Antioxidant and antiprotease status in peripheral blood and BAL fluid after cardiopulmonary bypass

Does heart surgery change the capacity of α1-antitrypsin to inhibit the ATP-induced release of monocytic interleukin-1β? A preliminary study

Heart surgery involving cardiopulmonary bypass induces systemic inflammation that is, at least in part, caused by extracellular ATP originating from damaged cells and by proteases secreted by activated neutrophils. The anti-protease α1-antitrypsin (AAT) forms complexes with several proteases including neutrophil elastase, resulting in a mutual loss of activity. We demonstrated recently that AAT inhibits the ATP-induced release of the pro-inflammatory cytokine interleukin-1β by human monocytes by a mechanism involving activation of metabotropic functions at nicotinic acetylcholine receptors. Interleukin-1β importantly contributes to the pathogenesis of sterile inflammatory response syndrome. Thus, AAT might function as an endogenous safeguard against life-threatening systemic inflammation. In this preliminary study, we test the hypothesis that during cardiopulmonary bypass, AAT is inactivated as an anti- protease and as an inhibitor of ATP-induced interleukin-1β release. AAT was affinity-purified from the blood plasma of patients before, during and after surgery. Lipopolysaccharide-primed human monocytic U937 cells were stimulated with ATP in the presence or absence of patient AAT to test for its inhibitory effect on interleukin-1β release. Anti-protease activity was investigated via complex formation with neutrophil elastase. The capacity of patient AAT to inhibit the ATP-induced release of interleukin-1β might be slightly reduced in response to heart surgery and complex formation of patient AAT with neutrophil elastase was unimpaired. We conclude that surgery involving cardiopulmonary bypass does not markedly reduce the anti-inflammatory and the anti-protease activity of AAT. The question if AAT augmentation therapy during heart surgery is suited to attenuate postoperative inflammation warrants further studies in vivo.

Lung Protection Strategies during Cardiopulmonary Bypass Affect the Composition of Bronchoalveolar Fluid and Lung Tissue in Cardiac Surgery Patients

Pulmonary dysfunction is among the most frequent complications to cardiac surgeries. Exposure of blood to the cardiopulmonary bypass (CPB) circuit with subsequent lung ischemia-reperfusion leads to the production of inflammatory mediators and increases in microvascular permeability. The study aimed to elucidate histological, cellular, and metabolite changes following two lung protective regimens during CPB with Histidine-Tryptophan-Ketoglutarate (HTK) enriched or warm oxygenated blood pulmonary perfusion compared to standard regimen with no pulmonary perfusion. A total of 90 patients undergoing CPB were randomized to receiving HTK, oxygenated blood or standard regimen. Of these, bronchoalveolar lavage fluid (BALF) and lung tissue biopsies were obtained before and after CPB from 47 and 25 patients, respectively. Histopathological scores, BALF cell counts and metabolite screening were assessed. Multivariate and univariate analyses were performed. Profound histological, cellular, and metabolic changes were identified in all patients after CPB. Histological and cellular changes were similar in the three groups; however, some metabolite profiles were different in the HTK patients. While all patients presented an increase in inflammatory cells, metabolic acidosis, protease activity and oxidative stress, HTK patients seemed to be protected against severe acidosis, excessive fatty acid oxidation, and inflammation during ischemia-reperfusion. Additional studies are needed to confirm these findings.

Short-term one-lung ventilation does not influence local inflammatory cytokine response after lung resection

Background

One-lung ventilation (OLV) is a ventilation procedure used for pulmonary resection which may results in lung injury. The aim of this study was to evaluate the local inflammatory cytokine response from the dependent lung after OLV and its correlation to VT. The secondary aim was to evaluate the clinical outcome of each patient.

