Lung Ultrasound in Pediatric Cardiac Surgery: A Complementary Tool for Predicting and Identifying Postoperative Pulmonary Complications

Point-of-care ultrasound is a continuously evolving diagnostic tool used for a variety of diverse applications across multiple specialty areas of medicine.1Bryson GL Grocott HP Point-of-care ultrasound: A protean opportunity for perioperative care.Can J Anaesth. 2018; 65: 341-344Crossref PubMed Scopus (6) Google Scholar In particular, the versatility of lung ultrasound (LUS) to evaluate acute respiratory disorders, noninvasively and at the bedside, has popularized its use among anesthesiologists and intensivists in the perioperative and intensive care unit settings.2Lichtenstein DA. Lung ultrasound in the critically ill.Ann Intensive Care. 2014; 4: 1Crossref PubMed Scopus (310) Google Scholar Several studies involving pediatric patients undergoing cardiac surgery have described the value of perioperative LUS examinations for detecting postoperative pulmonary complications (PPCs), improving outcomes (eg, shortened duration of mechanical ventilation, decreased incidence of postoperative desaturation events), and offering prognostic value as an independent predictor for intensive care unit length of stay.3Vitale V Ricci Z Gaddi S et al.Lung ultrasound profile after cardiopulmonary bypass in paediatric cardiac surgery: first experience in a simple cohort.Interact Cardiovasc Thorac Surg. 2017; 24: 598-602PubMed Google Scholar, 4Song IK Kim EH Lee JH et al.Utility of perioperative lung ultrasound in pediatric cardiac surgery: A randomized controlled trial.Anesthesiology. 2018; 128: 718-727Crossref PubMed Scopus (36) Google Scholar, 5Cantinotti M Giordano R Scalese M et al.Prognostic value of a new lung ultrasound score to predict intensive care unit stay in pediatric cardiac surgery.Ann Thorac Surg. 2020; 109: 178-184Abstract Full Text Full Text PDF PubMed Scopus (16) Google Scholar However, despite this increase in popularity and usage, the adoption of LUS by intensivists caring for pediatric cardiac surgery patients remains far from uniform.6Steppan D DiGiusto M Steppan J Perioperative lung ultrasound in the pediatric intensive care unit-beyond the vasculature and parenchyma.J Cardiothorac Vasc Anesth. 2020; 34: 956-958Abstract Full Text Full Text PDF PubMed Scopus (2) Google Scholar In this issue of the Journal of Cardiothoracic and Vascular Anesthesia, Gothra et al. assessed whether the addition of LUS to a standard practice of clinical examination and chest radiography (CXR) would result in earlier or improved detection of PPCs in pediatric patients undergoing cardiac surgery with cardiopulmonary bypass.7Ghotra GS Kumar B Niyogi SG et al.Role of lung ultrasound in the detection of postoperative pulmonary complications in pediatric patients: a prospective observational study.J Cardiothorac Vasc Anesth. 2021; 35: 1360-1368Abstract Full Text Full Text PDF PubMed Scopus (2) Google Scholar This prospective observational study included 100 children with acyanotic (left-to-right shunt) congenital cardiac lesions, evaluated preoperatively and at 12, 24, 48, and 72 hours after surgery. Ultimately, a total of 33 and 22 PPCs were observed in the early and late postoperative periods, respectively. The authors determined that the addition of LUS to the standard practice of clinical examination and CXR significantly increased the number of PPCs detected in the early postoperative period (ie, at 12 and 24 hours postoperatively), but not in the late postoperative period (ie, at 48 and 72 hours postoperatively). Cantinotti et al. have described the development of an institutional program in which LUS is performed routinely to evaluate common PPCs in patients after pediatric cardiac surgery, including pleural effusions, diaphragmatic excursion anomalies, and pneumothorax.8Cantinotti M Giordano R Assanta N et al.Chest ultrasound: A new, easy, and radiation free tool to detect retrosternal clot after pediatric cardiac surgery.J Cardiothorac Vasc Anesth. 2015; 29: e59-e60Abstract Full Text Full Text PDF PubMed Scopus (12) Google Scholar Investigators from this program, which was designed to reduce the number of CXRs performed and augment diagnostic accuracy for the recognition of PPCs, reported a high feasibility and additive diagnostic value of LUS over CXR in the diagnosis of common pulmonary conditions after pediatric cardiac surgery (eg, pleural effusions, atelectasis, pulmonary congestion).9Cantinotti M Ait Ali L Scalese M et al.Lung ultrasound reclassification of chest X-ray data after pediatric cardiac surgery.Paediatr Anaesth. 2018; 28: 421-427Crossref PubMed Scopus (23) Google Scholar An important conclusion, however, was that LUS should not be considered as a replacement for the CXR. Rather, LUS and CXR should be viewed as complementary evaluations to be employed selectively based on the specific clinical scenario. Similarly, the findings of Gothra et al. suggested that LUS has a complementary role to the standard practice of clinical examination and CXR, but currently is unlikely to replace this approach. Investigators did not evaluate specifically whether LUS could replace CXR; however, their findings highlighted that the optimum benefit of LUS is in the detection of PPC in the early postoperative period. While these findings underscored the diagnostic advantages of LUS in the early postoperative period, no imaging was performed in the immediate time frame after surgery in this study. One is therefore left wondering about any further benefits that may have been observed if LUS had been performed in this even earlier time frame (ie, within the first 12 hours postoperatively). The authors acknowledged this limitation, as well as the potential implications for underestimating the benefits of LUS in the immediate postoperative period in this study. Thus, future research is warranted to evaluate the benefit of LUS in the very early and immediate postoperative periods. Furthermore, there was an observed diagnostic advantage for specific types of PPCs, but not for all forms of pulmonary complications. While LUS increased diagnostic accuracy for pulmonary congestion compared to clinical examination and CXR alone, the low incidence of other PPCs did not allow the study to compare the different image approaches adequately for detecting these other forms of PPCs. As shown by Kaskinen et al., LUS has proven efficacy for estimating extravascular lung water after congenital cardiac surgery, with less interobserver variability than CXR lung edema scores.10Kaskinen AK Martelius L Kirjavainen T et al.Assessment of extravascular lung water by ultrasound after congenital cardiac surgery.Pediatr Pulmonol. 