Role of ANSiscope™ in monitoring autonomic dysfunction during anaphylaxis

Dear Editor, The ANSiscope™ is a non-invasive heart rate variability (HRV)-based monitor that assesses autonomic nervous system (ANS) function by analyzing 572 R–R intervals from the electrocardiogram and computing the ANSindex (0%–100%).[1,2] While its use has been described in conditions such as diabetes, spinal cord injury, and perioperative care,[1,3] its application during acute anaphylactic events remains undocumented. We report the use of ANSiscope™ in a 41-year-old gentleman scheduled for discectomy at the C5–C6 level. During pre-anesthetic evaluation, he had no known allergies. On the day of surgery, intravenous diclofenac 75 mg was administered by the neurosurgery team as part of preoperative analgesia plan. Shortly after, he developed pruritus and mild breathlessness and bilateral wheeze. He was treated with intravenous hydrocortisone 100 mg, chlorpheniramine 10 mg, and nebulized salbutamol (2.5 mg). Despite this, he developed hypotension (blood pressure [BP]: 86/46 mmHg), unresponsive to fluid resuscitation, intravenous phenylephrine (100 µg boluses), and mephentermine (6 mg aliquots). Intramuscular epinephrine 0.5 mg was administered, an arterial line was placed, and norepinephrine infusion was started, which stabilized BP. All symptoms occurred in the preoperative period, prior to anesthetic induction. As part of an ongoing observational study, ANSiscope™ had been applied in the preoperative holding area before symptom onset. The baseline ANSindex was 41%, with a low-frequency to high-frequency (LF/HF) ratio of 0.33. After epinephrine and norepinephrine were administered, the ANSindex reduced to 35% (LF/HF: 1.88). During norepinephrine tapering, the ANSindex increased again to 55% (LF/HF: 3.35), coinciding with a drop in MAP and clinical signs of recurrence [Figure 1a], prompting repeat intramuscular epinephrine 0.5 mg and transfer to the intensive care unit. Although treatment decisions were based on standard hemodynamic monitoring [Figure 1a] and clinical evaluation, graphical ANSigrams [Figure 1b-e] show that fluctuations in the ANSindex and LF/HF ratio tracked closely with the clinical course. The monitor indicated worsening autonomic dysfunction even before hypotension recurred during vasopressor tapering.Figure 1: Panel (a) Hemodynamic changes. Panels (b-e) ANSigram plots showing sympathovagal balance at (b) baseline, (c) norepinephrine tapering, (d) post-epinephrine, and (e) after norepinephrine discontinuationAfter stabilization and discontinuation of norepinephrine, the ANSindex improved to 20%. The patient underwent surgery 24 hours later and had an uneventful recovery. The LF/HF ratio is a commonly used surrogate for sympathovagal balance, while the ANSindex quantifies overall autonomic dysfunction, with higher values indicating greater imbalance. An increased LF/HF ratio reflects sympathetic dominance, whereas lower values indicate parasympathetic predominance. During allergen exposure, autonomic imbalance manifests as both sympathetic and parasympathetic overactivity, reflected by increased LF and HF components and reduced RR interval variability (SDNN).[4,5] This is the first report describing the use of ANSiscope™ for real-time observation of autonomic dysfunction during anaphylaxis. Although it was not used for treatment decisions, the temporal correlation between ANS values and symptom progression is notable. Limitations of the device include inability to provide accurate readings during arrhythmias, susceptibility to motion artifacts, dependency on ECG signal quality, and lack of validation in the context of anaphylaxis. The ANS parameters may also be influenced by pharmacologic agents that cause sympathetic activation, independent of the underlying autonomic state. Nonetheless, such observations may inform future evaluations of autonomic patterns during perioperative allergic reactions. Patient declaration of consent statement Appropriate patient consent has been obtained. Declaration of patient consent The authors certify that they have obtained all appropriate patient consent forms. In the form the patient(s) has/have given his/her/their consent for his/her/their images and other clinical information to be reported in the journal. The patients understand that their names and initials will not be published and due efforts will be made to conceal their identity, but anonymity cannot be guaranteed. Financial support and sponsorship Nil. Conflicts of interest There are no conflicts of interest.