Reduction of ischemia-reperfusion syndrome after abdominal aortic aneurysmectomy by N-acetylcysteine but not mannitol

Oxidative Stress, Endothelial Dysfunction, and N-Acetylcysteine in Type 2 Diabetes Mellitus

Significance: Cardiovascular diseases (CVDs) remain the leading cause of morbidity and mortality globally. Endothelial dysfunction is closely associated with the development and progression of CVDs. Patients with diabetes mellitus (DM) especially type 2 DM (T2DM) exhibit a significant endothelial cell (EC) dysfunction with substantially increased risk for CVDs. Recent Advances: Excessive reactive oxygen species (ROS) and oxidative stress are important contributing factors to EC dysfunction and subsequent CVDs. ROS production is significantly increased in DM and is critically involved in the development of endothelial dysfunction in diabetic patients. In this review, efforts are made to discuss the role of excessive ROS and oxidative stress in the pathogenesis of endothelial dysfunction and the mechanisms for excessive ROS production and oxidative stress in T2DM. Critical Issues: Although studies with diabetic animal models have shown that targeting ROS with traditional antioxidant vitamins C and E or other antioxidant supplements provides promising beneficial effects on endothelial function, the cardiovascular outcomes of clinical studies with these antioxidant supplements have been inconsistent in diabetic patients. Future Directions: Preclinical and limited clinical data suggest that N-acetylcysteine (NAC) treatment may improve endothelial function in diabetic patients. However, well-designed clinical studies are needed to determine if NAC supplementation would effectively preserve endothelial function and improve the clinical outcomes of diabetic patients with reduced cardiovascular morbidity and mortality. With better understanding on the mechanisms of ROS generation and ROS-mediated endothelial damages/dysfunction, it is anticipated that new selective ROS-modulating agents and effective personalized strategies will be developed for the management of endothelial dysfunction in DM.

N-Acetylcysteine and Atherosclerosis: Promises and Challenges

Atherosclerosis remains a leading cause of cardiovascular diseases. Although the mechanism for atherosclerosis is complex and has not been fully understood, inflammation and oxidative stress play a critical role in the development and progression of atherosclerosis. N-acetylcysteine (NAC) has been used as a mucolytic agent and an antidote for acetaminophen overdose with a well-established safety profile. NAC has antioxidant and anti-inflammatory effects through multiple mechanisms, including an increase in the intracellular glutathione level and an attenuation of the nuclear factor kappa-B mediated production of inflammatory cytokines like tumor necrosis factor-alpha and interleukins. Numerous animal studies have demonstrated that NAC significantly decreases the development and progression of atherosclerosis. However, the data on the outcomes of clinical studies in patients with atherosclerosis have been limited and inconsistent. The purpose of this review is to summarize the data on the effect of NAC on atherosclerosis from both pre-clinical and clinical studies and discuss the potential mechanisms of action of NAC on atherosclerosis, as well as challenges in the field.

Acute Cocaine Toxicity: Pharmacology and Clinical Presentations in Adult and Pediatric Populations

Cocaine remains the most prevalent drug responsible for emergency department (ED) visits. A majority of acute cocaine toxicity cases involve young, habitual, adult cocaine users and often present with a range of cardiac, neurologic, gastrointestinal (GI) or renal symptoms. In addition, atypical populations (neonates, infants, toddlers, young children and adolescents) are presenting in EDs with varying symptoms that are unknowingly associated with cocaine exposure. Unfortunately, juvenile presentations are generally anecdotal in nature, and while enlightening, are difficult to quantify epidemiologically. Outlining the types of symptom presentation in these young populations may assist healthcare providers in expediting proper treatment for such demographic groups. Therefore, this review examines the current knowledge regarding cocaine's pharmacologic activity as it relates to its potential toxicity, and outlines the clinical manifestations of cocaine exposure and toxicity in adult and pediatric populations. We conclude from the available clinical reports that there must be a higher index of suspicion in the pediatric population to identify exposed infants and children. Improved recognition and identification in both typical and atypical populations will result in better characterization of acute cocaine toxicity.

The effect of iloprost and N-acetylcysteine on skeletal muscle injury in an acute aortic ischemia-reperfusion model: an experimental study

Objective. The objective of this study was to examine the effects of iloprost and N-acetylcysteine (NAC) on ischemia-reperfusion (IR) injuries to the gastrocnemius muscle, following the occlusion-reperfusion period in the abdominal aorta of rats. Materials and Methods. Forty male Sprague-Dawley rats were randomly divided into four equal groups. Group 1: control group. Group 2 (IR): aorta was occluded. The clamp was removed after 1 hour of ischemia. Blood samples and muscle tissue specimens were collected following a 2-hour reperfusion period. Group 3 (IR + iloprost): during a 1-hour ischemia period, iloprost infusion was initiated from the jugular catheter. During a 2-hour reperfusion period, the iloprost infusion continued. Group 4 (IR + NAC): similar to the iloprost group. Findings. The mean total oxidant status, CK, and LDH levels were highest in Group 2 and lowest in Group 1. The levels of these parameters in Group 3 and Group 4 were lower compared to Group 2 and higher compared to Group 1 (P < 0.05). The histopathological examination showed that Group 3 and Group 4, compared to Group 2, had preserved appearance with respect to hemorrhage, necrosis, loss of nuclei, infiltration, and similar parameters. Conclusion. Iloprost and NAC are effective against ischemia-reperfusion injury and decrease ischemia-related tissue injury.

