Search PubMed⌕ Search

Biomedical subjects

B Vollmar

Publications and source records attributed to B Vollmar.

At least 73 records · Page 4Linked to original sources
PubMed2000

Vasomotion in critically perfused muscle protects adjacent tissues from capillary perfusion failure.

We analyzed the incidence and interaction of arteriolar vasomotion and capillary flow motion during critical perfusion conditions in neighboring peripheral tissues using intravital fluorescence microscopy. The gracilis and semitendinosus muscles and adjacent periosteum, subcutis, and skin of the left hindlimb of Sprague-Dawley rats were isolated at the femoral vessels. Critical perfusion conditions, achieved by stepwise reduction of femoral artery blood flow, induced capillary flow motion in muscle, but not in the periosteum, subcutis, and skin. Strikingly, blood flow within individual capillaries was decreased (P < 0.05) in muscle but was not affected in the periosteum, subcutis, and skin. However, despite the flow motion-induced reduction of muscle capillary blood flow during the critical perfusion conditions, functional capillary density remained preserved in all tissues analyzed, including the skeletal muscle. Abrogation of vasomotion in the muscle arterioles by the calcium channel blocker felodipine resulted in a redistribution of blood flow within individual capillaries from cutaneous, subcutaneous, and periosteal tissues toward skeletal muscle. As a consequence, shutdown of perfusion of individual capillaries was observed that resulted in a significant reduction (P < 0.05) of capillary density not only in the neighboring tissues but also in the muscle itself. We conclude that during critical perfusion conditions, vasomotion and flow motion in skeletal muscle preserve nutritive perfusion (functional capillary density) not only in the muscle itself but also in the neighboring tissues, which are not capable of developing this protective regulatory mechanism by themselves.

Animals↗
PubMed2000

Skin microvascular adaptations during maturation and aging of hairless mice.

Using intravital fluorescence microscopy in the ears of hairless mice, we determined skin microvascular adaptations during the process of aging from juvenile to adult and senescent life (6-78 wk). Despite an increase of ear area within the first 36 wk, the number and branching pattern of both arteriolar and venular microvessels remained constant during the whole life period. Both arterioles and venules exhibited an increase in length, diameter, and intervascular distance up to the age of 36 wk. With the increase of the size of the ears, the observation that cutaneous capillary density remained unchanged implied new capillary formation. During aging to 78 wk, capillary density in the ears was reduced to approximately 40%. Functional analysis revealed an appropriate hyperemic response to a 2-min period of ischemia during late juvenile and adult life, which, however, was markedly reduced during senescence. Thus, except for capillaries, there is no indication for age-related new vessel formation. The process of aging from adult to senescent life does not cause any significant remodeling but is associated with a decrease of nutritive perfusion and a functional impairment to respond to stimuli such as ischemia.

Adaptation, Physiological↗
PubMed2000

Model of chronic systolic and diastolic dysfunction after cryothermia-induced myocardial necrosis in rats.

BACKGROUND AND PURPOSE: Left ventricular dysfunction following myocardial infarction is the most important predictor of adverse prognosis. Novel treatment options in infarction require an appropriate experimental model with a standardized, hemodynamically relevant myocardial injury. We evaluated a cryoinjury model in rodents that allows quantitative analysis of systolic and diastolic dysfunction. METHODS: Anesthetized, orally intubated, and ventilated Lewis rats (n = 12) underwent sternotomy. Myocardial necrosis was induced by use of a standardized cryolesion to the obtuse margin of the left ventricle, freezing for 3 minutes to -160 degrees C. Left ventricular performance was analyzed at day 120 after cryoinjury. Sham-operated animals (n = 10) served as controls. RESULTS: Cryoinjured animals behaved normally and gained weight up to day 120. Average heart weight of cryoinjured animals significantly exceeded that of controls. Left ventricular systolic pressure and systolic, diastolic, and mean aortic pressures were lower 4 months after cryoinjury, whereas left ventricular end-diastolic pressure was significantly increased. Cryoinjured animals had reduced aortic blood flow, as well as impaired maximal left ventricular dP/dt during aortic occlusion and aortic occlusion-provoked peak systolic pressure. Analysis of maximal rates of isovolumic pressure decrease revealed significant reduction in peak negative dP/dt in cryoinjured animals. Finally, time constants of isovolumic pressure decline were significantly prolonged in cryoinjured animals. CONCLUSION: Standardized cryothermia induces a myocardial lesion that results in highly reproducible impairment of left ventricular performance 120 days after cryothermia. The model is ideally suited to test novel therapeutic strategies for myocardial dysfunction.

