Hypoxemic reperfusion of ischemic states: an alternative approach for the attenuation of oxidative stress mediated reperfusion injury.

Ischemia and reperfusion (I/R) - induced injury has been described as one of the main factors that contribute to the observed morbidity and mortality in a variety of clinical entities, including myocardial infarction, ischemic stroke, cardiac arrest and trauma. An imbalance between oxygen demand and supply, within the organ beds during ischemia, results in profound tissue hypoxia. The subsequent abrupt oxygen re-entry upon reperfusion, may lead to a burst of oxidative aggression through production of reactive oxygen species by the primed cells. The predominant role of oxidative stress in the pathophysiology of I/R mediated injury, has been well established. A number of strategies that target the attenuation of the oxidative burst have been tested both in the experimental and the clinical setting. Despite these advances, I/R injury continues to be a major problem in everyday medical practice. The aim of this paper is to review the existing literature regarding an alternative approach, termed hypoxemic reperfusion, that has exhibited promising results in the attenuation of I/R injury, both in the experimental and the clinical setting. Further research to clarify its underlying mechanisms and to assess its efficacy in the clinical setting is warranted.

Effect of clarithromycin in patients with suspected Gram-negative sepsis: results of a randomized controlled trial.

BACKGROUND: A previous randomized study showed that clarithromycin decreases the risk of death due to ventilator-associated pneumonia and shortens the time until infection resolution. The efficacy of clarithromycin was tested in a larger population with sepsis. METHODS: Six hundred patients with systemic inflammatory response syndrome due to acute pyelonephritis, acute intra-abdominal infections or primary Gram-negative bacteraemia were enrolled in a double-blind, randomized, multicentre trial. Clarithromycin (1 g) was administered intravenously once daily for 4 days consecutively in 302 patients; another 298 patients were treated with placebo. Mortality was the primary outcome; resolution of infection and hospitalization costs were the secondary outcomes. RESULTS: The groups were well matched for demographics, disease severity, microbiology and appropriateness of the administered antimicrobials. Overall 28 day mortality was 17.1% (51 deaths) in the placebo arm and 18.5% (56 deaths) in the clarithromycin arm (P = 0.671). Nineteen out of 26 placebo-treated patients with septic shock and multiple organ dysfunctions died (73.1%) compared with 15 out of 28 clarithromycin-treated patients (53.6%, P = 0.020). The median time until resolution of infection was 5 days in both arms. In the subgroup with severe sepsis/shock, this was 10 days in the placebo arm and 6 days in the clarithromycin arm (P = 0.037). The cost of hospitalization was lower after treatment with clarithromycin (P = 0.044). Serious adverse events were observed in 1.3% and 0.7% of placebo- and clarithromycin-treated patients, respectively (P = 0.502). CONCLUSIONS: Intravenous clarithromycin did not affect overall mortality; however, administration shortened the time to resolution of infection and decreased the hospitalization costs.

Nitrosative and oxidative stresses contribute to post-ischemic liver injury following severe hemorrhagic shock: the role of hypoxemic resuscitation.

PURPOSE: Hemorrhagic shock and resuscitation is frequently associated with liver ischemia-reperfusion injury. The aim of the study was to investigate whether hypoxemic resuscitation attenuates liver injury. METHODS: Anesthetized, mechanically ventilated New Zealand white rabbits were exsanguinated to a mean arterial pressure of 30 mmHg for 60 minutes. Resuscitation under normoxemia (Normox-Res group, n = 16, PaO(2) = 95-105 mmHg) or hypoxemia (Hypox-Res group, n = 15, PaO(2) = 35-40 mmHg) followed, modifying the FiO(2). Animals not subjected to shock constituted the sham group (n = 11, PaO(2) = 95-105 mmHg). Indices of the inflammatory, oxidative and nitrosative response were measured and histopathological and immunohistochemical studies of the liver were performed. RESULTS: Normox-Res group animals exhibited increased serum alanine aminotransferase, tumor necrosis factor--alpha, interleukin (IL) -1ß and IL-6 levels compared with Hypox-Res and sham groups. Reactive oxygen species generation, malondialdehyde formation and myeloperoxidase activity were all elevated in Normox-Res rabbits compared with Hypox-Res and sham groups. Similarly, endothelial NO synthase and inducible NO synthase mRNA expression was up-regulated and nitrotyrosine immunostaining increased in animals resuscitated normoxemically, indicating a more intense nitrosative stress. Hypox-Res animals demonstrated a less prominent histopathologic injury which was similar to sham animals. CONCLUSIONS: Hypoxemic resuscitation prevents liver reperfusion injury through attenuation of the inflammatory response and oxidative and nitrosative stresses.

