Comparison of pulmonary gas exchange in OPCAB versus conventional CABG

Off-pump grafting does not reduce postoperative pulmonary dysfunction

Objectives Pulmonary dysfunction is a recognized postoperative complication that may be linked to use of cardiopulmonary bypass. The off-pump technique of coronary artery bypass aims to avoid some of the complications that may be related to cardiopulmonary bypass. In this study, we compared the influence of on-pump or off-pump coronary artery bypass on pulmonary gas exchange following routine surgery. Methods Fifty patients (mean age 60.4 ± 8.4 years) with no preexisting lung disease and good left ventricular function undergoing primary coronary artery bypass grafting were prospectively randomized to undergo surgery with or without cardiopulmonary bypass. Alveolar/arterial oxygen pressure gradients were calculated prior to induction of anesthesia while the patients were breathing room air, and repeated postoperatively during mechanical ventilation and after extubation while inspiring 3 specific fractions of oxygen. Results Baseline preoperative arterial blood gases and alveolar/arterial oxygen pressure gradients were similar in both groups. At both postoperative stages, the partial pressure of arterial oxygen and alveolar/arterial oxygen pressure gradients increased with increasing fraction of inspired oxygen, but there were no statistically significant differences between patients who underwent surgery with or without cardiopulmonary bypass, either during ventilation or after extubation. Conclusions Off-pump surgery is not associated with superior pulmonary gas exchange in the early postoperative period following routine coronary artery bypass grafting in patients with good left ventricular function and no preexisting lung disease.

The impact of off-pump surgery in end-organ function: practical end-points

Most surgeons perform coronary bypass surgery with the aid of cardiopulmonary bypass, which inflicts a massive systemic inflammatory response to the body leading to adverse clinical outcome. In an attempt to make CABG less invasive, interest have been diverted to the off pump technique.

The current review attempts to bring an insight onto the last ten years knowledge on the off-pump impact in end organ function, with an aim to draw some clear conclusions in order to allow practitioners to reflect on the subject.

Pulmonary Protection Strategies in Cardiac Surgery: Are We Making Any Progress?

Pulmonary dysfunction is a common complication of cardiac surgery. The mechanisms involved in the development of pulmonary dysfunction are multifactorial and can be related to the activation of inflammatory and oxidative stress pathways. Clinical manifestation varies from mild atelectasis to severe respiratory failure. Managing pulmonary dysfunction postcardiac surgery is a multistep process that starts before surgery and continues during both the operative and postoperative phases. Different pulmonary protection strategies have evolved over the years; however, the wide acceptance and clinical application of such techniques remain hindered by the poor level of evidence or the sample size of the studies. A better understanding of available modalities and/or combinations can result in the development of customised strategies for the different cohorts of patients with the potential to hence maximise patients and institutes benefits.

Off-pump coronary artery bypass grafting improves short-term outcomes in high-risk patients compared with on-pump coronary artery bypass grafting: Meta-analysis

OBJECTIVES

To assess the benefits and risks of off-pump coronary artery bypass (OPCAB) versus coronary artery bypass grafting (CABG) through a meta-analysis of randomized controlled trials (RCTs), and to investigate the relationship between outcomes and patient risk profile.

METHODS

PubMed, Embase, the Cumulative Index of Nursing and Allied Health Literature, Scopus, Web of Science, Cochrane Library, and major conference proceedings databases were searched for RCTs comparing OPCAB and CABG and reporting short-term (≤ 30 days) outcomes. Endpoints assessed were all-cause mortality, myocardial infarction (MI), and cerebral stroke.

RESULTS

The meta-analysis included 100 studies, with a total of 19,192 subjects. There was no difference between the 2 techniques with respect to all-cause mortality and MI (odds ratio [OR], 0.88; 95% confidence interval [CI], 0.71-1.09; P = .25; I(2) = 0% and OR, 0.90; 95% CI, 0.77-1.05; P = .19; I(2) = 0%, respectively). OPCAB was associated with a significant 28% reduction in the odds of cerebral stroke (OR, 0.72; 95% CI, 0.56-0.92; P = .009; I(2) = 0%). A significant relationship between patient risk profile and benefits from OPCAB was found in terms of all-cause mortality (P < .01), MI (P < .01), and cerebral stroke (P < .01).

