Cold Injuries Flashcards
Two common cold injuries & susceptible populations
- Hypothermia & Frostbite
- Populations - winter athletes, moutaineers, elderly, homeless, & employed in cold
Causes of frostbite
- Environmental exposure to cold
- Direct exposure to freezing materials…ice packs
- Inhalation of hydrocarbons (upper airway)
Frostnip definition
Immersion Foot (“Trench Foot) definition
- Frost = cold induced, local paresthesia that burns/tingles, resolve w/ rewarming
- Immersion = injury to symp. nerves & vasculature, feet erythmatous, numb/pain, covered w/ hemorrhagic bullae
What disease progression is this?
Immersion foot/Trench foot
Perio definition and lesion descriptions
- Def = acute or repetitive exposure to damp cold above freezing point
- Edematous, red/purple, & may be pruritic and/or painful
Frostbite def & what occurs when ice crystals form in tissues?
- Def = tissue cooling w/ vasoconstriction & ischemia
- Abnormal electrolytes; cell dehyd, lysis, & death
What can thawing do to frostbite?
- Initiate inflamm pathway = further tissue ischemia, emboli w/in vessels, & thrombi in larger vessel
- Made worse if the injury re-freezes after initial thaw
Common symptoms of frostbite
- Cold, numbness, & clumsiness of area
- skin insensate, white/grayish color, & hard or waxy to touch
- Upon rewarming, bullae usually develop
1st degree frostbite features
- superficial
- pallor and anesthesia surrounded by erythema
- no tissue infarction
2nd degree frosbite features
- Large blisters w/ clear fluid, surrounded erythema & edema
- Seen 24 hrs after rewarming
- No tissue loss
3rd degree frostbite features
- Blisters hemorrhagic & more proximal
- Black eschar 1+ week
4th degree frostbit depth & extent damage to tissue
- Extend to muscle & bone
- Complete necrosis
Should you rub a frostbit area to warm it?
- No, may cause more tissue damage
What is the preferred way to rewarm frostbit tissue?
When can you tell if frostbit tissue is thawed?
- Rewarm by placing feet in water heated 37-39° C
- Airdry tissues
- Complete when tissue is red/purple & soft to touch
How to care for frostbite wound?
- Non-stick gauze & use pledgets between digits
- elevate=reduce edema
- Blisters
- non hemorr may be debrided
- hemmorr may be drained, not debrided
- Give tetanus if due
- Surgery if severe
- Avoid Ab = may cause maceration (use if suspected infection however)
Thrombolytic therapy to txt frosbite goal?
- Save tissue from microvascular thrombus
- Use tissue plasminogen activator (tPA), can add heparin joint (not by itself)
Do you amputate frostbit tissue right away?
No, complete demarcation of necrosis may take 1-3 months
Only amputate right away if signs of sepsis/gangrene
5 Ways body loses heat
- Radiation
- Conduction (body to object)
- Convection
- Evaporation
- Respiration
Normal core body temp & bodies natural reaction to hypothermia
- 37 C
- Shivering & catecholamine production
- Vasoconstriction vessels in periphery to shunt blood to organs & prevent heat loss
Common causes of hypothermia
- Metabolism (hypothyroid/-adrenalism)
- Extreme age
- Drug induced (ethanol/sedatives)
- Environment
- Aggressive fluid resuscitation or heat stroke txt
Mild hypothermia: body reaction & signs
- Rxn = HTN, shiver, tachycardia/pnea, vasoconstriction
- Signs = apathy, ataxia, cold diuresis, & impaired judge.
Temp ranges for normal, mild, moderate, and severe hypo
- normal = 37° C
- mild = 32.2-35° C
- mod = 28-32.2° C
- severe = <28° C
Moderate hypothermia signs
- Decreased HR/RR/BP
- Dilated pupils
- No shivering
- J wave
- Paradoxal undressing
What is a J Wave?
- Sign of moderate hypothermia
- positive deflection
- Height of deflection is proportionate to degree of hypothermia
Severe hypo symptoms/signs
- Apnea
- Coma
- Nonreactive pupils
- Oliguria (no urine)
- Pulm. edema
- Little/no EEG
- Ventricular dysrythmia
Preferred thermometer when measuring hypothermia?
Rectal probe thermometer
Definitions of methods of rewarming:
- Passive external
- Active external
- Active Internal (Core) Rewarming
- mild hypo, remove clothing & cover w/ blankets, patient must have intact thermoreg mech, endocrine f(x), & energy stores
- mod-sev, heat directly to skin, need intact circ, warm trunk before extremities
- severe
- Warm IV-saline w/ dextrose heat to 40-45° C
- Extracorporeal blood warming - take out blood, heat, then reintroduce, most effective method
Most effective temperature reading in rewarming
Esophageal
Risks in active external rewarming
- Afterdrop - cold peripheral blood rapidly returns to heart
- Rewarming acidosis - cold, acidemic blood returns to trunk = drops core temp & pH
Lab values to check with hypothermia (2 main)
- Glucose
- EKG
