A novel system for mild hypothermia.

Abstract

Mild hypothermia has been shown to provide protective effects in patients with ischemia (e.g. acute stroke and heart attack), but traditional methods for inducing, maintaining, and reversing hypothermia are slow, difficult to administer and control, and uncomfortable for patients. An innovative method produces mild, wholebody hypothermia (32 degrees C to 34 degrees C) by use of an endovascular heat exchanger placed into the inferior vena cava. A closed-loop system accurately changes core body temperature with average cool-down rates of 4.8 degrees C per hour, tight-target temperature control of +/- 0.1 degree C, and average rewarm rates of 1.9 degrees C per hour. By enhancing the mixing of blood in the vicinity of the heat exchanger, the disposable, small-diameter catheter efficiently exchanges heat between the closed-loop circulating fluid and the blood stream in response to body temperature. A control algorithm adapts to body physiology and thermal mass to mitigate temperature excursions. Flexible, bellow-shaped segments along the length of the catheter allow precise maneuvering within blood vessels. Heparin, covalently bonded to the catheter, helps control thrombogenicity. This novel design has potential clinical applications in cerebrovascular surgery, acute stroke, acute myocardial infarction, cardiac arrest, and fever control.