{'fraction_non_alphanumeric': 0.02569934045940414, 'fraction_numerical': 0.005458267000227428, 'mean_word_length': 5.211864406779661, 'pattern_counts': {'":': 0, '<': 0, '<?xml version=': 0, '>': 0, 'https://': 0, 'lorem ipsum': 0, 'www.': 0, 'xml': 0}, 'pii_count': 0, 'substrings_counts': 0, 'word_list_counts': {'cursed_substrings.json': 0, 'profanity_word_list.json': 0, 'sexual_word_list.json': 0, 'zh_pornsignals.json': 0}}
I Preoperative plasma brain natriuretic peptide concentrations : do they improve our care of high-risk non-cardiac surgical patients ?

There is presently much interest in the preoperative identification of high-risk patients undergoing major surgery— with the aim of adopting management strategies which may reduce postoperative morbidity and mortality. In the non-cardiac surgical patient, data for the UK suggest that there may be up to 8000 cardiovascular deaths per year for 5 million surgical procedures performed, with an incidence of 10 times that with regard to morbidity (myocardial infarction, congestive cardiac failure, malignant arrhythmias, and cardiac arrest). The major pathological disorder responsible for these adverse outcomes is ischaemic heart disease, either overt or covert, secondary to atherosclerosis. We, and others, have recently reviewed the role of biomarkers in the identification of at-risk cardiac patients. 4 For a test to be useful as a biomarker, it should to be able to differentiate between the ‘healthy’ and the ‘compromised’ patient. In epidemiological terms, it needs to have a high sensitivity (probability that the biomarker will be raised and correctly identify high risk for a complication) and high specificity (such that the biomarker is appropriately low or absent when the risk of complication is absent). For the majority of tests, there is a balance between these two indices; the performance of a test can be further described in terms of a receiver operating characteristic (ROC) curve, which is essentially a graphical plot of sensitivity against 1-specificity, with the inflexion of this curve usually taken as the cut-off value for the diagnostic test. Other commonly used descriptors of the utility of a test or biomarker are the positive and negative predictive values and the relative risk of an adverse event that is provided by a raised concentration of biomarker. A biomarker that has received a great deal of attention for a number of potential uses is brain (or B-type) natriuretic peptide (BNP). The natriuretic peptides comprise both the atrial and brain (or B-type) natriuretic peptides. In the human, atrial natriuretic peptide (ANP) is primarily produced by atrial myocytes, whereas BNP is produced by both atrial and ventricular myocytes, but primarily by the ventricular ones. BNP was originally identified in extracts of porcine brain. However, in man, it is produced and secreted mainly in the cardiac ventricles. BNP is secreted as the precursor pro-BNP and is cleaved to the active peptide BNP and the inactive N-terminal fragment (NT pro-BNP). The stimulus to release these peptides is myocyte stretch in association with ventricular dilation and pressure overload. The physiological effects of BNP include the augmentation of urinary volume (diuresis), sodium excretion (natriuresis), aldosterone antagonism through inhibition of the renin–angiotensin system, sympathetic autonomic nervous system inhibition, and direct antiproliferative effects on the cardiac myocytes. These effects result in relaxation of vascular smooth muscle and counteraction of hypertrophy and destruction of the myocyte sarcomere structure. Increased plasma concentrations of these peptides have been shown to be associated with hypertension, myocardial hypertrophy, arrhythmias, renal insufficiency, and cerebrally mediated salt wasting. BNP has shown utility as a diagnostic tool in the evaluation of acute dyspnoea. A blood value ,100 pg ml was thought to make a diagnosis of congestive cardiac failure unlikely, whereas a value of .500 pg ml made it highly likely. BNP has been advocated as a sensitive marker of ventricular dysfunction, with the concentration of BNP varying according to the grade of cardiac failure by the New York Heart Association (NYHA) classification; progressively increasing from Grade I to Grade IV of this scale. Furthermore, the utility of BNP as a biomarker in other settings has been assessed, including screening for preclinical disease in asymptomatic individuals. In elderly subjects (age .80 yr) with no history of cardiac disease, it has been shown that for each increase in the plasma BNP concentration of 50 pg ml, there is an associated increase in cardiac events of 1.6-fold and total mortality of 1.4-fold over a 2 yr follow-up period. When the Framingham Offspring Study Database was interrogated,