Microvascular Clamp Research Articles

Protective effect of sulfhydryl‐containing antioxidants against ischemia/reperfusion injury of prepubertal rat intestine

Reactive oxygen species generated during reperfusion of the tissue are known to play an important role in the basic pathophysiology of ischemia/reperfusion (I/R) injury. The aim of this study was to investigate and compare the protective effects of three sulfide-based antioxidants, N-acetylcysteine (NAC), erdosteine (ERD), and alpha-lipoic acid (LA), on I/R injury of the small intestine tissue. Forty male Sprague-Dawley rats weighing between 100-150 g were divided into five groups (n = 8 for each): control (sham operated), I/R, I/R + NAC, I/R + ERD, and I/R + LA. Intestinal ischemia was provided by occluding the superior mesenteric artery via a special microvascular clamp; ischemia for 30 min and reperfusion for 3 days were carried out. Ileal specimens were obtained to determine the tissue levels of malondialdehyde (MDA), protein carbonyl contents (PCO), superoxide dismutase (SOD), and glutathione peroxidase (GPx) activities and histological changes. The rats subjected to intestinal I/R exhibited an increase in tissue MDA and PCO; the levels could hardly be ameliorated in the treatment groups. SOD and GPx activities were significantly decreased in the I/R group, whereas their reduction was less expressed in the treatment groups. Additionally, the histopathological injury scores of the disulfide-treated groups were lower than those of the I/R group. All of the sulfhydryl-containing antioxidants used in this study exhibited a significant role in attenuating intestinal I/R injury; however, the outcome of the LA-treated group was significantly marked than that of the others.

Pitavastatin prevents intestinal ischemia/reperfusion–induced bacterial translocation and lung injury in atherosclerotic rats with hypoadiponectinemia

Atherosclerosis with hypoadiponectinemia can be further aggravated by intestinal ischemia/reperfusion (II/R)-induced injuries, such as bacterial translocation and lung injury. We investigated the effect of statin administration on the risk of II/R-induced injury in atherosclerotic rats with hypoadiponectinemia. Wistar rats were divided into 4 groups: (1) the Normal group (normal diet), (2) the Chol group (2% high cholesterol diet), (3) the St-1w group, and (4) the St-2w group (Chol group plus pitavastatin administration for 1 or 2 weeks, respectively). The serum concentrations of lipids and adiponectin were measured preoperatively. After midline laparotomy (time, T0), the superior mesenteric artery was occluded with a microvascular clamp for 30 min, followed by 360 min of reperfusion (T1). Intestinal and lung nitric oxide (NO) concentrations were measured. Intestinal injury was assessed by microcirculatory flow, histology, and permeability. Bacterial translocation was assessed by analysis of serum peptidoglycan concentration. Lung injury was assessed by histologic examination, pulmonary permeability index, and wet/dry lung weight ratio. The 2-week administration of statins with high-cholesterol feeding (St-2w group) improved hypoadiponectinemia to levels similar to those of the Normal group. Intestinal and lung NO concentrations were significantly lower at T1 in the Normal and St-2w groups than in the Chol group. Statin administration improved poor recovery of intestinal microcirculatory flow in the Chol group. At T1, intestinal and lung injuries were significantly aggravated and serum peptidoglycan concentration was significantly elevated in the Chol group compared with the Normal and St-2w groups. The 1-week administration of statins had no significant influence on serum adiponectin levels, tissue NO concentration, or tissue injury. Administration of pitavastatin reduces the risk of II/R-induced injury in atherosclerotic rats with hypoadiponectinemia by improving hypoadiponectinemia and inhibiting inducible NO synthase-produced NO. Furthermore, preoperative improvement of hypoadiponectinemia may be important as an index of the protective effect of pitavastatin for II/R-induced injury in atherosclerotic rats with hypoadiponectinemia.

Hyperbaric oxygenation preconditioning induces skin flap ischaemia tolerance in a rat model

Objective To study the effect of preconditioning hyperbaric oxygenation on skin flap is-ehaemia tolerance. Methods 18 male SD rats were divided into the control and HBO preconditioning groups. In control group, an extended epigastrie adipocutaneous flap was raised, based on the right su-perficial epigastric artery and vein. 3-hours flap ischemia was induced by clamping the pedicle vessels with microvascular clamp. At the end of ischemia induction, the clamp was removed and the flap was sutured back. Rats in HBO preconditioning group were treated with HBO two days before operation. Flap surger-y began 1 hour after the last HBO treatment. The operation was the same as the control group. On the fifth postoperative day, the condition of the flap was recorded with transparent paper. Mean flap necrosis area was calculated with Acrobat software. Data were analyzed with SPSS software. Results The aver-age designed flap area was (51.59±6.62)cm2 and (52.71±2.05)cm2 in the control group and the HBO preconditioning group. The average flap survival area was (7.38±2.49)cm2 and (15.82±5.95)cm2. The difference was significant between the control and HBO preconditioning groups (t= 4. 14, P<0.01) in average flap survival area. Conclusion HBO preconditioning can rise flap ischaemia tolerance and enhance flap survival. Key words: Hyperbaric oxygen; Skin flap; Ischemia preconditioning; Ischemia tolerance