Methods

Twenty-eight consecutive patients were enrolled. Ventilation was delivered in volume-controlled mode with a VT based on predicted body weight (PBW). 5 cmH₂O positive end-expiratory pressure (PEEP) and FiO₂ 0.5 were applied. Bronchoalveolar lavage (BAL) was performed in the dependent lung before and after OLV. The levels of pro-inflammatory interleukins (IL-1α, IL-1β, IL-6, IL-8), tumor necrosis factor alpha (TNFα), vascular endothelial growth factor (VEGF), endothelial growth factor (EGF), monocyte chemoattractant protein-1 (MCP-1) and anti-inflammatory cytokines, such as interleukins (IL-2, IL-4, IL-10) and interferon (IFN-γ), were evaluated. Subgroup analysis: to analyze the VT setting during OLV, all patients were ventilated within a range of 5-10 mL/kg. Thirteen patients, classified as a conventional ventilation (CV) subgroup, received 8-10 mL/kg, while 15 patients, classified as a protective ventilation (PV) subgroup, received 5-7 mL/kg.

Results

Cytokine BAL levels after surgery showed no significant increase after OLV, and no significant differences were recorded between the two subgroups. The mean duration of OLV was 64.44±21.68 minutes. No postoperative respiratory complications were recorded. The mean length of stay was for 4.00±1.41 days in the PV subgroup and 4.45±2.07 days in the CV group; no statistically significant differences were recorded between the two subgroups (P=0.511).

Conclusions

Localized inflammatory cytokine response after OLV was not influenced by the use of different VT. Potentially, the application of PEEP in both ventilation strategies and the short duration of OLV could prevent postoperative complications.

The importance of intraoperative selenium blood levels on organ dysfunction in patients undergoing off-pump cardiac surgery: a randomised controlled trial

INTRODUCTION

Cardiac surgery is accompanied by an increase of oxidative stress, a significantly reduced antioxidant (AOX) capacity, postoperative inflammation, all of which may promote the development of organ dysfunction and an increase in mortality. Selenium is an essential co-factor of various antioxidant enzymes. We hypothesized a less pronounced decrease of circulating selenium levels in patients undergoing off-pump coronary artery bypass (OPCAB) surgery due to less intraoperative oxidative stress.

METHODS

In this prospective randomised, interventional trial, 40 patients scheduled for elective coronary artery bypass grafting were randomly assigned to undergo either on-pump or OPCAB-surgery, if both techniques were feasible for the single patient. Clinical data, myocardial damage assessed by myocard specific creatine kinase isoenzyme (CK-MB), circulating whole blood levels of selenium, oxidative stress assessed by asymmetric dimethylarginine (ADMA) levels, antioxidant capacity determined by glutathionperoxidase (GPx) levels and perioperative inflammation represented by interleukin-6 (IL-6) levels were measured at predefined perioperative time points.

RESULTS

At end of surgery, both groups showed a comparable decrease of circulating selenium concentrations. Likewise, levels of oxidative stress and IL-6 were comparable in both groups. Selenium levels correlated with antioxidant capacity (GPx: r = 0.720; p<0.001) and showed a negative correlation to myocardial damage (CK-MB: r =  -0.571, p<0.001). Low postoperative selenium levels had a high predictive value for the occurrence of any postoperative complication.

CONCLUSIONS

OPCAB surgery is not associated with less oxidative stress and a better preservation of the circulating selenium pool than on-pump surgery. Low postoperative selenium levels are predictive for the development of complications.

TRIAL REGISTRATION

ClinicalTrials.gov NCT01409057.

Off-pump coronary revascularization: A potential benefit for female patients?

Coronary artery disease is one of the leading causes of illness for both men and women. However, women are 3 times more likely to die for coronary artery disease as they are of breast cancer. There are an increasing prevalence of coronary artery disease in women and thus facing the need for surgical revascularization. It has long being accepted that women carry a high risk of coronary surgery than men. Many investigators have suggested that female itself is predictive of poor outcome after on pump coronary surgery. We thought to search the litlature to investigate whether women who undergo off-pump surgery receive any benefits compared with women undergoing on-pump surgery.