Animals↗
PubMed2000

Role of microcirculation in transplantation.

Microcirculatory derangements in organ transplantation, characterized by capillary perfusion failure and inflammation-associated leukocyte recruitment, are major determinants for the manifestation of graft dysfunction and destruction. Although preservation/cold storage, posttransplant reperfusion, and rejection have to be considered as individual factors that contribute to injury, recent studies have indicated that ischemia-reperfusion-associated events may trigger immune-response-mediated late rejection. There is major evidence that the microcirculatory derangements induced by cold preservation and reperfusion involve oxygen radicals, complement, phospholipase A2, leukotrienes, thromboxane, platelet-activating factor, and endothelin-1 as well as the activation and function of leukocytic and endothelial selectins, beta 2-integrins, and ICAM-1. This view is based on the fact that blockade or neutralization of these inflammatory mediators and adhesion molecules results in significant amelioration of microvascular graft dysfunction. In parallel, rejection-mediated microcirculatory derangements may not only be ameliorated by immunosuppressive agents, such as cyclosporin, deoxyspergualin, or RS61443, but may, in addition, effectively be inhibited by counteracting oxygen radicals, complement, platelet-activating factor, and adhesion molecules. The introduction of novel techniques for the study of the microcirculation in men, such as thermodiffusion and orthogonal polarization spectral imaging, may in the future assist in improving both early diagnosis of microcirculatory derangements and monitoring of appropriateness of therapy in clinical transplantation surgery.

Animals↗
PubMed1999

Attenuation of microvascular reperfusion injury in rat pancreas transplantation by L-arginine.

BACKGROUND: Despite improving results, exocrine complications remain a major challenge in clinical pancreas transplantation. The etiology of posttransplantation pancreatitis relates almost certainly to cold ischemia/reperfusion-induced microvascular injury with an imbalance of vasoconstricting and vasodilating mediators due to endothelial dysfunction. We therefore studied the effectiveness of a nitric oxide donor on postischemic microvascular reperfusion injury after pancreas transplantation. METHODS: Heterotopic isogeneic pancreaticoduodenal transplantation was performed in spontaneously breathing, chloralhydrate-anesthetized Sprague Dawley rats after 16 hr (n=5) of cold storage of the graft in 4 degrees C histidine-tryptophane-ketoglutarate solution. An additional five animals received L-arginine immediately before (50 mg/kg i.v.) and during the first 30 min of reperfusion (100 mg/kg i.v.). Five animals that did not undergo transplantation served as controls. Intravital fluorescence microscopy was used for analysis of functional capillary density, capillary diameters, and capillary red blood cell velocity in exocrine pancreatic tissue during 120 min of reperfusion. Histology served for quantitative assessment of inflammatory response (leukocytic tissue infiltration) and endothelial disintegration (edema formation). RESULTS: In L-arginine-treated animals, functional capillary density of exocrine tissue of pancreatic grafts was found slightly higher after 30 and 60 min, and significantly higher after 120 min of postischemic reperfusion compared with untreated pancreatic grafts. This was accompanied by a significant increase of capillary diameters. In parallel, pancreatic histology revealed significant attenuation of both leukocytic tissue infiltration and edema formation in the L-arginine-treated animals when compared with the nontreated controls. CONCLUSIONS: Besides reduction of leukocyte-dependent microvascular injury, L-arginine improves postischemic microvascular reperfusion, supposedly by capillary dilatation. Thus, our results suggest that supplement of nitric oxide during reperfusion is effective in attenuating exocrine microvascular reperfusion injury.

Animals↗
PubMed1999

Microvascular consequences of Kupffer cell modulation in rat liver fibrogenesis.

