Kate Bailey

Approximately 4 million dogs in the United States suffer from brain cancer each year, and even more from intracranial disease and injury. Appropriate diagnostic imaging, including MRI, is crucial to diagnosis and treatment. Whether performing diagnostics or treatments, general anesthesia is required. Choice of safe anesthetic drugs is paramount to the survival and wellbeing of these patients to avoid complications such as increasing intracranial pressure and hypotension. The intracranial compartment is non-elastic, therefore an increase in tissue (i.e. a tumor), blood or cerebrospinal fluid volume inside the skull would increase intracranial pressure and could result in death of the patient. The ideal general anesthetic agent should decrease the amount of nutrients required by the brain and decrease the amount of cerebral blood flow (CBF), consequently decreasing the pressure inside the skull, while also ensuring hemodynamic stability and a quick recovery. CBF and cerebral vascular reactivity (CVR) to carbon dioxide are important indicators of brain vascular health and, if not impaired by the anesthetic drug, an invaluable tool for surgical planning. Inhalant anesthetics, such as isoflurane and sevoflurane, increase CBF and impair CVR, potentially leading to an increase in intracranial pressure in addition to systemic hypotension. Propofol is an injectable drug which decreases the metabolic rate and blood flow in the brain in a parallel fashion, reduces intracranial pressure, and maintains CVR to CO2. As such, using propofol to induce and maintain anesthesia appears the best choice for these patients. Alfaxalone is a new injectable anesthetic with the same mechanism of action as propofol that was recently introduced to the veterinary market. Compared to propofol, alfaxalone has an excellent safety margin and less cardiovascular side effects. This could be a more ideal anesthetic option for patients with intracranial disease, however, there is no information about the effects of alfaxalone on CBF and CVR.

Both captive and free������������������ranging sea turtles are frequently anesthetized for diagnostic, therapeutic, and research purposes. While general anesthesia with inhalant anesthetics is a common means of restraint in these species,reports of prolonged recovery times following inhalant anesthesia abound (Chittick, 2002; Moon, 1996; Sladky,2012; Vigani, 2014). Delayed time to full anesthetic recovery can result in increased morbidity and mortality during the peri������������������anesthetic period as well as increased personnel time and labor costs. Identifying methods to shorten the duration of inhalant anesthetic recovery would be advantageous for both sea turtles and their human caretakers. While presumably multifactorial, delayed anesthetic recovery time in sea turtles is likely influenced by the unique chelonian cardiopulmonary anatomy and physiology and response to changing oxygen levels. To this end, previous reports have hypothesized that exposure to high concentrations of oxygen (eg, 100% oxygen)will prolong reptilian anesthetic recovery, however, results of prospective studies are mixed and none have used a chelonian model (Bertelsen, 2005; Diethelm, 1999; O, 2015). Inhalant anesthetic characteristics may also affect recovery time and, in mammals, the use of a more poorly soluble inhalant anesthetic (eg, desflurane) will hasten emergence from inhalant anesthesia (Steffey, 2015); however, the effects of desflurane use in sea turtles is currently unknown. As the use of a poorly soluble inhalant anesthetic and lower concentrations of oxygen, either alone or in combination, may be advantageous in the anesthesia of sea turtles, the objective of this study is to investigate physiologic effects and anesthetic recovery time following use of desflurane or isoflurane in either 21% oxygen or 100% oxygen in green sea turtles. We hypothesize that sea turtles receiving desflurane in 21% oxygen will have significantly faster times to anesthetic recovery without significant negative physiologic effects.