Car Exhaust Therapy For Cardiopulmonary Bypass? A Poison As Protector

Main Category: Cardiovascular / Cardiology
Also Included In: Respiratory / Asthma
Article Date: 23 May 2008 - 2:00 PDT

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A study featured in this month's Anesthesiology could represent an important step toward the eventual use of carbon monoxide (CO) to promote cell survival and reduce lung inflammation in patients undergoing cardiopulmonary bypass (CPB) surgery.

Torsten Loop, M.D., and his group from the Department of Anesthesiology, University Medical Centre Freiburg, Germany, were seeking a new drug therapy for patients who may experience life-threatening lung injury during CPB surgery.

"Cardiac surgery is one of the most extreme situations a patient can face," said Dr. Loop. "Although a heart-lung machine ensures that organs are supplied with blood, and therefore oxygen, the nature of heart surgery means that normal operation of the lungs is impaired potentially resulting in lung injury."

Although only approximately 2 percent of patients undergoing cardiac surgery suffer from life-threatening lung injuries, mortality rates for these patients can exceed 60 percent.

Dr. Loop and his team used low doses of inhaled CO in pig models while employing beating-heart CPB.

"Our findings support that inhaled CO provides anti-inflammatory effects in the lungs and decreases the instance of cell death during CPB," said Dr. Loop.

"Additionally, and of greater importance, these effects occurred when CO was administered as a pre-treatment with the advantage of short exposure time, which limits how avidly CO can bind to hemoglobin."

The poisonous effects of CO are seen when it is allowed to freely bind to the hemoglobin within red blood cells, such as in breathing automobile exhaust or inhaling cigarette smoke. High levels of exposure limit the ability of the blood to carry oxygen. Remarkably, though, Dr. Loop's study shows that low doses can protect against tissue injury.

In a companion editorial to Dr. Loop's study, John G. Laffey, M.D., of the Clinical Sciences Institute, National University of Ireland, lauds the study for the doors it may open in the study of pre-treatment for CPB.

"A fascinating aspect of this study is that pre-treatment with CO before CPB was effective in protecting the lung," said Dr. Laffey. "These findings may support evidence that CO can trigger the body into a state that helps to protect it against the sometimes damaging effects of CPB."

Controlled human studies examining the effects of CO and organ function do not yet exist. However, the results of Dr. Loop's study add weight to the feasibility of conducting such clinical trials.

According to Dr. Laffey, "The demonstration that CO may reduce pulmonary inflammation and injury following CPB is an important and novel finding. Relative ease of administration, probable safety when given at low doses for short periods, and likely protective effects for multiple organs make this a fascinating agent with clear therapeutic promise."

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