Fifty-nine patients gave informed consent to take part in this study. Three patients could not be studied due to changes in surgical planning, and three patients had a low imaging quality (stitching artefacts) insufficient for 3D volumetry. Fifty-three patients (44 male and 9 female) were included into the final analysis.
The median age of the patients was 64 years (IQR 55 to 75) having a median EuroSCORE II of 2.9 % (IQR 1.9 to 7.5). Further demographic data as weight, height, body-surface-area, body-mass-index (BMI), preoperative laboratory values (creatinine, quick, total bilirubin) and the planned cardiac surgeries are given in table 1.
Anesthesia induction and ventilator settings
The median level of the PEEP was 5 mbar, the median Pinsp was 15 (IQR 14 to 17) to obtain a TV of 7 ml/kg (IQR 6 to 8). Anesthesia induction agents are given in table 1. No patient received noradrenaline prior to anesthesia. Median noradrenaline dose after anesthesia induction was 0.02µg/kg/min (IQR 0µg/kg/min to 0.05µg/kg/min). During anesthesia induction the patients received a median dose of 330ml (IQR 250ml to 440ml) of crystalloid fluids.
Hemodynamic variables are given in table 2. Patients experienced a significant reduction in heart rate (75 (SD 15) bpm to 66 (SD 14) bpm, p=<0.0001), systolic blood pressure (SBP; 136 (SD 24) mmHg to 112 (SD 19) mmHg; p<0.0001), diastolic blood pressure (DBP; 70 (IQR 60 to 80) mmHg to 57 (SD 11) mmHg; p<0.0001) and mean blood pressure (MBP; 91 (IQR 80 to 104) mmHg to 78 (SD 12) mmHg; p<0.0001).
A summary of the echocardiographic parameters is given in table 2. No significant change in the RVEDV, RVEDVI, RVESV, RVESVI, RVEF, right ventricular end-diastolic area indexed to body surface area (RVEDAI), RVFAC, 3D-RVLS-sw or right ventricular stroke volume was recorded (figure 2a).
After anesthesia induction and IPPV, the TAPSE was significantly reduced (18 (SD 4) mm to 16 (SD 4) mm; p=0.0013) (figure 2b). The TDITVs’ was also significantly reduced (13.2 cm/s (IQR 12 to 15.9) to 11.8 cm/s (IQR 10.1 to 13.3), p<0.0001). 3D-RVLS-fw also significantly decreased (-22.9 (SD 6) % to -21.4 (SD 5.9) %, p=0.0366) (figure 2 c).
There was no significant correlation between the noradrenaline dose and the change in RVEF (r=0.106, p=0.4451), 3D-RVLS-fw (r=-0.17, p=0.2284), TAPSE (r=-0.073, p=0.6129) or TDITVs’ (r=0.07, p=0.6439).
Subgroup analysis: patients with normal or impaired RVEF
For a subgroup analysis, patients were grouped based on their baseline RVEF. A baseline RVEF above 35% was considered normal, a baseline RVEF below or equal to 35% was considered depressed. Fourty-one patients with a median age of 64 years (IQR 53 to 74) were categorized into the group with a normal RVEF, twelve patients with a median age of 72 (IWR 63 to 77) were categorized into the group with depressed RVEF.
In both groups HR and MAP were significantly lower after anesthesia induction compared to the baseline values. RVEDV did not significantly change in either of the groups. In the group with a normal RVEF, all parameters reflecting RV function (RVEF, TAPSE, TDITVs’ and 3D-RVLS-fw) worsened significantly (table 3). The group with the depressed RVEF at baseline did not show a significant change of the RV functional parameters.
The ICC for the intra-observer reliability for the RVEDV was 0.924 (95% CI: 0.741 – 0.980), RVESV 0.847 (95% CI: 0.524 – 0.959), RVEF 0.984 (95% CI: 0.942 – 0.996), 3D-RVLS-fw 0.927 (95% CI: 0.749 – 0.981) and RVFAC 0.669 (95% CI: 0.143 – 0.905). The ICC for the inter-observer reliability for the RVEDV was 0.927 (95% CI: 0.737 – 0.981), RVESV 0.957 (95% CI: 0.839 – 0.989), RVEF 0.846 (95% CI: 0.497 – 0.959), 3D-RVLS-fw 0.834 (95% CI: 0.466 – 0.956) and RVFAC 0.662 (95% CI: 0.052 – 0.09.12).