The process of Ito cell activation, which is thought to be the central pathogenic mechanism in liver fibrogenesis, may involve distinct interactions with Kupffer cells (KCs) mediated by various cytokines and growth factors. The aim of this study was to determine whether targeting KC function using gadolinium chloride (GdCl(3)) interferes with the manifestation of carbon tetrachloride (CCl(4))-induced hepatic fibrosis, placing special emphasis on the process of microvascular remodelling. Using in vivo fluorescence microscopy, characteristic microvascular features of CCl(4)-induced liver fibrosis, progressively observed within the 8-week period of toxin exposure, were the significant reduction in sinusoidal density; the increase of venular vascular space; the perivenular accumulation of Ito cells, with concomitant collagen deposition; and the collapse of parenchymal tissue. GdCl(3) effectively attenuated sinusoidal rarefaction and delayed, but did not prevent, the process of Ito cell activation-associated collagen deposition. Strikingly, the 8-week modulation of KC function by GdCl(3) exhibited sustained hepatocellular fatty vacuolation with organ weight increase, liver enzyme release, and bile flow reduction. Thus, GdCl(3) treatment attenuates the hepatic microvascular response, but favours fatty change and only delays the development of liver fibrosis following CCl(4)-exposure.

Analysis of Variance↗
PubMed1999

Epi-illumination fluorescent light microscopy for the in vivo study of rat hepatic microvascular response to cryothermia.

To elucidate the hepatic microvascular response to cryothermia, we studied the liver microcirculation of Sprague-Dawley rats after one and two 4-minute freeze-thaw cycles using intravital fluorescence microscopy. Irrespective of the number of freeze-thaw cycles applied, the nature of hepatic microvascular injury was characterized by complete stasis of sinusoidal blood flow within the central part of the cryolesions and heterogeneous sinusoidal perfusion in a critically perfused border zone located at the periphery of the lesions. Analysis over time (2 hours) revealed a successive shutdown of sinusoidal perfusion within this critically perfused border zone, which was caused by intravascularly lodging cell aggregates, blocking the lumen of individual sinusoids. The aggregates consisted of parenchymal cells and cell fragments, but did not include leukocytes or platelets. Strikingly, microvascular perfusion failure was associated with Ito cell disintegration and marked dilation of sinusoids (15.6 +/- 0.8 microm vs. 8.8 +/- 0.8 microm; P <.05). This excludes sinusoidal constriction as the cause of nutritive perfusion failure, and may indicate dysfunction of Ito cell-regulated vasomotor control by cryothermia. However, because circulating cell aggregates were frequently observed plugging individual microvessels, dilation of sinusoids may just be the result of passive distension caused by outflow blockade. Analysis of hepatic tissue at 8 weeks after cryothermia did not reveal regeneration and microvascular remodeling, but loss of hepatic tissue, which corresponded well with the tissue area presenting with sinusoidal perfusion failure during the initial observation period after cryothermia. The fact that there was no recovery of sinusoidal perfusion over the initial 2-hour observation period, but loss of tissue after 8 weeks, supports the view that cryothermia induces injury not only by direct low-temperature-mediated action, but also through ischemia caused by irreversible deterioration of the microcirculation.

Animals↗
PubMed1999

In vivo analysis of microcirculation following closed soft-tissue injury.

Major loss of tissue is an almost invariable consequence of severe closed soft-tissue injury. Clinically, the extent of soft-tissue trauma determines the outcome of complex injuries and significantly influences bone healing. With use of a new animal model, this study quantitatively analyzed microcirculation, i.e., nutritive perfusion and leukocyte-endothelial cell interaction, in skeletal muscle after standardized closed soft-tissue injury. By means of a computer-assisted controlled-impact technique, a severe standardized closed soft-tissue injury was induced in the left hindlimb of 28 rats. The rats were assigned to four experimental groups (n = 7 per group) that differed by time of analysis (1.5, 24, 72, and 120 hours after injury); rats that were not injured served as controls (n = 7). Intramuscular pressure was measured, and microcirculation in the rat extensor digitorum longus muscle was analyzed by in vivo fluorescence microscopy, which allowed assessment of microvascular diameters, functional capillary density, number of rolling and adherent leukocytes in venules, and microvascular permeability. Edema weight gain was quantified by the ratio of wet to dry weight of the extensor digitorum longus muscle. Microvascular perfusion of the skeletal muscle was characterized by a significant reduction in functional capillary density, which was paralleled by an increase in capillary diameter throughout the 120 hours of observation when compared with the controls. Trauma-induced inflammatory response was reflected by a markedly increased rolling and adherence of leukocytes, primarily restricted to the endothelium of postcapillary venules; this was accompanied by increased microvascular permeability, indicative of a substantial loss of endothelial integrity. The microcirculation surrounding the core of the damaged tissue area resembled that of ischemia-reperfusion injury in skeletal muscle, i.e., heterogeneous capillary perfusion, pronounced microvascular leakage, and adherence of leukocytes. Enhanced vascular leakage and leukocyte adherence (24-72 hours after injury) coincided with the maximum intramuscular pressure (which was not indicative of compartment syndrome) and edema formation. These results demonstrate that initial changes, leading to ultimate tissue death, after closed soft-tissue injury are caused on the microcirculatory level. This standardized model provides further insight into microvascular pathophysiology and cellular interactions following closed soft-tissue injury. Thus, it is an adequate tool for testing novel therapeutic interventions.

