disorders of temperature regulation bryan e. bledsoe, facep midlothian, tx

Disorders of Disorders of Temperature Temperature RegulationRegulation

Bryan E. Bledsoe, FACEPBryan E. Bledsoe, FACEPMidlothian, TXMidlothian, TX

Temperature RegulationTemperature Regulation

HypothermiaHypothermia HyperthermiaHyperthermia

Heat CrampsHeat Cramps Heat TetanyHeat Tetany Heat ExhaustionHeat Exhaustion Heat SyncopeHeat Syncope Heat StrokeHeat Stroke

FeverFever


Humans are Humans are warm-blooded warm-blooded mammals who mammals who maintain a maintain a constant body constant body temperature temperature ((euthermiaeuthermia).).


Temperature Temperature regulation is regulation is controlled by controlled by the the hypothalamhypothalamusus in the in the base of the base of the brain.brain.


The hypothalamus functions as The hypothalamus functions as a thermostat for the body.a thermostat for the body.

Temperature receptors Temperature receptors (thermoreceptors) are located (thermoreceptors) are located in the skin, certain mucous in the skin, certain mucous membranes, and in the deeper membranes, and in the deeper tissues of the body.tissues of the body.


When an increase in body temperature When an increase in body temperature is detected, the hypothalamus shuts is detected, the hypothalamus shuts off body mechanisms that generate off body mechanisms that generate heat (for example, shivering).heat (for example, shivering).

When a decrease in body temperature When a decrease in body temperature is detected, the hypothalamus shuts is detected, the hypothalamus shuts off body mechanisms designed to cool off body mechanisms designed to cool the body (for example, sweating).the body (for example, sweating).


Body Temperature = Thermogenesis–Heat Body Temperature = Thermogenesis–Heat LossLoss


Basal Metabolic Rate:Basal Metabolic Rate: The metabolism that occurs The metabolism that occurs

when the body is completely at when the body is completely at rest.rest.


Metabolic Rate:Metabolic Rate: The body continuously adjusts The body continuously adjusts

the metabolic rate in order to the metabolic rate in order to maintain a constant CORE maintain a constant CORE temperature.temperature.


Normal body Normal body temperature is temperature is approximately approximately 3737º º C (98.6C (98.6º º F).F).

However, what However, what is normal for an is normal for an individual may individual may vary somewhat.vary somewhat.

HypothermiaHypothermia

Definition of HypothermiaDefinition of Hypothermia:: CLASSIC DEFINITION: A state of low CLASSIC DEFINITION: A state of low

body temperature, specifically a low body temperature, specifically a low CORE temperature (< 35CORE temperature (< 35º C or < 95º º C or < 95º F)F)..

ALTERNATIVE DEFINITION: It is best ALTERNATIVE DEFINITION: It is best defined as the unintentional decrease defined as the unintentional decrease of around 2of around 2º C (3.6º F) from the º C (3.6º F) from the “normal” CORE temperature“normal” CORE temperature


What is the What is the CORE CORE temperature?temperature? The deep The deep

internal internal temperature of temperature of normothermicnormothermic humans.humans.


How is the CORE How is the CORE temperature temperature measured?measured? There is little variance in There is little variance in

CORE temperature CORE temperature because of perfusion.because of perfusion.

Esophageal and Esophageal and tympanic temperatures tympanic temperatures are essentially the same are essentially the same as the temperature of as the temperature of the pulmonary artery.the pulmonary artery.


In steady-state In steady-state conditions, the conditions, the rectal rectal temperature is a temperature is a good index of good index of CORE CORE temperature.temperature.


Oral Oral temperature is temperature is an excellent an excellent index of CORE index of CORE temperature, temperature, provided the provided the mouth is kept mouth is kept closed.closed.


The type of The type of temperature temperature measurement measurement utilized is less utilized is less important than important than using the same using the same device and device and measurement site to measurement site to detect trends.detect trends.

Thermometer must Thermometer must be able to read low be able to read low temperatures.temperatures.

Heat loss Heat loss results from:results from: ConductionConduction ConvectionConvection RadiationRadiation EvaporationEvaporation RespirationRespiration


Heat = Molecular MotionHeat = Molecular Motion


Conduction:Conduction: Heat loss occurs Heat loss occurs

due to direct due to direct contact of the body contact of the body with a cooler object.with a cooler object.

