ECMO for Severe Hypothermia in Adults

Introduction:

Extracorporeal membrane oxygenation (ECMO) is a life support procedure performed to help patients with oxygenation of blood and breathing when the patient is unable to perform the function due to some abnormality or medical condition affecting the heart and the lungs simultaneously.

What Is ECMO?

ECMO means extracorporeal membrane oxygenation. It is a device similar to the heart-lung bypass machine used during open-heart surgery. It takes over the functions of the heart and the lungs and works for them. It pumps and purifies the blood outside the patient’s body. This allows the heart and lungs to rest. In simple words, ECMO receives your deoxygenated blood from the body, and after receiving it oxygenates the blood and removes carbon dioxide, increases the temperature of blood similar to body temperature, and pumps that blood back to the body. There are two types of ECMO and they are:

1. VA ECMO (Veno-Arterial Extracorporeal Membrane Oxygenation): This ECMO is connected to both vein and an artery. It is used when both heart and lung functions are compromised.

2. VV ECMO (Veno-Venous Extracorporeal Membrane Oxygenation): An ECMO connected to one or more veins, located near the heart is called VV ECMO. It is used when the lungs do not functioning properly.

What Are the Indications of ECMO?

• Used as a supportive aid for patients recovering from post-cardiac or pulmonary failure.

• Used to assess other organs like the brain, kidneys, and liver before undergoing heart or lung surgery

• Used as an adjuvant during procedures that carry a high risk of cardiac failure such as cardiac catheterization lab (invasive procedure performed to assess blood flow to the heart from the arteries).

• Used as a bridging support to devices assisting heart function, like left ventricular device (LVAD).

• Used to maintain the vitality and oxygenation of the tissues in patients awaiting lung transplantation, making them better recipients.

How Is an ECMO Performed?

ECMO is performed in three stages involving the insertion of catheter or cannulas, maintenance of ECMO, and termination of the procedure.

1. Insertion:

• The procedure is done in the patient's room, an operation theatre is not required.

• The patient is given anesthesia, painkillers, and anti-coagulants to prevent blood from clotting.

• ECMO catheter (thin tube) is inserted into an artery or vein by a trained surgeon.

• The placement of the catheter is confirmed with an X-ray.

2. Maintenance:

• While the patient is on ECMO, the vital signs and breathing is continuously monitored by a surgeon, nurses, and respiratory therapists.

• The ventilator is also connected to the ECMO to allow the patient’s lungs to rest and heal.

• Nutrition is supplemented through a nasogastric tube or intravenously since the patient is under sedation and will have a breathing tube through the mouth.

• ECMO catheters are used to administer medications like heparin to control blood clots, antibiotics to avoid infection, painkillers, diuretics to improve kidney function, sedatives to prevent bodily movements and induce sleep, and electrolytes to maintain the salt and sugar balance.

3. Termination:

• It is the step where ECMO is removed from the body. But, before removal, the functioning of the heart and the lungs is checked.

• Confirmatory tests are done to assess whether the organs are ready to function on their own.

• After ECMO catheters are removed, the vessel through which the tubes were inserted are repaired with stitches.

What Are the Advantages of ECMO?

• ECMO is a life-saving device for critically ill patients in intensive care units.

• It takes the workload of the heart and lungs, allowing the organs to recover.

• Makes it possible to keep a patient alive during surgical procedures.

• Gives circulatory and ventilatory support for transplant patients until they receive the donor organs.

• Supports babies' hearts and lungs that are underdeveloped.

What Is Hypothermia?

Hypothermia is the condition in which the body’s temperature gets reduced below 35 degrees Celsius. It occurs when the body is exposed to very cold temperatures for a long period. On exposure to cold temperatures, the body starts to lose heat rapidly whereas heat production is slow. It will eventually lead to loss of stored energy which drops the core body temperature. It is a dangerous medical condition because low body temperature affects the central nervous system and the patient is in a confused state.

Who Are at Risk of Hypothermia?

The following group of people is at increased risk of getting hypothermic:

• Elderly with a lack of adequate nutrition, protective clothing, and heat.

• Babies and infants sleeping in cold environments.

• Individuals who stay outdoors for a long time - the homeless, hunters, and workers.

• People who take illegal drugs and consume alcohol.

What Are the Signs and Symptoms of Hypothermia?

The followings are the signs and symptoms of hypothermia in adults and children-

1. Adults:

• Fatigue.

• Confusion.

• Dizziness.

• Slurred speech.

• Shivering.

• Loss of memory.

• Clumsy hand and feet movements.

2. Children:

• Cold skin.

• Bright red discolored skin.

• Tiredness.

How Is ECMO Used for Hypothermia in Adults?

• Rewarming severely hypothermic patients using ECMO is the choice of treatment for patients with hypothermic cardiac arrest and instability. It provides a stable, gradual, and controlled increase in body temperature, along with circulatory and respiratory support during the recovery period from hypothermia.

• The ECMO procedure remains the same for hypothermia except for a few differences in the vascular access and maintenance of blood flow. Hypothermia required rapid fluid resuscitation and a slight change in the procedure.

• The ideal blood flow and re-warming rate are yet to be studied and standardized.

• Advances cannulas are developed for ready-to-use ECMO devices to shorten the time needed for resuscitation.

• The ECMO type most preferred is VA-ECMO due to its easy availability, minimal anticoagulant requirement, and longer support time.

• It is indicated in stage 3 hypothermia (20-28 ℃) presenting with unconsciousness and stage 4 hypothermia (less than 20 ℃) with no vital signs.

• The maximum rewarming rate is up to 6℃ per hour given over a wide range of time.

• Cardiac output decreases with slow ECMO post-treatment but does not cause lung lesions.

• The patient with cardiac arrest should be first moved from the cold environment.

• For ECMO, vessel access is taken through the femoral vein and artery(which develop the complication of leg ischemia) using distal perfusion cannulas. Ultrasound-guided venous and arterial access is also done.

• Research is being done to develop cannulas that enable parallel and bidirectional flow for blood perfusion to the extremities.

• Challenges faced by a severely hypothermic patient are depletion of body fluid and the immediate need for aggressive fluid replacement. It is essential to maintain the blood flow through ECMO.

• Tissue edema and compartment syndrome are other complications that develop in hypothermia posing a challenge for ECMO procedure.

Conclusion:

At present, there is no standardized protocol for ECMO while treating a severely hypothermic patient. New cannulas with advanced features and simplified ECMO kits which are ready to use are under research. Studies are ongoing to reduce the need for heparin will potentially shorten the resuscitation time. Even though ECMO is beneficial in rewarming hypothermic patients, it has its own risks and complications, which should be addressed by trained and skilled clinicians in the emergency department.