Preoperative levels of natriuretic peptides and the incidence of postoperative atrial fibrillation after noncardiac surgery: a prospective cohort study

BACKGROUND:Postoperative atrial fibrillation (POAF) is associated with clinically significant short- and long-term complications after noncardiac surgery. Our aim was to describe the incidence of clinically important POAF after noncardiac surgery and establish the prognostic value of N-terminal pro–brain-type natriuretic peptide (NT-proBNP) in this context.METHODS:The Vascular events In noncardiac Surgery patIents cOhort evaluatioN (VISION) Study was a prospective cohort study involving patients aged 45 years and older who had inpatient noncardiac surgery that was performed between August 2007 and November 2013. We determined 30-day incidence of clinically important POAF (i.e., resulting in angina, congestive heart failure, symptomatic hypotension or requiring treatment) using logistic regression models to analyze the association between preoperative NT-proBNP and POAF.RESULTS:In 37 664 patients with no history of atrial fibrillation, we found that the incidence of POAF was 1.0% (95% confidence interval [CI] 0.9%–1.1%; 369 events); 3.2% (95% CI 2.3%–4.4%) in patients undergoing major thoracic surgery, 1.3% (95% CI 1.2%–1.5%) in patients undergoing major nonthoracic surgery and 0.2% (95% CI 0.1%–0.3%) in patients undergoing low-risk surgery. In a subgroup of 9789 patients with preoperative NT-proBNP measurements, the biomarker improved the prediction of POAF risk over conventional prognostic factors (likelihood ratio test p < 0.001; fraction of new information from NT-proBNP was 16%). Compared with a reference NT-proBNP measurement set at 100 ng/L, adjusted odds ratios for the occurrence of POAF were 1.31 (95% CI 1.15–1.49) at 200 ng/L, 2.07 (95% CI 1.27–3.36) at 1500 ng/L and 2.39 (95% CI 1.26–4.51) at 3000 ng/L.INTERPRETATION:We determined that the incidence of clinically important POAF after noncardiac surgery was 1.0%. We also found that preoperative NT-proBNP levels were associated with POAF independent of established prognostic factors. Trial registration: ClinicalTrials.gov, no. {"type":"clinical-trial","attrs":{"text":"NCT00512109","term_id":"NCT00512109"}}NCT00512109

Postoperative atrial fibrillation (POAF) is the most common arrhythmia that occurs after noncardiac surgery¹ and is associated with prolonged hospital stays and an increased risk of stroke and death,^2–8 both of which raise societal costs.⁹ The reported incidence of POAF ranges from 3.7% to 21.0% in patients undergoing thoracic surgery^3,10 and from less than 0.5% to 10.0% in patients undergoing noncardiac, nonthoracic surgery (Appendix 1, Supplementary Table 1, available at www.cmaj.ca/lookup/doi/10.1503/cmaj.200840/tab-related-content).^6,11Brain-type natriuretic peptide (BNP) is a neurohormone released by cardiomyocytes in response to volume and pressure overload.¹² This biomarker has an established role in the diagnosis and management of heart failure and in predicting cardiovascular morbidity and mortality.¹³ Although natriuretic peptides have been shown to predict new-onset atrial fibrillation (AF) in the nonsurgical setting reliably,^14–18 their value in predicting POAF after noncardiac surgery is unclear.^19–21The Vascular events In non-cardiac Surgery patIents cOhort evaluatioN (VISION) Study was a prospective international cohort study involving a representative sample of adults who underwent noncardiac surgery that required an overnight hospital stay. One of the predefined objectives in VISION was to determine the incidence of new-onset, clinically important POAF. We aimed to describe the overall and surgery-specific incidence of POAF after noncardiac surgery and to investigate the association between preoperative N-terminal pro–brain-type natriuretic peptide (NT-proBNP) and POAF. We hypothesized that measurement of NT-proBNP would improve POAF risk prediction beyond conventional prognostic factors.     

A Preliminary Study of Human Calcium Metabolism Using Long-Term Whole Body Tracer Measurements

Long-term bone calcium metabolism was measured using a whole body counter apparatus and the radioisotopes calcium-47 and strontium-85. Strontium was given with calcium in a single intravenous injection in order to estimate long-term retention of calcium. Calcium-47, with a short radio-active half-life, was measured directly for 20 days, and then indirectly from strontium retention for periods up to 200 days.The standard parameters of calcium transport were measured and, as well, a new parameter, calcium accretion to the fixed bone pool. These studies were carried out on 13 subjects, six of whom were selected “normals” and seven were patients with osteoporosis. Calcium accretion to the fixed bone pool, the new index of bone formation, varied from 100 to 210 mg. of calcium daily in normal subjects and from 70 to 340 mg./day in patients with osteoporosis. These values are one-third of those for the accretion to the total bone pool, the previously reported bone formation rate.     

