Bronchial artery perfusion during cardiopulmonary bypass does not prevent ischemia of the lung in piglets: assessment of bronchial artery blood flow with fluorescent microspheres

Effect of perioperative sigh ventilation on postoperative hypoxemia and pulmonary complications after on-pump cardiac surgery (E-SIGHT): study protocol for a randomized controlled trial

BACKGROUND

Postoperative hypoxemia and pulmonary complications remain a frequent event after on-pump cardiac surgery and mostly characterized by pulmonary atelectasis. Surfactant dysfunction or hyposecretion happens prior to atelectasis formation, and sigh represents the strongest stimulus for surfactant secretion. The role of sigh breaths added to conventional lung protective ventilation in reducing postoperative hypoxemia and pulmonary complications among cardiac surgery is unknown.

METHODS

The perioperative sigh ventilation in cardiac surgery (E-SIGHT) trial is a single-center, two-arm, randomized controlled trial. In total, 192 patients scheduled for elective cardiac surgery with cardiopulmonary bypass (CPB) and aortic cross-clamp will be randomized into one of the two treatment arms. In the experimental group, besides conventional lung protective ventilation, sigh volumes producing plateau pressures of 35 cmH2O (or 40 cmH2O for patients with body mass index > 35 kg/m2) delivered once every 6 min from intubation to extubation. In the control group, conventional lung protective ventilation without preplanned recruitment maneuvers is used. Lung protective ventilation (LPV) consists of low tidal volumes (6-8 mL/kg of predicted body weight) and positive end-expiratory pressure (PEEP) setting according to low PEEP/FiO2 table for acute respiratory distress syndrome (ARDS). The primary endpoint is time-weighted average SpO2/FiO2 ratio during the initial post-extubation hour. Main secondary endpoint is the severity of postoperative pulmonary complications (PPCs) computed by postoperative day 7.

DISCUSSION

The E-SIGHT trial will be the first randomized controlled trial to evaluate the impact of perioperative sigh ventilation on the postoperative outcomes after on-pump cardiac surgery. The trial will introduce and assess a novel perioperative ventilation approach to mitigate the risk of postoperative hypoxemia and PPCs in patients undergoing cardiac surgery. Also provide the basis for a future larger trial aiming at verifying the impact of sigh ventilation on postoperative pulmonary complications.

TRIAL REGISTRATION

ClinicalTrials.gov NCT06248320. Registered on January 30, 2024. Last updated February 26, 2024.

Annexin A2 Loss After Cardiopulmonary Bypass and Development of Acute Postoperative Respiratory Dysfunction in Children

The primary objective of this study was to determine whether expression of the multifunctional and adherens junction-regulating protein, annexin A2 (A2), is altered following cardiopulmonary bypass (CPB). A secondary objective was to determine whether depletion of A2 is associated with post-CPB organ dysfunction in children.

DESIGN

In a prospective, observational study conducted over a 1-year period in children undergoing cardiac surgery requiring CPB, we analyzed A2 expression in peripheral blood mononuclear cells at different time points. We then assessed the relationship of A2 expression with organ function at each time point in the early postoperative period.

SETTING

Twenty-three-bed mixed PICU in a tertiary academic center.

PARTICIPANTS

Patients 1 month to 18 years old undergoing cardiac surgery requiring CPB.

MEAN OUTCOME MEASUREMENTS AND RESULTS

We analyzed A2 expression in 22 enrolled subjects (n = 9, 1-23 mo old; n = 13, 2-18 yr old) and found a proteolysis-mediated decline in intact A2 immediately after bypass (p = 0.0009), reaching a median of 4% of baseline at 6 hours after bypass (p < 0.0001), and recovery by postoperative day 1. The degree of A2 depletion immediately after bypass in 1-23-month-olds correlated strongly with the extent of organ dysfunction, as measured by PICU admission Vasoactive-Ventilation-Renal (p = 0.004) and PEdiatric Logistic Organ Dysfunction-2 (p = 0.039) scores on postoperative day 1. A2 depletion immediately after bypass also correlated with more protracted requirement for both respiratory support (p = 0.007) and invasive ventilation (p = 0.013) in the 1-23-month-olds.

CONCLUSIONS AND RELEVANCE

The degree of depletion of A2 following CPB correlates with more severe organ dysfunction, especially acute respiratory compromise in children under 2 years. These findings suggest that loss of A2 may contribute to pulmonary microvascular leak in young children following CPB.

Changes in infant porcine pulmonary tissue oxylipins induced by cardiopulmonary bypass

BACKGROUND

Oxylipins are metabolites derived from fatty acids such as arachidonic acid (AA) and are key mediators in inflammation, host defense, and tissue injury. Serum oxylipins increase in adults after cardiopulmonary bypass (CPB) but tissue-level changes are poorly defined. The objective of this study was to characterize pulmonary tissue oxylipins in an infant porcine model of CPB with deep hypothermic circulatory arrest (DHCA).

METHODS

Infant pigs underwent CPB with DHCA. Controls received anesthesia only. Right upper and lower lobes of the lung underwent oxylipin analysis via liquid chromatography-tandem mass spectrometry. One-way ANOVA was utilized to assess differences in oxylipin concentrations across groups, followed by pairwise comparisons.

RESULTS

AA and multiple AA metabolites via cytochrome P450 (CYP450), lipoxygenase (LOX), and cyclooxygenase (COX) pathways were significantly increased in the upper and lower lobe of pigs exposed to CPB/DHCA as compared to controls. Multiple prostaglandin metabolites produced via COX were also significantly elevated in the lower lobes of control animals.

CONCLUSIONS

CPB/DHCA induces a significant increase in pulmonary tissue AA, with subsequent metabolism via COX, LOX, and CYP450 pathways. Interestingly, prostaglandins were also elevated in the lower lobes of the controls, suggesting a mechanism separate from CPB/DHCA. Future oxylipin studies are needed to better understand CPB-induced acute lung injury.

IMPACT

CPB/DHCA and, to a lesser extent, lung region influence pulmonary tissue-level AA metabolite production. Inflammatory mediator AA metabolites have been noted in previous studies to increase following CPB; however, this is the first study to look at pulmonary tissue-level differences following CPB/DHCA. Increases in many AA metabolites, including LOX- and CYP450-derived products, were seen in both upper and lower lobe of piglets following CPB/DHCA. COX-derived prostaglandin metabolites were increased not only in CPB upper and lower lobe but also in mechanically ventilated control lower lobe, suggesting an additional, separate mechanism from CPB/DCHA.

New Technology for the Use of Inhaled Nitric Oxide to Protect the Heart and Lungs during Operations with Cardiopulmonary Bypass

The aim of the study was to evaluate the effectiveness of a new technology for the use of inhaled nitric oxide (NO) for the heart and lung protection during operations with cardiopulmonary bypass (СРВ).

