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Hypothermia

Hypothermia

Hypothermia, defined as a core body temperature less than 95 °F(35°C) occurs

when heat loss exceeds the body’s heat production. (Ruffolo p.47) Thermal stability in

humans depends on the body’s ability to adapt to changes in internal and external

temperatures. Heat is transferred throughout tissues and fat, and is released at a rate

directly related to the temperature of the environment through radiation, conduction,

convection, and evaporation.

Hypothermia is typically seen as a bad thing; however, various studies have been

proving it to be very useful. Traumatic brain injury initiates several metabolic processes

that can exacerbate the injury. There is evidence that hypothermia may limit some of these

deleterious metabolic responses. In a randomized controlled trial researchers compared

the effect of moderate hypothermia and normhypothermia in 82 patients with severe

closed head injuries (score of 3 to 7 on the Glasgow Coma Scale) The patients assigned to

hypothermia were cooled to 33 degrees C an average of 10 hours after injury, kept at 32

degrees to 33 degrees C for 24 hours, and then re-warmed. A specialist in physical

medicine and rehabilitation who was unaware of the treatment assignments evaluated the

patients 3, 6, and 12 months later with the use of the Glasgow Outcome Scale. The

demographic characteristics, causes, and severity of injury were similar in the hypothermia

group and the normothermia groups. At 12 months 62% of the patients in the

hypothermia group and 38% in the normothermia had good outcomes (moderate, mild, or

no disabilities). The researchers concluded that "Treatment with moderate hypothermia for

24hours in patients with severe traumatic brain injury and coma scores of 5 to 7 hastened

neurological recovery and may have improved the outcome. (Marion et all)

Two studies done (one in Australia and the other in Europe) showed the

therapeutic value in survivors cardiac arrest. In the Australian study, which involved 77

patients who remained comatose after the restoration of spontaneous circulation, 49% of

those treated with hypothermia were discharged home or into a rehabilitation facility

compared to the 26% of those not treated with hypothermia. There were no significant

differences between the 2 groups with respect to the frequency of adverse events. The

out come of the European study, which involved 9 center in 5 countries and had a larger

number of patients, were similar. Taken together, the findings in these trials are important,

because in the United States so far, permanent brain damage after cardiopulmonary-

cerebral resuscitation causes many delayed deaths and is seen in about 10to 30 percent of

survivors of out-of hospital cardiac arrest. The fact that 2 studies yielded similar results

makes the important conclusions even more compelling. The rationale for the use of

therapeutic hypothermia is complex. Spontaneous uncontrolled hypothermia start with

potential deleterious shivering, thermo genesis , catecholamine release, and

vasoconstriction, there as controlled hypothermia is potentially beneficial. Therapeutic

hypothermia after cardiac arrest, as used in the 2 stories above, is directed at mitigating

neurological injury. Temperature levels are important; mild hypothermia (33°C to 36°C)

may be most effective, and is simple and safe. Moderate hypothermia (28°C to 32°C) can

cause arrhythmias or even ventricular fibrillation and if prolonged, can lead to

coagulopathy and infection. The timing and duration are important; mild hypothermia

should be initiated as soon as possible after resuscitation, but even when delayed for a few

hours, mild hypothermia has been shown to have some benefits un animal models of

cardiac arrest. Mild hypothermia induced in patients for 12 hours, as in the Australian

study, or 24 hours as in the European study, does not appear to have the putative

complications of moderate hypothermia.(Safar, p.612)

In another study, involving 275 patients(137- hypothermia and 138

normothermia), there was a similar outcome once again in favor of hypothermia. 55% of

the patients in the hypothermia group had favorable neurological outcomes compared to

the 39% in the normothermia group. (Holzer p.552) The hypothermia patients in this

study all received standard intensive care, as did the normothermia group. The

hypothermia group was then induced by intravenous administration of midazolam (.125

mg per kilogram per hour initially) and fentanyl (.002 mg per kilogram per hour initially).

The doses were adjusted as needed for 32 hours . To prevent shivering, paralysis was

induced by the administration of pancuroniam. (Holzer. 551)

Another study found different results. Their conclusion of the study is as follows.

"Treatment with hypothermia, with body temperature reaching 33°C within 8 hours after

injury, is not effective in improving outcomes in patients with severe brain injury." (Clifton

et all, p.556) The differences in this study included a wider age range (16 to 6). They also

used application of ice, gastric lavage with iced fluids, and the use of room temperature

air in the ventilator circuit to induce hypothermia. (Clifton at all, p 557)

Children recover rapidly from accidental and therapeutic hypothermia, say

American clinicians. Their re-warming process is two to three times faster compared to

adults. Children lose body heat faster and cool quickly because of their large surface area

in comparison to their metabolic rate. Their re-warming rate is a combination of cutaneous

heat transfer action plus metabolic heat production which is divided by body mass.

