Therapeutic Hypothermia - Methods - Invasive - Cooling Catheters

Cooling Catheters

Cooling catheters are inserted into the femoral vein. Cooled saline solution is circulated through either a metal coated tube or a balloon. The saline cools the patient’s whole body by lowering the temperature of a patient’s blood. Catheters reduce temperature at rates ranging from 1.5 °C (2.7 °F) - 2 °C (3.6 °F) per hour. Through the use of the sophisticated control unit, catheters can bring body temperature to within 0.1 °C (0.18 °F) of the target level. This level of accuracy allows doctors to avoid many of the pitfalls associated with excessively deep levels of hypothermia. Furthermore, catheters can raise temperature at steady rate, which helps to avoid harmful rises in intracranial pressure. Catheter-based temperature management has been shown to provide faster, more precise and more efficient cooling compared to all external methods, especially conventional. A number of studies in critically ill patients have demonstrated that therapeutic hypothermia via catheter is safe and effective in the treatment of a wide variety of patient populations.

Adverse events associated with this invasive technique include bleeding, infection, vascular puncture, and deep vein thrombosis (DVT). Infection caused by cooling catheters is particularly harmful, as resuscitated patients are highly vulnerable to the complications associated with infections. Bleeding too represents a significant danger to patients, due to a decreased clotting threshold caused by hypothermia. The risk of deep vein thrombosis might be the most pressing medical complication. One study (Simosa et al.) found that incidents of deep vein thrombosis increased by 33% if a patient’s catheter was kept active for 4 days or less and 75% if their catheter was left attached for 4 days or more. However, it is important to note that in the Simosa et al. study, the authors admit that it was a retrospective study of 11 patients (1 patient was excluded because she had a DVT prior to the study), and that all patients were predisposed to DVTs because of prolonged immobilization and failure to prophylactically anticoagulate the patients. The authors also admitted that they left the catheters in for 5–15 days, well past the four day maximum recommended by the manufacturer. Deep vein thrombosis can be characterized as a medical event whereby a blood clot forms in a deep vein, usually the femoral vein. This condition turns deadly when the clot travels to the lungs and causes a pulmonary embolism. Another potential problem with cooling catheters is the potential to block doctors' access to the femoral vein, which is a site normally used for a variety of other necessary medical procedures, including angiography of the venous system and the right side of the heart. However, most cooling catheters are triple lumen catheters, and the majority of post-arrest patients will require central venous access. Unlike non-invasive methods, which can be administered by nurses, the insertion of cooling catheters must be performed by a physician fully trained and familiar with the procedure. The time delay between identifying a patient who might benefit from the procedure and the arrival of an interventional radiologist or other physician to perform the insertion may minimize some of the benefit of invasive methods' more rapid cooling.