Hemodynamic changes and fluid shifts after large-volume fluid infiltration: results from a porcine model.

While certain parameters such as blood loss and serum lidocaine levels following liposuction have been well studied, fluid shifts between the intravascular and extravascular space have not. With the advent of large volume liposuction, prudent fluid management has become obligatory. Hence, the reason for our study.To test the impact of large volume infiltration on intercompartmental fluid shifts, we measured urine output and hemodynamic changes in 10 anesthetized female Yorkshire pigs weighing between 50 and 85 kg. Eight pigs were infused with 5 to 10 L of tumescent fluid. Two pigs were anesthetized, received no wetting solution, and served as controls. Hemodynamic variables were recorded before infusion and hourly for 48 hours. Animals were extubated after 4 hours of anesthesia. Plasma volume was measured using Evan's Blue Dye, and intravascular fluid shifts were calculated using Foldager's method.Total fluid shift into the intravascular space ranged between 511 and 1036 mL per animal with a mean of 767 mL in the first 3 hours. Higher volumes of fluid infiltration did not lead to fluid overload in the experimental group. Hemodynamic changes were characterized by significant increases in central venous pressure, cardiac output, pulmonary artery pressure, and heart rate consistent with the increase in intravascular volume. Hemodynamic parameters returned to baseline 20 hours following tumescent fluid infiltration.In this porcine model, animals were able to tolerate large fluid challenges delivered by clysis with statistically significant but only modest increases in hemodynamic parameters which gradually returned to baseline within 20 hours.

A new composite facial and scalp transplantation model in rats.

There are limited sources of autogenous tissue available for reconstruction of severe facial and scalp deformities caused by extensive tumor ablation, burns, or trauma. Allografts from cadaveric sources may serve as a reconstructive alternative. However, technical and immunological aspects of harvesting and transplanting face and scalp flaps limit the routine use of such procedures. For evaluation of the feasibility of composite-tissue reconstruction, an experimental model of composite face/scalp flap transplantation in rats was designed. Technical aspects of the model, survival rates, and the complications encountered during development of the model are presented. A total of 64 animals, in three experimental groups, were studied. In group I, the anatomical study group (n = 6), the anatomical features of the face and scalp region in rats were explored. Groups II and III were the transplantation groups. Isograft transplantations were performed between identical Lewis rats (RT11 to RT11), and allografts were transplanted, across major histocompatibility complex barriers, between Lewis-Brown Norway rats (RT1l/n) and Lewis rats (RT11). In group II (the control group, n = 8), transplantation of nonvascularized composite face/scalp isografts and allografts was performed. In group III (the transplantation group, n = 50), vascularized face/scalp isografts (n = 36) and allografts (n = 14) were transplanted. Complications included partial or total flap necrosis, death attributable to food aspiration, and poor general condition. To prevent acute and chronic allograft rejection, cyclosporine A (16 mg/kg per day) therapy was initiated 24 hours after transplantation; the dose was tapered to 2 mg/kg per day within 4 weeks and was maintained at that level thereafter. Long-term survival (>170 days) was achieved, without any signs of rejection, with low-dose (2 mg/kg per day) cyclosporine A therapy. This is the first report documenting successful composite face/scalp flap transplantation in the rat model.

Composite vascularized skin/bone transplantation models for bone marrow-based tolerance studies.

There is an ongoing need to understand the mechanisms of bone marrow-based allograft tolerance. This is important in clarifying the diverse variables influencing the ultimate outcome of the solid organ and composite tissue transplants. To establish bone marrow transplantation as a routine clinical application, further experimental studies should be conducted to overcome the obstacles related to the bone marrow transplantation. These obstacles include graft versus host disease, immunocompetence, and toxicity of the conditioning regimens. For these purposes, novel experimental models are needed. In an attempt to provide a reliable research tool for bone marrow-based tolerance induction studies, we introduced different experimental models of modified vascularized skin/bone marrow (VSBM) transplantation technique for tolerance induction, monitoring, and maintenance studies. In this skin/bone transplantation model, the technical feasibility of concurrent or consecutive transplantation of the combination of bilateral vascularized skin, vascularized bone marrow, or vascularized skin/bone marrow transplants was investigated. Isograft transplantations were performed between genetically identical Lewis (LEW, RT1) rats. Five different experimental designs in 5 groups of 5 animals each were studied. Group I: Bilateral vascularized skin (VS) transplantation; group II: bilateral vascularized skin/bone transplantation; group III: vascularized skin transplantation on one side and vascularized skin/bone transplantation on the contralateral side; group IV: vascularized bone transplantation on one side and vascularized skin/bone transplantation on the contralateral side; group V: vascularized bone transplantation on one side and vascularized skin transplantation on the contralateral side. Successful transplantations were performed in all groups. The survival of the isograft transplants was evaluated clinically and histologically. All skin flaps remained pink and pliable and grew new hair. The viability of the compact bone, bone marrow and skin at 100 days posttransplant was confirmed by histologic evaluation, and bone marrow revealed active hematopoiesis. Bilateral skin/bone transplantation model may serve as an experimental tool to study new strategies in tolerance induction by altering the amount of the immunogenic load in the form of skin transplant and bone marrow delivery in the vascularized form, allowing for expedited engraftment of stem and progenitor cells.

Composite vascularized skin/bone graft model: a viable source for vascularized bone marrow transplantation.

In this study, we introduce a new model for vascularized skin and bone marrow transplantation. Twenty-five Lewis (RT1(1)) rats were studied. Anatomic dissection studies were performed in 5 animals. In the experimental group, 10 isograft transplantations were performed between Lewis rats. Combined groin skin and femoral bone flaps were transplanted based on the femoral artery and vein. Transplants were evaluated on a daily basis. All flaps survived without problems over 100 days posttransplant. The skin component remained pink and pliable, and grew new hair. Histological examination of the femoral bone (except the femoral head) revealed active hematopoiesis with a viable compact and cancellous bone components on day 100 posttransplant. This model can be applied to tolerance induction studies across the major Histocompatibility (MHC) barrier, where bone will serve as donor of stem and progenitor cells, and the skin flap will serve as a monitor of graft rejection.

Hydroxyapatite cement reconstruction in the growing craniofacial skeleton: an experimental model.

Hydroxyapatite cement (HAC) has been shown to osseoconduct and may even osseoconvert. These properties render it suitable for repairing cranial defects in growing children. The objective of this pilot study was to determine if growth is restricted after HAC reconstruction in a growing, nonprimate, animal model. Frontoparietal craniotomies were performed on 10 4-week-old Yorkshire piglets. In 3 control piglets, the bone flap was resutured; in 7 experimental piglets, the defect was reconstructed with HAC. Analysis 6 months after surgery included craniometric measurements, biomechanical testing, and histological sectioning. Nine craniofacial measurements did not differ between controls and experimental animals. The mean midline-to-temporal line distance contralateral to the defect was 20% larger in the experimental group (P = 0.006), however, and experimental animals had a larger difference between right and left orbital breadths (+3% difference versus -1% difference; P = 0.003). The mean stiffness of the HAC-repaired defect was not different from the contralateral side in contrast to the resutured bone flap in controls, which was significantly less stiff than unoperated bone (162 N/mm compared with 358 N/mm; P < 0.05). Based on our animal model, HAC seems to be a sound alternative method of craniotomy reconstruction in the growing skull.