2017; 52: 345-352Crossref PubMed Scopus (22) Google Scholar However, on the flip side, a low sensitivity (45.5%) has been reported for LUS in the diagnosis of pneumothorax in pediatric trauma patients. Gothra et al. cited both of these investigations within their discussion, supporting the stance that the two imaging modalities have a complementary role within the pediatric population. A secondary outcome assessed by Gothra et al. involved the correlation of preoperative and postoperative LUS scores with the occurrence of PPCs. An investigator not involved in the clinical care of patients imaged six zones in each hemithorax and subsequently scored the LUS exam based on the number of B-lines in each zone.11Picano E Pellikka PA. Ultrasound of extravascular lung water: A new standard for pulmonary congestion.Eur Heart J. 2016; 37: 2097-2104Crossref PubMed Scopus (212) Google Scholar The six zones were defined by three longitudinal lines (ie, parasternal, anterior axillary, posterior axillary) and two axial lines (ie, above the diaphragm, 1 cm above the nipple). Similarly, each CXR also was scored by the physician performing the clinical examination (score 1: normal CXR, score 2: patchy atelectasis and/or hyperinflation and/or bronchial wall thickening, score 3: focal consolidation, score 4: multifocal consolidation, score 5: diffuse alveolar changes). The preoperative LUS scores demonstrated a better predictive ability for PPCs in the early postoperative period than the preoperative CXR score, although this difference did not persist after 24 hours. Multivariate analysis showed that the preoperative LUS score was associated independently with PPCs and emerged as an independent predictor for PPCs, mechanical ventilation duration, and intensive care unit stay. These findings supported other recent data showing that LUS provides not only diagnostic but also prognostic information in pediatric cardiac surgery patients. Cantinotti et al. evaluated their own LUS scoring system for its prognostic value, while also comparing this LUS score to conventional risk predictors including age, Society of Thoracic Surgeons/European Association of Cardio-Thoracic Surgery score, cardiopulmonary bypass time, and prognostic biomarkers (ie, brain natriuretic peptide, cystatin-C).5Cantinotti M Giordano R Scalese M et al.Prognostic value of a new lung ultrasound score to predict intensive care unit stay in pediatric cardiac surgery.Ann Thorac Surg. 2020; 109: 178-184Abstract Full Text Full Text PDF PubMed Scopus (16) Google Scholar LUS examinations were performed in 237 pediatric cardiac surgery patients (median age, 0.55 years; interquartile range, 0.09-4.15 years) at 12 and 36 hours postoperatively. When added as a continuous predictor to conventional risk factors, the LUS score was shown to be an independent predictor for duration of intensive care unit length of stay (p = 0.047) and time to extubation (0.024) after pediatric cardiac surgery. The prognostic relevance of LUS score on intensive care unit length of stay and time to extubation has the potential to be particularly advantageous in neonates and complicated patients. Interestingly, post hoc subgroup analysis by Gothra et al. highlighted that early postoperative LUS scores showed a marginally higher predictive ability for PPC in infants versus older patients. Therefore, as the authors suggested, future studies especially evaluating the impact of patient age on the utility of LUS are warranted. As previously discussed, an important limitation of this study was that imaging examinations were not performed in the immediate postoperative period due to multiple logistical constraints, including access to imaging. Many institutions are likely to encounter similar obstacles limiting timely access to imaging modalities. Regarding LUS, a major limitation to widespread availability of ultrasound machines involves fiscal constraints and equipment cost. One potential solution to increasing the availability and accessibility of this technology may lie in the multiple handheld ultrasound systems now commercially available at a fraction of the cost of traditional ultrasound systems.12Baribeau Y Sharkey A Chaudhary O et al.Handheld point-of-care ultrasound probes: The new generation of POCUS.J Cardiothorac Vasc Anesth. 2020; 34: 3139-3145Abstract Full Text Full Text PDF PubMed Scopus (23) Google Scholar Optimistically, increasing availability of these devices may help overcome logistic issues currently limiting access to this technology. Gothra et al. have made an important contribution to the existing literature, confirming the diagnostic utility of LUS in pediatric cardiac surgery. Equally as important, they have provided further support for the prognostic abilities of LUS in this patient population. Both applications of LUS in the domain of pediatric cardiac surgery offer exciting potential for more widespread adoption of this modality in the immediate future. None. Role of Lung Ultrasound in the Detection of Postoperative Pulmonary Complications in Pediatric Patients: A Prospective Observational StudyJournal of Cardiothoracic and Vascular AnesthesiaVol. 35Issue 5PreviewTo evaluate the incremental benefit of lung ultrasound (LUS) over clinical examination and chest x-rays (CXR) together (clinico-radiologic examination) for the diagnosis of postoperative pulmonary complications (PPC). Full-Text PDF