The role of ultrasonographic lung aeration score in the prediction of postoperative pulmonary complications: an observational study

Abstract

Background: Postoperative pulmonary complications (PPCs) are important contributors to mortality and morbidity after surgery. The available predicting models are useful in preoperative risk assessment, but there is a need for validated tools for the early postoperative period as well. Lung ultrasound is becoming popular in intensive and perioperative care and there is a growing interest to evaluate its role in the detection of postoperative pulmonary pathologies.

Objectives: We aimed to identify characteristics with the potential of recognizing patients at risk by comparing the lung ultrasound scores (LUS) of patients with/without PPC in a 24-h postoperative timeframe.

Methods: Observational study at a university clinic. We recruited ASA 2-3 patients undergoing elective major abdominal surgery under general anaesthesia. LUS was assessed preoperatively, and also 1 and 24 h after surgery. Baseline and operative characteristics were also collected. A one-week follow up identified PPC+ and PPC- patients. Significantly differing LUS values underwent ROC analysis. A multi-variate logistic regression analysis with forward stepwise model building was performed to find independent predictors of PPCs.

Results: Out of the 77 recruited patients, 67 were included in the study. We evaluated 18 patients in the PPC+ and 49 in the PPC- group. Mean ages were 68.4 ± 10.2 and 66.4 ± 9.6 years, respectively (p = 0.4829). Patients conforming to ASA 3 class were significantly more represented in the PPC+ group (66.7 and 26.5%; p = 0.0026). LUS at baseline and in the postoperative hour were similar in both populations. The median LUS at 0 h was 1.5 (IQR 1-2) and 1 (IQR 0-2; p = 0.4625) in the PPC+ and PPC- groups, respectively. In the first postoperative hour, both groups had a marked increase, resulting in scores of 6.5 (IQR 3-9) and 5 (IQR 3-7; p = 0.1925). However, in the 24th hour, median LUS were significantly higher in the PPC+ group (6; IQR 6-10 vs 3; IQR 2-4; p < 0.0001) and it was an independent risk factor (OR = 2.6448 CI95% 1.5555-4.4971; p = 0.0003). ROC analysis identified the optimal cut-off at 5 points with high sensitivity (0.9444) and good specificity (0.7755).

Conclusion: Postoperative LUS at 24 h can identify patients at risk of or in an early phase of PPCs.

Keywords: Lung ultrasound; Perioperative care; Point-of-care ultrasound; Postoperative pulmonary complications; Ultrasonography.

Fig. 1

Typical ultrasound patterns with different scores in parentheses. a: A-profile (0 point); b: typical B-profile (1 point). B-lines marked with white arrows; c: small subpleural consolidation (black arrowhead) with clear pleural line (1 point); d: confluent B-profile (2 points); e: multiple subpleural consolidations (white arrowheads) and irregular pleural line (2 points); f: consolidated lung with aerobronchograms (3 points)

Fig. 2

Study flowchart with reasons of exclusion in different stages

Fig. 3

Lung ultrasound scores at different timepoints in the PPC+ and PPC- groups. Median values with interquartile ranges. ***: p < 0.0001 (Mann-Whitney U)

Fig. 4

ROC curve of postoperative 24th hour lung ultrasound scores in the prediction of PPCs