Evaluation of a Novel Reverse Thermosensitive Polymer for Use in Microvascular Surgery

Microvascular clamps have several potential shortcomings, including the risk of vessel injury. LeGoo, a novel reverse thermosensitive polymer (Pluromed Inc., Woburn, MA), is investigated as a substitute to vascular clamping in a microsurgical model and the technical details are described. Femoral vessels of Sprague Dawley rats were used to evaluate the usefulness of this polymer for performing end-to-end arterioarterial (AA), venovenous (VV), and end-to-side arteriovenous (AV) microvascular anastomoses. The ability to obtain and maintain hemostasis was assessed. Secondary endpoints, including polymer volume, concentration, temperature, infusion technique, ability to reinfuse, blood vessel stenting effect, polymer dissolution characteristics, and reestablishment of flow, were also noted. Initial hemostasis occurred in every case. Mean duration of efficacy (hemostasis) after initial injection was 17.8 minutes (4 minutes to 44.5 minutes) for AA anastomoses and 31.8 minutes (13 minutes to 46 minutes) for VV anastomoses. Mean volume of polymer initially injected was 0.11 mL (0.01 mL to 0.20 mL) and 0.07 mL (0.06 mL to 0.10 mL) for AA and AV arteries, respectively, and 0.14 mL (0.10 mL to 0.20 mL) and 0.20 mL (0.15 mL to 0.27 mL) for VV and AV veins. Use of LeGoo in veins was clearly superior to arterial use with regard to the technical aspects of injecting LeGoo and reestablishing hemostasis, as well as greater vessel stenting effect and less vessel retraction. This novel polymer showed promise for its ability to allow for hemostasis while performing microvascular anastomoses. Improvements were made with regard to injection techniques, appropriate volumes, ability to reliably determine gel plug dissolution, and final vessel patency. Preliminary results demonstrate that this polymer may be a viable substitute for microvascular clamps.

Intestinal ischemia/reperfusion-induced bacterial translocation and lung injury in atherosclerotic rats with hypoadiponectinemia

Intestinal ischemia/reperfusion causes intestinal mucosal injury, which may result in bacterial translocation (BT) and multiple organ failure. Lung injury is a common complication after intestinal ischemia/reperfusion. Adiponectin is an antiinflammatory adipokine, and it plays an important role in the development of metabolic syndrome in hypoadiponectinemia. In atherosclerosis with hypoadiponectinemia, BT also may aggravate injuries induced by intestinal ischemia/reperfusion. Wistar rats were divided into 3 groups: Normal group (normal diet), Chol group (2% high cholesterol diet), and Chol+1400W group (Chol group plus 1400W, an inducible nitric oxide [iNOS] inhibitor, at 1 mg/kg intraperitoneally 30 minutes preoperatively). The serum concentrations of lipids and adiponectin and vascular responses were measured. After midline laparotomy (time, T0), the superior mesenteric artery was occluded with a microvascular clamp for 30 minutes, followed by 360 minutes of reperfusion (T1). Intestinal injury was assessed from microcirculatory flow, histology, serum diamine oxidase activity, and permeability. Lung injury was assessed by histology, pulmonary permeability index (PPI), and wet-to-dry lung weight (W/D) ratio. Intestinal and lung nitric oxide (NO) concentrations were also measured. BT was assessed by serum peptidoglycan (PG) concentration. The Chol and Chol+1400W groups developed hyperlipidemia and hypoadiponectinemia; the 2 groups also had vascular endothelial dysfunction without histological changes, indicating early atherosclerosis. These groups also showed poor recovery of intestinal microcirculatory flow at T1. The serum diamine oxidase activity, histological intestinal damage, and permeability were elevated at T1 in the Chol group; however, these findings were not significant in the Normal and Chol+1400W groups. Histological lung damage and lung PPI and W/D ratio were increased only in the Chol group. Intestinal and lung NO concentrations were significantly elevated at T1 in the Chol group. The serum PG concentration was elevated significantly in the Chol group. In atherosclerotic rats with hypoadiponectinemia, intestinal microcirculatory flow does not recover adequately after intestinal ischemia/reperfusion because of endothelial dysfunction. Atherosclerosis with hypoadiponectinemia increased the incidence of BT further by aggravating intestinal mucosal injury and, moreover, it aggravated lung injury. Although inhibition of iNOS does not lead to adequate recovery of intestinal microcirculatory flow, it reduces injury by decreasing the amount of NO derived from high enzymatic iNOS activity in the intestine.

