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Biomedical subjects

Andrej Banic

Publications and source records attributed to Andrej Banic.

15 recordsLinked to original sources
PubMed2006

Evaluation of late results in breast reconstruction by latissimus dorsi flap and prosthesis implantation.

BACKGROUND: Breast reconstruction by latissimus dorsi myocutaneous flap in combination with a prosthesis is a widely used, well-established procedure. Short- and medium-term evaluation after this procedure is well described in the literature, but there have been no evaluations of the late course (over 10 years) published until now. METHODS: In a retrospective study, 68 patients operated on by means of this technique at the authors' institution from 1981 to 1993 resulting in a minimal follow-up of 10 years were included. Patients were invited to an interrogation, clinical examination, and photographic documentation (n = 51). Incidence of late flap or prosthesis-related complications, number of and indications for corrective procedures, and the correlation of the patients' subjective judgment and objective results in the late course have been the main interest of the authors' survey. RESULTS: The authors found that 50 percent of the patients needed a late reoperation for change or removal of the prosthesis. Seven (10 percent) of 68 patients needed a definitive removal of the implant in the late course. Assessment of the photographic documentation of the late result by four nonprofessionals showed that the objective aesthetic results of a considerable number of the authors' reconstructions were not sufficient. CONCLUSION: The procedure combines two basic techniques of reconstructive surgery, the soft-tissue restoration by a pedicled flap as the autologous reconstructive component and the volume reconstruction by prosthesis. Therefore, these patients are subject to a cumulation of the basic morbidity of the two techniques. The authors conclude that the indication for this procedure should be restricted to patients not qualifying for "pure" reconstructive techniques.

Adolescent↗
PubMed2005

Is hemoglobin in hemoglobin vesicles infused for isovolemic hemodilution necessary to improve oxygenation in critically ischemic hamster skin?

The aim of this study was to test the influence of hemoglobin, encapsulated in phospholipid vesicles as an oxygen carrier, given in the course of isovolemic hemodilution to improve oxygenation in critically ischemic hamster flap tissue. Capillary hemodynamics and macromolecular leakage were investigated with intravital microscopy and analyzed off-line with the CapImage software. Partial tissue oxygen tension was measured with fluorescence quenching electrodes. The occurrence of apoptosis was assessed with the terminal deoxynucleotidyl transferase-mediated dUTP nick-end labeling assay. Vesicles with (HbV) or without (V) encapsulated Hb were suspended in 6% hydroxyethyl starch (HES) used for the 33% blood exchange. In the ischemic tissue, hemodilution led to an increase in functional capillary density by 31% for HES (P < 0.01 vs. other groups), 66% for V-HES, and 62% for HbV-HES (all P < 0.01 vs. control). Capillary diameters behaved inversely proportional to capillary microhemodynamics. The 20% increase in macromolecular leakage found over time in control animals was completely abolished in the vesicles groups (P < 0.01) but not with HES. Oxygen tension was improved from 10.7 to 16.0 mmHg after HbV-HES (P < 0.01 vs. baseline and other groups). Compared with the other groups, apoptosis was significantly reduced after HbV-HES (P < 0.01). We conclude that the encapsulation of Hb was essential to attenuate hypoxia and subsequent cell death in the critically ischemic tissue. However, the effect was partly attributed to the rheological changes exerted by the vesicles.

Acute Disease↗
PubMed2005

New generation of hemoglobin-based oxygen carriers evaluated for oxygenation of critically ischemic hamster flap tissue.

