Priyadharshanan Ariyaratnam

Risk factors and mortality associated with deep sternal wound infections following coronary bypass surgery with or without concomitant procedures in a UK population: a basis for a new risk model?

Deep sternal wound infection (DSWI) is a rare but serious complication following coronary artery bypass surgery. Our study investigates the risk factors and mortality associated with DSWI with other risk models for DSWI. Data was collected prospectively on 7602 patients undergoing coronary artery bypass grafting±concomitant surgery between April 1999 and September 2009 including DSWI. All 13 Society for Thoracic Surgeons (STS) risk scoring variables were assessed using logistic regression in relation to developing DSWI. The STS risk scores were evaluated using the area under the receiver operating curve. A total of 44 (0.59%) patients developed DSWI. These patients had a higher mortality (9.1%) than patients without DSWI (2.6%) (P=0.03). The mean preoperative and combined STS scores were significantly higher in the DSWI patient group compared to the non-DSWI group (9.46±4.30 and 8.76±3.86 vs. 7.07±4.25 and 6.51±4.11, P=0.0003 and P=0.0005, respectively). Logistic regression identified age [odds ratio (OR)=1.055], body mass index (OR=1.076), diabetes (OR=2.00) and chronic lung disease (OR=2.47) as the significant independent determinants of DSWI from the variables considered. Mortality rates and mean STS scores are higher in patients requiring re-opening for DSWI. Not all the STS risk factors were predictors of DSWI in our population.

Hydrogen sulphide vasodilates human pulmonary arteries: a possible role in pulmonary hypertension?

INTRODUCTION Acute rises in pulmonary artery pressures are associated with a significant mortality and morbidity due to the significant strain on the right ventricle. Although hydrogen sulphide (H2S) has been studied for its potential role in the systemic circulation, little is known of its effects on the pulmonary circulation in humans. We studied the effect of H2S at both the human isolated pulmonary arterial level as well as the human isolated perfused lung level. METHODS Human lobar pulmonary artery rings (n=12) and lobes (n=3) were obtained from resections for patients with bronchial carcinoma. Pre-constricted fresh rings were mounted in organ baths containing normoxic Krebs solution and subsequently exposed to hydrogen sulphide whilst tension was recorded. Isolated perfused human lung models consisted of lobes ventilated via a bronchial cannula and perfused with Krebs via a pulmonary artery cannula; hydrogen sulphide was added to the perfusate and the resulting pulmonary artery and bronchial pressures were recorded. RESULTS We found that 500μM H2S caused a mean dilation of 42.3% (±5.4) from the pre-constricted tension (p<0.005) in isolated arterial rings. In addition, 500μM H2S caused a 17.73% (3.52) reduction in pulmonary artery pressures (p<0.05). Furthermore, we found that 500μM H2S caused a 14.9% (6.01) reduction in bronchial airway pressures (p<0.05). CONCLUSIONS We have shown that H2S is a potent vasodilator of human pulmonary arteries and is a significant anti-hypertensive for pulmonary artery pressures. Our results indicate that this therapeutic potential should be further evaluated in clinical trials.

Test performance of PET-CT for mediastinal lymph node staging of pulmonary carcinoid tumours

Positron emission tomography-CT (PET-CT) is one of the initial mediastinal staging modality for non-small cell lung cancer; however, the clinical utility in carcinoid tumours is uncertain. We sought to determine the test performance of PET-CT for mediastinal lymph node staging of pulmonary carcinoid tumours. We collated data from seven institutions, performing a retrospective search on pathological databases for a consecutive series of patients who underwent thoracic surgery (with lymph nodal dissection) for carcinoid tumours with preoperative PET-CT staging. PET-CT results were compared with the reference standard of pathologic results obtained from lymph node dissection and test performance reported using sensitivity and specificity. From November 1999 to January 2013, 247 patients from seven institutions underwent surgery for carcinoid tumours with a corresponding preoperative PET-CT scan. The mean age of the patients was 61 (SD 15, range 73) and 84 were male patients (34%). The pathologic subtype was typical carcinoid in 217 patients (88%) and atypical carcinoid in 30 patients (12%). Results from lymph node dissection were obtained in 207 patients. The calculated sensitivity and specificity of PET-CT to identify mediastinal lymph node disease was 33% (95% CI 4% to 78%) and 94% (95% CI 89% to 97%), respectively. Our results indicate that PET-CT has a poor sensitivity but good specificity to detect the presence of mediastinal lymph node metastases in pulmonary carcinoid tumours. Mediastinal lymph node metastases cannot be ruled out with negative PET-CT uptake, and if the absence of mediastinal lymph node disease is a prerequisite for directing management, tissue sampling should be undertaken.