Heat flows from Heat flows from higher temperature higher temperature matter to lower matter to lower temperature matter.temperature matter.


Convection:Convection: Heat loss occurs Heat loss occurs

due to air currents due to air currents passing over the passing over the body.body.

Heat must first be Heat must first be conducted to the conducted to the air before air before convection can convection can occur.occur.


Radiation:Radiation: Heat loss Heat loss

results from results from infrared rays.infrared rays.

All objects not All objects not at absolute zero at absolute zero will radiate heat will radiate heat to the to the atmosphere.atmosphere.

RadiationRadiation


Evaporation:Evaporation: Heat loss occurs Heat loss occurs

as water as water evaporates from evaporates from the skin.the skin.

Heat loss occurs Heat loss occurs as water as water evaporates from evaporates from the lungs during the lungs during respirationrespiration..


Respiration:Respiration: Respiration combines the heat Respiration combines the heat

loss mechanisms of convection, loss mechanisms of convection, radiation, and evaporation.radiation, and evaporation.

Expired air is normally 98.6 Expired air is normally 98.6 degrees F. and 100% humidified.degrees F. and 100% humidified.

Heat-conserving Heat-conserving MechanismsMechanisms

Vasoconstriction Vasoconstriction of blood vessels in of blood vessels in the skin.the skin.

Stimulated Stimulated through activation through activation of the sympathetic of the sympathetic nervous system.nervous system.

Causes pale, cool Causes pale, cool skin.skin.


Piloerection is more Piloerection is more commonly called commonly called “goose bumps” or “goose bumps” or “goose flesh.”“goose flesh.”

Evolutionary Evolutionary remnant.remnant.

Caused by Caused by sympathetic sympathetic stimulation of stimulation of arrector piliarrector pili muscles. muscles.


Increased heat Increased heat production:production: ShiveringShivering Activation of Activation of

futile cycles futile cycles (chemical (chemical thermogenesis)thermogenesis)

Increased Increased thyroxine releasethyroxine release


When the core When the core temperature of temperature of the body drops the body drops below below

9595º º F, an F, an individual is individual is considered to considered to be be hypothermichypothermic..


Clinically, hypothermia results Clinically, hypothermia results from:from: Inadequate heat generation by Inadequate heat generation by

the body (thermogenesis).the body (thermogenesis). Excessive cold stress.Excessive cold stress. A combination of both.A combination of both.


Normal Range:Normal Range: 96-10096-100º º FF

Mild Mild Hypothermia:Hypothermia: 90-9590-95º º FF

Severe Severe HypothermiaHypothermia < 90< 90º º FF


Predisposing Factors to Predisposing Factors to Hypothermia:Hypothermia: Patient AgePatient Age Patient HealthPatient Health MedicationsMedications Prolonged or Intense ExposureProlonged or Intense Exposure Co-existing Weather ConditionsCo-existing Weather Conditions


Patient Age:Patient Age: Pediatric and geriatric patients Pediatric and geriatric patients

cannot tolerate cold environments cannot tolerate cold environments and have less capacity for heat and have less capacity for heat generation.generation.

Older patients often become Older patients often become hypothermic in environments that hypothermic in environments that seem only mildly cool to others.seem only mildly cool to others.


Patient Health:Patient Health: Hypothyroidism (suppresses Hypothyroidism (suppresses

metabolic rate)metabolic rate) Malnutrition, hypoglycemia, Malnutrition, hypoglycemia,

Parkinson’s disease, fatigue, and Parkinson’s disease, fatigue, and other medical conditions can other medical conditions can interfere with the body’s ability interfere with the body’s ability to combat cold exposure.to combat cold exposure.


Medications:Medications: Some drugs interfere with the Some drugs interfere with the

body’s heat-generating body’s heat-generating mechanisms.mechanisms.

These include: narcotics, alcohol, These include: narcotics, alcohol, antihistamines, antipsychotics, antihistamines, antipsychotics, antidepressants, and many antidepressants, and many others.others.


Prolonged or Intense Prolonged or Intense Exposure:Exposure: The length and severity of cold The length and severity of cold

exposure have a direct effect on exposure have a direct effect on morbidity and mortality.morbidity and mortality.

The Wind Chill Index (WCI) must The Wind Chill Index (WCI) must be taken into consideration.be taken into consideration.