OBJECTIVES: The aim of this study was to investigate and compare the effects of a traditionally formulated, low-viscosity, right-shifted polymerized bovine hemoglobin solution and a highly viscous, left-shifted hemoglobin vesicle solution (HbV-HES) on the oxygenation of critically ischemic peripheral tissue. DESIGN: Randomized, prospective study. SETTING: University laboratory. SUBJECT: A total of 40 male golden Syrian hamsters. INTERVENTIONS: Island flaps were dissected from the back skin of anesthetized hamsters. The flap included a critically ischemic, hypoxic area that was perfused via a collateralized vasculature. One hour after completion of the preparation, the animals received a 33% blood exchange with 6% hydroxyethyl starch 200/0.5 (HES, n = 9), HbV suspended in HES (HbV-HES, n = 8), or polymerized bovine hemoglobin solution (n = 9). MEASUREMENTS AND MAIN RESULTS: Three hours after the blood exchange, microcirculatory blood flow (laser-Doppler flowmetry) was increased to 262% of baseline for HbV-HES (p < .01) and 197% for polymerized bovine hemoglobin solution (p < .05 vs. baseline and HbV-HES). Partial tissue oxygen tension (bare fiber probes) was only improved after HbV-HES (9.4 torr to 14.2 torr, p < .01 vs. baseline and other groups). The tissue lactate/pyruvate ratio (microdialysis) was elevated to 51 in the untreated control animals, and to 34 +/- 8 after HbV-HES (p < .05 vs. control) and 38 +/- 11 after polymerized bovine hemoglobin solution (not significant). CONCLUSIONS: Our study suggests that in critically ischemic and hypoxic collateralized peripheral tissue, oxygenation may be improved by normovolemic hemodilution with HbV-HES. We attributed this improvement to a better restoration of the microcirculation and oxygen delivery due to the formulation of the solution.

Animals↗
PubMed2005

Heat shock preconditioning reduces ischemic tissue necrosis by heat shock protein (HSP)-32-mediated improvement of the microcirculation rather than induction of ischemic tolerance.

INTRODUCTION: Supraphysiologic stress induces a heat shock response, which may exert protection against ischemic necrosis. Herein we analyzed in vivo whether the induction of heat shock protein (HSP) 32 improves survival of chronically ischemic myocutaneous tissue, and whether this is based on amelioration of microvascular perfusion or induction of ischemic tolerance. METHODS: The dorsal skin of mice was subjected to local heat preconditioning (n = 8) 24 hours before surgery. In additional heat-preconditioned animals (n = 8), HSP-32 was inhibited by tin-protoporphyrin-IX. Unconditioned animals served as controls (n = 8). A random-pattern myocutaneous flap was elevated in the back of the animals and fixed into a dorsal skinfold chamber. The microcirculation, edema formation, apoptotic cell death, and tissue necrosis were analyzed over a 10-day period using intravital fluorescence microscopy. RESULTS: HSP-32 protein expression was observed only in heat-preconditioned but not in unconditioned flaps. Heat preconditioning induced arteriolar dilation, which was associated with a significant improvement of both arteriolar blood flow and capillary perfusion in the distal part of the flap. Further, heat shock reduced interstitial edema formation, attenuated apoptotic cell death, and almost completely abrogated the development of flap necrosis (4% +/- 1% versus controls: 53% +/- 5%; P[r] < 0.001). Most strikingly, inhibition of HSP-32 by tin-protoporphyrin-IX completely blunted the preconditioning-induced improvement of microcirculation and resulted in manifestation of 72% +/- 4% necrosis. CONCLUSION: Local heat preconditioning of myocutaneous tissue markedly increases flap survival by maintaining adequate nutritive perfusion rather than inducing ischemic tolerance. The protection is caused by the increased arteriolar blood flow due to significant arteriolar dilation, which is mediated through the carbon monoxide-associated vasoactive properties of HSP-32.

Analysis of Variance↗
PubMed2005

The influence of trauma and ischemia on carbohydrate metabolites monitored in hamster flap tissue.

