Background
Hypothermia (hi-po-THUR-me-uh) is a medical emergency that occurs when your body loses heat faster than it can produce heat, causing a dangerously low body temperature. The term “hypo” refers to less, and “thermia” refers to temperature. Normally, the core body temperature is 98.6 degrees F. Hypothermia occurs as your body temperature passes below 95 F (35 C). When your body temperature drops, your heart, nervous system and other organs cannot work correctly. Left untreated, hypothermia can eventually lead to severe heart and respiratory failure, and in some cases, death. Hypothermia is most often caused by long term exposure to cold weather or or and unexpected immersion into in the face of a cold stressor. Hypothermia, though, is not always the result of exposure to extremely cold outdoor temperatures.
History
Hypothermia has been applied therapeutically since antiquity. The Greek physician Hippocrates, the namesake of the Hippocratic Oath and arguably the world’s first modern doctor, advocated the packing of wounded soldiers in snow and ice.[3] Napoleonic surgeon, Baron Dominque Larrey recorded that officers who were kept closer to the fire survived less often than the minimally pampered infantrymen using snow and ice.[3] In modern times the first medical article concerning hypothermia was published in 1945.[3] This article focused on the effects of hypothermia on patients suffering from severe head injury. In the 1950s hypothermia established its first medical application, being used in intracerebral aneurysm surgery to create a bloodless field.[3] Most of the early research focused on the applications of deep hypothermia, defined as a body temperature between 20–25 °C (68–77 °F). Such an extreme drop in body temperature brings with it a whole host of side effects, which made the use of deep hypothermia impractical in most clinical situations.
This period also saw sporadic investigation of more mild forms of hypothermia, with mild hypothermia being defined as a body temperature between 32–34 °C (90–93 °F). In the 1950s, Doctor Rosomoff demonstrated the positive effects of mild hypothermia in dogs, after incurring brain ischemia and traumatic brain injury.[3] In the 1980s, further animal studies indicated the ability of mild hypothermia to act as a general neuroprotectant following a blockage of blood flow to the brain. In 1999, following a skiing accident Anna Bågenholm's heart stopped for more than three hours and her body temperature dropped to 13.7C, prior to being resuscitated.[4] In addition to the animal studies and Anna Bågenholm's accident, two landmark human studies were published simultaneously in 2002 by the New England Journal of Medicine.[1] Both studies, one occurring in Europe and the other in Australia, demonstrated the positive effects of mild hypothermia applied following cardiac arrest.[2] Responding to this research, in 2003 the American Heart Association (AHA) and the International Liaison Committee on Resuscitation (ILCOR) endorsed the use of therapeutic hypothermia following cardiac arrest.[5] Currently, a growing percentage of hospitals around the world incorporate the AHA/ILCOR guidelines and include hypothermic therapies in their standard package of care for patients suffering from cardiac arrest.[1] Some researchers go so far as to contend that hypothermia represents a better neuroprotectant following a blockage of blood to the brain than any known drug.[1][6] Over this same period, a particularly successful research effort showed that hypothermia is a highly effective treatment when applied to newborn infants following birth asphyxia. Meta-analysis of a number of large randomized controlled trials showed that hypothermia for 72 hours started within 6 hours of birth significantly increased the chance of survival without brain damage.[7]
Types
Hypothermia is generally classified as being either intentional (a patient’s temperature is dropped for medical reasons) or accidental. Accidental hypothermia is further divided into two categories: primary (as a result of exposure to cold) and secondary (as a result of a medical illness). Additionally, there are three classes of severity: Mild -- body temperature is 90-95 °F; Moderate -- body temperature is 86-90 °F; and Severe – body temperature is less than 86 °F.
