Inhalation Injuries

Apologies regarding the delay in bringing you this post... Hope you've missed us! Today we address inhalation injuries in the Emergency Room setting.

Inhalation injury is a nonspecific term that refers to damage to the respiratory tract or lung tissue from heat, smoke, or chemical irritants carried into the airway during inspiration. Respiratory damage is related to the concentration of the gas and its solubility. More water-soluble gases (e.g., chlorine, ammonia, sulfur dioxide, hydrogen chloride) dissolve in the upper airway and immediately cause mucous membrane irritation, which may alert people to the need to escape the exposure. Permanent damage to the upper respiratory tract, distal airways, and lung parenchyma occurs only if escape from the gas source is impeded. Less soluble gases (e.g., nitrogen dioxide, phosgene, ozone) may not dissolve until they are well into the respiratory tract, often reaching the lower airways. These agents are less likely to cause early warning signs (phosgene in low concentrations has a pleasant odor), are more likely to cause severe bronchiolitis, and often have a lag of ≥ 12 h before symptoms of pulmonary edema develop.

Symptoms and signs:

·      Dyspnea

·      Hoarseness, stridor

·      Marked cough, hemoptysis

·      Decreased level of consciousness, confusion

·      Cherry red skin (unreliable, usually a post-mortem finding)

·      Singed nasal hairs, soot on oral/nasal membranes, sooty sputum

·      PO2 normal but O2 saturation low suggests carbon-monoxide poisoning

Investigations:

·      Co-oximetry (Carboxyhemaglobin levels)

·      ABG

·      CXR

·      Bronchoscopy

Possible causes:

·      Direct thermal injury to upper airways

·      Smoke inhalation, leading to bronchospasm and edema

·      Carbon-monoxide or cyanide poisoning

Management:

·      Secure airway (early intubation in direct thermal injuries)

·      Humidified oxygen

·      Bronchodilators

·      Pulmonary toilet (removal of secretions)

·      Hyperbaric oxygen chamber or 100% O2 in carbon-monoxide poisoning

The most serious immediate complication is acute respiratory distress syndrome (ARDS), which usually occurs within 24 h. Patients with significant lower airway involvement may develop bacterial infection. Ten to 14 days after acute exposure to some agents (e.g., ammonia, nitrogen oxides, sulfur dioxide, mercury), some patients develop bronchiolitis obliterans progressing to ARDS. Bronchiolitis obliterans with organized pneumonia can ensue when granulation tissue accumulates in the terminal airways and alveolar ducts during the body’s reparative process. A minority of these patients develops late pulmonary fibrosis.

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Hypothermia and Frostbite

ER series 4 – Hypothermia and frostbite

32~34.9°C	Mild	Tachypnea, tachycardia, ataxia, dysarthria, shivering
28~31.9°C	Moderate	Loss of shivering, dysrhythmia, muscle rigidity, dilated pupils, decrease level of consciousness, combative behavior, J waves on ECG
<28°C	Severe	Coma, hypotension, academia, ventricular fibrillation, asystole, flaccidity, apnea

J-waves are also known as Osborn waves. Picture from Wikipedia.

Investigations:

·      Bloods: ABG, CBC, electrolytes, serum glucose, creatinine/BUN, magnesium, calcium, amylase, coagulation profile

·      Imaging: CXR

·      Monitoring: ECG, rectal thermometer, urinary catheter, nasogastric tube

Predisposition factors include extreme age, drug overdose, alcohol ingestion, incapacitating trauma, cold water immersion, outdoor sports; investigations and treatment should kept with these factors in mind. Complications include ventricular fibrillation, asystole, volume and electrolyte depletion.

Treatment is based on rewarming and supporting cardiorespiratory function:

·      Do not do CPR if there is a pulse, even if a bradycardic one. Always take the pulse and rhythm over a full minutes.

·      If there is need for intubation, ventilate with warmed, humidified oxygen.

·      If in ventricular fibrillation and body temp <30°C, defibrillate up to maximum 3 times.

·      Gently replace fluids and electrolytes

·      Passive external rewarming—using insulating blankets and letting the body warm itself back up; suitable for patients with body temperature >32.2°C

·      Active external rewarming—using warming blanket; safer to use in conjunction with active core rewarming

·      Active core rewarming—using warmed humidified oxygen and IV fluids OR peritoneal dialysis with warmed fluids OR gastric/colonic/pleural irrigation with warm fluids. Suitable for patients with body temperature <32.2°C or those with cardiovascular instability

·      Beware of the afterdrop phenomenon—warming of extremities causes vasodilation and movement of cool pooled blood from extremities to core, resulting in a drop in core temperature and can lead to cardiac arrest.

When exposed to extreme elements, patients may not only present with hypothermia but also frost bite!

Frostbite—when ice crystals form between cells and as a result the cells die. Its symptoms and signs are much like that of burns, and the classification is also similarly based on the depth of injury.

Degree	Symptoms	Signs
1st	Initial paresthesia, pruritus	Erythema, edema, hyperemia, no blisters
2nd	Numbness	Clear blisters, erythema, edema
3rd	Pain, burning, throbbing, thawing (If too severe there can be lack of pain)	Hemorrhagic blisters, skin necrosis, edema, no movement

Management:

·      Treat underlying hypothermia as above

·      Remove wet and constrictive clothing

·      Immerse in agitated warm water 40~42°C for 10~30min. This can be very painful so administer adequate analgesia.

·      Clean injured area and leave open

·      Debride dead tissue if necessary

·      Tetanus and penicillin G as infection risk is high

·      Surgical consult if there are any eschars

·      Never allow thawed area to re-chill or freeze

This blog post is also available in podcast form! Search for us on iTunes and Googleplay or visit www.medonthego.podbean.com.