Environmental

Altitude Sickness

/ fbfbar25 / Leave a comment
Lecture by Dr. Mansi Nayak
Summary by Fernando Barajas, PGY-2
Overview
Different responses to altitude grouped as follows:
(1) High altitude (1500-3500 meters):
  • Denver , Aspen, and capitals (Quito, Bogota, Bhutan) are at this altitude
  • Commercial flights are also pressurized to these altitudes
(2) Very High altitude (3500-5500 meters):
  • Altitude of highest inhabited cities and highest capital in the world, La Paz (3700m)
(3) Extreme altitude (>5500 meters):
  • Not able to acclimate to this altitude

altitude550

Physiology
  1. Higher altitude = Lower Patm ~ pO2
  2. Low pO2 → ↑ respiratory rate (mediated by medulla)
  3. Respiratory alkalosis → compensatory metabolic acidosis
  4. In the lung, hypoxia leads to vasoconstriction which leads to vicious cycle as described by (3)
  5. Heme:
    1. Acute ↑ in hematocrit due to volume contraction
    2. Over weeks there is an ↑ in Hgb production

**While all these occur at extremely high altitudes, acclimatization cannot occur with this degree hypobaric hypoxia

Pathophysiology
  1. Acute Mountain Sickness
    1. Cough, periodic breathing of altitude, pHTN, retinal hemorrhage
  2. Acute Altitude Headache
    1. Improves with descent and gets worse with exertion
    2. Can be treated with NSAIDS or tylenol
  3. High Altitude Pulmonary Edema (HAPE)
    1. Presentation: Cough, low grade fevers, dyspnea (out of proportion to activity),
    2. Pathophysiology: Hypoxic vasoconstriction → increased pulmonary arterial pressure → pulmonary edema
    3. Imaging: CXR may show infiltrates
    4. Screen Shot 2016-01-07 at 3.47.32 PMTreatments
      1. supplemental oxygen
      2. Hyperbaric bag (Gamow bag)
      3. Immediate descent
      4. Warming
      5. Salmetrol (lacking evidence)
      6. Nifedipine
      7. Sildenafil
  4. High Altitude Cerebral edema (HACE)
    1. Presentation: Headache, ataxia (often first finding), decreasing levels of consciousness
    2. Pathophysiology: ↑ in blood flow to compensate for hypoxia → vasogenic edema 2/2 blood flow exceeds ability of auto-regulation
    3. Imaging:

Screen Shot 2016-01-07 at 3.52.16 PM

  1. Treatment: Supplemental O2, Hyperbaric treatment, Dexamethasone, Diuretics (Acetazolamide)
  2. Prevention:
    1. Advise against travel to high altitudes if there is a history of pHTN, poorly controlled asthma, poorly controlled COPD, HAPE, or HACE
    2. Acetazolamide started days proper to trop
    3. Graded ascent (600m/day) and sleep at lower altitude than your highest climb
References
Nayak M.  “Altitude Sickness.” Jacobi Medical Center. Jacobi/Montefiore Emergency Medicine Conference. Bronx.  Dec 2015. Lecture
Gallagher SA, Hackett PH. High Altitude Sickness. Emery Med Clin N Am 22 (2004) 329-355

Drowning

/ Maninder Singh, M.D. / Leave a comment

Wednesday Conference
11/11/15
Article Inspired by: Dr. Sui Fai Li and Dr. Andrew Chertoff

THE CASE

20 y/o M BIBEMS after falling into the river. He is pulseless, apneic and cold. He is intubated, and his temperature is 80F. CPR has been in progress for 2 hours. Monitor shows VFib throughout CPR. What do you do?

  • Controversial but keep resuscitating until normothermic (possible neuroprotective effects with hypothermia)

THE TALK

Drowning = “process of experiencing respiratory impairment from submersion/immersion in liquid” as per World Congress on Drowning in 2002

Why is drowning harmful?

  • Initially you can hold breath
  • As some point, due to need for oxygen, will take a deep breath and water will enter airway
  • Clinical picture determined mostly by the amount of water that has been aspirated
    • Water in the alveoli causes surfactant dysfunction and washout
    • Increased permeability of the alveolar-capillary membrane
  • Result = hypoxemia
    • Decreased lung compliance
    • Increased regions of low ventilation to perfusion in the lungs (V/Q mismatch)
    • Atelectasis
    • Bronchospasm

What should I do if I see someone drowning and I am the first person on the scene?