Successful pregnancy after whole ovary microvascular transplantation

OBJECTIVE: Cortical grafting for ovary transplantation has been robustly successful, but results in dramatic decrease in oocyte numbers. Microvascular transplantation of the whole ovary may obviate the problem of ischemic follicle loss.DESIGN: Single case report of initial attempt at intact whole ovary microvascular transplantation in the human.MATERIALS AND METHODS: A 38 year-old pair of monozygotic twins requested ovary transplantation because although one of them had normal ovarian function and two children, the other had undergone premature ovarian failure (POF) at age 15. Her FSH level was 81 m/IU/ml and she had a history of amenorrhea for 22 years. The donor ovary was removed via laparoscopy by dividing the ligament at its base to obtain maximum length, while the recipient infundibulopelvic ligament was transected close to the ovary (after first securing with microvascular clamps) via minilaparotomy. The donor ovarian veins (3.0mm diameter) were anastomosed to the recipient's ovarian veins with 9-0 nylon interrupted sutures, and the ovarian arteries (0.5mm diameter) were anastomosed with 10-0 nylon interrupted sutures.RESULTS: Normal blood flow was immediately observed through the ovarian vessels of the transplanted ovary. The recipient's first menstruation in 22 years occurred on day 101 after transplantation and her day 3 FSH level dropped to 7.4 mIU/ml (the same as her sister) by day 158. Ultrasound revealed normal blood flow to the transplanted ovary and normal follicular development. She had normal, regular menstrual cycles until by day 427 her home pregnancy test was positive, and her beta-HCG was 174. A healthy pregnancy ensued. Her 7, 10, and 12-week scans for prenatal evaluation were completely normal with good interval growth and fetal heartbeat of 170. A healthy pregnancy ensued. Follow-up bone scans one and a half years post-op showed continuing resolution of her osteoporosis.CONCLUSIONS: To our knowledge, this is the first successful human intact whole ovary transplant leading to healthy pregnancy, now approaching term. The low serum FSH suggested minimal effects of the brief ischemia on ovarian reserve. The delay of 101 days (3 months) until the first menstruation precisely supports the theories of Gougeon on the dynamics of follicular growth in humans, i.e., that it requires 85 days for eggs in primordial follicles leaving their resting phase to reach sufficient maturity to enter the menstrual cycle and ovulate. OBJECTIVE: Cortical grafting for ovary transplantation has been robustly successful, but results in dramatic decrease in oocyte numbers. Microvascular transplantation of the whole ovary may obviate the problem of ischemic follicle loss. DESIGN: Single case report of initial attempt at intact whole ovary microvascular transplantation in the human. MATERIALS AND METHODS: A 38 year-old pair of monozygotic twins requested ovary transplantation because although one of them had normal ovarian function and two children, the other had undergone premature ovarian failure (POF) at age 15. Her FSH level was 81 m/IU/ml and she had a history of amenorrhea for 22 years. The donor ovary was removed via laparoscopy by dividing the ligament at its base to obtain maximum length, while the recipient infundibulopelvic ligament was transected close to the ovary (after first securing with microvascular clamps) via minilaparotomy. The donor ovarian veins (3.0mm diameter) were anastomosed to the recipient's ovarian veins with 9-0 nylon interrupted sutures, and the ovarian arteries (0.5mm diameter) were anastomosed with 10-0 nylon interrupted sutures. RESULTS: Normal blood flow was immediately observed through the ovarian vessels of the transplanted ovary. The recipient's first menstruation in 22 years occurred on day 101 after transplantation and her day 3 FSH level dropped to 7.4 mIU/ml (the same as her sister) by day 158. Ultrasound revealed normal blood flow to the transplanted ovary and normal follicular development. She had normal, regular menstrual cycles until by day 427 her home pregnancy test was positive, and her beta-HCG was 174. A healthy pregnancy ensued. Her 7, 10, and 12-week scans for prenatal evaluation were completely normal with good interval growth and fetal heartbeat of 170. A healthy pregnancy ensued. Follow-up bone scans one and a half years post-op showed continuing resolution of her osteoporosis. CONCLUSIONS: To our knowledge, this is the first successful human intact whole ovary transplant leading to healthy pregnancy, now approaching term. The low serum FSH suggested minimal effects of the brief ischemia on ovarian reserve. The delay of 101 days (3 months) until the first menstruation precisely supports the theories of Gougeon on the dynamics of follicular growth in humans, i.e., that it requires 85 days for eggs in primordial follicles leaving their resting phase to reach sufficient maturity to enter the menstrual cycle and ovulate.