Effect of aminoguanidine on sciatic functional index, oxidative stress, and rate of apoptosis in an experimental rat model of ischemia-reperfusion injury

This study was conducted to investigate the potential protective effects of aminoguanidine (AG) on sciatic functional index (SFI), oxidative stress status, and apoptosis index using a rat model of experimental sciatic nerve ischemia-reperfusion injury (I/R). Treatment groups received 150 mg AG/kg body mass, 24 h after the induction of ischemia. After reperfusion for 2, 4, 7, 14, and 28 days, we evaluated measured SFI, plasma antioxidant enzymes, total antioxidant capacity (TAC), malondialdehyde (MDA), and index of apoptosis. SFI was significantly improved on the 7th and 14th day of reperfusion in the AG-treated groups. AG treatment resulted in the significant reduction of MDA levels on the 7th and 14th day of reperfusion. TAC was only increased after 7 days of reperfusion compared with the untreated group. SOD activity was decreased in both the untreated and AG-treated groups by comparison with the control, but did not show a significant change. GPx activity decreased only after 7 days of reperfusion. The maximal rate of apoptosis occurred on the 7th day of reperfusion. Treatment with AG significantly reduced this enhancement. AG exhibits positive effects against sciatic nerve I/R injury, possibly in part because of the protective effects of AG against apoptosis and I/R-induced oxidative stress.

Fatal early peripheral post-reperfusion syndrome and the role of cutaneous signs

The purpose of this report is to present the case of a 75-year-old male affected by right common femoral artery and abdominal aortic aneurysms. His clinical history was also characterised by post-ischaemic cardiomyopathy, arterial hypertension, chronic respiratory disease and peripheral arterial disease. We performed two surgical procedures: right femoral aneurysmectomy and femoro-femoral bypass and subsequently a femoro-femoral crossover bypass plus right femoro-popliteal bypass below the knee. The second operation became necessary in order to treat acute occlusion of the right iliac-femoral arterial axis. The patient developed a progressive and aggressive lower limb post-perfusion syndrome associated to frank peripheral oedema, myocardial stunning, reperfusion arrhythmias, renal failure and respiratory distress. Cutaneous alterations (oedema of the leg, mottled skin and cyanosis of the foot) were more specific compared with Doppler ultrasound that showed the presence of adequate blood flow in the early phase. On the basis of this experience and of pertinent literature, this study represents a challenge for the understanding of the exact mechanism of origin and progression of post-reperfusion syndrome.

Methylene blue attenuates pancreas ischemia-reperfusion (IR)-induced lung injury: a dose response study in a rat model

BACKGROUND

Oxidants (and their generator, xanthine oxidase [XO]) play a role in inducing acute lung injury (ALI) expressed both structurally and functionally. Such damage has recently been demonstrated in the presence of pancreas ischemia-reperfusion (IR). We now investigated whether methylene blue (MB), a clinically used coloring agent and antioxidant in itself, protected the lung exposed to pancreas IR.

MATERIALS AND METHODS

Isolated pancreata (eight replicates/group) were (1) continuously perfused (controls), (2) made ischemic (IR-0) for 40 min and reperfused without treatment, (3) organs procured from allopurinol-treated rats made ischemic and reperfused with allopurinol, and (4) made ischemic and treated upon reperfusion with three different doses of MB contained in the perfusate. All perfusate solutions were directed into the isolated lungs' circulation whereby they were perfused for 60 min.

RESULTS

Pancreas injury was documented in all IR organs by abnormally high reperfusion pressure, wet-to-dry ratio, amylase and lipase concentrations, and abnormal XO activity and reduced glutathione in the circulation. Lungs paired with IR-0 pancreata developed approximately 60% increase in ventilatory plateau pressure and final PO(2)/FiO(2) decrease by 35%. Their weight during reperfusion and bronchoalveolar lavage (BAL) volume and contents increased 1.5-2.5 times the normal values; XO and reduced glutathione values were abnormal both in the BAL and in the lung tissues. Lungs exposed to IR effluents containing allopurinol or 68 microM MB were minimally damaged, whereas perfusion solutions containing 42 or 128 microM MB were ineffective in preventing lung injury.

CONCLUSIONS

Ex vivo pancreas IR-induced ALI is preventable by MB, although at a narrow dose range.

Mannitol prevents acute lung injury after pancreas ischemia-reperfusion: a dose-response, ex vivo study

Oxidants and their generator, xanthine oxidase (XO), play a major role in the damaging of the structural and functional integrity of the lung. Such damage has been recently demonstrated in the presence of pancreas ischemia-reperfusion (IR). We investigated whether mannitol, a clinically used agent and antioxidant, prevented lung damage after pancreas IR. Rats (n = 48) were anesthetized, after which each pancreas was isolated and perfused (controls), or made ischemic (IR) for 40 min, or made ischemic and treated upon reperfusion with four different doses of mannitol administered in the perfusate (8 replicates/group). Ischemia was followed by in-series 15-min pancreas plus normal isolated lung reperfusion. Isolated lungs were subsequently perfused for 45 min with the 15-min accumulated effluents. Pancreas injury occurred in all IR organs as demonstrated by abnormal reperfusion pressure, the wet-to-dry ratio, amylase and lipase leakage into the circulation, and XO activity and reduced glutathione (GSH) pool in the tissues. Pulmonary plateau pressure increased by 80%, and final PO(2)/FiO(2) decreased by 28% in the IR-untreated paired lungs. Bronchoalveolar lavage volume increased by 50% and 2- to 8-fold increase in their contained XO and GSH were recorded as well. The above indices of injury in lungs perfused with 0.77 mM mannitol were the least detected, compared with negligible efficacy of other (0.55 < 0.22 < 1.1 mM) dosages. Amylase and lipase did not contribute to lung injury. Ex vivo acute pancreatitis induces acute lung injury via oxidants/antioxidants imbalance, which is preventable by mannitol.

