Successful Prolonged Extracorporeal Perfusion and Replantation of Free Rectus Abdominis Flaps in a Porcine Model

Purpose:

Extracorporeal perfusion (ECP) aims to reduce ischemia-reperfusion injury and thereby prolong tissue preservation time. Safe prolongation of ischemia time will benefit multiple surgical procedures, e.g. multi-trauma surgery or VCA transplantation. Although currently available results on ECP of free flaps and extremities are promising, long-term perfusion of free muscle flaps is scarcely examined. The aim of this research was to evaluate long-term ECP and replantation of free rectus abdominis flaps and compare results to short static cold storage (CS). 

Materials and methods:

Unilateral free rectus abdominis flaps were harvested from 14 female Dutch landrace pigs (weight 63-84kg), followed by a 150cc passive flush of heparin-saline solution. Flaps were preserved in accordance to one of the following groups: 1) cold storage at 4⁰C for 4hr (n=4), 2) 18hr oxygenated continuous midthermic perfusion with Histidine-Tryptophan-Ketoglutarate (HTK) solution (n=5) or 3) 18hr oxygenated continuous midthermic perfusion with University of Wisconsin (UW) solution (n=5). After preservation, flaps were replanted to their original vascular pedicle and observed for 12 hours.

Results:

A total of 14 flaps was included in this study. The mean off-pedicle period in the CS-group was 5.4hr, compared to 19.2 and 19.1hr in UW resp. HTK-perfusion groups. Twelve flaps had uneventful post-replantation microsurgical controls and showed complete and homogenous perfusion on ICG-fluorescence angiography. One flap had acute arterial failure at 11.8hr post-replantation (UW-group) and one flap at 8hr post-replantation (HTK-group). A successful salvage procedure was performed for the latter after which controls and ICG-angiography patterns turned normal again.
Mean creatinine-kinase increase was higher in perfused groups (UW 48,571 U/L, HTK 32,014 U/L) compared to CS (9,494 U/L). However, mean venous lactate was lowest in UW-perfused flaps (0.68mmol/L), compared to CS-flaps (0.81mmol/L) and HTK-perfused flaps (0.86mmol/L). Mean weight increase was highest in HTK-flaps (114gr; 39%), followed by UW-flaps (72gr; 24%) and CS-flaps (50gr; 17%). Systemic cytokine levels (IL-1, IL-6 and TNF-) and histological evaluation (H&E, TUNEL) and qRT-PCR on muscle biopsies are currently under evaluation.

Conclusions:

All flaps were successfully perfused for 18 hours. Although CK increase was higher in the perfused flaps, post-replantation microsurgical controls and perfusion patterns were normal in all but two flaps. Lactate levels and weight increase were lower in UW-perfused flaps compared to HTK-perfused flaps. Upcoming results will give more insight into underlying cellular processes and flap survival rate. Overall, extracorporeal perfusion might be a promising solution for free flap preservation, with a more than four-fold lengthening of maximum ischemia time. The extra time will benefit multiple surgical fields, for instance vascularised composite allograft transplantation or multi-trauma surgery.