Pulmonary abnormalities after coronary arterial bypass grafting operation: cardiopulmonary bypass versus mechanical stabilization

Family nursing with the assistance of network improves clinical outcome and life quality in patients underwent coronary artery bypass grafting: A consolidated standards of reporting trials-compliant randomized controlled trial

BACKGROUND

Family nursing with the assistance of network (FNAN) improves nurses' practice and provides family/community-oriented nursing care. This study aimed to explore the effects of FNAN on the clinical outcome and life quality of coronary atherosclerotic heart disease (CHD) patients underwent coronary artery bypass grafting (CABG).

TRIAL DESIGN

This study is a randomized, placebo-controlled and double-blind trial.

METHODS

One-hundred and twelve patients underwent CABG were randomly divided into control group (CG, routine family nursing care) and experimental group (EG, FNAN) and the allocation ratio was 1:1. The situation of anxiety and depression were analyzed using the Hamilton Anxiety Scale (HAMA) scale and Hamilton Depression Scale (HAMD). Sleep quality was measured by using Pittsburgh Sleep Quality Index (PSQI). Lung function parameters were measured, including minute ventilation (MVV), partial pressure of oxygen (PaO2), partial pressure of arterial carbon dioxide (PaCO2), oxygen saturation measurement by pulse oximetry (SpO2), forced expiratory volume in 1 second (FEV1) and forced vital capacity (FVC). Life quality was measured by using Chronic Obstructive Pulmonary Disease Assessment Test (CAT).

RESULTS

After a 3-month intervention, 10 and 6 patients were lost in the CG and EG groups, respectively. The scores of HAMA, HAMD, PSQI and CAT were reduced in the EG group when compared with the CG group (P < .05). The values of MVV, PaO2, SpO2, FEV1 and FVC in the EG group was higher than those in the CG group whereas the levels of PaCO2 in the EG group was lower than those in the CG group (P < .05). PSQI score had a strong relationship with the values of MVV, PaO2, PaCO2, SpO2, FEV1, and FVC.

CONCLUSION

FNAN improves the clinical outcome and life quality in the patients underwent 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.

Leukocyte filtration and aprotinin: synergistic anti-inflammatory protection

Cardiopulmonary bypass activates an array of cellular and humoral inflammatory mechanisms that culminate in diverse or organ-specific injury. A manifestation of inflammatory injury to the heart, atrial fibrillation ranks among the most frequent and potentially life-threatening postsurgical complications. Pulmonary manifestations of the inflammatory response are also of major concern. Neutrophils activated by passage through the extracorporeal circuit inflict local injury and provoke the inflammatory cascade by producing oxyradicals and proinflammatory factors. This study tested if a combination of leukocyte depletion and aprotinin suppression of neutrophils could minimize postbypass atrial fibrillation and pulmonary dysfunction. In part one, two randomized groups of 90 patients undergoing primary coronary artery bypass grafting received full Hammersmith aprotinin alone (control group) or combined with leukofiltration (study group) and were prospectively examined. The dual treatment decreased the incidence of postoperative atrial fibrillation (7 of 90, 7.8%) by 67% versus aprotinin alone (21 of 90, 23.3%). Respiratory gas exchange in these patients was assessed from pulmonary shunt fraction. In the first two hours postbypass, pulmonary shunt fraction in the dual treatment group increased 40% less than in the group receiving aprotinin alone (p = 0.002), and subsided more quickly and completely over the next six hours. In part two, the cardiopulmonary bypass group receiving aprotinin+leukofiltration was retrospectively compared with 45 patients undergoing off-pump coronary revascularization. A strong, albeit not statistically significant trend (p= 0.08) toward a lower incidence of atrial fibrillation was found in the dual treatment group versus the off-pump group (8 of 45, 17.8%). These findings suggest that combining mechanical and pharmacologic suppression of the systemic inflammatory response could mitigate its deleterious arrhythmic and pulmonary complications.

Acute respiratory distress syndrome after cardiac surgery

Acute respiratory distress syndrome (ARDS) is a leading cause of postoperative respiratory failure, with a mortality rate approaching 40% in the general population and 80% in the subset of patients undergoing cardiac surgery. The increased risk of ARDS in these patients has traditionally been associated with the use of cardiopulmonary bypass (CPB), the need for blood product transfusions, large volume shifts, mechanical ventilation and direct surgical insult. Indeed, the impact of ARDS in the cardiac population is substantial, affecting not only survival but also in-hospital length of stay and long-term physical and psychological morbidity. No patient undergoing cardiac surgery can be considered ARDS risk-free. Early identification of those at higher risk is crucial to warrant the adoption of both surgical and non-surgical specific preventative strategies. The present review focuses on epidemiology, risk assessment, pathophysiology, prevention and management of ARDS in the specific setting of patients undergoing cardiac surgery.

