Regionalization of services improves access to emergency vascular surgical care.

Management of vascular surgical emergencies requires rapid access to a vascular surgeon and hospital with the infrastructure necessary to manage vascular emergencies. The purpose of this study was to assess the impact of regionalization of vascular surgery services in Toronto to University Health Network (UHN) and St Michael's Hospital (SMH) on the ability of CritiCall Ontario to transfer patients with life- and limb-threatening vascular emergencies for definitive care. A retrospective review of the CritiCall Ontario database was used to assess the outcome of all calls to CritiCall regarding patients with vascular disease from April 2003 to March 2010. The number of patients with vascular emergencies referred via CritiCall and accepted in transfer by the vascular centers at UHN or SMH increased 500% between 1 April 2003-31 December 2005 and 1 January 2006-31 March 2010. Together, the vascular centers at UHN and SMH accepted 94.8% of the 1002 vascular surgery patients referred via CritiCall from other hospitals between 1 January 2006 and 31 March 2010, and 72% of these patients originated in hospitals outside of the Toronto Central Local Health Integration Network. Across Ontario, the number of physicians contacted before a patient was accepted in transfer fell from 2.9 ± 0.4 before to 1.7 ± 0.3 after the vascular centers opened. In conclusion, the vascular surgery centers at UHN and SMH have become provincial resources that enable the efficient transfer of patients with vascular surgical emergencies from across Ontario. Regionalization of services is a viable model to increase access to emergent care.

Neoadjuvant aortic endografting.

The advent and success of endovascular repair of abdominal aneurysms led to the development of catheter-based techniques to treat thoracic aortic pathology. Such diseases, including thoracic aortic aneurysms, acute and chronic type B dissections, penetrating aortic ulcers, and traumatic aortic transection, challenge surgeons to perform complex open operative repairs in high-risk patients. The minimally invasive nature of thoracic endografting provides an attractive alternative therapy. We present two cases of covered stent grafts deployed in the thoracic aorta to perform resection of the aortic wall infiltrated by malignancy in order to avoid a major vascular intervention and a traditional vascular graft interposition. This may become a potential new utility for aortic endografts.

C5 complement inhibition attenuates shock and acute lung injury in an experimental model of ruptured abdominal aortic aneurysm.

BACKGROUND: Ruptured abdominal aortic aneurysm (RAAA) is associated with a systemic inflammatory response syndrome and multiple organ dysfunction. The potential role of a novel C5 complement inhibitor in attenuation of pathological complement activation and tissue injury was explored in a model of RAAA. METHODS: Anaesthetized rats were randomized to sham (control) or shock and clamp (SC) groups. Animals in the SC group underwent 1 h of haemorrhagic shock (mean arterial pressure 50 mmHg or less), 45 min of supramesenteric aortic clamping and 2 h of reperfusion. They were randomized to receive an intravenous bolus of a functionally blocking anti-C5 monoclonal antibody (C5 inhibitor), at a dose of 20 mg/kg, or saline. Lung injury was assessed by permeability to 125I-labelled albumin, tissue myeloperoxidase (MPO) activity, and semiquantitative reverse transcriptase-polymerase chain reaction (RT-PCR) for mRNAs encoding tumour necrosis factor (TNF) alpha and interleukin (IL) 6. RESULTS: The lung permeability index was significantly increased in the SC compared with the sham group (P = 0.032); this was prevented by the C5 inhibitor (P = 0.015). Lung MPO activity was significantly increased in the SC compared with the sham group (P < 0.001), and this increase was attenuated by treatment with the C5 inhibitor (P < 0.001). Semiquantitative RT-PCR in SC group demonstrated downregulation of TNF-alpha mRNA (P = 0.050) and upregulation of IL-6 mRNA (P < 0.001), which were both prevented by the C5 inhibitor (P = 0.014 and P < 0.001 respectively). CONCLUSION: These results indicated that C5 complement inhibition can reduce shock and acute lung injury in an experimental model of RAAA.

p38 MAPK regulates group IIa phospholipase A2 expression in interleukin-1beta -stimulated rat neonatal cardiomyocytes.

