Effects of hyperoxia on systolic and diastolic function assessed by strain analysis in patients with coronary artery disease during general anaesthesia

BACKGROUND Cardiac complications are a source of perioperative morbidity, but the impact of perioperative supplemental oxygen -a coronary vasoconstrictor- on the myocardium remains unclear. OBJECTIVE To determine the impact of supplemental oxygen on myocardial function in patients with coronary artery disease during general anaesthesia by 2D echocardiography. We hypothesised that 2D global systolic circumferential strain (GCS) worsens under hyperoxia. DESIGN This is a secondary analysis of a prospective randomised cross-over trial. SETTING Single tertiary centre. PATIENTS Datasets from 99 patients undergoing elective coronary artery bypass surgery were analysed. INTERVENTION During general anaesthesia, patients were exposed to normoxaemic and hyperoxic inspired oxygen fractions. MAIN OUTCOME MEASURES Transoesophageal echocardiography cines were analysed in each state primarily for changes in 2D GCS. Secondarily systolic parameters such as 2D global systolic longitudinal strain (GLS), ejection fraction (EF) and diastolic parameters were analysed. RESULTS GCS worsened under hyperoxia compared with normoxaemia (25.2% (26.6 to 23.8) vs. 26.1% (27.5 to 24.7), P = 0.041), whereas GLS and ejection fraction remained unchanged (−12.4% vs. 12.7%, P = 0.307 and 41% vs. 42%, P = 0.190, respectively). Although mean GCS declined, individual responses varied: 30% of patients showed a relevant worsening during hyperoxia and 14% an improvement ( P < 0.001). Strain responses to hyperoxia were heterogeneous and depended on baseline systolic function. Notably, patients with a greater count of myocardial segments associated with stenotic coronary lesions demonstrated improved GCS during hyperoxia ( r = −0.26, P = 0.009). Measures of global and regional diastolic function also deteriorated under hyperoxia. CONCLUSIONS In patients with coronary artery disease, mean GCS deteriorated with hyperoxia under general anaesthesia. Furthermore, circumferential strain based diastolic markers delineated a global and regional effect of hyperoxia on myocardial function. In the light of heterogeneous changes in systolic function with hyperoxia in individual patients, EF, GLS and GCS at normoxaemia may guide the utility of hyperoxia in patients with coronary artery disease undergoing general anaesthesia and as such may help to titrate supplemental oxygen in the individual patient. TRIAL REGISTRATION NCT04424433.