Heart Rate Variability as a Predictor of Rebound Pain Following Total Knee Arthroplasty

Konya City Hospital110 enrolled

Overview

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.

Study Type

OBSERVATIONAL

Enrollment

110

Conditions

Rebound Pain Total Knee Arthroplasty Postoperative Pain, Chronic Heart Rate Variability

Eligibility

Medical Language ↔ Plain English

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

Outcomes

Primary Outcomes

Preoperative LF/HF Ratio as a Predictor of Rebound Pain

To determine whether the preoperative low frequency to high frequency (LF/HF) ratio of heart rate variability is associated with the development of rebound pain after peripheral nerve block resolution. Patients will be classified based on the presence or absence of rebound pain (defined as a shift from NRS ≤3 to ≥7), and mean LF/HF ratios will be compared. Predictive capacity will be evaluated using logistic regression and ROC analysis.

Time frame: Preoperative (before spinal anesthesia) to 48 hours postoperative

Secondary Outcomes

Association Between HRV Parameters and Pain Intensity

Correlation between perioperative HRV values (SDNN, RMSSD, LF/HF) and postoperative pain scores (measured by NRS at 8h, 12h, 16h, 24h, and 48h).

Time frame: 0-48 hours postoperative