Immunomodulatory Effects of Anesthetics during Thoracic Surgery

Background. One-lung ventilation (OLV) during thoracic surgery may induce alveolar cell damage and release of proinflammatory mediators. The current trial was planned to evaluate effect of propofol versus isoflurane anesthesia on alveolar and systemic immune modulation during thoracic surgery. Methods. Fifty adult patients undergoing open thoracic surgery were randomly assigned to receive propofol (n = 25) or isoflurane (n = 25) anesthesia. The primary outcome measures included alveolar and plasma concentrations of interleukin-8(IL-8) and tumour necrosis factor-α (TNF-α), whereas secondary outcome measures were alveolar and plasma concentrations of malondialdehyde (MDA), superoxide dismutase (SOD), and changes in alveolar albumin concentrations and cell numbers. Results. Alveolar and plasma concentrations of IL-8 and TNF-α were significantly lower in the isoflurane group, whereas alveolar and plasma concentrations of MDA were significantly lower in the propofol group. Alveolar and plasma SOD levels increased significantly in the propofol group whereas they showed no significant change in the isoflurane group. Furthermore, the isoflurane group patients developed significantly lower alveolar albumin concentrations and cell numbers. Conclusion. Isoflurane decreased the inflammatory response associated with OLV during thoracic surgery and may be preferable over propofol in patients with expected high levels of proinflammatory cytokines like cancer patients.

EFFECTS OFN-ACETYLCYSTEINE ON OXIDANT-ANTIOXIDANT BALANCE IN OLEIC ACID–INDUCED LUNG INJURY

The antioxidant and anti-inflammatory properties of N-acetylcysteine has been documented in many experimental lung injury models. Because intravenous injection of oleic acid induces histopathologic changes similar to those seen in human acute lung injury or acute respiratory distress syndrome, the authors evaluated the effects of N-acetylcysteine (NAC) on oxidative stress and lung damage in an oleic acid (OA)-induced lung injury model. Thirty-five rats were divided into 5 groups as sham, NAC, OA, pre-OA-NAC, and post-OA-NAC. Lung damage was induced by intravenous administration of oleic acid. Pre-OA-NACgroup received intravenous (IV) N-acetylcysteine 15 minutes before oleic acid infusion and post-OA-NAC group received IV N-acetylcysteine 2 hours after oleic acid infusion. In both of the N-acetylcysteine treatment groups, blood and tissue samples were collected 4 hours after oleic acid infusion, independent from the time of N-acetylcysteine infusion. In other groups, blood and tissue samples were collected 4 hours after ethanol, NAC, or OA infusions. Serum myeloperoxidase activity, total antioxidant capacity, malondialdehyde levels, and lung tissue Na+ - K+ ATPase activity were measured and light microscopic analyses of lung specimens were performed. The administration of N-acetylcysteine significantly restored Na+ - K+ ATPase activity and total antioxidant capacity levels and ameliorated lung architecture. N-acetylcysteine has been shown to have some attenuating effects in experimental animal studies. However, further investigations are necessary to suggest N-acetylcysteine as a treatment agent in critically ill patients with lung injury.

Acid-base effects of a bicarbonate-balanced priming fluid during cardiopulmonary bypass: comparison with Plasma-Lyte 148. A randomised single-blinded study