Pulmonary Complications After Cardiac Surgery

Over the past two decades there has been a steady evolution in the practice of adult cardiac surgery with the introduction of “off-pump” surgery. However, respiratory complications remain a leading cause of postcardiac surgical morbidity and can prolong hospital stays and increase costs. The high incidence of pulmonary complications is in part due to the disruption of normal ventilatory function that is inherent to surgery in the thoracic region. Furthermore, patients undergoing such surgery often have underlying illnesses such as intrinsic lung disease (e.g., chronic obstructive pulmonary disease) and pulmonary dysfunction secondary to cardiac disease (e.g., congestive heart failure) that increase their susceptibility to postoperative respiratory problems. Given that many patients undergoing cardiac surgery are thus susceptiple to pulmonary complications, it is remarkable that more patients do not suffer from them during and after cardiac surgery. This is to a large degree because of advances in anesthetic, surgical and critical care that, for example, have reduced the physiological insults of surgery (e.g., better myocardial preservation techniques) and streamlined care in the immediate postoperative period (e.g., early extubation). Moreover, the development of minimally invasive surgery and nonbypass techniques are further evidence of the attempts at reducing the homeostatic disruptions of cardiac surgery. This review examines the available information on the incidences, consequences, and treatments of postcardiac surgery respiratory complications.

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.

ISMICS Consensus Conference and Statements of Randomized Controlled Trials of Off-Pump versus Conventional Coronary Artery Bypass Surgery

Objective

At this consensus conference, we developed evidence-informed consensus statements and recommendations on the practice of off-pump coronary artery bypass graft (OPCAB) by systematically reviewing and performing meta-analysis of the randomized controlled trials (RCTs) comparing OPCAB and conventional coronary artery bypass (CCAB).

Methods

All RCTs of OPCAB versus CCAB through April 2013 were screened, and 102 relevant RCTs (19,101 patients) were included in a systematic review and meta-analysis (15 RCTs of 9551 high-risk patients; and 87 RCTs of 9550 low-risk patients) in accordance with the Cochrane Collaboration and PRISMA (Preferred Reporting Items for Systematic Reviews and Meta-Analyses) methodology. Consensus statements for the risks and benefits of OPCAB surgery in mortality, morbidity, and resource use were developed based on best available evidence.

Results

Compared to CCAB, it is reasonable to perform OPCAB to reduce risks of stroke [class IIa, level of evidence (LOE) A], renal dysfunction/failure (class IIa, LOE A), blood transfusion (class I, LOE A), respiratory failure (class I, LOE A), atrial fibrillation (class I, LOE A), wound infection (class I, LOE A), ventilation time, and ICU and hospital length of stay (class I, LOE A). However, OPCAB may be associated with a reduced number of grafts performed (class I, LOE A) and with diminished graft patency (class IIa, LOE A, with increased coronary reintervention at 1 year and beyond (class IIa, LOE A), as well as increased mortality at a median follow-up of 5 years (class IIb, LOE A).

Conclusions

OPCAB compared with CCAB may improve outcomes in the short-term (stroke, renal dysfunction, blood transfusion, respiratory failure, atrial fibrillation, wound infection, ventilation time, and length of stay). However, over the longer-term, OPCAB may be associated with reduced graft patency, and increased risk of cardiac re-intervention and death.

Risk of stroke with percutaneous coronary intervention compared with on-pump and off-pump coronary artery bypass graft surgery: Evidence from a comprehensive network meta-analysis

BACKGROUND

Although some trials have reported that on-pump coronary artery bypass graft (CABG) surgery may be associated with higher rates of stroke than percutaneous coronary intervention (PCI), whether stroke is more common after off-pump CABG compared with PCI is unknown. We therefore sought to determine whether off-pump CABG is associated with an increased risk of stroke compared with PCI by means of network meta-analysis.

METHODS

Randomized controlled trials (RCTs) comparing CABG vs PCI were searched through MEDLINE, EMBASE, Cochrane databases, and proceedings of international meetings.

RESULTS

Eighty-three RCTs with 22,729 patients randomized to on-pump CABG (n = 10,957), off-pump CABG (n = 7,119), or PCI (n = 4,653) were analyzed. Thirty-day rates of stroke were significantly lower in patients treated with PCI compared with either off-pump CABG (odds ratio [OR]; 0.39, 95% CI, 0.19-0.83) or on-pump CABG (OR, 0.26; 95% CI, 0.12-0.47). Compared with on-pump CABG, off-pump CABG was associated with significantly lower 30-day risk of stroke (OR, 0.67; 95% CI, 0.41-0.95). However, in sensitivity analyses restricted to high-quality studies, studies with more than either 100 or 1,000 patients, or studies with protocol definition or adjudication of stroke by a clinical events committee, the precision of the point estimate for the 30-day risk of stroke between off-pump vs on-pump CABG was markedly reduced.

