Efficacy of cold renal perfusion protection for open complex aortic aneurysm repair: a meta-analysis.

BACKGROUND: Cold renal perfusion (CRP) with 4°C crystalloid fluids has been described as a method to reduce renal injury during open surgical repair of complex aortic aneurysms (cAAs) (those requiring at least a suprarenal clamp site). We performed a meta-analysis to ascertain whether CRP improves kidney-related outcomes after open surgical cAA repair. METHODS: Patients of any age or gender who had undergone open surgical repair of cAAs were included. Primary outcomes were the presence of postoperative kidney injury, the need for dialysis and mortality related to kidney injury. We compared patients who were treated with any intraoperative CRP strategy to a control population without CRP. We used a fixed-effects model to analyze derived odds ratios (ORs) and assess heterogeneity. We performed risk of bias analysis to identify potential confounding elements. RESULTS: Among the 935 studies screened, 5 primary articles met the inclusion criteria. Cold renal perfusion significantly reduced postoperative acute kidney injury (OR 0.46 [95% confidence interval 0.32-0.68], Z = 3.98, p = 0.001). Only 1 study included data for the other primary outcomes. The data were considered homogeneous, with Cochrane Q = 0.23 and I 2 of 0%. CONCLUSION: This meta-analysis showed reduced postoperative acute kidney injury with the use of CRP during open cAA repair. A prospective randomized controlled trial to perform further subgroup analysis and research the various types of CRP solutions may be warranted to identify further possible benefits.

Angiotensin-Converting Enzyme Inhibitor/Receptor Blocker, Diuretic, or Nonsteroidal Anti-inflammatory Drug Use After Major Surgery and Acute Kidney Injury: A Case-Control Study.

BACKGROUND: Acute kidney injury (AKI) is common after surgery and associated with increased mortality, costs, and lengths of hospitalization. We examined associations between angiotensin-converting enzyme inhibitor (ACEI)/angiotensin receptor blocker (ARB), diuretic, or nonsteroidal anti-inflammatory drug (NSAID) use after major surgery and AKI. MATERIALS AND METHODS: We conducted a nested case-control study of patients who underwent major cardiac, thoracic, general, or vascular surgery in Calgary, Alberta, Canada. Cases with AKI were matched on age, gender, and surgery type with up to five controls without AKI within 30-d after surgery. Adjusted odds ratios (ORs) for AKI were determined based on postoperative administration of ACEIs/ARBs, diuretics, or NSAIDs. RESULTS: Among 33,648 patients in the cohort, 2911 cases with AKI were matched to 9309 controls without AKI. Postoperative diuretic [OR = 1.96; 95% confidence interval (CI) = 1.68-2.29], but not ACEI/ARB (OR = 0.83; 95% CI = 0.72-0.95) or NSAID (OR = 1.12; 95% CI = 0.96-1.31), use was independently associated with higher odds of AKI (including stages 1 and 2/3 AKI) after all types of major surgery. There were increased adjusted odds of AKI 1 to 5 d after first exposure to diuretics and 1 d after first exposure to NSAIDs (but not after later exposures). Relationships between ACEI/ARB use and AKI varied by surgery type (p-interaction = 0.004), with lower odds of AKI observed among ACEI/ARB use after cardiac surgery (OR = 0.70; 95% CI = 0.57-0.81), but no difference after other major surgeries. CONCLUSIONS: Postoperative administration of diuretics and NSAIDs was associated with increased odds of AKI after major surgery. These findings characterize potentially modifiable medication exposures associated with AKI after surgery.

Development and initial implementation of electronic clinical decision supports for recognition and management of hospital-acquired acute kidney injury.

