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RESULTS PROMISING FOR TREATMENT OF SICKLE CELL ANEMIA WITH NITRIC OXIDE
William A. McDade, M.D., Ph.D.
ASA ANNUAL MEETING
EMBARGOED UNTIL: Monday, October 20, 1997
CONTACT:
Denise M. Jones
Philip S. Weintraub
(847) 825-5586
Oct. 18-22: (619) 525-6411
SAN DIEGO -- Reassessing some old theories based on new research could offer help for the thousands of sufferers with sickle cell anemia.
Nitric oxide (NO), a gas that has been used successfully to treat certain lung ailments, may have another application--the "unsickling" of sickled cells, according to the results of laboratory research conducted at the University of Chicago.
The finding, reported at the American Society of Anesthesiologists annual meeting, presents the intriguing possibility that NO may be suitable for studies in patients with sickle cell disease, anesthesiologist William A. McDade, M.D., Ph.D., said.
Sickle cell disease most frequently occurs in people of African ancestry and is caused by a flaw in the gene that makes hemoglobin, the oxygen-carrying molecule in blood. This flaw makes hemoglobin molecules stick to one another, forming rigid rods within the red blood cells. The disease gets its name from the way in which these rods distort the shape of the cells, causing them to become crescent-shaped. The rigid cells often get stuck in small blood vessels and stop the flow of blood. This condition depletes oxygen from tissues in other parts of the body causing a number of maladies, including kidney failure, diseases of the retina, strokes, pneumonia and severe pain. Ten percent of African-Americans carry the sickle cell gene, and one in 400 has the disease.
A serious, potentially life-threatening complication seen in some sickle cell disease patients is acute sickle chest syndrome. Often, this is caused by the blockage of blood vessels in the lungs or chest.
NO, even in small amounts, causes smooth muscle in the blood vessel wall to relax and the entire vessel to dilate, Dr. McDade said. Anesthesiologists have administered an inhaled form of NO to treat patients with pulmonary hypertension, a condition marked by abnormally high pressure within the arteries and lungs.
"Since nitric oxide is a powerful dilator of blood vessels and some patients with sickle cell disease suffer from episodic congestion of lung blood vessels, nitric oxide might be useful in the treatment of this problem," Dr. McDade said.
In the laboratory, researchers measured the effects of four different concentrations of NO on purified, oxygen-free samples of sickle hemoglobin. Even at the lowest concentrations, NO slowed cell sickling and even promoted the unsickling of sickled cells, Dr. McDade reported. The higher the concentration of NO, the stronger NO's favorable effect, he said.
The discovery counters research conducted more than 20 years ago that suggested NO might actually enhance the formation of sickle cells, Dr. McDade said. "These earlier findings may have led investigators to withhold NO treatment from sickle cell patients for fear of causing more cell sickling," he said.
The new findings could set the stage for clinical research, Dr. McDade said.
Copyright (c) 1997 American Society of Anesthesiologists
All Rights Reserved
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MEDIA NOTE: Please note, the substance used in this study is nitric oxide, not nitrous oxide, the chemical often referred to as "laughing gas," which is used as a light anesthetic in dentistry and some surgeries.
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