Animals↗
PubMed1999

Effects of cyclosporine A on the process of vascularization of freely transplanted islets of Langerhans.

We studied in vivo the effect of cyclosporine A (CsA) on both pancreatic islet vascularization and microvascular perfusion using intravital fluorescence microscopy and the dorsal skinfold chamber model in Syrian golden hamsters. Syngeneic transplantation was performed in order to exclude allograft- or xenograft-induced microvascular alterations. To study the effect of CsA on islet angiogenesis and vascularization, animals received 20 mg/kg CsA daily from day 0 until day 14 after transplantation (group A). To study toxic effects of CsA on islet microcirculation, the grafts were allowed to vascularize without immunosuppression, and 20 mg/kg CsA was given daily from day 10 until day 20 after transplantation (group B). Quantitative analysis of the process of islet vascularization in group A revealed a functional capillary density (FCD) of 515.6+/-72.7 cm(-1) at day 6 after transplantation without further increase until day 14 (504.3+/-16.7 cm(-1)). Islet transplants which were not treated with CsA during the process of angiogenesis/vascularization (group B) demonstrated a slightly but significantly (P<0.05) higher FCD (604.7+/-42.5 cm(-1)) at day 14 after transplantation, indicating slightly improved vascularization when compared to transplants of group A. Additional CsA treatment of these islet grafts until day 20 did not induce derangements of microvascular perfusion (601.2+/-67.0 cm(-1)), indicating that the immunosuppressive, drug has no toxic/detrimental effects on the transplants nutritional blood supply. We conclude that CsA only slightly alters the process of final vascularization of freely transplanted islets, and does not deteriorate nutritive perfusion of completely vascularized grafts.

Animals↗
PubMed1999

Exocrine, but not endocrine, tissue is susceptible to microvascular ischemia/reperfusion injury following pancreas transplantation in the rat.

While post-transplant pancreatitis is still a frequently occurring complication of whole pancreas transplantation, dysfunction of the endocrine tissue is rarely observed. Given that microcirculatory disorders play a major role in the pathogenesis of pancreatitis, we hypothesized a dissociation of endocrine and exocrine microvascular control in pancreas transplantation (cold ischemia-reperfusion) and studied this dissociation quantitatively, analyzing the pancreatic microcirculation after heterotopic isogeneic pancreaticoduodenal transplantation in rats by means of fluorescence microscopy. Functional capillary density (FCD) of both exocrine and endocrine tissue of pancreatic grafts after 1 h of cold storage in HTK solution did not differ when compared to sham-operated, time-matched controls. Intermittent capillary perfusion, which is absent under sham control conditions and which is proposed to be operative as a compensatory mechanism to counteract malperfusion, was observed in 52% of the exocrine, but in only 8% of the endocrine, tissue studied (p < 0.05). In contrast, cold storage of pancreatic grafts for 6 h in HTK resulted in a complete loss of intermittent capillary perfusion in exocrine tissue and, consequently, marked exocrine perfusion failure (decrease in FCD), while FCD of pancreatic endocrine tissue was preserved without any significant change in the incidence of intermittent capillary perfusion. Thus, our results indicate a higher susceptibility of the exocrine pancreas to cold ischemia/reperfusion events that is associated with significant alterations in nutritive perfusion and, thus, with limitations of the oxygen supply to the tissue. This may lead to inflammatory tissue reactions in the clinical setting of pancreas transplantation.

Animals↗
PubMed1999

Angiogenesis and microvascularization after cryothermia-induced myocardial infarction: a quantitative fluorescence microscopic study in rats.

