Altitude and Dysbarism

Altitude Illness

  • Risk factors: altitude, rapidity of ascent, sleeping altitude
  • Pathophysiology
    • Hypobaric hypoxia
      • Pulmonary: vasoconstriction  pulmonary hypertension capillary leak
      • Cerebral: vasodilation edema
    • Acclimatization
      • Hyperventilation primary respiratory alkalosis compensatory metabolic acidosis
      • Acetazolamide promotes renal bicarbonate excretion and accelerates acclimatization
  • Management: oxygen and descent

Acute mountain sickness (2000m)

  • Mild cerebral edema
  • Symptoms: headache, nausea/vomiting, fatigue (hangover)
  • Management: acetazolamide 250mg PO BID, dexamethasone 4mg q6h

High-altitude pulmonary edema (HAPE, 3000m)

  • Non-cardiogenic pulmonary edema
  • Symptoms: dyspnea at rest, cough, fever
  • Signs: hypoxia, crackles
  • CXR: patchy infiltrates
  • Management: nifedipine, PDEi (sildenafil), HBO

High-altitude cerebral edema (HACE, 4500m)

  • Cerebral edema
  • Symptoms: ataxia, altered mental status
  • Management: acetazolamide 250mg PO BID, dexamethasone 10mg then 4mg q6h, HBO
  • Gamow bag: portable HBO

Dysbarism (diving pathology)

  • Principles
    • Boyle’s Law: volume = 1/pressure
      • Volume changes greatest near surface
    • Henry’s Law: increased pressure increases proportion of dissolved gas

Barotrauma

  • Localized (descent)
    • Barotitis media
      • Mechanism: unequal pressure between external and middle ear.
      • Symptoms: pain, vertigo if ruptured
    • Barotitis externa
      • EAC edema/hemorrhage
    • Barotitis interna
      • Bleeding/rupture of round window
      • Symptoms: vertigo, tinnitus, hearing loss
      • Management: ENT referral
    • Sinus squeeze: pain and epistaxis
    • Mask squeeze: periorbital petechiae
  • Localized (ascent)
    • Barodontalgia
      • Air trapped in filling
      • Symptoms: pain, fracture
    • Alternobaric vertigo: Unequal ear pressure causing vertigo
    • GI barotrauma: belching, flatulence
  • Pulmonary overpressurization (ascent)
    • Mechanism: rapid ascent without exhalation, focal alveolar rupture leading to pneumomediastinum, rarely pneumothorax
    • CXR: continuous diaphragm sign
    • Symptoms: dysphonia, neck fullness, chest pain
    • Management: supportive
  • Air gas embolism (ascent)
    • Mechanism: similar to POP, air enters pulmonary venous circulation
    • Symptoms: MI, arrest, stroke, seizure within 10 minutes
    • Management: IVF, oxygen, HBO

Dissolved Gas Problems

  • Nitrogen narcosis
    • At >100ft, nitrogen enters nervous system and acts similarly to general anesthetic
    • Symptoms: similar to alcohol intoxication, complications arise from poor judgement
    • Management: ascent
  • Oxygen toxicity
    • Setting: industrial dives, deep
    • Symptoms: seizure, nausea, muscle twitching
  • Decompression sickness
    • Mechanism: nitrogen gas dissolves poorly in solution, with ascent forms bubbles, occurs 1-2 hours after ascent
    • Types
      • Musculoskeletal, integumentary (“bends”)
        • Symptoms: arthralgia, cutis marmorata
      • Neurological
        • Lower spinal cord (thoracic/lumbar/sacral)
          • Symptoms: paraplegia, paresthesia, bladder dysfunction
        • Cerebellum (“staggers”)
          • Symptoms: ataxia
        • Pulmonary (“chokes”)
          • Symptoms: similar to pulmonary embolus
        • Management: IVF, oxygen, HBO

Bites

Mammalian

  • Human: Eikenella corrodens
  • Dog/Cat: Pasteurella multocida

Athropod

  • Hymenoptra (bee, wasp, hornet, ant)
    • Venom: histamine reaction, anaphylaxis
    • Symptoms
      • Local: pain, swelling, pruritus
      • Toxic (<48h): multiple bits, N/V, syncope, HA
      • Anaphylaxis: minutes
      • Delayed (10-14d): serum sickness, fever, arthralgia, malaise
    • Management
      • Remove stinger
      • Wash, ice, anti-histamine, analgesia
  • Brown recluse (violin pattern)
    • Location: Midwest, wood pile
    • Symptoms: initially painless, cytotoxic venom may cause necrosis
    • Management: supportive, Tdap, delayed debridement if necrotic
  • Black widow (red hourglass)
    • Venom: neurotoxic, ACh, NE
    • Symptoms: painful, erythema, muscle contractions (“acute abdomen”), localized diaphoresis from ACh release
    • Management: analgesia, benzodiazepines, antivenom for refractory pain (may cause anaphylaxis)

