Most people have heard the term "pneumonia" and know it is a serious lung infection. In fact, "pneumonia" is not a very specific term and essentially means inflammation in the deep lung tissues where oxygen is absorbed into the body and waste gases are removed. Pneumonia has potential to be life-threatening regardless of its cause and there can be many possible causes. Usually there is an infectious disease at the root (virus, bacteria, fungus, even a worm) but not necessarily. Pneumonia can be caused by aspiration (inhalation) of vomited or regurgitated food, inhalation of smoke or chemicals or it could even be immune-mediated with no infection at all (eosinophilic infiltration). Bronchitis is a separate condition from pneumonia, and represents inflamed airways of the lung rather than inflammation in the deep lung tissue itself but pneumonia and bronchitis commonly go together to created what is called "bronchopneumonia."
Pneumonia is commonly classified by its original cause:
In most cases of pneumonia there is a bacterial component. This means that no matter what started the pneumonia, bacteria have joined in adding their own special pus, fever, and potential for disaster; in most cases, management of the bacteria is vital. This article centers on the management of bacterial pneumonia.
WHEN TO SUSPECT PNEUMONIA
Profile view of the chest of an adolescent puppy who contracted pneumonia shortly after shelter adoption. Air-filled healthy lung is mostly black with a fine lacy overlay of lung tissue. The sections that appear whited out represent pus and fluid secretion within the lung. Notice the dark "tree branch" appearance over the white area of lung tissue. This is called an "air bronchogram" and represents air inside an airway highlighted by the fluid filled abnormal lung around it. Normally, the branching of an airway is not visible as it is adjacent to air-filled lung and blends in.
Radiograph on left is an aerial view or "VD" chest film showing the collapsed/consolidated lung when this dog first started treatment. Radiograph on right shows this has cleared substantially after a few days of treatment.
The diagnosis of pneumonia hinges on the chest radiograph but knowing when to take chest radiographs can be tricky. The veterinarian must put together findings from the history, physical examination, and possibly response to initial therapies to decide if radiographs should be checked.
Coughing is hallmark symptom, though certainly not all coughing pets (or even most coughing pets) have pneumonia and many pets (especially cats) with pneumonia hardly cough at all. Bacterial pneumonia does not just happen; it is virtually always caused by something else, so some kind of diagnostics will likely be needed to determine what led to the bacterial pneumonia if it is not readily apparent.
The pneumonia patient may be in one of three states:
The goal is to get the patient stable enough for home treatment as several weeks are needed to fully clear pneumonia. When the patient is eating well, he or she may be discharged with oral antibiotics, a regimen of physical therapy, and a schedule for re-check radiographs (usually weekly).
The hospitalized patient has the following needs:
Intravenous fluid therapy
Coughing may be annoying but it is therapeutic and, when it comes to pneumonia, we want to encourage it, not suppress it. Coughing brings up the pus, mucus, and inflammatory cell products that make our patient sick. If the secretions of the lung are allowed to dry up, the patient will never be able to cough them up. For this reason, IV fluids must be maintained to keep our patient hydrated and keep the respiratory secretions wet.
Antibiotics are given to kill the bacteria, but which antibiotics should be chosen? We need something that will penetrate into the pus and mucus (which many antibiotics cannot do). Often a “four quadrant” approach is used that covers bacteria classified as Gram negative and Gram positive as well as those classified as aerobic and anaerobic. This typically involves two antibiotics used in combination to synergize one another and covers almost every possible bacterial organism.
Alternatively, the lungs may be cultured via a procedure called a tracheal wash. This process involves light sedation which the patient must be stable enough to withstand. Sample fluid from deep in the lung can be retrieved for culture. A culture identifies the organism and provides a list of antibiotics that can kill it. If possible, it is best to obtain a culture as a surprising number of resistant bacteria are in the environment and we not only want to confirm our antibiotic choice is appropriate but we do not want to needless encourage further development of resistant bacteria.
If the patient is sick enough for hospitalization, antibiotics are typically given as injections so as to maximize absorption into the body.
A technique called coupage is helpful at mobilizing respiratory secretions. The therapist’s hand is cupped and gently but rapidly taps the patient’s chest wall repeatedly. This loosens some of the deeper secretions and helps them move into airways. Material in the airway generates coughing which removes these materials from the body. Coupage should be performed at least four times daily and should be continued at home as long as the patient has a cough.
Light exercise is also helpful in mobilizing the respiratory secretions. The patient should not be over-exerted as he/she does not have normal lung capacity but one can use one’s judgment as to what level of exercise is tolerated by the patient.
In most cases, oxygen therapy is not necessary but when a pneumonia patient simply cannot move enough air, there is no substitute for oxygen. Room air is 20% oxygen. An oxygen cage typically is set to deliver 40% oxygen (higher percentages over long term are actually toxic to lung cells), and special oxygen-delivery hoods are also popular. A patient who requires this level of support is extremely sick.
Once the patient has a good appetite, he or she may be discharged for home care. The following tips are recommended as long as the patient is coughing:
Pneumonia is a serious infection and several weeks are needed to clear it. Prognosis ultimately depends on what the underlying cause was but the good news is that most patients are not sick enough to require oxygen therapy and the majority of these ultimately recover with proper treatment.
Page last updated: 2/16/2018