Mortality and factors associated with acute exacerbation after non-cardiac surgery in patients with interstitial pneumonia: a retrospective study

BACKGROUND: Acute exacerbation of interstitial pneumonia (AE-IP) is associated with high mortality rates. Although the risk factors for AE-IP have been extensively studied, given the small sample sizes, only a few risk factors have been established. This study aimed to investigate the postoperative mortality and factors associated with AE-IP. METHODS: This retrospective study included 482 patients with a preoperative diagnosis of IP who underwent noncardiac surgery between December 2012 and April 2020. AE-IP was diagnosed by a radiologist using computed tomography when worsening respiratory symptoms were observed within 1 month postoperatively. The Cox proportional hazards model was used to compare mortality rates. Candidate factors associated with AE-IP were identified through logistic regression analysis using the variable selection method, followed by case-control analysis using propensity score matching to determine possible factors associated with AE-IP. RESULTS: The multivariable-adjusted hazard ratios for all-cause and IP-related deaths were significantly higher in patients with AE-IP than in those without AE-IP. Multivariable analysis with variable selection suggested that male sex, higher C-reactive protein (CRP) levels, fraction of inspired oxygen (FiO2) ≥ 60%, and non-lung surgery were candidate factors associated with AE-IP. Case-control analysis using propensity score matching demonstrated that patients with AE-IP had higher CRP levels (P = 0.044) and frequency of FiO2 ≥ 60% (P = 0.035) than those without AE-IP. Furthermore, a positive, nearly linear relationship was observed between FiO2 ≥ 60% duration and AE-IP incidence. CONCLUSIONS: Intraoperative management with FiO2 ≥ 60% and high preoperative CRP levels were significantly associated with postoperative AE-IP.