A Randomized, Controlled, Double-Blind Trial of 3 Local Anesthetics for Spinal Anesthesia in Primary Total Hip Arthroplasty to Compare the Percentage of Patients in Each Group With Early Ambulation

Total hip replacement is often performed under spinal anesthesia, which is the standard at Thomas Jefferson University Hospital (TJUH) and Rothman Orthopedic Specialty Hospital (ROSH) for patients without contraindications. Spinal anesthesia involves injecting a numbing medicine (local anesthetic) into the cerebrospinal fluid that bathes the spinal cord through a space between two bones in the back. This causes temporary numbness of the legs and hips and allows surgery to take place without patients feeling pain during surgery. Different local anesthetics can be used for spinal anesthesia and each works for a different duration of time. Another factor that affects how spinal anesthesia medications work is the baricity of the medication, which refers to how dense it is compared to cerebrospinal fluid (CSF). Medications that are less dense than CSF are hypobaric, those with same density are isobaric, and those with greater density are hyperbaric. For clinical purposes, this really only comes into play when positioning the patient immediately after spinal placement as patient position has different effects on the dermatomal level attained depending on baricity of the local anesthetic. Bupivacaine is a long-acting local anesthetic that has been used for several decades for total hip replacement. It is available in both hyperbaric form (with dextrose added) and isobaric form (with no dextrose added). Mepivacaine is another local anesthetic that has a shorter duration of action and is also used for spinal anesthesia in total hip replacement at many centers. All three drugs are used routinely at different centers in the United States. Despite the differences in duration that have been described from pharmacokinetic studies, a randomized, controlled study comparing the three drugs in terms of important outcomes, such as the ability to walk after surgery, has not been published yet. Therefore, the investigators want to compare the three local anesthetics in a randomized, controlled fashion to see if more patients are able to walk sooner after receiving mepivacaine spinal anesthesia than either form of bupivacaine spinal anesthesia.

Patients who are eligible will be called the night prior to surgery and the study will be explained over the phone. Patients who express interest will be recruited on the day of their scheduled surgery in the short-procedure unit. Patients will be given consent forms and time to read them and ask questions.

Preoperative Management All patients without contraindications or allergies will receive oral gabapentin and acetaminophen in the short procedure unit prior to surgery per routine practice.

Intraoperative Management The targeted spinal dermatome level to achieve will be T10 (umbilicus). For isobaric drugs, patients will sit after spinal placement for 3-5 minutes to achieve this level. For hyperbaric bupivacaine, patients will be immediately placed supine and in Trendelenberg position for 3-5 minutes to achieve adequate level and confirmed with sensory pinprick testing, which will be performed every 2 minutes beginning at spinal placement time. After spinal is placed, sedation will be titrated at the discretion of the anesthesia team to achieve the American Society of Anesthesiology's definition of moderate sedation (purposeful response to verbal or tactile stimulation, spontaneous ventilation, and no airway intervention needed) using propofol. All patients will receive tranexamic acid unless contraindicated (10 mg/kg bolus), as well as multimodal analgesia with a non-steroidal anti-inflammatory drug (NSAID) and dexamethasone 4 mg IV per routine practice.

Postoperative Management