We don't know why he made this observation, but the father of Western medicine, Hippocrates, recommended packing wounded soldiers in snow or ice.1 Centuries later a surgeon serving under Napoleon noted wounded soldiers closer to the campfire had lower survival rates than those housed farther from the warmth.2 In modern times, physicians observed supposed drowning victims in very cold water were revived with minimal neurological damage.1
So through war stories, anecdotes and medical research, a new protocol - therapeutic hypothermia - was developed. Bolstered by a 2005 endorsement from the American Heart Association and the International Liaison Committee on Resuscitation, the protocol is implemented following cardiac arrest in more than 350 hospitals across the country. About one third of U.S. hospitals offer this treatment.3
One of the country's busiest therapeutic hypothermia programs can be found at Texas Health, according to Allison Snyder, MSN, APRN, ACNS-BC, CCRN, clinical nurse specialist for the cardiovascular division at Texas Health Harris Methodist Hospital Fort Worth, Fort Worth, TX.
In 2006, several facilities in this 16 acute-care hospital system began offering the therapy. To date the procedure has been performed more than 250 times.
If a Texas Health facility doesn't have a fully operational therapeutic hypothermia program, it is capable of commencing the procedure and transferring the patient to a system facility that does. With a success rate of 18-22 percent - the national average is 20 percent - the therapy requires highly skilled nurses "who know the protocol backwards and forwards, inside and out," said Lynette Campbell, BSN, RN, CCRN, quality supervisor, critical care unit at Texas Health Harris Methodist Hospital Hurst-Euless-Bedford (HEB), Bedford, TX.
Cooling the Body
What exactly is this therapy that Texas Health critical care nurses must master?
Therapeutic hypothermia, sometimes called protective hypothermia, is the process of cooling the body down - inducing mild hypothermia (temperatures of 32-34º C or 90-93º F) - to reduce ischemic injury to tissue. It is indicated when a patient's brain has been oxygen-starved for a period of time, usually due to cardiac arrest.
"Any time the heart is not pumping, the brain, which needs oxygen and blood, is deprived," explained Margaret Markey, BSN, RN, CCRN, unit manager for the 18-bed critical care unit at Texas Health HEB, where therapeutic hypothermia is performed. "And when the brain is deprived, cells swell, creating brain damage."
Based on research such as the Hypothermia after Cardiac Arrest Study, published in the New England Journal of Medicine in 2002, cooling provides significant improvement "in functional recovery at hospital discharge and lower 6-month mortality rate when compared with patients who were not cooled."1
The protocol is so delicate it requires 1-to-1 nursing - two nurses to one patient at the start of the process. That is hands-on and up-front-and-center nursing at all times, relying on nurses' strong diagnostic and observational skills, Campbell said. A degree too cold or cooling too rapidly can cause irreversible adverse reactions. All patients are unconscious during the 24-48 hour protocol.
Not all Texas Health patients are eligible to receive this therapy. Inclusion criteria can be loose, as it is at Texas Health HEB, or tight, as it is at Texas Health Fort Worth - both developed through practical experience with their patient population.
As Markey explained: "We had strict inclusion criteria at HEB; however, in 2007 a 21-year-old man was hit in the chest by a baseball that stopped his heart," she said. "No one did CPR on the field, which was 104º F. By the time they resuscitated him he had no neurological function. We began preparing to talk with his family about the possibility of eventual brain death."
Markey said the family had read about therapeutic hypothermia and begged "us to do it. We acquiesced; the young man woke up and is doing well now. His story has been all over the news. After that we threw out all exclusion criteria and now evaluate each patient individually."
At Texas Health Fort Worth, Snyder explained inclusion criteria includes cardiac arrest with return to spontaneous circulation; Glasgow Coma Scale < 5; an intubated patient on required ventilation and a BP of at least 90 spontaneously or with vasoactive drugs or fluids. "Quite a few of our patients have been on dialysis," Snyder commented.