BACKGROUND: Acute kidney injury (AKI) is common in hospitalized patients and is associated with poor patient outcomes and high costs of care. The implementation of clinical decision support tools within electronic medical record (EMR) could improve AKI care and outcomes. While clinical decision support tools have the potential to enhance recognition and management of AKI, there is limited description in the literature of how these tools were developed and whether they meet end-user expectations. METHODS: We developed and evaluated the content, acceptability, and usability of electronic clinical decision support tools for AKI care. Multi-component tools were developed within a hospital EMR (Sunrise Clinical Manager™, Allscripts Healthcare Solutions Inc.) currently deployed in Calgary, Alberta, and included: AKI stage alerts, AKI adverse medication warnings, AKI clinical summary dashboard, and an AKI order set. The clinical decision support was developed for use by multiple healthcare providers at the time and point of care on general medical and surgical units. Functional and usability testing for the alerts and clinical summary dashboard was conducted via in-person evaluation sessions, interviews, and surveys of care providers. Formal user acceptance testing with clinical end-users, including physicians and nursing staff, was conducted to evaluate the AKI order set. RESULTS: Considerations for appropriate deployment of both non-disruptive and interruptive functions was important to gain acceptability by clinicians. Functional testing and usability surveys for the alerts and clinical summary dashboard indicated that the tools were operating as desired and 74% (17/23) of surveyed healthcare providers reported that these tools were easy to use and could be learned quickly. Over three-quarters of providers (18/23) reported that they would utilize the tools in their practice. Three-quarters of the participants (13/17) in user acceptance testing agreed that recommendations within the order set were useful. Overall, 88% (15/17) believed that the order set would improve the care and management of AKI patients. CONCLUSIONS: Development and testing of EMR-based decision support tools for AKI with clinicians led to high acceptance by clinical end-users. Subsequent implementation within clinical environments will require end-user education and engagement in system-level initiatives to use the tools to improve care.

Force-frequency relationship during fatiguing contractions of rat medial gastrocnemius muscle.

The force-frequency relationship presents the amount of force a muscle can produce as a function of the frequency of activation. During repetitive muscular contractions, fatigue and potentiation may both impact the resultant contractile response. However, both the apparent fatigue observed, and the potential for activity-dependent potentiation can be affected by the frequency of activation. Thus, we wanted to explore the effects that repetitive stimulation had on the force-frequency relationship. The force-frequency relationship of the rat medial gastrocnemius muscle was investigated during consecutive bouts of increasing fatigue with 20 to 100 Hz stimulation. Force was measured prior to the fatiguing protocol, during each of three levels of fatigue, and after 30 min of recovery. Force at each frequency was quantified relative to the pre-fatigued 100 Hz contractions, as well as the percentage reduction of force from the pre-fatigued level at a given frequency. We observed less reduction in force at low frequencies compared to high frequencies, suggesting an interplay of fatigue and potentiation, in which potentiation can "protect" against fatigue in a frequency-dependent manner. The exact mechanism of fatigue is unknown, however the substantial reduction of force at high frequency suggests a role for reduced force per cross-bridge.

Cardiac rehabilitation in people with peripheral arterial disease: A higher risk population that benefits from completion.

BACKGROUND: Peripheral arterial disease (PAD) is common in people referred for cardiac rehabilitation (CR). However, the associations between PAD diagnosis and CR attendance and mortality remain to be defined. METHODS: All patients referred to a 12-week exercise-based CR program were included. Associations between PAD diagnosis and starting CR as well as between PAD diagnosis and completing CR were measured using multivariable logistic regression. Associations between CR completion and mortality were measured using adjusted Cox proportional hazards models, and a propensity-based matching sensitivity analysis was performed. RESULTS: 23,215 patients (mean age 61.3 years; 21.6% female) were referred to CR; 1366 (5.9%) had PAD. Those with PAD were less likely to start CR (57.0% vs 68.2%, adjusted OR 0.81, 95%CI 0.72, 0.91) and complete CR if they started (70.6% vs 76.7%, adjusted OR 0.80, 95%CI 0.68, 0.94). Patients with PAD completing CR had lower exercise capacity at baseline (6.6 vs. 7.6 METs, p < 0.0001) and completion (7.5 vs 8.6 METs, p < 0.0001). There were 3510 deaths over follow-up; 10-year survival was lower in those with PAD (66.9 vs 84.5%; p < 0.0001). CR completion was associated with lower mortality for all (adjusted HR 0.62 (95%CI 0.57, 0.67)), and the magnitude of the association was independent of PAD status. CONCLUSIONS: Patients with PAD referred to CR had a higher mortality than those without, and were less likely to start and complete CR. Completion of CR was associated with improved fitness and survival for PAD patients. These data support broader use of CR by those with PAD.

Force-velocity relationship during isometric and isotonic fatiguing contractions.