Fluid-induced metabolic acidosis can be harmful and can complicate cardiopulmonary bypass. In an attempt to prevent this disturbance, we designed a bicarbonate-based crystalloid circuit prime balanced on physico-chemical principles with a strong ion difference of 24 mEq/l and compared its acid-base effects with those of Plasma-Lyte 148, a multiple electrolyte replacement solution containing acetate plus gluconate totalling 50 mEq/l. Twenty patients with normal acid-base status undergoing elective cardiac surgery were randomised 1:1 to a 2 litre prime of either bicarbonate-balanced fluid or Plasma-Lyte 148. With the trial fluid, metabolic acid-base status was normal following bypass initiation (standard base excess 0.1 (1.3) mEq/l, mean, SD), whereas Plasma-Lyte 148 produced a slight metabolic acidosis (standard base excess -2.2 (2.1) mEq/l). Estimated group difference after baseline adjustment was 3.6 mEq/l (95% confidence interval 2.1 to 5.1 mEq/l, P=0.0001). By late bypass, mean standard base excess in both groups was normal (0.8 (2.2) mEq/l vs. -0.8 (1.3) mEq/l, P=0.5). Strong ion gap values were unaltered with the trial fluid, but with Plasma-Lyte 148 increased significantly on bypass initiation (15.2 (2.5) mEq/l vs. 2.5 (1.5) mEq/l, P < 0.0001), remaining elevated in late bypass (8.4 (3.4) mEq/l vs. 5.8 (2.4) mEq/l, P < 0.05). We conclude that a bicarbonate-based crystalloid with a strong ion difference of 24 mEq/l is balanced for cardiopulmonary bypass in patients with normal acid-base status, whereas Plasma-Lyte 148 triggers a surge of unmeasured anions, persisting throughout bypass. These are likely to be gluconate and/or acetate. Whether surges of exogenous anions during bypass can be harmful requires further study.

Pulmonary function and inflammatory markers in patients undergoing coronary revascularisation with or without cardiopulmonary bypass

Lung injury after cardiac surgery is believed to result from cardiopulmonary bypass and its pro-inflammatory effects. To test this hypothesis, we compared the oxygenation ratios, extravascular lung water indices and systemic and pulmonary tumour necrosis factor alpha (TNF-alpha) and interleukin (IL)-8 at predetermined intervals in coronary artery surgery patients with or without cardiopulmonary bypass. No differences in oxygenation ratios or extravascular lung water indices were found. Serum values of TNF-alpha and IL-8 increased in both groups but were higher in the cardiopulmonary bypass group (end of surgery: mean (SD) TNF-alpha 3.68 (2.5) vs 2.20 (1.2) pg.ml(-1) (p = 0.043 (CI 0.05-2.9)) and mean (SD) IL-8 19.45 (10.8) vs 6.31 (5.3) pg.ml(-1) (p = 0.001 (CI 6.9-19.3)). In broncho-alveolar lavage fluid, TNF-alpha and IL-8 increased in both groups with no differences between the groups.

The role of oxidative stress in postoperative delirium

AIM

This study aimed to determine a marker that predicts delirium using preoperative oxidative processes in patients undergoing cardiopulmonary bypass surgery.

METHOD

Twelve of the 50 patients included in the study showed signs of delirium during postoperative follow-up. The Delirium Rating Scale was used in patients with delirium according to DSM-IV-TR in the postoperative period. Venous blood samples were obtained from the patients the day before and the day after the surgery to determine plasma antioxidant enzyme levels.

RESULTS

While there were no differences in preoperative superoxide dismutase (SOD), glutathione peroxidase (GSH-Px) and malondialdehyde (MDA) levels in both groups, catalase (CAT) levels were significantly lower in the delirium group. Postoperative SOD and MDA levels were also higher in the delirium group, while the GSH-Px levels were found to be lower when compared with those during the preoperative period. In the nondelirium group, the postoperative MDA and GSH-Px levels were found to be lower than preoperative levels, and postoperative SOD levels were found to be higher than preoperative levels. CAT levels were lower in the delirium group when the pre- and postoperative levels were compared in both groups. The postoperative levels of SOD, GSH-Px and CAT in the nondelirium group and MDA in the delirium group were significantly higher than preoperative levels.

CONCLUSION

Patients with low preoperative CAT levels appeared to be more susceptible to delirium than patients with higher CAT levels.

Effects of ulinastatin treatment on the cardiopulmonary bypass-induced hemodynamic instability and pulmonary dysfunction

OBJECTIVE

To examine the association between decreased release of proinflammatory cytokines in response to urinary trypsin inhibitor pretreatment and decreased myocardial and lung injury after cardiopulmonary bypass.

DESIGN

A prospective, randomized, double-blind study.

SETTING

University hospital.

SUBJECTS

Thirty patients on cardiopulmonary bypass undergoing coronary artery bypass grafting.