Snake

  • Crotalid (rattlesnake, copperhead, cottonmouth, collectively “pit vipers”)
    • Venom: cytotoxic, hemorrhagic
    • Symptoms: erythema/edema (ecchymoisis/bullae), nausea/vomiting, metallic taste
    • Labs: DIC
    • Management
      • Immobilization (no tourniquet)
      • Local wound care, Tdap
      • CBC, INR, fibrinogen (q2h)
      • Antivenom (Crofab 4-6 vials): given until symptoms or laboratory abnormalities arrest
      • Compartment syndrome: avoid surgery
  • Elapidae (coral snake, “red on yellow”)
    • Venom: neurotoxic, delayed 10-12h
    • Symptoms: no significant local reaction, bulbar palsies, respiratory depression
    • Management: no antivenom, supportive care, intubation

Cnidaria (jellyfish)

  • Symptoms: local pain, erythema, pruritus
  • Management: 5% acetic acid, alcohol, remove stinger
    • Antivenom for box jellyfish

Stingray

    • Symptoms: local pain, edema
    • Management: Local wound care, Tdap, hot water immersion, antibiotics for Vibrio (cephalexin with doxycycline)

Vibrio vulnificus

  • Symptoms: necrotizing fasciitis, in cirrhotic primary septicemia after ingesting shellfish

Electrical Injuries

 

Physics

  • High-voltage defined as >1,000V
  • Voltage related to injuries current via resistance (V=IR)
  • AC is 3x more lethal than DC
    • Fluctuation at 60Hz causes tetany, maintained grasp on source

Effects

  • Dysrhythmia
    • DC: asystole
    • AC: ventricular fibrillation
    • Delayed dysrhythmia uncommon
  • Burn
  • Tissue ischemia: vascular spasm or thrombosis
  • CNS: AMS, seizure, ICH, neuropathy
  • MSK: posterior shoulder dislocation

Management

  • Asymptomatic: None
  • Mild (i.e. small burn): ECG, UA (rhabdo)
  • High voltage: Labs, CT, admit for observation
  • Pediatrics: oral commissure burn, discharge with plastic surgery follow-up if no LOC, normal ECG, tolerating PO. Risk of delayed labial artery bleeding.

Complications

  • Keraunoparalysis: current travels up and down lower extremities causing transient paresthesia and paralysis.
  • Trauma: TM rupture, other mechanical injuries

 

Heat Emergencies

Overview

  •  Spectrum
    • Cramps
    • Syncope
    • Exhaustion
    • Stroke
  • Physiology of cooling
    • Radiation: body warmer than environment, heat radiates away
    • Evaporation: environment warmer than body, sweat promotes heat exchange, affected by ambient humidity

Heat cramps

  • Mechanism: fluid/electrolyte depletion resulting in muscle cramps
  • Management: IVF, electrolyte repletion, cooling

Heat syncope

  • Mechanism: vasodilation resulting in hypotension
  • Management: IVF, cooling, rule out alternative etiologies

Heat exhaustion

  • Mechanism: similar to heat cramps
  • Symptoms: influenza-like, headache, fatigue, dizziness, nausea, normal mental status distinguishes from heat stroke
  • Findings: temperature <40°C
  • Management: IVF, cooling

Heat stroke

  • Mechanism: similar to heat cramps
  • Symptoms: prodrome of heat exhaustion
  • Signs: AMS, ataxia, seizure
  • Findings: temperature >40°C
  • Mortality: 30-80%
  • Labs: AST/ALT, coagulopathy, DIC, rhabdomyolysis, ATN/AKI
  • CXR: pulmonary edema
  • Types
    • Classical: elderly, dry skin, mild dehydration, increased mortality
    • Exertional: young athlete, diaphoretic, increased morbidity (organ failure)
  • Management
    • Evaporative cooling
    • Ice packs to large vessels
    • GI lavage
    • Liberal intubation
    • Benzodiazepines or thorazine for inappropriate thermogenesis (shivering)
    • Halt cooling at 40°C