CONCLUSIONS

Percutaneous coronary intervention is associated with lower 30-day rates of stroke than both off-pump and on-pump CABG. Further studies are required to determine whether the risk of stroke is reduced with off-pump CABG compared with on-pump CABG.

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.

Assessment of pulmonary function tests in cardiac patients

This study was aimed to assess the pulmonary function tests (PFTs) in cardiac patients; with ischemic or rheumatic heart diseases as well as in patients who underwent coronary artery bypass graft (CABG) or valvular procedures. For the forty eligible participants, the pulmonary function was measured using the spirometry test before and after the cardiac surgery. Data collection sheet was used for the patient's demographic and intra-operative information. Cardiac diseases and surgeries had restrictive negative impact on PFTs. Before surgery, vital capacity (VC), forced vital capacity (FVC), forced expiratory volume in the first second (FEV1), ratio between FEV1 and FVC, and maximum voluntary ventilation (MVV) recorded lower values for rheumatic patients than ischemic patients (P values were 0.01, 0.005, 0.0001, 0.031, and 0.035, respectively). Moreover, patients who underwent valvular surgery had lower PFTs than patients who underwent CABG with significant differences for VC, FVC, FEV1, and MVV tests (P values were 0.043, 0.011, 0.040, and 0.020, respectively). No definite causative factor appeared to be responsible for those results although mechanical deficiency and incisional chest pain caused by cardiac surgery are doubtful. More comprehensive investigation is required to resolve the case.

Isoflurane pre-treatment before cardiopulmonary bypass alleviates neutrophil accumulation in dog lungs

OBJECTIVE

This study investigated the effect of isoflurane pretreatment on cardiopulmonary bypass (CPB)-related lung injury.

METHODS

Twelve dogs were randomly divided into two groups of six each. In one group, 1.0 minimum alveolar concentration (MAC) of isoflurane was dministered for 30 min before CPB, while the control group received no anaesthetic. Both groups then underwent 100 min of mild hypothermic CPB with 60-min aortic cross clamping. Haemodynamic parameters, respiratory mechanics and alveolar arterial oxygen difference (AaDO₂) were measured during the experiment. One hundred and fifty minutes after CPB, lung tissue samples from the non-dependent and dependent portions of the left and right lungs were harvested for polymorphonulear leukocyte (PMNs) counts.

RESULTS

Following CPB, within the control group, pulmonary vascular resistance (PVR) was significantly increased at 60, 120 and 180 min after declamping, AaDO₂ deteriorated at 180 min post-declamping, and dynamic lung compliance (DLC) was reduced dramatically after declamping. Isoflurane pretreatment before CPB significantly reduced PVR compared to the controls. AaDO₂ was impaired at 180 min after declamping and DLC was decreased after declamping within the isoflurane group. No differences in AaDO₂ and DLC were found between the isoflurane and control groups. At 180 min after declamping, the PMN count in both the non-dependent and dependent regions of the isoflurane pre-treated lungs was significantly lower than that of the controls.

CONCLUSIONS

Our results suggest that 30-min pre-treatment with 1.0 MAC isoflurane before CPB caused a reduction in PMN accumulation in the dog lungs, inhibition of increases in PVR, and it did not affect AaDO₂ in the early post-CPB stage.

Changes in airway and respiratory tissue mechanics after cardiac surgery

BACKGROUND

Because of the critical importance of the first postoperative week in the development of respiratory complications after cardiac surgery, the mechanical properties of the respiratory system in this period were followed up systematically.

METHODS

The input impedance of the respiratory system (Zrs) was measured during spontaneous breathing in patients (n=35) undergoing cardiac surgery on the day before surgery to establish the baseline, and for six days thereafter. The airway resistance was inferred from the average of the resistive component of Zrs, while the changes in respiratory elastance were assessed from the imaginary part of Zrs by model fitting. An assessment was made of the impact on the postoperative changes of factors characteristic of the patients (gender, age, smoking, and obesity) or the surgery duration and the need or not for a cardiopulmonary bypass.

RESULTS

Airway resistance increased immediately after extubation (peak rise on day 1, evening: 48+/-10%) and subsequently gradually decreased to the initial level, the recovery proving prolonged in obese patients. Postoperative elevation in elastance peaked later (day 2, evening: 83+/-14%), lasted longer, and was affected by both cardiopulmonary bypass (p<0.05) and obesity (p<0.005).

CONCLUSIONS

These findings demonstrate the need for particular attention in the postoperative management of patients after cardiac surgery in order to reduce the immediate airway symptoms, and to take steps to maintain the lungs open during the critical postoperative days 2 and 3, especially in obese patients and (or) if the surgery involves the use of cardiopulmonary bypass.

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.

