The capacity of neurological pupil index to predict the absence of somatosensory evoked potentials after cardiac arrest - An observational study

Meena Thuccani; Sara Joelsson; Linus Lilja; Axel Strålin; Josefin Nilsson; Petra Redfors; Araz Rawshani; Johan Herlitz; Peter Lundgren; Christian Rylander

doi:10.1016/j.resplu.2024.100567

The capacity of neurological pupil index to predict the absence of somatosensory evoked potentials after cardiac arrest - An observational study

Resusc Plus. 2024 Feb 3:17:100567. doi: 10.1016/j.resplu.2024.100567. eCollection 2024 Mar.

Authors

Meena Thuccani^{1

2}, Sara Joelsson^{3

4}, Linus Lilja^{5

6}, Axel Strålin⁵, Josefin Nilsson⁴, Petra Redfors^{3

7}, Araz Rawshani^{1

2}, Johan Herlitz^{1

8}, Peter Lundgren^{1

8

2}, Christian Rylander⁹

Affiliations

¹ Department of Molecular and Clinical Medicine, Institute of Medicine, Sahlgrenska Academy, University of Gothenburg, Gothenburg, Sweden.
² Department of Cardiology, Sahlgrenska University Hospital, Gothenburg, Sweden.
³ Department of Clinical Neuroscience, Institute of Neuroscience and Physiology, Sahlgrenska Academy, University of Gothenburg, Gothenburg, Sweden.
⁴ Department of Clinical Neurophysiology, Institute of Neuroscience and Physiology, Sahlgrenska Academy, University of Gothenburg, Gothenburg, Sweden.
⁵ Department of Anaesthesiology and Intensive Care Medicine, Institute of Clinical Sciences, Sahlgrenska Academy, University of Gothenburg, Gothenburg, Sweden.
⁶ Department of Anaesthesia and Intensive Care, Karlstad Central Hospital, Karlstad, Sweden.
⁷ Department of Neurology, Sahlgrenska University Hospital, Gothenburg, Sweden.
⁸ Prehospen - Centre for Prehospital Research, University of Borås, Sweden.
⁹ Anaesthesiology and Intensive Care, Department of Surgical Sciences, Uppsala University, Uppsala, Sweden.

Abstract

Background: In neurologic prognostication of comatose survivors from cardiac arrest, two independent predictors of poor outcome are the loss of the Pupillary light reflex (PLR) and the loss of the N20 response from Somatosensory Evoked potentials (SSEP). The PLR can be quantitatively assessed by pupillometry. Both tests depend on the midbrain, in which a dysfunction reflects a severe hypoxic injury. We reasoned that a certain level of defective PLR would be predictive of a bilaterally absent SSEP N20 response.

Method: Neurological Pupil index (NPi) from the pupillometry and the SSEP N20 response were registered >48 h after cardiac arrest in comatose survivors. Clinical data were retrospectively analyzed. A receiver operating characteristic curve was used to evaluate the capacity of NPi to predict bilaterally absent SSEP N20 response. An NPi threshold value resulting in <5% false positive rate (FPR) for bilaterally absent N20 response was identified.

Results: From February 2020 to August 2022, we included 54 patients out of which 49 had conclusive pupillometry and SSEP examinations. The NPi threshold value with FPR < 5% was 3.4, yielding 36% sensitivity (95% CI 18-55) and significantly discriminated between respective groups with preserved and bilaterally absent N20 response to SSEP (p-value <0.01).

Conclusion: In this limited cohort, NPi < 3.4 in patients remaining comatose >48 hours after cardiac arrest predicted bilateral loss of the SSEP N20 response with a FPR < 5%. If validated in a larger cohort, an NPi threshold may be clinically applied in settings where SSEP is unavailable.

Keywords: Cardiac arrest; Neurological outcome; Neurological pupil index; Prognostication; Pupillometry; Somatosensory evoked potentials.