Background: See above. Aims:To study whether a new method of creating a buttonhole tunnel tracks can reduce the incidence of buttonhole technique failure and the patients pain with needling.
Patients and Methods: A randomized, multi-center study enrolling 42 patients in hemodialysis from two HD units in Denmark. The study will begin end of May 2019.
Participants are randomized into 2 groups where cannulation will be carried out by a small group of dialysis nurses with experience and skills in buttonhole cannulation. In both groups the same nurse will carry out the cannulation the first four dialysis sessions. At the following sessions the cannulation will be carried out by the nurse/nurses responsible for the patient. The procedures throughout the study will be the same in both participating centers.
The control group (K): creating buttonhole tunnels according to the standard method, ie. cannulation with a single sharp cannula in the AVF at each dialysis for 6-12 dialyses until a blunt needle can be inserted.
The intervention group (I): creating buttonhole tunnels according to the new method, ie. repeated cannulation with several sharp needles (4-6 pieces) at each dialysis for 1-3 dialyses until a blunt cannula can be inserted.
The creation of a buttonhole tunnel track is defined as completed when two consecutive dialyses have been carried out with no use of sharp needles, however no longer than 24 dialysis sessions.Thus, the period of time will be of different length for each participant. In the period until the tunnel is created, data will be collected at each dialyses regarding number of cannulations, type of needle (sharp or blunt), cannulator and patient-experienced pain with needling.
The primary outcome is buttonhole technique failure defined as the need for cannulations carried out using sharp needles in the buttonhole for three consecutive dialyses or in case lack of ability to insert blunt needles in the buttonhole for 2 weeks.
Follow-up from the date of the completed creation of the buttonhole tunnel track in both groups:
12 month ongoing follow-up of the primary outcome buttonhole survival and the secondary outcomes AVF associated infections, complications and AVF survival.
Sample size:The power calculation is based on the expected incidence of the primary outcome measure: buttonhole technique failure. Based on calculations in the two dialysis centers from randomly selected patients with buttonhole tunnels made using the intervention and the control method, it appears that the estimated buttonhole technique failure is 10 % and 30 %, respectively.
Drop-off rate is estimated to 30%. The number of participants for the study is calculated at 21 subjects in each group to achieve a power of 0.8 with a type error rate of 0.5.
Intention-to-treat analysis will be carried out. Censoring in case of death, if the person wants to withdraw from the study or moves, AV fistula failure for non-buttonhole associated causes and kidney transplant.
Statistical analysis:The baseline characteristics of the study population will be presented as counts and proportions and compared between randomization groups with chi-square test / Fisher's exact test (depending on number of observations) for categorical variables. Continous variables will be presented as mean (SD), respectively, median (IQR) depending on normality of data and compared between groups by t-test, respectively, Wilcoxon rank-sum test. Normality will be evaluated by quantile plots and Shapiro-Wilks test. Moreover, repeated measurements will be compared by mixed effects models. Time to event outcomes will be compared by the Kaplan-Meier method and tested by log-rank test, furthermore discrete time survival methods will be applied as a sensitivity analysis. P-values <0.05 are regarded as statistically significant. Follow-up will be censored at 1 year. Statistical analysis will be performed using Stata, version 11.0 (StataCorp, College Station, Tex., USA).