  • Cardiac arrest from drowning is due primarily to lack of oxygen
  • CPR should follow traditional ABC sequence- 5 initial rescue breaths, followed by 30 chest compressions and continuing with 2 rescue breaths and 30 compressions

Should I do the Heimlich maneuver?

  • NO, most frequent complication is vomiting and it delays the initiation of ventilation

How about when the patient is in the Emergency Department?

  • Focus on reversing hypoxemia
    • Non-rebreather mask or nasal cannula if patient is protecting airway
    • If no improvement in 10-30 minutes, intubate
  • If hypothermic, warm them to achieve ROSC and then make a treatment decision
  • ECMO is single most effective way to warm someone, especially if cardiac dysrhythmia
  • CXR in any drowning patient with respiratory systems but initial CXRs usually do not provide prognostic value
  • Be careful about the circumstances (i.e fell off a bridge- now have to worry about trauma related injuries in addition to the drowning)

Is there a way to classify patients?

  • Grade 1 = coughing but normal auscultation
  • Grade 2 = abnormal auscultation; rales in some fields
  • Grade 3 = acute pulmonary edema without arterial hypotension
  • Grade 4 = acute pulmonary edema with arterial hypotension
  • Grade 5 = isolated respiratory arrest
  • Grade 6 = cardiopulmonary arrest

When should I admit a patient?

  • Grade 2 to 6 presentation
  • However, for grade 2, can also place on noninvasive oxygen and if oxygenation normalizes, could discharge after 6-8 hours of observation

Can I send someone home who has had “nonfatal drowning?”

  • Awake and look okay (good arterial oxygenation, no need for supplemental oxygen and no other associated injuries) – check lungs and can be discharged

How should I manage these patients?

  • Neurological
    • Keep head of bed raised
    • Low to normal CO2
    • MAP of 80mmHg
    • Benzodiazepines for seizures
  • Respiratory
    • Protective lung ventilation to prevent ALI and ARDS
    • Bronchodilation
    • ECMO
  • Metabolic
    • Severe metabolic acidosis from lactate
    • Rhabdomyolysis
  • Cardiovascular
    • Extravasation of systemic and pulmonary capillaries + cold diuresis -> hypovolemia
    • SIRS post resuscitation, often require cardiac output monitoring
  • Infection
    • Consider antibiotics if submerged in grossly contaminated water

Terminology

  • Dry drowning
    • Those who do not aspirate liquid into the lungs
  • Wet drowning
    • Aspirate liquid into the lungs
  • Secondary drowning
    • Unrelated event (seizures, cervical spine injury or heart attack) that results in the submersion and subsequent drowning
    • Development of ARDS in recovering victim
  • Freshwater drowning VS Seawater drowning
    • Similar degrees of lung injury, despite difference in osmotic gradients
    • You usually don’t swallow enough water to make any difference to your vascular system
  • Afterdrop Phenomenon
    • When applying external heat to the body, return of pooled, cool blood from previously vasoconstricted extremities -> further lower core temperature = afterdrop
    • Rewarming of trunk first may prevent problem by allowing warm blood to perfuse distally constricted cold extremities
    • More common in dehydrated patients and in patients with frostbitten extremities

REFERENCES

Li, S. “Conference: Drowning” Jacobi Medical Center. Jacobi/Montefiore Emergency Medicine Conference. Bronx. Nov 2015. Lecture

Chertoff, A. “Conference: Drowning Jeopardy” Jacobi Medical Center. Jacobi/Montefiore Emergency Medicine Conference. Bronx. Nov 2015. Lecture

Borghei, Sam, MD, Mizuho Spangler, DO, and Andrew Schmidt, DO. “Drowning Resuscitation.” July 2015. EM:RAP.

