Retrospective Derivation and Validation of an Automated Electronic Search Algorithm to Identify Post Operative Cardiovascular and Thromboembolic Complications

BACKGROUND

With increasing numbers of hospitals adopting electronic medical records, electronic search algorithms for identifying postoperative complications can be invaluable tools to expedite data abstraction and clinical research to improve patient outcomes.

OBJECTIVES

To derive and validate an electronic search algorithm to identify postoperative thromboembolic and cardiovascular complications such as deep venous thrombosis, pulmonary embolism, or myocardial infarction within 30 days of total hip or knee arthroplasty.

METHODS

A total of 34 517 patients undergoing total hip or knee arthroplasty between January 1, 1996 and December 31, 2013 were identified. Using a derivation cohort of 418 patients, several iterations of a free-text electronic search were developed and refined for each complication. Subsequently, the automated search algorithm was validated on an independent cohort of 2 857 patients, and the sensitivity and specificities were compared to the results of manual chart review.

RESULTS

In the final derivation subset, the automated search algorithm achieved a sensitivity of 91% and specificity of 85% for deep vein thrombosis, a sensitivity of 96% and specificity of 100% for pulmonary embolism, and a sensitivity of 100% and specificity of 95% for myocardial infarction. When applied to the validation cohort, the search algorithm achieved a sensitivity of 97% and specificity of 99% for deep vein thrombosis, a sensitivity of 97% and specificity of 100% for pulmonary embolism, and a sensitivity of 100% and specificity of 99% for myocardial infarction.

CONCLUSIONS

The derivation and validation of an electronic search strategy can accelerate the data abstraction process for research, quality improvement, and enhancement of patient care, while maintaining superb reliability compared to manual review.

Falls and major orthopaedic surgery with peripheral nerve blockade: a systematic review and meta-analysis

The objective of this systematic review with meta-analysis was to determine the risk for falls after major orthopaedic surgery with peripheral nerve blockade. Electronic databases from inception through January 2012 were searched. Eligible studies evaluated falls after peripheral nerve blockade in adult patients undergoing major lower extremity orthopaedic surgery. Independent reviewers working in duplicate extracted study characteristics, validity, and outcomes data. The Peto odds ratio (OR) with 95% confidence intervals (CIs) were estimated from each study that compared continuous lumbar plexus blockade with non-continuous blockade or no blockade using a fixed effects model. Ten studies (4014 patients) evaluated the number of falls as an outcome. Five studies did not contain comparison groups. The meta-analysis of five studies [four randomized controlled trials (RCTs) and one cohort] compared continuous lumbar plexus blockade (631 patients) with non-continuous blockade or no blockade (964 patients). Fourteen falls occurred in the continuous lumbar plexus block group when compared with five falls within the non-continuous block or no block group (attributable risk 1.7%; number needed to harm 59). Continuous lumbar plexus blockade was associated with a statistically significant increase in the risk for falls [Peto OR 3.85; 95% CI (1.52, 9.72); P=0.005; I(2)=0%]. Evidence was low (cohort) to high (RCTs) quality. Continuous lumbar plexus blockade in adult patients undergoing major lower extremity orthopaedic surgery increases the risk for postoperative falls compared with non-continuous blockade or no blockade. However, attributable risk was not outside the expected probability of postoperative falls after orthopaedic surgery.

Synaptic vesicle pools at diaphragm neuromuscular junctions vary with motoneuron soma, not axon terminal, inactivity

Both spinal hemisection (SH) at C2 and tetrodotoxin (TTX) phrenic nerve blockade result in diaphragm muscle paralysis and inactivity of the phrenic axon terminals. However, phrenic motoneuron somata are inactive with SH but remain active with TTX phrenic nerve blockade. Neuromuscular transmission failure with repeated activation decreases following SH and increases following TTX phrenic nerve blockade, suggesting that matching (or mismatching) of somal and synaptic inactivities of phrenic motoneurons differentially regulates synaptic vesicle pools at diaphragm neuromuscular junctions. At individual type-identified rat diaphragm presynaptic terminals, the size of the releasable pool of synaptic vesicles was analyzed by fluorescence confocal microscopy of N-(3-triethylammoniumpropyl)-4-(6-(4-(diethylamino)phenyl)hexatrienyl) pyridinium dibromide (FM4-64) uptake and synaptic vesicle density at active zones was determined using transmission electron microscopy. After 14 days of SH and TTX-induced diaphragm muscle inactivity, neuromuscular junction size was not different at type I or IIa fibers, but increased at type IIx and/or IIb fibers (by 51% in SH and 35% in TTX) compared with control. With SH, synaptic vesicle pool size and density increased at presynaptic terminals innervating type I or IIa fibers (17 and 63%, respectively; P<0.001) and type IIx and/or IIb fibers (41 and 31%, respectively; P<0.001) when compared with controls. Following TTX, synaptic vesicle pool size and density decreased by 64 and 17%, respectively, at presynaptic terminals innervating type I or IIa fibers, and by 50 and 36%, respectively, at type IIx and/or IIb fibers (P<0.001, for all comparisons). Thus, matching motoneuron soma and axon terminal inactivity (SH) increases the size and density of releasable synaptic vesicle pools at adult rat diaphragm neuromuscular junctions. Mismatching motoneuron soma and axon terminal inactivities (TTX) results in converse presynaptic adaptations. Inactivity-induced neuromuscular plasticity reflects specific adaptations in the size and density of synaptic vesicle pools that depend on motoneuron soma rather than axon terminal (or muscle fiber) inactivity.

