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Environmental Board Review

Environmental Board Review. Raghu Seethala MD 12/3/2008. Environmental. 12/410 questions from PEER VII (3%) Some overlap with toxicology and trauma. Question 1.

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Environmental Board Review

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  1. Environmental Board Review Raghu Seethala MD 12/3/2008

  2. Environmental • 12/410 questions from PEER VII (3%) • Some overlap with toxicology and trauma

  3. Question 1 Which of the following abnormal test results is the earliest indicator of biological damage from whole-body penetrating irradiation? • Anemia RBC’s decrease to a lesser extent and later • Eosinophilia Characteristic of parasitic infections not radiation • Leukopenia Initial increase followed by a decrease that reaches a nadir at 30 days • Lymphopenia • Thrombocytopenia Initial increase followed by a decrease that reaches a nadir at 30 days

  4. Radiation Injuries • Types of ionizing radiation • Alpha, beta, neutrons, gamma and X-rays • Units of radiation • Gray (Gy) 1 Gy = 100 rad • Sieverts (Sv), 1 Sv = 1 Gy • Lethal dose of radiation • LD 50 = 4.5 Gy (abdominal CT is about 0.01 Gy) • Types of radiation exposure • External contamination • External irradiation • Internal contamination

  5. Radiation Injuries • Acute radiation syndrome • Prodromal phase, followed by latent phase • Manifest illness phase • Hematopoetic syndrome • Seen in doses above 1.5 – 2 Gy • Results from bone marrow depression • Decrease in lymphocytes first within 8 – 48 hours, then leukopenia, thrombocytopenia within several weeks • Lymphocyte counts at 48 hours are prognostic • > 1200/mm3 good, < 300/mm3 poor • Gastrointestinal syndrome • Nausea, vomiting, diarrhea within hours • Cardiovascular and CNS syndrome • Immediate nausea, vomiting, prostration, hypotension, universally fatal death within 24 – 72 hours

  6. Radiation Injuries • Treatment • Alleviating symptoms • Antiemetics, pain medication • Supportive care • IVF, blood products, TPN, reverse isolation, antibiotics, antifungals, colony stimulating factors • Specific therapies for internal contamination • Prussian blue - Cesium-134 or 137, Thallium • Potassium iodide - Iodine-125 or 131 • Chelating agents (Zn or Ca-DTPA) - plutonium, americium, curium, californium, and other transuranium elements

  7. Question 2 A 40 year old man passed out while using a gas powered cement cutter in his garage with the doors closed. His wife called 911; paramedics placed him on oxygen with a nonrebreather mask and transported him to the emergency department. On arrival he says he has only nausea and a mild headache. A venous blood COHb level of 20% confirms carbon monoxide poisoning; detailed neurologic examination is normal. The hospital’s hyperbaric oxygen chamber is available. What is the rationale for using it to treat this patient.

  8. To correct presumed associated metabolic alkalosis more rapidly Hyperbaric can correct a metabolic acidosis more rapidly B. To decrease the COHb level more rapidly Hyperbaric does decrease COHb more rapidly but that is not the reason to use in this situation C. To decrease the likelihood of death Does not improve mortality D. To decrease the likelihood of delayed neurologic sequelae • To prevent the development of cardiac dysrhythmias. Does not prevent dysrhythmias

  9. Carbon Monoxide Poisoning • Results from incomplete combustion of any fossil fuel • Northern climates in the winter months • CO competes with oxygen at binding sites on hemoglobin, myoglobin, and cytochrome aa3, thus interfering with oxygen delivery and utilization • Flu-like symptoms, headache, dizziness, nausea, vomiting. Severe symptoms include dyspnea, altered mental status, coma, seizures • Can develop persistent or delayed neurologic sequelae resulting in memory deficiency, chronic headaches, parkinsonism. • Levels don’t correlate well with symptoms. Normal non-smokers 1% – 2%, smokers 5% - 10%.

  10. Carbon Monoxide Poisoning • Treatment • High flow 100% oxygen • Hyperbaric oxygen treatment Definite Indications -Altered mental status, coma -Abnormal neuro exam -Syncope -Seizure -Myocardial ischemia Relative Indications -Persisting neuro symptoms After 4 hours of tx with 100% O2 -Persisting acidosis -Absolute level of >25% -Pregnant with level >15% HBO therapy more rapidly decreases COHb and more rapidly corrects acidosis. No evidence that HBO decreases mortality or prevents dysrhythmias. Some evidence exists that it can prevent delayed neurological sequelae.

  11. Question 3 A 22 year old man presents by ambulance with a depressed level of consciousness; his roommate found him lying in the yard that morning after their school’s football team won its bowl game. He has preserved airway reflexes, is unresponsive, has no signs of traumatic injury, and has a blood pressure of 100/60. Blood glucose is normal, and serum ethanol is 240 mg/dL. Figure 10 is a tracing from the cardiac monitor. Which of the following interventions is indicated.

