Environmental Disorders Flashcards
Pathophysiology of decompression sickness
Metabolically inert gas dissolved in body tissue under pressure precipitating out of solution (joints, lungs, vessels) and forming bubbles during decompression
Risk factors for decompression sickness
- Increasing depth of dive
- Rapidity of ascent
- Multiple dives in same day
- Air flight soon after dive
- Obesity (nitrogen is fat soluble)
Clinical picture of decompression illness
- Onset usually within 6 hours, but may occur only after air travel, particularly if within 24 hours of last dive
MSK: arthralgias and myalgias “the bends”
PULM: dyspnea, chest pain, cough “the chokes”
NEURO: vertigo, tinnitus, nausea “the staggers”
SPINE: paresthesias, paralysis
DERM: pruritus, burning, mottling (purpura marmorata), erysipelas-like rash over fatty areas
Tx for decompression sickness
If only msk or derm manifestations can treat with IVF, 100% O2, and ASA
If pulm, neuro, or vestibular manifestations - hyperbarics
Clinical picture of arterial gas embolism
- Sudden onset (within 10-20 mins of ascent)
- Affects brain but spares spinal cord
- Can occur with short and shallow dives
- Dyspnea, hemoptysis, chest pain
- MI
- Stroke
Sx may resolve spontaneously as air bubbles are forced into venous system by spike in cerebral blood pressure - but still require tx as there is a high risk of recurrence! - Requires immediate hyperbaric therapy
Which congenital defect increases prevalence of decompression sickness?
Patent foramen ovale
Symptoms from dysbarism of descent
Ear pain - air is trapped in enclosed spaces and causes local trauma due to increased pressure at depth and “squeeze” - Eustachian tube dysfunction causing pain, hematoma, TM rupture, vertigo in middle ear or possible rupture of round window in inner ear causing hearing loss, vertigo, tinnitus
Epistaxis - if sinus ostia are obstructed and air is trapped
Petechial rash - air between skin and diver’s dry suit
Dental pain - trapped air in cavity fillings may cause severe dental pain
Hemoptysis from rapid descent (rare); PTX, pneumomediastinum from rapid ascent
NOT part of decompression sickness
How can you differentiate joint pain from decompression sickness from other MSK pain?
Joint pain of decompression sickness is typically unrelieved but not worsened with movement
What is the most commonly used method of estimating dose exposure and prognosis in acute radiation syndrome?
Andrews lymphocyte depletion curves - level of lymphocytes over 48 hours
Which body system is most sensitive to effects of radiation?
Hematopoietic system followed by GI system
What medication may be administered to prevent absorption of radioactive material by thyroid gland?
Potassium iodide
Black widow vs. Brown Recluse
Identifying feature, venom, clinical effects, tx, antivenin
Q#441388 table
Venom of black widow
Neurotoxin - causes release of acetylcholine and norepinephrine at nerve terminals
Clinical effects of black widow venom
- Severe muscle cramping (typically abdominal wall, back, and legs)
- CNS and peripheral nerve hyperactivity
—> dizziness, restlessness, profuse sweating, difficulty speaking, ptosis, HTN, tachycardia
Tx for black widow envenomation
- Supportive with opioids and benzos
- Antivenin reserved for severe symptoms (autonomic instability and hemodynamic collapse) due to risk of anaphylaxis and serum sickness as it is derived from equine serum
Alkali burns cause what kind of necrosis?
Liquefactive
Acidic burns cause what kind of necrosis?
Coagulation necrosis
Spectrum of clinical presentation in heat exposure
- Heat Cramps
- Inadequate intake of fluids and electrolytes
- Muscle cramping of calves and abdomen - Heat Exhaustion
- Dehydration
- N/V
- General weakness
- May have temperature, but <104 - Heat Stroke
- Mental status change
- Organ damage
- Anhidrosis (not universal)
- Temperature >104
What animal in the US has the greatest incidence of rabies?
The bat
Pathophysiology of arterial gas embolism
Rapid decrease in ambient pressure caused by ascent from high-pressure environment of a deep dive to atmospheric pressure results in precipitation of air bubbles, which then embolize systemically
What lab test is almost universally abnormal, and remains so the longest, in patients with heat stroke?
LFTs
Tx for heat stroke
Rapid cooling to 39C within 10-20 mins; evaporative or cold water immersion
Avoid antipyretics
Why do drugs become ineffective during hypothermia?
Increased protein binding
Degree of hypothermia and characteristics
Mild (33-35C) - amnesia, dysarthria, shivering
Moderate (29-32C) - stupor, dysrhythmias, decreased level of consciousness, shivering extinguished
Severe (22-28C) - v-fib susceptibility, loss of reflexes, pulmonary edema, decreased cerebral blood flow
Profound (9-20C) - flat EEG, asystole
Tx of hypothermia
Mild: passive rewarming
Severe without CV instability: active external rewarming
Severe with CV instability: invasive core rewarming
Middle ear barotrauma 2/2 diving is due to ascent or descent barotrauma?
Descent - most common complaint of scuba divers
When is nitrogen narcosis most likely to occur?
Depths greater than 100 ft, but can occur at shallower depths. Ascent reverses symptoms
What is the most common cause of death from high altitude illness?