Alveolar recruitment strategy during cardiopulmonary bypass does not improve postoperative gas exchange and lung function

Pulmonary dysfunction with impairment of lung function and oxygenation is one of the most serious problems in the early postoperative period after cardiac surgery. In this study we investigated the effect of alveolar recruitment strategy during cardiopulmonary bypass on postoperative gas exchange and lung function. This prospective randomized study included 32 patients undergoing elective myocardial revascularization with cardiopulmonary bypass. In 16 patients 5 cm H(2)O of positive end-expiratory pressure was applied after intubation and maintained until extubation (Group I). In the other 16 patients (group II) a positive end expiratory pressure (PEEP) of 5 cm H(2)O was maintained as well but was increased to 14 cm H(2)O every 20 min for 2 min during cross clamp. Measurements were taken preoperatively, before skin incision, before and after (3, 24, 48 h) cardiopulmonary bypass and before discharge (6th postoperative day). Postoperative gas exchange, extravascular lung water and lung function showed no significant difference between the groups. Postoperative pulmonary function variables were lower in both groups compared to baseline values. In patients with normal preoperative pulmonary function, application of an alveolar recruitment strategy during cardiopulmonary bypass does not improve postoperative gas exchange and lung function after cardiac surgery.

Clinical outcomes in randomized trials of off- vs. on-pump coronary artery bypass surgery: systematic review with meta-analyses and trial sequential analyses

AIMS

To assess the clinical outcomes of off- vs. on-pump coronary artery bypass surgery in randomized trials.

METHODS AND RESULTS

We searched electronic databases and bibliographies until June 2007. Trials were assessed for risk of bias. Outcome measures were all-cause mortality, myocardial infarction, stroke, atrial fibrillation, and renewed coronary revascularization at maximum follow-up. We applied trial sequential analysis to estimate the strength of evidence. We found 66 randomized trials. There was no statistically significant differences regarding mortality [relative risk (RR) 0.98; 95% confidence interval (CI) 0.66-1.44], myocardial infarction (RR 0.95; 95% CI 0.65-1.37), or renewed coronary revascularization (RR 1.34; 95% CI 0.83-2.18). We found a significant reduced risk of atrial fibrillation (RR 0.69; 95% CI 0.57-0.83) and stroke (RR 0.53; 95% CI 0.31-0.91) in off-pump patients. However, when continuity correction for zero-event trials was included, the reduction in stroke became insignificant (RR 0.62; 95% CI 0.32-1.19). Trial sequential analysis demonstrated overwhelming evidence supporting that off-pump bypass surgery reduces atrial fibrillation.

CONCLUSION

Off-pump surgery reduces the risks of postoperative atrial fibrillation compared with on-pump surgery. For death, myocardial infarction, stroke, and renewed coronary revascularization, the evidence is still weak and more low-bias risk trials are needed.

Current Status of Off-Pump Coronary Artery Bypass Surgery

The expanding indications for angioplasty coupled with the successful short and mid-term results of randomized controlled trials of drug-eluting stents have already had an unquestionable impact on the practice of coronary revascularization operations. However, coronary artery bypass grafting remains a major mode of therapy for coronary artery disease. It is likely that surgery will continue to be preferred for more complex subsets and that surgeons will have to continue to maintain good results in patients with more complex problems. Concerns regarding morbidity associated with conventional surgical myocardial revascularization on cardiopulmonary bypass have led to a resurgence of interest in off-pump bypass surgery during the last decade, with the expectation that it would be safer if cardiopulmonary bypass could be avoided. This review summarizes the impact of off-pump bypass surgery in reducing the morbidity and mortality associated with conventional coronary artery bypass on cardiopulmonary bypass by evaluating the current best-available evidence from randomized controlled trials and meta-analyses comparing off-pump surgery with conventional bypass grafting.

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.

Oxygenation and release of inflammatory mediators after off-pump compared with after on-pump coronary artery bypass surgery

BACKGROUND

In a previous study, we showed that oxygenation was impaired for up to 5 day after conventional coronary artery bypass grafting (CABG). As cardiopulmonary bypass (CPB) may have a detrimental effect on pulmonary function, we hypothesized that coronary revascularization grafting without the use of CPB (OPCAB) would affect post-operative oxygenation and release of inflammatory mediators less compared with CABG.

METHODS

Low-risk patients scheduled for elective coronary revascularization were randomly assigned to one of two groups (CABG, n = 17 or OPCAB, n = 18). Two parameters of oxygenation, shunt (%) and ventilation-perfusions mismatch, described as DeltaPO(2) (kPa), were estimated for up to 5 days post-operatively. Systemic release of interleukin (IL)-6, -8 and -10, C-reactive protein (CRP) and neutrophils were measured in peripheral blood samples for up to 3 days post-operatively. The lungs participation in the cytokine response was evaluated from mixed venous blood samples taken within the first 16 h post-operatively.

