Heat Related Injury and Illness Flashcards
The 4 ways the body dissipates heat
- Radiation (infared rays)
- Convection (air/water across skin)
- Conduction (physical Contact)
- Evaporation (Sweat)
Pathophysiology of a Fever
Temperature elevation due to activity of the hypothalamus, in response to cytokines triggered by infection or sterile inflammation
Pathophysiology of Hyperthermia
Temperature elevation due to uncontrolled heat generation (i.e. muscular hyperactivity), which can generate temperatures higher than a fever, with greater risk of thermal injury to tissues.
Unlike fever, hyperthermia involves complete loss of thermal control
Does Fever or Hyperthermia involve complete loss of thermal control?
Hyperthermia
As body temp incr, skin sensors and warm blood stimulates the anterior hypothalamus, which stimulates ….
- Vasodilatation
- Increased Cardiac Output
- Increased Respiratory Rate
- Increased Sweat Production
as temp incr above ____, most heat loss occurs thru sweating.
95F
As relative humidity incr above ____%, sweating becomes ineffective
75%
bc moisture on skin cannt transfer into air bc theres not enough of a humidity difference b/w skin and air
Factors contributing to incr heat illness danger
- High heat
- high humidity
- lack of wind
Types of heat illness
- Heat cramps
- Heat exhaustion
- Heat stroke
Heat cramps
- painful, involuntary spasmodic muscle cramps that occur in heavily exercised muscles in hot and humid environments
- mildest form of heat injury
- ET: e- imbalance
Do heat cramps results in hyper or hyponatremia?
hyponatremia bc you sweat and replace water but not salt
Typical body temp during muscle cramps?
norm, body is still thermoregulating
Heat cramps trmnt
- firm passive muscle stretching (ankel dorsiflexion for calf cramp)
- rest in cool space
- Oral fluids (1-2L water with 2 tsp salt)
When to seek immediate attention for heat cramps?
- Cramps cannot be controlled
- Insufficient fluid intake due to nausea/vomiting
- Significant weakness
- Profuse sweating not controlled in air-conditioned environment
- May have in addition to heat exhaustion or heat stroke
Heat exhaustion can very quickly lead to ______ if not treated ASAP
heat stroke
Heat exhaustion is determined by a core temp >______
An illness resulting from prolonged, heavy activity in a hot environment with subsequent dehydration, electrolyte depletion, and rectal temperature 37.8 °C - 40 °C (100 °F - 104 °F)
Heat stroke is determined by a core temp >_____
A life-threatening heat illness characterized by extreme hyperthermia (core temperature >40 °C [104.0 °F]), dehydration, and neurologic manifestations
Which two types of heat illness are thermoregulation issues?
Heat exhaustion and heat stroke
Which heat illness is due to electrolyte abnorm?
Heat cramps
Heat exhaustion vs heat stroke (SS & trmnt)
Exertional vs Non-exertional heat stroke
- Exertional = Young althete on the field for too long
- Non-exertional = old women watching the game in the shade
Meds that impair heat dissipation (risks for elderly)
phenothiazines, anticholinergics, antihistamines, beta-blockers
- Anticholinergic properties (atropine)
- Antiepileptic (topiramate)
- Antihistamines
- Glutethimide (Doriden)
- Phenothiazines
- Tricyclic antidepressants
- Amphetamines, cocaine, “ecstasy”
- Ergogenic stimulants (e.g., ephedrine, ephedra)
- Lithium
- Diuretics
- β-Blockers
- Ethanol
Predisposing factors for heat illness (not due to illness)
Lack of acclimatization
Low physical fitness
Excessive body weight
Dehydration
Advanced age
Young age
Predisposing factors for heat illness (medical co-morbidities)
- Inflammation and fever
- Viral infection
- Cardiovascular disease
- Diabetes mellitus
- Gastroenteritis
- Rash, sunburn, and previous burns to large areas of skin
- Seizures
- Thyroid storm
- Neuroleptic malignant syndrome
- Malignant hyperthermia
- Sickle cell trait
- Cystic fibrosis
- Spinal cord injury
Heat exhaustion or stroke?
- Generalized malaise, weakness, headache, muscle and abdominal cramps, nausea, vomiting, hypotension, tachycardia.
- Rectal temperature is usually normal.
- Sweating is usually present.
exhaustion
Heat exhaustion or stroke?
- Neurologic manifestations (seizures, tremor, hemiplegia, coma, psychosis, other bizarre behavior)
- Evidence of dehydration (poor skin turgor, sunken eyeballs)
- Tachycardia, hyperventilation
- Skin is hot, red, and flushed
- Sweating is often (not always) absent, particularly in elderly patients
stroke
why are kids under 4 and elderly over 65yo at higher risk for heat illness?
kids CNS is not fully developed and cant thermoregulate as well
Elderly ppl have deterioating CNS
Which labs can differentiate b/w heat exhaustion and stroke?