Coexisting Coexisting Weather Weather Conditions:Conditions: High humidity, High humidity, brisk winds, brisk winds, accompanying rain accompanying rain

can all magnify the can all magnify the effect of cold effect of cold exposure on the body exposure on the body by accelerating heat by accelerating heat loss from the skin.loss from the skin.


Degrees of Hypothermia:Degrees of Hypothermia: MildMild– Core temperature > 90 – Core temperature > 90

degrees F (32 degrees C)degrees F (32 degrees C) SevereSevere– Core temperature < 90 – Core temperature < 90

degrees F (32 degrees C)degrees F (32 degrees C)

Signs and SymptomsSigns and Symptoms

MILD Hypothermia:MILD Hypothermia: LethargyLethargy ShiveringShivering Lack of CoordinationLack of Coordination Pale, cold, dry skinPale, cold, dry skin Early rise in blood pressure, Early rise in blood pressure,

heart, and respiratory rates.heart, and respiratory rates.

Signs and SymptomsSigns and Symptoms

SEVERE Hypothermia:SEVERE Hypothermia: No shiveringNo shivering Heart rhythm problemsHeart rhythm problems Cardiac arrestCardiac arrest Loss of voluntary muscle controlLoss of voluntary muscle control Low blood pressureLow blood pressure Undetectable pulse and respirationsUndetectable pulse and respirations

PreventionPrevention

Preventive Measures:Preventive Measures: Warm dressWarm dress Plenty of restPlenty of rest Adequate dietAdequate diet Limit ExposureLimit Exposure

TreatmentTreatment

Treatment for Treatment for Hypothermia:Hypothermia:

1. Remove wet garments1. Remove wet garments

2. Protect against further heat 2. Protect against further heat loss and wind chill.loss and wind chill.

3. Maintain patient in 3. Maintain patient in horizontal position.horizontal position.

TreatmentTreatment

Treatment for Treatment for Hypothermia:Hypothermia:

4. Avoid rough handling.4. Avoid rough handling.

5. Monitor the core 5. Monitor the core temperature.temperature.

6. Monitor the cardiac rhythm.6. Monitor the cardiac rhythm.

TreatmentTreatment

ECG changes seen in hypothermia:ECG changes seen in hypothermia: Prolongation of first the PR interval, then the Prolongation of first the PR interval, then the

QRS, then the QTc interval.QRS, then the QTc interval. J waves (also called Osborne waves) can J waves (also called Osborne waves) can

occur at any temperature < 32.3occur at any temperature < 32.3º C (90º F).º C (90º F). Most frequently seen in Leads II and VMost frequently seen in Leads II and V66.. The size of the J waves increase with The size of the J waves increase with

temperature depressiontemperature depression..

““J” or Osborne WavesJ” or Osborne Waves

RewarmingRewarming

Methods of Rewarming:Methods of Rewarming: Active External RewarmingActive External Rewarming Active Internal RewarmingActive Internal Rewarming

RewarmingRewarming

Active Rewarming of MILD Active Rewarming of MILD Hypothermia:Hypothermia: Active external methods:Active external methods:

Warm blanketsWarm blankets Heat packsHeat packs Warm water immersion (with caution)Warm water immersion (with caution)

Active internal methods:Active internal methods: Warmed IV fluidsWarmed IV fluids

RewarmingRewarming

Active Rewarming of SEVERE Active Rewarming of SEVERE Hypothermia:Hypothermia: Active external methods:Active external methods:

Warm blanketsWarm blankets Heat packsHeat packs Warm water immersion (with Warm water immersion (with

caution)caution) Active internal methods:Active internal methods:

Warmed IV fluidsWarmed IV fluids Warmed, humidified oxygenWarmed, humidified oxygen

RewarmingRewarming

Rewarming of the SEVERE Rewarming of the SEVERE hypothermia patient is best carried hypothermia patient is best carried out in the Emergency Department out in the Emergency Department using a pre-defined protocol, unless using a pre-defined protocol, unless travel time exceeds 15 minutes.travel time exceeds 15 minutes.

Most patients who die during active Most patients who die during active rewarming die from ventricular rewarming die from ventricular fibrillation.fibrillation.

RewarmingRewarming

Application of external heat in the Application of external heat in the prehospital setting is usually not prehospital setting is usually not effective and not recommended effective and not recommended because:because: More heat transferrence is required More heat transferrence is required

than generally possible in the than generally possible in the prehospital setting.prehospital setting.

Application of external heat may cause Application of external heat may cause “rewarming shock.”“rewarming shock.”