Association of Passive Lung Insufflation Oxygen Fraction in Adult Patients on Cardiopulmonary Bypass with Postoperative Pulmonary Outcomes: A Retrospective Cohort Study

OBJECTIVES

To determine whether F_IO₂ of passive lung insufflation during cardiopulmonary bypass correlates with postoperative pulmonary function.

DESIGN

A retrospective, observational study SETTING: A single-center, university-affiliated, specialist cardiothoracic center in the United Kingdom.

PARTICIPANTS

Adult patients presenting for nonemergency, nontransplant cardiac surgery requiring cardiopulmonary bypass without the need for deep hypothermic circulatory arrest between January 1, 2018, and December 31, 2018.

INTERVENTIONS

Passive insufflation of the lungs during cardiopulmonary bypass with fresh gas flow of varying F_IO₂. Patients were sorted retrospectively into low F_IO₂ (0.21-0.44), intermediate F_IO₂ (0.45-0.69), and high F_IO₂ (0.7-1.0) groups. The primary outcome was the difference between the PaO₂:F_IO₂ on the first postinduction blood gas and on the first blood gas recorded postoperatively in the intensive care unit (ICU) (delta PaO₂:F_IO₂). Secondary outcomes were ICU and hospital lengths of stay, requirement for respiratory support, and 30-day mortality.

MEASUREMENTS AND MAIN RESULTS

Nine hundred patients were included in the authors' analysis (low F_IO₂ n = 307, intermediate F_IO₂ n = 459, high F_IO₂ n = 134). There was no significant difference in delta PaO₂:F_IO₂ among the groups (low F_IO₂ = 52.5 [-38.8 to 152.4], intermediate F_IO₂ = 71.8 [-39.4 to 165.1], high F_IO₂ = 60.2 [-19.2 to 184.0], p = 0.25). There were no significant differences among groups for any secondary outcomes.

CONCLUSION

Fresh gas flow with a low F_IO₂ delivered to the lungs without positive airway pressure during cardiopulmonary bypass was not associated with improved postoperative pulmonary function when compared to higher F_IO₂ levels.

Chronic respiratory disease and survival outcomes after extracorporeal membrane oxygenation

Background

Quality of life following extracorporeal membrane oxygenation (ECMO) therapy is an important health issue. We aimed to describe the characteristics of patients who developed chronic respiratory disease (CRD) following ECMO therapy, and investigate the association between newly diagnosed post-ECMO CRDs and 5-year all-cause mortality among ECMO survivors.

Methods

We analyzed data from the National Health Insurance Service in South Korea. All adult patients who underwent ECMO therapy in the intensive care unit between 2006 and 2014 were included. ECMO survivors were defined as those who survived for 365 days after ECMO therapy. Chronic obstructive pulmonary disease (COPD), asthma, interstitial lung disease, lung cancer, lung disease due to external agents, obstructive sleep apnea, and lung tuberculosis were considered as CRDs.

Results

A total of 3055 ECMO survivors were included, and 345 (11.3%) were newly diagnosed with CRDs 365 days after ECMO therapy. The prevalence of asthma was the highest at 6.1% (185). In the multivariate logistic regression, ECMO survivors who underwent ECMO therapy for acute respiratory distress syndrome (ARDS) or respiratory failure had a 2.00-fold increase in post-ECMO CRD (95% confidence interval [CI]: 1.39 to 2.89; P < 0.001). In the multivariate Cox regression, newly diagnosed post-ECMO CRD was associated with a 1.47-fold (95% CI: 1.17 to 1.86; P = 0.001) higher 5-year all-cause mortality.

Conclusions

At 12 months after ECMO therapy, 11.3% of ECMO survivors were newly diagnosed with CRDs. Patients who underwent ECMO therapy for ARDS or respiratory failure were associated with a higher incidence of newly diagnosed post-ECMO CRD compared to those who underwent ECMO for other causes. Additionally, post-ECMO CRDs were associated with a higher 5-year all-cause mortality. Our results suggest that ECMO survivors with newly diagnosed post-ECMO CRD might be a high-risk group requiring dedicated interventions.

Supplementary Information

The online version contains supplementary material available at 10.1186/s12931-021-01796-8.

Pulmonary Complications of Cardiac Surgery

Cardiothoracic surgery posits an arrangement of large, significant hemodynamic, and physiologic alterations upon the human body, which predisposes a patient to develop pathology. The care of these patients in the postoperative realm requires an astute physician with deep understanding of the cardiopulmonary system, who is able to address subtle developing problems promptly, before the patient suffers further sequelae. In this review, we describe the presentation and management of an assortment of important complications which occur in the pulmonary system. In addition, we aim to shed better light upon how the physiology of a patient responds to the condition of cardiothoracic surgery.

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.

Pulmonary complications associated with veno-arterial extra-corporeal membrane oxygenation: a comprehensive review

Veno-arterial extracorporeal membrane oxygenation (VA-ECMO) is a life-saving technology that provides transient respiratory and circulatory support for patients with profound cardiogenic shock or refractory cardiac arrest. Among its potential complications, VA-ECMO may adversely affect lung function through various pathophysiological mechanisms. The interaction of blood components with the biomaterials of the extracorporeal membrane elicits a systemic inflammatory response which may increase pulmonary vascular permeability and promote the sequestration of polymorphonuclear neutrophils within the lung parenchyma. Also, VA-ECMO increases the afterload of the left ventricle (LV) through reverse flow within the thoracic aorta, resulting in increased LV filling pressure and pulmonary congestion. Furthermore, VA-ECMO may result in long-standing pulmonary hypoxia, due to partial shunting of the pulmonary circulation and to reduced pulsatile blood flow within the bronchial circulation. Ultimately, these different abnormalities may result in a state of persisting lung inflammation and fibrotic changes with concomitant functional impairment, which may compromise weaning from VA-ECMO and could possibly result in long-term lung dysfunction. This review presents the mechanisms of lung damage and dysfunction under VA-ECMO and discusses potential strategies to prevent and treat such alterations.

Multi-omic analysis of the effects of low frequency ventilation during cardiopulmonary bypass surgery

BACKGROUND

Heart surgery with cardio-pulmonary bypass (CPB) is associated with lung ischemia leading to injury and inflammation. It has been suggested this is a result of the lungs being kept deflated throughout the duration of CPB. Low frequency ventilation (LFV) during CPB has been proposed to reduce lung dysfunction.

METHODS

We used a semi-biased multi-omic approach to analyse lung biopsies taken before and after CPB from 37 patients undergoing coronary artery bypass surgery randomised to both lungs left collapsed or using LFV for the duration of CPB. We also examined inflammatory and oxidative stress markers from blood samples from the same patients.

RESULTS

30 genes were induced when the lungs were left collapsed and 80 by LFV. Post-surgery 26 genes were significantly higher in the LFV vs. lungs left collapsed, including genes associated with inflammation (e.g. IL6 and IL8) and hypoxia/ischemia (e.g. HIF1A, IER3 and FOS). Relatively few changes in protein levels were detected, perhaps reflecting the early time point or the importance of post-translational modifications. However, pathway analysis of proteomic data indicated that LFV was associated with increased "cellular component morphogenesis" and a decrease in "blood circulation". Lipidomic analysis did not identify any lipids significantly altered by either intervention.

