This study aims to investigate whether heart rate variability (HRV), a marker of autonomic nervous system activity, can predict the occurrence of rebound pain after total knee arthroplasty (TKA). Rebound pain is defined as a sudden and intense pain episode (NRS ≥7) that typically arises after the resolution of peripheral nerve blocks used for postoperative analgesia.
Patients undergoing elective unilateral TKA under spinal anesthesia with peripheral nerve blocks will be included. HRV will be measured both before and after surgery using a chest-worn heart rate monitor. Pain levels, analgesic consumption, sleep quality, and patient satisfaction will also be recorded. The primary goal is to determine whether perioperative HRV values can serve as a predictive biomarker for rebound pain.
Secondary outcomes include the relationship between HRV and pain intensity, opioid use, sleep quality, and length of hospital stay. The findings may contribute to developing individualized pain management strategies for TKA patients.
Who can participate
Age range
18 Years – 70 Years
Sex
ALL
See this in plain English?
AI-rewrites the medical criteria so a patient or caregiver can understand them. Always confirm with the trial site.
Inclusion Criteria:
* Age between 18 and 70 years
* American Society of Anesthesiologists (ASA) physical status I-III
* Scheduled for elective, unilateral total knee arthroplasty under spinal anesthesia
* Planned use of multimodal analgesia including peripheral nerve blocks
* Ability to provide written informed consent
* Ability to understand and complete pain diaries and questionnaires
Exclusion Criteria:
* Known allergy to local anesthetics
* Contraindications to regional anesthesia
* Contraindications to spinal anesthesia
* ASA physical status IV or higher
* Pregnancy or breastfeeding
* Neurological or psychiatric disorders impairing ability to participate or report outcomes
* Use of anticoagulant therapy or presence of coagulation disorders
* Infection at the proposed injection site
* Emergency (non-elective) surgical procedures
Questions worth asking your doctor
Bring these to your next appointment. They're a starting point for a shared conversation — not a sign you qualify or a recommendation to enrol.
1Based on my diagnosis and history, is this trial worth exploring for me — or is there a standard treatment we should try first?
2What does this trial's phase tell us about how much is already known about its safety and benefit?
3What would taking part actually involve for me — visits, tests, time, and travel?
4What are the known and possible risks or side effects I should weigh, and how would they be monitored?
5If this trial isn't the right fit, what other options or trials would you suggest I look into?
Generated to help you prepare — always confirm anything about your own eligibility and care with the study team and your doctor.
Questions for the trial coordinator
The trial coordinator is the person who runs the study day to day. These cover the practical side — logistics, costs, and what taking part would actually mean for your life. The study team confirms whether you meet the criteria; these are questions to ask, not a sign you qualify.
1What does taking part actually involve week to week — how many visits, where, and how long does each one take?
2What costs are covered by the study, and what might I have to pay for myself, including travel, parking, or time off work?
3What happens during screening, and what happens if the study team confirms I don't meet the criteria after those tests?
4Who pays for the scans, blood work, and other tests the trial requires — the study, my insurance, or me?
5How will being in the trial affect my regular care, and will my own doctor stay informed and involved?
6Can I leave the trial at any point if I change my mind, and what would happen to my care if I do?
A starting point for the conversation — always confirm anything about your own eligibility, costs, and care with the study team and your doctor.
What they're measuring
1
Preoperative LF/HF Ratio as a Predictor of Rebound Pain
Timeframe: Preoperative (before spinal anesthesia) to 48 hours postoperative