Inter-hospital Aviation Transport of Neonates

By: B Lessing

Reg. Sister / PHPLS / ACLS / FMA / ALS Paramedic

OBJECTIVES OF AERO-MEDICAL TRANSFERS

• To provide the basic understanding around the principles of aviation medicine;

• To appreciate the impact of the stressors of flight on both the practitioner, the patient and the parent; and

• To introduce the principles of in-flight care.

INTRODUCTION

• Aero-medical evacuation is safe for transporting almost any patient

• BUT ... The following conditions must be met:

• WELL-PREPARED, well-trained medical escort / team

• Medical EQUIPMENT that is qualified as “safe for use”

• A therapeutic dose of pessimism!

THE STRESSORS OF FLIGHT

• Hypoxia

• Barometric pressure and gas expansion

• Gravitational forces

• Thermal changes

• Noise and vibration

HYPOXIA

Hypoxia in aviation is a syndrome that is usually acute and results from inadequate oxygenation of the tissues secondary to a decreased partial pressure of oxygen in the inspired air– Four types of hypoxia:

• Hypoxic hypoxia• Anaemic hypoxia• Histotoxic hypoxia• Stagnant hypoxia

BAROMETRIC PRESSUREGAS LAWS:• Boyle’s Law (Pressure varies inversely with volume): This law

can affect things like: chest drains, catheters, ETT, pneumothorax, gastric distension, ileus hernia, necrotizing enterocolitis (NEC – can rupture into the peritoneal cavity). These patients should be flown at lowest cabin pressures possible

• Charles’ Law (Pressure constant; temperature varies directly with volume): Cabin pressures and the patients temperature can may influence the volume of trapped gases. Also and increase or decrease in temperature can move the oxygen disassociation curve to the left or right thereby affecting oxygenation of cells. Therefore it is vital that the incubator is fully functional and maintains the correct homeostatic environment.

• Gay Lussac’s Law (Volume constant. Temperature varies directly with pressure)

• Dalton’s Law: (Total barometric pressure is equal to the sum of the partial pressure of each gas)

GRAVITATIONAL FORCES

PROBLEMS UNDER G-FORCE• Cardiovascular Effects: Black out / LOC /

Convulsions / Amnesia / Confusion / Cardiac dysrhythmias / Tachycardia / Bradycardia / Heart block / Any cardiac defects e.g. PDA, ASD and VSD

• Respiratory Effects: Altered VQ ratios e.g. HMD, Meconium aspiration / Airway closure and Atelactasis

• Renal System Effects: Decreased renal blood flow / Oligouria / Increased plasma levels

• Musculoskeletal Effects: Back, neck and limb problems / Inter-vertebral disk rupture

THERMAL CHANGES

• Heat and cold: (differences in temperature from one area to another)

• Altitude: ( higher altitude – colder)

• Immuno-compromised: patient exposed to weather and climate conditions and variations

HEAT LOSS PREVENTION IN NEONATES

• Maintaining a neutral thermal environment is one of the key physiological challenges a newborn infant faces after delivery.

• Thermal regulation is distinctly different in newborns than in adults. In adults, the responses to a cold body temperature include peripheral vascular constriction, inhibition of sweating, voluntary muscle movements, involuntary muscle movements (shivering) and nonshivering thermogenisis. Neonates do not exhibit many of these responsis

• Nonshivering thermogenisis is the main mechanism of heat production in neonates. Nonshivering thermogenisis occurs due to an increase in sympathetic activity leading to an increase in norepinephrine and thyroid-stimulating hormone. Thyroid-stimulating hormone leads to an increase in T3 and T4. These mediators cause increased fat oxidation and heat production. This represents a large caloric demand. A newborn infant left unattended in a room at room temperature experiences energy losses of approximately 140kcal per min.

HYPOTHERMIA

• Infants exposed to cold temperatures are at risk for increased mortality

• Normal temperature ranges for the neonate is 36.5 to 37.7˚C

• Cold stress may occur when temperature drops to 36˚C

• Temperatures below 36˚C are considered hypothermic

• Moderate hypothermia is considered to be between 32 and 36˚C.

• Severe hypothermia is considered when the infant’s temperature is less than 32˚C.

PATHOPHYSIOLOGY OF HYPOTHERMIA

• Hypothermia results in a variety of physiologic stresses. • The infant has increased oxygen consumption, metabolic

acidosis, hypoglycaemia, decreased cardiac output and increased peripheral vascular resistance

• Over two-thirds of low birth weight infants are admitted to neonatal intensive care units with temperatures that would be considered hypothermic

• Therefore the main objective of aero-medical transfer of neonates lies in the correct management of temperature.

NOISE AND VIBRATION

• Constant noise – Difficult to communicate: Engines / turbulence / equipment / ear muffs

• Headaches

• Neonates are very sensitive to noise and therefore causes aggravation

INFORMATION

• The attending physician – determine destination, urgency, and mode of transport

• Discuss additional steps to further stabilize the patient

• An appropriate SAMPLE history

• The results of diagnostic tests

• Any special equipment or staff requirements

• Any problems anticipated

CREW

• The crew on the flight are the crew who will treat the patient – therefore know which crew are most required!

• The crew should be current with their aviation orientation• The crew should be familiar with the layout of the plane and

where the equipment is stored• The crew should know and understand and be able to explain

to patients and escorts the emergency procedures in the event of an emergency

• A Golden Rule: TRUST AND SHARE YOUR GUT FEELING TO THE FLIGHT AND MEDICAL CREW - ANY bad feelings MUST NOT BE IGNORED – no matter how trivial they may seem!!!

EQUIPMENT

• Critical aspect of any transfer – what you don’t have cannot be used

• Prepare an inventory of all necessary supplies and equipment

• Check and test all equipment prior to departure

• Have a “PLAN B”

• A N T I C I P A T I O N!

EQUIPMENT

• Defibrillators– Artefacts from vibration may occur– Ensure backup power supply / batteries

• NIBP– Gas expansion in cuffs may give inaccurate readings

• Pulse Oximeters– Vibration and noise may affect signal– Poor perfusion / temperature may affect readings

• Dopplers– Useful to assess pulses or foetal heart tones

• Incubator– Should be set at correct temperature– should have more than required battery supply (for the whole mission and not just the

flight– Spare warm blankets in case of incubator failure

PRE-FLIGHT STABILIZATION

• This is one of the most critical aspects of any transfer!

• Don’t be forced into a “scoop and run” scenario (obviously there may be some exceptions)

• Aero-medical “Feng Shui” – it is important to plan the packaging of patients and equipment according to your anticipation of what “can go wrong.” Access is vital!!!

PATIENTS AND ESCORTS

• Unless the mother is ill – she should accompany the neonate

• Ensure ID Bands are checked by the mother and receiving crew and hospital staff

• A toy for the child helps for comforting them• Patients, equipment and all supplies should be

secured safely before take-off and during the flight• Before take-off, ensure that: the escorts, patients

and crew are familiar with the emergency procedures and know where the emergency exits are.

Questions

End