BackgroundGeriatric patients undergoing hemiarthroplasty for hip fractures have unacceptably high rates of postoperative complications and mortality. Whether anesthesia type can affect the outcomes has still been inconclusive.ObjectivesWe compared general anesthesia (GA) and peripheral nerve blocks (PNBs) on postoperative complications and mortality in elderly patients with femoral neck fractures (FNF) undergoing hemiarthroplasty.Materials and methodsThis retrospective study involved data collection from an electronic database. Two hundred and seventeen patients underwent hemiarthroplasty for FNF between January 2008 and December 2012 at the Chinese People’s Liberation Army General Hospital. Data on mortality within in-hospital, 30-day, and 1-year, complications, comorbidities, blood loss and transfusion, operative time, postoperative hospital length of stay, intensive care unit admission, and hospital charge were collected and analyzed. Univariate and multivariate Cox regression analyses of all variables were used for 30-day and 1-year mortality.ResultsSeventy-two patients receiving GA and 145 receiving PNBs were eventually submitted and analyzed. Mortality was 6.9%, 14.7%, and 23.5% at in-hospital, 30-day, and 1-year, respectively postoperatively, while mortality and cardiovascular complications did not differ between the two anesthetic techniques. Preoperative comorbidities and intraoperative parameters were not statistically different except that patients receiving GA were more likely to have dementia (χ2=10.45, P=0.001). The most common complications were acute cardiovascular events, electrolyte disturbances, and delirium. Postoperative acute respiratory events and hypoxemia both were also common, but no differences were found between groups (χ2=0.68, P=0.410; χ2=3.42, P=0.065, respectively). Key factors negatively influencing mortality included: age, male gender, American Society of Anesthesiologists status, dementia, perioperative cardiovascular events and respiratory events, postoperative stroke, myocardial infarction, and hypoxia.ConclusionMortality and postoperative complications are not statistically significantly different between PNBs and GA among eldery patients undergoing hemiarthroplasty for FNF.

Dextrans with mass-average molar masses 8 . lo4 g/mol < Mw < lo8 g/mol have been studied in water by means of static and dynamic light scattering at different temperatures. Static light scattering (SLS) yields the z-average mean-square radius of gyration, (S'), and the second virial coefficient A,. It is found that the dependences of (S2)"2 and Axon the mass-average molar mass, Mw, can be well described by the power laws (S2)ih = K,. M$ and A, = KA . @). The exponent vs is independent of the temperature T, while vA decreases as Tis raised. Dynamic light scattering (DLS) yields the apparent diffusion coefficient, D , , (q, c), and the hydrodynamic radius, R,, where q is the wave vector and c the polymer concentration. For small q, a plot of D,,(q, c) versus q 2 . (S'), gives a straight line. The intercept D,(c) = D,,,(q, c) represents the centre-of-mass translational diffusion coefficient. Its dependence on the concentration, c, can be well simulated by the relation D,(c) = D,,,[1 + k,,,. c].Here, ka2 is the second hydrodynamic virial coefficient and D,, the z-average of the translational diffusion coefficient at infinite dilution. The analysis of the kD, ,-data shows that dextran molecules behave rather as interpenetrable than as non-interpenetrable spheres. The density p = (3Mw)/(NA. 4nR;) proves to be a measure for the degree of penetration; p decreases with increasing Mw, indicating that penetration becomes easier at higher molar masses.

It is important that monitoring the fatigue crack propagation in engineering. This paper studied crack growth rate with the metal magnetic memory technique. Three-point bending fatigue tests of center-cracked specimens were carried out and the normal component of magnetic field signals Hp(y) on the surface of specimens were measure by TSC-1M-4. The correlation of crack growth rate da/dN and metal magnetic memory normal signal Hp(y) was studied. The specimens, with different heat treatment, quenching and thermal refining, were tested in fatigue-testing Machine to study the influence of heat treatment on the metal magnetic memory signal Hp(y). The curve of da/dN ~ Hp(y) was built.

Crack growth rate, as an important parameter, is widely applied in crack growth evaluation and fatigue life prediction. The objective of this paper is to study crack growth rate with the metal magnetic memory (MMM) technology which is a non-destructive testing method newly developed. The correlation between crack growth rate da / dN and magnetic memory signal Hp(y) is investigated through three-point bending fatigue testing. Samples of steel X45, with different heat treatments, quenching and thermal refining, are tested in HYG fatigue machinery. The correlation curves of da / dN ~ Hp(y) are built and the characteristics of magnetic memory signal are given. The influence of heat treatment on Hp(y) is also analyzed. The crack growth rate model of X45 based on MMM signal is presented and verified.

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