Commercially available hypothermia induction devices are based on invasive and non-Invasive methods. Invasive methods tend to provide higher heat transfer rates than non-invasive methods, but their use requires specially trained physicians and is associated with a much higher range of possible side effects.
Invasive methods include:
- Endovascular cooling catheters tipped with a balloon percolated by cold water.
- Irrigation of the body cavities with cold water.
- Intravenous or intraosseous infusion of cold fluids.
- ECMO cooling.
Non-invasive methods include:
- Plastic body wraps percolated by cold water.
- Imitation of cold water immersion.
- Spraying evaporating coolant into the nasal cavity.
- Cooling cervical collar.
Endovascular cooling catheters (Alsius CoolGard 3000®, Zoll Medical; Thermogard XP®; Philips InnerCool RTx) do not provide fast heat loss. Their cooling rates are about the same as the cooling rates of cooling body wraps. Endovascular cooling catheters are invasive, they require the use of systemic anticoagulation, making them unsuitable for use out of hospital settings. The adverse effects include bleeding, infection, vascular punctures, and deep vein thrombosis. They are not suitable for targeted temperature maintenance or rewarming.
ECMO allows a very rapid rate of heat loss by pumping blood through a cooler. ECMO also allows controlled re-warming. However, it is invasive, requires the presence of a specially trained physician, perfusionist and nurses and requires systemic anticoagulation. It can be used only either in the Intensive Care Unit or Operating Room settings. Due to the technical complexity, ECMO requires a longer time to start than other methods. ECMO is associated with significant side effects, including bleeding, infection, deep vein thrombosis and stroke. It is unsuitable for out of hospital use.
Intravenous or intraosseous infusion of cold saline produces fast heat loss, can be used in pre-hospital settings and is inexpensive, but it requires administration of non-physiologically large volumes of fluids, leading to respiratory and/or cardiac failure, which can be detrimental. In addition, it does not allow accurate control of temperature reduction, temperature maintenance, and precise re-warming.
Irrigation of body cavities with cold saline (Veratherm®) does not offer higher heat transfer than cooling blankets. It is invasive, relies on the presence of a trained physician, can’t be used in pre-hospital settings, and may lead to fluid overload.
Cooling body wraps (Atticouris Medical Criticool PRO®; CR Bard Arctic Sun®; Genthrem Medical Blanketrol III®; Stryker Altrix®) are the most widely used cooling methods, representing about 80% of the hypothermia equipment market. They do not provide fast heat loss in adult patients, requiring up to 6 to 8 hours to achieve the target temperature. They are relatively large and are ill suitable for out of hospital use. They cover almost the entire body and obstruct access for physical examination or performance of CPR. Accurately controlled rewarming is hard to achieve.
Coldwater immersion imitating device (ThermoSuit®) offers a high rate of heat loss. The drawbacks include very large size, restriction of access to the patient, inability to use in prehospital settings, and inability to maintain target temperature or re-warming.
Irrigation of the nasal cavity with evaporative coolant (Braincool Rhinochill®) is compact and can be used in pre-hospital settings, but it does not provide fast heat loss and can cause thermal injury to the nose and nasal cavity. It does not allow targeted temperature maintenance or re-warming.
The intranasal balloon-tipped cooling catheter (Quickcool®) is portable and can be used in prehospital settings, but offers a slow rate of cooling and it does not allow targeted temperature maintenance or re-warming.
Excel Cryo Cooling® cervical collar is easy to use and compact and it allows for the initiation of hypothermia in prehospital settings. This device has a slow cooling rate and it does not allow targeted temperature maintenance or re-warming.
All of the currently used methods for the induction of therapeutic hypothermia have numerous shortcomings. Most of them can’t be used in prehospital settings, which leads to significant delays in achieving the required level of cooling. Most of them are not able to maintain steady body temperature. Only several devices allow rewarming, however, none of them allows rewarming at a precise rate. Methods that can be used in prehospital settings are unable to achieve a fast rate of cooling.
In conclusion: none of the currently used methods for the induction of therapeutic hypothermia is ideal.
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