Principal Investigator: Jordyn Boesch

DESCRIPTION (provided by applicant): 

‘Walking’ epidural injection with low doses of opioid and local anesthetic is used in women and dogs undergoing reproductive tract surgery to provide better analgesia than systemic drugs alone. A safe, effective “walking” epidural technique that can be employed easily by primary care veterinarians would greatly improve the post-operative recovery of many thousands of cats undergoing ovariohysterectomy (OVH) each year. We propose to develop such a technique: ‘walking’ sacrococcygeal epidural anesthesia (SCEA). First, we will determine the volume of injectate administered at the sacrococcygeal (SC) space that distributes cranially to spinal cord segment T10, the site where afferent neurons from the ovaries first enter the CNS. We will accomplish this by injecting contrast incrementally at the SC space and imaging the vertebral column using computed tomography in normal research cats under anesthesia. Next, using the volume determined above, we will assess if ‘walking’ SCEA administered post-operatively results in enhanced recovery after OVH compared to conventional systemic analgesia alone (i.e., lower pain scores, less nausea, better appetite, and improved mentation). We will also assess the extent to which the magnitude and duration of analgesia is dependent upon local anesthetic concentration, and if pelvic limb neurological dysfunction (proprioceptive or motor deficits) and/or urine retention occur. Shelter cats undergoing OVH in Block V Surgical Exercises will be assigned to one of four groups: a control group (systemic analgesia, no SCEA) or three groups given systemic analgesia plus SCEA; the latter will test three concentrations of the local anesthetic ropivacaine (0%, 0.06%, 0.125%) combined with a fixed dose of epidural morphine (0.1 mg/kg). A blinded investigator will assess analgesia using a validated pain scale at 0,1, 2, 4, 6, 8, 12, and 20 hours after the end of anesthesia. Rescue analgesia (systemic morphine) will be provided to any cat that achieves a predetermined analgesic intervention score. Nausea, appetite, mentation, pelvic limb proprioception and motor function, and urination/bladder size will also be assessed at these times. A linear mixed effect model will be constructed to assess the effect of time, group, and their interaction on pain score. A survival analysis will be performed to determine if the times to rescue analgesia, as well as times to first food consumption, normal mentation, normal pelvic limb neurological function, and urination differ by group. We hypothesize the walking SCEA will result in enhanced recovery, that increasing local anesthetic concentration is associated with greater magnitude and longer duration of analgesia, and that neurological deficits and urine retention will not occur after SCEA.