RESUMO
BACKGROUND: Mechanical evacuation of capillary thrombi in free flaps is difficult, and often requires thrombolytic therapy. Utilizing machine perfusion systems, the possibility rises to salvage free flaps ex vivo by administering high doses of thrombolytic agents. The primary aim of this pilot study in a porcine model is to investigate the feasibility of ex vivo thrombolysis using an extracorporeal perfusion machine. METHODS: A model of stasis-induced thrombosis was used in 12 free rectus abdominis flaps harvested from six Dutch Landrace pigs. Compromised flaps were ex vivo perfused with University of Wisconsin preservation solution and treated according to the following study groups: (1) 1 mg of tissue plasminogen activator (t-PA) as additive, (2) 3 mg of t-PA as an additive, and (3) no thrombolytic additive. Microcirculation was assessed using near-infrared fluorescence angiography. RESULTS: Pedicled abdominal flaps were created and thrombus formation was successfully induced. Eleven abdominal flaps were perfused using the modified heart-lung machine setup. Near-infrared fluorescence angiography showed delayed or no filling was noted in the control group. In comparison, the flaps which were perfused with 1 mg t-PA or 3 mg t-PA as additive showed increased fluorescence intensity curves. CONCLUSION: This pilot study in a porcine model presents a reliable and reproductive stasis-induced thrombosis model in free flaps. By adding t-PA to a custom-made extracorporeal perfusion system, the indocyanine green fluorescence intensity curves increased of all flaps that were perfused with different dosages of t-PA as additives, indicating restoration of capillary pressure and microcirculatory inflow.
Assuntos
Retalhos de Tecido Biológico , Trombose , Suínos , Animais , Retalhos de Tecido Biológico/irrigação sanguínea , Ativador de Plasminogênio Tecidual , Projetos Piloto , Microcirculação , Perfusão , Terapia Trombolítica , Trombose/tratamento farmacológicoRESUMO
BACKGROUND: Extracorporeal perfusion is a technique that aims to safely prolong tissue preservation by reducing ischemia-reperfusion injury. Free muscle flaps provide a sensitive research model due to their low ischemic tolerance. However, long-term perfusion of free muscle flaps is scarcely researched. The aim of this study was to compare tissue damage in musculocutaneous flaps during 36 h of extracorporeal perfusion versus static cold storage. MATERIALS AND METHODS: Bilateral free rectus abdominis flaps were harvested from five Dutch Landrace pigs (weight: 53-59 kg). Flaps were treated for 36 h according to the following study groups: (1) cold storage at 4°C-6°C (n = 4), (2) perfusion with histidine-tryptophan-ketoglutarate (HTK) at 8°C-10°C (n = 3), (3) perfusion with University of Wisconsin solution (UW) at 8°C-10°C (n = 3). Perfusion fluid samples (creatinine kinase, blood gas) and biopsies for quantitative polymerase chain reaction were collected at multiple time points. Microcirculation was assessed at 24 h of preservation using indocyanine-green fluorescence angiography. Flap weight was measured at the start and end of the preservation period. RESULTS: Successful and stable perfusion for 36 h was achieved in all perfused flaps. The mean creatinine kinase increase in the perfusion fluid was comparable in both the groups (UW: +43,144 U/L, HTK: +44,404 U/L). Mean lactate was higher in the UW group than in the HTK group (6.57 versus 1.07 mmol/L). There were homogenous and complete perfusion patterns on indocyanine-green angiography in both the perfusion groups, in contrast to incomplete and inhomogeneous patterns during cold storage. Expression of genes related to apoptosis and inflammation was lower in perfused flaps than in the cold storage group. Weight increase was highest in the HTK group (78%; standard deviation [SD], 29%) compared with UW (22%; SD, 22%) and cold storage (0.7%; SD, 4%). CONCLUSIONS: Long-term extracorporeal perfusion of free rectus abdominis flaps is feasible. Outcomes in the perfusion groups seemed superior compared to cold storage. Hypotheses gained from this research need to be further explored in a replantation setting.
Assuntos
Retalho Miocutâneo , Preservação de Tecido , Adenosina , Alopurinol , Animais , Creatina Quinase/análise , Feminino , Glucose , Glutationa , Insulina , Manitol , Modelos Animais , Soluções para Preservação de Órgãos , Cloreto de Potássio , Procaína , Rafinose , SuínosRESUMO
Recently three different neonatal extracorporeal membrane oxygenation (ECMO) circuits have been employed in our clinic. These circuits were compared for clotting and bleeding complications. Initially, we used an ECMO circuit containing a roller pump and venous bladder without severe complications. Manufacturing of circuit components was discontinued, necessitating the replacement of this circuit by a circuit with a centrifugal pump with 3/8 inch inlet and outlet. Acute increase of oxygenator resistance requiring emergency changeout became unexpectedly a regularly occurring complication. The increase in resistance was suspected to be caused by oxygenator clotting, although oxygenator function was preserved. To prevent this complication, we changed to a levitating centrifugal pump with 1/4 inch inlet and outlet, after which no oxygenator malfunction has been observed. Macroscopic and electron microscopic analysis demonstrates that small clots are formed within the circuit, presumably in or near the centrifugal pump, which are transported to the oxygenator and clog up the hollow fiber layer at the inlet side, barely penetrating the oxygenator beyond this first layer. Our results suggest that low blood velocities accompanied with recirculation of blood within or near the centrifugal pump and/or heat generation within the pump could contribute to the formation of these clots.
