Higher Total serum bilirubin levels independent risk factor for 1-year mortality in patients with ARF

It is already known that TBIL levels are a risk factor in patients who are critically ill. However, there remains an unclarity of the relationship between TBIL dynamics and the prognosis of ARF patients.

Considering this, a study was conducted by a team of researchers led by Zhishen Ruan from the Shandong Traditional Chinese Medicine University to investigate,

What is the impact of different levels of Total Bilirubin during hospitalization on the mortality of patients with ARF?

The study summary includes the following:

• The relevant patient information was extracted from Medical Information Bank for Intensive Care (MIMIC)-III (version 1.4).
• The researchers used propensity score matching PSM, Cox regression and subgroup analysis for adjustments and analysis of mortality risk factors and special populations.
• The study had 2673 patients.
• During hospitalization, 19.7% of patients developed hyperbilirubinemia, and total bilirubin values were ≥ 2 mg/dL.
• After PSM, multivariate Cox regression showed a 50% and 135% increased risk of death for a maximum value of TBIL ≥ 5 mg/dL and minimum value of TBIL ≥ 2 mg/dL during hospitalization, respectively than the control population.
• The independent risk factors for one-year mortality in ARF patients were age ≥ 65 years, previous comorbid malignancies, respiratory rate ≥ 22 beats/min, SpO2 ≥ 95, BUN ≥ 20 mg/dL, lactate ≥ 5 mmol/L, platelet < 100 * 10 ^ 9/L.
• The high bilirubin had a more significant effect on patients of age less than 65 years, as shown in the subgroup analysis.

Since bilirubin can often be used as a surrogate marker of liver function, this large retrospective cohort study evaluated elevated bilirubin levels in critically ill patients with acute respiratory failure. The results demonstrated that a significant proportion of patients with acute respiratory failure developed high bilirubin levels throughout hospitalization, and elevation ≥5 mg/dL was associated with increased mortality. Other factors associated with increased mortality in these patients included older age and elevated lactate levels.

This study emphasizes the relationship between liver damage and respiratory failure. Hypoxia can lead to hypoxic hepatitis, or advanced liver dysfunction can worsen lung ventilation/perfusion mismatch. Thus, we should consider respiratory failure's implications on the multiorgan system. It is also important to note that this study excluded patients with chronic liver disease.

Further reading:

Ruan, Zhishen, et al. “Association of Serum Total Bilirubin and Potential Predictors With Mortality in Acute Respiratory Failure: A Retrospective Cohort Study.” Heart & Lung, vol. 57, Elsevier BV, Jan. 2023, pp. 12–18. Crossref, https://doi.org/10.1016/j.hrtlng.2022.08.006.