OBJECTIVE: Microvascularization of infarcted myocardial tissue may be a prerequisite for successful therapeutic interventions, including cardiomyoblast or satellite cell transplantation. Because little is known on microvascular restitution within infarcted tissue, we studied angiogenesis and microvascularization after cryothermia-induced myocardial infarction using intravital fluorescence microscopic techniques. METHODS: In anesthetized, orally intubated and ventilated Sprague-Dawley rats (n = 20), a sternotomy was performed and a standardized cryolesion was induced to the right ventricle by freezing for 5 min to -160 degrees C. Myocardial angiogenesis and microvascularization were analyzed quantitatively after rethoracotomy on days 7 (n = 6) or 28 (n = 8). Sham-operated animals (n = 6) served as controls. RESULTS: Seven days after cryothermia, the central tissue area of the injured myocardium (28.4 +/- 9.2 mm2) was characterized by complete lack of capillary perfusion, while the periphery of the cryolesion (27.6 +/- 5.7 mm2) revealed a heterogeneous capillary perfusion pattern with a density of 300.9 +/- 38.9 cm-1. Adjacent myocardial tissue showed intact capillary perfusion (density: 563.0 +/- 44.4 cm-1) comparable with that of sham-operated controls. After 28 d the area with lack of capillary perfusion was found significantly reduced to 7.3 +/- 3.7 mm2 (P < 0.05); however, it was still surrounded by a heterogeneously perfused area of myocardial tissue of 57.7 +/- 19.2 mm2 (density: 271.1 +/- 52.7 cm-1), indicating partial restitution of capillary perfusion. Although at day 7 within the central zone of the cryolesions, capillary perfusion was completely shut down, perfusion of microvessels larger than capillaries, i.e., arterioles and venules, were found maintained, however, with a density markedly lower (1.96 +/- 1.04 mm-1) when compared with that of sham-controls (4.28 +/- 1.52 mm-1). After 28 d the number of these larger-sized microvessels increased significantly with values of density even higher compared with those observed in controls (6.89 +/- 1.71 mm-1; P < 0.05), indicating new vessel formation. CONCLUSIONS: Our study indicates partial restitution and function of the microvascular network within infarcted myocardial tissue, which may serve as an appropriate prerequisite for successful application of novel therapeutic strategies to improve myocardial function.

Animals↗
PubMed1999

Differential gene expression of CINC, NOS II, and ICAM-1 in endotoxemic liver cells by rG-CSF.

INTRODUCTION: We have recently demonstrated that recombinant granulocyte colony-stimulating factor (rG-CSF) modulates lipopolysaccharide (LPS)-induced Kupffer cell activation with subsequent reduction in hepatic leukocyte-endothelial cell interaction, thereby achieving protection against microcirculatory perfusion failure and hepatic dysfunction. To further clarify the underlying mechanisms, rG-CSF treated liver cells were tested for the LPS-induced gene expression of cytokine-induced neutrophil chemoattractant (CINC) and intercellular adhesion molecule-1 (ICAM-1) as potential chemotactic and leukocyte-recruiting factors and for the gene expression of inducible nitric oxide synthase (NOS II) as potential modulator of leukocyte adherence. METHODS: Using a collagenase, DNAse/pronase digestion technique, hepatic parenchymal and nonparenchymal cell fractions were obtained from livers of in vivo rG-CSF pretreated Sprague-Dawley rats 2 h after LPS exposure. mRNA transcripts were assessed using northern blot analysis. RESULTS: In control livers only ICAM-1 mRNA was found constitutively expressed in hepatic nonparenchymal cells. rG-CSF per se did not affect NOS II, CINC, or ICAM-1 expression in hepatic liver cells, while LPS induced a marked expression of NOS II, CINC, and ICAM-1 in nonparenchymal cells and, to a lesser extent, in hepatocytes. Administration of rG-CSF prior to LPS exposure tended to increase NOS II, CINC, and ICAM-1 mRNA transcripts in hepatocytes. In nonparenchymal cells, however, NOS II and CINC were found reduced in rG-CSF pretreated animals upon LPS exposure. CONCLUSIONS: The present data show a strikingly different cell type specific pattern of inflammatory response genes in rG-CSF-modulated hepatic endotoxemia. Reduced expression of NOS II, in particular of CINC, in the nonparenchymal cell fraction may contribute to the reduced leukocyte adherence and thus attenuation of cell-dependent tissue injury in rG-CSF pretreated endotoxemic animals.