RewarmingRewarming

Rewarming Shock:Rewarming Shock: Occurs due to peripheral reflex Occurs due to peripheral reflex

vasodilation.vasodilation. Causes the return of cooled blood and Causes the return of cooled blood and

metabolic acids from the extremities.metabolic acids from the extremities. May cause a paradoxical afterdrop in May cause a paradoxical afterdrop in

the core temperature further the core temperature further worsening hypothermia.worsening hypothermia.

RewarmingRewarming

Rewarming Shock:Rewarming Shock: Can be prevented in the Can be prevented in the

prehospital setting by using prehospital setting by using warmed IV fluids during active warmed IV fluids during active rewarming.rewarming.

RewarmingRewarming

Portable IV fluid Portable IV fluid heaters are available heaters are available in the United States in the United States and Canada.and Canada.

Devices fit in-line Devices fit in-line and are powered by and are powered by DC power sources.DC power sources.

RewarmingRewarming

The device is The device is single-use and single-use and remains with remains with the patient in the patient in the hospital the hospital (both the ED (both the ED and on the and on the floor).floor).

RewarmingRewarming

The HOT IV is The HOT IV is powered from a powered from a Physio-Control Physio-Control battery or from battery or from a DC converter a DC converter plugged in to plugged in to an AC outlet.an AC outlet.

Issues in HypothermiaIssues in Hypothermia

Benefits of IV Fluid Benefits of IV Fluid Warming:Warming: Maintains euthermiaMaintains euthermia Increases patient comfortIncreases patient comfort Prevents shiveringPrevents shivering


Benefits of IV Fluid WarmingBenefits of IV Fluid Warming:: Prevents cold-induced dysrhythmiasPrevents cold-induced dysrhythmias Decreases hemorrhage in abdominal Decreases hemorrhage in abdominal

trauma patientstrauma patients Decreases the incidence of Decreases the incidence of

infectious complications in infectious complications in abdominal trauma patientsabdominal trauma patients


Benefits of IV Fluid Benefits of IV Fluid WarmingWarming:: Allows active internal rewarming Allows active internal rewarming

to begin in the prehospital to begin in the prehospital setting.setting.

Less labor-intensive, freeing Less labor-intensive, freeing emergency personnel to manage emergency personnel to manage other, more pressing care needs.other, more pressing care needs.

Cardiac ArrestCardiac Arrest

Other Clinical Concerns:Other Clinical Concerns: Resuscitation of cardiac arrest Resuscitation of cardiac arrest

due to hypothermia is only due to hypothermia is only successful when the patient is successful when the patient is being re-warmed.being re-warmed.

The hypothermic cardiac arrest The hypothermic cardiac arrest patient is not DEAD until he is patient is not DEAD until he is WARM and DEAD!WARM and DEAD!

Survival from Survival from HypothermiaHypothermia

48.248.2º F (9º C)º F (9º C) - Lowest reported - Lowest reported survivor from therapeutic exposure.survivor from therapeutic exposure.

59.259.2º F (15.2º C) – Lowest reported º F (15.2º C) – Lowest reported infant survival from accidental infant survival from accidental exposure.exposure.

60.860.8º F (16º C) – Lowest reported º F (16º C) – Lowest reported adult survival from accidental adult survival from accidental exposure.exposure.

Survival from Survival from HypothermiaHypothermia

64.464.4º F (18º C) – Asystole.º F (18º C) – Asystole. 66.266.2º F (19º C) – Flat EEG.º F (19º C) – Flat EEG. 71.671.6º F (22º C) – Maximum risk for º F (22º C) – Maximum risk for

ventricular fibrillation. ventricular fibrillation. 7777º F (25º C) – Cerebral blood flow º F (25º C) – Cerebral blood flow

decreased by 66%.decreased by 66%. 78.878.8º F (26º C) – No reflexes or º F (26º C) – No reflexes or

response to painful stimuli.response to painful stimuli.


Other Clinical Concerns:Other Clinical Concerns: Hypothermia is common, even in Hypothermia is common, even in

persons with minor trauma.persons with minor trauma. Hypothermia can worsen infectious Hypothermia can worsen infectious

complications of abdominal trauma.complications of abdominal trauma. Hypothermic trauma patients suffer Hypothermic trauma patients suffer

increased blood loss compared to increased blood loss compared to their normothermic cohorts.their normothermic cohorts.