Hypoxemic resuscitation from hemorrhagic shock prevents lung injury and attenuates oxidative response and IL-8 overexpression.

We investigated whether hypoxemic resuscitation from hemorrhagic shock prevents lung injury and explored the mechanisms involved. We subjected rabbits to hemorrhagic shock for 60 min by exsanguination to a mean arterial pressure of 40 mm Hg. By modifying the fraction of the inspired oxygen, we performed resuscitation under normoxemia (group NormoxRes, P(a)O(2)=95-105 mm Hg) or hypoxemia (group HypoxRes, P(a)O(2)=35-40 mm Hg). Animals not subjected to shock constituted the sham group (P(a)O(2)=95-105 mm Hg). We performed bronchoalveolar lavage (BAL) fluid, lung wet-to-dry weight ratio, and morphological studies. U937 monocyte-like cells were incubated with BAL fluid from each group. Cell peroxides, malondialdehyde, proteins, and cytokines in the BAL fluid were lower in sham than in shocked animals and in HypoxRes than in NormoxRes animals. The inverse was true for ascorbic acid and reduced glutathione. Lung edema, lung neutrophil infiltration, myeloperoxidase, and interleukin (IL)-8 gene expression were reduced in lungs of HypoxRes compared with NormoxRes animals. A colocalized higher expression of IL-8 and nitrotyrosine was found in lungs of NormoxRes animals compared to HypoxRes animals. The BAL fluid of NormoxRes animals compared with HypoxRes animals exerted a greater stimulation of U937 monocyte-like cells for proinflammatory cytokine release, particularly for IL-8. In the presence of p38-MAPK and Syk inhibitors and monosodium urate crystals, IL-8 release was reduced. We conclude that hypoxemic resuscitation from hemorrhagic shock ameliorates lung injury and reduces oxygen radical generation and lung IL-8 expression.

Oral atovaquone for the treatment of severe Pneumocystis jirovecii pneumonia in a patient with glucose-6-phosphate dehydrogenase deficiency.

We present a case of severe Pneumocystis jirovecii pneumonia and coexisting cytomegalovirus infection in a glucose-6-phosphate dehydrogenase (G6PD) enzyme deficient woman with anaplastic astrocytoma on temozolomide and corticosteroid therapy. She was successfully treated with oral atovaquone and ganciclovir. Atovaquone represents a safe alternative in severe Pneumocystis infection when trimethoprim-sulfamethoxazole (co-trimoxazole) is contraindicated.

Administration of human protein C improves survival in an experimental model of sepsis.

OBJECTIVE: Study the effect of human protein C (PC) concentrate administration on organ damage and survival in septic rats. DESIGN: Animal study. SETTING: University laboratory. SUBJECTS: Male Wistar rats. INTERVENTIONS: Cecal ligation and puncture (CLP) was performed in 210 rats. Rats were randomly assigned to receive either human protein C (PC) IV 1, 7, and 13 hrs after CLP (CLP+PC) or placebo (CLP). Septic animals were again randomized in a survival group (CLP: n = 50 and CLP+PC: n = 40) that was monitored for 60 hrs and time groups (CLP: n = 60 and CLP+PC: n = 60) that were killed at 6, 12, 24, 36, 48, and 60 hrs after CLP. Brain, heart, lung, liver, kidney, gastric, and colon tissue were removed and postfixed in paraffin sections. MEASUREMENTS AND MAIN RESULTS: PC infusion increased PC serum levels in early sepsis (median 7.25) compared with late sepsis (median 2, p = .001). Activated protein C/a1-antitrypsin complex levels in the CLP+PC group were significantly increased in late sepsis (60 hrs after CLP) compared with early sepsis (6, 12, and 24 hrs after CLP, p = .009, p = .004, and p = .008, respectively) and to late septic CLP and normal rats (p = .005 and p = .007, respectively). Their IL-6 and tumor necrosis factor a plasma levels were decreased (by 27% and 25%, respectively) at 6 hrs compared with placebo (p = .008 and p = .016). Their serum PC levels were also decreased in CLP+PC survivors compared with nonsurvivors of the same group (median = 1.5 vs. median = 7, p = .001). Apoptosis was reduced in brain (10% vs. 77.8%, p < .001), stomach (66.7% vs. 100%, p < .002) and intestine (33.3% vs. 85.2%, p < .001) compared with placebo. Finally, the survival of septic rats treated with human PC was significantly increased compared with placebo (75% vs. 54%, p = .033). CONCLUSIONS: Human Protein C administration increased survival in septic rats, decreased plasma inflammatory cytokines levels and tissue injury in vital organs.