Hypoxic Pulmonary Vasoconstriction in Humans

Hypoxic pulmonary vasoconstriction is the elegant theory put forward more than six decades ago to explain regional variations in perfusion within the lung in certain animal species in response to localised restrictions in oxygenation. Although considerable progress has been made to describe the phenomenon at the macroscopic level and explain it at the microscopic level, we are far from a universal agreement about the process in humans. This review attempts to highlight some of the important evidence bases of hypoxic pulmonary vasoconstriction in humans and the significant gaps in our knowledge that would need bridging.

Complex aortic surgery in a regional center in the United Kingdom. Should the United Kingdom now adopt a United States–style supercenter model?

BACKGROUND The United States has established aortic supercenters, which have demonstrated clear improvements in the short-term and long-term outcomes after surgery on the thoracic aorta. This model of care does not exist in the United Kingdom. We have looked at our recent experience of emergency and elective thoracic aortic surgery and describe and compare our operative outcomes and 10-year survival with other regional centers and supercenters worldwide. METHODS This was a retrospective analysis of data collected prospectively from our cardiac database on patients who underwent surgery on the thoracic aorta (n=318) between November 1999 and November 2012. The outcome measures were adjusted operative mortality, postoperative complications, and long-term survival. RESULTS Type A dissection was carried out on 23.90% of the patients and 76.10% had surgery on the aortic root and thoracic aorta for nondissection. The mean age of the patients was 62.21±14.1 years. The mean logistic EuroSCORE was 26 in the dissection group and 19 in the nondissection group. Hospital mortality was significantly greater (P<.05) in the dissection group compared with the nondissection group (23.7% vs 12.8%). Survival after dissection and nondissection surgery was 66.3%±5.6% versus 77.4%±2.8%, respectively, at 3 years, 63.9%±5.9% versus 71.8%±3.2% at 5 years, and 53.7%±7.4% versus 47.1%±6.0% at 10 years. CONCLUSIONS Our outcomes are comparable with other regional centers worldwide; however, they are not as good as those reported from the aortic supercenters. There should be continued impetus regarding the establishment of thoracic aortic surgery guidelines and specialist aortic centers in the United Kingdom.

Extra-corporeal membrane oxygenation for the post-cardiotomy patient

Extra-corporeal membrane oxygenation remains the last resort in keeping patients alive in those with profound cardiogenic shock following percutaneous interventions or open surgery on the heart. No guidelines exist on the management of patients on such a device despite a high mortality. We attempt to highlight some universal principles that would be relevant to the current practice of those exposed to this challenging field.

Long-term survival from 801 adjunctive coronary endarterectomies in diffuse coronary artery disease

OBJECTIVES The role of coronary endarterectomy (CE) in modern cardiac surgery has been an extant debate as coronary artery bypass grafting (CABG) has advanced. However, as cardiac surgeons are being referred ever more complex coronary disease for surgical correction, adjunctive strategies may need re-evaluation. The long-term results of CE are largely unknown. We present the longest cohort follow-up in a single institution looking at our 20-year experience of CEs employed as an adjunct to CABG in diffuse coronary artery disease. METHODS We performed retrospective analysis of data collected prospectively on 801 patients undergoing CEs between February 1988 and September 2010 by a single surgeon using a standard open hydrodissection technique. We looked at patient demographics, characteristics of the vessels subjected to endarterectomy and predictors of long-term survival within this surgical group using Coxs regression analysis. RESULTS The mean age was 63.2 (±9.6) years. The mean number of coronary arteries undergoing endarterectomy was 1.16 (±0.4) per patient. Of these, 63.7% were performed on the right coronary artery (n = 558) and 32.3% on the left anterior descending artery (n = 283). The operative mortality was 2.62% (n = 21). The median survival time was 16.67 years (95% confidence interval 15.14-18.19 years). The significant predictors of survival (P < 0.05) were a lower age at surgery, a lower EuroSCORE I, the absence of peripheral vascular disease and shorter bypass times. CONCLUSION This significant long-term survival demonstrates that CE can be an attractive adjunct to CABG in otherwise inoperable coronary artery disease.