Nickson, Chris. “Drowning.” Drowning. LITFL Life in the Fast Lane Medical Blog

Electrical Injuries

/ Maninder Singh, M.D. / Leave a comment

Wednesday Conference
11/11/2015
Article Inspired By: Dr. Sui Fai Li and Dr. Andrew Chertoff

-Very little hard data as there are no randomized control trials and mostly just case series

-The first thing to do when someone presents with an electrical injury is to undress the patient and look for any burns/injuries

-Usually, if they present with just numbness, it will resolve

Classification:

  • Low Voltage Injuries
    • Household electrocutions
  • High Voltage Injuries (>1000V)
    • Occupational, Public transit, Transformers

Pathophysiology:

  • Damage done depends on:
    • Amperage (amount)
    • Duration
    • Voltage (force)
    • Resistance
    • and maybe Pathway
  • Amp X Resistance = Volt
    • Higher voltage = higher amperage
      • Household (U.S.) = 120V
      • Public Transit (Subway ~600 to Overhead ~15,000V)
      • Substations ~11,000-400,000V
    • Dry skin 10-40x more resistant than wet skin
    • Alternating current (AC) can be three times worse than Direct current (DC)
      • High-voltage DC is usually a single muscle spasm
      • Alternating current causes prolonged/continuous muscle contraction and tetany leading to longer electrical exposure

What type of injuries can you see with electricity?

  • Trauma
  • Thermal injury
  • Electrical injury
  • Burns
    • Arc burns
    • Crease burns

What organ systems do I have to worry about?

  • Neurological
    • LOC, transient paralysis, or paresthesias
    • Keraunoparalysis (fixed, dilated pupils; lower extremity cyanosis; paralysis from vasospasm)
      • Classically with high voltage lightning injuries
      • Continue resuscitation for prolonged period of time despite fixed, dilated pupils
    • Most permanent injuries are secondary events
  •  Cardiac
    • A/C induces ventricular fibrillation whereas D/C induces asystole
      • Lightening causes massive direct countershock which depolarizes entire myocardium causing asystole
    • Cardiac contusion common
    • Acute MI is rare
  • Vascular
    • Thrombosis/hemorrhage
    • Labial artery
      • Usually 3rd degree, 6-20% bleed, need referral to specialty
  • Ophthalmology
    • Lightning strike associated cataracts (need good follow-up)
  • Respiratory- Aspiration
    • Lightning can induce paralysis of medullary center leading to primary respiratory arrest
  • Musculoskeletal
    • Rhabdomyolysis
    • Compartment syndrome
  • Obstetrics
    • Stillbirths
    • Lightning strikes – fetal mortality close to 50%
      • First trimester- confirm fetal heart tone, d/c with spontaneous abortion precautions
      • Second/Third trimester- OB for fetal monitoring and significant risk for placental abruption

Okay, what should I do in the trauma bay?

  • Airway
    • May require intubation if intubated, major burns or for specific treatment (suxamethonium safe for 48 hours)
  • Breathing
    • Lung protective ventilation strategy
    • Look for same life threatening chest injuries as in trauma patients
  • Circulation
    • Prevent effects of rhabdomyolysis (hyperkalemia, hypocalcemia, hyperphophatemia, metabolic acidosis)
    • Restore normal circulating volume
      • May require ionotropes/vasopressors if SIRS
    • Parkland’s formula
  • Disability
    • R/o associated TBI
    • Prevent secondary brain injury
    • Normoglycemia
  • Exposure
    • Quantify severity of burns (depth, percent total body surface area)

Who should I admit and who can I send home?

  • Low voltage, asymptomatic- Do nothing and discharge
  • Low voltage, mild symptoms- Monitor and can discharge, if EKG and UA normal
  • High voltage (>1000V)- Admit for monitoring

REFERENCES:

Li, S. “Conference: Electrical injuries” Jacobi Medical Center. Jacobi/Montefiore Emergency Medicine Conference. Bronx. Nov 2015. Lecture

Chertoff, A. “Conference: Electrical injuries Jeopardy” Jacobi Medical Center. Jacobi/Montefiore Emergency Medicine Conference. Bronx. Nov 2015. Lecture

“Episode 1.0 – Electrical and Lightning Injuries.” Core EM

Nickson, Chris. “Electrical Injury.” Electrical Injury. LITFL Life in the Fast Lane Medical Blog