INTERVENTIONS

Patients received 5000 units/kg intravenous urinary trypsin inhibitor (n = 15) or 0.9% saline (control, n = 15) immediately before aortic cannulation for cardiopulmonary bypass.

MEASUREMENT AND MAIN RESULTS

Neutrophil elastase, tumor necrosis factor-alpha, interleukin-6, and interleukin-8 were measured after intubation (T1), immediately before aortic cannulation (T2), after separation from cardiopulmonary bypass (T3), at the end of surgery (T4), and on postoperative days 1 (T5), 3 (T6), and 5 (T7). Simultaneous hematocrit values were obtained at all sample times. Isoenzyme of creatine kinase with muscle and brain subunits, troponin-T, and myosin light chain I were also measured. Various hemodynamic and pulmonary data were obtained perioperatively. Levels of neutrophil elastase and cytokines were corrected for hemodilution. Interleukin-6 and interleukin-8 levels were lower at T3 and T4 in the urinary trypsin inhibitor group than in the control group. Stroke volume index was significantly decreased in the control group at T3, and statistical difference was found between groups at T3 (p < .01). Respiratory index and intrapulmonary shunt were significantly higher in the control group than in the urinary trypsin inhibitor group at T3. Changes in respiratory index and intrapulmonary shunt correlated with interleukin-8 levels at T3 (r = .52, p < 00001; r = .37, p < 0001, respectively) and T4 (r = .44, p < .001; r = .24, p < .05, respectively). Neutrophil elastase levels and cardiac marker responses to coronary artery bypass grafting surgery were similar in both groups.

CONCLUSIONS

Prepump administration of urinary trypsin inhibitor attenuates the elevation of interleukin-6 and interleukin-8 release immediately after cardiopulmonary bypass.

Inhibition of neutrophil elastase by alpha1-protease inhibitor at the surface of human polymorphonuclear neutrophils

The uncontrolled proteolytic activity in lung secretions during lung inflammatory diseases might be due to the resistance of membrane-bound proteases to inhibition. We have used a new fluorogenic neutrophil elastase substrate to measure the activity of free and membrane-bound human neutrophil elastase (HNE) in the presence of alpha1-protease inhibitor (alpha1-Pi), the main physiological inhibitor of neutrophil serine proteases in lung secretions. Fixed and unfixed neutrophils bore the same amounts of active HNE at their surface. However, the HNE bound to the surface of unfixed neutrophils was fully inhibited by stoichiometric amounts of alpha1-Pi, unlike that of fixed neutrophils. The rate of inhibition of HNE bound to the surface of unfixed neutrophils was the same as that of free HNE. In the presence of alpha1-Pi, membrane-bound elastase is almost entirely removed from the unfixed neutrophil membrane to form soluble irreversible complexes. This was confirmed by flow cytometry using an anti-HNE mAb. HNE activity rapidly reappeared at the surface of HNE-depleted cells when they were triggered with the calcium ionophore A23187, and this activity was fully inhibited by stoichiometric amounts of alpha1-Pi. HNE was not released from the cell surface by oxidized, inactive alpha1-Pi, showing that active inhibitor is required to interact with active protease from the cell surface. We conclude that HNE activity at the surface of human neutrophils is fully controlled by alpha1-Pi when the cells are in suspension. Pericellular proteolysis could be limited to zones of contact between neutrophils and subjacent protease substrates where natural inhibitors cannot penetrate.

The Pulmonary Immune Effects of Mechanical Ventilation in Patients Undergoing Thoracic Surgery

