The association of diastolic arterial pressure and heart rate with mortality in septic shock: a retrospective cohort study

Abstract

The effects of diastolic arterial pressure (DAP) and heart rate (HR) on the prognosis of patients with septic shock are unclear, and whether these effects persist over time is unknown. We aimed to investigate the relationship between exposure to different intensities of DAP and HR over time and mortality at 28days in patients with septic shock. In this cohort study, we obtained data from the Medical Information Mart for Intensive Care IV, which includes the data of adult patients (≥ 18years) with septic shock who underwent invasive blood pressure monitoring. We excluded patients who received extracorporeal membrane oxygenation (ECMO) or glucocorticoids within 48h of ICU admission. The primary outcome was mortality at 28days. Piece-wise exponential additive mixed models were used to estimate the strength of the associations over time. In total, 4959 patients were finally included. The median length of stay in the ICU was 3.2days (IQR: 1.5-7.1days), and the mortality in the ICU was 12.9%, with a total mortality at 28days of 15.9%. After adjustment for baseline and time-dependent confounders, both daily time-weighted average (TWA) DAP and HR were associated with increased mortality at 28days and strong association, mainly in the early to mid-stages of the disease. The results showed that mortality in patients with septic shock was lowest at a DAP of 50-70mm Hg and an HR of 60-90 beats per minute (bpm). Throughout, a significant increase in the risk of death was found with daily exposure to TWA-DAP ≤ 40mmHg (hazard ratio 0.99, 95% confidence interval (CI) 0.94-1.03) or TWA-HR ≥ 100bpm (hazard ratio 1.16, 95% CI 1.1-1.21). Cumulative and interactive effects of harmful exposure (TWA-DAP ≤ 40mmHg and TWA-HR ≥ 100bpm) were also observed. The optimal ranges for DAP and HR in patients with septic shock are 50-70mmHg and 60-90bpm, respectively. The cumulative and interactive effects of exposure to low DAP (≤ 40mmHg) and tachycardia (≥ 100bpm) were associated with an increased risk of death.