  12. Administration of atropine Pt is hemodynamically stable, and ACLS meds do not work that well in hypothermic pt’s B. Administration of sodium bicarbonate Tx for hyperkalemia, ASA toxicity, TCA toxicity C. Hyperbaric oxygen therapy Tx for CO poisoning, diving complications D. Intravenous steroids No role for steroids in hypothermia E. Rewarming techniques

  13. Hypothermia • Associated with extremes of age, alcohol, drug intoxicated, psych patients • EKG – Osborn J waves • Positive deflection at the junction of the QRS and ST segment. Height varies inversely with temp. • Cardiac rhythm progresses from – tachycardia -> bradycardia -> A-fib with a slow rate -> Vfib -> asystole

  14. Hypothermia • Treatment • Passive rewarming • Active external rewarming • Warm water immersion, heating blankets • Active core rewarming • Heated IVF, GI lavage, bladder lavage, peritoneal lavage, pleural lavage with saline heated to 42o C • Cardiac arrest patients • V-fib is usually refractory to defibrillation when temp < 30o C • ACLS medications don’t work well when temp < 30o C • Rewarming through extracorporeal circuit

  15. Question 4 Paramedics covering a marathon event call in for medical direction in their care of a runner who collapsed halfway through the race. He is disoriented and slightly diaphoretic and has a rectal temperature of 41oC (105.8oF). Rapid diagnostic testing reveals normal serum sodium and blood glucose levels. They are 1 hour from the nearest emergency department. What is the most effective immediate treatment?

  16. Administer acetaminophen No role for acetaminophen in heat stroke • Peform ice water immersion • Place him in the shade until he recovers Pt has heat stroke and needs aggressive cooling immediately • Place ice packs on his axillae and groin Pt has heat stroke and needs more aggressive measures, these can be used as adjuncts E. Transport to the emergency department, where evaporative cooling can be performed Pt is 1 hour from the nearest ED and needs to be cooled immediately to decrease morbidity and mortality

  17. Heat Emergencies • Risk factors: children, elderly on medications that decrease sweating (B-blockers), psych pt’s (on anticholinergics) cocaine use • Spectrum of disease including heat edema, prickly heat, heat tetany, heat syncope, heat exhaustion, heat stroke. • Cooling is treatment and should be initiated immediately, mortality increases significantly when it is delayed

  18. Heat Emergencies • Heat stroke – body temp above 40oC and CNS dysfunction (convulsion, coma, delirium) • Classic – Elderly w/ MMP, mortality is high because of chronic medical conditions, usually don’t get all heat related complications • Exertional – young athletes or military, high complication rate but low mortality rate • Rhabdo, ARF, hyperkalemia, hypocalcemia, hyponatremia, DIC • Tx: “wind and water,” evaporative cooling most effective – large fans with skin wetting • ice water immersion effective also • If shivering give benzos • Acetaminophen no role in heat stroke

  19. Question 5 Regarding submersion injuries, which of the following statements is correct? • Complete recovery in 48 hours is typical of submersion victims who never require CPR • Electrolyte measurement should be routine Electolyte abnormalities are rare, except if pediatric in freshwater or if aspirate water w/ high solute conc. (Red Sea) • Prolonged attempts at resuscitation of asystolic pediatric patients after warm-water submersion should be pursued Asystole at the scene or in ED is a sign of poor prognosis in warm water pediatric submersions • Prophylactic antibiotics are usually indicated Bacterial pneumonia is rare after near-drowning E. The Heimlich maneuver is of proven efficacy in removing aspirated fluid Heimlich is good for removing particulate matter in upper airway, not aspirated water in lungs

  20. Submersion Injuries • Drowning – submersion injuries that result in death in 24 hours • Near drowning – survival of greater than 24 hours after submersion event • Secondary drowning – death following initial recovery • Wet drowning – aspiration of water • Dry drowning – asphyxia due to laryngospasm (no aspiration) • Electrolyte abnormalities are unusual except in cases of aspiration of water with very high solute concentration (Dead Sea) • Pulmonary and CNS damage determine outcome

  21. Submersion Injuries • Asymptomatic individuals with normal O2 sat. and pulmonary exam after 4 -6 hours of observation can be d/c home. • Bacterial pneumonia is rare after submersion, so prophylactic antibiotics are unnecessary • Asystole at the scene or in ED is a sign of poor prognosis in warm water pediatric submersions. So prolonged resuscitation attempts should not be pursued • Several cases of complete neuro recovery in icy-watersubmersion even after asystole. In these cases prolonged resuscitative efforts are reasonable.

