This non-invasive method can tell the cardiovascular surgeon and anesthesiologists how successful the surgeon has been in removing air from the heart and if further action is needed.
"Our investigation basically related to brain function during cardiac surgery in children," Dr. Rosendo A. Rodriguez said. "Several problems may occur during this surgery that may potentially damage the brain."
Rodriguez and other investigators at the Children's Hospital of Eastern Ontario in Ottawa, Canada, have studied about 60 patients from infants to 18 year olds and intend to double this number by the end of the study.
The investigators will present their findings August 14th at the International Neurosonology '97 meeting here sponsored by the World Federation of Neurology and the Bowman Gray School of Medicine of Wake Forest University.
One concern is the small particles and bubbles of air that are ejected from the heart to systemic circulation during surgery, Rodriguez said. "We don't know exactly the effect on the brain. These emboli travel through the arteries in the brain and reach the brain tissue."
The surgeon goes through a process called de-airing to remove the air that has entered the heart during surgery, Rodriguez said. Transcranial Doppler has the ability to detect this air in the brain circulation when it is ejected from the heart. "The amount of air that is ejected to circulation is related to the effectiveness of the de-airing procedure," Rodriguez said.
The investigators looked for the correlation between how well the surgeon thought that the heart was de-aired versus the readings from the transcranial Doppler. This system is a good indicator of how much air is ejected, Rodriguez said.
"We have found that one of the advantages of doing this kind of monitoring is if you see lots of air, you can tell the surgeon he needs to do more deairing -- it is a feedback system," Rodriguez said.
By monitoring the patient, it helps them determine if action is needed, such as drugs, to protect the brain, and they don't have to wait until the end of the surgery.
Using a non-invasive method such as the transcranial Doppler with children has a particular advantage over methods such as the echocardiogram.
The transcranial Doppler requires a small-size probe applied around the temple area, while an echocardiogram is invasive and requires the presence of a cardiologist to interpret the echocardiogram during surgery.
The echocardiogram has additional risks not present with a non-invasive method like the transcranial Doppler.
"We have been able to integrate transcranial Doppler with other types of measurements," Rodriguez said. "Our philosophy is that (transcranial Doppler) is just a single window, not enough to see the whole inside of the house, but with two or three other windows, you get a better picture."
Rodriguez received the Popham Clinical Research Fellowship Award from Children's Hospital of Eastern Ontario in 1996 to continue his clinical investigations of brain function during cardiac surgery in children.
His colleagues in the study include Drs. Garry Cornel, chief of the Division of Cardiovascular Surgery, Lloyd Semelhago, William Splinter, Nihal Weerasena, and Lothar Broecker and Guy Millette of the Division of Cardiovascular Surgery and the Department of Anesthesia.
For further information, call Mark Wright (email: mwright@bgsm.edu) or Bob Conn (email: rconn@bgsm.edu) at 910-716-4587. Once International Neurosonology '97 has begun on August 13, call the conference press room at 910-724-6923.