Reasons of PEG failure to eliminate gastroesophageal reflux in mechanically ventilated patients.

AIM: To investigate factors predicting failure of percutaneous endoscopic gastrostomy (PEG) to eliminate gastroesophageal reflux (GER). METHODS: Twenty-nine consecutive mechanically ventilated patients were investigated. Patients were evaluated for GER by pH-metry pre-PEG and on the 7th post-PEG day. Endoscopic and histologic evidence of reflux esophagitis was also carried out. A beneficial response to PEG was considered when pH-metry on the 7th post-PEG day showed that GER was below 4%. RESULTS: Seventeen patients responded (RESP group) and 12 did not respond (N-RESP) to PEG. The mean age, sex, weight and APACHE II score were similar in both groups. GER (%) values were similar in both groups at baseline, but were significantly reduced in the RESP group compared with the N-RESP group on the 7th post-PEG day [2.5 (0.6-3.8) vs 8.1 (7.4-9.2, P < 0.001)]. Reflux esophagitis and the gastroesophageal flap valve (GEFV) grading differed significantly between the two groups (P = 0.031 and P = 0.020, respectively). Histology revealed no significant differences between the two groups. CONCLUSION: Endoscopic grading of GEFV and the presence of severe reflux esophagitis are predisposing factors for failure of PEG to reduce GER in mechanically ventilated patients.

High concentrations of reactive oxygen species in the BAL fluid are correlated with lung injury in rabbits after hemorrhagic shock and resuscitation.

Increased levels of cytokines or reactive oxygen species (ROS) in the bronchoalveolar lavage (BAL) fluid are associated with acute lung injury after ischemia/reperfusion. We investigated the correlation of these markers with the degree of lung injury in a rabbit model of hemorrhagic shock. Rabbits, maintained by mechanical ventilation, were left untreated (control) or subjected to hemorrhagic shock by withdrawing blood (n = 12 for each group). Shock animals were re-infused their shed blood for resuscitation. At the end of the experiment, BAL fluid was recovered, in which parameters of oxidative stress and cytokines were measured. Macrophages and malondialdehyde levels were increased (p = 0.043 and p = 0.003, respectively), and total antioxidant capacity (TAC) was decreased in the shock animals compared with control (p = 0.009). Production of ROS was significantly enhanced in shock animals compared with controls (p < 0.001). BAL fluid levels of tumor necrosis factor-alpha, interleukin (IL)-1beta and IL-6 were higher in shock rabbits by more than twofold (p < 0.001 for each). Shock animals also showed higher histopathological scores that represent severe tissue damage than controls (p = 0.022). Numbers of macrophages and levels of ROS and TAC were correlated with the degree of lung injury (p = 0.006, p = 0.02, and p = 0.04, respectively), but not cytokines. Therefore, resuscitation from hemorrhagic shock results in acute lung injury, with enhanced pulmonary oxidative and inflammatory responses. In conclusion, ROS in the BAL fluid are good markers that predict lung injury following hemorrhagic shock and resuscitation.

Ampicillin-sulbactam: an update on the use of parenteral and oral forms in bacterial infections.

