Free Flap Perfusion in Microvascular Head and Neck Reconstruction: Influence of the Number of Ischemia Intervals and Ischemia Duration-A Retrospective Study

Abstract

Background: In microvascular head and neck reconstruction, ischemia of the free flap tissue is inevitable during microsurgical anastomosis and may affect microvascular free flap perfusion, which is a prerequisite for flap viability and a parameter commonly used for flap monitoring. The aim of this study was to investigate the influence of the number of ischemia intervals and ischemia duration on flap perfusion.

Methods: Intraoperative and postoperative flap blood flow, hemoglobin concentration, and hemoglobin oxygen saturation at 2 and 8 mm tissue depths, as measured with the O2C tissue oxygen analysis system, were retrospectively analyzed for 330 patients who underwent microvascular head and neck reconstruction between 2011 and 2020. Perfusion values were compared between patients without (control patients) and with a second ischemia interval (early or late) and examined with regard to ischemia duration.

Results: Intraoperative and postoperative flap blood flow at 8 mm tissue depth were lower in patients with early second ischemia intervals than in control patients [102.0 arbitrary units (AU) vs 122.0 AU, P = .030; 107.0 AU vs 128.0 AU, P = .023]. Both differences persisted in multivariable analysis. Intraoperative and postoperative flap blood flow at 8 mm tissue depth correlated weakly negatively with ischemia duration in control patients (r = -.145, P = .020; r = -.124, P = .048). Both associations did not persist in multivariable analysis.

Conclusions: The observed decrease in microvascular flap blood flow after early second ischemia intervals may reflect ischemia-related vascular flap tissue damage and should be considered as a confounding variable in flap perfusion monitoring.

Keywords: blood flow; free tissue flap; ischemia; microsurgery; oxygen saturation; perfusion.

Graphical abstract

Figure 1.

Study groups. Patients were categorized into groups according to the presence of a second ischemia interval. Group 1 (Control): patients without a second ischemia interval; group 2: patients with an early second ischemia interval (cases in which the vessel clamp on the arterial recipient vessel was temporarily released after arterial/before venous anastomosis to verify the patency of the arterial anastomosis by assessing venous outflow); group 3: patients with a late second ischemia interval (cases in which intraoperative anastomosis revision was performed with additional temporary clamping of the arterial recipient vessel after release of flap perfusion).

Figure 2.

Intraoperative blood flow. Box plot for intraoperative blood flow [AU; separately shown for 8 mm tissue depth (left) and 2 mm tissue depth (right)] for patients without a second ischemia interval (Control) and patients with a second ischemia interval (SI); subdivided into patients with an early second ischemia interval (early SI) and patients with a late second ischemia interval (late SI); P values corresponding to testing for differences between groups (SI, early SI, and late SI vs Control) with Mann-Whitney test; significant P values are bold [*P < .05 on adjustment for ischemia duration, flap type, mean arterial blood pressure (mmHg), and administered catecholamine dose (µg/minute per kg) in multiple regression analysis]. Abbreviation: AU, arbitrary units.

Figure 3.

Postoperative blood flow. Box plot for postoperative blood flow [AU; separately shown for 8 mm tissue depth (left) and 2 mm tissue depth (right)] for patients without a second ischemia interval (Control) and patients with a second ischemia interval (SI); subdivided into patients with an early second ischemia interval (early SI) and patients with a late second ischemia interval (late SI); P values corresponding to testing for differences between groups (SI, early SI, and late SI vs Control) with Mann-Whitney test; significant P values are bold [*P < .05 on adjustment for ischemia duration, flap type, mean arterial blood pressure (mmHg) and administered catecholamine dose (µg/minute per kg) in multiple regression analysis]. Abbreviation: AU, arbitrary units.