Group IIa phospholipase A(2) (GIIa PLA(2)) is released by some cells in response to interleukin-1beta. The purpose of this study was to determine whether interleukin-1beta would stimulate the synthesis and release of GIIa PLA(2) from cardiomyocytes, and to define the role of p38 MAPK and cytosolic PLA(2) in the regulation of this process. Whereas GIIa PLA(2) mRNA was not identified in untreated cells, exposure to interleukin-1beta resulted in the sustained expression of GIIa PLA(2) mRNA. Interleukin-1beta also stimulated a progressive increase in cellular and extracellular GIIa PLA(2) protein levels and increased extracellular PLA(2) activity 70-fold. In addition, interleukin-1beta stimulated the p38 MAPK-dependent activation of the downstream MAPK-activated protein kinase, MAPKAP-K2. Treatment with the p38 MAPK inhibitor, SB202190, decreased interleukin-1beta stimulated MAPKAP-K2 activity, GIIa PLA(2) mRNA expression, GIIa PLA(2) protein synthesis, and the release of extracellular PLA(2) activity. Infection with an adenovirus encoding a constitutively active form of MKK6, MKK6(Glu), which selectively phosphorylates p38 MAPK, induced cellular GIIa PLA(2) protein synthesis and the release of GIIa PLA(2) and increased extracellular PLA(2) activity 3-fold. In contrast, infection with an adenovirus encoding a phosphorylation-resistant MKK6, MKK6(A), did not result in GIIa PLA(2) protein synthesis or release by unstimulated cardiomyocytes. In addition, infection with an adenovirus encoding MKK6(A) abrogated GIIa PLA(2) protein synthesis and release by interleukin-1beta-stimulated cells. These results provide direct evidence that p38 MAPK activation was necessary for interleukin-1beta-induced synthesis and release of GIIa PLA(2) by cardiomyocytes.

Hemorrhage-induced alpha-adrenergic signaling results in myocardial TNF-alpha expression and contractile dysfunction.

Hemorrhagic shock (HS), secondary to major blood loss, frequently precedes multiple organ dysfunction and is accompanied by a surge in circulating catecholamine levels. Expression of the cardiodepressant cytokine, tumor necrosis factor-alpha (TNF-alpha), has been observed in the heart after HS and resuscitation (HS/R) and alpha(1)-adrenergic blockade prevented translocation of the nuclear transcription factor, NF-kappa B, to the nucleus. We hypothesized that alpha(1)-adrenergic stimulation induces myocardial TNF-alpha expression, which results in depressed cardiac function after HS/R. The role of alpha(1)-adrenergic stimulation in myocardial TNF-alpha expression and depressed cardiac function after HS/R was assessed by treatment with the alpha(1)-adrenergic inhibitor, prazosin hydrochloride (1 mg/kg ip), for 1 h before the onset of hemorrhage. In addition, TNF-alpha was neutralized with a specific antibody (600 microl/kg iv) 5 min before hemorrhage. HS was induced by the withdrawal of blood to a mean blood pressure of 50 mmHg for 1 h. Contractile function was measured with the use of a Langendorff apparatus 2 h after the end of HS. HS/R led to significant decreases in left ventricular developed tension and in the maximal rate of pressure increase over time during both contraction and relaxation. Myocardial expression of TNF-alpha measured by enzyme-linked immunosorbent assay increased significantly after 30 min of hemorrhage and peaked after 60 min of HS and 45 min of resuscitation. Depression in cardiac function after HS/R was reversed by 85% in hearts from rats treated with a TNF-alpha neutralizing antibody and by 90% in hearts from rats treated with prazosin hydrochloride. We conclude that HS activates a alpha(1)-adrenergic pathway, resulting in TNF-alpha expression in the heart and depressed myocardial contractile function.

Role of TNF-alpha in myocardial dysfunction after hemorrhagic shock and lower-torso ischemia.