  22. Question 6 A 4 year old boy presents after sticking a fork into a home electrical outlet with his right hand and getting shocked. His right elbow was on the ground at the time. Although he cried initially, he has remained asymptomatic. Physical examination reveals two extremely small first-degree burns on his right hand and elbow; a 12-lead ECG is normal. The most appropriate disposition.

  23. Admit to a monitored bed for 24 hours Pt is asymptomatic and normal EKG, risk of delayed arrhythmia is low with household voltage • Admit to a nonmonitored bed for serial peripheral vascular examinations Indicated for significant injuries from high voltage contact, not this pt. • Discharge home • Observe in the emergency department for 6 hours; if no dysrhythmias occur, discharge home Pt is asymptomatic and normal EKG, risk of delayed arrhythmia is low with household voltage, pt can be safely d/c home • Perform echocardiography in the emergency department No role for routine evaluation in asymptomatic pt. who suffer electric shock

  24. Electrical Injuries • Electrical current is measured in amperes • Current flow is driven by electrical potential which is measured by voltage • DC current – tends to throw victim from source, small entrance wound large exit wound • AC current – more dangerous, can cause tetany causing individual to continually grasp the source, increasing contact time, exit entrance wounds are same size • Conduction - Nerve > blood vessels > muscle > bone

  25. Electrical Injuries • Low voltage AC current (household current) tends to cause vfib and no burns in 40% of deaths • High voltage AC and DC currents tend to cause asystole and respiratory arrest • Oral burns in children may have delayed labial artery bleeding (up to 2 weeks later) • Admit pt’s with shock greater than 600 V because of potentially severe consequences • Asymptomatic patients with household voltage exposure, normal ECG and normal exam can be discharged

  26. Question 7 Which of the following statements regarding lightning strikes is correct? • Absence of pupil reactivity is a reliable examination finding to help confirm brain death Pupillary response can be disrupted after lightening injury • In mass-casualty incidents involving lightning, cardiopulmonary arrest victims mandate highest priority • Lower extremity paralysis is typically permanent Lower extr. paralysis is temporary after lightening injury, unless spinal fx from trauma • Most common cause of death is intracranial injury Intracranial injuries occur but most COMMON cause of death is cardiopulmonary arrest • Vitreous hemorrhage is the most frequently observed ocular sequela Vitreous hemorrhage, corneal abrasions, retinal detachments can occur, but most frequent ophthalmic injury is cataract formation

  27. Lightning Injuries • 30% mortality rate • Mechanism – high voltage DC current, direct strike, side flash, contact strike, ground current, step potential • Physical findings • Clothing disintegration, burns, ferning skin pattern, tympanic membrane rupture, temporary lower extremity paralysis, disrupted pupillary response

  28. Lightning Injuries • Complications • Cardiopulmonary arrest is most common cause of death • Cataracts are the most frequent ophthalmic injury • Prolonged respiratory arrest can occur • Reverse triage because resuscitation is often successful from cardiopulmonary arrest

  29. Question 8 With regard to arterial gas embolism and decompression sickness associated with diving, which of the following is correct? • Almost all cases of arterial gas embolism occur within the first 10 minutes of surfacing • Decompression sickness results from the formation of small oxygen bubbles in the blood and tissues Nitrogen bubbles!! • Decompression sickness will not develop unless the victim experiences barotrauma Not true! • Loss of consciousness in CNS decompression sickness is common Loss of consciousness after resurfacing should point to arterial gas embolism! • Only arterial gas embolism requires recompression therapy Not true! Both decompression sickness and arterial gas embolism require recompression.

  30. Dysbarism and Diving Complications • Boyle’s Law – pressure and volume vary inversely • Henry’s Law – at equilibrium quantity of gas in solution is proportional to partial pressure of gas • Barotrauma • middle ear squeeze – ear pain, TM perforation • Inner ear barotrauma – tinnitus, vertigo, hearing loss • reverse squeeze – occurs during ascent from volume expansion • tooth squeeze – painful, air filled dental cavities • pulmonary overpressurization syndrome – expansion from unvented gases during ascent - alveolar rupture, PTX, pneumomediastinum

  31. Dysbarism and Diving Complications • Air embolism • Most severe result of pulmonary barotrauma. Gas bubbles enter pulmonary venous circulation and embolize to brain and heart. • Symptoms occur immediately after surfacing - syncope, seizure, hemiplegia, apnea • Tx – recompression therapy in hyperbaric chamber • Decompression Sickness • Dissolution of nitrogen bubbles during ascent, which then accumulate in tissue and joints • Type I (the bends) – involves joints, extremities, skin • Sx: deep pain in joints, commonly knee or shoulder • Type II – more severe, involves CNS usually SC • Sx: patchy parasthesias, ataxia, bladder dysfunction • Tx – recompression therapy

