When medical devices fail: Lessons learned in a hemodialysis unit.

Technology and medical equipment devices have become integrated in the delivery of health care. These technologies and devices can introduce new risks, either through user error or malfunction. When these incidents occur, it is important they are reported so that learning and improvements are possible. A just culture encourages reporting of incidents by not blaming individuals, but rather by seeking to understand incidents in relation to how they occurred because of the systems in place. These concepts are explored through a case study in a dialysis unit where a malfunction of a medical equipment device (central venous catheter) was identified. The process for addressing the issue is defined and includes reviewing applicable data, reporting incidents, and evaluating devices that malfunctioned. Finally, the role of the frontline health care professional is identified as an important stakeholder in identifying issues with technology and medical devices, reporting these incidents, and participating in the process that resolves the issues.

Effectiveness and Cost of Weekly Recombinant Tissue Plasminogen Activator Hemodialysis Catheter Locking Solution.

BACKGROUND AND OBJECTIVES: Evidence to guide hemodialysis catheter locking solutions is limited. We aimed to assess effectiveness and cost of recombinant tissue plasminogen activator (rt-PA) once per week as a locking solution, compared with thrice weekly citrate or heparin, in patients at high risk of complications. DESIGN, SETTING, PARTICIPANTS, & MEASUREMENTS: We used a prospective design and pre-post comparison in three sites across Canada. Pre-post comparisons were conducted using multilevel mixed effects regression models accounting for cluster with site and potential enrollment of patients more than once. In the pre period, catheter malfunction was managed as per site-specific standard of care. The intervention in the post period was once weekly rt-PA as a locking solution (with citrate or heparin used for other sessions). The primary outcome was rate of rt-PA use for treatment of catheter malfunction. Secondary outcomes included rates of bacteremia, management of catheter malfunction, and cost. RESULTS: There were 374 patients (mean age 68 years; 52% men) corresponding to 506 enrollments. Mean length of enrollment was 200 days (SD 119) in the pre period and 187 days (SD 101) in the post period. There was a significant decline in rate of rt-PA use for treatment of catheter malfunction in the post compared with pre period (adjusted incidence rate ratio, 0.39; 95% confidence interval, 0.30 to 0.52); however, there was no difference in the rate of bacteremia, or catheter stripping or removal/replacement. The increase in mean total health care cost in the post period was CAD$962 per enrollment, largely related to costs of rt-PA as a locking solution. CONCLUSIONS: Once weekly rt-PA as a catheter locking solution was associated with a reduction in rt-PA use for treatment of catheter malfunction. Our results showing a reduction in rescue rt-PA use are consistent with a prior randomized trial, although we did not observe a reduction in bacteremia or catheter stripping/removal and did observe an increased incremental cost of this strategy primarily accounted for by the cost of the rt-PA.

Comparison of intensive versus standard hemodialysis central venous catheter dysfunction protocol using rt-PA: a quality assurance initiative.

PURPOSE: Catheter locking solutions such as recombinant tissue plasminogen activator (rt-PA) are used to treat and prevent clotting of hemodialysis (HD) catheters during HD treatments and the interdialytic period. However, evidence to guide the use of rt-PA for catheter dysfunction is limited. METHODS: We evaluated outcomes using two catheter dysfunction protocols in a cohort of consecutive prevalent dialysis patients (Jan 2013 to Sep 2014) undergoing HD with a tunneled catheter. In the intensive protocol, rt-PA was administered to all catheters based on blood flow and/or line reversal. In the standard protocol, rt-PA administration was based only on blood flow. The primary outcome was the rate of rt-PA use for catheter malfunction (rt-PA treatment days/1000 total line days; [TLD]). Secondary outcomes included the cost of rt-PA/TLD and the rate of catheter-related bacteremia. RESULTS: There were 26 and 35 patients managed by the intensive and standard protocols, respectively. The rate of rt-PA use was 52/1000 TLD (intensive) versus 39/1000 TLD (standard) (rate ratio 1.30, 95% CI 1.12-1.52 CI, p<0.001). The rate of bacteremia was 0.43 and 0.22/1000 TLD for the intensive and standard protocols, respectively (p = 0.491). The cost of rt-PA was CDN $5.58 and CDN $6.15 per TLD for the intensive protocol and standard protocol groups (p<0.001). CONCLUSIONS: Managing catheter dysfunction based on line reversal and blood flow as opposed to only blood flow was associated with a higher rate of rt-PA use, but at a reduced overall cost.

An evaluation of oral dabigatran etexilate pharmacokinetics and pharmacodynamics in hemodialysis.

Dabigatran etexilate represents a possible improved alternative to warfarin for anticoagulation in hemodialysis patients with atrial fibrillation (AF). The objective was to determine dabigatran plasma concentrations and anticoagulant effects following administration of a single 110 mg oral dose of dabigatran etexilate to 10 adult patients immediately prior to starting hemodialysis. Mass spectrometry and the Hemoclot® assay were used, respectively, to determine free (unconjugated) dabigatran concentrations and thrombin time (TT) in plasma samples collected intermittently over 48 hours. The median time (tmax ) to reach the maximum plasma-free dabigatran concentration (Cmax ) was 2 hours (range 1-3 hours). The mean free dabigatran Cmax was 95.5 ± 33.4 ng/mL. The mean elimination half-lives on and off hemodialysis were, respectively, 2.6 ± 1.3 and 30.2 ± 7.8 hours. Hemodialysis effectively removed dabigatran with an extraction ratio of 0.63 ± 0.07. The maximal TT ratio was 2.1 and the TT ratio demonstrated a strong linear dependence on free dabigatran concentration (r(2) = 0.741). A 110 mg oral dabigatran dose prior to hemodialysis was rapidly absorbed and achieved therapeutic concentrations. Hemodialysis effectively removed dabigatran from the plasma and may be an effective means of accelerating the elimination of dabigatran in circumstances of excessive anticoagulation.

