Effects of acute global venous obstruction and unfractionated heparin on muscle cytokine synthesis.

Phlegmasia cerulea dolens is a devastating complication of massive deep venous thrombosis, which is clinically characterized by massive lower extremity tissue edema and subsequent arterial insufficiency. These experiments evaluated the local tissue effects of acute global venous obstruction combined with partial arterial ischemia. Experiments were performed to assess the effects of heparin on the cytokine response to simultaneous venous and partial arterial obstruction. Murine hind limbs were subjected to conditions of unilateral venous occlusion and partial tourniquet limb ischemia, which was confirmed by laser Doppler imaging (LDI). Mice underwent either hind limb venous obstruction with intravenous unfractionated heparin (200IU/kg) or intravenous saline 5min before venous occlusion. Sham-treated mice were subjected to anesthesia alone without venous occlusion. After 3hr, the mice were killed and tissue was harvested for measurement of edema (wet to dry weight ratio, W/D), muscle viability, indices of local thrombosis (thrombin-antithrombin complex [TAT]), and cytokine analysis for growth-related oncogene-1 (GRO-1) and interleukin-6 (IL-6, protein via enzyme-linked immunoassay and mRNA via reverse transcriptase polymerase chain reaction). Bleeding time and volume were documented in saline- and heparin-treated mice to confirm systemic anticoagulation. Administration of intravenous heparin resulted in a marked increase in bleeding time and volume. LDI confirmed venous obstruction and ongoing arterial inflow. Venous obstruction resulted in severe visible edema that correlated with a significantly higher W/D ratio but was not associated with a significant decrease in muscle viability. GRO-1 and IL-6 protein and mRNA levels were significantly elevated in the venous occlusion group compared to sham. Heparin therapy significantly decreased TAT3 levels but did not alter the profile of GRO-1 or IL-6 protein levels seen with venous occlusion. Venous occlusion with partial ischemia induces a unique and potent local cytokine expression. Heparin therapy did not ameliorate the cytokine response. These data indicate that heparin therapy does not modulate the cytokine response to venous obstruction.

Local inflammatory and thrombotic responses differ in a murine model of partial and complete hindlimb ischemia/reperfusion.

BACKGROUND: These experiments were designed to quantitatively compare the patterns of tissue thrombosis, cytokine response, and tissue viability in a murine model of partial (PI) versus complete hindlimb ischemia (CI), alone or with reperfusion (RE). METHODS: The control tension tourniquet was used to establish either PI or CI in the unilateral mouse hindlimb for 3 hours followed by 0, 4, and 24 hours of RE. Muscle viability, local neutrophil chemoattractant protein, interleukin 6, interleukin 1beta, D-dimer, thrombin-antithrombin III complex, plasminogen activator inhibitor 1, and tissue plasminogen activator levels were measured in protein extracts for each experimental interval. RESULTS: Tissue viability after CI and 24 hours of RE was significantly less than tissue subjected to PI and 24 hours of RE (96% +/- 16 PI, 64% +/- 4 CI, P=.02). The local cytokine response was initially elevated in the PI group but dissipated by 24RE. In contrast, the local cytokine response to CI alone was small but greatly increased by 24RE. The thrombotic response to PI was increased throughout ischemia/reperfusion. While thrombosis during CI alone was negligible, reperfusion led to a significant thrombotic response. CONCLUSIONS: Biochemical markers for tissue viability, thrombosis, and cytokine-mediated inflammation differ significantly in mice subjected to moderate and severe hindlimb ischemia/reperfusion. These biochemical markers may facilitate stratification of patients in clinical trials for treatment of ischemia/reperfusion injury and contribute to interpretation of their outcomes.

Polyadenosine diphosphate-ribose polymerase inhibition modulates skeletal muscle injury following ischemia reperfusion.