Ruptured abdominal aortic aneurysm (RAAA) repair, a combination of hemorrhagic shock and lower-torso ischemia, is associated with a 50-70% mortality. Myocardial dysfunction may contribute to the high rate of mortality after aneurysm repair. We attempted to determine whether RAAA repair results in cardiac dysfunction mediated by tumor necrosis factor-alpha (TNF-alpha). We modeled aortic rupture and repair in the rat by inducing hemorrhagic shock to a mean blood pressure of 50 mmHg for 1 h, followed by supramesenteric clamping of the aorta for 45 min. After 90 min of reperfusion, cardiac contractile function was assessed with a Langendorff preparation. Myocardial TNF-alpha, ATP and creatine phosphate (CP) levels, and markers of oxidant stress (F(2)-isoprostanes) were measured. Cardiac function in the combined shock and clamp rats was significantly depressed compared with sham-operated control rats but was similar to that noted in animals subjected to shock alone. Myocardial TNF-alpha concentrations increased 10-fold in the combined shock and clamp rats compared with sham rats, although there was no difference in myocardial ATP, CP, or F(2)-isoprostanes. TNF-alpha neutralization improved cardiac function by 50% in the combined shock and clamp rats. Hemorrhagic shock is the primary insult inducing cardiac dysfunction in this model of RAAA repair. An improvement in cardiac contractile function after immunoneutralization of TNF-alpha indicates that TNF-alpha mediates a significant portion of the myocardial dysfunction in this model.

Ruptured abdominal aortic aneurysm, a "two-hit" ischemia/reperfusion injury: evidence from an analysis of oxidative products.

PURPOSE: Ruptured abdominal aortic aneurysm (RAAA) remains a lethal condition despite improvements in perioperative care. The consequences of RAAA are hypothesized to result from a combination of two ischemia/reperfusion events: hemorrhagic shock and lower torso ischemia. Ischemia/reperfusion results in tissue injury by diverse mechanisms, which include oxygen free radical-mediated injury produced from activated neutrophils, xanthine oxidase, and mitochondria. Oxygen-free radicals attack membrane lipids, resulting in membrane and subsequently cellular dysfunction that contributes to postoperative organ injury/failure. The purpose of this investigation was to quantify the oxidative injury that occurs as a result of the ischemia/reperfusion events in RAAAs and elective AAAs. METHODS: Blood samples were taken from 22 patients for elective AAA repair and from 14 patients for RAAA repair during the perioperative period. Plasma F(2)-isoprostanes were extracted, purified, and measured with an enzyme immunoassay. Aldehydes and acyloins were purified and quantified. Neutrophil oxidative burst was measured in response to a receptor independent stimulus (phorbol 12-myristate 13-acetate) with luminol-based chemiluminescence. RESULTS: Plasma from patients with RAAAs showed significantly elevated F(2)-isoprostane levels on arrival at hospital and were significantly elevated as compared with the levels of patients for elective repair throughout the perioperative period (two-way analysis of variance, P <.0001). Multiple regression showed a significant relationship between the phagocyte oxidative activity and F(2)-isoprostane levels (P <.013). Total acyloin levels were significantly higher in patients with RAAAs as compared with the levels in elective cases. CONCLUSION: The F(2)-isoprostane levels, specific markers of lipid peroxidation, showed that patients with RAAAs had two phases of oxidative injury: before arrival at hospital and after surgery. The significant relationship between the postoperative increases in F(2)-isoprostane levels and the neutrophil oxidant production implicates neutrophils in the oxidative injury that occurs after RAAA. New therapeutic interventions that attenuate neutrophil-mediated oxidant injury during reperfusion may decrease organ failure and ultimately mortality in patients with RAAAs.

A CD18 monoclonal antibody reduces multiple organ injury in a model of ruptured abdominal aortic aneurysm.