The Oxford Companion to the Body lists four categories of hypothermia: immersion, exhaustion, urban and submersion. Immersion hypothermia is when cold stress on the body is so great that the body's heat-generating capacity is overwhelmed and the core temperature is forced down. Exhaustion hypothermia is when the body maintains the temperature until energy sources are exhausted. Then, since the heat-generating ability is reduced, even relatively mild cold exposure may cause continued cooling. Exhaustion hypothermia is the type most commonly found in mountaineers or hill walkers (The Oxford Companion to the Body). The third type, urban hypothermia, is when the cold stress has been mild but prolonged. The core temperature tends to remain normal (35°C or above) for days or weeks, with massive fluid shifts. The temperature eventually drifts down, or faster cooling is precipitated by some other factor such as a fall. This is the most usual type found in the elderly or in association with malnutrition (The Oxford Companion to the Body). Lastly, submersion hypothermia occurs when victims have been totally submerged in very cold water. Typically, submersion survival is about 3 min.
Symptoms
Shivering is your body's automatic defense against cold temperature — an attempt to warm itself. Constant shivering is a key sign of hypothermia. Signs and symptoms of moderate to severe hypothermia include: * Shivering * Clumsiness or lack of coordination * Slurred speech or mumbling * Stumbling * Confusion or difficulty thinking * Poor decision making, such as trying to remove warm clothes * Drowsiness or very low energy * Apathy or lack of concern about one's condition * Progressive loss of consciousness * Weak pulse * Slow, shallow breathing
A person with hypothermia usually isn't aware of his or her condition, because the symptoms often begin gradually and because the confused thinking associated with hypothermia prevents self-awareness. Symptoms of mild hypothermia not related to extreme cold exposure are nearly identical to those of more severe hypothermia, but may be much less obvious. Signs and symptoms of mild hypothermia may include: * Shivering * Faster breathing * Trouble speaking * Confusion * Lack of coordination * Fatigue * Increased heart rate * High blood pressure * Risk Factors
Age: The very young and very old may be less able to generate heat. The elderly with underlying medical conditions such as hypothyroidism or Parkinson's disease that limit the ability of the body to regulate temperature are less able to generate heat. Infants don't generate heat as efficiently, and with their relatively large head size compared to the body, they are at risk for increased heat loss by radiation.
Mental status: Impaired judgment and mental function can lead to cold exposure. Patients with Alzheimer's disease are prone to wander and become exposed to the elements.
Substance abuse: Alcohol and drug abuse increase the risk of hypothermia in two ways. First, impaired judgment can lead to cold exposure. Additionally, alcohol and similar drugs can dilate blood vessels near the skin (vasodilatation) and decrease the efficiency of the shivering mechanism, both of which decrease the body's ability to compensate for cold exposure.
Medical conditions: Underlying medical conditions can also lead to accidental hypothermia. Patients with hormonal abnormalities (thyroid, adrenal, pituitary), and those with peripheral neuropathy (due to diabetes or other conditions) or may be less able to feel the cold and generate a shivering response. Patients with spinal cord injuries, similarly, may not be able to adequately shiver. Patients who have suffered strokes or brain tumors may have impaired thermal regulation centers in the brain. Overwhelming infection and sepsis may both present with a lowered temperature instead of fever. People with diabetes who have very low blood sugar can appear unconscious and very cold.
Treatment
The medical methods through which hypothermia is induced break down into two categories: invasive and non-invasive.
Invasive: Cooling catheters are inserted into the femoral vein. Cooled saline solution is circulated through either a metal coated tube or a balloon. The saline cools the patient’s whole body by lowering the temperature of a patient’s blood. Catheters reduce temperature at rates ranging from 1.5 °C (2.7 °F) - 2 °C (3.6 °F) per hour. Through the use of the sophisticated control unit, catheters can bring body temperature to within 0.1 °C (0.18 °F) of the target level. This level of accuracy allows doctors to avoid many of the pitfalls associated with excessively deep levels of hypothermia.
Non Invasive: Water blankets, torso vest, leg wraps.