Inhibition of apoptosis by flaxseed in a mouse model of lung ischemia reperfusion injury

Latif, Jawad M. MD; Li, Xiaogjui PhD; Afthinos, John MD; Colanta, Agnes MD; Balderacchi, Jasminka MD; Todd, George J. MD; Belsley, Scott MD; Connery, Cliff P. MD; Christofidou, Melpo PhD; Bhora, Faiz Y. MD Author Information

NAD(P)H oxidase-derived peroxide mediates elevated basal and impaired flow-induced NO production in SHR mesenteric arteries in vivo

Nitric oxide (NO) and reactive oxygen species (ROS) have fundamentally important roles in the regulation of vascular tone and remodeling. Although arterial disease and endothelial dysfunction alter NO and ROS levels to impact vasodilation and vascular structure, direct measurements of these reactive species under in vivo conditions with flow alterations are unavailable. In this study, in vivo measurements of NO and H2O2 were made on mesenteric arteries to determine whether antioxidant therapies could restore normal NO production in spontaneously hypertensive rats (SHR). Flow was altered from approximately 50-200% of control in anesthetized Wistar-Kyoto rats (WKY) and SHR by selective placement of microvascular clamps on adjacent arteries while NO and H2O2 were directly measured with microelectrodes. Relative to WKY, SHR had significantly increased baseline NO and H2O2 concentrations (2,572 +/- 241 vs. 1,059 +/- 160 nM, P < 0.01; and 26 +/- 7 vs. 7 +/- 1 microM, P < 0.05, respectively). With flow elevation, H2O2 but not NO increased in SHR; NO but not H2O2 was elevated in WKY. Apocynin and polyethylene-glycolated catalase decreased baseline SHR NO and H2O2 to WKY levels and restored flow-mediated NO production. Suppression of NAD(P)H oxidase with gp91ds-tat decreased SHR H2O2 to WKY levels. Addition of topical H2O2 to increase peroxide to the basal concentration measured in SHR elevated WKY NO to levels observed in SHR. The results support the hypothesis that increased vascular peroxide in SHR is primarily derived from NAD(P)H oxidase and increases NO concentration to levels that cannot be further elevated with increased flow. Short-term and even acute administration of antioxidants are able to restore normal flow-mediated NO signaling in young SHR.

Antioxidant and protective effects of silymarin on ischemia and reperfusion injury in the kidney tissues of rats

Renal ischemia/reperfusion (I/R) injury is a major cause of acute renal failure. Silymarin is extracted from Silybum marianum and Cynara cardunculus seeds and fruits. The aim of this study is to investigate whether silymarin administration prevents the damage induced by I/R in rat kidneys. Thirty male Wistar rats were randomly divided into five experimental groups (n = 6, each) as follows; control group, sham-operated group, I/R group, silymarin group, and I/R + silymarin group. In the I/R and I/R + silymarin groups, both renal arteries were occluded using nontraumatic microvascular clamps for 45 min. Then, at the end of 24 h of reperfusion, the animals were killed. Kidney function tests, the serum and tissue antioxidant enzymes and oxidant products were determined. Animals that were subjected to I/R exhibited significant increase in serum urea, creatinine, and cystatin C levels compared with the rats treated with silymarin prior to the I/R process (P < 0.001). The serum enzymatic activities of superoxide dismutase and glutathione peroxidase significantly decreased in the I/R group; however, this reduction was significantly improved by the treatment with silymarin (P < 0.001 and P < 0.05, respectively). Renal I/R produced a significant increase in serum and tissue malondialdehyde, nitric oxide, and protein carbonyl as compared with controls. Treatment with silymarin resulted in significant reduction in these markers (P < 0.001). Based on our findings, silymarin protects the kidneys against I/R injury. This finding may provide a basis for the development of novel therapeutic strategies for protection against the damages caused by I/R.

Direct measurement of periarterial nitric oxide (NO) in resistance vessels of aged WKY rats reveals elevated basal and suppressed flow‐mediated production which is normalized by apocynin.