CONCLUSIONS

OPCAB is associated with a significant reduction in the odds of cerebral stroke compared with conventional CABG. In addition, benefits of OPCAB in terms of death, MI, and cerebral stroke are significantly related to patient risk profile, suggesting that OPCAB should be strongly considered in high-risk patients.

Intersectin-1s: an important regulator of cellular and molecular pathways in lung injury

Abstract Acute lung injury (ALI) and acute respiratory distress syndrome (ARDS) are severe syndromes resulting from the diffuse damage of the pulmonary parenchyma. ALI and ARDS are induced by a plethora of local or systemic insults, leading to the activation of multiple pathways responsible for injury, resolution, and repair or scarring of the lungs. Despite the large efforts aimed at exploring the roles of different pathways in humans and animal models and the great strides made in understanding the pathogenesis of ALI/ARDS, the only viable treatment options are still dependent on ventilator and cardiovascular support. Investigation of the pathophysiological mechanisms responsible for initiation and resolution or advancement toward lung scarring in ALI/ARDS animal models led to a better understanding of the disease's complexity and helped in elucidating the links between ALI and systemic multiorgan failure. Although animal models of ALI/ARDS have pointed out a variety of new ideas for study, there are still limited data regarding the initiating factors, the critical steps in the progression of the disease, and the central mechanisms dictating its resolution or progression to lung scarring. Recent studies link deficiency of intersectin-1s (ITSN-1s), a prosurvival protein of lung endothelial cells, to endothelial barrier dysfunction and pulmonary edema as well as to the repair/recovery from ALI. This review discusses the effects of ITSN-1s deficiency on pulmonary endothelium and its significance in the pathology of ALI/ARDS.

Off-pump versus on-pump coronary artery bypass grafting for ischaemic heart disease

BACKGROUND

Coronary artery bypass grafting (CABG) is performed both without and with cardiopulmonary bypass, referred to as off-pump and on-pump CABG respectively. However, the preferable technique is unclear.

OBJECTIVES

To assess the benefits and harms of off-pump versus on-pump CABG in patients with ischaemic heart disease.

SEARCH METHODS

We searched the Cochrane Central Register of Controlled Trials (CENTRAL) on The Cochrane Library (Issue 1, 2011), MEDLINE (OVID, 1950 to February 2011), EMBASE (OVID, 1980 to February 2011), Science Citation Index Expanded on ISI Web of Science (1970 to February 2011) and CINAHL (EBSCOhost, 1981 to February 2011) on 2 February 2011. No language restrictions were applied.

SELECTION CRITERIA

Randomised clinical trials of off-pump versus on-pump CABG irrespective of language, publication status and blinding were selected for inclusion.

DATA COLLECTION AND ANALYSIS

For statistical analysis of dichotomous data risk ratio (RR) and for continuous data mean difference (MD) with 95% confidence intervals (CI) were used. Trial sequential analysis (TSA) was used for analysis to assess the risk of random error due to sparse data and to multiple updating of accumulating data.

MAIN RESULTS

Eighty-six trials (10,716 participants) were included. Ten trials (4,950 participants) were considered to be low risk of bias. Pooled analysis of all trials showed that off-pump CABG increased all-cause mortality compared with on-pump CABG (189/5,180 (3.7%) versus 160/5144 (3.1%); RR 1.24, 95% CI 1.01 to 1.53; P =.04). In the trials at low risk of bias the effect was more pronounced (154/2,485 (6.2%) versus 113/2,465 (4.6%), RR 1.35,95% CI 1.07 to 1.70; P =.01). TSA showed that the risk of random error on the result was unlikely. Off-pump CABG resulted in fewer distal anastomoses (MD -0.28; 95% CI -0.40 to -0.16, P <.00001). No significant differences in myocardial infarction, stroke, renal insufficiency, or coronary re-intervention were observed. Off-pump CABG reduced post-operative atrial fibrillation compared with on-pump CABG, however, in trials at low risk of bias, the estimated effect was not significantly different.

AUTHORS' CONCLUSIONS

Our systematic review did not demonstrate any significant benefit of off-pump compared with on-pump CABG regarding mortality, stroke, or myocardial infarction. In contrast, we observed better long-term survival in the group of patients undergoing on-pump CABG with the use of cardiopulmonary bypass and cardioplegic arrest. Based on the current evidence, on-pump CABG should continue to be the standard surgical treatment. However, off-pump CABG may be acceptable when there are contraindications for cannulation of the aorta and cardiopulmonary bypass. Further randomised clinical trials should address the optimal treatment in such patients.