The role of CD18 antibody (anti-CD18) in remote and local injury in a model of ruptured abdominal aortic aneurysm repair was investigated. Rats were divided into sham, shock, clamp, and shock + clamp groups. Shock + clamp animals received anti-CD18 or a control monoclonal antibody. One hour of hemorrhagic shock was followed by 45 min of supramesenteric aortic clamping. Intestinal and pulmonary permeability to (125)I-labeled albumin was determined. Myeloperoxidase (MPO) activity, F(2)-isoprostane levels, and transaminases were also measured. Only shock + clamp resulted in statistically significant increases in pulmonary and intestinal permeability, which were associated with significant increases in MPO activity and F(2)-isoprostane levels. Treatment with anti-CD18 significantly decreased intestinal and pulmonary permeability in shock + clamp animals. These reductions were associated with significantly reduced intestinal and hepatic MPO activity and pulmonary F(2)-isoprostane levels and reduced alanine and aspartate aminotransferase levels; however, anti-CD18 had no effect on intestinal or hepatic F(2)-isoprostane levels or on pulmonary MPO activity. These results suggest CD18-dependent and -independent mechanisms of local and remote organ injury in this model of ruptured abdominal aortic aneurysm.

Importance of MEK in neutrophil microbicidal responsiveness.

Exposure of neutrophils to inflammatory stimuli such as the chemoattractant FMLP leads to activation of responses including cell motility, the oxidative burst, and secretion of proteolytic enzymes. A signaling cascade involving sequential activation of Raf-1, mitogen-activated protein kinase (MEK), and extracellular signal regulated kinase (ERK) is also rapidly activated after agonist exposure. The temporal relationship between these events suggests that the kinases may be involved in triggering the effector functions, but direct evidence of a causal relationship is lacking. To assess the role of the MEK/ERK pathway in the activation of neutrophil responses, we studied the effects of PD098059, a potent and selective inhibitor of MEK. Preincubation of human neutrophils with 50 microM PD098059 almost completely (>90%) inhibited the FMLP-induced activation of MEK-1 and MEK-2, the isoforms expressed by neutrophils. This dose of PD098059 virtually abrogated chemoattractant-induced tyrosine phosphorylation and activation of ERK-1 and ERK-2, implying that MEKs are the predominant upstream activators of these mitogen-activated protein kinases. Pretreatment of neutrophils with the MEK antagonist inhibited the oxidative burst substantially and phagocytosis only moderately. In addition, PD098059 antagonized the delay of apoptosis induced by exposure to granulocyte-macrophage CSF. However, the effects of PD098059 were selective, as it failed to inhibit other responses, including chemoattractant-induced exocytosis of primary and secondary granules, polymerization of F-actin, chemotaxis, or activation of phospholipase A2. We conclude that MEK and ERK contribute to the activation of the oxidative burst and phagocytosis, and participate in cytokine regulation of apoptosis.

Sequential ischemia/reperfusion results in contralateral skeletal muscle salvage.

Sequential ischemia/reperfusion in a paired canine gracilis muscle model resulted in significant muscle salvage. In this model, one randomly chosen gracilis muscle was subjected to 5 h of ischemia followed by 48 h of in vivo reperfusion. The contralateral (second) muscle was then made ischemic and reperfused using the same protocol. Muscle necrosis was determined at the end of 48 h of reperfusion. A mean 60% reduction in muscle necrosis was observed in the second group of muscles. Analysis of tissue adenine nucleotides indicated that significant sparing of ATP utilization occurred in the second muscle group during ischemia. Preliminary analysis of tissue heat shock proteins (HSP) showed that the second group of muscles had a different pattern of HSP expression before the onset of ischemia. The results suggest that reduced ATP utilization and altered HSP expression in the second muscle play a role in the tissue salvage observed in this sequential muscle ischemia model.

Mechanisms of postischemic injury in skeletal muscle: intervention strategies.

