Tolerance of prefabricated skin flaps to ischaemia and reperfusion: Experimental study

Systematic review of pathologic markers in skin ischemia with and without reperfusion injury in microsurgical reconstruction: Biomarker alterations precede histological structure changes

BACKGROUND

Ischemia and ischemia-reperfusion injury contribute to partial or complete flap necrosis. Traditionally, skin histology has been used to evaluate morphological and structural changes, however histology does not detect early changes. We hypothesize that morphological and structural skin changes in response to ischemia and IRI occur late, and modification of gene and protein expression are the earliest changes in ischemia and IRI.

METHODS

A systematic review was performed in accordance with PRISMA guidelines. Studies reporting skin histology or gene/protein expression changes following ischemia with or without reperfusion injury published between 2002 and 2022 were included. The primary outcomes were descriptive and semi-quantitative histological structural changes, leukocyte infiltration, edema, vessel density; secondary outcomes were quantitative gene and protein expression intensity (PCR and western blot). Model type, experimental intervention, ischemia method and duration, reperfusion duration, biopsy location and time point were collected.

RESULTS

One hundred and one articles were included. Hematoxylin and eosin (H&E) showed inflammatory infiltration in early responses (12-24 h), with structural modifications (3-14 days) and neovascularization (5-14 days) as delayed responses. Immunohistochemistry (IHC) identified angiogenesis (CD31, CD34), apoptosis (TUNEL, caspase-3, Bax/Bcl-2), and protein localization (NF-κB). Gene (PCR) and protein expression (western blot) detected inflammation and apoptosis; endoplasmic reticulum stress/oxidative stress and hypoxia; and neovascularization. The most common markers were TNF-α, IL-6 and IL-1β (inflammation), caspase-3 (apoptosis), VEGF (neovascularization), and HIF-1α (hypoxia).

CONCLUSION

There is no consensus or standard for reporting skin injury during ischemia and IRI. H&E histology is most frequently performed but is primarily descriptive and lacks sensitivity for early skin injury. Immunohistochemistry and gene/protein expression reveal immediate and quantitative cellular responses to skin ischemia and IRI. Future research is needed towards a universally-accepted skin injury scoring system.

Augmentation of Perforator Flap Blood Supply with Vascular Supercharge or Flap Prefabrication: Evaluation in a Rat Model

BACKGROUND

Vascular supercharge and flap prefabrication are two surgical maneuvers to improve flap blood supply. Although these techniques have been studied intensively, few studies have focused on the differences between supercharge and prefabricated flaps regarding their flap survival areas, vasculatures, and hemodynamics.

METHODS

In this study, 21 male Sprague-Dawley rats were divided into three groups as follows: group A, single perforator flap; group B, supercharge flap; and group C, prefabricated flap. Flap survival was measured 1 week after flap elevation. Indocyanine green angiography was applied to visualize flap vascularity and to analyze flap hemodynamics. Von Willebrand factor immunohistochemical staining was applied to assess the number of microvessels in the choke zone of the abdominal wall.

RESULTS

The flap survival areas were expanded significantly in the arteriovenous supercharge group and the vascular bundle prefabricated group compared with that in the single-perforator group (81.34 ± 8.12 percent and 75.51 ± 8.08 percent versus 46.27 ± 10.01 percent, respectively; p < 0.05). Hemodynamic analysis suggested that although a significant increase in arterial infusion could be achieved with flap prefabrication, the venous effusion of the prefabricated flap was the worst among the three groups, indicating greater susceptibility to compromised venous return. Active neovascularization was confirmed by an increased number of microvessels in group C. Specifically, the dilatation of choke vessels and the newly formed vessels of the prefabricated pedicle could be appreciated by indocyanine green angiographic mapping.

CONCLUSIONS

Both vascular supercharge and flap prefabrication can augment the blood supply of the perforator flap but by means of different mechanisms. Because a supercharge flap is less susceptible to venous compromise, it is suggested to first consider the use of vascular supercharging when feasible.

The Effect of Botulinum Toxin A on Ischemia-Reperfusion Injury in a Rat Model

Introduction

While studies using various materials to overcome ischemia-reperfusion (IR) injury are becoming increasingly common, studies on the effects of botulinum toxin A (BoTA) on IR injury in musculocutaneous flaps are still limited. The purpose of this study was to examine our hypotheses that BoTA provide protection of musculocutaneous flap from ischemia-reperfusion injury.

Method

Five days after pretreatment injection (BoTA versus normal saline), a right superior musculocutaneous flap (6 × 1.5 cm in size) was made. Ischemia was created by a tourniquet strictly wrapping the pedicle containing skin and muscle for 8 h. After ischemia, the tourniquet was cut, and the musculocutaneous flap was reperfused.

Results

The overall survival percentage of flap after 8 h of pedicle clamping followed by reperfusion was 87.32 ± 3.67% in the control group versus 95.64 ± 3.25% in the BoTA group (p < 0.001). The BoTA group had higher expression of CD34, HIF-1α, VEGF, and NF-kB comparing to control group in qRT-PCR analysis.

Conclusions

In this study, we found that local BoTA preconditioning yielded significant protection against IR injury in a rat musculocutaneous flap model.