Assuntos
Oxigenação por Membrana Extracorpórea , Hemostáticos , Trombose , Humanos , Recém-Nascido , Coagulação Sanguínea , Oxigenação por Membrana Extracorpórea/efeitos adversos , Oxigenação por Membrana Extracorpórea/métodos , Trombose/etiologia , Oxigenadores de Membrana/efeitos adversosRESUMO
BACKGROUND: Static cold storage is the gold standard of preservation in vascularized composite allotransplantation and allows a preservation time of 4-6 hours. Machine preservation is a promising technique for prolonged preservation; however, studies on extended preservation that compare different preservatives are scarce. This study aims to assess the feasibility of 24-hour acellular perfusion and compares different preservation solutions in a porcine myocutaneous flap replantation model. METHODS: Six harvested bilateral myocutaneous flaps of three Dutch Landrace pigs were perfused hypothermically for 24 hours with University of Wisconsin machine perfusion solution (UW-MPS; n = 2) or histidine-tryptophan-ketoglutarate solution (HTK; n = 2) or preserved on ice for 4 hours (n = 2) before orthotopic replantation. Animals were observed for 7 days after replantation. Skeletal muscle injury was assessed by biochemical markers during perfusion, and muscle biopsies were analyzed for ischemia reperfusion injury directly after preservation and at 1, 3, and 7 days after replantation. RESULTS: Markers of muscle damage varied during perfusion, but decreased overall in both perfusion groups. Flap weight increased 60% and 97% in the HTK-perfused flaps, compared with -6% and -7% in the UW-MPS-perfused flaps after 24 hours. Histopathologic evaluation demonstrated decreased muscle damage in flaps perfused with HTK compared with the UW-MPS-perfused flaps at 1 week after replantation. CONCLUSIONS: Machine perfusion of myocutaneous flaps for 24 hours with subsequent replantation is feasible, but warrants further research. Perfusion with HTK solution seemed to result in better histological outcomes 7 days after reperfusion compared with UW-MPS.
RESUMO
BACKGROUND: There is a risk for thrombotic complications (2 to 5 percent) associated with microsurgical reconstruction. Current thrombolytic therapy has a salvage rate between 60 and 70 percent, but it is afflicted by bleeding complications (2 to 6 percent). The use of machine perfusion for delivering thrombolytic agents is a new method that could potentially reduce these complications. In this article, the authors compared flap salvage outcomes comparing machine thrombolysis versus a manual flush with tissue plasminogen activator. METHODS: Sixteen bilateral flaps (12 × 9 cm) were dissected from eight female Dutch Landrace pigs (70 kg). Thrombosis was induced in free rectus abdominis flaps by clamping the pedicle's veins for 2 hours. Flaps were either thrombolysed with 2 mg tissue plasminogen activator (1 mg/ml) during 2 hours of machine perfusion (perfusion group; n = 8) or injected intraarterially (manual group; n = 8) before replantation. Near-infrared fluorescence angiography was used to confirm thrombus formation and to assess tissue perfusion; muscle biopsy specimens were analyzed for ischemia/reperfusion injury directly after thrombolysis and 15 hours after replantation. RESULTS: A higher incidence of secondary thrombosis was seen in the manual group compared to the perfusion group ( n = 6 versus n = 0, respectively; p < 0.001), resulting in two complete flap failures. Fifteen hours after replantation, mean fluorescence intensities were 13.0 (95 percent CI, 10.1 to 15.8) and 24.6 (95 percent CI, 22.0 to 27.2) in the perfusion and manual group, respectively ( p < 0.001), and mean muscle injury scores were comparable, measuring 7.5 ± 1.5. CONCLUSION: Two hours of machine thrombolysis of compromised flaps in a porcine model showed higher salvage rates compared to a manual injection with tissue plasminogen activator and reduced the incidence of secondary thrombosis. CLINICAL RELEVANCE STATEMENT: Using machine perfusion systems for ex vivo thrombolysis provides the benefits of local treatment of a composite tissue without the risk of systemic complications and may improve salvage rates and reduce the incidence of secondary thrombosis.