Transthoracic Coronary Sinus Blood Flow Monitoring and PC6 Transcutaneous Electrical Acupoint Stimulation in Elderly Hip Fracture Surgery: A Three-phase Randomised Trial

Background Perioperative myocardial injury in elderly hip fracture patients is usually silent and arises mainly from oxygen supply–demand mismatch. Transthoracic echocardiographic coronary sinus blood flow (CSBF) has been proposed as a non-invasive window on coronary perfusion, but its obtainability in this frail population is unknown. This trial assessed whether a definitive trial of PC6 transcutaneous electrical acupoint stimulation (TEAS) using such monitoring is feasible. Methods Three-phase, single-centre, sham-controlled randomised pilot and feasibility trial (June 2023–May 2025). Phase I (n = 30) assessed CSBF obtainability and acute responses to bilateral PC6 TEAS; Phase II (n = 60) explored stimulation parameters in a 2 × 2 factorial (2 vs. 5 Hz; 15 vs. 25 min); Phase III (n = 40) applied the leading combination under standardised total intravenous anaesthesia. Primary outcomes were feasibility outcomes: CSBF obtainability, predictors of measurement failure, recruitment, retention and safety. Clinical measures were secondary and exploratory, and progression criteria were pre-specified. The study was not powered to detect efficacy effects. Results Adequate CSBF spectra were obtainable in 64% of patients (55/85, Phases I–II). Chronic obstructive pulmonary disease (adjusted odds ratio 3.45), body mass index above 25 kg/m 2 (2.87) and thoracic kyphosis (3.21) independently predicted failure; obtainability reached 90.5% when none was present but fell to 56.8% intraoperatively. Recruitment averaged 4.4 patients/month, no patient was lost to follow-up, and no adverse event was attributable to TEAS. Exploratory estimates: coronary sinus velocity–time integral rose 20.8% (95% CI 11.2–30.4) without change in mean arterial pressure; rate-pressure product remained below 12,000 throughout in the TEAS arm, with a pooled between-group separation of 1759 (95% CI 876–2642) at peak-stress time points. Discussion A definitive trial is feasible, but not with transthoracic CSBF as its monitoring backbone: the technique fails in approximately a third of patients, and selectively in those at highest cardiovascular risk. We recommend proceeding with an amended protocol that substitutes pulse-wave analysis. The haemodynamic signals reported here are hypothesis-generating. Trial registration Chinese Clinical Trial Registry (https://www.chictr.org.cn), ChiCTR2600126845; registered 17 June 2026, retrospectively registered. Recruitment ran from June 2023 to May 2025, so registration followed completion of recruitment.