Extracorporeal perfusion - reduced to a one-way infusion

Tissue Viability of Free Flaps after Extracorporeal Perfusion Using a Modified Hydroxyethyl Starch Solution

BACKGROUND

In free flap surgery, tissue is stored under hypothermic ischemia. Extracorporeal perfusion (EP) has the potential to extend storage time and the tissue's perspective of survival. In the present study, the aim is to improve a recently established, simplified extracorporeal perfusion system.

METHODS

Porcine musculus rectus abdominis were stored under different conditions. One group was perfused continuously with a simplified one-way perfusion system for six hours, while the other received only a single flush but no further treatment. A modified hydroxyethyl starch solution was used as a perfusion and flushing solution. Vitality, functionality, and metabolic activity of both groups were analyzed.

RESULTS

Perfused muscles, in contrast to the ischemically stored ones, showed no loss of vitality and significantly less functionality loss, confirming the superiority of storage under continuous perfusion over ischemic storage. Furthermore, in comparison to a previous study, the results were improved even further by using a modified hydroxyethyl starch solution.

CONCLUSION

The use of EP has major benefits compared to the clinical standard static storage at room temperature. Continuous perfusion not only maintains the oxygen and nutrient supply but also removes toxic metabolites formed due to inadequate storage conditions.

Transplantation of a latissimus dorsi flap after nearly 6 hr of extracorporal perfusion: A case report

Prolonged ischemia of tissues inevitably leads to their necrosis. This is especially relevant in the case of transplantation or replantation. In such situations, reperfusion in a timely manner might not be possible due to transportation times or other unforeseen complications. Therefore, a readily available and simple method to oxygenate the tissue and thus widen the time frame to reperfusion seems desirable. Here, we present the case of extracorporal perfusion of a latissimus dorsi (LD) flap that was successfully transplanted after nearly 6 hr of ischemia. A 41-year-old patient suffered multiple injuries including complete severance of the popliteal artery requiring emergency bypass. After stabilization of the patient and subsequent debridement, a LD flap was performed for soft tissue coverage. However, there was an acute occlusion of the bypass during flap inset. To salvage the free flap, a one-way extracorporal perfusion of the flap with heparinized isotonic saline solution was performed for a total of 5 hr and 47 min. The flap survived with minimal tip necrosis. This case report describes the application of a simple extracorporal perfusion technique for salvage of a free flap over a prolonged ischemia time and discusses the relevant literature. Due to its ease and quickness of application as well as ubiquitous availability, it might serve as a valuable tool in cases of acute problems with the recipient vessels or other incidents where several hours of ischemia time are to be anticipated.

Effects of topical negative pressure therapy on perfusion and microcirculation of human skin

BACKGROUND

Topical negative pressure wound therapy (TNPWT) is one of the most frequently used techniques in wound treatment. But some of the underlying mechanisms still remain unclear. One possible explanation is an improved microcirculation by TNPWT.

OBJECTIVE

This study investigated the influence of TNPWT on microcirculation on intact skin in real-time.

METHODS

In healthy individuals, we performed a combined tissue - laser/photo - spectrometry technique to monitor changes of 4 different microcirculation parameters in real-time: The local blood flow, the capillary-venous oxygen saturation, the blood flow velocity and the relative amount of hemoglobin. We compared these parameters using two different protocols: a continuously (VAC ON 60/OFF 60) and discontinuously (VAC ON 30/OFF 60/ON 5) application.

RESULTS

Our results demonstrate a significant increase of all four measured parameters during the active TNPWT and the pressure free period. The comparison of two different protocols shows an advantage of the examined parameters using a discontinuous TNPWT application.

CONCLUSIONS

Our study demonstrated the changes of the microvascular tissue perfusion in intact human skin under the conditions of negative pressure and may thereby offer a broader understanding of mechanisms underlying the TNPWT.

Ex-vivo perfusion as a successful strategy for reduction of ischemia-reperfusion injury in prolonged muscle flap preservation - A gene expression study

INTRODUCTION

With the introduction of vascularized composite allotransplantation (VCA) as new surgical technique, the need arose for strategies that could safely prolong graft preservation. Ex-vivo machine perfusion is a promising technique and is currently applied in solid organ transplantation. There is still limited evidence in the field of VCA and free flap transplantation. This gene expression study aimed to assess the degree of ischemia-reperfusion (IR) injury after preservation and replantation of free muscle flaps in a porcine model.

MATERIALS AND METHODS

A microarray analysis was first conducted on muscle flaps preserved by ex-vivo perfusion versus cold storage, to select genes of interest for further investigation. The expression of these selected genes was then examined in a muscle flap replantation model after 18 hour ex-vivo perfusion (n = 14) using qRT-PCR. Two preservation solutions were compared to static cold storage: University of Wisconsin-mp (n = 5) and Histidine-Tryptophan-Ketoglutarate solution (n = 5).

RESULTS

A selection of 8 genes was made based on micro-array results: Tumor necrosis factor receptor superfamily member 10-A like, Regulator of G-protein signaling 2, Nuclear factor kappa beta inhibitor zeta, Interleukin-1 beta, Fibroblast growth factor 6 and DNA damage-inducible transcript 4, Hypoxia-inducible factor 1-alpha and Caspase-3. The muscle flap replantation experiment compared their expression patterns before and after preservation and replantation and showed overall comparable gene expression between the preservation groups.

CONCLUSIONS

The expression of genes related to ischemia, apoptosis and inflammation was comparable between the ex-vivo perfusion and static cold storage groups. These results suggest that ex-vivo perfusion might be a promising technique for 18 hour muscle preservation in terms of decreasing ischemia-reperfusion injury.