Isolated Human Pulmonary Artery Structure and Function Pre- and Post-Cardiopulmonary Bypass Surgery.

BACKGROUND: Pulmonary dysfunction is a known complication after cardiac surgery using cardiopulmonary bypass, ranging from subclinical functional changes to prolonged postoperative ventilation, acute lung injury, and acute respiratory distress syndrome. Whether human pulmonary arterial function is compromised is unknown. The aim of the present study was to compare the structure and function of isolated and cannulated human pulmonary arteries obtained from lung biopsies after the chest was opened (pre-cardiopulmonary bypass) to those obtained at the end of cardiopulmonary bypass (post-cardiopulmonary bypass) from patients undergoing coronary artery bypass graft surgery. METHODS AND RESULTS: Pre- and post-cardiopulmonary bypass lung biopsies were received from 12 patients undergoing elective surgery. Intralobular small arteries were dissected, cannulated, pressurized, and imaged using confocal microscopy. Functionally, the thromboxane mimetic U46619 produced concentration-dependent vasoconstriction in 100% and 75% of pre- and post-cardiopulmonary bypass arteries, respectively. The endothelium-dependent agonist bradykinin stimulated vasodilation in 45% and 33% of arteries pre- and post-cardiopulmonary bypass, respectively. Structurally, in most arteries smooth muscle cells aligned circumferentially; live cell viability revealed that although 100% of smooth muscle and 90% of endothelial cells from pre-cardiopulmonary bypass biopsies had intact membranes and were considered viable, only 60% and 58%, respectively, were viable from post-cardiopulmonary bypass biopsies. CONCLUSIONS: We successfully investigated isolated pulmonary artery structure and function in fresh lung biopsies from patients undergoing heart surgery. Pulmonary artery contractile tone and endothelium-dependent dilation were significantly reduced in post-cardiopulmonary bypass biopsies. The decreased functional responses were associated with reduced cell viability. CLINICAL TRIAL REGISTRATION: URL: http://www.isrctn.com/ISRCTN34428459. Unique identifier: ISRCTN 34428459.

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.

Should we consider beating-heart on-pump coronary artery bypass grafting over conventional cardioplegic arrest to improve postoperative outcomes in selected patients?

A best evidence topic in cardiac surgery was written according to a structured protocol. The question addressed was whether beating-heart on-pump coronary artery bypass grafting (BH-ONCAB) offered superior mortality and morbidity outcomes when compared with conventional on-pump coronary artery bypass grafting (C-ONCAB). Morbidity outcomes consisted of renal failure, stroke (transient or permanent), myocardial infarction, angina, congestive cardiac failure, reintervention and arrhythmias. Best evidence papers investigating BH-ONCAB versus C-ONCAB were considered. Where data were duplicated, the more credible evidence-based and recently published study was included. Two hundred and thirty-one papers were found using the reported search, of which 11 represented the best evidence to answer the clinical question. Two were prospective randomized controlled trials and the remaining 10 observational studies, of which one was propensity-matched. The authors, journal, date and country of publication, patient group studied, study type, relevant outcomes and results of these papers are tabulated. Five of these studies demonstrated significantly improved mortality following BH-ONCAB; however, one study exhibited better survival after C-ONCAB. Notably, this study incorporated BH-ONCAB patients with significantly more haemodynamic instability, thus possibly explaining the worse mortality outcomes. In terms of morbidity, a slightly more mixed picture is drawn. Five studies report morbidity in favour of BH-ONCAB, whereas three studies include individual outcomes favouring C-ONCAB. The remaining studies showed equivalent mortality and morbidity data. In summary, the results presented here suggest that BH-ONCAB may improve survival following coronary artery bypass surgery. A key observation is that the greatest benefits of BH-ONCAB appear to be in studies including patients with considerably higher risk characteristics at the time of surgery (haemodialysis, end-stage coronary artery disease, emergency surgery, low ejection fraction). There are limitations of the current evidence presented. Only two studies were randomized controlled trials. There was variability in sample size, selection criteria and preoperative risk profiles between the studies. The studies span many years, and the outcomes may have been affected by evolving technologies and differing patient profiles between these periods.

Effect of adding postoperative noninvasive ventilation to usual care to prevent pulmonary complications in patients undergoing coronary artery bypass grafting: a randomized controlled trial.

OBJECTIVE: We compared the efficacy of noninvasive ventilation with bilevel positive airway pressure added to usual care versus usual care alone in patients undergoing coronary artery bypass grafting. METHODS: We performed a 2-group, parallel, randomized controlled trial. The primary outcome was time until fit for discharge. Secondary outcomes were partial pressure of carbon dioxide, forced expiratory volume in 1 second, atelectasis, adverse events, duration of intensive care stay, and actual postoperative stay. RESULTS: A total of 129 patients were randomly allocated to bilevel positive airway pressure (66) or usual care (63). Three patients allocated to bilevel positive airway pressure withdrew. The median duration of bilevel positive airway pressure was 16 hours (interquartile range, 11-19). The median duration of hospital stay until fit for discharge was 5 days for the bilevel positive airway pressure group (interquartile range, 4-6) and 6 days for the usual care group (interquartile range, 5-7; hazard ratio, 1.68; 95% confidence interval, 1.08-2.31; P = .019). There was no significant difference in duration of intensive care, actual postoperative stay, and mean percentage of predicted forced expiratory volume in 1 second on day 3. Mean partial pressure of carbon dioxide was significantly reduced 1 hour after bilevel positive airway pressure application, but there was no overall difference between the groups up to 24 hours. Basal atelectasis occurred in 15 patients (24%) in the usual care group and 2 patients (3%) in the bilevel positive airway pressure group. Overall, 30% of patients in the bilevel positive airway pressure group experienced an adverse event compared with 59% in the usual care group. CONCLUSIONS: Among patients undergoing elective coronary artery bypass grafting, the use of bilevel positive airway pressure at extubation reduced the recovery time. Supported by trained staff, more than 75% of all patients allocated to bilevel positive airway pressure tolerated it for more than 10 hours.

Surgical management of chylopericardium and chylothorax in a patient with Behçet's disease.

Behçet's syndrome is a chronic multisystem inflammatory disease characterised classically by recurrent oral and genital ulcers with ocular lesions. It can affect blood vessels of all sizes, but involves veins more commonly than arterie. The presence of chylothorax in Behçet's syndrome is rare, with only a few cases cited in the literature. The most likely pathogenesis is SVC thrombosis with obstruction of the orifice of the thoracic duct resulting in leakage of chyle from the pleural lymphatics into the pleural space. The majority of the previously reported cases were managed medically without surgical intervention. We believe that this report describes the first use of surgery to ligate the thoracic duct and create a pericardial window in a Behçet's syndrome with chylothorax and chylopericardium.