By Heather Brown
A heart-lung bypass machine, also known as a pump, keeps the patient alive by draining blood from the body into a reservoir, where it is stored, then cooled, oxygenated and pumped back into the body. The amount of blood pumped and the speed at which it flows into and out of the machine are regulated either by a series of rollers or a centrifugal device.
Most hospitals use the roller head technology, which draws blood from the body through tubes connected to the machine. Blood is compressed in the tubes as it passes by the rollers, exposing it to trauma it doesn’t usually encounter when flowing freely in a person’s body.
Perfusionist Jennifer Bezaire prepares to initiate the cardiopulmonary bypass. She will then stop the patient’s heart to enable surgery. (Photo by Yuri Markarov)
A heart beats about 1,000 times in one day and about 35 million times in a year. Over a lifetime, a person’s heart will beat 2.5 billion times.
The centrifugal device maintains blood flow in and out of the body through centrifugal force, a more natural way that causes little or no damage to the blood because it is not being squeezed through rollers.
St. Michael’s began using the centrifugal device in February. It is the only teaching hospital and one of only two in Ontario to use this device exclusively during open-heart surgeries.
The centrifugal pump in action pulling blood from a patient’s body and circulating it back during open heart surgery. (Photo by Yuri Markarov)
Between February and September the centrifugal device has contributed to reducing the hospital’s blood transfusion rate during open-heart surgery. In the month of August the rate of transfusion decreased by 70 per cent compared to last year, further positioning St. Michael’s as a centre for excellence in blood management.
“This device enhances patient safety during open heart surgery,” said Constantine Dalamagas, the chief perfusionist at St. Michael’s. “Not only does it handle the blood more gently, but it also reduces air pockets by pushing the air back into the heart lung machine’s reservoir, preventing it from going into the body and causing complications such as an embolism or air pocket within a vein.”
The centrifugal device spins at roughly 2000 rpm, moving four to six litres of blood per minute through the machine and back into the body — 20 to 25 times faster than the roller head device.
Maintaining more natural flow rates at greater velocities during open heart surgery, with fewer transfusions often results in patients being able to go home sooner with fewer complications.
About St. Michael’s Hospital
St. Michael’s Hospital provides compassionate care to all who enter its doors. The hospital also provides outstanding medical education to future health care professionals in 27 academic disciplines. Critical care and trauma, heart disease, neurosurgery, diabetes, cancer care, care of the homeless and global health are among the hospital’s recognized areas of expertise. Through the Keenan Research Centre and the Li Ka Shing International Healthcare Education Centre, which make up the Li Ka Shing Knowledge Institute, research and education at St. Michael’s Hospital are recognized and make an impact around the world. Founded in 1892, the hospital is fully affiliated with the University of Toronto.