In these technologies, cold water circulates through a blanket, or torso wraparound vest and leg wraps. To lower temperature with optimal speed, medical professionals must cover 70% of a patient’s surface area with water blankets. Although this technique of temperature management dates back to the 1950s, it still remains in use today. The treatment also represents the most well studied means of controlling body temperature. Water blankets lower a patient’s temperature exclusively by cooling a patient’s skin and accordingly require no clinician performed invasive procedures. * The Standard Treatment * Immediate treatment is as follows: The patient's breathing should be monitored, and if it becomes dangerously slow or stops, CPR should be initiated. Rough handling or jerking of the patient should be minimized if the person is lethargic or unconscious. Re-warming should be started by applying warm compresses to the chest, neck, and groin. Hot water should not be used. Because there may be associated frostbite, direct heat should not be applied to the body. Instead, warm blankets and body to body contact may be needed as a first aid measure. The severity of hypothermia and the patient's mental status and ability to function will determine what further treatment is necessary. * How re-warming proceeds depends on the body temperature. 1) A mildly hypothermic person who is shivering may just need passive re-warming. This technique relies on the patient's own metabolism to re-warm the body. Once wet clothing is removed and the skin is dried, the patient is covered with blankets and placed in a warm room. The goal is to raise the patient's temperature by 0.5-2 °C an hour. 2) A moderately hypothermic person shows signs of confusion and is often treated first with active external re-warming and then with passive re-warming. Active external re-warming involves applying heat to the skin, for instance by placing the patient in a warm bath or wrapping the patient in electric heating blankets. Warmed intravenous fluids, warming blankets, and warmed humidified air may be provided in the hospital. 3) Severely hypothermic patients require active internal re-warming. Cardiopulmonary bypass, in which the patient's blood is circulated through a re-warming device and then returned to the body, is considered the best, and can raise body temperature by 1-2 °C every 3-5 minutes. However, many hospitals are not equipped to offer this treatment. Alternative treatment includes infusing warm fluids into the stomach or bladder, or irrigating warm solutions into the chest or abdominal cavity. * Inhalation re-warming is the only substantiated, non-invasive method of internal re-warming. It’s a simple, non-invasive technique, with low risk of complications or infections. It can be used outside a hospital by laymen and does not require much training. * Additionally, the patient should be removed from the cold environment and placed in a warm shelter away from the wind. Wet clothing should be removed and replaced with a warm, dry covering including head covering.
Other Treatment: * Routine Medical Care * Spinal precautions as necessary * Remove all wet clothing: dry patient, cover with blankets to prevent further heat loss * Maintain a warm environment * IV access * Cardiac monitoring • Oxygen as indicated • For pain from isolated frostbite, consider morphine sulfate 2 - 5 mg slow IVP for discomfort. May repeat morphine in 2-5 mg increments q 5 minutes or more up to 20 mg. • If unable to establish an IV up to 5 mg of morphine sulfate may be administered IM. May repeat in up to 5 mg increments q 10 minutes to a max of 20 mg. * Prior to the administration of morphine sulfate, and prior to each repeat dose, the patients pain and vital signs should be reassessed. The patient must have a SBP>90 mmHg, respirations>12, and awake to report pain. • In severely hypothermic patient, rough handling can precipitate ventricular fibrillation. • When checking pulses and respiratory rates, check for 60 seconds, because bradycardia and bradypnea are common in moderate to severe hypothermia * Cardiac dysrhythmias begin to develop at a core temperature of 30°C. * Ventricular fibrillation susceptibility is greatest below the core temperature of 22°C. * Bretylium (5 mg/kg initially) is recommended for any hypothermic patient manifesting significant new ventricular ectopy or frank dysrhythmia. However, bretylium has been discontinued by all manufacturers resulting in a worldwide shortage and has been unavailable to many centers since 1999. * Although the optimal dosage and ideal infusion rate for bretylium are unknown, consider prophylactic bretylium for patients with core temperatures below 30°C. * In dire circumstances, when heat packs are unavailable, rescuers can provide skin-to-skin contact with patients. * Measure core temperatures using a low-reading esophageal, rectal, or bladder thermometer. Tympanic thermometers are unreliable in a setting of profound hypothermia and should not be used. If using a rectal probe, be careful not to insert it into stool. * Determine whether a cold patient is profoundly or mildly hypothermic. Profoundly hypothermic patients present with stupor or cardiac dysrhythmia (regardless of the recorded temperature) and a core temperature of 30°C or lower. * Do not attempt resuscitation on the patient with a frozen chest where compressions are not possible. * Profoundly hypothermic patients who demonstrate cardiac ectopy may be ideal candidates for bretylium, if available. Administer an initial dose of 5 mg/kg IV (repeated at 10 mg/kg, as needed) to prevent ventricular fibrillation. Lidocaine is ineffective for treatment of hypothermia-induced dysrhythmias. * Initiate warmed, humidified oxygen; provide heated intravenous saline; and place warmed blankets or heat lamps around a hypothermic patient. * Initiate CPR for hypothermic patients who deteriorate into ventricular fibrillation. These patients also warrant immediate weight-based defibrillation (2 J/kg), along with prompt administration of high-dose bretylium (10 mg/kg).
