Post-Operative Analgesia and Spinal Block Duration Following Total Hip Arthroplasties: Comparison of Single-Shot Intrathecal Ropivacaine and Bupivacaine in a Randomized Double-Blinded Controlled Study

Patients undergoing outpatient total hip arthroplasty (THA) under spinal anesthesia require an anesthetic technique that provides adequate surgical anesthesia while allowing rapid postoperative recovery and same-day discharge. Bupivacaine is currently the most commonly used spinal anesthetic for hip arthroplasty, but its relatively long duration of action may delay recovery of motor and sensory function, prolong post-anesthesia care unit (PACU) stay, and increase the risk of urinary retention. Ropivacaine is a long-acting amide-type local anesthetic with a shorter duration of action and a potentially more favorable safety profile, including lower cardiotoxicity and reduced hemodynamic effects. This study aims to determine whether isobaric ropivacaine is more suitable than isobaric bupivacaine for spinal anesthesia in outpatient THA and to identify the optimal dose of ropivacaine for this surgical setting.

Altogether 176 patients scheduled for elective outpatient unilateral total hip arthroplasty at TYKS ORTO Surgical Hospital will be enrolled in this prospective, randomized, double-blind, controlled phase IV clinical trial. Eligible participants will be between 18 and 80 years of age, with a height of 160-186 cm, ASA physical status I-II, and body mass index below 35 kg/m², in accordance with local outpatient surgery criteria. Written informed consent will be obtained from all participants prior to study inclusion.

Patients will be randomized into two study groups to receive either intrathecal isobaric ropivacaine or intrathecal isobaric bupivacaine for spinal anesthesia. Both participants and investigators will remain blinded to group allocation throughout the study period. Spinal anesthesia will be performed according to standard clinical practice. Patient monitoring and perioperative care will follow institutional protocols routinely used for outpatient joint replacement surgery.

Baseline measurements including heart rate, blood pressure, and oxygen saturation will be recorded before administration of spinal anesthesia. After intrathecal injection, patients will undergo continuous monitoring including blood pressure, pulse, electrocardiography (ECG), oxygen saturation, and assessment of sensory block height. Measurements will initially be recorded every five minutes during the intraoperative period and subsequently at longer intervals after transfer to the ward.

The primary outcome of the study is the time to full recovery of sensory and motor function following spinal anesthesia. Secondary outcome measures include the proportion of patients discharged home as planned on the day of surgery, duration of PACU stay and total hospital stay, postoperative pain intensity measured using the Numerical Rating Scale (NRS; minimum 0, maximum 10, higher scores indicating more severe pain), incidence of urinary retention, time required to achieve adequate surgical anesthesia, adequacy of anesthesia during surgery, incidence of postoperative nausea and vomiting (PONV), postoperative opioid consumption, and patient satisfaction with care and recovery.