Highest early blood pressure within 24 hours and mortality after in-hospital cardiac arrest in the oldest ICU patients: A binational cohort study

Cardiac arrest in nonagenarian and centenarian ICU patients carries high mortality, yet the prognostic role of early blood pressure (BP) parameters remains unclear. While most studies have examined nadir or average values, the clinical significance of the highest very early systolic (SBP), diastolic (DBP), and mean arterial pressure (MAP) has not previously been investigated. This study aimed to evaluate whether these peak values within the first 24 h carry prognostic importance in this vulnerable population. We conducted a retrospective multicenter cohort study using data from the ANZICS Adult Patient Database (2010–2024), including 219 patients aged ≥ 90 years admitted to the ICU following in-hospital cardiac arrest. The highest SBP, DBP, and MAP values recorded within the first 24 h were analyzed. Piecewise Cox proportional hazards models adjusted for age, sex, and SOFA score assessed the association between BP parameters and 30-day and 1-year mortality. 30-day and 1-year mortality were 58.0% and 65.8%, respectively. Lower SBP, DBP, and MAP were consistently associated with higher mortality. Each 1 mmHg decrease below SBP 140 mmHg, DBP 74 mmHg, and MAP 100 mmHg decreased the hazard of 30-day mortality by 2.2% (HR 0.978; 95% CI 0.966–0.991), 2.9% (HR 0.971; 95% CI 0.948–0.994), and 2.1% (HR 0.979; 95% CI 0.964–0.994), respectively (all p < 0.05). These associations persisted at 1 year: SBP (HR 0.980; 95% CI 0.968–0.993), DBP (HR 0.980; 95% CI 0.960–1.000), and MAP < 98 mmHg (HR 0.983; 95% CI 0.971–0.995). BP values above these thresholds showed no significant protective effect. SBP and DBP demonstrated a moderate positive correlation (r = 0.553, p < 0.001). In patients ≥ 90 years old admitted to ICU after cardiac arrest, early hypotension—particularly SBP < 140 mmHg, DBP < 74 mmHg, and MAP < 98 mmHg—was independently associated with increased short- and long-term mortality. As SBP and DBP represented the highest recorded values within the first 24 h, these findings highlight that even peak pressures below these thresholds carry prognostic significance, underscoring the value of early BP assessment and vigilant haemodynamic management in the oldest ICU population.