EMS Procedures Assessment of Patient
1. Mild Hypothermia: A patient who is cold and has the following signs is considered to have mild hypothermia:
a. Alert b. Vital signs not depressed c. Vigorous shivering
2. Moderate or Severe Hypothermia – consistent with a temperature below 90 oF (32 oC). A patient who is cold and has any of the following signs or symptoms is considered to have moderate to severe hypothermia:
a. Depressed vital signs, such as a slow pulse and/or slow respiration.
b. Altered level of consciousness, including slurred speech, staggering gait, decreased mental skills, or the lack of response to verbal or painful stimuli.
c. No shivering in spite of being very cold. (Note: This sign is potentially unreliable and may be altered by alcohol intoxication.)
Basic Treatment for Hypothermia
1. Prevent further heat loss:
a. Insulate from the ground;
b. Protect from the wind, eliminate evaporative heat loss by removing wet clothing (once the patient has adequate shelter);
c. Insulate the patient, including the head and neck;
d. Cover the patient with a vapor barrier (such as a blue tarp, a large piece of plastic, large garbage bags etc.); and
e. Move the patient to a warm environment.
2. Activate the emergency medical services system to provide transport to a medical facility.
3. Do not give alcohol or permit patient to use tobacco.
4. Oxygen should be administered, if available. Oxygen should be heated to a maximum of 108°F (42°C) and humidified if possible. Heating oxygen without humidification is not an effective warming technique.
5. Splinting should be performed, when indicated, in an anatomically neutral
Community Health Aides should use the protocols for their level of EMS certification. CHAs who are not certified as EMTs should use the EMT-I protocols for cold injuries.
5
Revised 1/2005 -12-position if possible with caution to prevent additional injuries to frostbitten tissues.
C. Treatment for Mild Hypothermia
1. Treat the patient as outlined in Section B.
2. If there is no way to get to a medical facility, or if it will take more than 30 minutes for the patient to arrive at a medical facility, rewarm the patient with one or more of the following methods:
a. Vigorous shivering is a very important method for increasing heat production. Shivering should be fueled by calorie replacement with fluid containing sugars (sugar content is more important than hot drinks);
b. Do not allow the patient to drink liquids unless the patient is capable of swallowing and protecting the airway.
c. Apply heat to areas of high surface heat transfer including the underarms, sides of the chest wall, the neck and groin;
d. Place the patient in a sleeping bag and provide close skin-to-skin contact with a warm body. The patient should not be placed in a sleeping bag with another individual who is hypothermic. This method may not speed core warming in a vigorously shivering patient but will slowly warm a non- shivering patient;
e. Consider a warm shower or a warm bath for the patient, if he or she is alert and mobile; and
f. Mild exercise, such as walking or stepping up and down on an object, will produce heat and may be helpful. This should only be conducted after the patient is dry, has had calorie replacement, and has been stable for at least 30 minutes.
D. Treatment for Moderate to Severe Hypothermia with Signs of Life (Pulse or Respirations):
1. Treat patients who are hypothermic very gently (do not rub or manipulate extremities, or attempt to remove wet clothes without cutting them off).
2. Obtain a core temperature as trained and authorized.
3. Treat the patient as outlined in sections B and C above with the following exceptions:
a. Do not allow the patient to sit or stand until rewarmed (do not put in shower or bath).
b. Do not give the patient oral fluids or food. c. Do not attempt to increase heat production through exercise, including walking. 4. Reassess the patient's physical status periodically.