Hypothermia

Overview

  • Risk factors
    • Extremes of age
    • Behavioral: psychosis, intoxication
  • Types
    • Chillblains
    • Immersion foot
    • Frostnip
    • Frostbite
    • Generalized

Hypothermia

Chilblains

  • Findings: red/white plaques on extremities
  • Symptoms: pruritus, pain
  • Management: supportive (gentle warming), topical corticosteroids, consider nifedipine

Immersion foot (trench)

  • Mechanism: prolonged immersion in non-freezing water, vasoconstriction leads to ischemia/necrosis
  • Findings: pale, mottled skin, paresthesia
  • Management: supportive, drying and rewarming
  • Complications: gangrene

Frostnip

  • Retrospective distinction from frostbite after rewarming if no tissue loss

Frostbite

  • Mechanism: extracellular then intracellular crystal formation (mechanistically similar to crush injury)
  • Reperfusion: cellular injury triggers cytokine release upon reperfusion, results in microvascular thrombosis and tissue ischemia/necrosis
  • Classification: grades I-II superficial to dermis, grades III-IV involve subcutaneous tissue to bone
  • Management
    • Rapid rewarming (immersion in warm water at 41°C)
    • Tdap
    • Debridement of clear blisters

Generalized

  • Causes
    • Exposure
    • Metabolic (adrenal, thyroid, hypoglycemia)
    • Sepsis
  • Grading
    • Mild (32.2-35°C)
      • Findings: excitation, tachycardia, hypertension, shivering thermogenesis
    • Moderate (30-32.2°C)
      • Findings: ataxia, AMS, bradycardia, hypotension, bradypnea
      • ECG:  Osborn wave
    • Severe (<30°C)
      • Complications
        • Increased risk of arrhythmia (bradycardia, slow atrial fibrillation, ventricular fibrillation, asystole)
        • Irritable myocardium
        • Decreased enzymatic activity
          • Renal: cold diuresis
          • Heme: coagulopathy (hidden on labs as blood rewarmed prior to testing)
          • Metabolic: hyperglycemia as insulin ineffective
      • Management
        • Ventricular fibrillation: attempt one shock, then focus on rewarming if ineffective
        • Goal >30°C

Radiation Exposure

Physics

  • Units
    • Gray (amount of radiation absorbed by body)
    • Sievert (toxicity associated with radiation exposure)
  • Types
    • Alpha: 0.1mm penetration, injury through ingestion
    • Beta: 1cm penetration, injury through skin or ingestion
    • Gamma: deep penetration
  • Factors
    • Time and distance (1/d2)
    • Shielding
    • Radiosensitive cells (rapidly dividing such as hematopoetic, GI)

Injury

  • Localized: epilation or burns, delayed by days
  • Internal (inhaled, ingestion)
    • Radioactive iodine: high dose results in thyroid ablation, low dose increases risk of thyroid malignancy
  • External: managed by removing clothing, soap/water shower
  • Whole body (gamma)
System Dose Time of onset Signs/Symptoms
Hematopoetic 2G 2d Pancytopenia, increased risk of infection
GI 6G Hours Nausea/vomiting, diarrhea, GI bleeding
CV/CNS 10G Minutes Shock, seizure

Key clinical features

  • Multiple affected individuals with nausea/vomiting suggests radiation exposure
  • Rapidity of onset of symptoms suggests increased dose/exposure
  • LD505G
  • Prognosis by lymphocyte count
    • ALC >1000 at 48h suggests good prognosis
    • ALC <300 at 48h suggests poor prognosis

Submersion Injury

Pathophysiology

  • Breath-holding until eventual involuntary gasp which triggers reflexive laryngospasm. Resultant loss of consciousness may cause laryngeal relaxation and aspiration.
  • Fluid aspiration results in decreased surfactant activity and atelectasis. This is complicated by V/Q mismatch and atelectrauma which can lead to ARDS.

Symptoms

  • Progressive respiratory distress
  • AMS: due to cerebral hypoxia
  • Shock: uncommon, consider trauma

Management

  • Albuterol
  • BiPAP
  • Endotracheal intubation
  • ECMO

Disposition

  • Asymptomatic or minor event: observe 2-3 hours
  • Mildly symptomatic: observe 4-6 hours
  • Hypoxia: admit
  • PPV: ICU