Lung protection during total cardiopulmonary bypass by isolated lung perfusion: preliminary results of a novel perfusion strategy

The effects of ischaemic conditioning on lung ischaemia-reperfusion injury

Ischaemia-reperfusion injury (IRI) encompasses the deleterious effects on cellular function and survival that result from the restoration of organ perfusion. Despite their unique tolerance to ischaemia and hypoxia, afforded by their dual (pulmonary and bronchial) circulation as well as direct oxygen diffusion from the airways, lungs are particularly susceptible to IRI (LIRI). LIRI may be observed in a variety of clinical settings, including lung transplantation, lung resections, cardiopulmonary bypass during cardiac surgery, aortic cross-clamping for abdominal aortic aneurysm repair, as well as tourniquet application for orthopaedic operations. It is a diagnosis of exclusion, manifesting clinically as acute lung injury (ALI) or acute respiratory distress syndrome (ARDS). Ischaemic conditioning (IC) signifies the original paradigm of treating IRI. It entails the application of short, non-lethal ischemia and reperfusion manoeuvres to an organ, tissue, or arterial territory, which activates mechanisms that reduce IRI. Interestingly, there is accumulating experimental and preliminary clinical evidence that IC may ameliorate LIRI in various pathophysiological contexts. Considering the detrimental effects of LIRI, ranging from ALI following lung resections to primary graft dysfunction (PGD) after lung transplantation, the association of these entities with adverse outcomes, as well as the paucity of protective or therapeutic interventions, IC holds promise as a safe and effective strategy to protect the lung. This article aims to provide a narrative review of the existing experimental and clinical evidence regarding the effects of IC on LIRI and prompt further investigation to refine its clinical application.

Effects of pulmonary perfusion during cardiopulmonary bypass on lung functions after cardiac operation

BACKGROUND

Pulmonary artery perfusion during cardiopulmonary bypass (CPB) is a known but rarely used technique in adult cardiac surgery. In this study, we aimed to investigate biochemical and histopathological effects of pulmonary artery perfusion during CPB on lung functions.

METHODS

Between May 2014 and August 2014, all patients (n = 24) who gave informed consent for participating this study with inclusion criteria were included. Patients undergoing isolated coronary artery bypass grafting were sequentially randomized to conventional CPB (control group, n = 12) and conventional CPB with selective pulmonary artery perfusion (study group, n = 12). Lung functions were monitored using PF ratio, alveolar-arterial oxygen gradient, and lactate levels. A small sample tissue from the left lung was excised for histopathologic examination. Immunocytochemistry analysis was performed using anti-rabbit polyclonal vascular endothelial growth factor (VEGF), rabbit polyclonal inducible nitric oxide synthase (i-NOS), and BCL-2 antibodies.

RESULTS

Postoperative course of the patients were uneventful without any clinical outcome differences in terms of cardiopulmonary complications, ventilation time and hospital stay. Pulmonary perfusion group had significantly better oxygenation values after extubation and at postoperative 24-hour. Electron microscopy examinations revealed better preservation of the alveolar wall integrity with pulmonary perfusion. The intensity of VEGF, i-NOS, and BCL-2 antibody expressions in bronchial epithelial cells were more prominent in the pulmonary perfusion group.

CONCLUSIONS

Pulmonary artery perfusion during aortic cross-clamping provides better oxygenation and preservation of the wall alveolar integrity after coronary artery bypass grafting surgery. This technique can be used as a protective strategy to minimize CPB-induced lung injury in adult cardiac surgery.

