Advanced Hemodynamic Monitoring in Free Flap Surgery

Overview

Background: Anesthesia in free flap surgery is challenging. Monitoring of hemodynamic changes and their influence on the cardiovascular system in permanent feedback loops allow control, which is what anesthesiologists aim for to ensure an adequate blood flow and tissue oxygenation. The circulatory support and inferable volume administration are managed via heart rate (HR) and mean arterial pressure (MAP), but both parameters are influenced by variable components and are thus unfavorable for volume management. The aim of this study was to evaluate whether volume requirement may be assumable to additional monitoring parameters. Methods: 31 patients were enrolled prospectively. HR, MAP, central venous pressure and O2 saturation were comprehended based on the protocols. We expanded the data set by a permanent blinded intraoperative monitoring with registration of the Cardiac Index (CI) and Stroke Volume Variation (SVV) and semi-invasive pulse-contour analysis utilizing the Pro-AQT-Device.

We conducted a prospective cohort study in accordance with the WMA Declaration of Helsinki. Standard general anesthesia with intubation and administration of sufentanil, propofol and esmeron relaxant was performed in all patients undergoing primary free flap reconstruction in course of a head and neck tumor reconstruction. Hemodynamic monitoring measurement of cardiac index and the parameter stroke volume variation as surrogate for cardiac pre-load was performed using a Pro-AQT Monitor. Using an arterial catheter previously set by the Seldinger technique as part of the standard equipment, the mean, diastolic and systolic arterial pressure was measured as part of the standard monitoring as presented. This tube was previously deaerated and flushed with 2% NaCl and connected in series with a sensor, which passes over electric line signals to the Pro-AQT-Monitor®. Based on previously entered patient data and an analysis of the arterial pulse curve characteristics, a cardiac index (CI) start-value is determined by the system. The sampling of the arterial pressure characteristics is affected by a signal having a frequency of 250 Hz. The start value is the basis for the further determination of HI trend values. The arterial pulse contour is continuously tapped and analyzed and offset against the determined start value. To calculate the cardiac index, the PICCO®-pulse contour algorithm is applied. Every 12 seconds, a new measurement is performed and documented by the system. From the read logs ProAQT Monitor® the values of the CI, MAP, HR, stroke volume index (SVI), the stroke volume variation (SVV) and the systemic resistance index (SRI) were recorded at different measurement intervals throughout the operation. All parameters were evaluated for volume control in the course of the study.