5. Transfer to a medical facility as soon as possible.
E. Treatment for Severe Hypothermia with No Life Signs: Revised 1/2005 -13-
1. Treat the patient as outlined in Section B. Handle very carefully.
2. Check for respiration and signs of circulation for 60 seconds. If the patient is not breathing and has no signs of circulation, give 3 minutes of ventilation. Recheck for respiration and signs of circulation for a further 60 seconds. If the patient still is not breathing and has no signs of circulation and there are no contraindications as listed in Appendix C, continue ventilations. Start chest compressions only if the patient will not receive definitive care within 3 hours (see Q, page 6).
3. Use mouth-to-mask breathing or bag-valve-mask (BVM) with oxygen when giving ventilations. Care must be taken not to hyperventilate the patient as hypocarbia can reduce the threshold for ventricular fibrillation in the cold heart.
• When using a BVM, ventilate the hypothermic patient at 6 breaths per minute (half the normal rate).
• When using mouth-to-mask ventilations to the hypothermic patient, give 12 breaths per minute.
4. If the rescuers are authorized to use an automated external defibrillator and the device states that shocks are indicated, one set of three stacked shocks should be delivered. If the core temperature of the patient cannot be determined or is above 86 °F (30 oC), treat the patient as if normothermic. If the patient's core temperature is below 86 °F (30 oC), discontinue use of the AED after the initial three shocks until the patient’s core temperature has reached 86 °F (30 oC).
5. If CPR has been provided in conjunction with rewarming techniques for more than 30 minutes without the return of spontaneous pulse or respiration, contact the base physician for recommendations. If contact with a physician is not possible, Emergency Medical Technicians may consider terminating the resuscitation in 60 minutes in accordance with AS 18.08.089 and local protocols (see page 6, General Point Q).

The EMS Protocol is outlined in the following diagram:

Case Studies
Nearly 200,000 out-of-hospital incidents of sudden cardiac arrest occur among U.S. residents each year. For every minute care is delayed, survival is decreased.
"We used to always think that when the brain didn't get enough oxygen, cells died, but we think now that it's more that the brain is stunned," said Dr. Matt Sutter with Emergency Medicine of Indiana. Sutter works at the Emergency Room at Lutheran Hospital in Fort Wayne, Ind., and is among a growing number of emergency doctors using a treatment called moderate therapeutic hypothermia to cool the body of a patient when sudden cardiac arrest is witnessed.
By cooling the body quickly to between 90 and 94 degrees Fahrenheit -- normal body temperature is 98.6 degrees -- the body's metabolic processes are slowed. Cellular breakdown and the release of toxic chemicals are stymied.
"The cooling slows the process, allowing injured, but not dead, cells to get healthy," Sutter said.
The treatment was first used at Lutheran Hospital in October 2006, when Eric Jones, then 45, was brought to the hospital by EMS after he collapsed at a Fort Wayne, Ind., fitness center.
"I had been running on the treadmill. When I exercise I tend to push myself pretty hard," Jones said. A fitness instructor began CPR and used an automated external defibrillator, which the club had just purchased. Although his heart restarted, "I wasn't breathing on my own for about 10 to 13 minutes," he said. Emergency responders used a bag to force air into Jones, and he was taken to Lutheran, where doctors said his prognosis looked grim.
"I was posturing," which is a reflexive arching of the body due to lack of oxygen to the brain. "That was pretty scary to my family," said Jones, who is married and has three daughters. "The doctors actually told my wife that she should probably call all my siblings and my family and have them all come in." At the time, hypothermia for cardiac patients was a fairly new concept, and Lutheran had on order a device called the Arctic Sun, which pumps coolant into tubes within pads that are placed around the patient's body. Some methods of cooling the body involve putting the cooled saline into the femoral artery.
A target temperature is set on the control module, and the lowered temperature is maintained for 24 to 36 hours, on average, to allow the healing of the damaged or stunned cells in the brain. The same concept explains why people, particularly children, who drown in cold water have a greater chance of revival than if they drowned in warmer water.
Because Lutheran had therapeutic hypothermia protocols in place but not the Arctic Sun, Sutter used special cooling blankets to bring Jones' temperature down. He was kept sedated and his body slowly returned to normal temperature.
"My family was on pins and needles," Jones said, recalling how they waited hopefully but cautiously while the new treatment was used.