HYPOTHESIS: Polyadenosine diphosphate-ribose polymerase (PARP) has been implicated as a mediator of inflammation and tissue necrosis in murine models of human stroke and myocardial infarction. This study was designed to determine whether PARP modulates skeletal muscle injury and cytokine-growth factor levels during ischemia-reperfusion. DESIGN: Prospective controlled animal study. SETTING: Medical school-affiliated university hospital. INTERVENTIONS: Mice were divided into 2 groups-treated (PJ) and untreated; all mice were subjected to unilateral hind limb tourniquet ischemia followed by 4 or 48 hours of reperfusion. In treated mice, PJ34, an ultrapotent-specific PARP inhibitor was given immediately before ischemia and prior to reperfusion. A group of PARP-1 knockout mice (PARP-/-) were also subjected to hind limb ischemia followed by 48 hours of reperfusion. MAIN OUTCOME MEASURES: After ischemia-reperfusion, muscle was harvested for measurement of edema, viability, cytokine, and vascular endothelial growth factor content. RESULTS: The PJ34-treated mice had increased skeletal muscle viability when compared with the untreated mice after 4 and 48 hours of reperfusion (P<.01). Viability between PARP-/- and PJ34-treated mice were similar at 48 hours of reperfusion (P>.05), and it exceeded that of untreated mice (P<.01). Tissue edema was unaltered by PARP inhibition. Tissue levels of cytokine were only different (P<.05) in PJ34-treated vs untreated mice at 48 hours of reperfusion. Vascular endothelial growth factor levels in PJ34-treated mice were markedly reduced when compared with untreated mice only after 4 hours of reperfusion (P<.01), and in PARP-/- mice (P<.01) at 48 hours of reperfusion. CONCLUSIONS: Polyadenosine diphosphate-ribose polymerase modulates skeletal muscle viability, cytokine and vascular endothelial growth factor synthesis during reperfusion. Polyadenosine diphosphate-ribose polymerase inhibition may represent a novel method to modulate skeletal muscle ischemia-reperfusion injury.

Safety of carbon dioxide digital subtraction angiography.

OBJECTIVE: Reports of fatality following carbon dioxide digital subtraction angiography (CO2-DSA) have raised concerns regarding its safety. This study reviews the safety of CO2-DSA. DESIGN: Single-institution retrospective review. SETTING: Tertiary care teaching hospital in Los Angeles, California. PATIENTS: A total of 951 patients who underwent 1007 CO2-DSA procedures during a 21-year period. MAIN OUTCOME MEASURES: Preprocedure and postprocedure creatinine values and periprocedural morbidity and mortality. RESULTS: A total of 632 arterial CO2-DSA were performed; 527 were aortograms with or without extremity runoff; 100, extremity alone; and 5, pulmonary. Venous CO2-DSA included 187 inferior vena cavagrams, 182 hepatic or visceral, 5 extremity venograms, and 1 superior vena cavagram. Associated endovascular procedures were performed in 499 cases; 162 were arterial interventions including 62 endovascular aneurysm repairs, 53 visceral or renal percutaneous angioplasty with/without stent, 41 extremity percutaneous angioplasty with or without a stent, and 4 cases of thrombolysis or embolization; 176 caval filters, 98 transjugular intrahepatic portosystemic shunts, 54 transjugular liver biopsies, and 9 other venous interventions. The mean preprocedure creatinine level was 2.1 mg/dL; postprocedure, 2.1 mg/dL (P = .56). There were a total of 61 (6.1%) procedural complications including 4 (0.4%) mortalities. Two were procedure-related complications: 1, suppurative pancreatitis following aortogram; and 2, hepatic bleed following failed transjugular intrahepatic portosystemic shunts. Two were attributable to patient disease; 1, metastatic adenocarcinoma; and 2, refractory, end-stage cardiomyopathy. CONCLUSION: Carbon dioxide digital subtraction angiography is a versatile technique that can be safely used for diagnostic and therapeutic endovascular procedures. Morbidity and mortality are acceptable with preservation of renal function. Thus, CO2-DSA is a safe alternative to iodinated contrast.

Defining the high-risk patient for carotid endarterectomy: an analysis of the prospective National Surgical Quality Improvement Program database.

BACKGROUND: Carotid endarterectomy (CEA) is the gold standard for the treatment of carotid stenosis, but carotid angioplasty and stenting has been advocated in high-risk patients. The definition of such a population has been elusive, particularly because the data are largely retrospective. Our study examined results for CEA in the National Surgical Quality Improvement Program database (both Veterans Affairs and private sector). METHODS: National Surgical Quality Improvement Program data were gathered prospectively for all patients undergoing primary isolated CEA during the interval 2000 to 2003 at 123 Veterans Affairs and 14 private sector academic medical centers. Study end points included the 30-day occurrence of any stroke, death, or cardiac event. A variety of clinical, demographic, and operative variables were assessed with multivariate models to identify risk factors associated with the composite (stroke, death, or cardiac event) end point. Adjudication of end points was by trained nurse reviewers (previously validated). RESULTS: A total of 13,622 CEAs were performed during the study period; 95% were on male patients, and 91% of cases were conducted within the Veterans Affairs sector. The average age was 68.6 +/- 0.1 years, and 42.1% of the population had no prior neurologic event. The composite stroke, death, or cardiac event rate was 4.0%; the stroke/death rate was 3.4%. Multivariate correlates of the composite outcome were (odds ratio, P value) as follows: deciles of age (1.13, .018), insulin-requiring diabetes (1.73, <.001), oral agent-controlled diabetes (1.39, .003), decade of pack-years smoking (1.04, >.001), history of transient ischemic attack (1.41, >.001), history of stroke (1.51, >.001), creatinine >1.5 mg/dL (1.48, >.001), hypoalbuminemia (1.49, >.001), and fourth quartile of operative time (1.44, >.001). Cardiopulmonary comorbid features did not affect the composite outcome in this model. Regional anesthesia was used in 2437 (18%) cases, with a resultant relative risk reduction for stroke (17%), death (24%), cardiac event (33%), and the composite outcome (31%; odds ratio, 0.69; P = .008). CONCLUSIONS: Carotid endarterectomy results across a spectrum of Veterans Affairs and private sector hospitals compare favorably to contemporary studies. These data will assist in selecting patients who are at an increased risk for adverse outcomes. Use of regional anesthetic significantly reduced perioperative complications in a risk-adjusted model, thus suggesting that it is the anesthetic of choice when CEA is performed in high-risk patients.