Human atrial natriuretic peptide prevents the increase in pulmonary artery pressure associated with aortic unclamping during abdominal aortic aneurysmectomy

OBJECTIVE

To assess the effect of human atrial natriuretic peptide (HANP) on the pulmonary and systemic circulations during infrarenal abdominal aortic aneurysmectomy.

DESIGN

A prospective, randomized study.

SETTING

A university hospital.

PARTICIPANTS

Forty-five patients undergoing infrarenal abdominal aortic aneurysmectomy.

INTERVENTIONS

Abdominal aortic aneurysmectomy patients were randomly assigned to 1 of 3 groups (n = 15 for each group). They were infused with normal saline solution (SA), 0.02 microg/kg/min of HANP (LH), or 0.05 microg/kg/min of HANP (HH), starting 5 minutes after clamping. Hemodynamic variables were measured before/after clamping and unclamping.

MEASUREMENTS AND MAIN RESULTS

Both mean pulmonary arterial pressure (MPAP) and the pulmonary vascular resistance index (PVRI) increased (v baseline) in the SA group. HANP attenuated the rises in MPAP and PVRI dose dependently (LH and HH groups v SA). Mean arterial pressure and systemic vascular resistance index were not significantly different among the 3 groups.

CONCLUSION

HANP, infused during aortic clamping and abdominal aortic aneurysmectomy, attenuates the rises in pulmonary artery pressure and vascular resistance without severe systemic hypotension. This may result from direct and/or indirect pulmonary vascular effects of HANP because no HANP-induced changes in endothelin-1, angiotensin-II, and thromboxane B(2) were detected.

Mesenteric Artery Clamping/Unclamping-Induced Acute Lung Injury Is Attenuated by N-Methyl-D-Aspartate Antagonist Dextromethorphan

Lung N-methyl-D-aspartate receptors (NMDAR) may cause excitotoxic pulmonary edema if activated. Acute lung injury may be mediated by oxidative stress, frequently generated by local or remote ischemia and reperfusion (IR). This experimental study assessed the effects of intravenous dextromethorphan, an NMDAR antagonist, on reperfusion lung injury following superior mesenteric artery (SMA) clamping/unclamping. SMA of 48 (12 per group) anesthetized adult male Wistar rats was clamped for 90 min (IR); 48 additional rats underwent a sham laparotomy (control). The experimental timeframe was identical in all groups. Ten minutes before unclamping, three dextromethorphan doses were administered intravenously in three IR and three control groups, followed by 3 h of respiratory and hemodynamic assessment and postexperimental assessment of survival. Intravenous 10 and 20 mg/kg dextromethorphan attenuated an 85% increase in peak ventilatory pressure, a 45% reduction in PO(2)/FiO(2), 4-12-fold increase in bronchoalveolar lavage-retrieved volume, and polymorphonuclear leukocytes/bronchoalveolar cells ratio, all associated with SMA unclamping in the IR-nontreated and the IR-40 mg/kg dextromethorphan-treated rats. Lung tissue polymorphonuclear leukocyte count, total xanthine oxidase activity, reduced glutathione, and wet-to-dry weight ratio were all within normal ranges in the two lower-dose-treated groups. These effective regimens were also associated with longer postexperimental animal survival. Dextromethorphan was not associated with changes in three control groups. Thus, Intravenous dextromethorphan mitigates lung reperfusion injury following SMA clamping/unclamping in a dose-dependent manner. This is a novel potential use of dextromethorphan in vivo.

N-Acetylcysteine for the Prevention of Kidney Injury in Abdominal Aortic Surgery: A Randomized, Double-Blind, Placebo-Controlled Trial

In this prospective, randomized, placebo-controlled, double-blind trial we studied the effects of IV N-acetylcysteine for prevention of renal injury in patients undergoing abdominal aortic surgery. Seventy patients without previously documented renal dysfunction were randomly allocated to receive either N-acetylcysteine (150 mg/kg mixed in 250 mL of 5% dextrose infused in 20 min, followed by an infusion of 150 mg/kg in 250 mL of 5% dextrose over 24 h) or placebo. The infusion was started after the induction of anesthesia. The primary outcome measure was renal injury as measured by the increases in urinary N-acetyl-beta-d-glucosaminidase (NAG)/creatinine ratio (indicator of renal tubular injury) and urinary albumin/creatinine ratio (indicator of glomerular injury). Renal function was assessed by measuring plasma creatinine and serum cystatin C concentrations. The urinary NAG/creatinine ratio increased significantly from baseline to before crossclamp and remained increased on day 5 in both groups. The urinary albumin/creatinine ratio increased significantly from baseline to 6 h after declamping in the N-acetylcysteine group. However, the changes in the NAG/creatinine ratio and the albumin/creatinine ratio were not significantly different between the two groups. Plasma creatinine and serum cystatin C values remained unchanged during the study period in both groups. In conclusion, N-acetylcysteine did not offer any significant protection from renal injury during elective aortic operation in patients with normal preoperative renal function, and some degree of tubular injury seems to occur before aortic crossclamp.

