The effects of stress on health outcomes in veterinary practice
While veterinarians have traditionally been taught to prioritize patients’ medical care over their stress levels in the hospital, the veterinary community is coming to recognize that stress has its own effects on health outcomes. My colleagues and I have conducted research in this area to provide evidence for what many of us know intuitively—and are increasingly coming to prioritize.
In some patients stress, levels may be quite high. In our work on stress behaviors in dogs we found that cortisol levels of healthy dogs on their first night in a veterinary hospital were two to four times higher than that of thunderstorm-phobic dogs at home with their owners during a storm. Although the stress response is an appropriate attempt by the body to maintain homeostasis after a challenge, the response can become damaging when activated inappropriately or chronically, as in hospitalization. Evidence suggests that:
> chronic stress can negatively affect health outcomes in a multitude
> stress can be a significant factor contributing to disease
> reduction of stress may play an important role in the return to health.
The immediate effects of stress on the complete blood count are well-known in veterinary medicine as the “stress leukogram,” which includes leukocytosis, neutrophilia, lymphopenia and related changes. As stress is prolonged and becomes chronic, leukocytosis may become leukopenia, with other changes to inflammatory cytokines resulting in immunosuppression. This stress-induced immunosuppression has been shown in humans to result in increased susceptibility to infection and neoplasia, while laboratory studies in mice have also shown decreased ability to eliminate bacterial infection due to chronic stress, suggesting that that stress increases susceptibility to sepsis. We don't know the effects of stress-induced immunosuppression on hospitalized veterinary patients, but we have no reason to think they are any less significant than in other species.
Studies in laboratory animals and humans also show that stress delays wound healing, certainly a concern for our postoperative surgical or trauma patients. Chronic stress has been shown to negatively affect the gastrointestinal system, exacerbating large-bowel disease in humans and being associated with chronic idiopathic large-bowel disease in dogs. As for its effects on the cardiovascular system, chronic stress is prothrombotic, associated with hypertension, and has triggered atrial fibrillation in humans.
Stress in veterinary patients is very difficult to quantify. Unfortunately, there are no validated cage-side measurements for stress assessment by clinicians, and behavioral measures are notoriously difficult to interpret. Our recent work investigating stress behaviors in hospitalized dogs suggests that many behaviors frequently used by clinicians to identify stress, such as barking, do not correlate with elevated cortisol levels. While two behaviors did correlate with high cortisol levels (panting) or low cortisol levels (resting the head on the ground), 20 minutes of observation was necessary for these behaviors to be predictive; two minutes of observation was insufficient. These findings suggest that assessment of a patient's stress levels by veterinary personnel may be inaccurate simply because of inadequate time for thorough observation of the patient.
So what avoidable stressors are our patients encountering in our hospitals? We restrain them, expose them to possible hostile conspecifics in neighboring cages, separate them from their owners and provide a noisy and high-motion environment for them. Not all of these stressors can be removed from the hospital experience, but arguably many can be reduced. Hospital administration could more greatly prioritize staff training in low-stress handling skills, support a clinician or technician’s choice to go slowly with some animals—despite a loss of efficiency—and place an emphasis on hospital design to improve the animal's experience, including noise reduction measures. Owners can be encouraged to visit their hospitalized pets, and shy animals can be provided with a safe place to hide that still allows for clinician observation, such as a high-walled bed. Other solutions are available at dvm360’s Fear Free center (dvm360.com/fearfree).
With the knowledge of the damaging effects of stress on health outcomes, and in the absence of an ability to accurately predict which animals are stressed and which are not, we call on the veterinary community to prioritize stress prevention in hospitals. Our patients’ bodies are not our only responsibility—their minds are as well, especially as body and mind are so inextricably entwined.
Hekman JP, Karas A, and Sharp CR. Psychogenic stress in hospitalized dogs: Cross species comparisons, implications for health care, and the challenges of evaluation. Animals 2014;4.2:331-347. Open access version available at dx.doi.org/10.3390/ani4020331.
Hekman JP, Karas AZ, and Dreschel NA. Salivary cortisol concentrations and behavior in a population of healthy dogs hospitalized for elective procedures. Applied Animal Behaviour Science 2012;141:3-4. Open access version available at www.ncbi.nlm.nih.gov/pmc/articles/PMC3817620/.