Abnormal regulation of the nitric oxide (NO) system may be responsible for the age‐related impairment in tissue perfusion and collateral growth. Direct, real time, in vivo measurements of NO in aging resistance vessels are not available. This study tested the hypothesis that aging is correlated with reduced basal and flow‐mediated NO production, which can be reversed by anti‐oxidant therapy. Our mesenteric model was used in young (Y) and retired breeder (RB) WKY and RB pre‐treated with apocynin (RB+Apo). NO‐ specific electrodes measured mesenteric periarterial NO simultaneously with arterial flow. After NO baseline measurement, collateral flow was varied from 50–200% of control by placement of microvascular clamps on adjacent arteries. RB had significantly increased baseline NO compared with Y (2053 ± 504 vs. 1059 ± 160 nM, p&lt; 0.05). Periarterial NO levels were altered in proportion to blood flow changes in Y but not in RB rats (Figure 1). In RB+Apo, NO baseline was reduced (760 ± 102 nM) and flow‐mediated NO production restored in RB+Apo (Figure 1). Immunoblotting showed that RB had significantly increased phospho‐eNOS levels compared to either Y or RB+Apo. This suggests that the elevated baseline and suppressed flow‐mediated NO production may result from near maximal activation of eNOS in the RB. eNOS stimulation by reactive oxygen species produced by NADPH oxidase is a mechanism to be explored.Support: HL42898 and HL20605

The Protective Effects of Intravenous Anesthetics and Verapamil in Gut Ischemia/Reperfusion-Induced Liver Injury

We investigated the protective effects of IV anesthetics and verapamil in gut ischemia/reperfusion-induced liver injury. Forty male Wistar Albino rats were randomly assigned to four groups of 10 rats each. Anesthesia was induced and maintained with propofol in Groups 1 and 3 and with thiopental in Groups 2 and 4 during the experiment. All animals developed intestinal ischemia after occlusion of the superior mesenteric artery for 30 min. Reperfusion was induced by removal of the microvascular clamp and was allowed to continue for 120 min. The animals in Groups 3 and 4 were given verapamil 10 min before reperfusion. Liver and ileum samples were taken for measurement of malondialdehyde (MDA) and histopathologic examination before ischemia and 30 and 120 min after reperfusion. Blood samples were also obtained for measurement of plasma tumor necrosis factor-alpha and interleukin-6 levels. Gut ischemia/reperfusion-induced significant increases in MDA contents of liver and gut and serum cytokines, consistent with histopathologic injury scores. Propofol effectively stabilized the MDA levels and decreased the tissue injury scores of the liver and gut. Tumor necrosis factor-alpha and interleukin-6 levels increased less in the propofol groups than in the thiopental groups. There was no additive preventive effect of verapamil on propofol. The addition of verapamil to thiopental was effective in decreasing the serum cytokines and liver MDA content. Propofol may offer advantages by inhibiting lipid peroxidation and inflammatory cytokine production in an animal model of gut ischemia/reperfusion-induced liver injury.

Melatonin reduces ischemia/reperfusion‐induced superoxide generation in arterial wall and cell death in skeletal muscle

The purpose of this study was to determine the effect of melatonin on superoxide generation in arterial wall at an early phase of reperfusion and on endothelial dysfunction of microvasculature and cell viability of cremaster muscle at late phase of reperfusion (24 hr) after prolonged ischemia. Bilateral vascular pedicles which supply blood flow to the cremaster muscle were exposed. After surgical preparation, microvascular clamps were applied on the right iliac, femoral and spermatic arteries to create 4 hr of ischemia in both feeding vessels and the unexposed cremaster muscle. The vascular clamping was omitted on the left iliac, femoral and spermatic arteries and served as an internal control. Melatonin or Vehicle was via by intravenous injection at 10 min prior to reperfusion and 10 min after reperfusion. In the first experiment, the vascular pedicle was harvested after reperfusion to measure superoxide generation in real time by lucigenin-derived chemiluminescence. In the second experiment, endothelial-dependent and -independent vasodilatation was examined in the terminal arteriole of cremaster muscle which was then harvested to examine cell viability by WST-1 assay on day 2. Superoxide generation in arterial wall peaked at first 5-min of reperfusion and declined to near baseline after 60 min of reperfusion. Melatonin treatment significantly reduced superoxide generation in arterial walls and improved cell viability in cremaster muscles. Melatonin treatment also significantly reduced microvascular endothelial dysfunction which was still observable in the microcirculation of cremaster muscle after 24 hr of reperfusion. Melatonin reduces superoxide generation in the early phase of reperfusion resulting in attenuating endothelial dysfunction and muscle cell death in the late phase of reperfusion.