DISCUSSION

Taken together these data indicate the keeping both lungs collapsed during CPB significantly induces lung damage, oxidative stress and inflammation. LFV during CPB increases these deleterious effects, potentially through prolonged surgery time, further decreasing blood flow to the lungs and enhancing hypoxia/ischemia.

Mitochondrial Aldehyde Dehydrogenase in Myocardial Ischemic and Ischemia-Reperfusion Injury

Myocardial ischemia-reperfusion (IR) injury during acute myocardial infarction or open-heart surgery would promote oxidative stress, leading to the accumulation of reactive aldehydes that cause cardiac damage. It has been well demonstrated that aldehyde dehydrogenase (ALDH)-2 is an important cardioprotective enzyme for its central role in the detoxification of reactive aldehydes. ALDH2 activation by small molecule activators is a promising approach for cardioprotection for myocardial IR injury.

A perioperative surgeon-controlled open-lung approach versus conventional protective ventilation with low positive end-expiratory pressure in cardiac surgery with cardiopulmonary bypass (PROVECS): study protocol for a randomized controlled trial

Background

Postoperative pulmonary complications (PPCs) are frequent after on-pump cardiac surgery. Cardiac surgery results in a complex pulmonary insult leading to high susceptibility to perioperative pulmonary atelectasis. For technical reasons, ventilator settings interact with the surgical procedure and traditionally, low levels of positive end-expiratory pressure (PEEP) have been used. The objective is to compare a perioperative, multimodal and surgeon-controlled open-lung approach with conventional protective ventilation with low PEEP to prevent PPCs in patients undergoing cardiac surgery.

Methods/design

The perioperative open-lung protective ventilation in cardiac surgery (PROVECS) trial is a multicenter, two-arm, randomized controlled trial. In total, 494 patients scheduled for elective cardiac surgery with cardiopulmonary bypass (CPB) and aortic cross-clamp will be randomized into one of the two treatment arms. In the experimental group, systematic recruitment maneuvers and perioperative high PEEP (8 cmH2O) are associated with ultra-protective ventilation during CPB. In this group, the settings of the ventilator are controlled by surgeons in relation to standardized protocol deviations. In the control group, no recruitment maneuvers, low levels of PEEP (2 cmH2O) and continuous positive airway pressure during CPB (2 cmH2O) are used. Low tidal volumes (6–8 mL/kg of predicted body weight) are used before and after CPB in each group. The primary endpoint is a composite of the single PPCs evaluated during the first 7 postoperative days.

Discussion

The PROVECS trial will be the first multicenter randomized controlled trial to evaluate the impact of a perioperative and multimodal open-lung ventilatory strategy on the occurrence of PPCs after on-pump cardiac surgery. The trial design includes standardized surgeon-controlled protocol deviations that guarantee a pragmatic approach. The results will help anesthesiologists and surgeons aiming to optimize ventilatory settings during cardiac surgery.

Trial registration

Clinical Trials.gov, NCT 02866578. Registered on 15 August 2016. Last updated 11 July 2017.

Electronic supplementary material

The online version of this article (10.1186/s13063-018-2967-y) contains supplementary material, which is available to authorized users.

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.

Alda-1 Attenuates Lung Ischemia-Reperfusion Injury by Reducing 4-Hydroxy-2-Nonenal in Alveolar Epithelial Cells

OBJECTIVES

Excessive oxidative stress is a main cause of lung ischemia-reperfusion injury, which often results in respiratory insufficiency after open-heart surgery for a cardiopulmonary bypass. Previous studies demonstrate that the activation of aldehyde dehydrogenase-2 could significantly reduce the oxidative stress mediated by toxic aldehydes and attenuate cardiac and cerebral ischemia-reperfusion injury. However, both the involvement of aldehydes and the protective effect of the aldehyde dehydrogenase-2 agonist, Alda-1, in lung ischemia-reperfusion injury remain unknown.

DESIGN

Prospective laboratory and animal investigation were conducted.

SETTING

State Key Laboratory of Cardiovascular Disease.

SUBJECTS

Primary human pulmonary alveolar epithelial cells, human pulmonary microvascular endothelial cells, and Sprague-Dawley rats.

INTERVENTIONS

A hypoxia/reoxygenation cell-culture model of human pulmonary alveolar epithelial cell, human pulmonary microvascular endothelial cell, and an isolated-perfused lung model were applied to mimic lung ischemia-reperfusion injury. We evaluated the effects of Alda-1 on aldehyde dehydrogenase-2 quantity and activity, on aldehyde levels and pulmonary protection.

MEASUREMENTS AND MAIN RESULTS

We have demonstrated that ischemia-reperfusion-induced pulmonary injury concomitantly induced aldehydes accumulation in human pulmonary alveolar epithelial cells and lung tissues, but not in human pulmonary microvascular endothelial cells. Moreover, Alda-1 pretreatment significantly elevated aldehyde dehydrogenase-2 activity, increased surfactant-associated protein C, and attenuated elevation of 4-hydroxy-2-nonenal, apoptosis, intercellular adhesion molecule-1, inflammatory response, and the permeability of pulmonary alveolar capillary barrier, thus alleviated injury.

CONCLUSIONS

Our study indicates that the accumulation of 4-hydroxy-2-nonenal plays an important role in lung ischemia-reperfusion injury. Alda-1 pretreatment can attenuate lung ischemia-reperfusion injury, possibly through the activation of aldehyde dehydrogenase-2, which in turn removes 4-hydroxy-2-nonenal in human pulmonary alveolar epithelial cells. Alda-1 pretreatment has clinical implications to protect lungs during cardiopulmonary bypass.

Pulmonary artery perfusion versus no pulmonary perfusion during cardiopulmonary bypass in patients with COPD: a randomised clinical trial

Introduction

Absence of pulmonary perfusion during cardiopulmonary bypass (CPB) may be associated with reduced postoperative oxygenation. Effects of active pulmonary artery perfusion were explored in patients with chronic obstructive pulmonary disease (COPD) undergoing cardiac surgery.

Methods

90 patients were randomised to receive pulmonary artery perfusion during CPB with either oxygenated blood (n=30) or histidine-tryptophan-ketoglutarate (HTK) solution (n=29) compared with no pulmonary perfusion (n=31). The coprimary outcomes were the inverse oxygenation index compared at 21 hours after starting CPB and longitudinally in a mixed-effects model (MEM). Secondary outcomes were tracheal intubation time, serious adverse events, mortality, days alive outside the intensive care unit (ICU) and outside the hospital.

