The present invention relates to over the wire heat exchange catheters, particularly to catheters having a distal end with a coiled heat exchanger.
In warm blooded creatures, temperature regulation is one of the most important functions of the body. Despite the known importance of properly maintaining body temperature, scientists have discovered certain beneficial effects of artificially inducing a hypothermic state. For instance, cooling the body can help regulate vital functions during surgery by lowering the metabolism. With stroke, trauma, and other conditions, hypothermia is believed to reduce the permeability of the blood/brain barrier. Also, induced hypothermia is believed to inhibit the release of damaging neurotransmitters, inhibit calcium mediated effects, inhibit brain edema, and lower intra cranial pressure. Regardless of the particular mechanism, the present invention understands that fevers degrade the outcomes for patients suffering from brain trauma or stroke, and moreover that hypothermia improves the outcomes for such patients.
Hypothermia may be induced locally or systemically. With local hypothermia, physicians focus their cooling efforts on a particular organ, limb, anatomical system, or other region of the body. With systemic hypothermia, body temperature is lowered without particular attention to any body part.
One technique for inducing systemic hypothermia includes packing the patient""s entire body in ice. Although this technique has been used with some success, some physicians may find it cumbersome, and particularly time consuming. Also, it is difficult to precisely control body temperature with ice packing. As a result, the patient""s body temperature overshoots and undershoots the optimal temperature, requiring physicians to add or remove ice. Furthermore, there is some danger of injuring the skin, which is necessarily cooled more than any other body part.
In another approach to systemic hypothermia, the patient is covered with a cooling blanket, such as an inflatable air-filled or water-filled cushion. Physicians control the patient""s temperature by regulating the temperature of the inflation medium. Nonetheless, some delay is still inherent, first for a cooling element to change the temperature of the cooling medium, and then for the temperature adjusted cooling medium to cool the desired body part. This delay is even longer if the targeted body part is an internal organ, since the most effective cooling is only applied to the skin, and takes some time to successively cool deeper and deeper layers within the body.
A proven approach to inducing hypothermia is by circulating a cooling fluid through a cooling catheter placed inside a patient""s body. The catheter may be inserted into veins, arteries, cavities, or other internal regions of the body. It is often desired to precisely position such a catheter within the body of a patient to provide for local, or, systematic heat exchange.
An over-the-wire heat exchange catheter includes a heat transfer extension having at least one supply lumen and at least one return lumen for circulating heat exchange fluid within the catheter. The catheter has a distal tip and valve attached to the distal tip. The valve automatically seals the distal tip around a guidewire or a mandrel to seal the heat transfer extension and inhibit escape of the heat transfer fluid from the heat transfer extension.
The valve is normally closed, but opens upon receipt of a guide wire and seals the distal tip around the guidewire. The valve automatically closes upon removal of the guide wire to re-seal the distal tip to inhibit escape of the heat exchange fluid from the heat transfer extension.
The valve has a disk shape and an aperture for admitting a guidewire. The aperture is a centrally defined aperture for admitting a guidewire, and opposing concave sides. According to aspects of the invention, the valve is made from silicon or plastic. According to another aspect of the invention, the valve includes sealed flaps. According to a further aspect of the invention, the valve includes a spongy membrane.
The heat transfer extension includes a flow through lumen to deliver fluids via the distal tip of the catheter.