Effects of purified poloxamer 407 gel on vascular occlusion and the coronary endothelium☆

Vascular occlusion during off-pump coronary surgery often results in sub-optimal visualization and endothelial damage of the target vessel. We have previously reported the safety of purified poloxamer 407, a gel with reverse thermosensitive properties, in a model of off-pump coronary occlusion. The aim of this study was to evaluate different gel concentrations and their effects on coronary occlusion time, myocardial contractility, endothelial function, and markers of myocardial injury and apoptosis. Yorkshire swine (30-35 kg) underwent sternotomy and mid-LAD occlusion using either microvascular clamps (n=6) or varying quantities of three different concentrations (20%; n=6, 22.5%; n=3, and 25%; n=3) of purified poloxamer 407 gel. Distal LAD flow, left ventricular pressure, and in vitro microvascular reactivity were assessed. Molecular markers of myocardial injury and apoptosis were assessed using Western blotting. Duration of ischemia correlated significantly with the amount of injected gel for the 20% and 22.5% formulations (Spearman r=0.64, p=0.02 and r=0.85, p=0.03, respectively) but not for the 25% gel (r=0.22, p=0.66). There were no significant differences in LV contractility (maximum+dp/dt) (p=0.86) as well as LAD flow (p=0.25) during reperfusion in the four groups. Microvessel relaxation to adenosine diphosphate in the ischemic territory was impaired with higher concentrations of the gel, 22.5% (-14.8+/-7.5% vs control at 10(-5)mol/L, p<0.05) and 25% gel (-24.0+/-7.6% vs control at 10(-5)mol/L, p<0.001) but not with the 20% gel. Endothelium-independent relaxation to sodium nitroprusside was preserved in all groups. Cleaved poly(ADP-ribose) polymerase, a marker of myocardial injury and apoptosis, was elevated in the ischemic myocardium in all groups (p=0.02 vs non-ischemic myocardium) with no significant differences between the groups (p=0.70). Phosphorylation of Bad, an anti-apoptotic protein, was significantly reduced in the ischemic territory (p=0.04). No changes were observed in other markers of myocardial apoptosis. Purified poloxamer 407 gel is effective for temporary coronary vascular occlusion. Coronary artery occlusion time is related to gel concentration and the quantity of gel injected. The higher gel concentrations may cause endothelial dysfunction of the distal vasculature and therefore should be avoided.

Parotid Duct Repair by Use of an Embolectomy Catheter with a Microvascular Clamp

Department of Plastic and Reconstructive Surgery, Uludağ University Faculty of Medicine, Bursa, Turkey Correspondence to Dr. Etöz, Uludağ Üniversitesi, Tıp Fakültesi, Plastik ve Rekonstrüktif Cerrahi A.D., 16059 Görükle, Bursa, Turkey, [email protected]

Safety and Efficacy of a Novel Gel for Vascular Occlusion in Off-Pump Surgery

Coronary occlusion techniques used during off-pump coronary artery bypass surgery often provide suboptimal visualization and can damage the endothelium. We evaluated a novel gel with reverse thermosensitive properties for internal vessel occlusion during off-pump coronary artery bypass surgery. Yorkshire pigs (n = 6 per group) underwent two cycles of mid-left anterior descending coronary artery (LAD) occlusion using the gel (injected into the artery) or microvascular clamps (control group) followed by 30 minutes of reperfusion. Regional wall motion and LAD flow were monitored, microvessel relaxation responses were evaluated, and myocardial tissue was analyzed histologically. Complete left anterior descending coronary artery occlusion was successfully achieved using the gel (median ischemic time, 14 minutes; range, 4.5 to 24 minutes). Anterior wall motion abnormalities as well as flow patterns in the reperfused left anterior descending coronary artery were similar in both groups. Microvessel relaxation to substance P was mildly impaired (-11.7 +/- 2.8% vs control; p < 0.001) in the left anterior descending coronary artery territory, but response to adenosine diphosphate and sodium nitroprusside was unaffected. Mild contraction band necrosis was present in both groups, consistent with mild ischemia-reperfusion injury. The gel represents a safe and effective method of vessel occlusion with a potentially important role in off-pump coronary artery bypass surgery.

