Reduction of pro-inflammatory cytokine levels and cellular adhesion in CABG procedures with separated pulmonary and systemic extracorporeal circulation without an oxygenator

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.

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 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.

A new rotary blood pump for versatile extracorporeal circulation: the DeltaStream™

Today, rotary pumps are routinely used for extracorporeal circulation in different clinical settings and applications. A review of these applications and specific limitations in extracorporeal perfusion was performed and served as a basis for the development of the DeltaStream®. The Delta- Stream® is a miniaturized rotary blood pump of a new and unique design with an integrated drive unit. Despite its small design, the pump maintains a sufficient hydraulic capacity, which makes the DeltaStream® very flexible for intra- and perioperative applications. It also opens the field for short-term ventricular assist devices (VAD) applications or use as a component in extracorporeal life support systems (ECLS). The DeltaStream® and, specifically, its impeller design have been optimized with respect to haemolysis and nonthrombogenicity. Also, the pump facilitates an effective pulse generation in VAD applications and simulates heart action in a more physiological way than other rotary pumps or roller pumps. Hydraulic and haematological properties have been tested in vitro and in vivo. In a series of seven animal experiments in two different setups, the pump demonstrated its biocompatibility and applicability. Basic aspects of the DeltaStream® pump concept as well as important console features are presented. A summary of the final investigation of this pump is given with focus on hydraulic capabilities and results from animal studies.

Strategies to prevent intraoperative lung injury during cardiopulmonary bypass

During open heart surgery the influence of a series of factors such as cardiopulmonary bypass (CPB), hypothermia, operation and anaesthesia, as well as medication and transfusion can cause a diffuse trauma in the lungs. This injury leads mostly to a postoperative interstitial pulmonary oedema and abnormal gas exchange. Substantial improvements in all of the above mentioned factors may lead to a better lung function postoperatively. By avoiding CPB, reducing its time, or by minimizing the extracorporeal surface area with the use of miniaturized circuits of CPB, beneficial effects on lung function are reported. In addition, replacement of circuit surface with biocompatible surfaces like heparin-coated, and material-independent sources of blood activation, a better postoperative lung function is observed. Meticulous myocardial protection by using hypothermia and cardioplegia methods during ischemia and reperfusion remain one of the cornerstones of postoperative lung function. The partial restoration of pulmonary artery perfusion during CPB possibly contributes to prevent pulmonary ischemia and lung dysfunction. Using medication such as corticosteroids and aprotinin, which protect the lungs during CPB, and leukocyte depletion filters for operations expected to exceed 90 minutes in CPB-time appear to be protective against the toxic impact of CPB in the lungs. The newer methods of ultrafiltration used to scavenge pro-inflammatory factors seem to be protective for the lung function. In a similar way, reducing the use of cardiotomy suction device, as well as the contact-time between free blood and pericardium, it is expected that the postoperative lung function will be improved.

Deleterious effects of cardiopulmonary bypass in coronary artery surgery and scientific interpretation of off-pump's logic

Cardiopulmonary bypass (CPB) has been suggested to be a cause of complex systemic inflammatory response that significantly contributes to several adverse postoperative complications. In the last few years, off-pump coronary artery bypass grafting (OPCAB) has gained widespread attention as an alternative technique to conventional on-pump coronary artery bypass grafting (ONCAB). However, a degree of uncertainty regarding the relative merits of ONCAB and OPCAB continues to be a significant issue. Surgeons supporting off-pump surgery, state that the avoidance of the CPB leads to significantly reduced myocardial ischemia-reperfusion injury, postoperative systemic inflammatory response and other biological derangements, a feature that may improve the clinical outcomes. However, perfection in perioperative care, surgical technique and methods of attenuating the untoward effects of CPB has resulted in better clinical outcome of ONCAB as well. Possible reasons of these controversial opinions are that high-quality studies have not comprehensively examined relevant patient outcomes and have enrolled a limited range of patients. Some studies may have been too small to detect clinically important differences in patient outcomes between these two modalities. We present a review of the available scientific interpretation of the literature on OPCAB with regard to safety, hemodynamic changes, inflammation, myocardial preservation and oxidative stress. We also sought to determine from different reported retrospective and randomized control studies, the initial and the long-term benefits of this approach, despite the substantial learning curve associated with OPCAB.

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.

Perfusing and ventilating the patient's lungs during bypass ameliorates the increase in extravascular thermal volume after coronary bypass grafting

BACKGROUND

To test the hypothesis that bilateral extracorporeal circulation (ECC) (Drew technique) ameliorates the increase in extravascular thermal volume (ETV) observed after conventional cardiopulmonary bypass (CPB) in patients undergoing coronary artery bypass grafting.

METHODS

Thirty-four consecutive patients underwent either bilateral ECC (n = 24, additional cannulation of pulmonary artery and left atrium and lungs perfused and ventilated during bypass) or conventional CPB (n = 10, right atrial and aortic cannulation, lungs statically inflated to 4 mbar (0.41 cm H(2)O) with oxygen, 500 mL/min). Determinations of ETV (thermodye dilution technique) and intraoperative fluid balance were made before surgery, at the end of surgery, and 4 hours thereafter. In addition, interleukin (IL)-8, thromboxane B2 (TxB(2)), and endothelin (ET)-1 concentrations were measured in the right atrium and pulmonary vein at specified time points.