Mild or absent increases in heat exhaustion:
creatine phosphokinase (CPK)
aspartate aminotransferase (AST)
lactate dehydrogenase (LDH)
alanine aminotransferase (ALT)
Possible lab abnormalities for heat exhaustion and stroke
- HIGH BUN, creatinine, hematocrit
- Hypo/hypernatremia, hyper/hypoK+
- HIGH LDH, AST, ALT, CPK, Bilirubin
- Lactic acidosis, resp alkalosis (hyperventilation)
- Myoglobinuria, hypofibrinogenemia, fibrinolysis, hypocalcemia
Heat exhaustion trmnt
- get out of the heat
- fluids 2L q4hr
- salt replacement (1/4 tsp salt in 1L water)
- if IV fluids if unable to drink
IV Fluids for heat exhaustion?
- young athletes -> NS IV (3-4L over 6-8hrs)
- elderly patients -> consider using D5½NS IV with the rate titrated to cardiovascular status.
Heat stroke trmnt
- rapid cooling
- rmv clothes
- if unconscious -> roll pt on their side
- protect airway and give nasal O2 at 4L/min to keep SatO2 >90%
- Monitor body temp q 5min (rectal temp goal: 38C (102.2F) within 30-60min)
- Stop active cooling when 38-39 °C to prevent overcooling
- Continue monitoring for thermal instability for up to 6 hours
The goal of active cooling is to drop the temp down to ________ within ______min
38C (102.2F) within 30-60min
Stop once this is reached to prevent overcooling
Monitor body temp q ____min
5
Ways to cool a person with heat stroke?
- spray bottle + fan
- immersion in tepid water (15C, 59F) is preferred over ice immersion to minimize risk of shivering
- ice bath (more effective than other intrusive options like ice cold stomach lavage)
Why should you NOT cool a person by puting ice packs on their bare skin (axilla, neck, groin)
they increase peripheral vasoconstriction and may induce shivering.
Why are antipyretics ineffective at cooling a person with heat stroke?
the hypothalamic set point during heat stroke is normal despite the increased body temperature.
Antipyretics are agents that try to decrease a fever by telling the hypothalamus to decrease the set body temperature.
Trying to turn the temperature down won’t do anything if the room is on fire
Why are Arctic sun (cooling pads) not preferred to cool a person with heat stroke?
not quick enough
Why should vasopressors be avoided if possible in pt with heat stroke?
may cause cutaneous vasoconstriction which impairs heat release
management of heat stroke
- Intubate a comatose patient, or one with extreme rigidity, or in status epilepticus
- Otherwise, nasal O2
- Insert Foley catheter
- Continuous ECG monitoring is recommended.
- Insert at least two large-bore IV lines and begin IV hydration with normal saline (NS) or Lactated Ringer.
- Draw initial laboratory studies: Electrolytes, complete blood count, blood urea nitrogen, creatinine, AST, ALT, CPK, LDH, glucose, PT (INR), PTT, platelet count, Ca2+, lactic acid, Coag profile, and arterial blood gases.
Hyperthermia complications
- Rhabdomyolysis
- Acute hepatic failure (rarely leading to fulminant failure requiring transplantation)
- Seizure
- Aspiration pneumonia -> ARDS
- Stress-induced cardiomyopathy
- Disseminated Intravascular Coagulation (DIC)
- Hypoglycemia
- Hyponatremia (likely hypernatremic if dehydrated)
Heat stroke complication trmnts
Hypotension
Vigorous hydration with normal saline or Ringer lactate
Heat stroke complication trmnts
Shivering
- Benzodiazepines, muscle relaxation and anti-seizure effects
- Ketamine, help control agitation
- Opioids, treat pain if source of agitation (avoid fentanyl if concerned of serotonin syndrome)
- Magnesium
- Buspirone 30mg PO
Caution, these can decr resp drive (especiially opiates). if you have to use, knock them out and intubate
Heat stroke complication trmnts
Acidosis
Use bicarbonate judiciously (only in severe acidosis)
usu you just treat the underlying ET
Heat stroke complications
Rhabdomyoloysis is a concern for ____
compartment syndrome
heat stroke prognosis
- Most patients recover completely within 48 hr.
- Central nervous system injury is permanent in 20% of cases.
- Mortality rate can exceed 30% in patients with prolonged and severe hyperthermia.
- Delayed access to cooling is the leading cause of morbidity and mortality in persons with heat stroke.
heat stroke complications trmnt
Agitation
Low-dose ketamine