Fatiguing contractions change the force-velocity relationship, but assessment of this relationship in fatigue has usually been obtained after isometric contractions. We studied fatigue caused by isometric or isotonic contractions, by assessment of the force-velocity relationship while the contractions maintaining fatigue were continued. This approach allowed determination of the force-velocity relationship during a steady condition of fatigue. We used the in situ rat medial gastrocnemius muscle, a physiologically relevant preparation. Intermittent (1/s) stimulation at 170 Hz for 100 ms resulted in decreased isometric force to ~35% of initial or decreased peak velocity of shortening in dynamic contractions to ~45% of initial. Dynamic contractions resulted in a transient initial increase in velocity, followed by a rapid decline until a reasonably steady level was maintained. Data were fit to the classic Hill equation for determination of the force-velocity relationship. Isometric and dynamic contractions resulted in similar decreases in maximal isometric force and peak power. Only Vmax was different between the types of contraction ( P < 0.005) with greater decrease in Vmax during isotonic contractions to 171.7 ± 7.3 mm/s than during isometric contractions to 208.8 mm/s. Curvature indicated by a/Po (constants from fit to Hill equation) changed from 0.45 ± 0.04 to 0.71 ± 0.11 during isometric contractions and from 0.51 ± 0.04 to 0.85 ± 0.18 during isotonic contractions. Recovery was incomplete 45 min after stopping the intermittent contractions. At this time, recovery of low-frequency isometric force was substantially less after isometric contractions, implicating force during intermittent contractions as a determining factor with this measure of fatigue. NEW & NOTEWORTHY The force-velocity relationship was captured while fatigue was maintained at a constant level during isometric and dynamic contractions. The curvature of the force-velocity relationship was less curved during fatigue than prefatigued, but within 45 min this recovered. Low-frequency fatigue persisted with greater depression of low-frequency force after isometric contractions, possibly because of higher force contractions during intermittent contractions.

A proof-of-concept in vitro study to determine if EndoAnchors can reduce gutter size in chimney graft configurations.

PURPOSE: To investigate the feasibility of using endoanchor technology to reduce chimney graft-related gutter size in a juxtarenal aneurysm model. METHODS: In silicone juxtarenal aortic aneurysm models with two sizes of branch arteries and two sizes of aorta, single chimney graft (CG) configurations were constructed using 6-mm Atrium balloon-expandable stent-grafts in association with two sizes of Gore Excluder main grafts (23 and 28.5 mm). Configurations without Aptus EndoAnchors, with suprarenal placement of EndoAnchors, and with additional infrarenal placement of EndoAnchors were investigated. A total of 12 CG configurations were scanned using 64-slice computed tomography. Gutter volume and gutter areas at the top and bottom of the sealing zone were measured with image processing software. RESULTS: The combination of supra- and infrarenal placement of endoanchors led to a reduction in gutter volume compared to unanchored configurations. The same configurations also led to a decrease in gutter area at the bottom of the sealing zone. CONCLUSION: It is feasible to reduce gutters in CG configurations with the use of endoanchors in an in vitro juxtarenal aneurysm model.

Prediction of summation in incompletely fused tetanic contractions of rat muscle.

Summation is the accumulating contractile force resulting from sequential activations applied to a muscle without sufficient interval to permit complete relaxation. The purpose of this study was to evaluate summation in the rat medial gastrocnemius muscle, and to determine if the contractile responses during summation could be predicted from the relationship between force and activation pattern. In the first part of this study, the consistency of summation in the rat gastrocnemius muscle was assessed and prediction equations were derived. The second part compared predicted summation with actual contractions obtained in a new set experiments. Summation was assessed by calculation of the contractile response, per stimulation, for up to five stimulating pulses at these frequencies: 20, 40, 60 and 80Hz. This was done by subtraction of the force transient for j-1 pulses of stimulation (where j=1-5 pulses) from the force response with j pulses of stimulation. Each of these force differences was evaluated for peak rate of force development, contraction time and half-relaxation time. Contraction and half-relaxation times changed by only a small magnitude from values obtained for the twitch. Peak rate of force development was proportional to the active force for all force transients obtained by subtraction. The force per activation increased from the first to the fifth stimulus, and was dependent on interpulse delay. In the second series of experiments, the predicted force was related to the actual force for brief tetanic contractions at 40, 50 and 60Hz (r(2)=0.875). These experiments demonstrate that the force response to sequential activations is consistent and predictable. Summation can be predicted, knowing only the amplitude of the twitch contraction and the relationship between delay and force for each activating stimulus.