Concomitant Administration of Mannitol and N-Acetylcysteine for the Prevention of Lung Reperfusion Injury

BACKGROUND

Mannitol (MN) and N- acetylcysteine (NAC) are partially successful in preventing lung reperfusion injury after liver ischemia reperfusion (IR). Their concomitant administration might enhance the individual effects of each.

METHODS

Rat isolated livers were perfused with Krebs-Henseleit solution (controls) or made globally ischemic (IR) for 2 hours. Separately isolated lungs were paired with livers and each pair was reperfused in-series for 15 minutes. During reperfusion, eight groups were treated with Krebs containing two low and two high doses of MN and/or NAC; one group received no treatment.

RESULTS

The tested lung parameters were unchanged in all control groups. Pulmonary perfusion or ventilatory pressures, weight gain and bronchoalveolar lavage volume increased by 30 to 70% of baseline in the nontreated IR-paired lungs and in the only IR-MN 0.44- and the IR-NAC 0.25 mmol (weight/body weight) treated lungs but remained preserved by the two higher monotherapies (MN 0.55 mmol and NAC 0.37 mmol) and by the four bitherapies. The reduced glutathione content in all lung tissue subgroups treated by the bitherapies was higher by 63 to 124% of the corresponding monotherapy values. Xanthine oxidase activity in the bitherapies-treated IR-lungs decreased 1.5 to twofold compared with the corresponding monotherapies.

CONCLUSIONS

Co-administration of MN and NAC augments the amount of lung protection afforded by each drug individually and enhances their antioxidant potentials.

Effects of ulinastatin on pulmonary artery pressure during abdominal aortic aneurysmectomy

STUDY OBJECTIVE

Abdominal aortic aneurysmectomy (AAAectomy) results in a general ischemia-reperfusion syndrome accompanied by an acute rise in pulmonary artery pressure (PAP). We examined whether ulinastatin, a urinary trypsin inhibitor, prevents ischemia-reperfusion injury and increase in PAP after aortic unclamping (XU) during AAAectomy.

DESIGN

Prospective study.

SETTING

Public, university-affiliated hospital.

PATIENTS

Sixteen patients (11 males and 5 females) scheduled for AAAectomy.

INTERVENTIONS AND MEASUREMENTS

The patients received 300000 IU of ulinastatin intravenously before XU (n = 8) or no additional treatment (n = 8) (control). Heart rate, central venous pressure, PAP, pulmonary arterial wedge pressure, arterial pressure, mixed venous oxygen saturation (Sv(O2)), and cardiac output were monitored. Arterial and mixed venous blood samples were analyzed for pH, Pa(CO2), Pa(O2), hemoglobin, and oxygen saturation, and the physiological shunt function (Qs/Qt) were calculated. Plasma concentrations of malondialdehyde, myeloperoxidase, granulocyte elastase, alpha1-antitrypsine, and thromboxane B2 and the stable hydrolysis products of thromboxane A2 were measured. Measurements were conducted before aortic crossclamping (XC) (baseline) and at 10, 30, and 60 minutes after XU.

MAIN RESULTS

A significant increase in PAP was observed 10 minutes after XU in the control group but not in the ulinastatin group. At 60 minutes after XU, Qs/Qt values had increased in the control group but had decreased in the ulinastatin group. There were no significant changes in malondialdehyde, thromboxane B2, granulocyte elastase, and alpha1-antitrypsine levels after XU in either group. A significant decrease in the plasma level of myeloperoxidase after XU was found in both groups.

CONCLUSIONS

The present study demonstrated that ulinastatin prevents increase in PAP and shunting after XU during AAAectomy.

A case of post-reperfusion syndrome following surgery for liver trauma

We report the case of a young trauma patient who needed tight perihepatic surgical packing to control bleeding from a ruptured liver. He developed severe cardiovascular and respiratory decompensation on removal of the surgical packs as a result of the post-reperfusion syndrome. He underwent a total hepatectomy and, 35 h later, orthotopic liver transplantation. The pathophysiology of post-reperfusion syndrome is discussed, and its importance to anaesthetists in the non-transplant setting is emphasized.

The effect of N-acetylcysteine on blood coagulation and platelet function in patients undergoing open repair of abdominal aortic aneurysm

N-acetylcysteine (NAC) may offer renal and hepatic protection during surgery, but in experimental studies it has been shown to impair coagulation. Since very little is known about the effects of NAC on blood coagulation in surgical patients, we studied its effects during abdominal aortic reconstruction. NAC (a bolus of 150 mg/kg followed by a continuous 24-h infusion of 150 mg/kg) or the same volume of placebo was given intravenously, in a randomized double-blinded fashion, to 20 patients undergoing abdominal aortic aneurysm repair. The haematocrit, platelet count, prothrombin time, thromboelastometry, and platelet aggregation were studied during and after surgery. Total blood loss was also measured. The median (25th-75th percentiles) decrease of the prothrombin time value was 33.0% (30-37%) after NAC treatment and 6.5% (4-8%) after placebo (P<0.001). Postoperative prothrombin time values remained lower in the patients receiving NAC. In thromboelastometry tracings the coagulation time was more prolonged after the bolus of NAC (P=0.02). Platelet aggregation induced with adenosine diphosphate decreased after NAC but not after placebo. Low prothrombin time values before and after bolus infusions were associated with increased blood loss (P=0.008 and P=0.015, respectively). NAC has anticoagulant and platelet-inhibiting properties in patients undergoing major vascular surgery. This abnormal haemostatic activity should be considered when NAC is administered to patients with increased bleeding risk.