Extracorporeal life support and systemic inflammation

Extracorporeal life support (ECLS) encompasses a wide range of extracorporeal modalities that offer short- and intermediate-term mechanical support to the failing heart or lung. Apart from the daily use of cardiopulmonary bypass (CPB) in the operating room, there has been a resurgence of interest and utilization of veno-arterial and veno-venous extracorporeal membrane oxygenation (VA- and VV-ECMO, respectively) and extracorporeal carbon dioxide removal (ECCO₂R) in recent years. This might be attributed to the advancement in technology, nonetheless the morbidity and mortality associated with the clinical application of this technology is still significant. The initiation of ECLS triggers a systemic inflammatory response, which involves the activation of the coagulation cascade, complement systems, endothelial cells, leukocytes, and platelets, thus potentially contributing to morbidity and mortality. This is due to the release of cytokines and other biomarkers of inflammation, which have been associated with multiorgan dysfunction. On the other hand, ECLS can be utilized as a therapy to halt the inflammatory response associated with critical illness and ICU therapeutic intervention, such as facilitating ultra-protective mechanical ventilation. In addition to addressing the impact on outcome of the relationship between inflammation and ECLS, two different but complementary pathophysiological perspectives will be developed in this review: ECLS as the cause of inflammation and ECLS as the treatment of inflammation. This framework may be useful in guiding the development of novel therapeutic strategies to improve the outcome of critical illness.

Lung Protection Strategies during Cardiopulmonary Bypass Affect the Composition of Blood Electrolytes and Metabolites-A Randomized Controlled Trial

Cardiac surgery with cardiopulmonary bypass (CPB) causes an acute lung ischemia-reperfusion injury, which can develop to pulmonary dysfunction postoperatively. This sub-study of the Pulmonary Protection Trial aimed to elucidate changes in arterial blood gas analyses, inflammatory protein interleukin-6, and metabolites of 90 chronic obstructive pulmonary disease patients following two lung protective regimens of pulmonary artery perfusion with either hypothermic histidine-tryptophan-ketoglutarate (HTK) solution or normothermic oxygenated blood during CPB, compared to the standard CPB with no pulmonary perfusion. Blood was collected at six time points before, during, and up to 20 h post-CPB. Blood gas analysis, enzyme-linked immunosorbent assay, and nuclear magnetic resonance spectroscopy were used, and multivariate and univariate statistical analyses were performed. All patients had decreased gas exchange, augmented inflammation, and metabolite alteration during and after CPB. While no difference was observed between patients receiving oxygenated blood and standard CPB, patients receiving HTK solution had an excess of metabolites involved in energy production and detoxification of reactive oxygen species. Also, patients receiving HTK suffered a transient isotonic hyponatremia that resolved within 20 h post-CPB. Additional studies are needed to further elucidate how to diminish lung ischemia-reperfusion injury during CPB, and thereby, reduce the risk of developing severe postoperative pulmonary dysfunction.

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.

Pulmonary artery perfusion versus no perfusion during cardiopulmonary bypass for open heart surgery in adults

BACKGROUND

Available evidence has been inconclusive on whether pulmonary artery perfusion during cardiopulmonary bypass (CPB) is associated with decreased or increased mortality, pulmonary events, and serious adverse events (SAEs) after open heart surgery. To our knowledge, no previous systematic reviews have included meta-analyses of these interventions.

OBJECTIVES

To assess the benefits and harms of single-shot or continuous pulmonary artery perfusion with blood (oxygenated or deoxygenated) or a preservation solution compared with no perfusion during cardiopulmonary bypass (CPB) in terms of mortality, pulmonary events, serious adverse events (SAEs), and increased inflammatory markers for adult surgical patients.

SEARCH METHODS

We searched the Cochrane Central Register of Controlled Trials (CENTRAL), MEDLINE, Embase, Science Citation Index Expanded, and advanced Google for relevant studies. We handsearched retrieved study reports and scanned citations of included studies and relevant reviews to ensure that no relevant trials were missed. We searched for ongoing trials and unpublished trials in the World Health Organization International Clinical Trials Registry Platform (ICTRP) and at clinicaltrials.gov (4 July 2017). We contacted medicinal firms producing preservation solutions to retrieve additional studies conducted to examine relevant interventions.

SELECTION CRITERIA

We included randomized controlled trials (RCTs) that compared pulmonary artery perfusion versus no perfusion during CPB in adult patients (≧ 18 years).