Safety and efficacy of reoperative carotid endarterectomy: a 14-year experience.

BACKGROUND: Reoperative carotid endarterectomy (CEA) is an accepted treatment for recurrent carotid stenosis. With reports of a higher operative morbidity than primary CEA and the advent of carotid stenting, catheter-based therapy has been advocated as the primary treatment for this reportedly "high-risk" subgroup. This study reviews a contemporary experience with reoperative CEA to validate the high-risk categorization of these patients. METHODS: From 1989 to 2002, 153 consecutive, isolated (excluding CEA/coronary artery bypass graft and carotid bypass operations) reoperative CEA procedures were reviewed. Clinical and demographic variables potentially associated with the end points of perioperative morbidity, long-term durability, and late survival were assessed with multivariate analysis. RESULTS: There were 153 reoperative CEA procedures in 145 patients (56% men, 36% symptomatic) with an average age of 69 +/- 1.3 years. The average time from primary CEA (68% primary closure, 23% prosthetic, 9% vein patch) to reoperative CEA was 6.1 +/- 0.4 years (range, 0.3 to 20.4 years). At reoperation, patch reconstruction was undertaken in 93% of cases. The perioperative stroke rate was 1.9%, with no deaths or cardiac complications. Other complications included cranial nerve injury (1.3%) and hematoma (3.2%). Average follow-up after reoperative CEA was 4.4 +/- 0.3 years (range, 0.1 to 12.7 years), with an overall total stroke-free rate of 96% and a restenosis rate (>50%) by carotid duplex of 9.2%. Among variables assessed for association with restenosis after reoperative CEA, only younger age was found to be significant (66 +/- 2.5 years vs 70 +/- 0.7 years, P < .05). The all-cause long-term mortality rate was 29%. Multivariate analysis of long-term survival identified diabetes mellitus as having a negative impact (hazard ratio, 3.4 +/- 0.3, P < .05) and lipid-lowering agents as having a protective effect (hazard ratio, 0.42 +/- 0.4, P < .05) on survival. CONCLUSION: Reoperative CEA is a safe and durable procedure, comparable to reported standards for primary CEA, for long-term protection from stroke. These data do not support the contention that patients who require reoperative CEA constitute a "high-risk" subgroup in whom reoperative therapy should be avoided.

CXC chemokine expression and synthesis in skeletal muscle during ischemia/reperfusion.