Nitric Oxide and Skeletal Muscle Reperfusion Injury: Current Controversies (Research Review)

Nitric oxide (NO) has been implicated in a large number of disease processes, including ischemia-reperfusion injury following the restoration of oxygenated blood to previously ischemic muscle, which is a recognized significant complication of vascular surgery. Altered metabolism of NO is implicated in the endothelial dysfunction that forms part of the pathophysiology of ischemia-reperfusion injury. However, NO can demonstrate either protective or cytotoxic effects during reperfusion injury. The use of transgenic mice, either NO synthase (NOS) gene knockout animals, or animals that over-express NOS isoforms, along with direct NO measurements and NO donor or inhibitor studies, have all demonstrated a role for NO in skeletal muscle reperfusion injury. There appears to be an initial stimulation of NO production in the first 20-min of ischemia, with a gradual decline through early reperfusion and a second higher peak of NO commencing in the later stages of reperfusion. The absolute levels of NO in the reperfused tissue and its regulation by the subtle interplay with superoxide and the subsequent production of the highly toxic peroxynitrite anion, are important factors in determining whether NO, in the context of ischemia-reperfusion injury, has damaging or protective effects in the body.

N-Acetyl-L-Cysteine Mitigates Aortic Tone Injury Following Liver Ischemia-Reperfusion

Liver ischemia and subsequent reperfusion (IR) are associated with secondary, remote organ reperfusion injury attributable to oxidative stress mediators. Because N-acetyl-L-cysteine (NAC) was effective in attenuating lung reperfusion injury, its properties on aortic dysfunction were tested. Rat isolated perfused aortic rings (n = 8/group) were evaluated during and after exposure to liver postischemia perfusate. Aortic response to phenylephrine under these conditions was also assessed in the presence or absence of increasing concentrations of NAC. Aortic rings incubated with postischemia perfusates exhibited abnormally protracted contraction. Their response to phenylephrine was reduced to 18 +/- 7% and 65 +/- 11% of controls during and after the exposure, respectively, and their subsequent relaxation was irregular. NAC 0.25 mM best attenuated the IR-induced aortic tone impairments, 0.12 mM affected it slightly, and IR-NAC 0.5 mM and IR-NAC 0.74 mM solutions dilated the rings proportionately, abolishing reactions to both IR solutions and phenylephrine. Xanthine oxidase activity and reduced glutathione (GSH) level in all IR ring tissues were inversely proportionate, but not directly so. Thus, liver IR impaired aortic tone and its response to phenylephrine, even after removal of toxic elements. NAC concentrations directly and inversely correlated with xanthine oxidase activity but not with GSH level. It preserved aortic functions dose-specifically, mainly by oxidant quenching.

The effects of exogenous nitric oxide donor on motor functional recovery of reperfused peripheral nerve

PURPOSE

To investigate the effects of the nitric oxide donor S-nitroso-N-acetylcysteine (SNAC) on motor functional recovery of reperfused rat sciatic nerve.

METHODS

Seventy-eight rats were divided into groups treated with SNAC (100 nmol/100 g/min), methylprednisolone 30 mg/kg/h for 15 minutes, 45-minute pause, 5.4 mg/kg/h for 1.5 h), and phosphate-buffered saline 0.2 mL/100 g/h). A 1-cm segment of sciatic nerve had 2 hours of ischemia and the results were evaluated after various reperfusion periods using a walking track test, muscle contractile testing, muscle weight, and histology.

RESULTS

During reperfusion there was a significant overall improvement in sciatic functional index measurement and isometric titanic contractile force for the SNAC-treated group compared with the methylprednisolone- and phosphate-buffered saline- treated groups. The SNAC group had significantly earlier improvement in the sciatic functional index measurement between days 7 and 28. Restoration of the contractile force and muscle weight of the extensor digitorum longus muscle began earlier in the SNAC group--after day 11--whereas the other 2 groups showed progressive atrophy until day 21, with a significant difference between the SNAC group and the other 2 groups. Histologic examination showed that SNAC-treated rats had less severe degeneration and earlier regeneration of axons than the others. Although methylprednisolone-treated rats showed earlier recovery than phosphate-buffered saline-treated rats in all parameters there were no significant differences between these 2 groups.

CONCLUSIONS

Supplementation of nitric oxide is effective in promoting motor functional recovery of the reperfused peripheral nerve and has potential to replace or augment steroids as therapeutic agents in treatment of nervous system ischemia/reperfusion injury.

Evidence-based renal protection in cardiac surgery

Acute renal dysfunction is a common serious complication of cardiac surgery. Although a diversity of mechanisms exist by which the kidney can be damaged during cardiac surgery, atheroembolism, ischemia-reperfusion, and inflammation are believed to be primary contributors to perioperative renal insult. In addition, the high metabolic demands of active tubular reabsorption and the oxygen diffusion shunt characteristic of renal circulation make the kidney particularly vulnerable to ischemic injury. Remote effects of acute renal injury likely contribute to the strong association of this condition with other major postoperative morbidities and mortality and justify the search for renoprotective agents, even when dialysis is never required. Nonpharmacologic preventive strategies include procedure planning that is based on risk stratification, avoidance of nephrotoxins, and meticulous perioperative clinical care, including optimizing intravascular volume and attention to modifiable risk factors such as minimizing hemodilution. Although numerous pharmacologic interventions to prevent or treat acute renal injury have shown promise in animal models, randomized placebo-controlled clinical trials that have looked at measures of significant adverse outcomes such as death and dialysis have not confirmed a benefit.