DATA COLLECTION AND ANALYSIS

Two independent review authors extracted data, conducted fixed-effect and random-effects meta-analyses, and calculated risk ratios (RRs) or odds ratios (ORs) for dichotomous outcomes. For continuous data, we have presented mean differences (MDs) and 95% confidence intervals (CIs) as estimates of the intervention effect. To minimize the risk of systematic error, we assessed risk of bias of included trials. To reduce the risk of random errors caused by sparse data and repetitive updating of cumulative meta-analyses, we applied Trial Sequential Analyses (TSAs). We used GRADE principles to assess the quality of evidence.

MAIN RESULTS

We included in this review four RCTs (210 participants) reporting relevant outcomes. Investigators randomly assigned participants to pulmonary artery perfusion with blood versus no perfusion during CPB. Only one trial included the pulmonary artery perfusion intervention with a preservation solution; therefore we did not perform meta-analysis. Likewise, only one trial reported patient-specific data for the outcome "pulmonary events"; therefore we have provided no results from meta-analysis. Instead, review authors added two explorative secondary outcomes for this version of the review: the ratio of partial pressure of oxygen in arterial blood (PaO₂) to fraction of inspired oxygen (FiO₂); and intubation time. Last, review authors found no comparable data for the secondary outcome inflammatory markers.The effect of pulmonary artery perfusion on all-cause mortality was uncertain (Peto OR 1.78, 95% CI 0.43 to 7.40; TSA adjusted CI 0.01 to 493; 4 studies, 210 participants; GRADE: very low quality). Sensitivity analysis of one trial with overall low risk of bias (except for blinding of personnel during the surgical procedure) yielded no evidence of a difference for mortality (Peto OR 1.65, 95% CI 0.27 to 10.15; 1 study, 60 participants). The TSA calculated required information size was not reached and the futility boundaries did not cross; thus this analysis cannot refute a 100% increase in mortality.The effect of pulmonary artery perfusion with blood on SAEs was likewise uncertain (RR 1.12, 95% CI 0.66 to 1.89; 3 studies, 180 participants; GRADE: very low quality). Data show an association between pulmonary artery perfusion with blood during CPB and a higher postoperative PaO₂/FiO₂ ratio (MD 27.80, 95% CI 5.67 to 49.93; 3 studies, 119 participants; TSA adjusted CI 5.67 to 49.93; GRADE: very low quality), although TSA could not confirm or refute a 10% increase in the PaO₂/FiO₂ ratio, as the required information size was not reached.

AUTHORS' CONCLUSIONS

The effects of pulmonary artery perfusion with blood during cardiopulmonary bypass (CPB) are uncertain owing to the small numbers of participants included in meta-analyses. Risks of death and serious adverse events may be higher with pulmonary artery perfusion with blood during CPB, and robust evidence for any beneficial effects is lacking. Future randomized controlled trials (RCTs) should provide long-term follow-up and patient stratification by preoperative lung function and other documented risk factors for mortality. One study that is awaiting classification (epub abstract with preliminary results) may change the results of this review when full study details have been published.

Lung Injury after Cardiopulmonary Bypass

Pulmonary injury during cardiopulmonary bypass is common as patient factors (smoking, pain, pneumonia) and the effects of cardiopulmonary bypass combine to compromise lung function after cardiac surgery. Lung injury follows the propagation of an inflammatory response involving cytokines, complement, neutrophils, monocytes, activated endothelial cells and platelets. Neutrophils sequester in the lung in response to chemo-tactic agents and release injurious oxygen free radicals and specific enzymes resulting in widespread pulmonary injury.

To alleviate this lung injury a number of possible interventions exist. Off pump surgery may reduce the degree of systemic inflammation but respiratory impairment still occurs and the clinical advantage is uncertain. The use of leukocyte filtration can attenuate the acute inflammatory response with encouraging though variable results. Aprotinin, Pentoxyfilline, Nitric oxide, Aspirin and other agents have shown benefits in lung function after cardiopulmonary bypass induced lung injury.

Given the magnitude and diversity of the inflammatory response to cardiopulmonary bypass many possible interventions exist to attenuate lung injury resulting from extracorporeal circulation. Immediate clinical benefits are likely to result from successful amelioration of the processes involved.