Reperfusion of ischemic skeletal muscle leads to adverse local and systemic effects. These detrimental effects may be attenuated by interfering with or modulating the pathophysiological processes that are set in motion during ischemia and/or reperfusion. The purpose of this paper is to review the different intervention strategies that have been employed in an attempt to elucidate the mechanisms involved in the pathogenesis of skeletal muscle ischemia-reperfusion injury. The results of these studies indicate that the postischemic injury processes that lead to cell dysfunction and death are multifactorial in nature and include oxidant generation, elaboration of proinflammatory mediators, infiltration of leukocytes, Ca2+ overload, phospholipid peroxidation and depletion, impaired nitric oxide metabolism, and reduced ATP production. Although the etiopathogenesis of skeletal muscle ischemia-reperfusion is complex, careful delineation of the mechanisms that contribute to postischemic microvascular dysfunction and muscle necrosis has progressed to the point where rational intervention strategies may be proposed and implemented as potential treatments for skeletal muscle dysfunction associated with ischemia-reperfusion.

Phospholipid peroxidation deacylation and remodeling in postischemic skeletal muscle.

Reperfusion of ischemic skeletal muscle is associated with white blood cell (WBC) sequestration and hydroperoxy-conjugated diene (HCF) formation, a marker of free radical-mediated phospholipid peroxidation. The purpose of this study was to define the kinetics of phospholipid fatty acyl peroxidation, deacylation, and remodeling in postischemic skeletal muscle during prolonged reperfusion in vivo, and to determine whether reperfusion with WBC and plasma-depleted blood would attenuate postischemic phospholipid peroxidation and myocyte necrosis. The isolated, paired, canine gracilis muscle model was used. After 5 h of ischemia, muscles underwent unaltered reperfusion or initial reperfusion with WBC-deficient blood cells resuspended in hydroxyethyl starch, followed by return to normal circulation (modified reperfusion). The concentration of native fatty acids and HCDs of linoleic acid extracted from muscle phospholipids was quantified by gas chromatography and positively identified by mass spectrometry. Ischemia and reperfusion resulted in phospholipid deacylation and a selective increase in phospholipid stearic acid content, but had no effect on total phospholipid phosphorus. Modified reperfusion decreased 1) early HCD formation (54%) and 2) postischemic skeletal muscle necrosis (49%). These data suggest that reperfusion results in phospholipid deacylation and remodeling, and that the initial oxidant stress during reperfusion may be a significant determinant of ultimate muscle necrosis.

Decreased leukocyte adhesion with anti-CD18 monoclonal antibodies is mediated by receptor internalization.

BACKGROUND: Adhesion of polymorphonuclear leukocytes (PMNs) to endothelial cells is mediated partially by CD11/CD18 integrins. The purpose of this study was to define (1) the response of PMNs to anti-CD18 monoclonal antibody binding, and (2) the mechanism responsible for anti-CD18 monoclonal antibody-mediated decreases in PMN adhesion to endothelial cells. METHODS: Canine PMN O2- production, myeloperoxidase, and lysozyme release in response to the anti-CD18 monoclonal antibody IB4 were measured by standard assays. To examine endocytosis of CD18 receptors, PMNs incubated with IB4 and a fluorescein isothiocyanate secondary antibody were analyzed by flow cytometry. RESULTS: Treatment of PMNs with IB4 did not stimulate O2- production or degranulation but decreased adhesion of 51Cr-labeled PMNs to ex vivo canine aorta. Incubation of PMNs at 25 degrees C resulted in a decrease in fluorescence intensity that was not affected by NaN3 or vanadate but was blocked by NaF, 4 degrees C, and bafilomycin, which prevents endosomal acidification. Treatment with an antifluorescein antibody decreased the fluorescence intensity in NaF and 4 degrees C, but not in bafilomycin-treated neutrophils. CONCLUSIONS: IB4 decreases PMN-endothelial cell adhesion but does not stimulate neutrophil oxidative metabolism or degranulation. These data suggest that reduced adhesion may be the result of internalization of the CD18/IB4 complex. Anti-CD18 monoclonal antibodies may be useful in preventing PMN adhesion without the potentially deleterious effects of cell activation.

Prolonged adenine nucleotide resynthesis and reperfusion injury in postischemic skeletal muscle.

