The effects of anesthesia induction and positive pressure ventilation on right-ventricular function: An echocardiography-based prospective observational study

Background: General anesthesia induction with the initiation of positive pressure ventilation creates a vulnerable phase for patients. The impact of positive intrathoracic pressure on cardiac performance has been studied but remains controversial. 3D echocardiography is a valid and MRI-validated bed-side tool to evaluate the right ventricle (RV). The aim of this study was to assess the impact of anesthesia induction (using midazolam, sufentanil and rocuronium, followed by sevo�urane) with positive pressure ventilation (PEEP 5, tidal volume 6 – 8 ml/kg) on 2D and 3D echocardiography derived parameters of RV function. Methods: A prospective observational study on �fty-three patients undergoing elective cardiac surgery in a tertiary care university hospital was designed. Transthoracic echocardiography exams were performed before and immediately after anesthesia induction and were recorded together with hemodynamic parameters and ventilator settings. Results: After anesthesia induction TAPSE (mean difference -1.6mm (95% CI -2.6mm to -0.7mm; p=0.0013) as well as the Tissue Doppler derived tricuspid annulus peak velocity (TDITVs’) were signi�cantly reduced (mean difference -1.9% (95% CI: -2.6 to -1.2; p<0.0001), but global right ventricular ejection fraction (RVEF; p=0.1607) and right ventricular stroke volume (RVSV; p=0.1838) did not change. Conclusions: This data shows a preserved right ventricular ejection fraction and right ventricular stroke volume after anesthesia induction and initiation of positive pressure ventilation. However, the baso-apical right ventricular function is signi�cantly reduced. Larger studies are needed in order to determine the clinical impact of these �ndings especially in patients presenting with impaired right ventricular function before anesthesia induction. were applied intravenously (i.v.) for anesthesia induction and endotracheal intubation and were followed by sevo�urane (up to 1 minimal alveolar concentration (MAC)) for anesthesia maintenance. As per institutional standard, intravenous volume was administered restrictively using isotonic crystalloid solutions with a maximum of 15 ml/kg prior to initiation of cardiopulmonary bypass in all patients. A target mean arterial blood pressure (MBP) of > 65 mmHg was maintained during anesthesia induction using a continuous i.v. infusion of noradrenaline as a �rst line agent to counteract hypotension based on the clinical requirements. Pressure controlled positive pressure ventilation with a standardized PEEP of 5 cm H 2 O and a peak inspiratory pressure (Pinsp) to receive a tidal volume of 6-8ml/kg was initiated, and the inspiratory oxygen fraction was titrated to individual demands to maintain a SpO2 between 95-99%. End-tidal carbon dioxide levels were maintained between 35-37 mmHg by adjusting the ventilation frequency. All hemodynamic parameters were recorded during the echocardiography studies. a 2D transapical 4-chamber and 3D full volume acquisitions ventricle. The 3D full volume datasets were acquired using an ECG-gated 4 heart beats-technique with a short apnoeic phase maintaining PEEP. Hemodynamic parameters were allowed to stabilize prior to the TTE exam. Tricuspid annular plane systolic excursion (TAPSE) was measured in an apical 4-chamber view using M-mode on the lateral tricuspid annulus. Systolic apical movement velocity of the lateral tricuspid annulus (TDITVs’) was assessed using tissue Doppler imaging. All measurements were performed according to current ASE recommendations All 3D quanti�cations were performed o�ine. RV quanti�cation was performed on a independent by two echocardiographers blinded for each other’s results. For quanti�cation of the 3D datasets, software that had been validated against cardiac magnetic resonance imaging (CMRI) was used (Tomtec 4D RV-Function 2.0; Tomtec Imaging Systems After adjustment of the 3D image in pre-de�ned axes, this software uses a speckle tracking based technique to identify right ventricular endocardial borders to generate a dynamic model of the right ventricular endocardial surface (�gure 1). The RV end-diastolic (RVEDV) and end-systolic (RVESV) volumes were measured based on the generated RV model. RVEF was calculated [(RVEDV-RVESV)/RVEDV] x 100%. To compare individual RV sizes, volumes were indexed to the body-surface area (RVEDVI and RVESVI). right ventricular mechanics and novel 3D echocardiographic parameters of right ventricular function during anesthesia induction and initiation of positive pressure ventilation. Right ventricular volume, quanti�ed by the RVEDVI, and the RVEDAI did not change in our study. This is contrary to previously published results by Couture et al. that showed an increase in preload as measured by the RVEDA after anesthesia induction (34). PEEP and peak inspiratory pressure levels are not reported in the article of Couture et al. (34), thus making it di�cult to compare their �ndings to our results. A potential reason for the different observations could be the different approach for the volumetric quanti�cation, particularly the direct measurement of the RVEDVI in this study. The 3DE volumetric technique incorporates the whole right ventricle. This technique includes the right ventricular out�ow tract in the volume calculation and overcomes the use of a single imaging plane used by Couture et al. Foreshortened imaging planes in 2D echocardiography could be another potential reason for the different results. In our patients RVEF and stroke volume did not signi�cantly change. This �nding is supported by the data published by Pinsky et al. that showed no relevant change in ejection fraction during various PEEP levels (5). Our data demonstrate that the longitudinal function of the right ventricle, as measured by indices that assess the movement of the lateral tricuspid annulus, namely, TAPSE and TDITVs’, are signi�cantly reduced after anesthesia induction and IPPV. This con�rms the previous �ndings of Tousignant et al. that have shown a similar reduction in TAPSE (35). But contrary to our results they did not experience a change in TDITVs’ what could be due to the different patient population, the smaller number of included patients or different ventilator settings. The movement of the tricuspid annulus is not solely associated with right ventricular function and relies on the movement of the whole heart. Moreover, TAPSE has shown to be associated with left ventricular function 37). In addition, con�icting data exist about the lack of correlation of the TAPSE with cardiac MRI-derived RV ejection fraction (38, 39). Imaging of longitudinal myocardial deformation does not only rely on the movement of the tricuspid annulus and directly assesses the longitudinal myocardial contractility. Right ventricular strain imaging is considered to detect even subtle changes in myocardial contractility (40). In our patients we observed a signi�cant but small decrease in right ventricular free wall strain. In a subgroup analysis we can show that patients with a normal RVEF at baseline experienced a signi�cant decrease in the longitudinal myocardial contraction component accompanied by a small but signi�cant reduction in RVEF. right patient we fraction assessed 3DE decreased baseline but, stroke volume did not change.