Pulmonary complications of cardiopulmonary bypass

Pulmonary complications after the use of extracorporeal circulation are common, and they range from transient hypoxemia with altered gas exchange to acute respiratory distress syndrome (ARDS), with variable severity. Similar to other end-organ dysfunction after cardiac surgery with extracorporeal circulation, pulmonary complications are attributed to the inflammatory response, ischemia-reperfusion injury, and reactive oxygen species liberated as a result of cardiopulmonary bypass. Several factors common in cardiac surgery with extracorporeal circulation may worsen the risk of pulmonary complications including atelectasis, transfusion requirement, older age, heart failure, emergency surgery, and prolonged duration of bypass. There is no magic bullet to prevent or treat pulmonary complications, but supportive care with protective ventilation is important. Targets for the prevention of pulmonary complications include mechanical, surgical, and anesthetic interventions that aim to reduce the contact activation, systemic inflammatory response, leukocyte sequestration, and hemodilution associated with extracorporeal circulation.

Pressure-controlled mechanical ventilation is more advantageous in the follow-up of patients with chronic obstructive pulmonary disease after open heart surgery

OBJECTIVE

Cardiopulmonary bypass deteriorates pulmonary functions to a certain extent. Patients with chronic obstructive pulmonary disease (COPD) are associated with increased mortality and morbidity risks in the postoperative period of open-heart surgery. In this study we compared 2 different mechanical ventilation modes, pressure-controlled ventilation (PCV) and volume-controlled ventilation (VCV), in this particular patient population.

PATIENTS AND METHODS

Forty patients with severe COPD were assigned to 1 of 2 groups and enrolled to receive PCV or VCV in the postoperative period. Arterial blood gases, respiratory parameters, and intensive care unit and hospital stays were compared between the 2 groups.

RESULTS

Maximum airway pressure was higher in the VCV group. Pulmonary compliance was lower in the VCV group and minute ventilation was significantly lower in the group ventilated with PCV mode. The respiratory index was increased in the PCV group compared with the VCV group and with preoperative findings. Duration of mechanical ventilation was significantly shorter with PCV; however, intensive care unit and hospital stays did not differ.

CONCLUSION

There is not a single widely accepted and established mode of ventilation for patients with COPD undergoing open-heart surgery. Our modest experience indicated promising results with PCV mode; however, further studies are warranted.

Pulmonary perfusion with oxygenated blood or custodiol HTK solution during cardiac surgery for postoperative pulmonary function in COPD patients: a trial protocol for the randomized, clinical, parallel group, assessor and data analyst blinded Pulmonary Protection Trial

Background

Five to thirty percent of patients undergoing cardiac surgery present with chronic obstructive pulmonary disease (COPD) and have a 2- to 10-fold higher 30-day mortality risk. Cardiopulmonary bypass (CPB) creates a whole body systemic inflammatory response syndrome (SIRS) that could impair pulmonary function. Impaired pulmonary function can, however, be attenuated by pulmonary perfusion with oxygenated blood or custodiol HTK (histidine-tryptophan-ketoglutarate) solution.

Methods/Design

The Pulmonary Protection Trial (PP-Trial) randomizes 90 patients undergoing CPB-dependent cardiac surgery to evaluate whether pulmonary perfusion with oxygenated blood or custodiol HTK solution reduces postoperative pulmonary dysfunction in COPD patients. Further, we aim for a non-randomized evaluation of postoperative pulmonary function after transcatheter aortic-valve implantation (TAVI). The primary outcome measure is the oxygenation index measured from anesthesia induction to the end of surgery and until 24 hours after anesthesia induction for a total of six evaluations.

Discussion

Patients with COPD may be impaired by hypoxemia and SIRS. Thus, prolonged recovery and even postoperative complications and death may be reflected by the degree of hypoxemia and SIRS. The limited sample size does not aim for confirmatory conclusions on mortality, cardiovascular complications or risk of pneumonia and sepsis, but the PP-Trial is considered an important feasibility trial paving the road for a multicenter confirmatory trial.

