This sounds most consistent with significant pre-operative anxiety / panic symptoms rather than a primary heart rhythm problem, especially since the palpitations are linked to fear, nighttime panic, and thoughts about surgery/anesthesia. A heart rate of 140–150 bpm can happen during intense anxiety or panic attacks because of an adrenaline surge. A salivary gland stone surgery is usually considered a relatively routine procedure, and modern anesthesia is very safe when pre-anesthetic evaluation is normal. A few practical points that usually help: * Meet the anesthesiologist before surgery and openly discuss: * fear of anesthesia * palpitations * prior panic episodes * sleep disturbance * You will benefit from a mild anti-anxiety medication the night before or morning of surgery. * Avoid excessive Google/YouTube searching about surgical complications — it often worsens anticipatory anxiety. * Reduce caffeine/energy drinks for a few days before surgery. * Sleep deprivation increases palpitations and panic symptoms. When the fear surge starts: * Slow breathing helps reduce adrenaline: * inhale 4 seconds * hold 2 seconds * exhale 6 seconds * repeat for 3–5 minutes Before surgery ensure: * ECG * blood pressure check * hemoglobin * thyroid function if symptoms suggest it * anesthetic fitness evaluation