Human models of acute lung injury

Acute lung injury (ALI) is a syndrome that is characterised by acute inflammation and tissue injury that affects normal gas exchange in the lungs. Hallmarks of ALI include dysfunction of the alveolar-capillary membrane resulting in increased vascular permeability, an influx of inflammatory cells into the lung and a local pro-coagulant state. Patients with ALI present with severe hypoxaemia and radiological evidence of bilateral pulmonary oedema. The syndrome has a mortality rate of approximately 35% and usually requires invasive mechanical ventilation. ALI can follow direct pulmonary insults, such as pneumonia, or occur indirectly as a result of blood-borne insults, commonly severe bacterial sepsis. Although animal models of ALI have been developed, none of them fully recapitulate the human disease. The differences between the human syndrome and the phenotype observed in animal models might, in part, explain why interventions that are successful in models have failed to translate into novel therapies. Improved animal models and the development of human in vivo and ex vivo models are therefore required. In this article, we consider the clinical features of ALI, discuss the limitations of current animal models and highlight how emerging human models of ALI might help to answer outstanding questions about this syndrome.

Effects of early vital capacity maneuver on respiratory variables during multivessel off-pump coronary artery bypass graft surgery

OBJECTIVES

Despite avoiding cardiopulmonary bypass, similar degrees of pulmonary impairment compared with on-pump coronary artery bypass surgery have been demonstrated in patients undergoing off-pump coronary artery bypass graft surgery (OPCAB) compared with on-pump coronary artery bypass surgery. To investigate the effects of an early vital capacity maneuver (VCM) on intrapulmonary shunt (Qs/Qt), oxygenation, and pulmonary outcome in OPCAB.

DESIGN

Prospective, randomized, controlled, double-blind clinical trial.

SETTING

Cardiothoracic operating room and intensive care unit (ICU) of a university hospital.

PATIENTS

Fifty patients scheduled for OPCAB were randomized to treatment with VCM or none.

INTERVENTIONS

After sternotomy, VCM was performed by inflating the lungs to 40 cm H2O and holding this pressure for 10 seconds.

MEASUREMENTS AND MAIN RESULTS

Qs/Qt, Pao2/Fio2 (P/F) ratio, and dynamic and static pulmonary compliances were measured before induction of anesthesia (T0), 15 minutes after tracheal intubation (T1), during Y-graft construction (T2), 15 minutes after completion of grafting (T3), 15 minutes after sternal closure (T4), and 3 hours after arrival at the ICU (T5). Qs/Qt was lower and P/F ratio was higher in the VCM group at T2 through T5. Pulmonary compliances were also higher in the VCM group at T4 and T5. Patients in the VCM group were extubated earlier.

CONCLUSIONS

The beneficial effects of an early VCM on Qs/Qt persisted into the period of ICU care, with an improvement in P/F ratio and preserved pulmonary compliances, leading to a shorter time to extubation.

Pulmonary injury after cardiopulmonary bypass: beneficial effects of low-frequency mechanical ventilation

OBJECTIVE

Pulmonary dysfunction is a frequent postoperative complication after cardiac surgery with cardiopulmonary bypass, and atelectasis is thought to be one of the main causes. The aim of this study was to evaluate whether low-frequency ventilation and continuous positive airway pressure during cardiopulmonary bypass reduce postcardiopulmonary bypass lung injury.

METHODS

Eighteen Yorkshire pigs were subjected to 120 minutes of cardiopulmonary bypass (1 hour of cardioplegic arrest) followed by 90 minutes of recovery before being sacrificed. Six animals served as control with the endotracheal tube open to atmosphere during cardiopulmonary bypass. The remaining animals were divided into 2 groups of 6: One group received continuous positive airway pressure of 5 cm H(2)O, and one group received low-frequency ventilation (5/minutes) during cardiopulmonary bypass. Lung tissue biopsy and bronchoalveolar lavage samples were obtained before and 90 minutes after discontinuation of cardiopulmonary bypass for measurement of adenine nucleotide (adenosine-5'-triphosphate, adenosine diphosphate, adenosine monophosphate), lactate dehydrogenase, DNA levels, and histology. Hemodynamic data and arterial blood gases were also collected through the study.