Mechanical ventilation (MV) may induce an inflammatory alveolar response. One-lung ventilation (OLV) with tidal volumes (Vt) as used during two-lung ventilation is a suggested algorithm but may impose mechanical stress of the dependent lung and potentially aggravate alveolar mediator release. We studied whether ventilation with different Vt modifies pulmonary immune function, hemodynamics, and gas exchange. Thirty-two patients undergoing open thoracic surgery were randomized to receive either MV with Vt = 10 mL/kg (n = 16) or Vt = 5 mL/kg (n = 16) adjusted to normal Pa(CO2) during and after OLV. Fiberoptic bronchoalveolar lavage of the ventilated lung was performed, and cells, protein, tumor necrosis factor (TNF)-alpha, interleukin (IL)-8, soluble intercellular adhesion molecule (sICAM)-1, IL-10, and elastase were determined in the bronchoalveolar lavage. Data were analyzed by parametric or nonparametric tests, as indicated. In all patients, an increase of proinflammatory variables was found. The time courses of intra-alveolar cells, protein, albumin, IL-8, elastase, and IL-10 did not differ between the groups after OLV and postoperatively. TNF-alpha (8.4 versus 5.0 microg/mL) and sICAM-1 (52.7 versus 27.5 microg/mL) concentrations were significantly smaller after OLV with Vt = 5 mL/kg. These results indicate that MV may induce epithelial damage and a proinflammatory response in the ventilated lung. Reduction of tidal volume during OLV may reduce alveolar concentrations of TNF-alpha and of sICAM-1.

IMPLICATIONS

Reductions of tidal volume, with subsequently decreased peak airway pressures, may reduce some alveolar inflammatory responses seen with mechanical ventilation.

Competition between elastase and related proteases from human neutrophil for binding to alpha1-protease inhibitor

The protease-antiprotease imbalance that is characteristic of most inflammatory lung disorders depends on the spatial-temporal regulation of active inhibitor and protease concentrations in lung secretions. We have studied the competition between the three main serine proteases from human neutrophil primary granules in their binding to alpha1-Pi, the main serine proteases inhibitor in lung secretions. Elastase was the only target of alpha1-Pi when identical molar amounts of purified inhibitor and the three proteases were tested together. The other two proteases were only inhibited once elastase was saturated. Elastase remained the preferred target of inhibitors when bronchoalveolar lavage fluids from patients with lung pneumonia and acute respiratory distress syndrome were used as the source of inhibitors, in spite of the presence of additional inhibitors in lung secretions. Since neutrophil proteases are expressed at the neutrophil surface, we also measured residual activities of membrane-bound proteases after purified neutrophils were incubated with bronchoalveolar fluids. Again, elastase was the preferred target of the inhibitors. We conclude that protease 3 and cathepsin G are not controlled as efficiently as elastase in lung secretions, a feature that must be taken into account when developing inhibitor-based anti-inflammatory therapies.

Pulmonary Outcomes of Off-Pump vs On-Pump Coronary Artery Bypass Surgery in a Randomized Trial

STUDY OBJECTIVES

Comparison of pulmonary outcomes after off-pump coronary artery bypass (OPCAB) vs on-pump coronary artery grafting with cardiopulmonary bypass (CABG/CPB).

STUDY DESIGN

We examined preoperative and postoperative respiratory compliance, fluid balance, hemodynamics, arterial blood gases, chest radiographs, spirometry, pulmonary complications, and time to extubation in a prospective trial of 200 patients randomized to OPCAB vs CABG/CPB performed by one surgeon.

RESULTS

One CABG/CPB patient and two OPCAB patients required mitral valve repair or replacement and were withdrawn. After three crossovers from CABG/CBP to OPCAB and one crossover from OPCAB to CABG, 97 CABG/CPB patients and 100 OPCAB patients remained. There were no significant preoperative demographic differences between groups. Postoperative compliance was reduced more after OPCAB than after CABG/CPB (- 15.4 +/- 10.7 mL/cm H(2)O vs - 11.2 +/- 10.1 mL/cm H(2)O [mean +/- SD]; p = 0.007), associated with rotation of the heart into the right chest to perform posterolateral bypasses (p < 0.001) and the concomitant increased fluid requirements necessary to maintain hemodynamic stability during rotation of the heart. In addition to higher intraoperative fluid intake (4,541 +/- 1,311 mL vs 3,585 +/- 1,033 mL, p < 0.0001), OPCAB patients had higher intraoperative fluid balance (3,903 +/- 1,315 mL vs 1,772 +/- 1,373 mL, p < 0.0001), and higher postoperative pulmonary arterial diastolic pressure (15.0 +/- 5.5 mm Hg vs 11.8 +/- 5.2 mm Hg, p < 0.0001) and central venous pressure (10.4 +/- 4.5 mm Hg vs 8.4 +/- 4.7 mm Hg, p < 0.0001). Despite lower compliance, immediate postoperative Pao(2) on fraction of inspired oxygen of 1.0 (275 +/- 97 torr vs 221 +/- 92 torr, p = 0.001) was higher after OPCAB and extubation was earlier (p = 0.001). Postoperative chest radiographs, spirometry, mortality, reintubation, or readmission for pulmonary complications were not different between groups.

