SMALL ANIMAL MEDICINE
to be fed and often have naso-oesophageal tubes
placed, but due to the ileus and gastric stasis, the food
accumulates in the stomach and increases their risk of
vomiting and aspirating.
This risk can be reduced by doing intermittent gastric
suction of the stomach content, by either passing a
stomach tube intermittently or by placing a nasogastric
feeding tube and suctioning out the residual gastric
content before feeding. The nasogastric tube can also
then be used for enteral feeding. Placing nasogastric
tubes as apposed to naso-oesophageal tubes was
thought to increase the risk of regurgitation, but a
study published in the journal of Veterinary Emergency
and Critical Care found that there was no significant
differences in adverse occurrences between the
groups with naso-oesophageal tubes and those with
nasogastric tubes. In people, reinfusing some of the
aspirated gastric fluid has been recommended to
avoid the development of hyperchloremic metabolic
acidosis, however In a small population of dogs
and cats that underwent intermittent suction over
a 36 hour period none developed hyperchloremic
metabolic acidosis.
AP is a well known sequel to general anaesthesia (GA)
in dogs. The longer the time under GA, and the more
times a patients position is changed are some of the
factors that lead to an increase risk for that patient
aspirating. Trying to reduce the time under GA along
with good presurgical planning could help with these
factors.
Prolonged food restriction before GA has also been
thought to aid in reducing the risk of AP but this has
been brought into question by four different studies
in dogs where the impact of food withholding
on gastroesophageal reflux was reported. The
conclusion was that a short (2 to 4 hour) period of
food withholding as well as feeding a smaller portion
of food with high moisture content (canned dog
food) appeared to reduce the risk of gastroesophageal
reflux. The optimal duration of withholding water was
also evaluated, and determined to be four hours.
Treatment
Treatment for aspiration pneumonia revolves around
treating the underlying cause if possible, administration
of intravenous fluids, antibiotics and oxygen therapy
along with other supportive care.
tract diseases. The group recommends the use
of ampicillin or a first generation cephalosporin in
patients with aspiration pneumonia and no evidence
of sepsis. They also suggest clindamycin could be
used for gram-positive and anaerobic coverage, as its
lipophilic nature may afford better tissue penetration.
When there is evidence of a more life-threatening
infection then the recommendations are to add
a fluroquinolone and if the animal has a history of
being from a shelter or boarding facility and presents
with a very mild pneumonia with no systemic signs,
mycoplasma could be the underlying infectious agent
and doxycycline may be used.
When the following factors are present, then obtaining
a sample for culture and sensitivity is strongly advised
as they are likely to be associated with resistant
bacteria:
1. The patient has been on antibiotics within the last
four months
2. The aspiration pneumonia is a hospital acquired
infection
3. The patient has recurrent bouts of AP
The duration of treatment of dogs with AP has also
been questioned as the traditional recommendations
have been to continue administration of antimicrobials
for at least 3-4 weeks, or 1-2 weeks after radiographic
resolution. There appears to be no evidence however
to support this duration of treatment in either cats or
dogs. In the human literature the recommendations
are to use antimicrobial therapy for 7 to 10 days
and only extend the therapy for 14 days or longer
for patients who are immunocompromised or those
with unusual infections They also do not advise using
the appearance of thoracic radiographs to guide the
duration of antibiotic therapy.
Specifically, the guidelines recommend “treatment
until 72 hours after the patient becomes afebrile and
until clinically stable. With this in mind the consensus
opinion of the Working Group is that shorter courses
of appropriate treatment, might be effective in some
veterinary situations as well. They recommend that
patients be re-evaluated no later than 10–14 days
after starting treatment, and then the decisions to
extend treatment should be made based on clinical,
haematological, and radiographic findings. The use of
CRP may be helpful in decision making at this stage
as well.
Fluid Therapy
Antimicrobial Treatment
Ideally, antimicrobial selection should be based
on the results of the culture and sensitivity, but
it is not always possible to get samples due to
financial limitations or patient instability. In these
cases broad-spectrum empirical antibiotics should
be chosen using the recommendations made by
the International Society for Companion Animal
Infectious Disease Working Group on respiratory
Fluids are important to replace fluid losses and
maintain hydration. Dehydration causes the respiratory
secretions to become more “sticky” due to loss of
fluids from the aqueous layer of these secretions.
This in turn impairs mucociliary clearance. On the
other hand, over hydration can be detrimental to the
patient, as it will increase pulmonary interstitial and
alveolar fluid accumulation and thereby exacerbate
hypoxemia. There are no guidelines as to the use of
Issue 05 | NOVEMBER 2018 | 19