His determined research endeavors of more than 13 years have gone a long way in reducing the risk of memory loss in patients who undergo cardiac surgery. Dr. Grocott has carved a niche for himself in modern medicine by elaborating on the relationship between temperature management during cardiac surgery and cognitive brain function.
According to Dr. Grocott, a majority of medical centers have modified their temperature management strategies during cardiac surgery as a result of a great body of evidence supplied by Duke, along with other corroborating work. “We have known for decades that there is a brain-temperature relationship. Although a neuroprotective effect of hypothermia (cold temperature) has yet to be definitively established in cardiac surgery, we have demonstrated that the reverse is true – that is, higher than normal temperatures can actually injure the brain.”
For Dr. Grocott, an anesthesiologist, focusing on the relationship between temperature and cognitive function was intuitive. “We are the frontline people who monitor patients. It is a very natural thing for the anesthesiologist to be involved in monitoring and managing temperature.” Anesthesiologists have the ability to employ techniques and drugs that impact body temperature. So, not only do they monitor, they can also direct therapy and use cooling and warming devices to change temperature.
Hypothermia has always been an integral part of cardiac surgery. In the early days, Dr. Grocott recounted, patients undergoing cardiac surgery were routinely cooled down to the high 60's from the normal temperature of 98.6°F. However, the flip side of low temperatures, he added, is that at the end of the operation, the patient has to be rewarmed to a normal temperature compatible with normal organ function. The temperature of the patient today is much higher, usually kept anywhere between 86°and 93.2°F. Research in the past 10 years has highlighted the importance of how the patient should be rewarmed in cardiac surgery. “Temperature management is a very important part of cardiac surgery. It is how you rewarm the patient that we have been modifying over the years.” Dr. Grocott’s early work focused on the accuracy of temperature monitoring in different areas of the body, especially the brain. According to him, there is a tremendous temperature gradient across the body. Most people check the body temperature with a thermometer in the ear or under the tongue. However, monitoring the temperature in one area of the body may not necessarily be an accurate indicator of the temperature in another part, particularly during times of rapid temperature change, such as is seen during surgery, he cautioned.
“I wanted to make sure that we were monitoring the temperature in the brain properly so that we could make use of the beneficial effects of hypothermia. When you rewarm the brain, for which we use warmed blood from the heart-lung machine, the rest of the body is very slow to rewarm. If you are monitoring the temperature in the bladder, it may be three or four degrees colder than the brain temperature. So, if you try to rapidly rewarm the bladder to 98.6°F,you are likely to considerably overheat the brain.”
After it was identified that aggressive rewarming of patients was a problem, the Duke DREAM Team conducted a study with Dr. Grocott comparing different rewarming rates between patient populations. “We took a group of patients that were cold and rewarmed them in a conventional manner, which was very rapid, and compared them with a group of patients that were cold and rewarmed much slower. We found that neurological outcomes were much better in patients that we rewarmed more slowly. The peak temperatures in the group rewarmed slowly were much lower, suggesting that we were not overheating the brain.”
Like most researchers, Dr. Grocott thrives on the long-term benefit his efforts can have on patient care. “Although one clearly gains satisfaction from the everyday care offered in getting patients through risky surgery safely, it is even more rewarding to know that the research that we are currently doing has the potential to fundamentally change how we practice anesthesia and take care of the cardiac surgery patient,” he emphasized. As a result of the changes implemented at Duke relating to temperature management, Dr. Grocott assures patients that their risk of suffering memory loss has been reduced.
However, the risks have not been eliminated entirely, he admits cautiously. Vigorous efforts are under way at Duke to better characterize the genetic risk factors that affect outcomes in cardiac surgery as well as in the screening of neuroprotective drugs in the laboratory that may be promising in clinical trials.