Expert Q&A: Cardiac surgery care for diabetics

Answers provided by Tony Furnary, M.D., cardiothoracic surgeon at Providence St. Vincent Medical Center.
Q. What can you tell us about the unique risks among diabetic cardiac surgery patients?

People with diabetes who undergo coronary bypass have a risk of death between 25 and 30 percent higher than people without diabetes. This increased risk affects a significant portion of the population: In the United States today, 30 percent of people undergoing open-heart surgery are diabetic. 

Fifteen years ago, we started investigating the relationship of hyperglycemia, or high glucose levels, to adverse outcomes in diabetic patients. We found that hyperglycemia is intimately related to death rates.

Q. Can you describe the study you’re doing with diabetic cardiac surgery patients?

Based on our findings about the relationship between hyperglycemia and cardiac surgery complications, we surmised that the most effective approach would be to normalize blood sugar levels in diabetics.  

In 1987, we began to study all our diabetic heart surgery patients. We have divided into two groups the 3,550 diabetic patients who underwent coronary bypass since that time. Following surgery, one group of patients received insulin subcutaneously – under their skin – in order to maintain their glucose levels at a low rate. The second group of patients received insulin intravenously to lower their blood sugars.

Q. What are the results of your study?

We found that the patients who received intravenous insulin had much better blood sugar control than those who received subcutaneous insulin. As a consequence, their mortality rate was 60 percent lower than that of the patients who received subcutaneous insulin. Specifically, the patients who received intravenous insulin had fewer fatal arrhythmias and lower incidence of death from heart failure after an open-heart operation.

Importantly, we’ve shown that by normalizing high glucose levels in coronary bypass patients, we lower death rates among diabetics to that of the non-diabetic population.

Q. How, specifically, does lowering glucose levels benefit the heart?

Giving patients insulin lowers their glucose levels, which boosts the heart’s energy capacity and reduces the risk of heart failure and arrhythmias.

Q. What is a protocol, and what is the Portland Protocol?  

A protocol is a detailed series of steps that should be followed during medical treatment. 

Our research has enabled us to define a series of steps, called the Portland Protocol, which should be followed when treating diabetic heart surgery patients. The Portland Protocol uses intravenous insulin to force diabetic patients’ blood sugars to a pre-determined target range.

Q. How many people could be helped by these findings?

The Portland Protocol is now used at various heart surgery centers throughout the country and throughout the world. However, if all the heart surgery centers in the United States used the Portland Protocol today, over 2,200 lives per year would be saved.

Although the results of our study are just now becoming available to the general public, Portland heart surgery patients have been benefiting from this protocol for the past 10 years.