Ampicillin-sulbactam has a wide range of antibacterial activity that includes Gram-positive and Gram-negative aerobic and anaerobic bacteria. However, the drug is not active against Pseudomonas aeruginosa and pathogens producing extended-spectrum beta-lactamases. The combination could be considered particularly active against Acinetobacter baumannii infections due to the intrinsic activity of sulbactam. The drug is indicated as empirical therapy for a broad range of community acquired infections supervened in adults or children and is effective in either parenteral (ampicillin-sulbactam) or oral (as a mutual prodrug sultamicillin) form. In clinical trials, sultamicillin has proved clinically and bacteriologically effective in adults and children against a variety of frequently encountered infections, including mild upper and lower respiratory tract infections, urinary tract infections, diabetic foot and skin and soft tissue infections. Furthermore, adverse effects rarely occur with the diarrhoea to represent the most commonly reported. The parenteral ampicillin-sulbactam is indicated for community infections of mild-to-moderate severity acquired infections such as intra-abdominal or gynecological. Moreover, it seems to represent the alternative of choice for the treatment of A. baumannii infections for carbapenem-resistant strains in the nosocomial setting. Thus, ampicillin-sulbactam remains a valuable agent in the physician's armamentarium in the management of adult and pediatric infections.

Hypoxemic resuscitation after hemorrhagic shock is accompanied by reduced serum levels of angiopoietin-2.

BACKGROUND: To investigate whether angiopoietin-2 (Ang2) and vascular endothelial growth factor (VEGF) are implicated in the hypoxemic resuscitation from hemorrhagic shock. METHODS: Twenty rabbits were subjected to hemorrhagic shock after blood exsanguination; resuscitation was performed by infusion of the shed blood in ten rabbits under normoxemic conditions (NormoxRes) and in 10 under hypoxemic conditions (HypoxRes); four rabbits were subjected to sham operation. Serum was drawn at serial time intervals; serum was applied for stimulation of U937 monocytes. RESULTS: Serum concentrations of Ang2 were higher in the NormoxRes group compared to the HypoxRes group at 90 min (p: 0.049) and at 120 min (p: 0.028). Serum concentrations of VEGF did not differ between groups. Concentrations of VEGF in the supernatants of U937 stimulated with sera of all groups were below detection limit. The wet to dry lung ratio of the HypoxRes group was significantly lower than the NormoxRes group (p<0.0001). CONCLUSIONS: Hypoxemic resuscitation from hemorrhagic shock is a process accompanied by reduced serum levels of Ang2. These findings add significantly to our understanding of that experimental treatment strategy of resuscitation.

Hypoxemic resuscitation prevents pulmonary capillary endothelial dysfunction induced by normoxemic resuscitation from hemorrhagic shock.

OBJECTIVE: Hypoxemic reperfusion attenuates brain injury secondary to severe cerebral ischemia, myocardial, and intestinal injury occurring in intestinal postischemic shock, and offers hemodynamic stabilization and attenuation of inflammatory response when applied in the resuscitation from hemorrhagic shock. In this study, we sought to investigate the effect of hypoxemic resuscitation on pulmonary endothelium. DESIGN: Prospective, randomized, controlled animal study. SETTING: Experimental laboratory of a university intensive care unit. SUBJECTS: Male New Zealand White rabbits weighting 3-3.5 kg. INTERVENTIONS: Hemorrhagic shock at mean arterial pressure of 40 mm Hg was induced by exsanguinations in anesthetized, mechanically ventilated animals for 60 minutes and thereafter rabbits were resuscitated by homologous blood and Ringer's lactate infusion under normoxemia (Normox-Res group, Pao2 = 95-105 mm Hg, n = 9) or hypoxemia (Hypox-Res group, Pao2 = 35-40 mm Hg, n = 7). MEASUREMENTS AND MAIN RESULTS: Using indicator-dilution techniques we measured at baseline and post resuscitation pulmonary capillary endothelial angiotensin converting enzyme activity expressed as percentage of metabolism (%M) and hydrolysis (v) of the substrate H-benzoyl-Phe-Ala-Pro. Normox-Res rabbits exhibited decreased %M (p < 0.05) and v (p < 0.05) post resuscitation as compared with baseline, while no differences occurred in the Hypox-Res group. Myeloperoxidase was measured in lung tissue and was higher in Normox-Res than Hypox-Res animals (p < 0.01). Lung injury was estimated microscopically, whereas the expression of the intercellular adhesion molecule-1 and the vascular cell adhesion molecule-1 were assessed by immunohistochemistry on sections coming from the same tissue block. Compared with Normox-Res, Hypox-Res animals exhibited lower lung injury histopathological score (p < 0.01) and lung malondialdehyde concentration (p < 0.01), and lower intercellular adhesion molecule-1 and vascular cell adhesion molecule-1 expressions in both the inflammatory cells (p < 0.01) and the blood vessels (p < 0.05). CONCLUSIONS: Normoxemic resuscitation of hemorrhagic shock is associated with pulmonary endothelial dysfunction and lung injury that may be attenuated by hypoxemic resuscitation.

