Original ArticleClinical Correlation of Early Atelectasis after Bilateral Internal Thoracic Artery Harvest for Coronary Artery Bypass Grafting
Introduction
Respiratory insufficiency remains a significant complication after coronary bypass graft (CABG) surgery. The aetiology of respiratory dysfunction is multifactorial however postoperative atelectasis is recognised as a common contributor resulting in decreased lung compliance, increased pulmonary vascular resistance, impaired oxygenation [1] and an increased risk of postoperative pneumonia [1].
The incidence of atelectasis after heart surgery has been previously reported, however this data reflects older surgical strategies for CABG that may not be currently relevant, such as the use of systemic hypothermia, older generation oxygenators and limited use of the internal thoracic artery as a conduit. This latter aspect may particularly influence lung function due to the potential contribution of injury to the phrenic nerve from dissection and pleural breach.
The aim of our study was to determine perioperative characteristics that predict atelectasis in patients who have undergone CABG and to determine the clinical outcomes related to the presence and/or severity of postoperative atelectasis. We hypothesised that atelectasis is more common with pleural breach and topical myocardial cooling with cold slush and that the degree of atelectasis on the initial x-ray on admission to the ICU is a predictor of respiratory dysfunction as determined by measures of oxygenation and length of ventilation.
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Ethics
Our tertiary care cardiac centre has approval from its institutional research ethics board to anonymously publish data that are prospectively collected before and after coronary artery bypass grafting. As such, individual patient consent was waived.
We retrospectively analysed prospectively collected data from the Peri-Operative Database Unit to identify patients undergoing CABG with bilateral internal thoracic artery (BITA) harvest. Between May 2, 2006 and October 23, 2012, 9166 patients
Results
A total of 565 patients were included in the study. Interobserver reliability for atelectasis grade was greater on the left (kappa=0.75) as compared to the right (kappa=0.51). Eighty-nine of 565 patients (15.8%) had Grade 2/3 atelectasis on the Day 0 chest radiograph. Patient and perioperative characteristics of those with and without Grade 2/3 atelectasis are listed in Table 1. Patients who developed Grade 2/3 atelectasis had a greater incidence of NYHA Class III or IV heart failure (p=0.002),
Discussion
The radiologic finding of severe (Grade 2/3) atelectasis after BITA grafting is relatively common, occurring in up to 16% of all patients on admission after CABG surgery. Factors associated with the development of atelectasis included advanced NYHA class, diabetes and increased CPB time. There was no relationship between the use of slush for topical cooling and the development of atelectasis. Severe atelectasis on the right was associated with a significant decrease in the pO2 and the PF ratio.
Conclusions
This study has demonstrated that severe atelectasis after BITA harvest has a left-sided predominance, however right-sided atelectasis, when present, is associated with greater changes in oxygenation. Topical slush, pleural breach and direct phrenic damage were not determined to be factors in the development of early atelectasis after cardiac surgery. Clinical trials are warranted to test strategies that may prevent perioperative atelectasis and to determine if this improvement is associated
Acknowledgements
We would like to acknowledge Subhapradha Anand MD (SA) and Abdullah Al Jebreen MD (AAJ) for their contribution to chest radiographic interpretation.
This original research has received no external financial support.
References (12)
- et al.
Phrenic nerve function and its relationship to atelectasis after coronary artery bypass surgery
Chest.
(1988) - et al.
The routine use of positive end-expiratory pressure after open heart surgery
Chest.
(1979) - et al.
Phrenic nerve injury during cardiac surgery: mechanisms, management and prevention
Heart, Lung and Circulation
(2013) - et al.
Postoperative chest radiographic changes after on- and off-pump coronary surgery
Clin Radiol.
(2005) - et al.
The effect of different lung-protective strategies in patients during cardiopulmonary bypass: a meta-analysis and semiquantitative review of randomized trials
J Cardiothorac Vasc Anesth.
(2012) - et al.
A new system for assessing atelectasis on chest x-ray after sternotomy for cardiac surgery
Medical Imaging and Radiology
(2014)