By Ashley Power, VMD
House fires are tragedies for household pets as much as their human family members. In addition to the risk of burn or physical injury from the fire itself, smoke inhalation can have immediate and long-term consequences for our pets.
Carbon monoxide is the chief culprit when it comes to smoke inhalation. This molecule is a competitive inhibitor of oxygen in binding hemoglobin, the iron-based molecule within red blood cells responsible for carrying oxygen. When air is inhaled into the lungs, it makes its way through progressively smaller branches of bronchi and bronchioles until it reaches a terminal site of an alveolus, where the epithelial lining of the airway meets the endothelial lining of a capillary for gas exchange. From here, oxygen is carried by red blood cells to the tissues of the body with the ultimate purpose of carrying out aerobic metabolism.
Carbon monoxide is able to bind hemoglobin at a much higher affinity than oxygen, so only a small amount can have profound consequences. When carbon monoxide is inhaled in excess, such as during a house fire, it out-competes oxygen to bind to hemoglobin, and as a result, the body’s tissues do not receive sufficient oxygen to properly carry out their functions. This condition is called hypoxia. The nervous tissue in the brain has some of the body’s highest demand for oxygen, and so we often see neurologic damage as a result of a hypoxic state. Ultimately, the three broad possible results of carbon monoxide poisoning are complete recovery, recovery with permanent neurologic damage (particularly, hearing or vision loss), and, sadly, death.
A feline patient in an oxygen cage. Photo courtesy of Google.
Quick intervention is key in giving animals exposed to smoke their best chance at recovery. Upon arrival to the hospital, the animals’ signs can range in severity from eupnea (normal breathing) to tachypnea (quick breathing) to dyspnea (distressed or labored breathing). The veterinarian will perform a physical examination and obtain the patient’s vital parameters, percent oxygen saturation, and blood gas analysis. We can place a probe on the animal’s tongue to measure the percent of oxygen saturation in the circulating red blood cells, and can obtain a blood sample which a machine analyzes to determine what percent of carbon monoxide is bound to hemoglobin.
Animals with trouble breathing or indications of poor oxygenation status on their diagnostics are placed in an oxygen cage, which is able to deliver oxygen at about twice the concentration of normal atmospheric air. The higher concentration of oxygen is able to shorten the half-life of carbon monoxide, meaning that we can rid the body of this toxic gas much quicker with the aid of oxygen supplementation. Studies have reported that the normal half-life of 250 minutes can be reduced to 26-148 minutes. Once the carbon monoxide is cleared, the animals may require a longer period of oxygen therapy if their lungs are recovering from thermal injury or irritation from the inhalation of other noxious gases or particulate matter from the fire.
Once the animal’s breathing is more stable, they are gradually weaned off of oxygen back down to normal room air. They are also bathed to remove lingering smoke residue from the fur. Periodic neurologic assessment is performed during their stay in the hospital. Sometimes, delayed neurologic signs can develop days after the initial insult. Animals who suffered burn injuries to their skin in addition to smoke inhalation will require additional care for the associated wounds, and will unfortunately have a more guarded prognosis for recovery.
Although the hardship and potential medical consequences of house fires are daunting, the MSPCA-Angell team is fortunate enough to offer a program called SafePet to provide owners with up to two weeks of emergency boarding for pets displaced by disasters such as house fires. It is important to be prepared for these unforeseen tragedies by having a disaster response plan in mind for your pets. Please refer to our MSPCA website for important disaster preparedness guidelines.
- Silverstein DC, Hopper K. Small Animal Critical Care Medicine. 2nd Ed. St. Louis, MO: Saunders; 2015. 785-788.