Induced Hypothermia Shows Promise in Treating Cardiac, Neurotrauma Patients
There are several patient warming and cooling devices available for temperature management, but the practice of induced hypothermia was what made national headlines this past fall with the treatment of the major spinal injury of Buffalo Bills' football reserve tight end Kevin Everett.
Everett severely dislocated his cervical spine Sept. 9, when trying to make a tackle during the Buffalo Bills’ season opener against the Denver Broncos. Kevin Gibbons, M.D., the supervisor of neurosurgery at Buffalo's Millard Fillmore Gates Hospital, said at a press conference Sept. 12 the injury made Everett functionally paraplegic, and he was unsure if Everett would recover from the paralysis. The C3/4 level injury was considered life-threatening. However, a couple days following surgery and the use of induced hypothermia, Everett began moving his extremities. As of mid-December Everett was walking again.
Reducing the body temperature to about 33°C/91°F can be used to help prevent neurological damage from swelling and can be used to help treat severe trauma, cardiac arrest and stroke patients. Experts say it slows the body’s metabolic rate to buy time for doctors, reducing brain damage, swelling, pain, and helps accelerate the healing of damaged tissue.
Induced hypothermia can be accomplished by several methods, including rapid infusion of ice-cold intravenous fluids; cooling of internal organs with ice-cold water; cooling through evaporation; intravascular cooling using specialized vascular catheters; external cooling with ice packs or special cooling blankets; and by preventing excess heat generation by using medication.
In Everett’s case, doctors said cooled saline was administered in the ambulance on the way to the hospital. Buffalo Bills' orthopedic surgeon Andrew Cappuccino, M.D., said in a press conference Everett was also cooled after surgery to alleviate the pressure on the spinal cord.
Following surgery Everett’s temperature rose drastically and his doctors were afraid this would cause neurological injury. His doctors decided to induce hypothermia using an Alsius CoolGard 3000 machine, which uses an intravenous central catheter circulating cooled saline in a closed loop system. However, with the decision to cool Everett came additional ICU management problems, Dr. Gibbons said. This included marked fluctuation in his electrolytes, difficulty managing the ventilator and the need to keep Everett heavily sedated. Dr. Gibbons said this was carried out over the next 24 hours
When sedation was lifted, Dr. Gibbons said Everett showed clear improvement in the motor function in his legs, the ability to push his knees together and apart, and wiggle his toes. He also had slight movement in his ankles and the ability to kick out his lower leg against gravity. He regained the ability to slightly extend his elbow and had a hint of ability to flex his arm. At that point doctors decided to begin warming him over the next 12 hours.
“[Induced hypothermia] is also utilized in sudden cardiac death; it is utilized prophylactically in some centers for the elective treatment of major spinal reconstructive surgery,” Dr. Cappuccino said at the press conference. “But our literature has told us that in the presence of an acute spinal cord injury, if we can by any means possible lower the core temperature of the body, there may in fact be... a sparing effect on the inflammation and otherwise cell destruction of the spinal cord. It seemed like a simple and straightforward application, which I was willing to pull out all the stops to try to help this young man.”
Induced hypothermia may have helped Everett’s recovery, but science cannot be proven based on one man's case, said therapeutic hypothermia expert Dr. Kees Polderman, M.D., Ph.D., vice chairman in the Department of Intensive Care at University Medical Center Utrecht in the Netherlands.
Dr. Kees said hypothermia aids the body by slowing down the cascade of reactions that leads to brain cell death following oxygen deprivation. He said cooling also decreases the body's inflammatory response.
“It helps give a lot of extra time for the doctor,” Dr. Kees said, but admitted, “Using it for spinal cord injuries is pretty experimental.”
He said studies show hypothermia's effectiveness in preventing brain damage in babies with oxygen depravation and in resuscitated cardiac arrest patients. Dr. Kees said evidence in animal studies show effectiveness in treating spinal injuries, but little human research has been done.
Dr. Kees said the use of hypothermia is expanding and may eventually be used as a common treatment for spinal and head trauma patients, but admits much more research needs to be done.
“I think we will be moving in there, but we are not there yet,” he said.
“(Everett) had a phenomenal outcome,” said Carmelo Graffagnino, M.D., a neurologist at Duke University Hospital who is active with hypothermia research. “Induced hypothermia is a neuroprotectant.”
He too agrees while there is some evidence hypothermia aids in treating mild to medium damage to the spinal cord, few clinical studies exist to show its true effectiveness. He said people who are temporarily paralyzed by a spinal injury have recovered without this intervention.
“It's too early to recommend all patients with spinal cord injuries should be treated with hypothermia,” Dr. Graffagnino said.
Dr. Graffagnino uses the Alsius Coolguard, the same device used on Everett. He said it has the advantage of acting as a central catheter and cools and warms much faster than other methods.
“It's a good workhorse for us, because we can deliver medication and monitor the venous pressure while cooling a patient,” Dr. Graffagnino said.
He has used cooling blankets that circulate water or jell and said they are easy to use and cheaper to purchase. But, Dr. Graffagnino found he usually needed two cooling blankets, the blankets may cause frostbite if left unchecked, and access to the patient is limited because they are covered. He also uses the Arctic Sun temperature transfer pad device by Medivance and likes it because of its temperature feedback loop provided by a urinary catheter, but said it is slower than the Coolguard.
Dr. Kees said the different cooling methods have not been compared very well in studies. He said catheter cooling and warming devices work the fastest and allow easy adjustment of the patient's temperature, but require a physician to insert the device.
Dr. Kees uses Cincinnati Sub-Zero's (CSZ) microprocessor controlled, Blanketrol cooling/warming therapy system and the Arctic Sun. Both systems use water circulating through heat transfer pads.
“(The Blanketrol) is quite easy to use and a nurse can do it, because it does not require a catheter to be inserted,” he said.
The cooling pads take time to lower a patient's temperature, but Dr. Kees said a combination of methods can be used to speed the process, including the injection of cold intravenous fluids.
Despite the variety of equipment available to cool patients, Drs. Graffangnino and Kees both said the simplest method that can be used immediately anywhere is a refrigerated saline IV. Dr. Graffagnino recommends a temperature of 2°C at 10cc per kilogram pumped quickly into the patient. They said this method is good for the short term, but specific cooling devices are better for use over long periods of cooling to maintain a consistent temperature.
The newest cooling device to hit the market in January is the RhinoChill System from BeneChill, which uses a battery-powered, portable, noninvasive probe inserted into the nasal cavity. RhinoChill recently received the CE Mark for commercial sale in Europe.