Hemodynamic Changes Associated with Lateralized Periodic Discharges: A Near-Infrared Spectroscopy and Continuous EEG Study

Background: Lateral periodic discharges (LPDs) have been recognized as a common electroencephalographic (EEG) pattern in critically ill patients. However, management decisions in these patients are still a challenge for clinicians. This study investigates hemodynamic changes associated with LPDs and evaluates if this pattern is likely to represent an ictal, interictal, or ictal-interictal continuum phenomenon via non-invasive near infra-red spectroscopy (NIRS) with concurrent with continuous EEG.

Methods: Seventeen patients admitted to the intensive care unit with LPDs on continuous electroencephalogram (EEG) were included. Participants engaged in NIRS recording-with scalp probes on right and left frontal regions simultaneously. Associations between LPDs laterality, primary frequency, NIRS a of cerebral oxygen saturation (SO₂), total hemoglobin concentration (tHb), oxygenated hemoglobin concentration (O₂Hb), de-oxygenated hemoglobin concentration (HHb), and variables in participant medical history were studied.

Results: Hemispheres with LPDs showed higher overall SO₂ when compared to non-LPDs hemispheres (57% vs 52%, p = 0.03). Additionally, mildly increased tHb, O₂Hb, and mildly decreased HHb concentrations were detected in the hemisphere showing LPDs, but changes were not statistically significant. A higher primary frequency of LPDs was associated with lower cerebral SO₂ (Pearson correlation r = - 0.55, p = 0.022) and O₂Hb (Pearson correlation r = - 0.52, p = 0.033). In patients with seizure during their EEG recording (64.7%), lower tHb (28.2 μmol/L vs 37.8 μmol/L, p = 0.049) and O₂Hb (15.5 μmol/L vs 24.2 μmol/L, p = 0.033) were recorded in the LPDs hemisphere.

Conclusions: This study demonstrates an increased cerebral SO₂ in the hemisphere with LPDs, and decreased SO₂ and O₂Hb when the frequency of LPDs increases. The findings indicate that LPDs increase oxygen demand on the ipsilateral hemisphere. We infer that a threshold of LPDs frequency might exit, when the cerebral oxygen demand begins to supersede the ability of delivery, and saturation decreases.