A Medical Device Daily

Surgeons are testing new ways of treating the number-one cause of death from trauma in this country — massive bleeding.

Investigators from Massachusetts General Hospital (Boston) are deeply cooling the entire body to prolong the time surgeons have to correct bleeding problems before the brain dies. In their most recent study, the surgical researchers found that profound hypothermia effectively treated shock that could not be reversed by standard cardiopulmonary resuscitation, thus saving lives that otherwise would be lost.

Findings from this study were reported at the 2007 93rd annual Clinical Congress of the American College of Surgeons (ACS; Chicago) that began Sunday and continues through today in New Orleans.

“We’re using this strategy in a situation where the alternative is almost certain death. We’re not talking about a scenario where you might decrease the mortality from 10% down to 5%. We’re talking about a highly lethal model, so we need to do something that is fairly dramatic and outside the box,” according to Hasan Alam, MD, associate professor of surgery at Harvard Medical School (Boston) and a trauma surgeon at Massachusetts General Hospital.

Another study presented at the ACS meeting highlighted the work of Vanderbilt University (Nashville, Tennessee), who are aggressively treating hemorrhage with a predefined cocktail of blood products to replenish not only the volume of fluid but also the specific blood components trauma patients lose in the early period after injury.

According to findings from this study of massive hemorrhage, the trauma exsanguination protocol (TEP) reduced the odds of mortality by over 70%, saving the lives of patients who were not expected to live, and reducing the number of patients who were expected to die.

In reporting on the Massachusetts General Hospital study, Alam explained that more patients under the age of 34 die of traumatic injuries than of all other diseases combined, and the number one reason why these patients die is massive bleeding.

“If you look at autopsy data, most patients have bleeding problems that were fixable. We weren’t able to fix them because once patients lose enough blood, they go into cardiac arrest, and the brain dies in about 4-5 minutes. We simply don’t have enough time to get to the bleeding source and control it,” Alam said.

Profound cooling of the body decreases the metabolic rate of the brain so it slows down but does not completely stop. So instead of consuming huge amounts of oxygen, the brain can be kept alive with only small amounts of oxygen delivery. According to Alam, once the brain is cooled down to about 10 degrees C, it can stay alive for about two hours, giving surgeons enough time to fix underlying bleeding problems.

Alam and his research associates have been testing hypothermia as a treatment for massive blood loss for about five years. In that time, they have determined the optimal rate of cooling and rewarming, the desired depth and duration of cooling, and other practical aspects of the technique through a series of studies.

Their most recent studies have evaluated the effectiveness of hypothermia in an extremely challenging model — a combination of massive blood loss as well as injuries to major organs.

“The goal of this study was to take the technique into a realistic scenario. In the past, we found that the technique worked in models that had no confounding variable other than an injury to a blood vessel, which is easy enough to fix. Once you get to it, you sew it up and you control the bleeding. But what if you have an injury to the abdomen and there is spillage of stool in the abdomen or an injury to the liver or the spleen that continues to spill blood? This study looked at a realistic lifelike trauma scenario,” Alam explained.

Findings from these studies resolved two major concerns about profound hypothermia: the danger that exposure to profound cooling might precipitate a malfunction in the coagulation process and cause bleeding and that it might reduce immune function and lead to infectious complications.

“We found that cooling causes bleeding, but when the body is cold and bleeding, it is not consuming much oxygen and so it is in a protected state. Once you reverse the hypothermia and warm the body, the bleeding stops. Also, profound hypothermia that is maintained for only a short period of time followed by active rewarming is not associated with infectious for complications,” Alam said. He said the latest study also demonstrates that induction of profound hypothermia can preserve organs and prevent death, even in the setting of advanced shock that does not respond to conventional methods of cardiopulmonary resuscitation and is typically considered “irreversible.”

The trauma exsanguination protocol used by trauma surgeons at Vanderbilt University Medical Center addresses massive blood loss by assuming the patient is coagulopathic upfront and presumptively treating them, according to Brigham Au, a third-year medical student. Patients who are so severely injured that they need a transfusion of 10 or more units of blood typically receive infusions of red blood cells to replace the blood they have lost. Many times, however, patients bleed out what they are given because the transfusions do not contain sufficient amounts of blood products to stimulate coagulation.

The Vanderbilt protocol, developed by a multidisciplinary group of surgeons, anesthesiolo-gists, and transfusion medicine specialists, calls for the hospital blood bank to prepare packets of red blood cells, platelets, and fresh frozen plasma in predefined ratios and continue to replenish these every 20 to 30 minutes until a patient is stabilized. The ratios of blood components (plasma and platelets) are more closely approximate to that of blood being lost than what is considered “standard” transfusion practice at most trauma centers.

“We use a tighter ratio so we can stop the bleeding up front in an effort to limit the total blood products needed to reduce the amount of fluid necessary to control the patient’s cardiovascular stability,” medical student Au explained.

When trauma surgeons at Vanderbilt University Medical Center evaluated outcomes after they instituted a transfusion protocol that replaced the blood trauma patients had lost and at the same time instituted coagulation, they found that there were more unexpected survivors and fewer unexpected deaths. The survival rate was 15% higher in patients who received the exanguination protocol with an unexpected survivor rate of 20.3% (compared to only 5.7% for patients who did not receive the TEP). As well, the rate of unexpected deaths was 14% lower (2.9% vs 17.1%).