicated if reduction in response time is

medically indicated Distance covered is over 150 miles (240 km) Remote areas - when no other means of transfer is practicable Enable early initiation of management by trained medical staff and

special equipment

Conditions Major trauma STEMIs Acute stroke Neurosurgical emergencies Obstetric emergencies ……

ContraindicationsAbsolute Unsafe flying conditions, as determined by

pilot Combative or uncontrollable status of the

patient (i.e., a risk to aircraft or crew)

Relative Terminal condition of the patient Acute infection or contamination in

communicable phase of illness Cardiopulmonary arrest of the patient Pneumothorax, unless reduced by chest tube

with Heimlich valve in place Decompression sickness Arterial gas embolism Bowel obstruction from any source

(commonly postoperative) Unreduced incarcerated hernia Volvulus Intussusception Laparotomy or thoracotomy within previous 7

days Presence of intracranial air

Relative (con’t) Eye surgery within previous 7–14 days Gas gangrene Hemorrhagic cerebrovascular accident within

previous 7 days Severe uncorrected anemia (hemoglobin <7.0

g/ml) Acute blood loss with hematocrit below 30% Uncontrolled dysrhythmia Irreversible myocardial infarction Congestive heart failure with acute pulmonary

edema Acute phase of chronic obstructive pulmonary

disease Acute asthma exacerbation Acute psychosis Delirium Spinal injury unless immobilized Pregnancy with imminent delivery

In deciding a patient for an aeromedical transfer, consider:

4

1

3

• Local facility inadequate to treat condition AND

• Patient fit for air transfer

• Local facility is inadequate to stabilise condition AND

• Condition will greatly benefit from treatment at destination

• Local facility adequate to stabilise patient AND

• Condition may benefit if treated at destination AND

• Aeromedical team capability matches local level of care or more

No

In deciding a patient for an aeromedical transfer, consider:Patient condition1 Local medical facility capability2 Benefits at destination3 Capability of aeromedical team4

StablePatient?

Large Distanceto facility

YES AeromedicalEvacuation

Decision forAeromedicalEvacuation

Large Distanceto facility

YESAeromedicalEvacuation

• Benefits of aeromedical transfer is uncertain.

• Risks and benefits of the transfer will need to be deliberated carefully

• Plan should be consistent with the goals of the patient.

Yes No

EMERGENCY, NO on-scene medical care

Use most expeditious mode

YESAeromedical or Surface

Evacuation

No

• Aeromedical transfer may not benefit patient

• Continue treatment at local facility• Re-evaluate when conditions

changesNo

No

No

Large Distanceto facility

YES AeromedicalEvacuation

Yes

2

Flight Environment Clinical / Physiological Issues ambient pressures (~570 mmHg or 0.75 atm)

• PaO2 – 55 mmHg ; SaO2 88-90%• Limits maximum PO2 delivery

Flight Environment and Physiology

Gaseous expansion • Trapped gas cavities• Post surgical trapped air• Equipment – LMA/ETT cuffs, intra-aortic balloon,

drug/fluid containers, pressure bags

Acceleration & vibration • Motion sickness• muscle stimulation, metabolic rate, pain over

fracture sites• Haemodynamic effects

Temperature & humidity • Body temperature control• Drying of airways and burnt skin

Noisy, isolated & cramp • Poor access to patient• Degraded monitoring• No access to further intervention

Flight Environment and Physiology

Inflight Clinical Pearls

Lower threshold to secure airway

Compensate FiO2 If patient requires >0.75 FiO2 at sea level, not possible to deliver

equivalent PiO2 at cabin altitude of 8000ft

Cabin Altitude Restriction (CAR) if high FiO2 requirement Cabin pressure will be maintained at sea level Impact on fuel consumption and cruising altitude and range

Decreased humidity secretions are thicker Humidified gases

Source : USAF AFI-41-307 : Aeromedical Evacuation Patient Considerations and Standards of Care.

Inflight Clinical Pearls

• Will be difficult to oxygenate in-flight

• Optimise before transfer• Cabin altitude restriction• Transfer with lung assist device

Even after taking into account correction for hypobaric conditions, may still rquire higher FiO2 due to:• Increased stimulation• Increased V/Q mismatch

(supine, haemodynamic instability)

• Loss of recruitment secondary to multiple disconnection

• Transport ventilator mode

Conversion table for in-flight FiO2 administration

Compensate FiO2

Inflight Clinical Pearls

Shock patients tolerate transport poorly Monitoring

NIBP prone to interference by vibration. Invasive lines - re-zero after ascend and descend

(760 vs 565 mmHg = 265 cmH2O difference!)

Defibrillation Defibrillation pads safer and should be used or placed prior to transfer Interference to communications

Intra-aortic Balloon Pump Balloon volume can increase by 25 to 62.5%. Pressure should be

equalised frequently (every 1000 feet ascent/decent)

Inflight Clinical Pearls Traumatic Head Injury

Preferably to avoid during 3-5 days post-injury due to peak brain oedema

Neurological Monitoring Increased requirement for

sedation Low threshold for ICP monitoring

(no access to CT) Pneumocranium

Case Series (Donovan et al) n=21, 0.6-42.7mL intracranial air:Nil sequelae

CSF leak & EVDs will drain slightly faster at altitude

High-risk or unknown infective pathogens Requires negative pressure HEPA-filtered

transport isolator with gloved ports Crew protection : coveralls, positive pressure

respirators, hoods and prophylaxis Reduced access for monitoring and intervention

Inflight Clinical Pearls

Platform Considerations

“If you are in trouble anywhere in the world, an

airplane can fly over and drop flowers, but a helicopter can

land and save your life.”

— Igor Sikorsky

Platform Considerations Flight – load, range, speed, buffeting,

instruments, all-weather, hovering, air-strip requirements

Aeromedical ergonomics – loading (doors vs ramp), work-space, lighting, electrical power, oxygen supply

Others – environmental control, cabin pressurisation, rapid start-up (HEMS)

Safety – flight profile, co-pilot, weather, survivability

Equipment Considerations

Requires flight engineering authority certification for safety & compatibility

Equipment mounting – crash survivability

Aircraft electrical power Not directly compatible Battery endurance - specifications

usually overestimates

Oxygen Supply Aviation certified oxygen tanks

(green) Alternatives – molecular sieve

oxygen concentrators (low flow) Take along 2x amount calculated!

Preparation and Planning - Checklist Meticulous stabilisation prior to transfer Full history and thorough evaluation

Complete trauma survey Request investigations if indicated Upgrade monitoring if indicated Photograph wounds/skin condition

Informed consent from the patient or a representative

Ensure critical infusions are topped up Check equipment Calculate electrical power and oxygen

requirements. Secure all lines, tubes, and equipment Bivalve fresh casts Remove or deflate air splints Re-check air-filled balloons or fill with

noncompressible fluid (water)

Collect passports and visas for the patient, escort, and evacuation team

Orient the patient (or escort) to emergency egress procedures

Reserve ground ambulance for departure and destination airports

Ensure that lift crews are available at both airports

Ensure that a hospital bed and physician are available at the receiving hospital

Pack all medical records, radiographs, and care documents

Review altitude restrictions (if any) with flight crew

Discuss contingency plans, including diversion options, with flight crew

Take warm clothing, mobile phone, food, money

Last Slide - Medical Flight Crew

Air transfers can be hazardous for both the critically ill patient and inexperienced transfer crew

Areas for training emphasis Flight physiology, monitoring,

resuscitation, stabilisation & optimisation

Airmanship & crew resource management

Survival

Simulation training - great potential Safe, controlled context and

environment High fidelity – environmental stressors

and patient simulators