The Gut Microbiota–Brain Axis Expands Neurologic Function: A Nervous Rapport

Does exploration of the gut microbiota–brain axis expand our understanding of what it means to be human? Recognition and conceptualization of a gut microbiota–brain axis challenges our study of the nervous system. Here, integrating gut microbiota–brain research into the metaorganism model is proposed. The metaorganism—an expanded, dynamic unit comprising the host and commensal organisms—asserts a radical blurring between man and microbe. The metaorganism nervous system interacts with the exterior world through microbial‐colored lenses. Ongoing studies have reported that gut microbes contribute to brain function and pathologies, even shaping higher neurological functions. How will continued collaborative efforts (e.g., between neurobiology and microbiology), including partnerships with the arts (e.g., philosophy), contribute to the knowledge of microbe‐to‐mind interactions? While this is not a systemic review, this nascent field is briefly described, highlighting ongoing challenges and recommendations for emerging gut microbiota–brain research. Also see the video abstract here https://youtu.be/lP9gOW8StXg .     

Engineered antifouling microtopographies: mapping preferential and inhibitory microenvironments for zoospore attachment

An algorithm was developed and implemented to map the locations of attached spores of Ulva linza on patterned surfaces. Using this mapping algorithm, spore preference among regions within a pattern can be detected and quantified. Settlement maps of spores on patterned topographies from several assays showed clear preferences in spore settlement. Over 94% of the spores attached within the depressed regions on the surfaces, including a surface containing pits instead of protruding features. The spores attached primarily at the intersections of several features, with over half and up to 96% of spores settling in these regions. The highest spore densities occurred at intersections where the features were most dissimilar. In contrast, the location of attached beads on the surfaces was nearly uniform across the surface. Identification of preferential attachment locations allows for the study of localized properties that influence cell behavior and aids in the development of new surfaces to control cell–surface interactions.     

Protozoan community structure in a fractal soil environment.

Protozoan abundance was quantified, and 365 protozoan species were recorded, in 150 soil samples from an upland grassland in Scotland. Across the entire size range (2-200 pm) protozoan species richness varied by a factor of two, whereas abundance increased by a factor of 20 with decreasing body size. As the soil had fractal structure, the relatively flat species curve can be explained if spatial heterogeneity determines species number--for in a fractal environment, heterogeneity will be the same at all spatial scales. Community structure appeared to approach a temporary steady-state about six days after re-hydration of dried soil. A simple model based on combining the fractal character of increasing habitat area at smaller spatial scales, with the weight-specific energy requirements of protozoa, provided theoretical curves of abundance and biovolume on body size which provide a reasonable fit to real data. We suggest two possibilities--that the apparent competence of the theoretical model is fortuitous and the product of poorly understood dynamic elements of the trophic structure in the community; or that key elements of protozoan community structure in a fractal soil environment may be largely explained in terms of habitat space and energy requirements.     

Amphiphilic triblock copolymers with PEGylated hydrocarbon structures as environmentally friendly marine antifouling and fouling-release coatings

The ideal marine antifouling (AF)/fouling-release (FR) coating should be non-toxic, while effectively either resisting the attachment of marine organisms (AF) or significantly reducing their strength of attachment (FR). Many recent studies have shown that amphiphilic polymeric materials provide a promising solution to producing such coatings due to their surface dual functionality. In this work, poly(ethylene glycol) (PEG) of different molecular weights (M_w?=?350, 550) was coupled to a saturated difunctional alkyl alcohol to generate amphiphilic surfactants (PEG-hydrocarbon-OH). The resulting macromolecules were then used as side chains to covalently modify a pre-synthesized PS₈?_K-b-P(E/B)₂₅?_K-b-PI₁₀?_K (SEBI or K3) triblock copolymer, and the final polymers were applied to glass substrata through an established multilayer surface coating technique to prepare fouling resistant coatings. The coated surfaces were characterized with AFM, XPS and NEXAFS, and evaluated in laboratory assays with two important fouling algae, Ulva linza (a green macroalga) and Navicula incerta, a biofilm-forming diatom. The results suggest that these polymer-coated surfaces undergo surface reconstruction upon changing the contact medium (polymer/air vs polymer/water), due to the preferential interfacial aggregation of the PEG segment on the surface in water. The amphiphilic polymer-coated surfaces showed promising results as both AF and FR coatings. The sample with longer PEG chain lengths (M_w?=?550?g?mol^?1) exhibited excellent properties against both algae, highlighting the importance of the chemical structures on ultimate biological performance. Besides reporting synthesis and characterization of this new type of amphiphilic surface material, this work also provides insight into the nature of PEG/hydrocarbon amphiphilic coatings, and this understanding may help in the design of future generations of fluorine-free, environmentally friendly AF/FR polymeric coatings.