RESULTS

Comparisons of ETV made at the start of surgery, after aortic declamping, and after termination of ECC, respectively, revealed an increase from 4.8 +/- 0.2 mL/kg (mean +/- SEM) to 6.7 +/- 0.4 mL/kg, and 6.3 +/- 0.3 mL/kg with conventional CPB but ETV remained unchanged at 5.2 +/- 0.3 mL/kg, 5.1 +/- 0.2 mL/kg, and 4.9 +/- 0.3 mL/kg with bilateral ECC. Priming volume (1,580 +/- 10 mL versus 2,213 +/- 77 mL, p < 0.001) and intraoperative fluid balance (+1,955 +/- 233 mL versus +2,654 +/- 210 mL, p < 0.05) were less with conventional CPB. Concentrations of IL-8, TxB(2), and ET-1 were not different between groups.

CONCLUSIONS

Despite a significantly greater prime volume and a more positive intraoperative fluid balance, ETV did not change with bilateral ECC but increased with conventional CPB. Thus, using the patient's lungs as an oxygenator during bypass mitigates the increase in extravascular pulmonary fluid.

Cardiac surgery with deep hypothermic circulatory arrest produces less systemic inflammatory response than low-flow cardiopulmonary bypass in newborns

OBJECTIVE

We sought to compare low-flow cardiopulmonary bypass with deep hypothermic circulatory arrest in respect to the influence on the systemic inflammatory response.

METHODS

Twenty-three infants weighing less than 10 kg and scheduled for repair of congenital malformations were enrolled in a randomized, controlled study. Eleven patients underwent cardiac surgery with deep hypothermic circulatory arrest (the DHCA group). Low-flow cardiopulmonary bypass was used in another 12 patients (the LF group). Interleukin 6 and 8 and anaphylatoxin C3a levels were measured 6 times perioperatively. Also, perioperative weight gain and a radiologic soft-tissue index were compared.

RESULTS

All patients had an uneventful clinical course. Duration of deep hypothermic circulatory arrest was 40 +/- 4 minutes; the bypass time was significantly shorter in the DHCA group (85 +/- 8 vs 130 +/- 19 minutes). However, the duration of the operation was similar in both groups (245 +/- 30 vs 246 +/- 30 minutes). During cardiopulmonary bypass (rewarming), the concentration of C3a (3751 +/- 388 vs 5761 +/- 1688 ng/mL, mean +/- SEM) was significantly lower in the DHCA group than in the LF group. The interleukin 8 level was significantly lower, and the interleukin 6 level had a tendency to be lower in the DHCA group compared with levels in the LF group. There was less weight gain on the first postoperative day in the DHCA group (65 +/- 61 vs 408 +/- 118 g). The soft-tissue index suggested reduced edema formation in the DHCA group.

CONCLUSION

Deep hypothermic circulatory arrest produces less systemic inflammatory response than low-flow cardiopulmonary bypass. In addition, there is an indication of less fluid accumulation postoperatively.

The systemic factor: the comparative roles of cardiopulmonary bypass and off-pump surgery in the genesis of patient injury during and following cardiac surgery

There is compelling evidence that off-pump coronary artery bypass operations are associated with reduced circulating levels of inflammatory mediators. Whereas complement activation and release of acute-phase reactants such as interleukin-6 are still expected to occur as consequences of a nonbypass-related general surgical trauma, a major feature of off-pump surgery seems to be a decreased production of interleukin-8, which may have important practical implications because of the participation of this cytokine in neutrophil trafficking and myocardial injury. The scarcity of carefully controlled, randomized trials precludes firm conclusions regarding the extent to which these biological changes translate into meaningful improvements in clinical outcomes. The problem is further complicated by the fact that the adverse effects of cardiopulmonary bypass largely depend on a genetically controlled balance between proinflammatory and antiinflammatory mediators. Currently, it is still impossible to predict, in a given patient, the side toward which this balance will be shifted. Nevertheless, accumulating experience identifies patient subgroups who may greatly benefit from avoiding extracorporeal circulation. These subsets include patients with severe extracardiac comorbidities (in particular, renal failure) and, possibly, patients with advanced left ventricular dysfunction, who may poorly tolerate superimposed, bypass-related, inflammatory tissue injuries.

Is there a role for extracorporeal life support after stage I Norwood?

OBJECTIVES

Controversy still surrounds the use of extracorporeal life support (ECLS) in patients with single ventricle physiology. An analysis of the experience with a group of neonates who underwent stage I Norwood palliation and received ECLS is reported.

METHODS

A retrospective review of hospital records, operative notes and perfusion data was performed in a group of 12 consecutive patients undergoing ECLS in the perioperative period after stage I. An analysis to identify risk factors for poor outcome was performed.

RESULTS

The mean age and weight were 3.9 days (1-14) and 2.6 kg (1.4-3.8), respectively. There were 3/12 patients under 2.5 kg and four patients were under 35 weeks of gestation. The most common diagnosis (7/12) was hypoplastic left heart syndrome with aortic atresia. Associated extracardiac anomalies were present in four patients. Three patients had an additional cardiac defect and two of these required an additional surgical procedure besides the stage I Norwood. The mean circulatory arrest was 56 min (46-63). ECLS was initiated preoperatively in one, intraoperatively in nine, and postoperatively in two patients. The indication for support was: arrhythmia (one), low output (six), cardiac arrest (three), unbalanced circulation (one), and hypoxemia (two). The mean duration of support was 68 h (24-192). Eight patients were weaned off support, and six were discharged home in good condition. Morbidity included sepsis in five, renal failure in five, neurologic sequelae in three, and bleeding in two. Prematurity, renal dysfunction and the initiation of ECLS outside the operating room were significantly associated with poor outcome. Residual hemodynamic effect, low birth weight and neurologic event showed a tendency towards poor outcome, but did not reach statistical significance.

CONCLUSIONS

Although the use of ECLS in patients with single ventricle physiology still carries a significant risk, prompt initiation of support can improve the outcome in a group of patients with impaired cardiopulmonary function after stage I palliation.