The level of hypotension during hemorrhagic shock is a major determinant of the post-resuscitation systemic inflammatory response: an experimental study.

BACKGROUND: To evaluate whether the level of hypotension during hemorrhagic shock may influence the oxidative and inflammatory responses developed during post-ischemic resuscitation. METHODS: Fifteen rabbits were equally allocated into three groups: sham-operated (group sham); bled within 30 minutes to mean arterial pressure (MAP) of 40 mmHg (group shock-40); bled within 30 minutes to MAP of 30 mmHg (group shock-30). Shock was maintained for 60 min. Resuscitation was performed by reinfusing shed blood with two volumes of Ringer's lactate and blood was sampled for estimation of serum levels aminotransferases, creatinine, TNF-alpha, IL-1beta, IL-6, malondialdehyde (MDA) and total antioxidant status (TAS) and for the determination of oxidative burst of polymorhonuclears (PMNs) and mononuclear cells (MCs). RESULTS: Serum AST of group shock-30 was higher than that of group shock-40 at 60 and 120 minutes after start of resuscitation; serum creatinine of group shock-30 was higher than group shock-40 at 120 minutes. Measured cytokines, MDA and cellular oxidative burst of groups, shock-40 and shock-30 were higher than group sham within the first 60 minutes after start of resuscitation. Serum concentrations of IL-1beta, IL-6 and TNF-alpha of group shock-30 were higher than group shock-40 at 120 minutes (p < 0.05). No differences were found between two groups regarding serum MDA and TAS and oxidative burst on PMNs and MCs but both groups were different to group sham. CONCLUSION: The level of hypotension is a major determinant of the severity of hepatic and renal dysfunction and of the inflammatory response arising during post-ischemic hemorrhagic shock resuscitation. These findings deserve further evaluation in the clinical setting.

Efficacy and safety of high-dose ampicillin/sulbactam vs. colistin as monotherapy for the treatment of multidrug resistant Acinetobacter baumannii ventilator-associated pneumonia.

OBJECTIVE: To compare the safety and efficacy of ampicillin/sulbactam (Amp/Sulb) and colistin (COL) in the treatment of multidrug resistant Acinetobacter baumannii ventilator-associated pneumonia (VAP). METHODS: A prospective cohort study in adult critically ill patients with VAP. Patients were randomly assigned to receive Amp/Sulb (9 g every 8h) or COL (3 MIU every 8h) intravenously. Dosage was adjusted according to creatinine clearance. RESULTS: A total of 28 patients were enrolled (15 COL, 13 Amp/Sulb). Resolution of symptoms and signs occurred in 60% (9/15) of the COL group and 61.5% (9/13) of the Amp/Sulb group, improvement in 13.3% (2/15) vs. 15.3% (1/13) and failure in 26.6% (4/15) vs. 23% (3/13), respectively. The difference was not statistically significant. Bacteriologic success was achieved in 66.6% (10/15) vs. 61.5% (8/13) in the COL and Amp/Sulb groups, respectively (p<0.2). Mortality rates (14 days and 28 days) were 15.3% and 30% for the Amp/Sulb and 20% and 33% for the COL group, respectively. Adverse events were 39.6% (including 33% nephrotoxicity) for the COL group and 30.7% (15.3% nephrotoxicity) for the Amp/Sulb group (p=NS). CONCLUSION: Colistin and high-dose ampicillin/sulbactam were comparably safe and effective treatments for critically ill patients with MDR A. baumannii VAP.

The effect of hypoxemic resuscitation from hemorrhagic shock on blood pressure restoration and on oxidative and inflammatory responses.