Exclusion criteria at Fort Worth includes: Any patient with a known terminal illness; with existing bleeding problems or coagulopathy; who is baseline hypothermic upon admission (< 30º C or 86º F); or is comatose for a reason other than cardiac arrest.
How Cooling Works
The equipment needed to perform this delicate procedure is surprisingly simple, depending on which process a hospital adopts.
"We use disposable cooling blankets and vests (positioned above and below the patient) and chilled IVs of normal saline (we keep saline in the refrigerator at all times to be prepared)," Markey said. "There are other ways of doing this such as inserting a central catheter in the main vein, cooling the blood and returning it to the body. However, that "Netherlands procedure," is invasive and has a high rate of infection.
"You can also use ice bags or cold wraps, which we use in the ED as patients are transported up to us or to the cath lab," she continued. "Cooling can go on simultaneous to catheterization."
Markey pointed out local EMS crews are being trained to begin the protocol in transit using ice bags.
"Every patient is different in their ability to get to the 91 or 92 degrees recommended, but we administer an average of 5-6 liters of saline," she said.
Pharmacologic needs can include busporine and meperidine, to help reduce shivering if it occurs; morphine or fentanyl, if an analgesic is needed; and midazolam or propofol for sedation.
The Critical Nursing Role
Besides medication and equipment, essential to the process are well-educated nurses and respiratory therapists. Because of the high acuity of these patients a nurse must have at least 1 year's experience to train for the protocol, said Snyder, at Texas Fort Worth's 25-bed cardiovascular unit.
Education includes the pathophysiology of hypothermia, medications, contraindications and counseling. "What we found was the chaplain needed to be included in training our nurses," Snyder told ADVANCE. "Patients are very compromised by the time they come to the ICU. It is very hard on staff because the acuity is so high, and so many of these patients die. The staff needed help with death and dying issues, as well as the families of patients undergoing therapeutic hypothermia."
One thing nurses are trained to watch for is shivering. While it is the body's best defense against cold, it is actually harmful during this protocol. "You have to stay on top of where you want the patient to be," explained Campbell, who is a front-line nurse as well a supervisor.
"Shivering most often occurs in the first 2-3 hours of the process," Markey said. "Once the body reaches 90-92 degrees there is no shivering."
"When shivering occurs, we adjust medications," Snyder said. "We don't use paralytics as our primary control because it can interfere with the waking process. It is used after other options have failed."
Time management is critical for nurses monitoring this therapy. "The rewarming phase is the most challenging part of the process because people don't warm up at the same rate," Campbell said. "Everyone reacts differently. There doesn't seem to be any correlation between young and old, athletic and sedentary, heavy or thin."
While the Texas Health units have had great successes, they have had failures. Both Markey and Campbell pointed out that even when a patient is lost, therapeutic hypothermia gives the family time to adjust to the situation.
"In that 48-hour period when the patient is undergoing the protocol, the family goes through grief, anger, despair," Campbell said. "The protocol gives them hope of survival, but it also gives family from out of town a chance to arrive and a chance for all to say goodbye."
Still "the successes we have had are what keeps us going," Markey stressed.
Snyder agreed. "Our successes have fed enthusiasm for this protocol," she said. "We treated a firefighter who is now back to work. It doesn't get any better than that."
1. Adler, J. & Peter, K. (2011). Therapeutic hypothermia. Retrieved Oct. 26, 2011 from the World Wide Web: http://emedicine.medscape.com/article/812407-overview
2. Wikipedia. (2011). Therapeutic hypothermia. Retrieved Oct. 18, 2011 from the World Wide Web: http://en.wikipedia.org/wiki/Therapeutic_hypothermia
3. Penn Medicine. (2010). Reversing death: Therapeutic hypothermia. Retrieved Oct. 26, 2011 from the World Wide Web: http://news.pennmedicine.org/inside/2010/07/reversing-death-therapeutic-hypothermia.html
Gail O. Guterl is a frequent contributor to ADVANCE.