To monitor hypoperfusion of the peripheral tissues in critical illness caused by injury, we measured the concentrations of glucose, pyruvate, and lactate in traumatized and ischemic hamster flap tissue with the use of microdialysis. The interruption of the anatomic blood supply led to a drastic decrease in microvascular blood flow (laser Doppler flowmetry) and partial tissue oxygen tension (dye fluorescence quenching technique) in the ischemic part of the flap (both P < 0.01). In the traumatized area, blood flow, oxygen tension, and pyruvate were similar to the healthy control tissue throughout the experiments, whereas pyruvate was reduced in the ischemic tissue (P < 0.05 versus baseline and other tissues). Lactate was increased in both parts of the flap (P < 0.01 versus baseline and other groups for ischemic, not significant for traumatized). The sensitivity to detect ischemic hypoxia was 62% for lactate and 93% for lactate/pyruvate ratio (L/P) (P < 0.01). The specificity to discern ischemia-related from trauma-related changes was 71% for lactate and 70% for L/P (not significant). Our results suggest that L/P is more accurate than lactate for monitoring ischemia-related hypoxia after trauma. However, the rate of increased values originating from normally perfused but traumatized tissue was high for both markers.

Animals↗
PubMed2005

Preconditioning with monophosphoryl lipid A improves survival of critically ischemic tissue.

In this study we sought to assess the effects of preconditioning with monophosphoryl lipid A on critically ischemic wound margins and on systemic and local hemodynamics and oxygenation during prolonged anesthesia with volatile anesthetics and narcotics. Twenty large white pigs were randomly assigned to receive either monophosphoryl lipid A 35 mug/kg IV or saline 24 h before dissection of a buttock flap. The animals were anesthetized with isoflurane (end-tidal concentration approximately 1.25%) for surgery and subsequent monitoring of hemodynamics and oxygenation both systemically and in the flap tissue for 6 h. Preconditioning resulted in increased cardiac index and oxygen delivery (both P < 0.05) and in decreased central venous pressure and systemic vascular resistance (both P < 0.01). In the preconditioned flap tissue, microcirculatory blood flow (laser Doppler flowmetry) and partial tissue oxygen tension (polarographic microprobes) were up to 2.5-fold higher compared with control (both P < 0.05) and flap necrosis was reduced by 20% on postoperative day 14 (P < 0.05). Our results suggest that preconditioning with a single dose of monophosphoryl lipid A may attenuate ischemia-related wound healing complications, which may be related to an improvement in perfusion and oxygenation of this tissue. Furthermore, preconditioning exerted a systemic cardiovascular stabilization effect during prolonged isoflurane anesthesia.

Anesthesia, General↗
PubMed2005

MRI of merkel cell carcinoma: histologic correlation and review of the literature.

OBJECTIVE: The objective of this study was to determine the MRI characteristics of Merkel cell carcinoma, with an emphasis on histologic correlation. MATERIALS AND METHODS: The demographic information about 15 patients from our institution and their MRI examinations were retrospectively reviewed by three musculoskeletal radiologists by consensus for lesion location and intrinsic characteristics. The study group was composed of three women and 12 men who ranged in age from 48 to 87 years, with a mean age of 75 years. Histology results of resected specimens were reviewed in all cases and were correlated with imaging. RESULTS: MRI showed skin thickening, subcutaneous reticular stranding (n = 9, 60%); multiple anatomically aligned subcutaneous soft-tissue masses, representing lymphatic tumor nodules (n = 5, 33%); lymph node enlargement with fine, compressed, retained fatty tissue (n = 5, 33%); nodal necrosis (n = 1); and perifascial and intramuscular metastases (n = 2). Histology confirmed the lymphatic nature of the soft-tissue Merkel cell tumors. CONCLUSION: Patients with Merkel cell tumors may present at imaging with subcutaneous lymphatic reticular stranding, multiple subcutaneous masses, and lymph node metastases. Often there is massive lymph node enlargement with fine, compressed, retained fatty tissue.

Aged↗
PubMed2004

Evolution of a "falx lunatica" in demarcation of critically ischemic myocutaneous tissue.