Best threshold for diagnosis of stenosis or thrombosis within six months of access flow measurement in arteriovenous fistulae.

Canadian clinical practice guidelines recommend performing angiography when access blood flow (Qa) is <500 ml/min in native vessel arteriovenous fistulae (AVF), but data on the value of Qa that best predicts stenosis are sparse. Because correction of stenosis in AVF improves patency rates, this issue seems worthy of investigation. Receiver-operating characteristic curves were constructed to examine the relationship between different threshold values of Qa and stenosis in 340 patients with AVF. Stenosis was defined by the composite outcome of access failure or angiographic stenosis occurring within 6 mo of the first Qa measurement. The Qa value was then classified as true negative, true positive, false negative, or false positive for stenosis. An additional analysis was performed in which Qa was corrected for systolic BP before assigning it to one of the four diagnostic categories. The area under the curve for the composite definition of stenosis was 0.86. Graphically, Qa thresholds of <500 and <600 ml/min had similar efficacy for detecting stenosis or access failure within 6 mo, and both seemed superior to <400 ml/min. However, the frequency of the composite definition of stenosis among AVF with Qa between 500 and 600 ml/min was only 6 (25%) of 24, as compared with 58 (76%) of 76 when Qa was <500 ml/min. This suggests that most lesions that would be found using a threshold of <600 ml/min occurred in AVF with Qa <500 ml/min and that the small gain in sensitivity associated with the <600-ml/min threshold would be outweighed by the reduced specificity compared with <500 ml/min. Correcting Qa for BP did not improve diagnostic performance or change these results, which were consistent in several sensitivity analyses. Qa measurements seemed to predict stenosis or incipient access failure equally well in groups defined by diabetic status, gender, and AVF location. In conclusion, it was found that Qa <500 ml/min seems to be the most appropriate threshold for performing angiography in patients with native vessel AVF. It is recommended that clinicians arrange angiography when Qa is <500 ml/min in AVF.

Factors associated with access blood flow in native vessel arteriovenous fistulae.

BACKGROUND: Access blood flow (Qa) identifies stenosis in patients with native vessel AV fistulae (AVF), but data on factors that are associated with Qa in normally functioning accesses are sparse. Such factors could be used in conjunction with Qa to improve the diagnostic performance of screening. We examined the relationship between Qa and certain clinical characteristics in a large group of patients with AVF. METHODS: This was a retrospective study of incident and prevalent haemodialysis patients treated at a single institution, all of whom had a functioning AVF during the study period. Qa was measured bimonthly using ultrasound dilution in all subjects. Mixed models were used to explore the relationship between Qa and a group of independent variables, including systolic blood pressure (SBP), diastolic blood pressure (DBP), mean arterial pressure (MAP), diabetes mellitus, patient age, sex, height, body mass index (BMI) and AVF location (forearm vs upper arm). RESULTS: A total of 4084 Qa measurements was made in 294 patients. Univariate analysis found that younger patient age, non-diabetic status, higher blood pressure (SBP, DBP, MAP, all at the time of Qa measurement), upper arm AVF location and overweight status (BMI >/=25) were significantly associated with Qa. SBP appeared to be more strongly associated with Qa than either DBP or MAP. Patient sex, height and interval between access creation and Qa measurement were not significantly associated with Qa. Tests for interaction suggested that the association between SBP and age and Qa varied significantly by access location. In a multivariate model, SBP, overweight status and diabetic status were independently associated with Qa. The strength of the association between these characteristics and Qa appeared to be clinically relevant. CONCLUSIONS: Our findings suggest that a single Qa threshold for angiography in all patients may be simplistic, and that the optimal threshold might vary by patient subgroup. The strong association between SBP and Qa suggests that adjusting Qa for SBP may improve the specificity of access screening. Further work is required to determine whether such modifications to current practice would improve the predictive power of Qa measurements for detection of stenosis in AVF.

Access flow monitoring of patients with native vessel arteriovenous fistulae and previous angioplasty.

Screening strategies based on measurement of access blood flow (Qa) allow detection and angioplasty of subclinical stenosis in native vessel arteriovenous (AV) fistulae. However, little is known about the efficacy of Qa measurements for detecting recurrent stenoses in fistulae and that of angioplasty for correcting them. A total of 303 patients were studied over 30 mo; 69 (23%) of these had stenoses, of whom 53 underwent angioplasty. Of those undergoing angioplasty, 30 patients had 46 episodes of recurrent positive studies and underwent repeat fistulography. In 31 of these episodes (19 patients), stenosis was again identified and treated successfully with angioplasty. Overall positive predictive values for stenosis were similar in first and subsequent episodes of stenosis (71% versus 67%), and angioplasty was associated with sustained increases in Qa for both first and subsequent episodes. Assisted patency in fistulae that required repeat angioplasty was 87% (median follow-up 10 mo after the second angioplasty). In conclusion, Qa is effective for detecting first and subsequent lesions in patients with AV fistulae, and angioplasty of first or subsequent lesions is associated with sustained increments in Qa. Continued screening after correction of first stenoses appears reasonable, because of both the frequency of recurrent stenosis and the success of repeat intervention.