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Show GrGVJOUGG ED ElGCFi 8uTflGFtf Microwaves, like those in your oven at home, may someday increase the success rate in infant open-heart surgery, sur-gery, according to a University Univer-sity of Utah anesthesiologist. DEEP hypothermia--dras-tically lowered body temperature which greatly reduces bodily functions-is a common technique presently used in surgery to correct congenital heart disease in infants. "What is new is how we think the infant should be rewarmed following open-heart open-heart surgery which has utilized the cooling technique to a state of near suspended animation," according to Dr. K. C. Wong, chairperson of the Department of Anesthesiology at the University Univer-sity of Utah College of Medicine. "RECENT experiments on animals have convinced us that using microwaves to rewarm babies from inside-out inside-out would be a much more natural, safe and physiologically logical way to bring them back," he said. "In preparation for surgery, sur-gery, the baby is packed with ice and cooled down to 20 degrees Centigrade, which is about 68 degrees Fahrenheit," according to Dr. Wong. "THIS PUTS the infant in a state of near suspended animation. The baby's metabolism, me-tabolism, the chemical reaction reac-tion by which energy is taken in by a cell and waste given off, is reduced to about 20 percent of normal so that his blood flows very slowly even stopping the circulation entirely en-tirely at this point, body tissues tis-sues can be starved or deprived of additional oxygen and nutrients for up to an hour without being irreversibly irreversi-bly harmed," the Utah anesthesiologist said. Dr. Wong said this 'freezing' 'freez-ing' technique has several advantages over a cardiopulmonary cardiopul-monary bypass machine which acts as an artificial heart and lung during infant-cardiac infant-cardiac surgery. "FIRST. YOU get away from 'plumbing problems'", he explained. "A baby's heart is very small-only about the size of a chicken egg. The blood vessels are also small. There isn't a lot of room for the various tubes used in cardiopulmonary car-diopulmonary bypass." Additionally, a 10-pound baby has a small amount of blood, perhaps as little as a pint. It takes up to one and a half times the infant's blood capacity just to prime most of the bypass machines. This leads to dilution of the infant's in-fant's blood. " "WHENEVER YOU introduce in-troduce foreign bodies (i.e. tubes) into the circulatory system, it is necessary to prevent clotting by giving anti-coagulants which can lead to other surgical problems," Dr. Wong said. "The use of deep hypothermia hypother-mia solves these problems," he said. "ONE ADDITIONAL advantage ad-vantage to deep hypothermia in infant open-heart surgery is that the blood circulation is arrested and the surgeon is not faced with extensive bleeding in his working area," Dr. Wong said. The problem with rewarm-ing rewarm-ing the infant in the 'old way, from the outside-in, is that the tissue near the surface warms up and requires blood before the heart is warmed and vigorous enough to deliver it, Dr. Wong explained. "BY USING a microwave generator directed into the chest, we could rewarm the infant from the inside-out. First the heart is stimulated by the neat. The blood passing through the heart is also rewarmed. The warm blood then not only rewarms the tissues but also delivers oxygen and nutrients to the 'starved' tissues. The heart works, then, at a pace always just above the demand of the body tissues," Dr. Wong said. Dr. Wong has performed hypothermia experiments in more than 50 dogs at the University of Utah College of Medicine and successfully rewarmed them using a special microwave generator and applicator developed by the University's Department of Bioengineering. "THE LATE Dr. Curtis Johnson, Dr. Carl Durney and Dr. Douglas Christensen of electrical engineering, have been invaluable in developing our experimental microwave hardware. Dr. Dwayne Wes-tenskow, Wes-tenskow, a bioengineer of this department, continues to help with the research for refinement of this technique," tech-nique," Dr. Wong said. "We discovered in our experiments on dogs that when heat from the microwaves is held at 105 degrees Fahrenheit, the water molecules in the tissue are excited just enough to produce a slow, natural warming. OXYGEN consumption increases as the dog warms; blood pressure and heart rate resume and increase naturally na-turally and immediately as the microwave heat is applied without the use of drugs to stimulate the cardiovascular system." he said. "There is no question in my mind that deep hypothermia is the best method to prepare infants for open-heart surgery. "MORE WORK needs to be done before we will be ready to perform microwave rewarming on an infant following such surgery, but I would not hesitate to use it today on a person who was brought in suffering severe frostbite or accidental hypothermia," he said. "Infant open-heart surgery is just one example of the possible medical uses of microwave's heating of the inside of the body," says Dr. Wong. "Undoubtedly additional addi-tional uses will be discovered as research continues." |