aeromedical evacuation - providing exceptional care in unusual places
TRANSCRIPT
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
Firs
t res
pond
ers
/ On-
scen
e
- HEMS / SAR- Specialist Trauma Teams
Inte
rfaci
lity
Tran
sfer
- HEMS- Air Ambulances
Rep
atria
tion
Tran
sfer
s
- Air Ambulances- Commercial Airline
On Scene Primary Facility Tertiary Hosp. Home / Rehab
Acu
ity o
f pat
ient
s
Unstable
Stabilising
Stable
Aeromedical Transfer Systems
- HEMS / SAR- Specialist Trauma Teams
- HEMS- Air Ambulances - Air Ambulances
- Commercial Airline
Firs
t res
pond
ers
/ On-
scen
e
Inte
rfaci
lity
Tran
sfer
Rep
atria
tion
Tran
sfer
s
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