1085: Icp Sensitivity to Co2 Directly Correlates With Intracranial Compliance in Pediatric Tbi Patients

Introduction: In traumatic brain injury (TBI), the relationship between intracranial pressure (ICP), mean blood pressure (MAP), and end-tidal CO2 (EtCO2) provides insight into cerebral autoregulation and cerebrovascular reactivity. We hypothesized that ICP sensitivity and responsivity to CO2 (ISCO2, IRCO2, respectively) would reflect intracranial compliance provided any degree of cerebrovascular reactivity is intact. We investigated the ICP-dependent dynamics of ISCO2 and IRCO2 in pediatric TBI patients compared to established ICP waveform-derived compliance metrics Methods: In this IRB approved study, retrospective monitor data (2018-2024) from pediatric TBI patients was screened for invasive pulsatile ICP, MAP and EtCO2 recordings. The RAP index, defined as the temporal correlation [R] between ICP pulse amplitude [A] and mean ICP [P], and compensatory-reserve-weighted ICP [wICP = (1-RAP) × ICP] were calculated. Multivariate ordinary least squares regression of ICP against MAP, EtCO2 and heart rate (2-second sampling) was used to compute time-varying IRCO2 and ISCO2. Data reported as Median [Q1-Q3] Results: Data from 20 patients were extracted (median age: 8.5 y/o [3.0-12.3], Male/Female: 11/9, Survived/Deceased: 14/6). Across all patients, ISCO2 correlated strongly with RAP index (r=0.76) for ICP < 50 mmHg. Both metrics showed inverted U-shaped relationships with ICP, peaking at ~25 mmHg. IRCO2 had strong inverse correlation with wICP (r=-0.81). ISCO2 increased between ICP< 20 and 20-50 mmHg but decreased significantly when ICP>50 mmHg. Patients with craniectomies had significantly lower ISCO2 (0.47 [0.43-0.54] vs 0.83 [0.62-1.05], p=0.006) and RAP indices (0.23 [0.08-0.33] vs 0.58 [0.45-0.68], p=0.003). In patients without craniotomies when mean ICP was < 20 mmHg, non-survivors had significantly lower IRCO2 and trended toward lower ISCO2 and higher wICP vs survivors (IRCO2: 0.16 [0.12-0.19] vs 0.27 [0.26-0.29], p=0.02; ISCO2: 0.58 [0.50-0.60] vs 0.83 [0.80-1.07], p=0.06; wICP: 9.15 [7.45-9.49] vs 3.99 [3.17-6.52], p=0.06) Conclusions: ISCO2 and IRCO2 closely track established intracranial compliance and cerebrovascular reactivity metrics in pediatric TBI. ISCO2 and IRCO2 could be physiologically grounded biomarkers derived from routine monitoring data that could augment neuromonitoring for TBI patients