In just five days, he was home from the hospital. His main problem was short-term memory loss but that resolved in a few weeks. Doctors discovered the cardiac arrest was due to an electrical problem within his heart, not the normal cause, which is blockage in an artery of the heart.
"I'm so grateful that they had the opportunity to use the cooling blanket on me," Jones said. Since April 2007, Lutheran has used the Arctic Sun on 28 patients, with good outcomes for many. Sutter cautions the treatment is not for patients whose cardiac arrest is not witnessed or who have other medical conditions that lead to the heart's stoppage. But several studies reported in medical journals show good outcomes ranged from 41 percent to 68 percent better for patients treated with hypothermia compared to those given normal supportive care.
Parkview Hospital in Fort Wayne is also now using Arctic Sun and for Mike Bechdol, 57, of Angola, Ind., it may well have made the difference between his celebrating the holidays this year with his family, fully functioning and alert, and not being able to talk and play with his children and grandchildren -- or not even being here at all.
It was during hip replacement surgery Oct.1 that Bechdol's heart suddenly stopped. Doctor's shocked it back into action and sent him to Parkview's ICU, where he was hooked up to the hypothermia equipment.
"According to my wife, I shaked and rattled and rolled," he said of the initial response to the quick cooling, although medication was used to relieve those effects. Like Jones, he had some short-term memory problems soon after, but today he says, "I'm amazed ... to think I was in a coma and brought back without any problems. When I did come out of it, my wife claimed I knew everybody. It truly could have gone the other way. I'm quite thankful." Mike GeRue is director of the neuroscience service line at Parkview Hospital, where hypothermia has been used on more than 50 cardiac arrest patients so far.
The treatment is also being used on traumatic brain injury and spinal cord patients in some hospitals. Parkview Research Center is considering using it on stroke patients as part of a study, he said.
Buffalo Bills tight end Kevin Everett brought national attention to the treatment after it was successfully used on him following a spinal cord injury incurred during a September 2007 game.
"It's a really hot topic," Sutter said of the potential uses for hypothermia. The most gratifying news he hears from nurses, he says, is that "a lot of people are waking up who they never expected to wake up." * WHAT ROLE WILL HYPOTHERMIA TREATMENT IN EMS PLAY IN THE FUTURE: * The recently discovered benefit of medically induced hypothermia (known as therapeutic hypothermia) will have a major impact on EMS workers. Rather than simply treat accidental hypothermia, they will now be starting the process of induced intentional hypothermia. The New York Fire Department EMS expects to administer hypothermia therapy to more than 6,000 patients in the next year. * The remainder of this report deals solely with therapeutic hypothermia. It is a major change/advancement in EMS care. * * WHAT THE FUTURE WILL REQUIRE: * The future is ever changing and the equipment for the EMS industry will have to change with it. In the case of what equipment the EMS industry will need for the future, we as a group think the vehicles will need a cooler to store ice packs and to cool the saline solution. The vehicles should also have cots that have the ability to cool or heat the body temperatures of their patients. Cots made of gel/foam combination should do well in providing the ability to change body temperature. Cooling blankets would also be helpful to assist with therapeutic hypothermia. Additionally, warm-air units should be available in each ambulance to treat accidental hypothermia patients. * * WHY THERAPEUTIC HYPOTHERMIA MAY BE BENEFICIAL: * By cooling the body quickly to between 90 and 94 degrees Fahrenheit (normal body temperature is 98.6 degrees) the body's metabolic processes are slowed -- cellular breakdown and the release of toxic chemicals are stymied. * The goal of induced therapeutic hypothermia is to decrease the patient’s body temperature to 32-34oC, and then maintain that for 24 hours. After that time period, the patient will slowly be re-warmed, over 6-8 hours. Cooling can be achieved several different ways: cooled saline infusions, cooling blankets such as the Arctic Sun, or ice/cold packs. The majority of cardiac arrests occur outside of the hospital. While many emergency medical technicians are able to resuscitate patients, many patients never survive to be discharged from the hospital. Of those patients surviving to discharge, the majority incur neurological impairment. Proper application of mild therapeutic hypothermia is shown to improve neurological outcomes