High Altitude Pulmonary Edema
Clinical progression of high altitude pulmonary edema
Initial (2-4 days after arrival at new altitude)
- subtle, nonproductive cough, dyspnea on exertion
Progression
- dyspnea at rest
- clear or pink frothy sputum
- tachycardia, tachypnea, fever
- pulse ox 10 points lower than expected for altitude
Cxrs progress from interstitial to localized alveolar and then generalized alveolar infiltrates
Management of high altitude pulmonary edema
- Immediate descent is definitive tx of choice
- Supplemental oxygen
- Nifedipine
- Portable hyperbaric chamber
What animal envenomation is associated with heightened sensitivity to touch in the affected area, along with local numbness and weakness?
Scorpion
Clinical features of scorpion bites
- Local reaction with edema and erythema
- Heightened sensitivity to touch in area of sting
- Local numbness/weakness
Systemically: - anxiety/restlessness
- muscle spasms
- n/v
- excessive salivation
- diaphoresis
- hyperthermia
- myoclonus
- hemiplegia
- syncope
Criteria for 4-6 hours of observation after submersion/drowning event
- No evidence of respiratory distress or pulmonary compromise (rales, rhonchi, retractions)
- O2 saturation >95% on room air
- GCS > 13
What is the mammalian diving reflex?
Body is submerged in cold water, reflexive bradycardia and peripheral vasoconstriction
Clinical presentation of arterial gas embolism
- LOC on ascent or within 10 min of surfacing
Coronary: dysrhythmias, MI, cardiac arrest
Cerebral: focal motor, sensory, visual deficits, seizures, death
Musculocutaneous: cyanotic marbling and focal pallor of tongue
Kidney: hematuria, proteinuria, renal failure
Uterine and GI bleeding
Management of arterial gas embolism
- Immediate 100% O2 and IVF to improve tissue perfusion and oxygenation
- Place patient in supine position
- Hyperbaric oxygen
What is the cause of the symptoms of heat exhaustion?
Dehydration and hyponatremia cause cramping, nausea, dizziness, tachycardia, orthostatic hypotension (NOT core body temperature)
In non-fatal drowning incidents, what are criteria for patients able to be observed 4-6 hours and discharged from ED?
- GCS > 13
- Normal pulmonary exam or only mildly symptomatic with normal CXR
- O2 saturations >94% on ED arrival
What intervention needs to occur within 30 minutes for heat stroke?
Rapid cooling with goal temperature of 38.9 (102F)
No danger in rapid cooling - evaporative methods are safe and fast - continually wet patient with tepid water while fanning skin. Immersion in ice water baths also effective
What is the role of benzodiazepine in hyperthermia?
To manage agitation and shivering (due to rapid cooling)
What is the importance of type of fluid medium (fresh vs. salt water) in submersion injury?
Type of fluid does not have clinical relevance
What is chilblains?
- Also called pernio
- Inflammatory skin lesions precipitated by protracted and intermittent exposure to damp, non-freezing ambient temperatures
- Localized edema, erythema, cyanosis, nodules, rarely ulcerations and bullae
- Pruritus, numbness, burning paresthesias
Associated disorders with chilblains - “Secondary pernio”
- Hematologic disorders
- Autoimmune disease
- Viral hepatitis
- Malignancy
What physical exam finding is classically associated with a brown recluse spider bite?
A “bull’s eye” lesion with circumferential erythema and a necrotic center
What causes high altitude pulmonary edema?
High microvascular pressure in pulmonary arterial bed
What is the most lethal illness of high altitude?
High altitude pulmonary edema
Patients with anaphylaxis to which antibiotics should avoid acetazolamide?
Sulfa (although risk of cross-reactivity very low)
What is the initial neurologic finding in patients with heatstroke?
Ataxia
What is the primary enzyme responsible for necrosis caused by brown recluse spider bites?
Phospholipases D
What may help prevent local effects of envenomation from brown recluse spiders if given within 48 hours of bite?
Dapsone, but otherwise local wound care is primary management
What is the toxic component of black widow spider bites?
Alpha-Latrotoxin
Chilblains vs. immersion foot vs. frostbite
Find the questions and organize better
Elapidae species snakes
- Coral
- Cobra
- Kraits
- Mambas
- Sea snakes
- Pygman copperhead
Envenomation by elapidae snakes
Minimal local reaction with marked systemic neurotoxicity - salivation, dysarthria, diplopia, ptosis, miosis, dysphagia, seizure
Death from respiratory failure
Symptoms may be delayed several hours
Pathophysiology of envenomation of elapidae family snakes
Venom irreversibly binds acetylcholine receptors
Viperidae family of snakes
Also called crotalids
- Rattlers
- Cottonmouths
- Copperheads
- Western diamondback
Effects of envenomation by viperidae family of snakes
Local effects - very painful, edema, erythema, bullae, rhabdomyolysis
Systemic - weakness, paresthesias, metallic taste, chest pain, dyspnea
Hematologic - coagulopathy, thrombocytopenia, bleeding, rhabdomyolysis
Management of Viperidae family bites
- Observe “dry” bites for 8 hours prior to discharge
- Otherwise crofab (sheep product with few allergic manifestations)
Management of bite from elapidae family snake?
Antivenom for all symptomatic eastern coral snake bites, otherwise supportive care
But all require admission for observation
What exposure can bypass decontamination and should be immediately assessed for systemic toxicity?
Chlorine gas and all other fully dispersed gases
What is most sensitive sign of high altitude cerebral edema?
Cerebellar ataxia
What is most likely to determine the degree of pulmonary insult suffered by patient with submersion injury?
Amt of liquid aspirated
