Case Report: A case series: heart rate variability during dental treatment with vasovagal reflex

Abstract

Introduction: The vasovagal reflex is the most frequent emergency that occurs during dental procedures, but its underlying mechanism is not understood. In this study, we conducted autonomic monitoring of patients with a history of vasovagal reflexes.

Case description: We focused on the high-frequency component, an indicator of parasympathetic activity, and interrupted the treatment when the high-frequency component increased. Treatment was then resumed after confirming that there was no mood disturbance and no increase in the high-frequency component. In another patient with a history of dental treatment-induced vasovagal reflex, autonomic activity during treatment was measured under atropine sulfate hydrate administration.

Discussion: Analysis of heart rate variability during the vasovagal reflex showed that parasympathetic hyperactivity was followed by sympathetic hyperactivity, indicating real-time changes in autonomic nervous system activity. In addition, the high-frequency component, which decreased after atropine sulfate hydrate administration, did not increase during treatment, along with the low-frequency to high-frequency ratio, a measure of sympathetic nervous system activity, and the vasovagal reflex did not occur. We believe that the visualization of a patient's autonomic nervous system activity during dental treatment will improve the quality of systemic management and lead to the realization of a safe and comfortable treatment environment.

Keywords: autonomic nervous system activity; case series; dental treatment; heart rate variability; vasovagal reflex.

FIGURE 1

(A,B) Course of LF/HF, HF, HR, and SBP in Case 1. (A) Course at the onset of the vasovagal reflex: extraction of bilateral palatally displaced maxillary second premolars. (B) Course when the vasovagal reflex did not occur: extraction of the left mandibular third molar. Green line: HR, Red line: HF, Blue line: LF/HF, Arrowheads: BP LF/HF: Low frequency/High frequency; HF: High frequency; HR: Heart rate; SBP: Systolic blood pressure; DBP: Diastolic blood pressure. Timeline (A) 14:37–14:47 Rest 14:48 Local anesthesia 14:52 No complaints of feeling unwell 14:53 HF increased; when I asked him, the patient reported feeling unwell 14:55 Lower limb elevation 14:57 Securing intravenous line; administration of atropine 15:05 Local anesthesia 15:10 Extraction 15:13 Extraction. Timeline (B) 15:23 Securing an intravenous line 15:24–15:35 No complaints of feeling unwell 15:41 Incision and flap reflection 15:49 Bone removal 15:58 Separation of the tooth crown 16:02 Extraction 16:04 Separation of the tooth crown 16:07 Extraction 16:15 Suturing. (C,D) Course of LF/HF, HF, HR, and SBP in Case 2 (A) Course at the onset of the vasovagal reflex: extraction of the left mandibular third molar. (B) Course when the vasovagal reflex did not occur: extraction of the right mandibular third molar. Green line: HR, Red line: HF, Blue line: LF/HF, Arrowheads: BP LF/HF: Low frequency/High frequency; HF: High frequency; HR: Heart rate; SBP: Systolic blood pressure; DBP: Diastolic blood pressure Timeline (C) 14:20–14:43 Rest 15:00 Local anesthesia 15:02 Incision and flap reflection 15:04 Bone removal 15:05 Separation of the tooth crown 15:10 Horizontal position; lower limb elevation 15:15 Extraction 15:17 Suturing 15:20 Surgery completed Timeline (D) 14:21 Rest supine position 14:24 Standing position 14:29 Supine position 14:40 Rest 14:44 Local anesthesia 14:48 Incision and flap reflection 14:51 Bone removal 14:54 Separation of the tooth crown 15:00 Extraction 15:03 Suturing 15:10 Rest (E) Course of LF/HF, HF, HR, and SBP in Case 3 (A). Records from the hospital room. (B). Recording vital signs with history of a vasovagal reflex and prophylactic atropine administration during intravenous sedation. Green line: HR, Red line: HF, Blue line: LF/HF, Arrowheads: BP LF/HF: Low frequency/High frequency; HF: High frequency; HR: Heart rate; SBP: Systolic blood pressure; DBP: Diastolic blood pressure Timeline (E) 15:48–15:50 Rest Timeline (F) 14:03 Rest 14:06 Securing intravenous line 14:08 Administration of midazolam and propofol 14:10 Atropine administration 14:17 Local anesthesia 14:27 Upper right 7 extraction 14:29 Upper right 6 extraction 14:38 Local anesthesia 14:40 Lower left tooth 5 extraction 14:44 End of dental treatment 15:03 Opening of eyes.

FIGURE 2

Mechanism of vasovagal reflex and trigeminal cardiac reflex in dental treatment (modified from Figure 13-II-1 of Fukushima Kazuaki et al. Dental Anesthesiology, eighth Edition, ISHIYAKU publishers, 2019; 507.) VVR: Vasovagal reflex; TCR: Trigeminal cardiac reflex; CVLM: Caudal ventrolateral medulla; RVLM: Rostral ventrolateral medulla.