RESULTS

The hemodynamic parameters were similar in the 3 groups. After cardiopulmonary bypass, the low-frequency ventilation group showed significantly better oxygen tension and alveolar arterial oxygen gradient, higher adenine nucleotide, lower lactate dehydrogenase levels, and reduced histologic damage in lung biopsy, as well as lower DNA levels in bronchoalveolar lavage compared with the control group. The continuous positive airway pressure group showed only significantly reduced lactate dehydrogenase levels compared with control.

CONCLUSION

Low-frequency ventilation during cardiopulmonary bypass in a pig experimental model reduces tissue metabolic and histologic damage in the lungs and is associated with improved postoperative gas exchange.

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.

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

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

Mechanisms of pulmonary dysfunction after on-pump and off-pump cardiac surgery: a prospective cohort study

BACKGROUND

Pulmonary dysfunction following cardiac surgery is believed to be caused, at least in part, by a lung vascular injury and/or atelectasis following cardiopulmonary bypass (CPB) perfusion and collapse of non-ventilated lungs.

METHODS

To test this hypothesis, we studied the postoperative pulmonary leak index (PLI) for 67Ga-transferrin and (transpulmonary) extravascular lung water (EVLW) in consecutive patients undergoing on-pump (n = 31) and off-pump (n = 8) cardiac surgery. We also studied transfusion history, radiographs, ventilatory and gas exchange variables.

RESULTS

The postoperative PLI and EVLW were elevated above normal in 42 and 29% after on-pump surgery and 63 and 37% after off-pump surgery, respectively (ns). Transfusion of red blood cell (RBC) concentrates, PLI, EVLW, occurrence of atelectasis, ventilatory variables and duration of mechanical ventilation did not differ between groups, whereas patients with atelectasis had higher venous admixture and airway pressures than patients without atelectasis (P = 0.037 and 0.049). The PLI related to number of RBC concentrates infused (P = 0.025).

CONCLUSION

The lung vascular injury in about half of patients after cardiac surgery is not caused by CPB perfusion but by trauma necessitating RBC transfusion, so that off-pump surgery may not afford a benefit in this respect. However, atelectasis rather than lung vascular injury is a major determinant of postoperative pulmonary dysfunction, irrespective of CPB perfusion.

Off-Pump Surgery Is Associated With Reduced Occurrence of Stroke and Other Morbidity as Compared With Traditional Coronary Artery Bypass Grafting

Background and Purpose— There is growing enthusiasm for coronary artery bypass grafting (CABG) without cardiopulmonary bypass (CPB). Although deleterious effects of CPB are known, it remains to be proven that avoiding CPB will result in reduction in morbidity. We sought to determine whether off-pump surgery is associated with reduced occurrence of adverse outcomes as compared with CABG with CPB.

Methods— Studies were identified by searching the MEDLINE, EMBASE and the Cochrane Register 1980 to 2006 (February). We also searched the reference lists of randomized clinical trials (RCT) and reviews to look for additional studies. Study selection: RCTs comparing off-pump surgery to CABG with CPB. No restriction applied on the size of the trial or end point reports. Data extraction: 2 reviewers independently searched for studies, read abstracts and abstracted all data. Data synthesis: combined estimates were obtained using fixed or random effect meta-analyses. Relative risks and risk differences were calculated. Heterogeneity was assessed using χ 2 and I 2 values.

Results— There were 3996 patients enrolled in 41 RCTs (mean age 62, 22% female). No study reported information on race. Off-pump CABG was associated with a 50% reduction in the relative risk of stroke (95% CI, 7% to 73%), 30% reduction in atrial fibrillation (AF; 95% CI, 16% to 43%) and 48% reduction in wound infection (95% CI, 26% to 63%) with no heterogeneity among RCTs. This translated into avoidance of 10 strokes, 80 cases of AF and 40 infections per 1000 CABG. Fewer distal grafts were performed and there was evidence for >10 reinterventions per 1000 with off-pump CABG. Long-term follow-up is not yet reported in the trials.

Conclusions— Off-pump CABG is associated with reduced risk of stroke, AF and infections as compared with CABG with CPB. Evidence should be generalized taking into account RCT enrollment limitations, drawbacks related to training requirements, propensity to perform fewer grafts and likely reinterventions after off-pump surgery.