Validation of the Intensive Care National Audit and Research Centre Scoring System in a UK Adult Cardiac Surgery Population

OBJECTIVE The Intensive Care National Audit and Research Centre (ICNARC) scoring system was conceived in 2007, utilizing 12 physiologic variables taken from the first 24 hours of adult admissions to the general intensive care unit (ICU) to predict in-hospital mortality. The authors aimed to evaluate the ICNARC score in predicting mortality in cardiac surgical patients compared to established cardiac risk models such as logistic EuroSCORE as well as to the Acute Physiology and Chronic Health Evaluation (APACHE) II. DESIGN Retrospective analysis of data collected prospectively. SETTING Single-center study in a cardiac intensive care in a regional cardiothoracic center. PARTICIPANTS Patients undergoing cardiac surgery between January 2010 and June 2012. METHODS A total of 1,646 patients were scored preoperatively using the logistic EuroSCORE and postoperatively using ICNARC and APACHE II. Data for comparison of scoring systems are presented as area under the receiver operating characteristic curve. MEASUREMENTS AND MAIN RESULTS The mean age at surgery was 67 years±10.1. The mortality from all cardiac surgery was 3.2%. The mean logistic EuroSCORE was 7.31±10.13, the mean ICNARC score was 13.42±5.055, while the mean APACHE II score was 6.32±7.731. The c-indices for logistic EuroSCORE, ICNARC, and APACHE II were 0.801, 0.847 and 0.648, respectively. CONCLUSION The authors have, for the first time, validated the ICNARC score as a useful predictor of postoperative mortality in adult cardiac surgical patients. This could have implications for postoperative management, focusing the utilization of resources as well as a method to measure and compare performance in the cardiothoracic ICU.

Hyperoxic Vasoconstriction of Human Pulmonary Arteries: A Novel Insight into Acute Ventricular Septal Defects

Objectives. Acute rises in pulmonary artery pressures following postinfarction ventricular septal defects present a challenge. We hypothesised that the abnormally high oxygen content exposure to the pulmonary arteries may be a factor. We investigated the contractile responses of human pulmonary arteries to changes in oxygen tension. Methods. Isometric tension was measured in large and medium sized pulmonary artery rings obtained from lung resections for patients with bronchial carcinoma (n = 30). Fresh rings were mounted in organ baths bubbled under basal conditions with hyperoxic or normoxic gas mixes and the gas tensions varied during the experiment. We studied whether voltage-gated calcium channels and nitric oxide signalling had any role in responses to oxygen changes. Results. Hypoxia caused a net mean relaxation of 18.1% ± 15.5 (P < 0.005) from hyperoxia. Subsequent hyperoxia caused a contraction of 19.2% ± 13.5 (P < 0.005). Arteries maintained in normoxia responded to hyperoxia with a mean constriction of 14.8% ± 3.9 (P < 0.005). Nifedipine inhibited the vasoconstrictive response (P < 0.05) whilst L-NAME had no effect on any hypoxic vasodilatory response. Conclusions. We demonstrate that hyperoxia leads to vasoconstriction in human pulmonary arteries. The mechanism appears to be dependent on voltage-gated calcium channels. Hyperoxic vasoconstriction may contribute to acute rises in pulmonary artery pressures.

Long-term prognosis and a prediction model for acute bowel ischaemia following cardiac surgery

OBJECTIVES Bowel ischaemia following cardiac surgery is associated with a high postoperative mortality. No scoring system exists as yet to predict this complication following surgery. In addition, the long-term survival is not known. We sought to evaluate in-hospital outcomes and long-term outcomes in bowel ischaemia following cardiac surgery. We also sought to devise a simple risk prediction model for this catastrophic entity. METHODS This was a retrospective study of data entered prospectively into our cardiac surgical database between July 1999 and May 2014. We compared the short- and long-term outcomes of patients who developed bowel ischaemia following cardiac surgery with those who did not develop bowel ischaemia using propensity-matched analysis. We developed a prediction model for bowel ischaemia from logistic regression. RESULTS In total, 13 853 patients underwent cardiac surgery. Of these, 85 had confirmed bowel ischaemia following surgery. The in-hospital mortality rate for those with bowel ischaemia was 60%, while in those without bowel ischaemia, the mortality rate was 3% (P < 0.0001). In those bowel ischaemia patients who had a laparotomy for corrective surgery, the in-hospital mortality was significantly less compared with those who did not have a laparotomy (39.2 vs 91.2%, P < 0.0001). The long-term survival for bowel ischaemia at 2, 6 and 10 years was 35% (±5), 31% (±5) and 26% (+/6), respectively. Multivariable analysis revealed that advanced age at surgery, peripheral vascular disease, intra-aortic balloon pump usage, NYHA IV and postoperative atrial fibrillation were the significant (P < 0.005) determinants of developing postoperative bowel ischaemia. We developed a model to predict bowel ischaemia and validated it within our population (c-index = 0.781). CONCLUSIONS We have shown that whilst bowel ischaemia carries a higher short-term mortality, the long-term mortality is not significantly greater for those few who survive to discharge. We have developed a simple prediction model to identify those at high risk of developing bowel ischaemia following cardiac surgery in order to optimize perioperative strategies in future.