Original Article
Clinical Correlation of Early Atelectasis after Bilateral Internal Thoracic Artery Harvest for Coronary Artery Bypass Grafting

https://doi.org/10.1016/j.hlc.2015.11.004Get rights and content

Background

Atelectasis is a significant complication after cardiac surgery. The current study was designed to assess the significance of atelectasis after bilateral internal thoracic artery (BITA) harvest.

Methods

The ICU admission chest x-ray of 565 patients undergoing BITA was reviewed. Linear regression modelling was used to assess the relationship between atelectasis and oxygenation as well as patient variables to length of ventilation and length of stay in the Intensive Care Unit (ICU).

Results

Eighty-nine patients (15.8%) had Grade 2/3 atelectasis which was significantly more common on the left as compared to the right (left 0.149 95% CI [0.119-0.178], right 0.027 95% CI [0.013-0.040], p<0.001). Grade 2/3 atelectasis on the right was associated with a significant drop in the pO2 (p=0.001) and the per cent O2-fractional O2 (PF) ratio (p=0.002). Factors associated with increased ventilation time included presence of Grade 2/3 atelectasis (p=0.001) and peripheral vascular disease (PVD) (p<0.001), both of which were predictors of prolonged ICU length of stay (p=0.002 and p<0.001 respectively).

Conclusions

Early atelectasis is related to impaired oxygenation, prolonged ventilation and prolonged ICU stay. Future research should focus on strategies to minimise atelectasis and to determine if these changes translate into better patient outcomes.

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.

Section snippets

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.

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