Analysis of the efficacy and safety of intravenous injection combined with nebulized inhalation of polymyxin E sodium methanesulfonate in the treatment of carbapenem resistant gram-negative bacterial infections in the lungs.

BACKGROUND

Carbapenem-resistant Gram-negative (CR-GN) pneumonia remains a major therapeutic challenge due to limited effective treatment options and high morbidity. Polymyxin E sodium methanesulfonate (colistin), despite concerns of nephrotoxicity, continues to serve as a last-resort agent. The adjunctive use of nebulized polymyxin may enhance local drug delivery and improve outcomes.

OBJECTIVE

To evaluate the clinical efficacy, microbiological clearance, radiological response, and safety of combined intravenous and nebulized polymyxin E in patients with CR-GN pneumonia, and to identify early predictors of treatment response.

METHODS

This retrospective, single-center observational study included 120 adult patients with microbiologically confirmed CR-GN pneumonia treated between January 2022 and December 2024. All patients received intravenous polymyxin E along with nebulized polymyxin E (50 mg twice daily). Clinical parameters, laboratory markers, radiological findings, and adverse events were assessed at baseline (Day 0), Day 5, and Day 10-14. Multivariate logistic regression and receiver operating characteristic (ROC) curve analysis were performed to identify predictors of poor outcomes.

RESULTS

Significant improvements were observed across clinical parameters, including reduction in temperature (38.6 °C to 36.9 °C), respiratory rate, and improvement in oxygenation (SpO2: 90.2% to 96.1%; PaO2/FiO2: 205.4 to 326.9; p < 0.01). Inflammatory markers, including C-reactive protein and procalcitonin, showed a marked decline over time. Microbiological clearance was achieved in 73.3% of patients, with early culture conversion observed in nearly half by Day 5. Radiological improvement ≥50% was noted in 79.2% of cases. Nephrotoxicity occurred in 15% of patients, bronchospasm in 7.5%, and treatment discontinuation in 3.3%. ROC analysis identified procalcitonin >1.2 ng/mL, CRP >45 mg/L, and PaO2/FiO2 <250 as significant predictors of poor clinical outcomes.

CONCLUSION

Combined intravenous and nebulized polymyxin E therapy was associated with favorable clinical and microbiological outcomes in patients with CR-GN pneumonia, with an acceptable safety profile. Early biomarkers such as procalcitonin, CRP, and oxygenation indices may help guide risk stratification and optimize treatment strategies in critically ill patients.