Surgery remains the mainstay treatment for older patients with lung cancer, and paravertebral block (PVB) is recommended for perioperative analgesia. With the increasing surgical demand, a growing proportion of elective thoracic procedures in China are scheduled at night. Circadian variation, prolonged fasting, and resource limitations may affect intraoperative hemodynamics. However, the comparative hemodynamic safety of daytime versus nighttime PVB has not been systematically investigated. We emulated a target trial using routinely collected anesthesia and electronic medical records from the Cancer Hospital Chinese Academy of Medical Sciences (Oct-2020 to Jun-2022). Patients aged ≥65 years undergoing lung cancer surgery with PVB were classified into daytime (08:00-16:59) or nighttime (17:00-7:59) groups. Confounding was addressed with stabilized inverse probability of treatment weighting. The primary outcomes were intraoperative hypotension (systolic blood pressure <90 mmHg or diastolic blood pressure <60 mmHg) and bradycardia (heart rate <60 bpm). Secondary outcomes included intravenous fluid volume and vasoactive drug use. Time-to-first and recurrent events were assessed using weighted Cox and Poisson regression. Sensitivity analyses included propensity score matching, restricting to patients with PVB after general anesthesia, and adding surgical type as a covariate. Among 637 patients (479 daytime, 158 nighttime), nighttime PVB was associated with more recurrent hypotension (adjusted-incidence rate ratio [IRR]: 1.04; 95% confidence interval [CI], 1.01-1.09), but no difference in bradycardia (hazard ratio [HR]: 1.11, 95% CI, 0.90-1.36; IRR 1.02, 95%CI 0.98-1.05). Intravenous fluid use was lower at night (mean difference -53.20 mL; 95% CI, -104.36 to -2.04). Findings were robust across sensitivity analyses, with stronger associations in women and patients with hypertension or arrhythmia. We conclude that in older patients undergoing lung cancer surgery, nighttime PVB was linked to a modestly higher burden of hypotension and lower fluid administration compared with daytime PVB. Vigilant monitoring and optimized perioperative management are warranted, and multicenter studies should validate these findings.