Researchers consequently tested the hypothesis that the forced-air re-warming is inversely

related to body size. Participants included infants, children and adults, scheduled for

hypothermic neurosurgery, who were given isoflurane, nitrous oxide and fentanyl

anesthesia. All fluids were warmed to 37 degrees centigrade and surrounding temperature

maintained at 21 degrees centigrade. A full-body forced air cover of the appropriate size

was placed over patients. By setting the heater to low or ambient temperature, it reduced

the core temperature to 34 degrees centigrade in time for the dural opening. This

temperature was maintained for an hour by adjusting the blower temperature. The forced

air heater temperature was then set to high ~43 degrees centigrade. The process of re-

warming was continued for the duration of surgery, and post operatively, until the core

temperature exceeded 36.5 degrees centigrade. Linear regression determined the re-

warming rate in each individual patient. (Rose)

CHICAGO, IL -- December 17, 1997 -- Small reductions in brain temperature

following birth can have a long-lasting neuroprotective effect for newborns who have

difficulty establishing respiration after delivery, according to the journal of the American

Academy of Pediatrics. John Wyatt, F.R.C.P., University College London Medical School,

London, England, and Marianne Thoresen, D.M., Ulleval University Hospital, Oslo,

Norway, report studies done in this decade confirm the results of research dating back to

the 1950s on the use of hypothermia treatment for at-risk newborns. In one of these early

studies 65 infants who were born unresponsive were immediately treated in a specially-

constructed cold water bath to lower body temperature. Of these infants, 52 survived and

none showed any evidence of cerebral palsy. The commentary suggests the rapid cooling

of hypothermia treatment allows for prolonged survival, giving a newborn\'s cerebral

oxygen supply and demand an opportunity to return to balance. Other studies detailed in

the commentary have also shown brain hypothermia may prolong the therapeutic window

for infants born with neurological difficulties following oxygen shortage during delivery,

allowing other medications time to work. Despite potential negative side effects and the

need for large clinical trials to determine optimal timing and duration of treatment, the

authors feel the use of brain hypothermia in treating some infants with neurological

difficulties is currently the most promising option for a clinically feasible neural rescue

therapy. (docguide.com)

Purpose Statement

To Prove that Hypothermia is useful as a medical device.

· Hypothermia can help reduce the neurological effects of brain injury.

· Hypothermia can improve the outcome for cardiac arrest patients.

· Lowering the brain temperature can better the outcome for at-risk newborns.

Research Questions

· How does induced hypothermia effect the neurological outcome of people who

have had serious brain injury?

· Can hypothermia improve the outcome after cardiac arrest?

· Will lowering the brain temperature of newborns, born with respiratory difficulty,

help their chances of survival?

Hypothesis

· I hypothesize that inducing hypothermia after trauma to the brain will help

improve the success of recovery.

· I hypothesize that the induction of hypothermia after cardiac arrest with aid in

the neurological recovery of the patient.

· I hypothesize that lowering the brain temperature of newborns with respiratory

difficulty will have neuroprotecting effects for the newborn.

Importance of this Study

The findings of this study could have a great impact on the future of medical

treatment. Especially emergency medicine. This study could better the care of trauma

patients, improving their life. If my hypothesis is found to be true there new ways of

protecting the human brain could be developed, so that people can have more normal lives

after treatment of their trauma. Many brain injury, cardiac arrest, and stroke victim never

return to a normal state after their trauma. Hypothermia may be able to give these people

a chance at normal living. This study is also important in improving the outcome for

neonatal emergencies. Many children survive difficulties at birth, but must endure

suffering for the rest of their lives due to complication. If this study was to prove in favor

of hypothermia there may be many developments to preserve the brain function of

newborns during their treatment.

Assumptions

· We may not know the complete medical history of all patients

· There will be various degrees of brain trauma

· Causes of cardiac arrest may not be known

Research and Design

Hospitals and Trauma Centers must be selected to conduct the study in. Doctors

will have to be trained to perform the procedures and to record their findings. Patients will

be induced with hypothermia by various methods in order to find the best possible method.

Patients will be left in hypothermia from 12 to 32 hours to find the most beneficial length

of hypothermia. Follow ups must be down on the hypothermia group as well as on a

normothermia group to indicate which group had a better outcome.

Delimitations

Patients of all ages, and of both genders are needed for study. However, consent

must be obtained. Results will be categorized by age and by type of trauma.

Limitations

Complications of study may include: malfunction of equipment, deaths of patients,

lack of participants, prior treatment of patient, and unknown medical factors of patient.

All of which can hinder the accuracy of results.

Definitions of terms

Radiation is the transfer of heat through the air from a warmer to cooler area. For

example, when patients are left uncovered with large surface areas of skin exposed.

Radiation typically results from an exposed head and can be responsible 55% to 65% of a

patients body heat loss. (Ruffolo p.48)

Conduction occurs through direct contact with cooler objects. It occurs when

patients are in contact with metal carts the ground or fluids. (Ruffolo p.48)

Convection refers to the transfer of heat by movement of air or liquids over skin.

Drafts, irrigation fluids, preparation solution, or baths can contribute to heat loss. Ruffolo

Evaporation is the transfer of heat to the air from moist skin or mucous

membranes. It occurs through wet skin, open body cavities and the respiratory tract.

Bibliography:

Ruffolo, Daria. www.rnweb.com. Vol. 65 No. 2. February 2002

Marion, DW et all. "Treatment of traumatic brain injury with moderate hypothermia", University of Pittsburgh Medical Center.

Safar, Peter & Patrick Kochanek. "Therapeutic Hypothermia After Cardiac Arrest". New England Journal of Medicine, February 21, 2002 p.612-613

Holzer, Michael. "Mild Therapeutic Hypothermia To Improve The Neurologic Outcome After Cardiac Arrest." New England Journal of Medicine, February 21, 2002 p.549

Clifton, Guy et all. "Lack of Effect of Induction of Hypothermia After Acute Brain Injury" New England Journal of Medicine. February 22, 2002. p.556

Rose, Victoria. "Children Recover Faster Than Adults From Accidental Or Therapeutic Hypothermia". www.docguide.com. July 23, 2001

Unknown Author, "Reducing Brain Temperature May Benefit At-Risk Newborns" http://www.pslgroup.com/dg/4E73E.htm, December 17, 1997

Source: Essay UK - http://www.essay.uk.com/coursework/hypothermia.php



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