Results

21 hours after starting CPB patients receiving pulmonary artery perfusion with normothermic oxygenated blood had a higher oxygenation index compared with no pulmonary perfusion (mean difference (MD) 0.94; 95% CI 0.05 to 1.83; p=0.04). The blood group had also a higher oxygenation index both longitudinally (MEM, p=0.009) and at 21 hours (MD 0.99; CI 0.29 to 1.69; p=0.007) compared with the HTK group. The latest result corresponds to a difference in the arterial partial pressure of oxygen of 23 mm Hg with a median fraction of inspired oxygen of 0.32. Yet the blood or HTK groups did not demonstrate a longitudinally higher oxygenation index compared with no pulmonary perfusion (MEM, p=0.57 and 0.17). Similarly, at 21 hours there was no difference in the oxygenation index between the HTK group and those no pulmonary perfusion (MD 0.06; 95% CI −0.73 to 0.86; p=0.87). There were no statistical significant differences between the groups for the secondary outcomes.

Discussion

Pulmonary artery perfusion with normothermic oxygenated blood during cardiopulmonary bypass appears to improve postoperative oxygenation in patients with COPD undergoing cardiac surgery. Pulmonary artery perfusion with hypothermic HTK solution does not seem to improve postoperative oxygenation.

Trial registration number

NCT01614951; Pre-results.

Lung Perfusion and Ventilation During Cardiopulmonary Bypass Reduces Early Structural Damage to Pulmonary Parenchyma

BACKGROUND

It is unclear whether maintaining pulmonary perfusion and ventilation during cardiopulmonary bypass (CPB) reduces pulmonary inflammatory tissue injury compared with standard CPB where the lungs are not ventilated and are minimally perfused. In this study, we tested the hypothesis that maintenance of lung perfusion and ventilation during CPB decreases regional lung inflammation, which may result in less pulmonary structural damage.

METHODS

Twenty-seven pigs were randomly allocated into a control group only submitted to sternotomy (n = 8), a standard CPB group (n = 9), or a lung perfusion group (n = 10), in which lung perfusion and ventilation were maintained during CPB. Hemodynamics, gas exchanges, respiratory mechanics, and systemic interleukins (ILs) were determined at baseline (T0), at the end of 90 minutes of CPB (T90), and 180 minutes after CPB (T180). Bronchoalveolar lavage (BAL) ILs were obtained at T0 and T180. Dorsal and ventral left lung tissue samples were examined for optical and electron microscopy.

RESULTS

At T90, there was a transient reduction in PaO2/FIO2 in CPB (126 ± 64 mm Hg) compared with the control and lung perfusion groups (296 ± 46 and 244 ± 57 mm Hg; P < 0.001), returning to baseline at T180. Serum ILs were not different among the groups throughout the study, whereas there were significant increases in BAL IL-6 (P < 0.001), IL-8 (P < 0.001), and IL-10 (P < 0.001) in both CPB and lung perfusion groups compared with the control group. Polymorphonuclear counts within the lung tissue were smaller in the lung perfusion group than in the CPB group (P = 0.006). Electron microscopy demonstrated extrusion of surfactant vesicles into the alveolar spaces and thickening of the alveolar septa in the CPB group, whereas alveolar and capillary histoarchitecture was better preserved in the lung perfusion group.

CONCLUSIONS

Maintenance of lung perfusion and ventilation during CPB attenuated early histologic signs of pulmonary inflammation and injury compared with standard CPB. Although increased compared with control animals, there were no differences in serum or BAL IL in animals receiving lung ventilation and perfusion during CPB compared with standard CPB.

The potential of the novel leukocyte removal filter in cardiopulmonary bypass

Cardiopulmonary bypass (CPB) is indispensable for cardiac surgery but leads to systemic inflammatory responses and leukocyte activation, possibly due to blood contact with the surface of the CPB unit, surgical, ischemic reperfusion injury, etc. Systemic inflammatory responses during CPB result in increased morbidity and mortality. Activation of leukocytes is an important part of this process and directly contributes to coagulopathy and hemorrhage. This inflammatory response may contribute to the development of postoperative complications, including myocardial dysfunction, respiratory failure, renal and neurologic dysfunction, altered liver function and ultimately, multiple organ failure. Various pharmacologic and mechanical strategies have been developed to minimize the systemic inflammatory response during CPB. For example, leukocyte removal filters were developed in the 1990s for incorporation into the CPB circuit. However, studies of this approach have yielded conflicting findings. The purpose of this was to review the studies of a novel leukocyte removal filter in patients undergoing CPB.

Impact of Cardiopulmonary Bypass on Respiratory Mucociliary Function in an Experimental Porcine Model

Background

The impact of cardiac surgery using cardiopulmonary bypass (CPB) on the respiratory mucociliary function is unknown. This study evaluated the effects of CPB and interruption of mechanical ventilation on the respiratory mucociliary system.

Methods

Twenty-two pigs were randomly assigned to the control (n = 10) or CPB group (n = 12). After the induction of anesthesia, a tracheostomy was performed, and tracheal tissue samples were excised (T0) from both groups. All animals underwent thoracotomy. In the CPB group, an aorto-bicaval CPB was installed and maintained for 90 minutes. During the CPB, mechanical ventilation was interrupted, and the tracheal tube was disconnected. A second tracheal tissue sample was obtained 180 minutes after the tracheostomy (T180). Mucus samples were collected from the trachea using a bronchoscope at T0, T90 and T180. Ciliary beat frequency (CBF) and in situ mucociliary transport (MCT) were studied in ex vivo tracheal epithelium. Mucus viscosity (MV) was assessed using a cone-plate viscometer. Qualitative tracheal histological analysis was performed at T180 tissue samples.

Results

CBF decreased in the CPB group (13.1 ± 1.9 Hz vs. 11.1 ± 2.1 Hz, p < 0.05) but not in the control group (13.1 ± 1 Hz vs. 13 ± 2.9 Hz). At T90, viscosity was increased in the CPB group compared to the control (p < 0.05). No significant differences were observed in in situ MCT. Tracheal histology in the CPB group showed areas of ciliated epithelium loss, submucosal edema and infiltration of inflammatory cells.

Conclusion

CPB acutely contributed to alterations in tracheal mucocilliary function.

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.

The Effect of Pulsatile Cardiopulmonary Bypass on Lung Function in Elderly Patients

Purpose

Cardiopulmonary bypass is still a major cause of lung injury and delay in pulmonary recovery after cardiac surgery. Although it has been shown that pulsatile flow induced by intra-aortic balloon pumping is beneficial for preserving lung function, it is not clear if the same beneficial effect can be accomplished with pulsatile flow generated in the extracorporeal circuit. Therefore, we investigated the effect of pulsatile flow, produced by a centrifugal pump, on lung function in elderly patients.