RESULTS

OPCAB was followed by a higher shunt (P = 0.047), with no difference (P = 0.47) in the deterioration of DeltaPO(2) between the groups. OPCAB was followed by an attenuated systemic release of IL-8 (P = 0.041) and IL-10 (P = 0.006), while the release of IL-6 (P = 0.94), CRP (P = 0.121) and neutrophils (P = 0.078) did not differ between the groups. Indications of an uptake of cytokines in the lungs were found after OPCAB.

CONCLUSIONS

When comparing OPCAB with CABG, oxygenation was more affected and only part of the systemic inflammatory response was attenuated.

The effect of mannitol on oxygenation and creatine kinase MB release in patients undergoing multivessel off-pump coronary artery bypass surgery

OBJECTIVES

Despite avoiding cardiopulmonary bypass, off-pump coronary artery bypass surgery is associated with reduction in PaO2 and postoperative respiratory compliance. Also, transient interruption of coronary flow is necessary during distal anastomoses and may impose ischemia-reperfusion myocardial injury. Mannitol is an osmotic diuretic with free radical scavenging properties, and we have evaluated the effects of mannitol on oxygenation and cardiac enzyme release in patients undergoing multivessel off-pump bypass surgery in a prospective, randomized, controlled, double-blind trial.

METHODS

Fifty patients were randomly allocated to receive either 20% mannitol 0.5 g/kg (n = 25) or normal saline 2.5 mL/kg (n = 25) during Y-graft construction. Pulmonary variables and serum sodium concentrations were measured 15 minutes after induction of anesthesia and sternum closure. Creatine kinase MB was measured before and after the operation. Intraoperative and postoperative fluid input and output, time to extubation, and intraoperative hemodynamic variables were also recorded.

RESULTS

PaO2 after sternum closure was significantly higher in the mannitol group, with faster time to extubation and shorter length of stay in the intensive care unit. Intraoperative urine output was significantly greater in the mannitol group, without significant differences in fluid input, serum sodium concentration, and hemodynamic variables. Number of patients with a creatine kinase MB level more than 3 times the upper limit of normal was significantly higher in the control group.

CONCLUSION

Mannitol could be safely used without adverse side effects in patients undergoing multivessel off-pump bypass surgery with beneficial effects in terms of preserving oxygenation, earlier extubation, and fewer patients with significant creatine kinase MB elevation.

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.

Comparison of pulmonary gas exchange in OPCAB versus conventional CABG

BACKGROUND

Cardiopulmonary bypass has been implicated as a cause of acute lung injury in cardiac surgical patients. This could be avoided with off-pump coronary artery bypass surgery. Aim. To ascertain the possible benefit of OPCAB surgery on pulmonary gas exchange.

METHODS

We randomized 75 consecutive patients (mean age 57 years) into two groups: Group 1 off-pump coronary artery bypass surgery (OPCAB), n=37, Group 2 conventional coronary artery bypass grafting (con CABG), n=38. Alveolar-arterial oxygen difference (A-aO(2) difference) was calculated pre-operatively, then 2 and 4h post-operatively. PaO(2)/FiO(2) ratio and respiratory index (RI) were calculated 2 and 4h post-operatively.

RESULTS

Alveolar-arterial O(2) gradient sharply increased in the immediate post-operative period, from 27mmHg pre-operatively, to 227mmHg 2h post-operatively, then declined to 152mmHg 4h post-operatively. PaO(2)/FiO(2) ratio and RI also showed severe worsening 2h post-operatively, with marked improvement at 4h. The pattern of physiological deterioration of gas exchange was similar in both the groups.

CONCLUSION

In terms of pulmonary gas exchange, similar degree of deterioration is noticed in CABG patients with or without cardiopulmonary bypass. OPCAB seems to provide no physiological benefit of gas exchange at the alveolar capillary membrane when compared to conventional CABG.

Impact of Off-Pump Coronary Artery Bypass Surgery on Postoperative Bleeding: Current Best Available Evidence

Cardiopulmonary bypass (CPB) is a prerequisite for open-heart surgery, and is a procedure routinely used. CPB exposes blood to artificial surfaces, to mechanical trauma from the pump, to alterations in temperature, and to dilution with fluids, whole blood, plasma products, and drugs, and leads to the activation of platelets, coagulation, and fibrinolysis. Coagulopathy during cardiac surgery with CPB results in impairment in hemostasis and subsequently higher morbidity and mortality. Recent advances in surgical techniques and postoperative management have aimed at reducing postoperative morbidity and mortality. Off-pump coronary artery bypass (OPCAB) surgery is one such advance that attempts to avoid the deleterious effects of extracorporeal circulation by performing myocardial revascularization without CPB. Emerging evidence from several randomized controlled trials (RCTs) as well as large registries such as the Society of Thoracic Surgeons (STS) database suggests that OPCAB reduces the postoperative morbidity and mortality. This review article attempts to evaluate the current best available evidence from RCTs on the impact of OPCAB on postoperative bleeding and transfusion requirements.