Using intravital microscopy in a chronic in vivo mouse model, we studied the demarcation of myocutaneous flaps and evaluated microvascular determinants for tissue survival and necrosis. Chronic ischemia resulted in a transition zone, characterized by a red fringe and a distally adjacent white falx, which defined the demarcation by dividing the proximally normal from the distally necrotic tissue. Tissue survival in the red zone was determined by hyperemia, as indicated by recovery of the transiently reduced functional capillary density, and capillary remodeling, including dilation, hyperperfusion, and increased tortuosity. Angiogenesis and neovascularization were not observed over the 10-day observation period. The white rim distal to the red zone, appearing as "falx lunatica," showed a progressive decrease of functional capillary density similar to that of the necrotic distal area but without desiccation, and thus transparency, of the tissue. Development of the distinct zones of the critically ischemic tissue could be predicted by partial tissue oxygen tension (Pt(O(2))) analysis by the time of flap elevation. The falx lunatica evolved at a Pt(O(2)) between 6.2 +/- 1.3 and 3.8 +/- 0.7 mmHg, whereas tissue necrosis developed at <3.8 +/- 0.7 mmHg. Histological analysis within the falx lunatica revealed interstitial edema formation and muscle fiber nuclear rarefaction but an absence of necrosis. We have thus demonstrated that ischemia-induced necrosis does not demarcate sharply from normal tissue but develops beside a fringe of tissue with capillary remodeling an adjacent falx lunatica that survives despite nutritive capillary perfusion failure, probably by direct oxygen diffusion.

Animals↗
PubMed2004

Intraluminal laser light source and external solder: in vivo evaluation of a new technique for microvascular anastomosis.

BACKGROUND AND OBJECTIVES: Current laser-assisted end-to-end anastomoses are performed by irradiating the vessel wall from outside after additional fixation with three to six sutures. These sutures are needed to provide adequate approximation of the vessel stumps. We present a new laser soldering technique that is based on an intraluminal laser light source centered in a balloon catheter, and external application of a solder. This technique was applied in vivo in order to test its feasibility under clinical conditions. STUDY DESIGN/MATERIALS AND METHODS: Seven white pigs were treated with a total of fourteen end-to-end laser-anastomoses of their saphenous arteries having outer diameters of 2 mm. The vessels were stented over an intraluminal balloon catheter, which was maximally dilated and which allowed for a precise approximation of the vascular stumps. An 808 nm diode laser was coupled into a specially designed optical fiber producing a 360 degrees radiation ring inside the balloon catheter. An indocyanine green (ICG) doped liquid albumin solder was applied on the external surface of the vascular stumps. Laser soldering was achieved by irradiating with a 808 nm laser diode for 75 seconds. Tightness of the anastomoses was evaluated by clamping the artery distal to the anastomosis for 1 hour, and patency was tested over an observation period of 3 hours, during which the animals were heparinized. Thereafter, the anastomoses were harvested for histomorphological examination. RESULTS: All anastomoses remained patent over the entire observation period. Some leakage was observed in three anastomoses, which was explained by a deviation of the illumination fiber from the center of the balloon leading to an inhomogeneous irradiation of the vessel wall. Histology revealed perfect adaptation of the vascular stumps. A segment of denaturated vascular collagen was observed, that corresponded to the irradiated, solder-covered zone. CONCLUSION: Patent, maximally dilated and well adapted microvascular anastomoses could be obtained without the need of stay sutures. A well centered laser light source is indispensable for avoiding inhomogenous welding, thus causing leakage.

Anastomosis, Surgical↗
PubMed2003

Improved oxygenation in ischemic hamster flap tissue is correlated with increasing hemodilution with Hb vesicles and their O2 affinity.

