Relationship between the magnitude of haemoglobin changes and long-term mortality in patients with sepsis: a retrospective cohort study

Abstract

Background: Sepsis is a common and severe disease with a high mortality rate in intensive care unit (ICU). The hemoglobin (HGB) level is a key parameter for oxygen supply in sepsis. Although HGB is associated with the progression of inflammation in sepsis patients, its role as a marker following sepsis treatment remains unclear. Here, we studied the correlation between early temporal changes in HGB levels and long-term mortality rates in septic patients.

Method: In this retrospective study of data on patients with sepsis from the Medical Information Mart for Intensive Care (MIMIC) IV database, the outcome was long-term mortality. Patients were divided based on the cut-off of the HGB percentage for receiver operating characteristic (ROC) curve calculation. Kaplan-Meier (KM) survival curves and Cox proportional hazards regression models were used to analyse the associations between groups and outcomes. Propensity score matching (PSM) was used to verify the results.

Results: In this study, 2042 patients with sepsis and changes in HGB levels at day 4 after admission compared to day 1 were enrolled and divided into two groups: group 1 (n = 1147) for those with reduction of HGB < 7% and group 2 (n = 895) for those with dropping ≥ 7%. The long-term survival chances of sepsis with less than a 7% reduction in the proportion of HGB at day four were significantly higher than those of patients in the group with a reduction of 7% or more. After adjusting for covariates in the Cox model, the hazard ratios (HRs) with 95% confidence intervals (CIs) for long-term all-cause mortality in the group with a reduction of 7% or more were as follows: 180 days [HR = 1.41, 95% CI (1.22 to 1.63), P < 0.001]; 360 days [HR = 1.37, 95% CI (1.21 to 1.56), P < 0.001]; 540 days [HR = 1.35, 95% CI (1.20 to 1.53), P < 0.001]; 720 days [HR = 1.45, 95% CI (1.29 to 1.64), P < 0.001]. Additionally, the long-term survival rates, using Kaplan-Meier analysis, for the group with a reduction of 7% or more were lower compared to the group with less than 7% reduction at 180 days (54.3% vs. 65.3%, P < 0.001), 360 days (42.3% vs. 50.9%, P < 0.001), 540 days (40.2% vs. 48.6%, P < 0.001), and 720 days (35.5% vs. 46.1%, P < 0.001). The same trend was obtained after using PSM.

Conclusion: A ≥ 7% decrease in HGB levels on Day 4 after admission was associated with worse long-term prognosis in sepsis patients admitted to the ICU.

Keywords: HGB; Long-term; MIMIC-IV database; Propensity score matching; Sepsis.

Fig. 1

Study flow diagram depicting exclusion criteria and outcomes. Abbreviations: MIMIC medical information mart for intensive care, ICU intensive care unit, HGB haemoglobin, Group 1: < 7% Haemoglobin decrease, Group 2: > 7% Haemoglobin decrease

Fig. 2

Kaplan‒Meier survival curves of the groups. All-cause mortality before matching was significantly lower in the group 1 than in the group 2 at 180 days, 360 days, 540 days and 720 days (A, B, C, D). Abbreviations: K-M kaplan–meier, HGB haemoglobin, Group 1: < 7% Haemoglobin decrease, Group 2: > 7% Haemoglobin decrease

Fig. 3

K‒M survival curves of the groups. All-cause mortality postmatching was significantly lower in the group 1 than in the group 2 at 180 days, 360 days, 540 days and 720 days (E, F, G, H). Abbreviations: K-M kaplan–meier, HGB haemoglobin, Group 1: < 7% Haemoglobin decrease, Group 2: > 7% Haemoglobin decrease