Standardized blood volume changes monitored by capnodynamic hemodynamic variables: An experimental comparative study in pigs

BACKGROUND

The capnodynamic method, based on Volumetric capnography and differential Fick mathematics, assess cardiac output in mechanically ventilated subjects. Capnodynamic and established hemodynamic monitoring parameters' capability to depict alterations in blood volume were investigated in a model of standardized hemorrhage, followed by crystalloid and blood transfusion.

METHODS

Ten anesthetized piglets were subjected to controlled hemorrhage (450 mL), followed by isovolemic crystalloid bolus and blood re-transfusion. Intravascular blood volume, and all hemodynamic variables, were determined twice after each intervention. The investigated hemodynamic variables were: cardiac output and stroke volume for capnodynamics and pulse contour analysis, respectively, pulse pressure and stroke volume variability and mean arterial pressure. One-way ANOVA and Tukey's test for multiple comparisons were used to identify significant changes. Trending was assessed by correlation and concordance.

RESULT

Concordance against intravascular volume changes for capnodynamic cardiac output and stroke volume were 96 and 94%, with correlations r = .78 and .68, (p < .0001) with significant changes for 6 and 5 of the 6 measuring points, respectively. Mean arterial pressure and pulse pressure variation had a concordance of 85% and 87%, r = .67 (p < .0001) and r = -.45 (p < .0001), respectively, and both changed significantly for 3 of 6 measuring points. Pulse contour stroke volume variation, stroke volume and cardiac output, showed concordance and correlation of 76%, r = -.18 (p = .11), 63%, r = .28 (p = .01) and 50%, r = .31 (p = .007), respectively and significant change for 1, 1 and 0 of the measuring points, respectively.

CONCLUSION

Capnodynamic cardiac output and stroke volume did best depict the changes in intravascular blood volume. Pulse contour parameters did not follow volume changes in a reliable way.

Deep sedation vs femoral block anesthesia: beat-by-beat hemodynamic impact on TAVI procedure

BACKGROUND

In spite of the increased use of Trans-catheter Aortic Valve Implantation (TAVI) due to the better patient selection, well-trained operators and improved technology, the choice of the best anesthesia regimen remains an open question. In particular, it remains to be clarified whether deep sedation (DS) in spontaneous breathing or femoral local anesthesia (LA) is best.

OBJECTIVE

This study compared the hemodynamic variations determined by deep sedation (DS) with spontaneous breathing and local femoral anesthesia (LA) in 2 groups of patients submitted to TAVI with two different kinds of anesthesia, using a beat-by-beat pulse contour method (MostCare^®-UP).

METHODS

82 patients with severe aortic stenosis and similar baseline characteristics and indications underwent trans-femoral TAVI: 50 with LA and 32 with DS. All patients were submitted to minimally invasive hemodynamic monitoring. The following parameters were measured: pressure indexes: systolic, diastolic, mean (SysP, DiaP, MAP) and dicrotic (DicP) pressures; flow indexes: cardiac output (CO), stroke volume (SV); ventriculo-arterial coupling indexes (VAC): peripheral arterial elastance (Ea_P), systemic vascular resistance (SVR); cardiovascular system performance: cardiac cycle efficiency (CCE), dP/dt_{max_rad}.

RESULTS

The TAVI procedure was successful in 89% of patients (VARC-2 criteria) with no difference between the 2 groups. Anesthesia induction determined a higher decrease of pressures in DS than in LA (P<0.01) with no differences in CO. The VAC parameters (Ea_P, SVR) decreased (P<0.01) in DS with an improvement in CCE (P<0.001); these parameters did not change in LA. The post-TAVI flow and VAC parameters, especially Ea, increased (P<0.05) more significantly in the LA group than in the DS group (P<0.001). Using logistic regression, the occurrence of the post-TAVI aortic regurgitation was correctly associated with the pressure gradient MAP-DicP in 63% of the study population (P=0.033). This association was more effectively detected in the LA group (78%, P=0.011) with a ROC AUC=0.779, than the DS group.

CONCLUSION

The use of the pulse contour method to track the fast-hemodynamic changes during the TAVI procedure proved suitable for the aim. As expected, LA and DS induced different pre-TAVI hemodynamic conditions, which influenced the post-TAVI hemodynamic changes. The hemodynamic conditions induced by LA, enabled the occurrence of post-TAVI aortic regurgitation to be detected more effectively.