Off-Pump Coronary Artery Surgery for Reducing Mortality and Morbidity

OBJECTIVES

The purpose of this study was to assess the effects of off-pump coronary bypass surgery (OPCAB) on mortality and morbidity.

BACKGROUND

Despite its potential for reducing morbidity and mortality, OPCAB's role in clinical practice remains controversial.

METHODS

A meta-analysis of 37 randomized controlled trials (RCTs) (n = 3,449) and 22 risk-adjusted (logistic regression or propensity-score) observational studies (n = 293,617) was performed. Two reviewers performed literature searches (MEDLINE, EMBASE, PubMed, reference lists), quality assessment, and data extraction. Treatment effects were calculated as odds ratios (ORs) with 95% confidence intervals (CIs).

RESULTS

In RCTs, OPCAB was associated with reduced atrial fibrillation (OR 0.59; 95% CI 0.46 to 0.77) and trends toward reduced 30-day mortality (OR 0.91 95% CI 0.45 to 1.83), stroke (OR 0.52; 95% CI 0.25 to 1.05), and myocardial infarction (OR 0.79; 95% CI 0.50 to 1.25). Observational studies showed OPCAB to be associated with reduced 30-day mortality (OR 0.72; 95% CI 0.66 to 0.78), stroke (OR 0.62; 95% CI 0.55 to 0.69), infarction (OR 0.66; 95% CI 0.50 to 0.88), and atrial fibrillation (OR 0.78; 95% CI 0.74 to 0.82). At one to two years, OPCAB was associated with trends toward reduced mortality, but also increased repeat revascularization (RCT: OR 1.75, 95% CI 0.78 to 3.94; Observational: OR 1.35, 95% CI 0.76 to 2.39).

CONCLUSIONS

Randomized controlled trials did not find, aside from atrial fibrillation, the statistically significant reductions in short-term mortality and morbidity demonstrated by observational studies. These discrepancies might be due to differing patient-selection and study methodology. Future studies must focus on improving research methodology, recruiting high-risk patients, and collecting long-term data.

Effects on Lung Function in Patients Undergoing Coronary Artery Surgery on versus off Cardiopulmonary Bypass: A Randomized Trial

Background

Coronary revascularization is associated with respiratory dysfunction and poor gas exchange postoperatively. Cardiopulmonary bypass (CPB) has been implicated as a possible explanation for this phenomenon. This study investigated respiratory function in patients undergoing coronary artery bypass grafting (CABG) on-CPB versus off-CPB to determine whether the off-CPB condition results in improved postoperative pulmonary function.

Methods

Forty patients were randomized into 1 of 2 groups: CABG on-CPB (group A) or off-CPB (group B). Pulmonary function tests, including spirometry and diffusion studies, were performed preoperatively and on postoperative day 5. Arterial blood gases on 100% oxygen were taken preoperatively (TP1), 15 minutes after sternal closure (TP2), and 3 hours postoperatively (TP3).

Results

The arterial partial pressure of oxygen (PaO2) on FiO2 1.0 decreased from 59.5 ± 11.5 kPa and 55.7 ± 12.2 kPaat TP1 to 39.5 ± 16 kPa and 39.7 ± 13 kPa at TP2 in groups A and B, respectively (P < 0.001), with no significant difference between groups. At TP3, the PaO2 partially recovered toward preoperative levels (P < 0.05). Spirometry revealed a significant reduction in FEV1 and FVC on the fifth postoperative day (P < 0.001), with no significant difference between groups. The corrected transfer factor for carbon monoxide reduced significantly in group A from 7.9 ± 2.5 mmolmin–1 · kPa–1 preoperatively to 5.1 ± 1.6 mmolmin–1 · kPa–1 postoperatively (P < 0.05). This reduction was not seen in group B.

Conclusions

Coronary artery surgery is associated with a marked reduction in lung function as measured by pulmonary function tests and PaO2. Diffusion studies revealed that on-CPB patients had significantly reduced diffusion capacities postoperatively compared with patients in the off-CPB group.

Off-pump versus on-pump coronary artery bypass surgery and postoperative pulmonary dysfunction

OBJECTIVE

To investigate how off-pump coronary artery bypass grafting (CABG) affects postoperative pulmonary function when compared with on-pump CABG.

DESIGN

Prospective clinical study.

SETTING

University-affiliated teaching hospital.

PARTICIPANTS

Adult patients (n = 39) undergoing elective coronary artery bypass surgery with or without cardiopulmonary bypass.

INTERVENTIONS

Two groups of patients were compared: 19 consecutive patients undergoing off-pump CABG surgery and 20 consecutive patients undergoing conventional CABG surgery.

