Answers and Discussion

Answers and Discussions to the Questions:

• In a fire, what types of by-products and respiratory injuries do you need to worry about?
  
  Carbon monoxide and carbon dioxide drop the concentration of oxygen to 5-10%.  Carbon monoxide preferentially binds with hemoglobin in place of oxygen.  This leads to tissue hypoxemia and ultimately asphyxiation.  The two types of injuries that occur are either thermal or chemical.  Thermal injury is usually limited to the upper airway and may result in edema, erythema, hemorrhage and ulceration.  Chemical injury (carbon monoxide, hydrogen cyanide) results in tissue hypoxemia, inhibition of mucociliary clearance, surfactant inactivation, and changes in vascular permeability leading to pulmonary edema.

• What are the clinical signs of smoke inhalation?
  
  The patient may be normal on presentation.  If it is unknown as to whether the animal was in a fire, look for soot on the fur and the smell of smoke.  You may see burns or singed hair and whiskers.  The animal may have or may develop a cough, dyspnea, or upper airway stridor.  You may see cherry red or brick red mucous membranes.   There may also be conjunctival or corneal edema.
  
• What is the progression of signs/symptoms you see with respiratory damage over the next 2-3 days?
  
  During the first 6-12 hours the patient may be normal or have mild signs:  edema, stridor, etc.  This is when there is tissue hypoxia and pulmonary defenses are shutting down.  Over the next 6 hours to 2 days, pulmonary edema may develop and in severe cases, acute respiratory distress syndrome (ARDS).  Two to three days after the injury pneumonia may develop as well as sepsis if severe burns were present.

• Should chest radiographs be done on all patients with smoke inhalation?
  
  No.  As discussed in the previous question, most respiratory damage is not apparent on a radiograph for many hours to days.  Radiographs are generally not indicated in asymptomatic patients and only used for a baseline in symptomatic patients.  
  
• How would you treat a smoke inhalation patient?
  
  First assess the airway.  If the patient is in respiratory distress because of laryngeal edema, intubation or a tracheostomy may be necessary.  Follow with positive pressure ventilation (PEEP--to help combat atelectasis) and humidify all gases.   If the patient is not in severe respiratory distress, place in an oxygen cage at 100%, even if asymptomatic.  This will reduce carboxyhemoglobin concentrations by 50% every 30 minutes.  Wean over the next few hours to a lower oxygen concentration (40%) to avoid oxygen toxicity.  Crystalloid fluids (Normosol) should be given at a rate needed to restore/maintain adequate perfusion in the body.  Overhydration can contribute to pulmonary complications but underhydration is known to increase cardiopulmonary instability.  Give colloids if hypoproteinemia is present, especially if the patient is severely burned.  Steroids are not indicated and may actually make things worse.  Antibiotics should not be given prophylactically.  Pneumonia usually develops 2-3 days after presentation.  Culture and sensitivity should be obtained at that time, then start broad-spectrum antibiotics and switch to a more narrow-spectrum drug after sensitivity results are received.  If pulmonary edema develops in these cases, diuretics are not indicated and may lead to electrolyte imbalances.  Ventilation is a better option.  Also encourage the patient to move frequently--switch positions, walk if able, etc.  Nebulization and coupage can be done QID.
  
• What complications do you need to watch for?
  
  Watch for pneumonia, ARDS (acute respiratory distress syndrome) and sepsis.  Pay attention to lung sounds and vital signs, central venous pressure, CBC's and radiographs.  

• Follow-Up: "Annie" was placed in an oxygen cage but her lung sounds became a little more harsh over the next few hours.  She stayed in the critical care unit for a couple days and was nebulized and coupaged.  She did well, did not develop any complications and was sent home.

Smoke Inhalation Pearls

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Copyright 2000, Wayne E. Wingfield, Colorado State University   
This page was last edited:  04/12/00