Wound ventilation : A new concept for prevention of complications in cardiac surgery

Sammanfattning: Cardiac surgery through an open chest wound is a major operation both in size and duration. The wound exposure to ambient air implies considerable risks. 1) Air may enter the heart and great vessels and embolize to the brain or cardiac muscle where it may cause dysfunction or permanent damage. 2) The wound is exposed to airborne bacterial contamination, which may lead to postoperative wound infection. 3) The wound is subjected to desiccation, which may lead to serious adhesions and possible impairment of cardiac function. Intraoperative wound ventilation with carbon dioxide (CO2) might help to protect the patient against these risks. CO2 is more soluble than air and thus less harmful to the human body. CO2 is also heavier than air, which facilitates the establishment of a CO2 atmosphere in the chest wound cavity. The present study investigated how the physical properties of CO2 could be used to prevent or reduce complications in cardiac surgery. The study shows that conventional insufflation devices such as an open-ended tube, a tube with a gauze sponge at the end, or a multi-perforated catheter cannot efficiently supply CO2 to the wound. The flow velocities, at which these devices supply gas, are too high and the resulting turbulence mixes and dilutes the delivered CO2 with ambient air. The net effect is a low degree of air displacement. Even more important, it also results in a much higher rate of direct airborne contamination and desiccation of the wound than what is the case without any CO2 insufflation at all. A new insufflation device, a gas-diffuser, was developed. The thesis shows that with this device a CO2 atmosphere of more than 99% can be created in the cardiothoracic wound. At a continuous flow of 10 L/min, wound ventilation should thus significantly decrease the risk of air embolism. Furthermore, this type of wound ventilation may reduce the risk of postoperative wound infection in three different ways. In the first place, the laminar outflow of CO2 from the wound opening withholds airborne contaminants from reaching the wound. Secondly, the bacteriostatic effect of CO2 may decrease the growth rate of bacteria in the wound. Thirdly, the addition of a few vol. % of a gasified antiseptic agent to the CO2 may decrease the number of bacteria in the wound or inhibit their growth even more. Finally, wound ventilation with humidified CO2 should significantly reduce desiccation of sensitive wound tissue. The present thesis indicates that intraoperative wound ventilation may provide a simple and effective method to reduce the risk of several life-threatening complications in cardiac surgery as well as in other types of surgery. Future clinical studies will eventually reveal its clinical significance.