MEASUREMENTS AND MAIN RESULTS

Pulmonary function tests (flow volume loops and lung volumes with plethysmography) were done preoperatively and 72 hours postoperatively. Arterial blood gases and PaO2/FIO2 were measured at various stages. Sequential chest x-rays were obtained and evaluated for pleural changes, pulmonary edema, and atelectasis. In both groups, PaO2/FIO2 ratios decreased progressively throughout the perioperative period, with no significant differences between the groups at any stage during the study. There was a significant decline in postoperative pulmonary function tests in both groups, but there was no difference between groups at 72 hours postoperatively. No differences were found in the time to extubation, atelectasis scores, or postoperative complications.

CONCLUSIONS

Off-pump CABG does not confer major protection from postoperative pulmonary dysfunction compared with CABG surgery with CPB. Strategies for minimizing pulmonary impairment after CABG surgery should be directed to factors other than the use of CPB.

Effects of N-acetylcysteine on pulmonary function in patients undergoing coronary artery bypass surgery with cardiopulmonary bypass

Cardiopulmonary bypass (CPB) has been implicated in causing poor pulmonary gas exchange postoperatively in patients undergoing coronary artery bypass grafting (CABG) procedures. In this prospective, randomized, double-blind, placebo-controlled study, we examined the pulmonary effects of N-acetylcysteine (NAC) in patients undergoing CABG. Twenty patients undergoing elective CABG and early tracheal extubation were randomized into two groups. Group I (ten patients) received a physiologic salt solution as a placebo in a continuous intravenous infusion for one hour before CPB and 24 hours after CPB; Group II (ten patients) received 100 mg/ kg NAC intravenously for one hour before CPB and 40 mg/kg/day at 24 hours after CPB. Perioperative hemodynamic and pulmonary data were recorded. Postoperative tracheal extubation was accomplished at the earliest appropriate time. The postoperative clinical course was similar in the two groups. Both groups exhibited significant postoperative increases in A-a oxygen gradient (p < 0.01), but patients in Group II exhibited significantly lower increases in postoperative A-a oxygen gradient (p < 0.006). Other hemodynamic and pulmonary data (pulmonary capillary wedge pressure, pulmonary vascular resistance (PVR), cardiac index (CI), shunt flow, dynamic lung compliance and static lung compliance) exhibited no differences between the groups. There was no significant difference in terms of intubation time. The malondialdehyde (MDA) increase in Group II following CPB was found to be significantly lower than in Group I (p = 0.043). This clinical study reveals that administration of NAC to patients undergoing elective CABG with CPB improves systemic oxygenation. There was no effect in other pulmonary parameters and in terms of intubation time.

Side Effects of Cardiopulmonary Bypass:. What Is the Reality?

Despite many years of clinical and experimental research, the contribution of cardiopulmonary bypass (CPB) and cardioplegic arrest to morbidity and mortality following cardiac surgery remains unclear. This is due, in part, to lack of suitable control group against which bypass and cardioplegic arrest can be compared. The recent success of beating heart coronary artery bypass grafting has, however, for the first time, provided an opportunity to compare the same operation, in similar patient groups, with, or without CPB and cardioplegic arrest. CPB is associated with an acute phase reaction of protease cascades, leucocyte, and platelet activation that result in tissue injury. This is largely manifest as subclinical organ dysfunction that produces a clinical effect in those patients that generate an excessive inflammatory response or in those with limited functional reserve. The contribution of myocardial ischemia/reperfusion, secondary to aortic cross-clamping, and cardioplegic arrest, to the systemic inflammatory response and wider organ dysfunction is unknown, and requires further evaluation in clinical trials.

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.

Daily comparison of respiratory functions between on-pump and off-pump patients undergoing CABG

OBJECTIVE

Widespread application of on-pump revascularization procedures is increasing due to the thought of elimination of untoward effects of cardiopulmonary circuit. Thus, whether off-pump coronary artery surgery eliminates side effects especially related to respiratory functions is still controversial. Although many previous studies have evaluated these respiratory functions, daily comparison of 12 parameters was not included in any of the studies. The aim of our prospective study was to ascertain whether off-pump coronary operation improves pulmonary functions and postoperative recovery period when compared with on-pump technique and whether early discharge of patients with off-pump surgery is the result of respiratory improvement.

METHODS

Eighteen patients in each group were included: on-pump group underwent coronary revascularization with cardiopulmonary bypass and off-pump with stabilization. Respiratory function tests and arterial blood gas analyses were performed preoperatively and daily after operation function tests included forced expiratory volume (FEV) in 1s, forced vital capacity (FVC), expiratory reserve volume, vital capacity, quotient of FEV in 1s to FVC, maximal voluntary ventilation (MVV), tidal volume, and forced midexpiratory flow. Blood gas analyses included partial arterial oxygen and carbon dioxide pressure, arterial pH and hematocrit (Hct).

