Gamble, specializing in anesthesiology and pediatric critical care in the U of S College of Medicine, has been working with a group of doctors, researchers and veterinarians for the past two years on an extensive multidisciplinary hemodynamics study.
“The cornerstone to all acute care medicine is resuscitation,” Gamble explained. “I think a lot of what is thought of resuscitation is what you see on TV. But resuscitation is actually a bigger process than that, and when we resuscitate people what we really are trying to do is ensure that we help the patient to circulate oxygen in the blood to the organs and make sure all of the tissues are functioning.
“But the cornerstone to the first part of this is what we call hemodynamic resuscitation, (and) that’s often based upon a measurement of blood pressure.”
Gamble said most physicians use that blood pressure measurement as a surrogate for cardiac output—how much blood is being pumped out of the heart—because it’s relatively easy to measure in a clinical setting. It can be measured non-invasively, and is often assumed to be an accurate reflection of cardiac output.
However, blood pressure may not be the best way to guide resuscitation. It may be that cardiac output is the more accurate way of guiding resuscitation. And if that’s the case, the medical instrument industry has a wide array of equipment designed specifically for measuring cardiac output.
That industry is the primary focus of this study: how accurate are the machines used to measure cardiac output being used by our physicians and hospitals?
“The medical device industry is quite robust,” Gamble said. “So we’re trying to determine how accurate these devices are that clinicians use to help measure cardiac output against a gold standard.”
That gold standard is a machine called a peri-aortic flow probe, which has a small blue ring that sits around the aorta to monitor actual blood flow, but obviously needs to be surgically implanted and is therefore not something that can be used by most acute care doctors.
“This measures cardiac output in a very accurate way, but a very invasive way,” Gamble said. “So this blue ring sits around the aorta, the vessel that immediately comes from the heart, so all the blood that comes from the heart goes past the aorta and it can measure (the) flow.”
The second focus of the study is to assess how well blood pressure reflects cardiac output. This is done by comparing blood pressure measurements to peri-aortic flow probe. And both of these research topics bring us back to the collaborative portion of this project: the Western College of Veterinary Medicine (WCVM). To test both the machines and resuscitation, Gamble and his team—which includes physicians and researchers from anesthesiology, veterinary medicine, neuro- surgery, general surgery, perfusion, neurophysiology, and the Department of Chemistry—turned to the WCVM for help.
The team is using a porcine model to test both projects at once: hooking up the machines to the subject to test their accuracy, and monitoring the blow pressure and flow as they run through different stress levels experienced during surgical procedures and illnesses, in order to monitor the hemodynamic resuscitation and tissue function.
“We don’t know how much flow is enough, but we wanted to be able to actually measure function—or an indication of function—at the tissue level,” Gamble said. “And the way I see the world, if we don’t resuscitate the brain, there’s no point resuscitating the individual. But it’s hard to measure actual cellular function.
“But at the end of the day the cardiovascular system is designed to supply oxygen to the tissue, and the tissue absorbs that oxygen. If the tissue is not getting enough oxygen, it’ll extract more oxygen and we can measure the saturation.”
The eventual goal is to make it easier for anesthesiologists, critical care physicians and emergency medicine physicians to ensure adequate blood flow to avoid accidental tissue death by figuring out what the ideal blood flow indicator is, while also determining which of the top three industry-supplied medical devices is the most accurate.
“(If) we can use our indicator to change, to intervene or not intervene, or escalate interventions based on actual tissue oxygen level (during surgery), we can fundamentally change how we look at resuscitation.”
This has implications in terms of lives saved, as well as financial considerations, as the medical device industry is gigantic. Every time one of the monitors is used it costs at least $200, which is significant, especially if the device isn’t telling the physicians everything they need to know to make an informed decision.
And the University of Saskatchewan is one of very few places in Canada where research like this can logistically happen. With a medical school, veterinary college and chemistry department all in close proximity, the ability to carry out the testing is available to only one other university in Canada. And that ability to collaborate with so many specialists is almost as exciting to Gamble as the research itself.
“I think it’s great that we’re taking advantage of all of these features the University of Saskatchewan has at its disposal, and bringing them together.”
Marg Sheridan is an online communications co-ordinator in the College of Medicine.