BACKGROUND: The chemokines keratinocyte-Derived Cytokine (KC) and macrophage inflammatory protein (MIP)-2, murine equivalents of human interleukin 8, have been implicated in remote injury after acute hind limb ischemia/reperfusion (I/R). These studies were designed to determine whether the cytokines responsible for remote tissue injury are also synthesized and accumulate in the ischemic or reperfused hind limb. METHODS: B6, 129SF2/J mice were subjected to either 3 hours of unilateral hind limb ischemia alone (IA) or 3 hours of ischemia followed by 4 or 24 hours of reperfusion (I/R). After IA or I/R, experimental and control (nonischemic) contralateral hind limbs were harvested for analysis of protein content, messenger RNA (mRNA), tissue edema, and viability. RESULTS: IA did not increase KC or MIP-2 mRNA or protein levels. In contrast, I/R resulted in a 15- and 10-fold increase in KC mRNA after 4 and 24 hours of reperfusion, respectively. KC protein levels were increased 10-fold after 4 hours of reperfusion and 30-fold after 24 hours (vs IA or sham; P < .001). MIP-2 mRNA transiently increased 42-fold after 4 hours of reperfusion but decreased to basal levels after 24 hours of reperfusion. Despite the relative increase in MIP-2 mRNA by 4 hours of reperfusion, significantly increased (8- to 10 fold) MIP-2 protein levels were not detected until 24 hours of reperfusion only in the reperfused limbs. Tissue edema was increased significantly (P < .01) compared with sham after just 4 hours of reperfusion and remained increased at 24 hours. Tissue viability decreased 52% after 4 hours of reperfusion and did not change significantly by 24 hours. CONCLUSIONS: Skeletal muscle is a site of significant ongoing chemokine synthesis during reperfusion. The persistent increase in muscle chemokine levels at 24 hours of reperfusion was not associated with increased edema or injury. The role of these chemokines during reperfusion may be further investigated by local or oral administration of chemokines or chemokine receptor antagonists. CLINICAL RELEVANCE: I/R injury remains an important clinical problem across a variety of surgical specialties. In the critical care arena, serum levels of proinflammatory cytokines have been useful in predicting the mortality associated with acute respiratory distress syndrome and sepsis. In this article, the data presented indicate that murine skeletal muscle produces potent proinflammatory neutrophil and macrophage chemokines during reperfusion, but not during ischemia. These findings suggest that measurement of tissue and/or serum levels of chemokines during reperfusion may be an important adjunct to predicting tissue injury along with ongoing inflammation during the clinical course of reperfusion injury. Within the vascular system, severe inflammatory responses are usually associated with thrombotic events. New techniques to noninvasively image thrombin activation (by using magnetic resonance imaging) in reperfused limbs may coincide with the pattern of murine skeletal muscle chemokine expression in humans. The data suggest that reperfusion is when chemokine mRNA and protein synthesis increase. Within the time periods studied in these experiments, the chemokine component of the inflammatory response remained in the reperfused, rather than the systemic nonreperfused, tissue. This observation may underestimate the degree of the systemic response to ischemia because the single mouse hind limb represents only 7% of the mouse total body area, whereas the human limb represents nearly 18% of the adult body area. Despite this shortcoming, these data provide potential temporal and quantitative information regarding the location and magnitude of chemokine synthesis in skeletal muscle during reperfusion.

Early outcomes of endovascular versus open abdominal aortic aneurysm repair in the National Surgical Quality Improvement Program-Private Sector (NSQIP-PS).

BACKGROUND: There remains no consensus on the appropriate application of endovascular abdominal aortic aneurysm repair (EVAR). Information from administrative databases, industry-sponsored trials, and single institutions has inherent deficiencies. This study was designed to compare early outcomes of open (OPEN) versus EVAR in a contemporary (2000 to 2003) large, multicenter prospective cohort. METHODS: Fourteen academic medical centers contributed data to the National Surgical Quality Improvement Program-Private Sector (NSQIP-PS), which ensures uniform, comprehensive, prospective, and previously validated data entry by trained, independent nurse reviewers. A battery of clinical and demographic features was assessed with multivariate analysis for association with the principal study end points of 30-day operative mortality and morbidity. RESULTS: One thousand forty-two patients underwent elective infrarenal abdominal aortic aneurysm (AAA) repairs: 460 EVAR and 582 OPEN. EVAR patients were older (74 vs 71 years, P < .0001), included more men (84.6% vs 79.6%, P < .05), and had a higher incidence of chronic obstructive pulmonary disease (25.4% vs 17.9%, P < .01). EVAR resulted in significantly reduced overall morbidity (24% vs 35%, P < .0001) and hospital stay (4 vs 9 days, P < .0001). Cardiopulmonary and renal function-related comorbidities had the expected significant impact on mortality for both procedures at univariate analysis ( P < .05). While crude mortality rates between EVAR and OPEN did not differ significantly (2.8% vs 4.0%) ( P = 0.32). After multivariate analysis, correlates of operative mortality included OPEN (odds ratio [OR], 2.44; 95% confidence interval [CI], 1.03 to 5.78; P < .05), advanced age (OR, 1.11; P < .001), history of angina (OR, 5.54; P < .01), poor functional status (OR, 5.78; P < .001), history of weight loss (OR, 7.42; P < .01), and preoperative dialysis (OR, 51.4; P < .0001). EVAR also compared favorably to OPEN (OR, 2.14; 95% CI, 1.58 to 2.89; P < .0001) for overall morbidity. CONCLUSION: Significant morbidity accompanies AAA repair, even at major academic medical centers. These data strongly endorse EVAR as the preferred approach in the presence of significant cardiopulmonary or renal comorbidities, or poor preoperative functional status.