The value of diaphragmatic ultrasound combined with procalcitonin, B-type natriuretic peptide, and lactate in assessing short-term prognosis of sepsis

Background: Sepsis is one of the leading causes of death in critically ill patients. Currently, commonly used clinical prognostic scoring systems such as Sequential Organ Failure Assessment (SOFA) score and Acute Physiology and Chronic Health Evaluation II (APACHE II), although having certain predictive value, have limited sensitivity in reflecting real-time organ functional status. Diaphragmatic dysfunction is significantly associated with mortality in septic patients. However, traditional methods for assessing diaphragmatic function are complex. This study aims to investigate the predictive value of a novel assessment model that combines bedside diaphragmatic ultrasound with procalcitonin (PCT), B-type natriuretic peptide (BNP), and lactate (Lac) for short-term prognosis (28-day mortality) in septic patients, in order to provide a more convenient and dynamic prognostic assessment tool for clinical practice.

Methods: This retrospective study enrolled 74 sepsis patients at Beijing Chaoyang Hospital from September 2021 to June 2023. All eligible patients with sepsis during the study period were included. Based on 28-day mortality, patients were categorized into survivors (n=45) and non-survivors (n=29). Demographic data, APACHE II scores, and laboratory measurements (PCT, BNP, Lac) within 24 hours of admission were collected. Diaphragmatic function was assessed via bedside ultrasonography: diaphragm excursion (DE) was measured during quiet breathing, and diaphragm thickness at end-inspiration (DTei) and end-expiration (DTee) were recorded to compute the diaphragmatic thickening fraction (DTF). Group comparisons were performed. Variables showing significant differences or clinical relevance in univariate analyses were entered into a multivariate logistic regression model to identify independent prognostic factors. Model performance was assessed using receiver operating characteristic (ROC) curve analysis.

Results: (I) Baseline characteristics were similar between groups. (II) Non-survivors exhibited significantly elevated serum PCT, BNP, and Lac levels, alongside reduced DTei, DTee, DTF, and DE values. The non-survivor group had lower DTei, DTee, DTF, and DE, with means of 0.21±0.02 cm, 0.17±0.02 cm, 22.11%±5.81%, 1.08±0.21 cm, respectively. (III) Univariate analysis revealed PCT, BNP, Lac, DTF, and DE were significantly associated with 28-day mortality in sepsis patients, with odds ratios (ORs) of 1.028, 1.114, 1.626, 0.879, and 0.008, respectively. Multivariable logistic regression confirmed DTF and DE as independent predictors, with ORs of 0.892 and 0.051, respectively. ROC analysis demonstrated that the combined use of all five parameters yielded the highest predictive accuracy [area under the curve (AUC) =0.890; sensitivity 96.6%, specificity 57.80%], outperforming individual markers.

Conclusions: Diaphragmatic ultrasonography (DTF and DE) combined with serum biomarkers (PCT, BNP, Lac) enhances the predictive capability for short-term (28-day) survival in sepsis patients, aids in the early identification of high-risk patients, and provides early warning for clinical intervention, although its specificity remains limited.