In a small dental surgery study, a heart-rate variability index differed by maintenance sedative despite similar clinical sedation scores and shared midazolam premedication.
What the monitor measured
The investigators prospectively enrolled adults undergoing mandibular third molar extraction. All received a small pre-induction dose of midazolam before maintenance with either dexmedetomidine or propofol. The Analgesia Nociception Index used heart-rate variability to characterize autonomic responses. It was not a direct measurement of pain experience or benzodiazepine concentration.
What differed between groups
Twenty-four of 30 enrolled patients were analyzed, 12 per group. Minimum index values were higher with dexmedetomidine in several five-minute intervals, with unadjusted p values below 0.05. Values below 50 occurred intermittently only with propofol. Clinical Ramsay sedation scores were similar, while another monitor, the Patient State Index, differed during sedation. Different readings can coexist because the instruments measure different signals.
What cannot be attributed to midazolam
The attending anesthesiologist selected the maintenance sedative. The study was small, nonrandomized, and exploratory, so the interval comparisons were hypothesis-generating. Respiratory patterns, stress, local anesthetic effects, and supplemental midazolam could influence autonomic tone. Because midazolam premedication was shared, there was no comparison with a group that omitted it. The practical lesson is to interpret an autonomic index alongside the clinical assessment, medication timeline, and procedure. A numerical difference between maintenance groups does not prove a difference in subjective pain or identify midazolam as the cause.
Source paper
Original analysis of the supplied journal article, identified as PMC13053196.
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