Endovascular vs open AAA repair: similar effects on renal proximal tubular function

AIM

To compare the effect of open and endovascular repair on renal function.

MATERIALS AND METHODS

In a prospective, non-randomized study twenty-four abdominal aortic aneurysms (AAA) treatable with either method were repaired, 15 using endovascular device (ENDO group) and nine with open surgery with infrarenal aortic cross-clamping (OPEN group). All the patients had standardised general anaesthesia, intravascular fluid therapy and monitoring. Renal function tests and cardiovascular measurements were performed at predetermined intervals.

RESULTS

N-acetyl-beta-D-glucosaminidase indexed to urinary creatinine (U-NAG/crea), a sensitive marker of renal proximal tubular damage, increased similarly in both groups at the end of surgery (two-way ANOVA, p < 0.05). No patient developed clinical renal impairment, on the contrary, creatinine clearance was increased, serum cystatin C (a sensitive marker of renal glomerular filtration) and serum creatinine concentration decreased at 24 hours postoperatively (Wilcoxon paired test, p < 0.05). Intraoperative blood loss and the amount of administered crystalloids were higher in the OPEN than in the ENDO group (Mann-Whitney U-test, p < 0.05). The cardiovascular measurements were comparable between the groups. The mean (SD) amount of radio-contrast media given was 3.1 (1.1) ml/kg in the ENDO group.

CONCLUSIONS

Our results indicate that endovascular AAA repair does not protect renal proximal tubular function. A temporary renal tubular dysfunction was found both in open and in endovascular AAA repair which did not lead to permanent changes in renal function.

Methylene blue attenuates lung injury after mesenteric artery clamping/unclamping

BACKGROUND

This controlled, experimental study was designed to assess the effects of intratracheal and intravenous methylene blue on reperfusion lung injury following superior mesenteric artery clamping/unclamping.

MATERIALS AND METHODS

Superior mesenteric arteries of 144 anaesthetized adult male Wistar rats (n = 12/group) were clamped for 1 h. Ten minutes before unclamping, methylene blue or its vehicle was administered intratracheally or intravenously, followed by a 3 h-respiratory assessment and postexperimental assessment of survival.

RESULTS

Intravenous 3 and 9 mg kg(-1) but not higher methylene blue doses, and intratracheal 6-mg kg(-1) but not lower doses, significantly (P < 0.05) reduced the 100% increase in plateau pressure, 30% reduction in PO(2)/FiO(2), fourfold augmented bronchoalveolar lavage-retrieved volume and the increased polymorphonuclear leukocytes/bronchoalveolar cells' ratio associated with unclamping of the superior mesenteric artery. Lung tissue polymorphonuclear leukocytes count, total xanthine oxidase activity and wet-to-dry-weight ratio were also normal in these dose-treated groups. These effective regimens were also associated with longer animal survival.

CONCLUSIONS

Intratracheal methylene blue mitigates lung reperfusion injury following superior mesenteric artery clamping/unclamping at a similar magnitude as an intravenous regimen. This finding is a novel potential use of methylene blue in vivo.

Attenuation of liver ischemia-reperfusion-induced atrial dysfunction by external pacing but not by isoproterenol

Remote ischemia–reperfusion detrimentally affects myocardial function by initially interfering with the rate of contraction. We investigated the usefulness of isoproterenol versus external electrical pacing in attenuating secondary functional damage of isolated Wistar rat atria. Atrial strips (n = 10/group) were bathed within oxygenated Krebs–Henseleit solution that exited from isolated livers that had been either perfused normally (controls) or underwent no flow (ischemia) for 2 h. In addition to one noninterventional ischemia-exposed strip group, a second group was externally paced at a fixed rate (55 pulses·min–1, 6 V) and a third "ischemia" group was treated with isoproterenol (0.1 mM), both interventions commencing upon the strips' exposure to the hepatic effluents. Control strips displayed unaltered contraction rate and systolic-generated tension during the 2-h exposure. Nontreated strips exposed to ischemic reperfusate experienced bradycardia compared with baseline values (7 ± 2 vs. 50 ± 12 beats·min–1, p < 0.05), followed <1-min later by a fall in the generated tension (11 ± 4 vs. 20 ± 6 mmHg, p < 0.05). The paced-ischemic strips displayed unaltered rate and force of contraction, whereas the addition of isoproterenol did not prevent deterioration in the rate and force of contraction (8 ± 3 beats·min–1, 12 ± 4 mmHg, respectively; p < 0.05 vs. baseline control ischemia-paced strips). Thus, external electrical pacing prevented liver ischemia–reperfusion-induced atrial strips' bradycardia and loss of contractility, while isoproterenol did not.Key words: ischemia, reperfusion, liver, atrium, dysfunction, isoproterenol, pacing.