Methods

Serial measurements of lung biomarkers Clara cell 16 kD protein, surfactant protein D, and elastase were performed on blood samples from 37 elderly patients (≥75 years) who underwent elective aortic valve replacement surgery with CPB, either with pulsatile perfusion or continuous perfusion. Pulmonary function was assessed by postoperative ventilation time, the arterial blood oxygenation (PaO2/FiO2), the alveolar-arterial oxygen gradient (Aa-O2 gradient) and the pulmonary vascular resistance indexed by body surface area (PVRi).

Results

There was no difference in lung function between both groups, as assessed by the postoperative ventilation time, the PaO2/FiO2 ratio, and the Aa-O2 gradient. The PVRi, however, was significantly lower in the pulsatile perfusion group 15 mins after the administration of protamine (p<0.05). The plasma concentrations of the lung biomarkers increased during surgery and peaked at 1 h ICU, there were however no differences between groups.

Conclusions

Pulsatile flow does not seem beneficial to postoperative lung function in elderly patients. Moreover, pulsatile flow does not affect lung function on a subclinical level as assessed by lung biomarkers.

Controlled lung reperfusion to reduce pulmonary ischaemia/reperfusion injury after cardiopulmonary bypass in a porcine model

OBJECTIVES

Ischaemia/reperfusion (I/R) injury of the lungs contributes to pulmonary dysfunction after cardiac surgery with cardiopulmonary bypass (CPB), leading to increased morbidity and mortality of patients. This study investigated the value of controlled lung reperfusion strategies on lung ischaemia-reperfusion injury in a porcine CPB model.

METHODS

Pigs were subjected to routine CPB for 120 min with 60 min of blood cardioplegic cardiac arrest (CCA). Following CCA, the uncontrolled reperfusion (UR, n = 6) group was conventionally weaned from CPB. Two groups underwent controlled lung reperfusion strategies (CR group: controlled reperfusion conditions, n = 6; MR group: controlled reperfusion conditions and modified reperfusate, n = 6) via the pulmonary artery before CPB weaning. Sham-operated pigs (n = 7) served as controls. Animals were followed up until 4 h after CPB. Pulmonary function, haemodynamics, markers of inflammation, endothelial injury and oxidative stress as well as morphological lung alterations were analysed.

RESULTS

CPB (UR group) induced deterioration of pulmonary function (lung mechanics, oxygenation index and lung oedema). Also, controlled lung reperfusion groups (CR and MR) presented with pulmonary dysfunction after CPB. However, compared with UR, controlled lung reperfusion strategies (CR and MR) improved lung mechanics and reduced markers of oxidative stress, but without alteration of haemodynamics, oxygenation, inflammation, endothelial injury and lung morphology. Both controlled reperfusion groups were similar without relevant differences.

CONCLUSION

Controlled lung reperfusion strategies attenuated a decrease in lung mechanics and an increase in oxidative stress, indicating an influence on CPB-related pulmonary injury. However, they failed to avoid completely CPB-related lung injury, implying the need for additional strategies given the multifactorial pathophysiology of postoperative pulmonary dysfunction.

Deep hypothermic circulatory arrest with lung perfusion/ventilation in a patient with acute type a aortic dissection

A 50-year-old black male presented with acute type A aortic dissection. Surgical repair was performed under deep hypothermic circulatory arrest (DHCA) with lung perfusion/ventilation throughout the procedure. Details of the lung perfusion technique and its potential benefits and drawbacks are discussed.

Preoperative inhalation of milrinone attenuates inflammation in patients undergoing cardiac surgery with cardiopulmonary bypass

OBJECTIVES

The purpose of this study was to evaluate the effect of preoperative inhalation of milrinone on cardiopulmonary bypass (CPB)-related inflammation.

SUBJECTS AND METHODS

A total of 30 patients undergoing cardiac surgery were recruited and randomized for preoperative inhalation of milrinone (Mil group) or normal saline (NS group), respectively. Each group had 15 patients. Their hemodynamic parameters were measured and blood samples were obtained longitudinally. The levels of serum interleukin (IL-6), tumor necrosis factor-α (TNF-α), and matrix metalloproteinase (MMP)-9 were determined by ELISA.

RESULTS

The levels of serum IL-6, TNF-α, and MMP-9 significantly increased at the end of cardiac surgery and remained high for 24 h in both groups of patients. However, the levels of proinflammatory cytokines at the end of cardiac surgery in the Mil group of patients were significantly lower than those of the NS group of patients.

CONCLUSIONS

Our data indicated that preoperative inhalation of milrinone significantly mitigated CPB-related inflammation.

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.

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.

Pulmonary perfusion with L-arginine ameliorates post-cardiopulmonary bypass lung injury in a rabbit model

BACKGROUND

Post-cardiopulmonary bypass (CPB) lung injury is the combination of whole body inflammatory response and local ischemia-reperfusion (IR) injury. We investigated the benefit of pulmonary perfusion with L-arginine in protection against post-CPB lung injury.

METHODS

New Zealand white rabbits (n = 50, weight, 2.5-2.8 kg) were divided into five groups (n = 10 each): sham (sham sternotomy), CPB (CPB without pulmonary perfusion), perfusion (CPB with pulmonary perfusion), L-arginine (CPB with perfusion + L-arginine), and L-NAME (CPB with perfusion + L-NAME). The duration of CPB was 60 min followed by 2 h of reperfusion. Pulmonary perfusion was performed every 20 min through the pulmonary artery during CPB. Checking parameters included: (1) pulmonary vascular resistance, (2) pulmonary artery endothelium relaxation (organ chamber study), and (3) IR marker (myeloperoxidase) and inflammatory markers (TNF-α, IL-B, NF-κB).

RESULTS

CPB induced pulmonary artery endothelium dysfunction manifested by increased pulmonary vascular resistance and impaired pulmonary artery relaxation. Pulmonary perfusion could significantly reverse the phenomenon (P < 0.01) while provision of NO precursor-L-arginine with pulmonary perfusion together further possessed significant relaxation ability for pulmonary arterial endothelium compared with perfusion alone (P < 0.05). Accordingly, lung parenchyma myeloperoxidase activity and inflammatory cytokine level were also markedly increased after CPB (P < 0.05). Pulmonary perfusion could partially decrease the response, whereas additional L-arginine further attenuated inflammatory cytokine release (P < 0.05).

CONCLUSIONS

Pulmonary perfusion during CPB partially ameliorates CPB-induced lung injury. Pulmonary perfusion with L-arginine could further attenuate lung injury by restoring endothelial function and decreasing inflammatory response.

Pulmonary protection during cardiac surgery: systematic literature review

Ischemia-reperfusion injury occurs during heart surgery in which cardiopulmonary bypass is used. Current knowledge of the factors contributing to postoperative pulmonary dysfunction and the measures to avoid it are reviewed.

Pretreatment with edaravone reduces lung mitochondrial damage in an infant rabbit ischemia-reperfusion model

PURPOSE

Free radical scavenger edaravone has been approved as a new drug for treatment of stroke patients. The purpose of this study was to examine whether pretreatment with edaravone could attenuate ischemia-reperfusion (IR)-induced lung damage in infant rabbits.

