A retrospective case-control study evaluating systemic blood pressure and heart rate in dogs with brain herniation under general anesthesia

Abstract

ObjectiveTo examine whether increased systemic arterial blood pressure (ABP) and decreased heart rate (HR) under inhalant anesthesia were suggestive of the Cushing reflex (CR) in dogs with neurological diseases based on magnetic resonance imaging (MRI) findings. Study designRetrospective case-control studyAnimals or Animal population: A sample of 137 client owned dogs admitted to two veterinary teaching hospitals for diagnosis and patient care due to suspected intracranial disease from 2005–2020. All dogs underwent general anesthesia for MRI of the brain. MethodsBased on MRI study reports, dogs were divided into three study groups: dogs with suspected brain herniation, dogs with an abnormal MRI finding but without suspicion of herniation, or dogs with structurally unremarkable brains (control). Initial evaluation by an anesthesiologist resulted in 58 cases selected for further review based on suspicion of having intracranial hypertension, as indicated by ABP and HR changes under anesthesia. Anesthetic records were randomized and independently reviewed by three board certified anesthesiologists blinded to MRI diagnosis who allocated each dog into one of three groups: (1) likely to have CR, (2) unlikely to have CR, or (3) insufficient data for determination. ResultsOf the 58 cases evaluated, 9 cases were considered likely to have CR and 48 were considered unlikely to have CR. In one case, the anesthesiologists were unable to determine whether CR occurred. Of the 9 dogs with likely CR, 3 had an MRI diagnosis of intracranial herniation. The remaining 6 dogs suspected of CR belonged to the normal brain group. Conclusions and Clinical RelevanceABP and HR changes associated with CR are not reliably associated with brain herniation in dogs undergoing general anesthesia.