Efficacy of Stroke Volume Variation-guided Fluid Management of Patients undergoing Off-pump Coronary Artery Bypass Grafting: An Observational Comparative Study between Open and Closed Chest

Abstract

Introduction: Functional haemodynamic monitoring using dynamic parameter such as Stroke Volume Variation (SVV), based on pulse contour analysis, helps in predicting fluid responsiveness in off pump Coronary Artery Bypass Grafting (CABG) surgery. This allows adequate volume replacement to achieve optimal cardiac performance. Aim: To evaluate the efficacy of SVV in predicting volume responsiveness and effect on haemodynamic variable in patients undergoing off pump CABG in both closed and open chest. Materials and Methods: This single-centre, non randomised observational study was conducted at a tertiary medical college and hospital (LokmanyaTilak Municipal Medical College and General Hospital) Mumbai, Maharashtra, India, from December 2016 to December 2018. A total of 34 patients undergoing elective off pump CABG were included. Haemodynamic measurements Stroke Volume (SV), Cardiac Output (CO), Cardiac Index (CI), and SVV, were recorded with the transducer positioned at the level of midaxillary line. If the SVV was equal to or higher than 12, 100 mL fluid aliquot was given to patients. Endpoints for fluid aliquots was increase in CO by 15%, decrease in SVV of less than 12 or an increase Central Venous Pressure (CVP) upto 15 millimeter of mercury (mmHg). Number of times SVV above 12 during the procedure was recorded. SVV was considered as fluid responsive “if there was an increase in SV by 5%”. Statistical analysis was done using Student’s t-test (two tailed, dependent) on continuous parameters. The p-value <0.05, was considered significant. Results: Out of 103 events of rise in SVV, 65 (63.1%) occurred when chest was open and 38 (36.9%) while chest was closed. The SVV-guided fluid response was 76.3% in closed chest and 75.4% in open chest and there was no significant difference. (p-value=0.91). There was a significant increase in SV (p-value<0.01), CO (p-value=0.04), and significant decrease in SVV (p-value<0.01) and heart rate (p-value<0.01) after fluid loading in the responsive group when compared with non responsive group. There was no statistically significant difference between percentage change in SV, CO, CI, SBP, DBP, MAP and CVP between closed and open chest conditions after fluid replacement. Conclusion: SVV is not affected by open or closed chest conditions in mechanically ventilated patients undergoing CABG and can be used as a guide for fluid replacement. Weather open or closed chest conditions, few patients do not respond to fluid replacement when SVV are more than 12 by an increase in SV, cardiac output or CI, the cause of which remains to be determined.