METHODS

New Zealand White rabbits (Experimental Animal Center, Nanjing Medical University, Nanjing, China) at age from 15 to 21 days were subjected to sham operation, IR, or edaravone plus IR. Ischemia/reperfusion was induced by clamping the right pulmonary hilum for 1 hour and then removal of the clamp for 4 hours. Edaravone (1 mg/kg, intravenous) was given 5 minutes before ischemia. Concentrations of reactive oxygen species-hydroxyl radical (ROS-HR) and malondialdehyde (MDA), and activities of glutathione peroxidase (GSH-PX) and superoxide dismutase (SOD) in the lung tissue were measured. Mitochondrial membrane potential, swelling rate, and ultrastructure of the lung were analyzed, and histologic condition of the lung was evaluated.

RESULTS

Edaravone pretreatment reduced markedly the productions of ROS-HR and MDA and increased the activities of GSH-PX and SOD. It attenuated both IR-induced decrease in mitochondrial membrane potential from 60% to 14% and IR-induced increase in mitochondrial swelling. As results, the mitochondrial and lung tissue damages were less, leading to an improved survival rate in IR rabbits pretreated with edaravone compared with IR rabbits without the treatment.

CONCLUSION

Edaravone pretreatment reduces the IR-induced lung mitochondrial damage in infant rabbits.

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.

Elevated pulmonary dead space and coagulation abnormalities suggest lung microvascular thrombosis in patients undergoing cardiac surgery

OBJECTIVE

Inflammation has been shown to trigger microvascular thrombosis. Patients undergoing cardiac surgery sustain significant inflammatory insults to the lungs and in addition are routinely given anti-fibrinolytic agents to promote thrombosis. In view of these risk factors we investigated if evidence of pulmonary microvascular thrombosis occurs following cardiac surgery and, if so, whether a pre-operative heparin infusion may limit this.

DESIGN

Double-blind randomised controlled trial.

SETTING

Tertiary university affiliated hospital.

PATIENTS

Twenty patients undergoing elective cardiac surgery.

INTERVENTIONS

Patients were randomised to receive a pre-operative heparin infusion or placebo. All patients were administered aprotinin.

MEASUREMENTS AND RESULTS

Pulmonary microvascular obstruction was estimated by measuring the alveolar dead-space fraction. Pulmonary coagulation activation was estimated by measuring the ratio of prothrombin fragment levels in radial and pulmonary arterial blood. Systemic tissue plasminogen activator (t-PA) levels were also assessed. In the placebo group cardiac surgery triggered increased alveolar dead-space fraction levels and the onset of prothrombin fragment production in the pulmonary circulation. Administration of pre-operative heparin was associated with a lower alveolar dead-space fraction (p < 0.05) and reduced prothrombin fragment production in the pulmonary circulation (p < 0.05). Pre-operative heparin also increased baseline t-PA levels (p < 0.05).

CONCLUSION

The changes in the alveolar dead-space fraction and pulmonary coagulation activation suggest that pulmonary microvascular thrombosis develops during cardiac surgery and this may be limited by a pre-operative heparin infusion.

Intraaortic Balloon Pumping During Cardioplegic Arrest Preserves Lung Function in Patients With Chronic Obstructive Pulmonary Disease

BACKGROUND

Linear flow during cardiopulmonary bypass is considered a potential mechanism of lung damage in patients with chronic obstructive pulmonary disease (COPD). We evaluated differences in lung function of patients with COPD undergoing preoperative intraaortic balloon pumping (IABP), between linear flow during cardiopulmonary bypass (IABP-off) and maintenance of pulsatile flow (IABP-on at automatic 80 bpm) during cardioplegic arrest.

METHODS

Fifty patients with COPD undergoing preoperative IABP were randomized between January 2004 and July 2005 to receive nonpulsatile cardiopulmonary bypass with IABP discontinued during cardioplegic arrest (25 patients; group A), or IABP-induced pulsatile cardiopulmonary bypass (25 patients; group B). Hospital outcome, need for noninvasive ventilation, oxygenation (partial pressure of oxygen, arterial to fraction of inspired oxygen [Pao(2)/Fio(2])), respiratory system compliance, and scoring of chest radiographs were compared.

RESULTS

There were no hospital deaths, no IABP-related complications, and no differences in postoperative noninvasive ventilation (group A: 6 of 25, 24.0% vs group B: 5 of 25, 20%; p = not significant [NS]). One patient in both groups developed pneumonia (p = NS). Intensive care and hospital stay were comparable (p = NS). Group B showed lower intubation time (8.3 +/- 5.1 hours versus group A: 13.2 +/- 6.0; p = 0.001), better Pao(2)/Fio(2) at aortic declamping (369.5 +/- 93.7 mm Hg vs 225.7 +/- 99.3; p = 0.001) at admission in intensive care (321.3 +/- 96.9 vs 246.2 +/- 109.7; p = 0.003), and at 24 hours (349.8 +/- 100.4 vs 240.8 +/- 77.3; p = 0.003). The respiratory system compliance was better in group B at the end of surgery (56.4 +/- 8.2 mL/cm H(2)O vs 49.4 +/- 7.0; p = 0.004) and 8 hours postoperatively (76.4 +/- 8.2 vs 59.4 +/- 7.0; p = 0.0001), as well as scoring of chest radiograph at intensive care admission (0.20 +/- 0.41 vs 0.38 +/- 0.56; p = 0.05) and on the first day (0.26 +/- 0.45 vs 0.50 +/- 0.67; p = 0.025).

CONCLUSIONS

Automatic 80 bpm IABP during cardioplegic arrest preserves lung function in patients with COPD.

Regression of the systemic vasculature to the lung after removal of pulmonary artery obstruction

RATIONALE

Pulmonary artery occlusion stimulates angiogenesis in the systemic circulation of the ipsilateral lung and increases systemic- to-pulmonary blood flow. Whether this systemic neovascularization decreases after lung revascularization is unknown.

OBJECTIVES

To assess the influence of lung revascularization on anatomy and flow of bronchial vessels supplying a chronically ischemic lung in piglets.

METHODS

Piglets were studied before (control) and 5 wk after left pulmonary artery ligation and 5 wk after left pulmonary artery reimplantation into the pulmonary artery trunk. The systemic blood flow to the right and left lungs was measured using colored microspheres, and the bronchial vasculature was assessed using light-microscopic morphometry. Renal and total blood flow, systemic blood pressure, and pulmonary blood pressure were measured in each experimental condition.

MEASUREMENTS AND MAIN RESULTS

Systemic blood flow to the left lung increased from 0.4 +/- 0.1 to 11.5 +/- 3.8 ml/min/g (p < 0.05) after left pulmonary artery ligation and returned toward the control value (1.2 +/- 0.6 ml/min/g) after revascularization, whereas it remained unchanged in the right lung. The number of bronchial vessels increased twofold in the ligated lung (p = 0.01), and did not decrease after reperfusion; however, vessel diameters decreased markedly. Renal and total blood flows, as well as mean pulmonary and systemic arterial pressures, were similar in the three experimental conditions.