Hepatic ischemia-reperfusion syndrome after partial liver resection (LR): hepatic venous oxygen saturation, enzyme pattern, reduced and oxidized glutathione, procalcitonin and interleukin-6

The hepatic ischemia-reperfusion syndrome was investigated in 28 patients undergoing elective partial liver resection with intraoperative occlusion of hepatic inflow (Pringle maneuver) using the technique of liver vein catheterization. Hepatic venous oxygen saturation (ShvO2) was monitored continuously up to 24 hours after surgery. Aspartate aminotransferase, glutamate dehydrogenase, gamma-glutamyl transpeptidase, pseudocholinesterase, alpha-glutathione S-transferase, reduced and oxidized glutathione, procalcitonine, and interleukin-6 were serially measured both before and after Pringle maneuver during the resection and postoperatively in arterial and/or hepatic venous blood. ShvO2 measurement demonstrated that peri- and postoperative management was suitable to maintain an optimal hepatic oxygen supply. As expected, we were able to demonstrate a typical enzyme pattern of postischemic liver injury. There was a distinct decrease of reduced glutathione levels both in arterial and hepatic venous plasma after LR accompanied by a strong increase in oxidized glutathione concentration during the phase of reperfusion. We observed increases in procalcitonin and interleukin-6 levels both in arterial and hepatic venous blood after declamping. Our data support the view that liver resection in man under conditions of inflow occlusion resulted in ischemic lesion of the liver (loss of glutathione synthesizing capacity with disturbance of protection against oxidative stress) and an additional impairment during reperfusion (liberation of reactive oxygen species, local and systemic inflammation reaction with cytokine production). Additionally, we found some evidence for the assumption that the liver has an export function for reduced glutathione into plasma in man.

Changes in cerebral microcirculation during and after abdominal aortic cross-clamping in rabbits: the role of thromboxane A2 receptor

Little is known about any changes in cerebral hemodynamics, during and after abdominal aortic cross-clamping and unclamping, especially in the cerebral microcirculation. We studied the effects of abdominal aortic cross-clamping and unclamping on cerebral pial vessel diameter in the presence or absence of the thromboxane (Tx)A(2) receptor antagonist using a closed cranial window in 27 rabbits. Although infrarenal aortic cross-clamping did not affect pial vessel diameter, release of a 20-min aortic cross-clamp caused pial arterioles to dilate and then constrict. A significant constriction persisted for at least 60 min (maximum, -17% for large [> or =75 micro m] and -28% for small arterioles [<75 micro m] compared with baseline). Topical administration of a TxA(2) receptor antagonist, seratrodast, at 10(-7) M and 10(-6) M, significantly attenuated the constriction of large and small arterioles (at 60 min, -9% and -13% constriction for 10(-7) M, and -6% and -7% for 10(-6) M). Release of a 20-min aortic cross-clamp induced a sustained pial arteriolar constriction. Because this unclamping-induced vasoconstriction was attenuated by topical administration of seratrodast, it was likely partially mediated via the washout of TxA(2) produced in the ischemic region during the clamp and after cross-clamp release.

IMPLICATIONS

Abdominal aortic unclamping after a 20-min clamp caused an initial dilation followed by a sustained constriction of pial arterioles. Seratrodast, a thromboxane A(2) receptor antagonist, attenuated the vasoconstriction suggesting that it is at least partly mediated by thromboxane A(2) washed out from the region rendered ischemic by clamping.

A multiantioxidant supplementation reduces damage from ischaemia reperfusion in patients after lower torso ischaemia. A randomised trial

BACKGROUND

open repair of intra-abdominal aortic aneurysm (AAA) is associated with lower torso ischaemia and reperfusion.

OBJECTIVE

to examine the effect of antioxidants on the activation and sequestration of white blood cells and muscle injury during AAA repair.

METHOD

forty-two patients undergoing elective infrarenal aneurysm repair, were randomised to either standard therapy (22 patients) or standard therapy with additional multiantioxidant supplementation (20 patients). Vitamin E and C, Allopurinol, N-acetylcysteine and mannitol was administered perioperatively. White blood cell count (WBC), serum creatine kinase, aspartateaminotransferase, lactate and lipofuscine were measured.

RESULTS

WBC remained higher after reperfusion in the antioxidant group (p = 0.008). CK, ASAT and lipofuscine levels were significantly lower after reperfusion in the antioxidant group (p = 0.02, p = 0.018, p = 0.017).

CONCLUSION

multi-antioxidant supplementation was associated with a reduction in serum CK and ASAT after AAA repair. This is likely due to a reduction in oxidative stress and a decreased leucocyte sequestration and activation.

Selective attenuation of acute lung ventilatory injury by methylene blue after liver ischemia-reperfusion: a drug response study in an isolated perfused double organ model

BACKGROUND

Liver transplantation-related ischemia-reperfusion (IR) is associated with the generation of stress oxidants that can spread damage remotely. Methylene blue (MB) had been shown to reduce lung neutrophils sequestration after in vivo intestinal IR and to have a dose-dependent potential for abrogating oxidant-induced ex vivo aortal ring reperfusion injury after liver IR. We now investigated MB's dose-dependent capabilities in preventing acute lung injury after the same liver IR.

METHODS

Wistar rat livers (eight replicates/group) were perfused (control) with modified Krebs-Henseleit solution or put globally in no flow (IR) conditions for 2 hr. Separately prepared lungs were then paired with livers and "reperfused" (15 min) together. The livers were then removed, and the lungs were left to recirculate alone with the accumulated Krebs for 45 min. Three additional control and three IR groups were reperfused with Krebs containing 20, 40, or 60 mg/kg MB at concentrations of 42, 86, or 128 microM.

RESULTS

All IR livers had hepatocellular and biochemical abnormalities compared with normal functions in the controls. Liver IR was associated with a 50%-75% increase in lung ventilation and perfusion pressures, vascular resistance and decreased compliance, and abnormal bronchoalveolar lavage (BAL) volume and content. Adding 42 and 86 microM MB selectively maintained normal the vascular parameters, intra-experimental lung weight gain, BAL indices, and wet-to-dry ratios. MB128 microM but not 42 or 86 microM best prevented IR-induced deterioration in lung ventilatory pressure and compliance.

