Systemic Immune Inflammation Index (SII) and Prognostic Nutritional Index (PNI) Associated with Prolonged Intensive Care Unit (ICU) Stay in Patients with Pneumonia Complicated with Respiratory Failure.

Background: The length of intensive care unit (ICU) stay is an important index reflects the prognosis of severe pneumonia (SP) combined with respiratory failure (RF). Blood transfusion can alleviate tissue hypoxia in ICU patients, but blood transfusion can affect the prognosis of patients. The objective of this study was to evaluate the effect of immune-nutritional indices (pan-immune inflammation value (PIV), systemic immune inflammation index (SII), system inflammation response index (SIRI), neutrophil-to-albumin ratio (NAR), and prognostic nutritional index (PNI)) on length of stay in patients treated with and without transfusion.

Methods: Total of 3425 pneumonia combined with respiratory failure patients were retrospectively analyzed. Medical records (age, gender, body mass index, history of smoking, history of alcohol drinking, hypertension, diabetes mellitus, lung diseases, invasive mechanical ventilation, blood transfusion, APACHE II score, and laboratory test results) were collected, the relationship between this information and prolonged ICU stay was analyzed.

Results: The average length of ICU stay was 5.32 (2.94, 9.36) days, there were 2521 (73.6%) patients with non-prolonged ICU stay (<9 days) and 904 (26.4%) with prolonged ICU stay (≥9 days). The levels of PIV, SII, and SIRI in prolonged ICU stay patients were higher than those of non-prolonged ICU stay in patients with and without blood transfusion, respectively. Multivariate logistic regression analysis showed that high SII (odds ratio (OR): 2.115, 95% confidence interval (CI): 1.428-3.131, p<0.001), and invasive mechanical ventilation (OR: 10.205, 95% CI: 5.623-18.524, p<0.001) were associated with prolonged ICU stay in patients with blood transfusion; and low PNI (OR: 1.378, 95% CI: 1.073-1.769, p=0.012), invasive mechanical ventilation (OR: 3.566, 95% CI: 2.666-4.771, p<0.001) were associated with prolonged ICU stay in patients without blood transfusion.

Conclusion: High SII level and invasive mechanical ventilation were independently associated with prolonged ICU stay in patients treated with blood transfusion; and low PNI level and invasive mechanical ventilation were independently associated with prolonged ICU stay in patients without blood transfusion.