OBJECTIVE: We investigated whether hypoxemic resuscitation from hemorrhagic shock prevents the late circulatory instability and attenuates the oxidative and inflammatory responses associated with the standard strategy. DESIGN AND SETTING: Prospective, randomized, controlled animal study in an experimental laboratory of a university intensive care unit. SUBJECTS: Thirty-one New Zealand white rabbits weighting 3.1-3.4 kg INTERVENTIONS: Anesthetized animals were subjected to hemorrhagic shock by exsanguinations to a mean arterial pressure of 40 mmHg for 60 min. Resuscitation was performed by reinfusing the shed blood for 30 min under normoxemia (PaO(2) 95-105 mmHg, control group, n=10) or hypoxemia (PaO(2) 35-40 mmHg, hypox-res group, n=10); Ringer's lactate was given from 30 to 60 min to restore arterial pressure within baseline values. A sham group was assigned (n=11). Animals were recorded for 120 min postresuscitation and for further 360 min to assess the early mortality rate. MEASUREMENTS AND RESULTS: Hypoxemic resuscitation compared with normoxemic resuscitation from hemorrhagic shock was associated with (a) a better hemodynamic condition assessed by the gradual restoration of blood pressure, higher urinary output associated with less fluid infusion; (b) lower reactive oxygen species production assessed by the reduced blood geometric mean fluorescence intensity, lower malondialdehyde, and higher ratio of reduced to total glutathione levels; (c) attenuation in the plasma concentrations of IL-1beta, TNF-alpha, and IL-6; and (d) no difference in mortality rate. CONCLUSIONS: Hypoxemic resuscitation from hemorrhagic shock is more efficient than normoxemic in restoring the blood pressure and in attenuating the excessive oxidative and inflammatory responses observed during normoxemic resuscitation.

Grouping of patients with common variable immunodeficiency based on immunoglobulin biosynthesis: comparison with a classification system on CD4-naïve cells.

The present study compared two different systems of classification of patients with common variable immunodeficiency (CVID); one based on in vitro immunoglobulin biosynthesis; and another on CD4-naïve cell counts. Peripheral blood mononuclear cells (PBMCs) were isolated from 35 patients with CVID and 20 healthy controls. They were stimulated for the secretion of IgM and IgG after stimulation with Staphylococcus aureus Cowan I (SAC) upon supplementation of interleukin-2 (IL-2) or with pokeweed mitogen. T cell subsets were estimated by flow cytometry. By the first system, patients were classified into group A (n=18) with secretion of neither IgG nor IgM; into group B (n=12) with detectable IgM but no IgG secretion; and into group C (n=5) with IgM and IgG secretion similar to controls. By the second system, patients were classified into group I (n=12) with less than 109 CD4-naïve cells/mul; into group II (n=12) with CD4-naïve cells within 109-225microl(-1); and into group III (n=11) with more than 225 CD4-naïve cells/mul. All groups I-III were defective for in vitro release of IgG and IgM. The likelihood ratio for splenomegaly in patients with <225 CD4-naïve cells/mul was 5.08 (p: 0.024). CD4-naïve cell counts of patients were positively correlated to serum levels of IgG and IgA of patients. The presented results revealed that the former system described adequately the function of B cells and the latter the clinical status of the patient. Our proposal is that both should be used for the characterization of patients with CVID.

Acute renal dysfunction in liver diseases.

Renal dysfunction is common in liver diseases, either as part of multiorgan involvement in acute illness or secondary to advanced liver disease. The presence of renal impairment in both groups is a poor prognostic indicator. Renal failure is often multifactorial and can present as pre-renal or intrinsic renal dysfunction. Obstructive or post renal dysfunction only rarely complicates liver disease. Hepatorenal syndrome (HRS) is a unique form of renal failure associated with advanced liver disease or cirrhosis, and is characterized by functional renal impairment without significant changes in renal histology. Irrespective of the type of renal failure, renal hypoperfusion is the central pathogenetic mechanism, due either to reduced perfusion pressure or increased renal vascular resistance. Volume expansion, avoidance of precipitating factors and treatment of underlying liver disease constitute the mainstay of therapy to prevent and reverse renal impairment. Splanchnic vasoconstrictor agents, such as terlipressin, along with volume expansion, and early placement of transjugular intrahepatic portosystemic shunt (TIPS) may be effective in improving renal function in HRS. Continuous renal replacement therapy (CRRT) and molecular absorbent recirculating system (MARS) in selected patients may be life saving while awaiting liver transplantation.