Assessment of Pericardium Volume by the Stroke Volume Variation in Patients with Off-Pump Cardiac Surgery

Objective: SVV is derived from the cardiopulmonary interaction, which is used to predict the responsiveness of cardiac preload guiding fluid therapy in patients under general anesthesia in non-opened chest surgery. From a clinical point of view, it is important to know how well SVV reflects preload and fluid responsiveness during cardiac surgery. This study was undertaken to assess the accuracy and reliability of SVV derived from the FloTrac/Vigileo system in monitoring changes in blood volume in patients undergoing off-pump coronary artery bypass grafting (OPCABG) under general anesthesia. Methods: After approval from the ethics committee and obtaining the permission of the patients, twenty-nine patients, ASA II-III and NYHA II-III, aged 44 77 yr, undergoing elective off-pump coronary artery bypass grafting, were randomly divided into 2 groups: the control group (group C, n = 8) and volume expansion group (group V, n = 21). After patients entered the operating room, veins were put in line, ECG, HR, SpO2, and PETCO2 were continuously monitored. Left radial arterial and right internal jugular vein catheters were inserted under local anesthesia. The FloTrac/Vigileo system was connected and MAP, CO, CI, SVV, SV, SVI, SVR, SVRI, CVP were continuously monitored. BIS values were kept at 45% 55.6% hydroxyethyl starch 130/0.4 sodium chloride solution 7 ml/kg was intravenously infused after completion of sternotomy and pericardiotomy at a rate of 0.25 ml/kg/min in group V. MAP, HR, CVP, systemic vascular resistance (SVR), SVV, and stroke volume index (SVI) were determined 10 min before (T1) and after the infusion of finished (T2), and the change rate (ΔHR, ΔMAP, ΔCVP, ΔSVR, ΔSVV, ΔSVI) was calculated. Sodium chloride injection 3 ml/kg was infused in group C. Results: CVP, SVI, CO and CI were increased after volume expansion, SVRI and SVV significantly decreased in group V(P < 0.01), while MAP and HR were not changed. Changes in HR(r = –0.737, P < 0.05) and SVR(r = –0.480, P < 0.05) were significantly correlated to changes in SVI, but there was no correlation between ΔCVP, ΔMAP, ΔSVV and ΔSVI. SVV(r = 0.640, P < 0.01) and HR(r = 0.591, P < 0.01) before volume expansion were correlated to changes in SVI,but no correlation was found between MAP, SVR, CVP and changes in SVI. Analysis of results of the receiver operating characteristic (ROC) curve showed that when the change rate of SVI ≥ 25% was used as the criteria for assessment of the changes in blood volume, the diagnostic threshold of SVV was 8.8%. When SVV ≥ 8.8%, the sensitivity and specificity of blood volume monitoring were 52.6% and 100% respectively. Conclusion: SVV derived from the FloTrac/Vigileo system cannot accurately monitor changes in fluid responsiveness in patients undergoing off-pump coronary artery bypass grafting under general anesthesia, though it is better than CVP and MAP.