CONCLUSIONS

MB selectively affords maintenance of normal lung ventilatory versus vascular measures after liver ischemia-reperfusion. Its proposed differential mechanism of action is discussed.

S-nitroso-N-acetylcysteine protects skeletal muscle against reperfusion injury

The effects of a nitric oxide (NO) donor on microcirculation and contractile function of reperfused skeletal muscle were studied. Rat cremaster muscles underwent 5 hours of ischemia and 90 minutes of reperfusion and were divided into two groups systemically infused with S-nitroso-N-acetylcysteine (SNAC, 100 nmol/min) and phosphate-buffered saline (PBS), respectively. The results showed that the vessels in the SNAC group had more rapid and complete recovery than that in controls. A significant difference was found from 10 to 40 minutes and at 90 minutes in 10-20-microm arterioles, from 10 to 90 minutes in 20-40-microm arterioles, and at 10 and 90 minutes in 40-70-microm arteries. When compared to controls, SNAC-treated muscles showed larger fluorescein filling areas at 15, 30, 60, and 90 minutes and greater isometric tetanic contractile forces in response to stimulation frequencies of 40, 70, 100, and 120 Hz. The data indicate that supplementation of exogenous NO could effectively improve microcirculation and contractile function of skeletal muscle during early reperfusion.

Impairment of aortal tone by no flow-reflow conditions and its partial amelioration by mannitol

BACKGROUND

Although postischemic cardiac or pulmonary dysfunction can relate to the impact of remotely generated oxygen stress mediators on the heart, their direct effect on the vascular bed remains unresolved. Thus, we tested these remote effects in an ex-vivo double organ model.

METHODS

After stabilization With Krebs-Henseleit solution, isolated rat livers were either perfused or made ischemic for 2 hours. Aortic rings were stabilized, immersed in postischemic liver perfusates and their functions were tested. Some organs originated from donors fed with tungstate, whereas others had mannitol (0.25 g/kg) in the buffer.

RESULTS

Incubation of aortic rings with postischemic hepatic effluent resulted in protracted contraction. Spasm was slightly lesser when the livers were pretreated with tungstate or exposed to mannitol, but worse in pretreated rings. The return to basal tone was abrupt in all ischemia-reperfusion aortae. The response of the rings to phenylephrine under the influence of the ischemia-reperfusion hepatic effluent was deficient. Mannitol prevented most abnormal responses.

CONCLUSIONS

Aortal tone impairment can occur by direct influence of the ischemia-reperfusion liver. It cannot be attributed entirely to xanthine oxidase, but also to other hepatic-released factors.

Suppression of interleukin 2 biosynthesis by three modes of oxidative cellular stress: selective prevention by N-acetyl cysteine

Acute stress induced by reagent hydrogen peroxide suppressed interleukin (IL-)2 biosynthesis in a dose-dependent fashion, reaching almost complete abolishment at 200 microM. Cells exposed to longitudinal oxidative stress and irradiation did not exhibit complete suppression of IL-2 biosynthesis, probably because intensities high enough to achieve such response would be lethal. These results suggest that suppression of IL-2 biosynthesis is a sensitive measure of acute oxidative stress. N-acetyl cysteine (NAC) prevented oxidative stress-induced suppression of IL-2 biosynthesis, except for that induced by acute stress at 100 microM and above. NAC was very efficient in preventing longitudinal and irradiation-induced stresses. Therefore, NAC appears to be a promising candidate for providing defence to individuals exposed to environmental conditions in which reactive oxygen intermediates are generated.

Middle cerebral artery flow velocity and cerebral oxygenation during abdominal aortic surgery

Cerebral perfusion was evaluated in twelve patients undergoing elective infra-renal abdominal aortic aneurysmectomy by transcranial Doppler ultrasonography-determined middle cerebral artery mean flow velocity, near-infrared spectroscopy-assessed cerebral oxygen saturation and systemic haemodynamic variables. The middle cerebral artery mean flow velocity and cerebral oxygen saturation decreased during cross-clamping of the aorta, and both increased upon declamping of the aorta with the oxygen saturation change lagging behind the change in the flow velocity. The changes in cerebral flow velocity and oxygen saturation paralleled the deviations in cardiac output and end-tidal carbon dioxide tension.

Lesão pulmonar de reperfusão

A lesão de isquemia-reperfusão constitui-se em um evento fisiopatológico comum a diversas doenças da prática clínica diária. O pulmão pode ser alvo da lesão de isquemia-reperfusão diretamente, como no edema pulmonar após transplante ou na resolução de tromboembolismo; ou ainda ser atingido à distância, como nos casos de choque ou por lesão de reperfusão em intestino ou em membros inferiores, como ocorre no pinçamento da aorta, utilizado nas cirurgias de aneurisma. Dentre os mediadores envolvidos na lesão de isquemia-reperfusão, foram identificados espécies reativas tóxicas de oxigênio (ERTO), mediadores lipídicos, como a tromboxana, moléculas de adesão em neutrófilos e endotélio, fator de necrose tumoral, dentre outros. As medidas terapêuticas para a lesão de reperfusão ainda são utilizadas no plano experimental e em poucos estudos clínicos. São utilizados: antioxidantes, bloqueadores de mediadores lipídicos, inibidores da interação entre leucócito e endotélio ou substâncias que favoreçam o fluxo sanguíneo pós-isquêmico.