Intravenous Ondansetron for Attenuation of Post Spinal Anesthesia Hypotension

Abstract

pinal Anesthesia is a common type of anesthesia used during many surgical procedures. This regional technique can be accomplished by administering an intrathecal dose of hyperbaric local anesthetic solution. The local anesthetic within the subarachnoid space can block sensory, motor and sympathetic pathways. One of the most common complications associated with spinal anesthesia is hypotension with or without bradycardia that can increase risk of perioperative cerebral and cardiovascular events. The postulated mechanism for hypotension has been attributed to both venous and arterial vasodilatation resulting from a local anesthetic induced sympathetic blockade, while bradycardia is believed to result from an increase in parasympathetic tone, blockade of the cardioaccelerator nerve fibers, and decreased baroreceptor activity. Recently, the Bezold Jarisch reflex (BJR) has been implicated as the most likely cause of bradycardia following spinal anesthesia. The Bezold–Jarisch reflex is a cardioinhibitory reflex producing bradycardia, hypotension, and cardiovascular collapse via non-myelinated, type C fibers whose terminals lie in the chambers ofthe heart. Stimulation of peripheral serotonin receptors 5-hydroxytryptamine (5-HT3) elicits the BJR.