Considerations in Emergency Considerations in Emergency Care:Care:““Most traditional methods of Most traditional methods of maintaining trauma patient maintaining trauma patient temperature during temperature during prehospital transport appear prehospital transport appear to be inadequate.”to be inadequate.”From: Watts DD, Roche M, et al. The utility of From: Watts DD, Roche M, et al. The utility of traditional prehospital interventions in maintaining traditional prehospital interventions in maintaining thermostasis. thermostasis. Prehosp Emerg CarePrehosp Emerg Care 1999;3(2)115- 1999;3(2)115-122122


Considerations in Emergency Considerations in Emergency Care:Care:

““Based upon our findings, accidental Based upon our findings, accidental hypothermia poses a relevant problem hypothermia poses a relevant problem in the prehospital treatment of trauma in the prehospital treatment of trauma patients. It is not limited to a special patients. It is not limited to a special season of the year.”season of the year.”From: Helm M, Lampl L, Hauke J, Bock KH. Accidental From: Helm M, Lampl L, Hauke J, Bock KH. Accidental hypothermia in trauma patients. Is it relevant to hypothermia in trauma patients. Is it relevant to preclinical emergency treatment? preclinical emergency treatment? Anaesthesist Anaesthesist 1995;44(2):101-1071995;44(2):101-107


Considerations in Emergency Considerations in Emergency Care:Care:““Thus, hypothermia is common in Thus, hypothermia is common in

patients undergoing a laparotomy patients undergoing a laparotomy for trauma. Hypothermic patients for trauma. Hypothermic patients with similar injury severity have with similar injury severity have greater blood loss.”greater blood loss.”From: Bernabei AF, Levision MA, Bender JS. The effects From: Bernabei AF, Levision MA, Bender JS. The effects of hypothermia and injury severity on blood loss during of hypothermia and injury severity on blood loss during trauma laparotomy. trauma laparotomy. J TraumaJ Trauma 1992;33(6):835-839 1992;33(6):835-839

HyperthermiaHyperthermia

Heat crampsHeat cramps Heat tetanyHeat tetany Heat exhaustionHeat exhaustion Heat syncopeHeat syncope Heat strokeHeat stroke


Abnormal Abnormal elevation in elevation in body body temperature.temperature.

Not a normal Not a normal physiological physiological response (such response (such as fever).as fever).


Caused by Caused by environmental environmental temperature temperature increase.increase.

Increased Increased humidity.humidity.

Still air.Still air.


Heat waves not Heat waves not uncommon.uncommon.

More devastating More devastating where heat waves where heat waves are uncommon.are uncommon.

600 heat-related 600 heat-related deaths in 1995 deaths in 1995 Chicago heat Chicago heat wave. wave.

Heat CrampsHeat Cramps

Brief, painful muscle Brief, painful muscle contractions.contractions.

Frequent Frequent complication of heat complication of heat exhaustion.exhaustion.

Salt depletion and Salt depletion and other electrolyte other electrolyte problems commonly problems commonly associated.associated.

Self-limited.Self-limited. Symptomatic Symptomatic

treatment.treatment.

Heat TetanyHeat Tetany

Carpopedal spasms Carpopedal spasms that occur in hot that occur in hot environments.environments.

Secondary to Secondary to hyperventilation hyperventilation from body’s from body’s attempt to cool.attempt to cool.

Resolves when Resolves when hyperventilation hyperventilation slows. slows.

Heat ExhaustionHeat Exhaustion

Results from Results from cardiovascular cardiovascular strain as body strain as body attempts to attempts to maintain normal maintain normal temperature.temperature.

Usually develops Usually develops and continues and continues over several days.over several days.


Most common Most common between body between body temperature of temperature of 102.9° (39.4° C) 102.9° (39.4° C) and 104° (40° C).and 104° (40° C).

Finding is Finding is unreliable.unreliable.

Diagnosis should be Diagnosis should be made on physical made on physical assessment.assessment.


Firefighters at Firefighters at increased risk of increased risk of developing heat developing heat exhaustion.exhaustion.

Rehab sector Rehab sector essential for essential for major fires in major fires in warm weather.warm weather.