Trial registration

ClinicalTrials.gov: NCT01614951.

Mitral valve replacements under on-pump beating heart and lung perfusion/ventilation using a minithoracotomy: an experience with 11 cases

BACKGROUND

The primary aims of minimally-invasive cardiac valve surgery are to lessen the impact of the incision, extracorporeal circulation, myocardial ischemia, and pulmonary ischemia, to obtain satisfactory therapeutic results, and to allow a quicker rehabilitation. In this study, the feasibility of minimally-invasive mitral valve replacements without ascending aorta and vena cava cross-clamping under beating heart was evaluated by surveying 11 patients.

METHODS

Preoperative risk factors, intraoperative techniques, and postoperative complications were surveyed and evaluated for one year (April 1, 2009 to March 30, 2010) in 11 patients who had undergone beating-heart mitral valve replacement surgery at The People's Hospital of Guangxi Zhuang Autonomous Region. Minithoracotomy and femoral arterial cannulation procedures were used in the surgeries for cardiopulmonary bypass (CPB) without ascending aorta and vena cava cross-clamping.

RESULTS

The operations were performed successfully in all 11 patients. The CPB time was 52.80 ± 11.36 minutes; the mean postoperative mechanical ventilation assistance time was 8.20 ± 2.84 hours; and the mean transfusion volume of red cells was 2.20 ± 1.04 units. There were no cerebral complications, no periprosthetic leakage, no occurrence of permanent high-degree atrioventricular blockage, and no mortality.

CONCLUSION

Mitral valve replacement on the beating heart using a minithoracotomy and femoral arterial cannulation for CPB without ascending aorta and vena cava crossclamping under pulmonary ventilation is feasible. A larger number of patients are required to further characterize the efficacy and safety of this procedure.

Beating-heart valve surgery: is the introduction of lung perfusion/ventilation the next step?

Myocardial and pulmonary ischemia during cardiopulmonary bypass has been associated with postoperative cardiac and pulmonary dysfunction, as well as poor outcomes. Beating-heart valve surgery utilizing continuous coronary perfusion with warm oxygenated blood via the antegrade/retrograde routes, is a novel strategy for myocardial protection. Conceptually, it is proposed that maintenance of pulmonary perfusion and ventilation during the cardiopulmonary bypass period also might be advantageous. The most current evidence regarding these evolving techniques and further areas of research are discussed in this article.

Lung ischemia-reperfusion injury: a molecular and clinical view on a complex pathophysiological process

Lung ischemia-reperfusion injury remains one of the major complications after cardiac bypass surgery and lung transplantation. Due to its dual blood supply system and the availability of oxygen from alveolar ventilation, the pathogenetic mechanisms of ischemia-reperfusion injury in the lungs are more complicated than in other organs, where loss of blood flow automatically leads to hypoxia. In this review, an extensive overview is given of the molecular and cellular mechanisms that are involved in the pathogenesis of lung ischemia-reperfusion injury and the possible therapeutic strategies to reduce or prevent it. In addition, the roles of neutrophils, alveolar macrophages, cytokines, and chemokines, as well as the alterations in the cell-death related pathways, are described in detail.

Gas Exchange during Lung Perfusion/Ventilation during Cardiopulmonary Bypass: Preliminary Results of a Pilot Study

Lung perfusion/ventilation was introduced as a means to minimize cardiopulmonary (CPB)-related pulmonary ischemic injury. Current results in the literature are divergent, and the role of gas exchange during lung perfusion/ventilation during CPB, remains undefined. This report details a) the technique of continuous lung perfusion/ventilation during CPB, b) provides initial observations, and c) discusses gas exchange during CPB.

Pulsatile pulmonary perfusion during cardiopulmonary bypass reduces the pulmonary inflammatory response

BACKGROUND

Pulmonary dysfunction presumably linked to an inflammatory response is frequent after cardiac operations using cardiopulmonary bypass (CPB) and pulmonary hypoperfusion. We previously demonstrated that active perfusion of the lungs during CPB reduces ischemic lung injury. We now hypothesized that avoiding ischemia of the lungs during CPB by active pulmonary perfusion would decrease pulmonary inflammatory response.

