Influence of noninvasive central blood pressure devices for afterload monitoring with aortic velocity-pressure Loop in anesthetized patients

摘要

Background Global afterload angle (GALA) is a parameter derived from velocity-pressure loop (VP Loop), for continuous assessment of cardiac afterload in the operating room. It has been validated with invasive measure of central pressure. The aim of this study was to evaluate the feasibility of noninvasive VP Loop obtained with central pressure measured with two different noninvasive tonometers. Methods A prospective, observational, monocentric study was conducted in 51 patients under general anesthesia. Invasive central pressure (cP(INV)) was measured with a fulfilled intravascular catheter, and noninvasive central pressure signals were obtained with two applanation tonometry devices: radial artery tonometry (cP(SHYG): Sphygmocor tonometer) and carotid tonometry (cP(COMP): Complior tonometer). Three VP Loops were built: VP Loop(INV), VP Loop(SPHYG)and VP Loop(COMP). Patients were separated according to cardiovascular risk factors. Results In the 51 patients under general anesthesia, cP(SHYG)was adequately obtained in 48 patients (89%) but, compared to cP(INV), SBP was underestimated (-4 +/- 6 mmHg,P< 0.0001), augmentation index (AIX(SPHYG)) and a GALA(SPHYG)were overestimated (+13 +/- 19%,P= 0.0077 and +4 +/- 8 degrees,P= 0.0024, respectively) with large limit of agreement (LOA) (-21 to 47% and -13 to 21 degrees for AIX(SPHYG)and GALA(SPHYG), respectively). With the Complior, the failure rate of measurement for cP(COMP)was 41%. SBP was similar (3 +/- 17 mmHg,P= 0.32), AIX(COMP)was underestimated (-11 +/- 19%,P= 0.0046) and GALA(COMP)was similar but with large LOA (-50 to 26% and -20 to 18 degrees for AIX(COMP)and GALA(COMP), respectively). Conclusion In anesthetized patient, the reliability of noninvasive central pressure monitoring by tonometry seems too limited to monitor cardiac afterload with VP Loop.