Animals↗
PubMed1999

Effectiveness of a hands-on training course for laparoscopic spine surgery in a porcine model.

BACKGROUND: Although it is widely proposed that surgeons, before introducing a novel laparoscopic technique in man, should practice in an appropriate animal model for acquisition of the necessary technical skills, the effectiveness of those hands-on training courses are rarely documented. METHODS: In 1995 we have organized eight hands-on training courses for laparoscopic anterior interbody spine fusion in an in vivo porcine model. A total of 72 colleagues from 50 different centers of 12 countries participated, including orthopedic, trauma, visceral, neuro-, and vascular surgeons. Quality and effectiveness of the course were evaluated by a questionnaire after a 1.5- to 2.5-year period. RESULTS: During this time, 42.2% of the participating centers had applied the new technique successfully in man. Centers which participated in the course with a team that included a skilled laparoscopic surgeon and an orthopedic or trauma surgeon introduced the technique more frequently to clinical practice (57.9%) than those represented by only one participant (30. 8%). Moreover, there was a tendency toward a more frequent introduction of the technique to clinical practice in centers associated with university hospitals (57.1% vs. 29.2%), indicating the requirement of a particular infrastructure for this complex interdisciplinary procedure. Almost all participants (98.3%) agreed that for novel surgical techniques requiring advanced technical skills, there should first be training in a large animal model before the technique is applied in man. CONCLUSIONS: Complex laparoscopic procedures (i.e., laparoscopic spine surgery) can be successfully learned by in vivo hands-on training courses. We propose that for refinements and modifications of the technique (e.g. , the lumboscopic approach), there should also first be training in a large animal model before these are applied in man.

Animals↗
PubMed1999

Inhibition of tumor growth, angiogenesis, and microcirculation by the novel Flk-1 inhibitor SU5416 as assessed by intravital multi-fluorescence videomicroscopy.

Vascular endothelial growth factor (VEGF) plays a fundamental role in mediating tumor angiogenesis and tumor growth. Here we investigate the direct effect of a novel small molecule inhibitor of the Flk-1-mediated signal transduction pathway of VEGF, SU5416, on tumor angiogenesis and microhemodynamics of an experimental glioblastoma by using intravital multifluorescence videomicroscopy. SU5416 treatment significantly suppressed tumor growth. In parallel, SU5416 demonstrated a potent antiangiogenic activity, resulting in a significant reduction of both the total and functional vascular density of the tumor microvasculature, which indicates an impaired vascularization as well as significant perfusion failure in treated tumors. This malperfusion was not compensated for by changes in vessel diameter or recruitment of nonperfused vessels. Analyses of the tumor microcirculation revealed significant microhemodynamic changes after angiogenesis blockage such as a higher red blood cell velocity and blood flow in remnant tumor vessels when compared with controls. Our results demonstrate that the novel antiangiogenic concept of targeting the tyrosine kinase of Flk-1/KDR by means of a small molecule inhibitor represents an efficient strategy to control growth and progression of angiogenesis-dependent tumors. This study provides insight into microvascular consequences of Flk-1/KDR targeting in vivo and may have important implications for the future treatment of angiogenesis-dependent neoplasms.

Animals↗
PubMed1999

Secondary ischaemia in experimental free flaps--treatment by long acting prostacyclin analogues.

Secondary postoperative ischaemia due to venous occlusion is the most detrimental insult to free microvascular flaps. In an experimental rat free flap model the efficacy of long acting prostacyclin analogues iloprost (Ilomedin) and cicaprost in venous occlusion induced postoperative ischaemia was studied. Free, microvascular groin flaps were transplanted to the neck and the draining veins were temporarily occluded on the first postoperative day for a total of 20 min. In the untreated control group, haemorrhagic flap necrosis occurred. Intravital microscopy after secondary ischaemia revealed flap areas without reperfusion. The functional vessel density was significantly reduced. Reperfused capillaries were tortuous and significantly dilated. After reperfusion the interstitial leakage of macromolecular dextran increased, indicating loss of microvascular endothelial integrity. Intraarterial and intravenous applications of iloprost were able to diminish the ischaemic effects, giving a flap survival rate of 83%. Similar results were obtained by intravenous and enteral administration of cicaprost. Transcutaneous oxygen partial pressure measurements confirmed the viability of the surviving flaps. We conclude that both iloprost and cicaprost are effective in preventing venous occlusion induced failure of free microvascular groin flaps.

