Impacts of Hypothermia

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Impacts of Hypothermia

• Cindy Fehr
• Malaspina University-College
• BSN Nursing Program
• Nursing 335 Fall 2005

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Hypothermia

• Body functions best at core temp 36.4C 37.5 C
  (97.5 F 99.5 F)
• When core temp lt 95 F, body loses heat faster
  than can produce it
• Causes every organ system to be under stress
  potential for permanent disability or death
  increases
• Hypothermia defined as temperature lt 96.8 F or
  36 C at two sites (e.g. rectum esophagus)

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Hypothermia Classification

• Primary hypothermia
• Occurring with accidental excessive or prolonged
  exposure to cold
• Secondary hypothermia
• Due to failure of thermoregulation by the body

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Hypothermia Classification cont.

• Mild Hypothermia
• 86.9 - 95 F or 35 - 32 C
• Moderate Hypothermia
• 82.4 - 89.6 F or 28 - 32 C
• Severe Hypothermia
• Less than 82 F or 28 C

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Normal Body Response

• Activation of SNS
• Norepinephrine released to ? muscle tone
  shivering ? ? thermogenesis
• Peripheral BV constrict to conserve heat shunt
  blood from skin to core
• If core temp continues to fall, adaptive
  mechanisms fail and vasodilation occurs ? heat
  loss from core to periphery

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Factors Increasing Risk

• Extremes of Age
• Very young and old have less sq for insulation,
  insufficient heat generation mechanisms
  (shivering), inadequate behavioral responses
  (less recognition of cold environment and what to
  do)
• Traumatic Injury or Pathologic Condition of CNS
• E.g. Stroke can disrupt hypothalamic response
• ? bleeding trauma arrive hypothermic to ED
• Assessment treatment procedures tend to worsen
  hypothermia ? lack of clothing, open body
  cavities, fluid replacement, meds (muscle
  relaxants, sedatives, anesthetics, opioids)

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Factors Increasing Risk cont.

• Endocrine Disorder
• E.g. hypothyroidism ? metabolic rate, heat
  production, behavioral responses
• Alcohol Consumption
• Dilates BV, ? heat loss, ? thermogenesis, impair
  behavioral responses
• Outdoor Occupations, Activities
• ? exposure

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Factors Increasing Risk cont.

• Medications
• E.g. phenothiazines, benzodiazepines ? centrally
  mediated vasoconstriction
• Anaesthetics can block shivering
• Other Disorders
• E.g. hepatic failure, sepsis, burns ? disrupt
  thermoregulation

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Effects of Hypothermia

• Depends of severity of hypothermia, underlying
  cause, other co-morbid factors (age, underlying
  disease process chronic health challenges)
• Affects every organ system
• Neurologic Effects
• Each 1C ? in temp 6-7 ? in cerebral blood
  flow
• Confusion, hallucinations, maladaptive behaviors,
  impaired judgment, ? drowsiness, ataxia,
  dysarthria, amnesia
• lt 82.4 F or 28 C induces coma

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Effects of Hypothermia cont.

• Cardiovascular Effects
• Normally SNS stimulates peripheral
  vasoconstriction, HTN, tachycardia, ?CO
• Cooling of body temperature ? ?HR, ? CO, ? risk
  arrhythmias (ventricular fibrillation or
  asystole)
• V fib and asystole can spontaneously occur temp
  lt25C
• In event of cardiac arrest ? ?response to
  defibrillation, pacemaker stimulation,
  cardioactive drugs, metabolism of drugs ? active
  core rewarming must be priority treatment
• Metabolic acidosis from impaired O2 delivery to
  tissues d/t peripheral vasoconstriction ?
  cellular metabolism from aerobic to anaerobic,
  serum lactate levels ? ? metabolic acidosis (pH
  7.30)
• DIC risk ? slows clotting (impairs platelet
  aggregation adherence), reduces production of
  clotting factors acidosis also affects normal
  platelet function

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Effects of Hypothermia cont.

• Respiratory Effects
• Mild hypothermia ? tachypnea
• Moderate to severe hypothermia ? progressive ? RR
  volume of ventilation, bronchospasm, loss of
  protective airway reflexes
• Can lead to pulmonary edema and apnea in severe
  cases
• Respiratory acidosis from marked respiratory
  depression ? LOC ? retaining CO2
• Respiratory arrest with core temp lt24 C

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Effects of Hypothermia cont.

• Renal Effects
• Peripheral vasoconstriction ? large fluid shifts
  to central circulation ? triggers cold diuresis
  in attempt to remove excess fluid and ?
  dehydration
• With progressive hypothermia ? ? renal blood
  flow, oliguria, anuria
• GI Effects
• ? liver metabolism of drugs elimination of
  toxins ? bleeding
• GI smooth muscle movement slows ? paralytic ileus

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Interventions for Hypothermia

• keep flat ? prevent worsening hypotension
• No sudden/rough movements, excessive activity ?
  prevent lethal arrhythmia
• Passive External Rewarming
• Tx for mild hypothermia
• Relies on patients metabolism to rewarm body
• Remove wet clothing, sheets
• Applying dry blankets or insulating material
  (extra layers, sleeping bag, hypothermia
  blanket) especially head cover
• Increase room temperature

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Interventions for Hypothermia cont.

• Active External Rewarming
• Tx for moderate hypothermia
• Forced warm air, fluid-circulating heat blanket,
  radiant heat source, heating pads
• Core Rewarming
• Tx for severe hypothermia
• Invasive
• Inhalation of warm, humidified O2
• warmed IV NS
• warmed gastric, colonic, mediastinal, closed
  throacic or peritoneal lavage
• Extracorporeal rewarming with hemodyalysis
• Cardiopulmonary bypass