CONCLUSIONS

Compared to CABG/CPB, OPCAB was associated with a greater reduction in postoperative respiratory compliance associated with increased fluid administration and rotation of the heart into the right chest to perform posterolateral grafts. OPCAB yielded better gas exchange and earlier extubation but no difference in chest radiographs, spirometry, or rates of death, pneumonia, pleural effusion, or pulmonary edema.

Lymphocyte’s Activation and Apoptosis After Coronary Artery Bypass Graft: A Comparative Study of Two Membrane Oxygenators–One with and Another without a Venous-Arterial Shunt

Newer oxygenators with the latest technologies are designed to attenuate the immune response, including lymphopenia, prompted by cardiopulmonary bypass (CPB) in cardiac surgery. We evaluated the effect of CPB, comparing an oxygenator with a venous-arterial shunt and a conventional oxygenator with regard to lymphocyte's early activation and apoptosis induction and its implications in post-CPB lymphopenia. Patients undergoing coronary artery bypass graft surgery with CPB, using either a conventional oxygenator or one with a venous-arterial shunt, had blood samples drawn at anesthetic induction (baseline); the beginning and end of the CPB; and at 6, 12, and 24 hours after surgery. Analysis by flow cytometry was undertaken to assess the expression of lymphocyte surface markers (CD3+, CD25+, CD26+, CD69+) and apoptosis (annexin V). Twenty patients were studied; 10 used a conventional oxygenator, and 10 used an oxygenator with venous-arterial shunt. Postoperative lymphopenia (50% decrease), 35% increased expression of CD69+, and 56% decrease in annexin V were significant comparing baseline to 24 hour value, similarly in both groups. Early activation (expression of CD69+) and degree of apoptosis (expression of annexin V) of lymphocytes after CBP in cardiac surgery was similarly observed in both types of oxygenators. The observed lymphopenia after CPB does not appear to be secondary to apoptosis.

Assessing the antioxidative status in critically ill patients

PURPOSE OF REVIEW

Oxidative stress is caused by a higher production of reactive oxygen and reactive nitrogen species or a decrease in endogenous protective antioxidative capacity. In all types of critical illness, such as sepsis, trauma, burn injury, acute pancreatitis, liver injury, severe diabetes, acute respiratory distress syndrome, AIDS and kidney failure, the occurrence of increased oxidative stress or a reduced antioxidative status is described. Whereas in the past, reactive oxygen and reactive nitrogen species were mainly known as harmful agents, recent investigations have given a new insight into the (patho)physiological importance of these substances as powerful messenger molecules involved in gene regulation, thereby enabling the synthesis of cytokines or adhesion molecules necessary for defending inflammatory processes. As shown in this review, there are numerous possibilities for the quantification of oxidative stress.

RECENT FINDINGS

Several investigations showed a close association of single or multiple parameters, such as total antioxidative capacity, lipid peroxidation, vitamins C and E, the activation of nuclear factor kappa B, and respiratory burst, with the patient's outcome. However, no recommendation for a single parameter to be measured can be given because the assays described do not allow the definition of an overall "antioxidative status" for patients.

SUMMARY

The occurrence of oxidative stress in critically ill patients is associated with a poor prognosis. The measurement of a cluster of assays representative of the quantification of reactive species or of antioxidants may improve the usefulness of therapeutic intervention and increase knowledge of pathophysiological alterations.