Symptoms:Symptoms: DizzinessDizziness HeadacheHeadache FatigueFatigue IrritabilityIrritability AnxietyAnxiety ChillsChills Nausea/vomitingNausea/vomiting Heat crampsHeat cramps


Signs:Signs: TachycardiaTachycardia HyperventilatioHyperventilatio

nn HypotensionHypotension SyncopeSyncope


Treatment:Treatment: Remove patient from warm Remove patient from warm

environment.environment. Remove bulky clothing.Remove bulky clothing. Fluids (IV or PO).Fluids (IV or PO). AntiemeticsAntiemetics Removal from duty.Removal from duty.

Heat SyncopeHeat Syncope

Form of postural hypotension.Form of postural hypotension. Results from massive vasodilation.Results from massive vasodilation. Dehydration usually a contributing Dehydration usually a contributing

factor.factor. Most common in persons not Most common in persons not

acclimatized to the heat.acclimatized to the heat. Usually occurs during the early Usually occurs during the early

stages of heat exposure.stages of heat exposure.

Heat SyncopeHeat Syncope

Treatment:Treatment: SymptomaticSymptomatic CoolCool FluidsFluids Rule out other Rule out other

causes of causes of syncope.syncope.

Heat StrokeHeat Stroke

Heat stroke is a Heat stroke is a life-threatening life-threatening emergency!emergency!

Heat stroke is a Heat stroke is a total failure of total failure of temperature temperature regulation.regulation.


Core Core temperature temperature >104.9° (40.5° >104.9° (40.5° C).C).

Loss of sweating Loss of sweating (anhidrosis).(anhidrosis).

Altered mental Altered mental status.status.


Anhidrosis may or Anhidrosis may or may not be may not be present.present.

Just because a Just because a patient is patient is sweating does not sweating does not mean they are mean they are not suffering heat not suffering heat stroke.stroke.


Treatment Treatment must include:must include: CPR if required.CPR if required. Fluid and Fluid and

electrolyte electrolyte replacement.replacement.

Immediate Immediate cooling.cooling.


Goal of cooling is to get body Goal of cooling is to get body temperature down to 104° (40° C).temperature down to 104° (40° C).

Preferred method is immersion in cold Preferred method is immersion in cold water or ice-water bath.water or ice-water bath.

Evaporative cooling (moistened sheets) Evaporative cooling (moistened sheets) and ice packs) can be used but less and ice packs) can be used but less effective.effective.

Essential to remove from bath as soon Essential to remove from bath as soon as target temperature reached to avoid as target temperature reached to avoid overcooling and activation of reflex overcooling and activation of reflex mechanisms.mechanisms.

FeverFever

FeverFever

Fever is Fever is notnot an abnormal increase in an abnormal increase in body temperature.body temperature.

It is a resetting of the body’s set-point It is a resetting of the body’s set-point above normal.above normal.

Causes:Causes: Abnormalities within the brain (tumors, Abnormalities within the brain (tumors,

hemorrhage compress hypothalamus)hemorrhage compress hypothalamus) DehydrationDehydration Toxic substances within the body Toxic substances within the body

(pyrogens). (pyrogens).

FeverFever

Definitions:Definitions: Any oral temp ≥ 98.9° (37.2° Any oral temp ≥ 98.9° (37.2°

C) in the early morning.C) in the early morning. Any oral temp ≥ 100° (37.8° Any oral temp ≥ 100° (37.8°

C) at any time.C) at any time.

FeverFever

How hot is high?How hot is high? Human upper limit of fever is Human upper limit of fever is

105.8-107.6°F (41–42°C).105.8-107.6°F (41–42°C). Almost never exceeds 42° C Almost never exceeds 42° C

unless there’s a failure in unless there’s a failure in thermoregulation.thermoregulation.

FeverFever

How hot is high?How hot is high? 104° (40° C) may be the upper 104° (40° C) may be the upper

limit of fever in infants <12 limit of fever in infants <12 weeks old.weeks old.

Remember that young infants Remember that young infants can have infections with normal can have infections with normal or lowered body temps.or lowered body temps.

FeverFever

Can high fever can Can high fever can cause damage in cause damage in and of itself?and of itself? Seizures and Seizures and

complications.complications. Brain damage Brain damage

because of the because of the infection causing infection causing the fever the fever (meningitis or (meningitis or encephalitis).encephalitis).

FeverFever

No human studies No human studies published.published.

Animal studies Animal studies suggest that a suggest that a body temp of ≥ body temp of ≥ 107.5° (42° C) in 107.5° (42° C) in humans may humans may trigger enough trigger enough adverse effects on adverse effects on a cellular level to a cellular level to cause death.cause death.

