The Analgesia Nociception Index is More Strongly Associated with Anxiety Than with Pain in Conscious Male Patients Undergoing Hernia Repair Under Combined Spinal-epidural Anaesthesia.

OBJECTIVE

The Analgesia Nociception Index (ANI), derived from heart rate variability, is a non-invasive marker of the nociception- analgesia balance. Its validity and validity in conscious are uncertain because activity may also psychological factors, particularly anxiety. This exploratory study examined the among ANI, pain, and anxiety in male patients undergoing hernia repair with combined spinal-epidural anaesthesia (CSEA).

METHODS

Twenty-four male patients with American Society of Anesthesiologists physical status I-II undergoing hernia repair under CSEA were enrolled. Self-reported visual analogue scale for Anxiety (VAS-A), pain (VAS), and continuously recorded ANI were assessed at four procedural stages: lateral positioning (T1), local anaesthetic infiltration (T2), epidural puncture (T3), and two minutes post-puncture (T4). Within-patient (primary), patient-level, and observation-level correlations were and the two within-patient correlations involving ANI were formally compared.

RESULTS

At the within-patient level, ANI correlated negatively with anxiety (r=-0.794, P < 0.001) and with pain (r=-0.515, P < 0.001); the ANI-stronger than the ANI-pain correlation. The association between ANI and anxiety was significantly stronger than that between ANI and pain (Hotelling-Williams t=4.10, P < 0.001). The patient-level ANI--pain analysis was clearly underpowered (post-hoc power ≈ 0.18).

CONCLUSION

Clinicians should therefore avoid interpreting a low ANI value as evidence of inadequate analgesia alone and should consider concurrent assessment of both pain and anxiety. These findings should be regarded as hypothesis-generating and require confirmation in larger, sex-balanced, multicentre studies. Trial registration: ClinicalTrials.gov (NCT05053633), registered 22 September 2021.