The aim of this study was to test the influence of oxygen affinity of Hb vesicles (HbVs) and level of blood exchange on the oxygenation in collateralized, ischemic, and hypoxic hamster flap tissue during normovolemic hemodilution. Microhemodynamics were investigated with intravital microscopy. Tissue Po2 was measured with Clark-type microprobes. HbVs with a P50 of 15 mmHg (HbV15) and 30 mmHg (HbV30) were suspended in 6% Dextran 70 (Dx70). The Hb concentration of the solutions was 7.5 g/dl. A stepwise replacement of 15%, 30%, and 50% of total blood volume was performed, which resulted in a gradual decrease in total Hb concentration. In the ischemic tissue, hemodilution led to an increase in microvascular blood flow to maximally 141-166% of baseline in all groups (median; P < 0.01 vs. baseline, not significant between groups). Oxygen tension was transiently raised to 121 +/- 17% after the 30% blood exchange with Dx70 (P < 0.05), whereas it was increased after each step of hemodilution with HbV15-Dx70 and HbV30-Dx70, reaching 217 +/- 67% (P < 0.01) and 164 +/- 33% (P < 0.01 vs. baseline and other groups), respectively, after the 50% blood exchange. We conclude that despite a decrease in total Hb concentration, the oxygenation in the ischemic, hypoxic tissue could be improved with increasing blood exchange with HbV solutions. Furthermore, better oxygenation was obtained with the left-shifted HbVs.

Animals↗
PubMed2003

Normovolemic hemodilution with Hb vesicle solution attenuates hypoxia in ischemic hamster flap tissue.

The aim of this study was to test whether oxygenation in acutely ischemic, collateralized tissue may be improved by normovolemic hemodilution with a solution containing liposome-encapsulated human Hb (HbV). A skin flap model in anesthetized hamsters was used, which consisted of two parts receiving either anatomic or collateral perfusion. Microhemodynamics were investigated with intravital microscopy. Partial tissue oxygen tension was measured with a Clark-type microprobe. Hemodilution was obtained by exchanging 50% of the total blood volume with HbV suspended in 8% human serum albumin (HSA8) or 6% Dextran 70 (Dx70). The size of the vesicles was 276 nm, the P(50) was 22 mmHg, and the Hb concentration of the solutions was 7.5 g/dl. Colloid osmotic pressure and viscosity were 49.9 mmHg and 8.7 cP for HbV-Dx70 and 40.0 mmHg and 2.9 cP for HbV-HSA8, respectively. Hemodilution with HbV-Dx70 led to an increase in microvascular blood flow in the ischemic microvessels to maximally 158% (median, P < 0.01), whereas blood flow remained virtually unchanged after hemodilution with HbV-HSA8. In the ischemic tissue, oxygen tension was improved from 11.9 to 17.0 mmHg (P < 0.01) after hemodilution with HbV-Dx70 but remained virtually unchanged after hemodilution with HbV-HSA8. Our study suggests that the oxygenation in acutely ischemic, collateralized tissue may be improved by normovolemic hemodilution with HbV suspended in Dx70. The effect was achieved by an increase in microcirculatory blood flow related to the rheological properties of the suspending medium.

Animals↗
PubMed2003

Redistribution of microcirculatory blood flow within the intestinal wall during sepsis and general anesthesia.

BACKGROUND: Hypoperfusion of the intestinal mucosa remains an important clinical problem during sepsis. Impairment of the autoregulation of microcirculatory blood flow in the intestinal tract has been suggested to play an important role in the development of multiple organ failure during sepsis and surgery. The authors studied microcirculatory blood flow in the gastrointestinal tract in anesthetized subjects during early septic shock. METHODS: Eighteen pigs were intravenously anesthetized and mechanically ventilated. Regional blood flow in the superior mesenteric artery was measured with ultrasound transit time flowmetry. Microcirculatory blood flow was continuously measured with a six-channel laser Doppler flowmetry system in the mucosa and the muscularis of the stomach, jejunum, and colon. Eleven pigs were assigned to the sepsis group, while seven animal served as sham controls. Sepsis was induced with fecal peritonitis, and intravenous fluids were administered after 240 min of sepsis to alter hypodynamic sepsis to hyperdynamic sepsis. RESULTS: In the control group, all monitored flow data remained stable throughout the study. During the hypodynamic phase of sepsis, cardiac output, superior mesenteric artery flow, and microcirculatory blood flow in the gastric mucosa decreased by 45%, 51%, and 40%, respectively, compared to baseline (P < 0.01 in all). Microcirculatory blood flow in the muscularis of the stomach, jejunum, and colon decreased by 55%, 64%, and 70%, respectively (P < 0.001 in all). In contrast, flow in the jejunal and colonic mucosa remained virtually unchanged. During the hyperdynamic phase of sepsis, there was a threefold increase in cardiac output and superior mesenteric artery flow. Blood flow in the gastric, jejunal, and colonic mucosa also increased (22%, 24%, and 31% above baseline, respectively). Flow in the muscularis of the stomach returned to baseline, while in the jejunum and colon, flow in the muscularis remained significantly below baseline (55% and 45%, respectively, P< 0.01). CONCLUSIONS: It appears that in early septic shock, autoregulation of microcirculatory blood flow is largely intact in the intestinal mucosa in anesthetized pigs, explaining why microcirculatory blood flow remained virtually unchanged. This may be facilitated through redistribution of flow within the intestinal wall, from the muscularis toward the mucosa.