FeverFever

Animal studies:Animal studies: Temperature >105° Temperature >105°

may cause may cause respiratory alkalosis respiratory alkalosis and occasional and occasional electrolyte electrolyte imbalancesimbalances

Temperature Temperature >105.8° >105.8° maymay cause cause cellular swelling and cellular swelling and damage in the damage in the brain, kidneys and brain, kidneys and liverliver

FeverFever

When set-point in hypothalamus When set-point in hypothalamus changes, it usually takes several changes, it usually takes several hours to reach new set-point.hours to reach new set-point.

Signs and symptoms common Signs and symptoms common during this phase (blood during this phase (blood temperature lower than temperature lower than hypothalamic set-point). hypothalamic set-point).

FeverFever

Fever is generally uncomfortable.Fever is generally uncomfortable. Signs and Symptoms:Signs and Symptoms:

ChillsChills Flushing of the skinFlushing of the skin Teeth chatteringTeeth chattering Feels coldFeels cold ShiveringShivering Skin cold to touch (phase-dependent)Skin cold to touch (phase-dependent)

FeverFever

It is important to remember It is important to remember that fever is a that fever is a normalnormal response response to many diseases.to many diseases.

Although uncomfortable, it is Although uncomfortable, it is rarely harmful.rarely harmful.

Febrile SeizuresFebrile Seizures

Incidence of 2-5% in US.Incidence of 2-5% in US. 6 months – 3 years (median 6 months – 3 years (median

18-22 months).18-22 months). Boys more often than girls.Boys more often than girls. Often occurs with the first Often occurs with the first

fever of an illness.fever of an illness.


Characteristics:Characteristics: 85% of all febrile seizures last for 85% of all febrile seizures last for

<15 minutes and don’t recur <15 minutes and don’t recur within 24 hours.within 24 hours.

50% have temp between 39°-50% have temp between 39°-40°C.40°C.

25% have temp 25% have temp >> 40°C. 40°C.

Febrile Seizures:Febrile Seizures:

Characteristics:Characteristics: 1/3 will have recurrence of febrile 1/3 will have recurrence of febrile

seizures.seizures. The younger the age at 1The younger the age at 1stst febrile seizure, febrile seizure,

the higher the incidence of recurrence.the higher the incidence of recurrence. El-Radhi, 1998El-Radhi, 1998

Presenting temp <39° for 1Presenting temp <39° for 1stst febrile seizure febrile seizure have 2.5x risk for recurrence within the same have 2.5x risk for recurrence within the same illness and 3x risk for recurrence with other illness and 3x risk for recurrence with other illnessesillnesses


Simple febrile Simple febrile seizures are seizures are generalized tonic-generalized tonic-clonic with brief clonic with brief post-ictal period.post-ictal period.

Complex or Complex or atypical febrile atypical febrile seizures can be seizures can be focal, atonic, or focal, atonic, or prolongedprolonged


Multiple studies Multiple studies have revealed have revealed several genetic several genetic loci that code loci that code for for susceptibility to susceptibility to febrile seizures.febrile seizures.


Fever + Seizure ≠ “Febrile Fever + Seizure ≠ “Febrile Seizure”Seizure” Meningitis/SepsisMeningitis/Sepsis Seizure disorderSeizure disorder Medication/Poison-inducedMedication/Poison-induced

Febrile Seizure is NOT an EMS Febrile Seizure is NOT an EMS diagnosis!diagnosis!

Febrile SeizureFebrile Seizure

Myths:Myths: Rate of temperature rise does Rate of temperature rise does

notnot appear to be a cause of appear to be a cause of febrile seizures.febrile seizures.

No studies have demonstrated No studies have demonstrated that febrile seizures without that febrile seizures without complicating hypoxia cause brain complicating hypoxia cause brain damage.damage.


Myths:Myths: Febrile seizures cause epilepsy.Febrile seizures cause epilepsy.

Risk factors for afebrile seizure:Risk factors for afebrile seizure: Complex 1Complex 1stst Febrile Seizure. Febrile Seizure. Abnormal neuro state before 1Abnormal neuro state before 1stst Febrile Febrile

Seizure.Seizure. Afebrile seizure history in parents or Afebrile seizure history in parents or

siblingssiblings If If >>2 risk factors, 10% chance of 2 risk factors, 10% chance of

developing “epilepsy”developing “epilepsy”


Myths:Myths: Treating the fever will prevent the Treating the fever will prevent the

seizure.seizure. Antipyretics are Antipyretics are notnot protective. protective. Rectal/oral diazepam at time of fever Rectal/oral diazepam at time of fever

isis protective. protective. Daily oral phenobarbital is protective Daily oral phenobarbital is protective

but has undesirable side effects.but has undesirable side effects.


