Abstract Body: Introduction: The physiologic response to epinephrine during pediatric CPR varies and poor response is associated with worse outcomes. Though vasopressin is not recommended by CPR guidelines, laboratory data show a physiologic response to vasopressin among epinephrine non-responders. We aimed to explore the physiologic response to vasopressin during pediatric IHCA.

Hypothesis: Vasopressin is associated with an increase in diastolic blood pressure (DBP) compared to epinephrine in patients with ≥1 dose of epinephrine.

Methods: Single-center retrospective cohort study of pediatric ICU IHCAs with prospectively collected physiologic and arrest event data (2017-2023). Vasopressin subjects received ≥1 dose of epinephrine preceding vasopressin and were matched to patients who received epinephrine at the same time in CPR based on age, illness category (cardiac vs. non-cardiac) and total epinephrine doses prior to the matched dose. DBP response to vasopressor was analyzed with regression discontinuity and the per subject responsiveness (≥5mmHg increase following the dose). A secondary analysis explored time to ROSC from time of vasopressin or epinephrine using Cox regression with censoring of all subjects 20 minutes post-dose.

Results: Of 556 IHCAs with ≥1 dose epinephrine, 52 received vasopressin, and 41 met inclusion criteria and matched with epinephrine-only subjects. Median CPR duration was 36.5 [IQR 23, 48] minutes; median time to study dose was 14.5 [10.8, 19] minutes. ROSC occurred in 10/41 (24%) vasopressin subjects and 15/41 (36%) epinephrine subjects (p=0.34). There was no difference in time to ROSC from study dose (aHR 0.73 [95% CI 0.31 -1.7]). Arterial BP waveform data were evaluable in 12/41 (29%) vasopressin and 7/41 (17%) epinephrine subjects. Vasopressor responsiveness occurred in 4/12 (33%) vasopressin and 1/7 (14%) epinephrine subjects (p=0.60). Figure 1 shows trend in DBP by treatment group around drug delivery, along with regression discontinuity plots of DBP for each drug. Regression discontinuity showed a change in DBP of +2.3mmHg after vasopressin (95% CI: –11.4, 16.0) and -5.67mmHg after epinephrine (–15.13, 3.80).

Conclusion: In a small cohort of IHCA patients with ≥1 epinephrine dose, we did not detect a DBP response to vasopressin or epinephrine. Prolonged time to vasopressin in this cohort may have played a role in these findings; a larger sample of children receiving vasopressin earlier in IHCA will be required for future work.