Beneficial Effect of U-74389 G and Sildenafil in An Experimental Model of Flap Ischemia/Reperfusion Injury in Swine. Histological and Biochemical Evaluation of the Model

Use of Phosphodiesterase Inhibitors in the Postoperative Period of Skin Flaps: A Systematic Review

Ischemia-reperfusion injury can occur in several clinical conditions, and it has been widely studied in the context of skin flaps. Vascular distress results in an imbalance between the supply and demand of oxygen to living tissues, and the result of this process is tissue necrosis. Several drugs have been studied to reduce vascular distress of skin flaps and tissue loss.

Methods

The present study performed a systematic review of literature in the main databases (PubMed, Web of Science, LILACS, SciELO, and Cochrane), including articles published in the last 10 years.

Results

It was observed that phosphodiesterase inhibitors, mainly types III and V, have shown promising results in terms of vascularization of the postoperative skin flap, especially when started on the first postoperative day and maintained for 7 days.

Conclusion

New studies with different posology, duration of use, and new drugs are needed to better elucidate the use of this substance to optimize the circulation of skin flaps.

Saphenous Artery Perforator Flaps in Minipigs: Anatomical Study and a New Experimental Model

This study describes the anatomy of the saphenous artery (SA) perforators in minipigs and the development of a new animal model. First, the anatomic characteristics of the SA and perforators in minipigs were examined after latex-lead oxide perfusion. Subsequently, the right hind limbs of 10 minipigs were used to generate capillary perforator flaps (group A; utilizing the SA and 5.5 cm of deep fascia above the knee), while all perforators of the left hind limbs were reserved (group B). Four additional minipigs were used to evaluate SA perforator flaps with capillary perforators plus sarcolemma and a small amount of muscle (group C). Preoperative and postoperative CTA of both hind limbs confirmed that all perforators were ligated in groups A and C. The average length of the SA was 14.86 ± 0.76 mm. The diameters of the SA at initiation, the medial tibial condyle, and the medial malleolus were 1.73 ± 0.15 mm, 1.50 ± 0.12 mm, and 1.30 ± 0.13 mm, respectively. There were 7.09 ± 1.16 perforators per hind limb, with an average diameter of 0.40 ± 0.13 mm (range, 0.10-0.78 mm), and the majority (96.2%) had a diameter >0.2 mm. The survival rates of the flaps in groups A, B, and C were 32 ± 39%, 100%, and 60.2 ± 17%, respectively. The position of the SA in minipigs is constant, its diameter is relatively large, and it has many perforators, allowing it to be used as a reliable model of perforator flaps, including capillary perforator flaps.

Lazaroid U-74389G in liver ischemia-reperfusion injury: A swine model

Reactive oxygen species have a key role in liver ischemia-reperfusion (I/R) injury. In the present study, the effect of the anti-oxidant compound lazaroid U-74389G in preventing liver I/R injury was investigated in a swine model. Ischemia was produced by portal vein occlusion. Two sets of experiments were performed, each with two groups (n=7 per group). In the first group, the potential protective effect of an intracaval injection of U-74389G after a 30-min ischemia, followed by a 60-min reperfusion period was assessed (biopsies at 0, 15, 30 and 90 min experimental time). In the second set, the effect of intracaval U-74389G injection after 30 min of ischemia, followed by a longer reperfusion period of 120 min was determined (biopsies at 0, 15, 30 and 150 min experimental time). Liver malondialdehyde, hepatocyte vacuolation-degeneration, venous congestion, inflammatory cell infiltration, sinus congestion-dilation and Chiu score of intestinal damage were determined at up to 150 min of reperfusion. In the second set of experiments, the Chiu score of intestinal damage was improved by the administration of U-74389G (3.17±0.40 vs. 4.33±0.21; P=0.030). However, in the two sets of experiments, the liver inflammatory reaction was more pronounced in the U-74389G groups (P=0.017 for the first set, P=0.021 for the second set). No significant effect of U-74389G on any other parameters was detected. In conclusion, intestinal damage due to portal venous congestion and reflow appears to be mitigated by the lazaroid U-74389G; however, intracaval administration of U-74389G does not appear to exert any protective effects against liver I/R-induced inflammation.

Effect of the Phosphodiesterase 5 Inhibitor Sildenafil on Ischemia-Reperfusion-Induced Muscle Mitochondrial Dysfunction and Oxidative Stress

Lower-limb ischemia-reperfusion (IR) is frequent and associated with significant morbidity and mortality. Phosphodiesterase 5 inhibitors demonstrated antioxidant and beneficial effects in several organs submitted to IR, but their effects on muscle mitochondrial functions after lower-limb IR are unknown. Unilateral hindlimb IR (2 h tourniquet followed by 2 h reperfusion) without or with sildenafil (1mg/kg ip 30 minutes before ischemia) was performed in 18 mice. Maximal oxidative capacity (V_Max), relative contribution of the mitochondrial respiratory chain complexes, calcium retention capacity (CRC)—a marker of apoptosis—and reactive oxygen species (ROS) production were determined using high-resolution respirometry, spectrofluorometry, and electron paramagnetic resonance in gastrocnemius muscles from both hindlimbs. IR significantly reduced mitochondrial V_Max (from 11.79 ± 1.74 to 4.65 ± 1.11 pmol/s*mg wet weight (ww), p < 0.05, −50.2 ± 16.3%) and CRC (from 2.33 ± 0.41 to 0.84 ± 0.18 µmol/mg dry weight (dw), p < 0.05; −61.1 ± 6.8%). ROS tended to increase in the ischemic limb (+64.3 ± 31.9%, p = 0.08). Although tending to reduce IR-related ROS production (−42.4%), sildenafil failed to reduce muscle mitochondrial dysfunctions (−63.3 ± 9.2%, p < 0.001 and −55.2 ± 7.6% p < 0.01 for V_Max, and CRC, respectively). In conclusion, lower limb IR impaired skeletal muscle mitochondrial function, but, despite tending to reduce ROS production, pharmacological preconditioning with sildenafil did not show protective effects.