  32. Question 9 A 20 year old man presents after being bitten on the hand by his pet rattlesnake. He feels nauseated and describes a metallic taste, and he has a pain around the bite site. Vital signs are normal. CBC reveals a platelet count of 45,000/mm^3. What is the most appropriate management? http://www.venomous.com/snake/armpic.jpg

  33. Administration of antibiotics Infections are unusual after most rattle snake envenomations • Administration of antivenin • Administration of platelets May be required later if antivenin doesn’t work, but antivenin 1st line tx • Placement of a tourniquet on the arm Torniquet that decreases arterial flow is likely to worsen outcome. • Prophylactic fasciotomy of the forearm Antivenin tx is first line, even with elevated compartment pressures fasciotomy is controversial; prophylactic fasciotomy is likely to cause much more harm than benefit

  34. Snake Bites • Crotalidae – rattle snakes > water mocassins > copper heads • Local injury – swelling, pain, ecchymosis, watch for compartment syndrome • Systemic effects – nausea, metallic taste, hypotension, tachycardia, coagulopathy • Tx – CroFab antivenin, check coags,immobilize ext., local wound care • Pitfalls – early fasciotomy, not enough antivenin • Sx can occur 30 min – 12 hours, may d/c if asymptomatic after 8 hours • Coral Snakes • “Red on yellow kill a fellow” • “Red on black friend of jack” • Neurotoxin – tremor, seizure, resp. paralysis, bulbar palsy • Admit to hospital, observe 24 – 48 hr, antivenin

  35. Question 10 What is the MOST common finding in a patient with a brown recluse spider bite? • Severe itching Brown recluse bite usually delayed pain, not itching. B. Local tissue necrosis C. Severe muscle cramps Black widow bite causes this. D. Anaphylaxis Hymenoptera (Bees, wasps) sting more commonly causes this.

  36. Spider bites • Brown Recluse (loxosceles reclusa) • Found in dark spaces, attics, woodpiles, closets • Delayed pain, local tissue necrosis • Loxoscelism – systemic reaction, 1 -2 days s/p enevenomation • Fever, chills,vomiting, myalgias, hemolysis, ARF, DIC • Tx – no antivenin in U.S., local wound care, surg. f/u, dapsone and hyperbaric to prevent necrosis are controversial • Black Widow • Immediate pain, erythema, swelling, muscle cramps and spasms • Abd. Wall muscle pain mimics acute abdomen • Systemic - HTN, resp. failure, coma, shock • Tx: Benzos relieve spasm, antivenin for severe envenomation

  37. Question 11 Which of the following is TRUE regarding marine envenomations? • Jellyfish nematocysts are inactivated by fresh water rinsing Fresh water causes further envenomation • Sponge dermatitis is treated with antibiotics against gram-negative organisms Inflammatory reaction treated with antihistamines • Hot water immersion is an effective pain reliever for venomous fish and stingray injuries • Tetrodotoxin poisoning from an octopus bite may be reversed with antivenin No antivenin exists for tetrodotoxin, supportive care only, usually full recovery

  38. Marine Envenomations • Invertebrates • Jellyfish, box jelly fish, potugese man of war, sponges, starfish • Vertebrates • Stingrays, venemous fish, sea snakes • Basic info • Hot water immersion relieves pain • Fresh water immersion can make pain worse • Deactivate nematocysts with acetic acid (Vinegar) • Remove remaining spicules, tentacles, spines etc. • Antivenin available for box jellyfish, certain sea snakes • No antivenin for tetrodotoxin

  39. Question 12 The physical sign or symptom that would distinguish acute mountain sickness from high-altitude cerebral edema is: • Ataxia • Dizziness • Fatigue • Headache • Hypoxia

  40. High Altitude Sickness • 17% – 40% occur 7200 ft – 9000 ft • Acute mountain sickness • Pathophysiology – hypoxia -> increased cerebral blood flow -> increased cerebral hydrostatic pressure -> fluid shift -> cerebral edema • Lightheaded, dizzy, hangover, headache, nausea • Prevention – gradual ascent, avoid etoh, incr. carb diet. • Tx: descend, nocturnal low flow O2, acetazolamide – bicarb diuresis -> met. acidosis -> stimulates ventilation -> acclimatization response

  41. High Altitude Sickness • High altitude cerebral edema (HACE) • Severe progression of AMS, usually at > 12,000 ft • Sx: mental status changes, confusion, ataxia, neurologic symptoms • Tx: Immediate descent, Dexamethasone, O2 • High altitude pulmonary edema (HAPE) • Most common cause of death in altitude illness • Pathophys: exaggerated hypoxic pulmonary vasoconstriction -> incr. pulm. hydrostatic pressure • Signs and symptoms: cough, SOB,tachycardia, tachypnea, rales, • Tx: Immediate descent, O2, Nifedipine, Lasix

  42. The End

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