Anesthesia, General↗
PubMed2003

Is it safe to combine abdominoplasty with other dermolipectomy procedures to correct skin excess after weight loss?

The development of sophisticated bariatric surgery techniques has led to an increasing number of patients demanding a complexity of body contouring procedures that can be achieved either with a step-by-step approach or by combining dermolipectomy in various regions. The aim of this study was to test the hypothesis that abdominoplasty-related morbidity and outcome may be worsened by combining abdominoplasty with other dermolipectomies and to determine whether any predictive risk factor could be identified. Seventy-three consecutive patients undergoing abdominoplasty with (n = 26) and without (n = 47) additional dermolipectomy on the upper arms, inner thighs, breasts, and buttocks were included in this study. Additional dermolipectomies did not increase abdominoplasty-related morbidity but revealed better long-term results (p = 0.10). Statistically significant risk factors were male sex, age (>41 years), overweight (BMI > 30), prolonged operations (>3 hours), and extensive blood loss (1,000 mL). Most importantly, better outcome was obtained in patients whose weight reduction was greater (p = 0.04). The authors' results suggest that combined dermolipectomy procedures can be advocated in patients who have reached their intended level of weight reduction and if prolonged operative time and excessive blood loss are avoided.

Abdomen↗
PubMed2002

Acute normovolemic hemodilution improves oxygenation in ischemic flap tissue.

BACKGROUND: The flaps used in reconstructive surgery are prone to ischemia and hypoxia, which imply a considerable risk of wound-healing complications. During normovolemic hemodilution, the oxygenation may further deteriorate because of the lack of erythrocytes or improve because of increased microcirculatory blood flow. The aim of this study was to investigate the net effect of normovolemic hemodilution of various degrees on the microcirculation and oxygenation in ischemic flap tissue in adult minipigs. METHODS: A rectangular flap was raised in the middle of the epigastrium, consisting of an adequately perfused portion and a partly ischemic portion. The animals were randomly assigned to either the control group (n = 10) or the experimental group (n = 10) receiving graded normovolemic hemodilution with 6% hydroxyethyl starch 200-0.5. RESULTS: Normovolemic hemodilution caused a significant linear increase in total blood flow to the flap (measured by transit time flowmetry). In the ischemic flap tissue, both oxygen tension (measured by polarographic cells) and venous base excess were transiently improved during hemodilution (F = 4.79 and P = 0.019 for the regression of tissue oxygen tension on hemoglobin and hemoglobin squared, and F = 4.18 and P = 0.029 for base excess). The expected values reached a peak at hemoglobin concentrations of 9.1 and 8.5 g/dl, respectively. The measured values at this level of hemodilution were 17 +/- 10.7 mmHg (mean +/- SD) versus 7.6 +/- 1.9 mmHg (baseline) for oxygen tension and -1.7 +/- 3.4 versus -5.6 +/- 4.1 mM for venous base excess. CONCLUSIONS: Our results suggest that the oxygenation in ischemic and hypoxic flap tissue may be improved by normovolemic hemodilution. The maximal benefit may be expected at a hemoglobin concentration at or slightly less than 9 g/dl.

Animals↗