Invited commentary

This article [1Boodhwani M. Cohn W.E. Feng J. et al.Safety and efficacy of a novel gel for vascular occlusion in off-pump surgery.Ann Thorac Surg. 2005; 80: 2333-2337Abstract Full Text Full Text PDF PubMed Scopus (25) Google Scholar] reports a prospective, experimental study in pigs of the use of a resorbable gel with reverse thermosensitive properties for temporary coronary artery occlusion. The gel is soft at room temperature and hardens at body temperature. Because the material is water soluble it dissolves in blood at a rate proportional to the amount and concentration of the gel applied. By measurement of blood flow, regional fractional myocardial shortening, and microvascular function, the gel was equivalent to occlusion with a standard microvascular clamp. The authors suggest that the gel may have a utility for vessel occlusion during off-pump coronary artery bypass graft surgery and may be less traumatic than mechanical occlusive devices like clamps or vessel loops.This interesting idea is well presented in this article. As the authors acknowledge, this preliminary study is limited by the fact that the experimental model is not truly analogous either to the diseased coronary circulation or to conditions during clinical off-pump surgery. Nonetheless, the idea is original and is likely to be of interest to surgeons committed to improving this technology.Among the questions that remain to be answered are the efficacy of this approach in diseased human coronary arteries in which collateral circulation may alter the quality and duration of vessel occlusion. Also, what is the proper technique for injection of the gel? Is there a risk of coronary injury even if a very fine gauge needle is used for injection? Can more gel be applied should the vessel open due to dissolution of the gel before the anastomosis is complete or if an additional suture is required? Is there any role for a catheter-based delivery system? Might gel fragments be a source of peripheral coronary emboli should the gel not dissolve at a uniform rate? Despite these remaining and potentially important unresolved issues, this is the type of incremental innovation that characterizes many complex techniques which are now considered the standard of practice in contemporary cardiac surgery. This article [1Boodhwani M. Cohn W.E. Feng J. et al.Safety and efficacy of a novel gel for vascular occlusion in off-pump surgery.Ann Thorac Surg. 2005; 80: 2333-2337Abstract Full Text Full Text PDF PubMed Scopus (25) Google Scholar] reports a prospective, experimental study in pigs of the use of a resorbable gel with reverse thermosensitive properties for temporary coronary artery occlusion. The gel is soft at room temperature and hardens at body temperature. Because the material is water soluble it dissolves in blood at a rate proportional to the amount and concentration of the gel applied. By measurement of blood flow, regional fractional myocardial shortening, and microvascular function, the gel was equivalent to occlusion with a standard microvascular clamp. The authors suggest that the gel may have a utility for vessel occlusion during off-pump coronary artery bypass graft surgery and may be less traumatic than mechanical occlusive devices like clamps or vessel loops. This interesting idea is well presented in this article. As the authors acknowledge, this preliminary study is limited by the fact that the experimental model is not truly analogous either to the diseased coronary circulation or to conditions during clinical off-pump surgery. Nonetheless, the idea is original and is likely to be of interest to surgeons committed to improving this technology. Among the questions that remain to be answered are the efficacy of this approach in diseased human coronary arteries in which collateral circulation may alter the quality and duration of vessel occlusion. Also, what is the proper technique for injection of the gel? Is there a risk of coronary injury even if a very fine gauge needle is used for injection? Can more gel be applied should the vessel open due to dissolution of the gel before the anastomosis is complete or if an additional suture is required? Is there any role for a catheter-based delivery system? Might gel fragments be a source of peripheral coronary emboli should the gel not dissolve at a uniform rate? Despite these remaining and potentially important unresolved issues, this is the type of incremental innovation that characterizes many complex techniques which are now considered the standard of practice in contemporary cardiac surgery.

Protective effects of trapidil in lung after abdominal aorta induced ischemia–reperfusion injury: an experimental study

We aimed to investigate the protective effects of trapidil after the occlusion of abdominal aorta and the reperfusion injury in lung. Eighteen New Zealand albino rabbits were used in the study. In six animals [group 1, ischemia-reperfusion (IR) group], the abdominal aorta was exposed and a microvascular clamp was placed in the infrarenal abdominal aorta for 60 min. After the ischemic period, the microvascular clamp was removed and reperfusion was provided for 2 h. After the reperfusion period, the lungs were removed carefully and specimens were prepared for histopathological and biochemical studies in appropriate conditions. In group 2 (study group), trapidil (Rocarnal, Rentschler-UCB GmbH, Kerpen, Germany) was administered intraperitoneally as a single dose 1 h prior to trial, the IR procedure was performed and lung specimens were prepared similar to group 1. In group 3 (sham group), the infrarenal abdominal aorta was exposed and lung specimens were prepared for histopathological and biochemical studies at the end of the study. Histopathological changes, malondialdehyde (MDA), nitric oxide (NO) and total sulfhydryl group (T-SH) levels were evaluated. There was a statistical difference between the IR group and study group regarding NO and MDA levels (P < 0.05 and P < 0.01, respectively), but this was not detected between the IR group and the sham group (P > 0.05). There was no statistical difference among the three groups regarding T-SH levels (P > 0.05). While a statistical difference was found between the sham group and study group in the NO level (P < 0.05), no statistical difference was found in the MDA level (P > 0.05). There was a statistical difference in interstitial edema, PMN infiltration and hemorrhage scores among the groups (P < 0.05). There was a statistical difference between the IR group and study group in PMN infiltration (P < 0.05), but this was not detected between the groups in interstitial edema and hemorrhage scores (P > 0.05). There was a statistical difference between IR group and sham group in interstitial edema, PMN infiltration and hemorrhage scores (P < 0.05). Statistical difference was found between the sham group and study group in interstitial edema and hemorrhage scores (P < 0.05), but not in PMN infiltration (P > 0.05). Infrarenal abdominal aortic occlusion and reperfusion causes lung injury. We conclude that trapidil has preventive effects in the lung tissue after IR injury.