Mechanism of endothelial dysfunction in apolipoprotein E-deficient mice

Endothelium-dependent relaxations mediated by NO are impaired in a mouse model of human atherosclerosis. Our objective was to characterize the mechanisms underlying endothelial dysfunction in aortas of apolipoprotein E (apoE)-deficient mice, treated for 26 to 29 weeks with a lipid-rich Western-type diet. Aortic rings from apoE-deficient mice showed impaired endothelium-dependent relaxations to acetylcholine (10(-)(9) to 10(-)(5) mol/L) and Ca(2+) ionophore (10(-)(9) to 10(-)(6) mol/L) and endothelium-independent relaxations to diethylammonium (Z)-1-(N,N-diethylamino)diazen-1-ium-1,2-diolate (DEA-NONOate, 10(-)(10) to 10(-)(5) mol/L) compared with aortic rings from C57BL/6J mice (P<0.05). By use of confocal microscopy of an oxidative fluorescent probe (dihydroethidium), increased superoxide anion (O(2)(-)) production was demonstrated throughout the aortic wall but mainly in smooth muscle cells of apoE-deficient mice. CuZn-superoxide dismutase (SOD) and Mn-SOD protein expressions were unaltered in the aorta exposed to hypercholesterolemia. A cell-permeable SOD mimetic, Mn(III) tetra(4-benzoic acid) porphyrin chloride (10(-)(5) mol/L), reduced O(2)(-) production and partially normalized relaxations to acetylcholine and DEA-NONOate in apoE-deficient mice (P<0.05). [(14)C]L-Citrulline assay showed a decrease of Ca(2+)-dependent NOS activity in aortas from apoE-deficient mice compared with C57BL/6J mice (P<0.05), whereas NO synthase protein expression was unchanged. In addition, cGMP levels were significantly reduced in the aortas of apoE-deficient mice (P<0.05). Our results demonstrate that in apoE-deficient mice on a Western-type fat diet, impairment of endothelial function is caused by increased production of O(2)(-) and reduced endothelial NO synthase enzyme activity. Thus, chemical inactivation of NO with O(2)(-) and reduced biosynthesis of NO are key mechanisms responsible for endothelial dysfunction in aortas of atherosclerotic apoE-deficient mice.

Phrenic motoneuron morphology during rapid diaphragm muscle growth

In the adult rat, there is a general correspondence between the sizes of motoneurons, motor units, and muscle fibers that has particular functional importance in motor control. During early postnatal development, after the establishment of singular innervation, there is rapid growth of diaphragm muscle (Dia(m)) fibers. In the present study, the association between Dia(m) fiber growth and changes in phrenic motoneuron size (both somal and dendritic) was evaluated from postnatal day 21 (D21) to adulthood. Phrenic motoneurons were retrogradely labeled with fluorescent tetramethylrhodamine dextran (3,000 MW), and motoneuron somal volumes and surface areas were measured using three-dimensional confocal microscopy. In separate animals, phrenic motoneurons retrogradely labeled with choleratoxin B-fragment were visualized using immunocytochemistry, and dendritic arborization was analyzed by camera lucida. Between D21 and adulthood, Dia(m) fiber cross-sectional area increased by approximately 164% overall, with the growth of type II fibers being disproportionate to that of type I fibers. There was also substantial growth of phrenic motoneurons ( approximately 360% increase in total surface area), during this same period, that was primarily attributable to an expansion of dendritic surface area. Comparison of the distribution of phrenic motoneuron surface areas between D21 and adults suggests the establishment of a bimodal distribution that may have functional significance for motor unit recruitment in the adult rat.

Regional differences in serotonergic input to canine parasternal intercostal motoneurons

There is a mediolateral gradient in activation of the parasternal intercostal (PI) muscle during inspiration. In the present study, we tested the hypotheses that serotonergic [5-hydroxytryptamine (5-HT)] input from descending central drive and/or intrinsic size-related properties of PI motoneurons leads to the differential activation of PI muscles. In dogs, PI motoneurons innervating the medial and lateral regions of the PI muscles at the T(3)-T(5) interspaces were retrogradely labeled by intramuscular injection of cholera toxin B subunit. After a 10-day survival period, PI motoneurons and 5-HT terminals were visualized by using immunohistochemistry and confocal imaging. There were no differences in motoneuron morphology among motoneurons innervating the medial and lateral regions of the PI muscle. However, the number of 5-HT terminals and the 5-HT terminal density (normalized for surface area) were greater in motoneurons innervating the medial region of the PI muscle compared with the lateral region. These results suggest that differences in distribution of 5-HT input may contribute to regional differences in PI muscle activation during inspiration and that differences in PI motoneuron recruitment do not relate to size.