By Raphaël Vézina-Audette, M.Sc.,DVM, DACVAA, CVA
Anesthetic complications in veterinary patients are an important source of concern and anxiety in pet owners. Will my pet survive this anesthetic event? Rather than discarding these concerns when discussing veterinary anesthesia with the public, we as veterinarians and veterinary technicians best serve our clients when we educate them on the risks of anesthesia and describe the steps we take to mitigate those risks.
What is the incidence of anesthetic mortality in veterinary patients?
Few studies have documented the incidence of anesthetic morbidity and mortality in veterinary medicine. The largest veterinary study reporting on anesthetic mortality, entitled Confidential Enquiry into Perioperative Small Animal Fatalities was carried out in the UK between 2002 and 2004 and involved 98,036 anesthetics and sedations from 117 participating centers established an overall rate of 0.18% for anesthetic-related deaths in dogs. Twenty years later, the first international multicenter study by Redondo and colleagues assessed the overall mortality of veterinary patients to 0.69%. Strikingly, despite two decades of technological advances, little has changed in terms of anesthetic mortality rates. When compared to the reported human perioperative mortality rates (1.1 / 1000000), anesthetic deaths are significantly more frequent in veterinary medicine.
What could increase the risk of anesthetic death in my pet?
Research has shown that certain patient specific factors can increase anesthetic risks for morbidity and mortality. While the adage “Age is not a disease” remains true, geriatric patients often present with health issues that could complicate anesthesia. Not only was advanced age identified as a risk factor for anesthetic death in veterinary patients, neonatal and pediatric patients also were at an increased risks due to the immaturity of organ systems. Ultimately, a healthy patient who presents for an elective procedure carries a lower risk than a sick patient in urgent need for surgery. The general threat to any patient undergoing general anesthesia lies within his health status at the time of the anesthetic event and thus, a careful assessment of organ systems function is indispensable to accurately estimate a patient’s anesthetic risk. Unsurprisingly, obesity has also been linked to anesthetic death and is arguably the most easily preventable cause of anesthetic mortality in pets. Client education during wellness visits and emphasizing the importance of weight management cannot be understated.
What does my veterinary healthcare team do to mitigate these risks?
Though we cannot completely eliminate anesthetic risks for veterinary patients, efforts can be made to accurately identify patients with important risk factors. The first step is to perform a physical exam within 12 hrs. of any anesthetic event. Following administration of sedative and anesthetic medications, our patient’s survival depends on the diligent monitoring of vital parameters which must continue until the patient is fully recovered from anesthesia. Recent evidence suggests that the majority of anesthetic deaths (80%) occur in the post-operative period. This bolsters the recommendation to provide continued anesthesia monitoring and support of vital functions including, but not limited to, body temperature and respiratory function during the recovery phase. A dedicated anesthesia staff member and limiting distractions in the work environment are key to success. Ensuring that every member of the team is knowledgeable and trained in accordance with the most up-to-date guidelines through continuing education is critical. Depending on the state in which you work, legislation may also prohibit workers who are not licensed veterinary technicians or veterinarians to take on the role of anesthetist.
As far as anesthetic protocols are concerned, veterinary anesthesiologists recommend using a multimodal, balanced anesthetic regimen that incorporates, wherever possible, multimodal analgesia including regional nerve blocks, opioids, and NSAIDs. Indeed, pre-emptive pain management and continual assessments of patient comfort are key for optimal outcomes. The use of acepromazine and alpha-2 agonists as premedicants has also been associated with improved outcomes due to their ability to decrease inhalant anesthetic doses during anesthesia and reduce stress associated with anesthesia and surgery.
In summary, the risks of anesthetic mortality in veterinary patients is real, and owner education should be promoted by veterinary practice managers and administrators rather than a cavalier approach aiming to minimize these concerns. Anesthetic mortality increases with patient age and health status. Diligent patient monitoring from induction of anesthesia carried through the recovery stages are essential to identify life-threatening complications. Rigorous pain management protocol guided by serial pain assessments also plays an important role to optimize
outcomes.
Dr. Vezina-Audette is a board-certified veterinary anesthesiologist and second-year surgical resident at PVESC.