Change pattern of somatosensory-evoked potentials after occlusion of segmental vessels: possible indicator for spinal cord ischemia

Paraplegia was reported after occlusion of the segmental vessels during anterior spinal surgery. The aim of this study was to investigate the effect of occlusion of the segmental vessels on the somatosensory-evoked potential (SEP) monitoring and analyze its potential risk for cord ischemia. Thirty-one patients with thoracic scoliosis underwent anterior spinal surgery. T5-T11 segmental vessels on the convexity were occluded with microvascular clamps at the point 2 cm from the intravertebra foramen. The SEPs were recorded 5 min before occlusion and 2, 7, 12 and 17 min after occlusion. The SEPs were analyzed with two indices i.e. P40 latency and P40 amplitude. All SEP waveforms recorded during the test were regular and recognizable. Compared to 5 min before occlusion, the P40 latencies at 2 min and 7 min after occlusion significantly increased 3.39% and 2.76% on an average, the P40 amplitudes at 2 min after occlusion significantly declined 26% (peak to peak) or 22% (peak to baseline) on an average (P<0.05). But the changes of SEPs were temporary. The SEPs began to restore at 12 min after occlusion and returned to the pre-occlusion level at 17 min after occlusion. No neurologic complications occurred in all patients after surgery. These results suggest that SEP is a possible indicator for ischemia of the spinal cord which is a dynamic course and cannot be considered an "all-or-none" phenomenon. Without the factors such as developmental deformities of the spinal cord, vascular variation and potential cord ischemia, occlusion of the segmental vessels would be safe during the anterior spinal surgery.

The antioxidant effect of melatonin in lung injury after aortic occlusion?reperfusion

Acute aortic occlusion with subsequent ischemia-reperfusion of the lower extremities is well known to predispose to lung injury. Melatonin (MEL), a pineal hormone, is a free radical scavenger and an antioxidant. The purpose of this study was to assess the putative protective role of MEL in lung ischemia-reperfusion injury induced by aortic occlusion-reperfusion. Thirty-two rats were randomly allocated to four groups as follows: SHAM (Sham Laparotomy), SHAM+MEL, Aortic Ischemia Reperfusion (AIR) and AIR+MEL. Twenty mg/kg live weight MEL was given intraperitoneally 1 h prior to the experiment. An atraumatic microvascular clamp was placed across the infrarenal abdominal aorta (IAA) just after its origin from the aorta for 30 min. The microvascular clamp on IAA was removed and reperfused for 12 h. Lung tissues were assessed for malondialdehyde (MDA) level and myeloperoxidase (MPO) activity. MDA level and MPO activity, indicating the extent of lipid peroxidation and neutrophil infiltration of lung, respectively, significantly increased in AIR group when compared to SHAM and SHAM+MEL groups (P<0.05). Treating rat with MEL significantly decreased MDA levels as well as MPO activity in AIR+MEL group when compared to AIR group (P<0.05). In this study, exogenously administered MEL reduced lung injury after aortic occlusion reperfusion.

The protective effect of erythropoietin on ischaemia/reperfusion injury of liver

Besides its haematopoietic effect, erythropoietin (EPO) has multiple protective effects, i.e. antiapoptotic, antioxidant and angiogenic properties. The neuroprotective effects of EPO against ischaemia have all been demonstrated in cell culture and animal models. The aim of the study was to evaluate the effect of erythropoietin on ischaemia-reperfusion injury (I/R injury) of the liver. Forty-eight adult male Sprague-Dawley rats weighing 250-300 g were divided into three groups: group I, hepatic ischaemia-reperfusion (Hepatic I/R); group II, hepatic ischaemia-reperfusion + EPO (Hepatic I/R+ EPO); group III, sham. Hepatic ischaemia was created by placing a microvascular clamp on the hepatic pedicle for 45 minutes. EPO was given to group II at a dose of 1000 U/kg 120 minutes before the onset of the ischaemia. Blood samples and liver tissues were obtained after 45 minutes of reperfusion from half of the rats in each group. The remaining rats were killed after a 24-hour observation period and blood and tissue samples were obtained. Blood alanine aminotransferase, tumour necrosis factor-alpha (TNF-alpha), interleukin-2 (IL-2) and liver tissue malondialdehyde (MDA) levels were determined. Liver tissue histopathology was also evaluated by light microscopy. In rats with hepatic ischaemia, serum levels of ALT, TNF-alpha, IL-2 and liver tissue levels of MDA were reduced by the administration of erythropoietin and the histopathological score was also less severe. This study demonstrates that pre-ischaemic administration of EPO has protective effects on hepatic I/R injury.