METHODS

Pigs were randomized to a control group with CPB for 120 minutes, followed by 120 minutes of postbypass reperfusion, or to the study groups where animals underwent active pulmonary perfusion with pulsatile or nonpulsatile perfusion during CPB (n = 7 in each group). Activation of transcription factor activity (nuclear factor [NF]-kappaB and activating protein [AP]-1) was determined by electrophoretic mobility shift assay. Levels of proinflammatory protein expression (interleukin [IL]-1, IL-6, and tumor necrosis factor [TNF]-alpha) were quantified by enzyme-linked immunoabsorbent assay. Caspase-3 activity was measured using a fluorogenic assay.

RESULTS

The activation of transcription factor AP-1 and NF-kappaB was reduced in the pulsatile pulmonary perfusion group. The caspase-3 activity and the expression of IL-1, IL-6, and TNF-alpha revealed a significant decrease in the pulsatile and nonpulsatile pulmonary perfusion groups. Animals of the pulsatile pulmonary perfusion group showed significantly reduced IL-6 expression and caspase-3 activity compared with the nonpulsatile pulmonary perfusion group.

CONCLUSIONS

Active pulmonary perfusion reduces the inflammatory response and apoptosis in the lungs observed during conventional CPB. This effect is greatest when pulmonary perfusion is performed with pulsatility. The reduction in cytokine expression by pulsatile pulmonary perfusion might be mediated by AP-1 and NF-kappaB.

Mechanical Ventilation for Cardiac Support

Postoperative lung injury is a common, although decreasing, complication of cardiac surgery. This article discusses various means to prevent and minimize postoperative lung injury. These include lung-protective strategies, pharmacologic strategies, and mechanical ventilation.

Risk Factors for Hypoxemia After Surgery for Acute Type A Aortic Dissection

PURPOSE

Postoperative hypoxemia is a frequent complication of surgery for acute type A aortic dissection. We tried to determine the factors associated with postoperative hypoxemia.

METHODS

Between 1997 and 2003, 114 patients underwent surgery for acute type A aortic dissection. Multivariate logistic regression analysis was done to identify the independent predictors of postoperative hypoxemia, defined by an arterial partial oxygen/inspired oxygen fraction (PaO(2)/FiO(2)) ratio of 200 or lower.

RESULTS

The overall in-hospital mortality was 6.1% (7 of 114 patients), being 5.2% in the hypoxemia group and 6.9% in the non-hypoxemia group. The ventilation time and intensive care unit stay were significantly longer in the hypoxemia group than in the non-hypoxemia group (P = 0.0044, P = 0.038, respectively). Logistic regression identified the following variables as predictors for postoperative hypoxemia: body mass index > or = 25 (odds ratio [OR], 5.6; 95% confidence interval [CI], 2.1-15.01; P < 0.001), preoperative PaO(2)/FiO(2) ratio < or = 300 (OR, 2.6; 95% CI, 1.09-6.13; P = 0.031), and the volume of transfused blood (OR, 1.08; 95% CI, 1.01-1.18; P = 0.037).

CONCLUSIONS

Initiating early treatment for hypoxemia and reducing the volume of blood transfused intraoperatively may improve the postoperative clinical course of obese patients with preoperative hypoxemia.

Whole-body moderate hypothermia confers protection from wood smoke-induced acute lung injury in rats: The therapeutic window*

OBJECTIVE

Toxic smoke inhalation causes acute lung injury. We studied the efficacy and therapeutic window of whole-body hypothermia in rats with wood smoke-induced acute lung injury.

DESIGN

Randomized, controlled study.

SETTING

Research laboratory.

SUBJECTS

Anesthetized, paralyzed, and artificially ventilated rats (n = 100) were used.