CONCLUSION

Revascularization after a period of left pulmonary artery occlusion normalizes the systemic blood flow to the left lung and induces partial loss of collateral vessels.

The biology of exhaled nitric oxide (NO) in ischemia–reperfusion-induced lung injury: A tale of dynamism of NO production and consumption

The main objective of this paper is to review the potential diagnostic roles of exhaled nitric oxide (NO) in evaluating ischemia-reperfusion-induced lung injury associated with cardiac surgery. We shall start by elaborating on current clinical practice of cardiac surgery and to arrive at the conclusion that clinically important ischemia-reperfusion injury is a common scenario of many forms of these surgical procedures. We shall conclude this part by establishing the clinical need for biomarkers of inflammation in cardiothoracic surgery and by proposing that exhaled NO could be an important new addition to our anaesthetic monitoring repertoire based on our expertise with exhaled breath monitoring. We shall then take a closer look at mechanisms of ischemia-reperfusion injury and will propose the role of reactive oxygen and nitrogen species as mediators and biomarkers of acute lung injury. This analysis will provide a good opportunity to highlight major potential mechanisms of altered NO production and bioactivity of NO. We shall conclude that multiple relevant mechanisms may either lead to increased production of NO or enhance consumption of NO, leaving us with the paradigm that NO maybe used either as a positive or negative biomarker of inflammation. In order to explore this dilemma further, we will investigate the predominant effect of oxidative stress on NO bioactivity in cell culture models of ischemia-reperfusion injury. We will then turn to animal models of ischemia-reperfusion injury to elucidate the ultimate effects of this condition on lung NO production and concentrations of NO in the lung. Finally, we shall complete this journey by highlighting the human relevance of these observations by reviewing our own experience at Harefield Hospital, UK, and that of others, regarding exhaled NO in ischemia-reperfusion injury associated with cardiac surgery and lung transplantation.

Effect of exogenous nitric oxide during cardiopulmonary bypass on lung postperfusion histology

We tested the hypothesis that nitric oxide (NO) administered during cardiopulmonary bypass (CPB) would preserve platelets and prevent postperfusion lung changes. Ten anesthetized Yorkshire pigs were put on normothermic CPB (right atrium to aorta) with a roller pump and membrane oxygenator for 1 hour. In the study group (n = 5), NO was delivered in the oxygenator's gas inflow line with a MiniNO system at 5-10 ppm throughout CPB. In controls (n = 5), NO was not used. Crystalloid solution and norepinephrine were used to maintain blood pressure > or = 60 mm Hg. Fifteen minutes after CPB termination, all pigs were killed with intravenous potassium chloride and exsanguinated via the right atrium. Organ samples were put in formalin solution, processed in paraffin blocks, and stained with hematoxylin and eosin. We did not observe any thrombi in any perfusion system. There were no differences observed in platelet counts and aggregation ability to ADP and collagen, or in neutrophil counts between groups. Bleeding times were similar between groups before and after CPB. Also, there was no significant difference in factor XIIa and fibrinopeptide A levels between groups. Methemoglobin did not exceed normal levels. Lungs were devoid of neutrophils after perfusion in NO-treated pigs, whereas many neutrophils were present in the respiratory membrane of controls. Low-dose exogenous NO in the oxygenator's gas intake has no demonstrable effect on platelet number or function, but prevents neutrophil adhesion to lungs with a possible beneficial effect on postperfusion pulmonary morbidity.

Clinical Effectiveness of Leukocyte Filtration During Cardiopulmonary Bypass in Patients with Chronic Obstructive Pulmonary Disease

BACKGROUND

We tested the hypothesis that leukocyte filtration during pulmonary reperfusion preserves pulmonary function and results in improved oxygenation after cardiopulmonary bypass (CPB) in patients with chronic obstructive pulmonary disease (COPD).

METHODS

In a prospective, randomized study, the treatment group consisted of 20 patients with COPD from consecutive open-heart procedures. A primed leukocyte filter was connected to the arterial line downstream of the standard arterial filter but was excluded from circulation. Circulated blood was directed through the leukocyte filter approximately 10 minutes before aortic cross-clamp removal and at early reperfusion for up to 30 minutes. These patients were compared to 20 additional COPD patients (controls) on whom systemic leukocyte filtration was not used during open-heart surgery.

RESULTS

There was no significant difference in gender, age, left ventricular ejection fraction, type of procedure, aortic cross-clamp time, perfusion time, preoperative FEV1 and preoperative respiratory index (Pao2/FiO2 ratio) between treatment and control groups. The respiratory index changed in the treatment group by +9.8% of baseline after completion of CPB, by -14.2% upon arrival in the intensive care unit (ICU), and by -19.6% 12 hours later, whereas in the control group, it changed by -14.5% (p < 0.05), -27.7%, and -24%, respectively. Leukocyte-depleted patients required shorter intubation time (20.4 +/- 16.1 hours), ICU stay (46.2 +/- 40.1 hours) and length of hospitalization (8.3 +/- 2.8 days) than controls (29.5 +/- 21.9 hours, p < 0.05; 75.5 +/- 34.9 hours, p < 0.005; and 10.4 +/- 3.5 days, p < 0.05, respectively). Surgical (30-day) mortality was zero in both groups.

CONCLUSIONS

In COPD patients having CPB, systemic leukocyte depletion at early reperfusion was associated with better oxygenation, shorter intubation time, and shorter ICU and hospital stays. Leukocyte filtration during CPB most likely preserves pulmonary function by ameliorating pulmonary reperfusion injury.

Importance of pulmonary artery perfusion in cardiac surgery

OBJECTIVE

To investigate the importance of pulmonary artery perfusion in cardiac surgery.

DESIGN

Prospective randomized study.

SETTING

University hospital.

PARTICIPANTS

Patients undergoing cardiac surgery.

INTERVENTIONS

Patients in whom the cross-clamp was applied only to the aorta were defined as group 1 (n = 11) and patients in whom the cross-clamp was applied to both the aorta and pulmonary artery were defined as group 2 (n = 11).

MEASUREMENT AND RESULTS

Tissue samples obtained from the lower lobe of the left lung before CPB, 20 minutes after cross-clamping, and 20 minutes after declamping were examined under light and electron microscopes. Electron microscopic examination revealed changes in the blood-air barrier, epithelial cells, pneumocytes, and basal membrane were more prominent in group 2. Changes in the leukocyte, neutrophil, and lymphocyte counts of blood samples obtained from the right atrium and right superior pulmonary vein before CPB and 5, 30, 60, and 90 minutes after the removal of clamp were also investigated. The transpulmonary difference was statistically significant at 5 and 30 minutes after declamping in group 1. In group 2, transpulmonary differences continued to be significant at 5, 30, 60, and 90 minutes after declamping. There was no difference between groups in terms of PaO(2)/F(I)O(2) ratio before CPB (group 1: 342.0 +/- 80.0 mmHg, group 2: 349.0 +/- 67.0 mmHg); however, a statistically significant difference was found between the groups 2 hours after declamping (group 1: 418.0 +/- 87.0 mmHg and group 2: 290.0 +/- 110.0 mmHg; p = 0.007).