RESULTS

Preoperative pulmonary functions and arterial blood gases were not statistically significant between groups except MVV and partial arterial oxygen pressure. MVV was slightly higher in on-pump group and partial arterial oxygen pressure was slightly lower in on-pump group. During postoperative first day Hct (P=0.004) and FEV in 1s (P=0.049) values and third day partial arterial oxygen pressure (P=0.011) and Hct (P=0.011) values were lower in on-pump group. Mean extubation, duration in postoperative suit and hospital discharge times, mean blood loss were not statistically significant between groups postoperatively.

CONCLUSION

Pulmonary functions and arterial blood gases were not improved in off-pump patients when compared with on-pump patients. Patients going to be surgically revascularized should not be altered to off-pump surgery merely with the hope of improving respiratory functions with off-pump technique. As the postoperative stay times at surgical theatre and hospital is not different and the extubation times were similar, early discharge of patients with off-pump surgery cannot be related merely to better preservation of respiratory functions.

Systematic organ protection in coronary artery surgery with or without cardiopulmonary bypass

Coronary artery bypass grafting with cardiopulmonary bypass (CPB) is known to be associated with a systemic inflammatory response, which contributes to the development of postoperative complications including multiple organ dysfunction. Off-pump coronary surgery has been shown to attenuate the inflammatory injury compared to the conventional approach, thereby reducing the incidence of postoperative cardiopulmonary, renal, or neurological dysfunction. It is believed that off-pump experience may greatly impact on improving the outcome of coronary surgery in certain high-risk patients. Moreover, a better understanding of the underlying mechanism would also help to improve our current CPB management. Accumulating evidence to date indicates that a balance between pro- and antiinflammatory responses is crucial in limiting the extent of such systemic inflammatory injury following surgical myocardial revascularization.

Pulmonary dysfunction after cardiac surgery

Postoperative lung injury is one of the most frequent complications of cardiac surgery that impacts significantly on health-care expenditures and largely has been believed to result from the use of cardiopulmonary bypass (CPB). However, recent comparative studies between conventional and off-pump coronary artery bypass grafting have indicated that CPB itself may not be the major contributor to the development of postoperative pulmonary dysfunction. In our study, we review the associated physiologic, biochemical, and histologic changes, with particular reference to the current understanding of underlying mechanisms. Intraoperative modifications aiming at limiting lung injury are discussed. The potential benefits of maintaining ventilation and pulmonary artery perfusion during CPB warrant further investigation.

Off-pump coronary artery bypass grafting decreases risk-adjusted mortality and morbidity

BACKGROUND

The purpose of this study was to determine whether coronary artery bypass grafting without cardiopulmonary bypass (off-pump CABG) decreases risk-adjusted operative death and major complications after coronary artery bypass grafting in selected patients.

METHODS

Using The Society of Thoracic Surgeons (STS) National Adult Cardiac Surgery Database, procedural outcomes were compared for conventional and off-pump CABG procedures from January 1, 1998, through December 31, 1999. Mortality and major complications were examined, both as unadjusted rates and after adjusting for known base line patient risk factors.

RESULTS

A total of 126 experienced centers performed 118,140 total CABG procedures. The number of off-pump CABG cases was 11,717 cases (9.9% of total cases). The use of an off-pump procedure was associated with a decrease in risk-adjusted operative mortality from 2.9% with conventional CABG to 2.3% in the off-pump group (p < 0.001). The use of an off-pump procedure decreased the risk-adjusted major complication rate from 14.15% with conventional CABG to 10.62% in the off-pump group (p < 0.0001). Patients receiving off-pump procedures were less likely to die (adjusted odds ratio 0.81, 95% CI 0.70 to 0.91) and less likely to have major complications (adjusted odds ratio 0.77, 95% CI 0.72 to 0.82).

CONCLUSIONS

Off-pump CABG is associated with decreased mortality and morbidity after coronary artery bypass grafting. Off-pump CABG may prove superior to conventional CABG in appropriately selected patients.

Postoperative intensive care in cardiac surgery

Postoperative intensive care in cardiac surgery is a growing area, fuelled by the increase in the number of cardiac surgical procedures performed. An increase in the number of patients has resulted in increased resource utilization. Much of the recent research in this field is concerned with the early extubation of cardiac surgical patients, reducing the length of stay in the intensive care unit and predicting which patients will have delayed extubation and a prolonged length of stay. A number of recent studies have been published advocating 'off pump' cardiac surgery as a way of reducing the physiological insult of cardiopulmonary bypass and thereby improving the postoperative course. There is still insufficient evidence that this approach reduces morbidity and intensive care unit length of stay in multi-vessel off-pump coronary artery bypass surgery. The traditional design of post-cardiac surgical intensive care units and high dependency units has also recently been challenged. More flexible integrated units improve cost control and are more suited to modern cardiac surgery.