Background and objectives: Concentrated heparin solutions are instilled into the catheter lumens after each hemodialysis session to prevent catheter thrombosis. The heparin lock concentration at many centers has been decreased recently to reduce the risk of systemic bleeding and contain costs. However, the effect of this change on catheter patency is unknown. We compared catheter patency between two heparin lock solutions: 1000 versus 5000 units/ml. Design, setting, participants, & measurements: With use of a prospective, computerized, vascular access database, 105 patients with newly placed tunneled hemodialysis catheters, including 58 patients receiving a 5000 units/ml heparin lock and 47 patients receiving a 1000 units/ml heparin lock, were retrospectively identified. The primary endpoint was cumulative catheter patency and the secondary endpoint was frequency of thrombolytic instillation.Results: Cumulative catheter survival was similar in the two groups, being 71% versus 73% at 120 days in the low-and high-concentration heparin lock groups (hazard ratio of catheter failure, 0.97; 95% confidence interval, 0.45 to 2.09; P ‫؍‬ 0.95). The frequency of tissue plasminogen activator instillation was significantly greater in the low-concentration heparin group (hazard ratio, 2.18; 95% CI, 1.26 to 3.86; P ‫؍‬ 0.005). No major bleeding complications were observed in either treatment group. The overall drug cost for maintaining catheter patency was 23% lower with the low-concentration heparin lock ($1418 versus $1917) to maintain catheter patency for 1000 days.Conclusions: Low-concentration heparin lock solutions do not decrease cumulative dialysis catheter patency, but require a twofold increase in thrombolytic instillation to maintain long-term patency.

Cardiorrespiratory fitness is a capacity to perform, through body adaptations and responses, dynamic activities of moderate to high intensity using large muscle groups, during long time. It determines an important part of possibilities to perform activities of daily living and is closely related with health and quality of life. The measurement of the maximal oxygen uptake (VO2max) as a parameter of this fitness is useful for educating about the physical conditioning and in prescription and control of fitness programs in sick and healthy subjects.The aim of the study was to develop a regression equation to predict VO2max based on non‐exercise data in patients with chronic low back pain (CLBP). All patients (N=70) achieved a maximal graded exercise test with measured VO2max (30.8 ml.kg−1.min−1 +/− 7.7). The regression model included as non‐exercise data, the patient's sex, body mass index (BMI) and intensity of sports activities (IPAS). Multiple linear regression generated the following formula (R2 = 38.3, SEE = 6.08 ml.kg−1.min−1): VO2max (ml.kg−1.min−1) = 35.337 − 0.475 * BMI + 0.155 * IPAS + 7.976 * sex (women = 0 and men =1)The Durbin Watson statistic demonstrated inexistence of problems with serial autocorrelation (D–W = 1.86). The K–S normality test demonstrated that the errors are distributed normally. This study provides a relatively precise non‐exercise regression model to predict VO2max in CLBP patients.