CONCLUSION

Pulmonary artery perfusion was found to be important in cardiac surgery.

Effect of bronchial artery blood flow on cardiopulmonary bypass-induced lung injury

Cardiovascular surgery requiring cardiopulmonary bypass (CPB) is frequently complicated by postoperative lung injury. Bronchial artery (BA) blood flow has been hypothesized to attenuate this injury. The purpose of the present study was to determine the effect of BA blood flow on CPB-induced lung injury in anesthetized pigs. In eight pigs (BA ligated) the BA was ligated, whereas in six pigs (BA patent) the BA was identified but left intact. Warm (37°C) CPB was then performed in all pigs with complete occlusion of the pulmonary artery and deflated lungs to maximize lung injury. BA ligation significantly exacerbated nearly all aspects of pulmonary function beginning at 5 min post-CPB. At 25 min, BA-ligated pigs had a lower arterial Po2at a fraction of inspired oxygen of 1.0 (52 ± 5 vs. 312 ± 58 mmHg) and greater peak tracheal pressure (39 ± 6 vs. 15 ± 4 mmHg), pulmonary vascular resistance (11 ± 1 vs. 6 ± 1 mmHg·l–1·min), plasma TNF-α (1.2 ± 0.60 vs. 0.59 ± 0.092 ng/ml), extravascular lung water (11.7 ± 1.2 vs. 7.7 ± 0.5 ml/g blood-free dry weight), and pulmonary vascular protein permeability, as assessed by a decreased reflection coefficient for albumin (σalb; 0.53 ± 0.1 vs. 0.82 ± 0.05). There was a negative correlation ( R = 0.95, P < 0.001) between σalband the 25-min plasma TNF-α concentration. These results suggest that a severe decrease in BA blood flow during and after warm CPB causes increased pulmonary vascular permeability, edema formation, cytokine production, and severe arterial hypoxemia secondary to intrapulmonary shunt.

Initial experience with a new right ventricular support device for beating heart surgery

OBJECTIVE

Device supported beating heart surgery has been advocated to extend patient selection criteria for off-pump surgery. This article reports the initial experimental and clinical results with a novel paracardial right ventricular support device.

METHODS

Preclinical experiments were performed in two pigs. Ten elective patients with triple vessel disease were subjected to beating heart coronary artery bypass grafting surgery during right ventricular support by the paracardial device. Measurements included intraoperative hemodynamics during cardiac tilting, perioperative left ventricular ejection fraction (LVEF), hemolysis parameters, mortality and major morbidity events.

RESULTS

A mean of 3.2 +/- 0.2 distal anastomoses per patient were performed. Mean arterial pressure and central venous oxygen saturation remained stable during cardiac tilting. Perioperative LVEF did not vary significantly. Sixty-day mortality and postoperative infarction rate were 0%. Functional Canadian Cardiovascular Society class at 6 days after surgery was 1.2 +/- 0.1 vs. 3.3 +/- 0.2 pre-operatively.

CONCLUSION

In this initial clinical experience, application of the novel paracardial right ventricular support device proved to be safe and efficient.

The importance of pulmonary artery circulation during cardiopulmonary bypass

This study sought to determine changes in transpulmonary difference in blood cells and alveolar-arterial oxygen (A-aO2) gradient when pulmonary artery circulation was obstructed in patients undergoing coronary artery bypass grafting (CABG) with cardiopulmonary bypass (CPB). Eighteen patients were divided into group A (control group; X-clamp placed on aorta, n = 9) and group B (pulmonary ischaemia group; X-clamp placed on aorta and pulmonary artery, n = 9). Haematological parameters were compared before CPB and up to 90 min after declamping. A-aO2 gradient differences were compared before and 2 h and 6 h after declamping. A transpulmonary increase in leucocyte levels normalized after 60 min in group A but remained higher in group B. A transpulmonary increase in neutrophils normalized after 60 min in group A and 90 min in group B. Increased lymphocyte levels normalized after 30 min in group A and 90 min in group B. A-aO2 gradient was determined as: group A (294.8 +/- 74.3) and group B (321.2 +/- 73.3) before X-clamping; group A (132.7 +/- 22.7) and group B (236.6 +/- 41.5) 2 h after declamping; and group A (72.2 +/- 22.7) and group B (189.4 +/- 88.9) 6 h after declamping. When pulmonary artery circulation was obstructed during the X-clamping period, leucocyte, neutrophil and lymphocyte sequestration within both lungs increased, and an increased A-aO2 gradient was observed because of tissue damage. To prevent post-operative complications, precautions to maintain normal pulmonary artery circulation are recommended.

Cardiopulmonary bypass reduction of bronchial blood flow: a potential mechanism for lung injury in a neonatal pig model

BACKGROUND

During total cardiopulmonary bypass, blood flow to the lungs is limited to flow through the bronchial arteries. We tested the hypothesis that bronchial blood flow during cardiopulmonary bypass is insufficient to prevent ischemia of the lung and that perfusion of the pulmonary arteries with oxygenated blood during bypass would reduce lung injury.

METHODS

Eighteen piglets (5.0 +/- 0.5 kg) were subjected to 120 minutes of normothermic total cardiopulmonary bypass, followed by 60 minutes of postbypass perfusion. Nine of them received continuous pulmonary perfusion with oxygenated blood during bypass. Six additional piglets served as a control group and were mechanically ventilated after sternotomy for 180 minutes only. We quantitated bronchial arterial blood flow, tissue lactate content, and alveolar septal thickness and surface area. We also obtained bronchioalveolar lavage fluid samples.

RESULTS

With the beginning of cardiopulmonary bypass, bronchial arterial blood flow decreased to 13% of baseline (42.1 +/- 10.4 to 5.6 +/- 1.0 mL/min). It remained decreased until the end of bypass and returned to starting levels 60 minutes after bypass. The decrease in bronchial blood flow was associated with a 3-fold increase in tissue lactate content. At the end of reperfusion there was a 2-fold increase in alveolar septal thickness and significant accumulations relative to control in the bronchoalveolar lavage fluid of albumin, lactate dehydrogenase, neutrophils, and elastase. Controlled pulmonary perfusion significantly ameliorated all the observed changes.

CONCLUSION

Cardiopulmonary bypass caused a reduction in bronchial arterial blood flow, which was associated with injury of the lung. Controlled pulmonary perfusion reduced injury to the lung during bypass. The inflammatory response, as evidenced by bronchoalveolar lavage fluid, may be caused by ischemia.