INTERVENTIONS

Air or wood smoke (30 breaths) was delivered into the lung using a respirator. Immediately after challenge, the rat's colonic temperature was kept a) 37 degrees C (normothermia, NT) for 1 (NT-1-Air and NT-1-Smoke), 2.5 (NT-2.5-Air and NT-2.5-Smoke), or 5 hrs (NT-5-Air and NT-5-Smoke) in six groups; b) 30 degrees C (hypothermia, HT) for 2.5 (HT-2.5-Smoke) or 5 hrs (HT-5-Air and HT-5-Smoke) in three groups; c) 30 degrees C for the first 2.5 hrs followed by 37 degrees C for another 2.5 hrs (HT-NT-5-Smoke) in one group; or d) 37 degrees C for the first 2.5 hrs followed by 30 degrees C for another 2.5 hrs (NT-HT-5-Smoke) in on group.

MEASUREMENTS AND MAIN RESULTS

Various acute lung injury indexes were assessed at 1, 2.5, or 5 hrs after challenge. In the air group, whole-body hypothermia did not affect the level of lung lipid peroxidation and the amount of proteins, total and differential cell counts, and concentrations of tumor necrosis factor-alpha and interleukin-1beta in bronchoalveolar lavage fluid. In the smoke groups, these acute lung injury indexes were increased showing that NT-5-Smoke > NT-2.5-Smoke > NT-1-Smoke. Whole-body hypothermia prevented increases in these acute lung injury indexes in the HT-2.5-Smoke and HT-5-Smoke groups. The efficacy of whole-body hypothermia in the HT-NT-5-Smoke group was superior to that in the NT-HT-5-Smoke group and similar to that in the HT-5-Smoke group. Whole-body hypothermia also alleviated smoke-induced poor gas exchange, pulmonary edema, and pathohistologic injurious signs.

CONCLUSIONS

Whole-body hypothermia confers protection from wood smoke-induced acute lung injury in rats by suppressing oxidant bronchoalveolar damage and pulmonary inflammation. Early and short-period (2 hrs) application of whole-body hypothermia provides favorable therapeutic effects.

Quantitative isolation of alphalAT mutant Z protein polymers from human and mouse livers and the effect of heat

Alpha-1-antitrypsin (alpha1AT) deficiency in its most common form is caused by homozygosity for the alpha1AT mutant Z gene. This gene encodes a mutant Z secretory protein, primarily synthesized in the liver, that assumes an abnormal conformation and accumulates within hepatocytes causing liver cell injury. Studies have shown that mutant alpha1ATZ protein molecules form unique protein polymers. These Z protein polymers have been hypothesized to play a critical role in the pathophysiology of liver injury in this disease, although a lack of quantitative methods to isolate the polymers from whole liver has hampered further analysis. In this study, we demonstrate a quantitative alpha1ATZ polymer isolation technique from whole liver and show that the hepatocellular periodic acid-Schiff-positive globular inclusions that are the histopathological hallmark of this disease are composed almost entirely of the polymerized alpha1ATZ protein. Furthermore, we examine the previously proposed but untested hypothesis that induction of alpha1ATZ polymerization by the heat of physiological fever is part of the mechanism of hepatic alpha1ATZ protein accumulation. The results, however, show that fever-range temperature elevations have no detectable effect on steady-state levels of intrahepatic Z protein polymer in a model in vivo system. In conclusion, methods to separate insoluble protein aggregates from liver can be used for quantitative isolation of alpha1ATZ protein polymers, and the effect of heat from physiological fever may be different in vivo compared with in vitro systems.

Na /H+ exchange inhibitor cariporide: effects on respiratory dysfunction after cardiopulmonary bypass