Skeletal muscle ischemia results in energy depletion and intracellular acidosis. Reperfusion is associated with impaired adenine nucleotide resynthesis, edema formation, and myocyte necrosis. The purpose of these studies was to define the time course of cellular injury and adenine nucleotide depletion and resynthesis in postischemic skeletal muscle during prolonged reperfusion in vivo. The isolated canine gracilis muscle model was used. After 5 h of ischemia, muscles were reperfused for either 1 or 48 h. Lactate and creatine phosphokinase (CPK) release during reperfusion was calculated from arteriovenous differences and blood flow. Adenine nucleotides, nucleosides, bases, and creatine phosphate were quantified by high-performance liquid chromatography, and muscle necrosis was assessed by nitroblue tetrazolium staining. Reperfusion resulted in a rapid release of lactate, which paralleled the increase in blood flow, and a delayed but prolonged release of CPK. Edema formation and muscle necrosis increased between 1 and 48 h of reperfusion (P less than 0.05). Recovery of energy stores during reperfusion was related to the extent of postischemic necrosis, which correlated with the extent of nucleotide dephosphorylation during ischemia (r = 0.88, P less than 0.001). These results suggest that both adenine nucleotide resynthesis and myocyte necrosis, which are protracted processes in reperfusing skeletal muscle, are related to the extent of nucleotide dephosphorylation during ischemia.

Complement activation and white cell sequestration in postischemic skeletal muscle.

After skeletal muscle ischemia, tissue damage is augmented during reperfusion. White blood cells (WBCs) and complement proteins may participate in the reperfusion injury. The purpose of this study was to define the kinetics of classical and alternative pathway complement activation and WBC sequestration by postischemic skeletal muscle during the first 48 h of reperfusion in vivo. The isolated canine gracilis muscle model was used. Systemic levels of the complement proteins factor B (alternative pathway) and C4 (classical pathway) were quantitated by hemolytic assay. WBC sequestration was measured by gracilis arterial-venous WBC differences and tissue myeloperoxidase activity. Reperfusion was associated with an 18% decrease in systemic factor B levels but no consistent change in systemic C4 levels. WBCs were sequestered during the first 4 h of reperfusion, and tissue myeloperoxidase activity was elevated 97-fold after 48 h of reperfusion. These results suggest that skeletal muscle ischemia-reperfusion stimulates 1) activation of the alternative but not the classical complement pathway and 2) an immediate and prolonged sequestration of WBCs.

Latex-Rickettsia rickettsii test reactivity in seropositive patients.

In correlating results obtained from a new latex-Rickettsia rickettsii test with results obtained from a reference microimmunofluorescence test for Rocky Mountain spotted fever, we found that for seropositive patients each microimmunofluorescence titer (up to 4,096) was usually double the median titer obtained from the latex-R. rickettsii test. The pattern of immunoserological response indicated that latex-R. rickettsii is reactive with sera containing either anti-R. rickettsii immunoglobulin M (IgM) or IgG or both. The agglutination efficiency of the new test was greater when the anti-rickettsial IgM/IgG ratio was greater than or equal to 1. Sera from late-convalescent patients were generally minimally reactive or nonreactive in the latex-R. rickettsii test unless anti-R. rickettsii IgM was present.

Sodium and potassium effects on skeletal muscle microsomal adenosine triphosphatase and calcium uptake.

The relationship between the (Na(+) and K(+))-activated adenosine triphosphatase enzyme system implicated in sodium-transport by cell membranes and the calcium-activated adenosine triphosphatase, which is generally associated with calcium uptake, was examined in microsomes from skeletal muscle. Whereas sodium and potassium did not modify the relatively low adenosine triphosphatase activity seen in the absence of calcium, a pattern similar to that of the sodium-transport enzyme system was seen afer the addition of CaCl(2). The calcium-activated adenosine triphosphatase was stimulated equally by sodium or potassium alone, but both the rate and extent of calcium uptake were enhanced more by potassium than by sodium at concentrations below 0.12 mole per liter. In the absence of either of these ions addition of calcium failed to activate adenosine triphosphatase although significant amounts of calcium were taken up by the microsomes.