There is There is nono evidence that evidence that bringing the bringing the fever down by fever down by anyany means will means will stop or prevent stop or prevent a febrile a febrile seizure.seizure.


Bottom line:Bottom line: They’re more scary than They’re more scary than

dangerous.dangerous. Most resolve without Most resolve without

anticonvulsant treatment.anticonvulsant treatment. Antipyretic treatment does not Antipyretic treatment does not

prevent or treat febrile seizures.prevent or treat febrile seizures. Not all seizures with fever are Not all seizures with fever are

febrile seizures.febrile seizures.

FeverFever

Fever Fever treatment:treatment: Treatment of Treatment of

choice is choice is antipyretics antipyretics (acetaminophe(acetaminophen, n, ibuproprofen).ibuproprofen).

FeverFever

There is no evidence to support one There is no evidence to support one antipyretic over another when antipyretic over another when considering effectivenessconsidering effectiveness

No delivery route (po/pr) has been No delivery route (po/pr) has been proven more effective than another, proven more effective than another, but there has been recent evidence but there has been recent evidence to suggest that higher doses may to suggest that higher doses may be needed when given rectally.be needed when given rectally.

FeverFever

Acetaminophen 10-15 mg/kg Acetaminophen 10-15 mg/kg po/pr q4h.po/pr q4h.

Ibuprofen 10mg/kg po q6-8h.Ibuprofen 10mg/kg po q6-8h. No demonstrated benefit to No demonstrated benefit to

alternating the two meds but alternating the two meds but there is a significant chance of there is a significant chance of dosing error and possible dosing error and possible overdose.overdose.

FeverFever

Other cooling methods:Other cooling methods: Never use ice, cold water or Never use ice, cold water or

alcohol.alcohol. Use tepid water or cool Use tepid water or cool

compresses over head and pulse compresses over head and pulse points.points.

Avoid inducing chills.Avoid inducing chills.

FeverFever

Should we treat fever?Should we treat fever? AnimalAnimal studies suggest that the studies suggest that the

fever mechanism is a positive fever mechanism is a positive adaptive responseadaptive response Triggers host immune responsesTriggers host immune responses May stabilize cell membranesMay stabilize cell membranes

FeverFever

Should we treat fever?Should we treat fever? Increased metabolic stress and Increased metabolic stress and

oxygen demand:oxygen demand: Patients with poor cardiac reservePatients with poor cardiac reserve Patients with poor pulmonary Patients with poor pulmonary

reservereserve Lowers the “seizure threshold”Lowers the “seizure threshold”

FeverFever

Reasons to treat fever:Reasons to treat fever: Patient comfortPatient comfort Parent comfortParent comfort

FeverFever

Should EMS Should EMS providers treat providers treat fever?fever?

FeverFever

Should EMS providers treat fever?Should EMS providers treat fever? Pros:Pros:

Providing an additional service to our Providing an additional service to our customers.customers.

Comfort measure.Comfort measure. Cons:Cons:

Treat and release?Treat and release? Documentation of fever.Documentation of fever. Dosing of meds.Dosing of meds. Reinforcement of fears.Reinforcement of fears.

FeverFever

Cultural Cultural considerations.considerations.

Relates to Relates to ancient beliefs ancient beliefs of “hot” and of “hot” and “cold” illnesses.“cold” illnesses.

FeverFever

Summary:Summary: Fever is not the clearly defined Fever is not the clearly defined

concept many believe it to be.concept many believe it to be. Both the lay public and the medical Both the lay public and the medical

community need more education community need more education about fever.about fever.

““Fever Phobia” is unfounded.Fever Phobia” is unfounded. Fever treatment by EMS personnel is Fever treatment by EMS personnel is

controversial.controversial.


For more For more detailed detailed information on information on temperature temperature regulation and regulation and hypothermia, hypothermia, see the March see the March 2003 issue of 2003 issue of JEMSJEMS magazine. magazine.

disorders of temperature regulation bryan e. bledsoe, facep midlothian, tx

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