The purpose of the present study was to evaluate the potential of the Na+/H+ exchange inhibitor cariporide to protect the lung from injury after cardiopulmonary bypass (CPB). In a randomized placebo-controlled study, 16 pigs were subjected to CPB for 75 min. Administration of vehicle or cariporide (bolus 180 mg, 40 mg/hour) began 30 min pre-CPB and was continued throughout the protocol. The alveolo-arterial O2-gradient (AaDO2), the pulmonary shunt (Qs/Qt), the compliance (Cpl), haemodynamic variables and glycerol and water content in lung tissue were measured 10 min before and up to 180 min post-CPB. All animals in the control versus 75% in the cariporide group survived the experiment. At 5 and 60 min post-CPB, the mean AaDO2 and at 5, 60 and 180 min post-CPB, the mean pulmonary vascular resistance index were higher in the cariporide group (p < 0.05), respectively. More lung water accumulation was found in the cariporide group (p < 0.05). Mean Cpl decreased; the Qs/ Qt and glycerol in lung tissue increased without significant intergroup difference. In this model, the inhibitor of the Na+/H+ antiporter showed no protective effect on lung injury after CPB and might even have harmful effects on pulmonary vascular tone and function.

Pilot study on prevention of lung injury during surgery for type A acute aortic dissection: no evident improvements with celsior flushing through the pulmonary artery

OBJECTIVE

Postoperative respiratory failure is a frequent and serious complication in patients with type A acute aortic dissection. Experimental evidence suggests that pulmonary artery perfusion using hypothermic protective solutions helps prevent lung injury. The aim of this pilot prospective study was to evaluate the effect of pulmonary artery flushing during selective cerebral perfusion (SCP) on lung function.

METHODS

Twenty patients referred for acute type A aortic dissection, who were free from preoperative respiratory dysfunction, were assigned prospectively and alternately to two treatment groups. Pulmonary flushing was performed during SCP in group P (10 patients), while conventional Kazui technique was applied in group N (10 patients). Lung perfusion consisted of single-shot hypothermic pulmonary artery flush with Celsior. Lung function was evaluated by intubation time, scoring of chest radiograms at 12 hours after CPB, and PaO2/FiO2 assessed from immediately before surgery to 72 hours after termination of cardiopulmonary bypass.

RESULTS

Incidence of pre, intra and post operative determinants of lung dysfunction proved homogeneous in both groups. Lung oxygenation function showed a marked post operative decline followed by a slow improvement in both groups. Analysis of respiratory ratios did not disclose significant differences even though the flushed group had a better performance in all study patients. The incidence of prolonged ventilator support (longer than 72 hours) (30% vs 20%, p = NS) and severity of x-ray pulmonary infiltrate score were comparable (mean score 1.7 +/- 0.71 vs 1.6 +/- 0.68, p = NS).

CONCLUSIONS

Pulmonary artery flushing with Celsior solution does not seem to provide an effective preservation of lung function.

New strategies to control the inflammatory response in cardiac surgery

PURPOSE OF REVIEW

To present and interpret data from recent clinical studies (July 2002-August 2003) of strategies to control the inflammatory response after cardiac surgery.

RECENT FINDINGS

Off-pump coronary artery bypass techniques, which avoid the need for extracorporeal circulation, attenuate the inflammatory response and appear to confer clinical benefit. Concerns regarding the quality of the revascularization after off-pump coronary artery bypass appear to have been allayed. At present, ventricular assist devices do not enhance the efficacy of off-pump coronary artery bypass. In patients undergoing cardiopulmonary bypass, heparin-coated circuits, hypothermic pulmonary perfusion, normoxic reperfusion after aortic unclamping, and modified ultrafiltration hold promise. Strategies to maintain perioperative haemodynamic stability, such as enoximone therapy, may be beneficial, particularly in elderly patients. Aprotinin may have important beneficial anti-inflammatory actions in higher-risk adult and paediatric patients. The therapeutic potential of corticosteroids, particularly when administered in multiple dosages is increasingly clear. Direct anti-mediator therapies that focus upon key effector molecules and pathways of the inflammatory response offer future therapeutic options.

SUMMARY

The potential for strategies that inhibit the inflammatory response to improve outcome after cardiac surgery is clear. Large-scale multicentre trials investigating the most promising strategies, including off-pump coronary artery bypass, heparin-coated circuits, and perioperative corticosteroid and aprotinin therapy, are urgently needed. These trials need to be restricted to the high-risk patient groups most likely to experience benefit. In the interim, the optimal strategy to minimize the inflammatory response to cardiac surgery will remain elusive.