Animals↗
PubMed1999

In vivo analysis of the microcirculation of osteomyocutaneous flaps using fluorescence microscopy.

Previous studies have indicated that freely transferred osteomyocutaneous flaps may fail despite anastomotic patency. While microvascular dysfunction is thought to be one of the major causes for this type of flap failure, little is known of its underlying mechanisms, probably due to the lack of adequate experimental models allowing detailed intravital microcirculatory analysis. Herein we report quantitative analysis of the microcirculation of periosteum, muscle, subcutis and skin by intravital fluorescence microscopy using an osteomyocutaneous free flap model in the hindlimb of rats. The microcirculation of the different tissues was studied after microanastomotic transfer (free flap), and was compared to that after solely elevating the tissue, mimicking a pedicled osteomyocutaneous flap. Transferred flaps, which were exposed to 1 h of ischaemia during the anastomotic procedure, showed a slight but significant decrease (P< 0.05) of functional capillary density in muscle, subcutis and skin when compared with the microcirculation of pedicled flaps, while capillary diameters, red blood cell velocity and blood flow of perfused capillaries remained almost unaffected. The decrease of functional capillary density was associated by a significant (P< 0.05) inflammatory response, as indicated by the increased number of leukocytes adherent to the endothelial lining of postcapillary venules. While the functional capillary density of periosteum was not affected by the free transfer procedure, the inflammatory response was found similar when compared with that observed in muscle and subcutis. Thus, our study indicates that even after a short 1-h ischaemic time period, capillary perfusion failure and leukocyte-endothelial cell interaction are the main events, characterising microvascular dysfunction after free transfer of osteomyocutaneous flaps. Using the model described herein, intravital microscopic analysis of the microcirculation proved an appropriate tool to study the individual microvascular response after free tissue transfer, and may thus be used to evaluate the effectiveness of novel therapeutic regimens which aim at counteracting microcirculatory dysfunction in free osteomyocutaneous flaps.

Animals↗
PubMed1999

Cardiopulmonary dysfunction during minimally invasive thoraco-lumboendoscopic spine surgery.

UNLABELLED: The endoscopic retroperitoneal approach to thoracolumbar anterior spine fusion is associated with CO2 insufflation into the thoracic space. We studied the cardiopulmonary effects of this CO2 thoraco-retroperitoneal insufflation compared with the conventional open surgical procedure using thoraco-phreno-lumbotomy in 12 pigs under balanced anesthesia, paralysis, and mechanical ventilation. During open surgery of the thoracolumbar spine, animals exhibited unchanged systemic and pulmonary hemodynamics, as well as ventilation and oxygenation variables. Animals retroperitoneally insufflated with CO2 (12 mm Hg) exhibited a significant increase of PaCO2 and a moderate decrease of PaO2, SaO2, and pH, with insignificant changes of central venous filling pressures and systemic hemodynamics. Endoscopic phrenotomy with thoracic CO2 insufflation instantaneously and drastically affected hemodynamic status and pulmonary gas exchange with marked hypoxia, hypercapnia, systemic hypotension, tachycardia, and pulmonary hypertension within minutes. An increase of minute ventilation, inspiratory oxygen fraction, and positive end-expiratory pressure promptly reversed these cardiopulmonary effects. CO2 evacuation allowed the animals to completely recover and regain almost baseline cardiopulmonary status, except for a reduced arterial blood pressure. Appropriate monitoring and immediate CO2 desufflation may be beneficial in cases of therapy-resistant hemodynamic, oxygenation, and ventilation difficulties. IMPLICATIONS: For endoscopic thoraco-lumbar spine fusion, CO2 thoraco-retroperitoneum-induced cardiopulmonary dysfunction must be of concern, especially in patients with cardiopulmonary compromise. Appropriate monitoring and immediate CO2 desufflation may be beneficial in cases of therapy-resistant hemodynamic, oxygenation, and ventilation difficulties.

Animals↗