Effect of needle orientation during arteriovenous access puncture on needed compression time after hemodialysis: A randomized controlled trial

There are two techniques for puncturing an arteriovenous fistula: one where the needle is inserted bevel up and then rotated to a bevel down position, and another where the needle is inserted bevel down. The aim of this study was to compare these two methods of needle insertion on minimum compression time required for hemostasis after needle removal.


INTRODUCTION
There are currently two different practices regarding the placement and orientation of needles during puncture of native arteriovenous fistulas: In one approach the needle bevel is oriented upwards during fistula puncture, after which the needle is immediately rotated to the bevel down position prior to starting extracorporeal blood flow.In another approach, the needle bevel is oriented downwards (e.g., toward the skin surface) during the puncture of the fistula.Which technique is used depends on the country, as well as on the experience and culture of a particular dialysis center. 1 In the journal of the French Association of Dialysis, Transplant and Nephrology Nurses (AFIDTN) it is recommended that metal needles be inserted bevel up and then turned 180 to the bevel down position after insertion into the vessel. 2eeping the needle bevel oriented downward during puncture should present an anatomical advantage when the needle is withdrawn since the vascular flap at the puncture site should rise under the effect of the blood flow and thus spontaneously close the orifice created by the insertion of the needle.Conversely, when the needle bevel is inserted with the bevel directed upwards, the fistula flap might fold back on the access wall and not completely close the puncture tract; this might lead to an increase in the compression time needed at the end of dialysis when the needle is removed (Figure 1). 2 The heterogeneity of fistula puncture techniques among nurses in dialysis centers, and the lack of specific studies in the literature, prompted us to explore the consequences to the patient of compression time and bleeding frequency.We hypothesized that the arteriovenous fistula puncture technique might influence the compression time needed for hemostasis on needle removal and might also reduce puncture pain.

Study design
This was a prospective, randomized, cross-over, blinded, single-center, routine care study.The study was registered at Clinicaltrial.gov (NCT03355508).The study received a favorable opinion from the French Committee for the Protection of Persons in March 2017 (nr 2-17-01).The Consort checklist for reporting randomized trials is included in the Supporting Information associated with this manuscript. 3he study ran from December 2017 to June 2020 in dialysis patients at Poissy Saint-Germain-en-Laye's Hospital, France.The study was offered to patients older than 18 years with chronic kidney failure being treated by hemodialysis using a native arteriovenous fistula.The fistula had to have been in use for more than 3 months and the usual puncture had to be done using two needles (one arterial and one venous).Before the study, the nurses' practices in the center were heterogeneous.Both methods of puncture (bevel up or down) were used according to the preference of the nurse.Patients who did not understand or speak French, patients awaiting a living donor renal transplant, patients who had undergone more than two percutaneous angioplasties in the previous 6 months, and patients being dialyzed using an arteriovenous graft were excluded.
The sample size was determined by the team's biostatistician.In the absence of published data but based on the professional practice of the authors of the project, it was hypothesized that the use of bevel-down needle insertion would lead to an average reduction of 5 min in compression time.The within-subject standard deviation was estimated to be 8 min.Within-subject correlation was set at zero because the patients are not always dialyzed by the same caregiver for logistical reasons.The primary analysis of the difference in compression times between the two needle placement techniques was performed using a linear mixed model with the final minimum compression time as the dependent variable, a random effect for the subject effect, using a Gaussian distribution with a mean of zero and a variance to be estimated, as well as fixed effects for the needle placement method (bevel-up vs. bevel-down), the parameter of interest in the study, and for the sequence effect (high-low vs. low-high), and the period effect.To achieve a two-sided alpha risk of 5%, with 80% power, it was estimated that 42 subjects would be needed.

Intervention
The study used a balanced, crossover design, with the order of the two different needle insertion techniques determined by randomization.An initial 2-week observation phase was used to evaluate the average compression time for each patient, during which time the access was punctured with needles inserted bevel up (the technique recommended by the AFIDTN).
After the baseline compression time was determined, the minimum compression time was determined during each of the two follow-up periods.During one follow-up period, the access would be punctured with needles inserted bevel up, and then rotated into the bevel down position prior to initiating blood flow.During the other follow-up period, the access would be punctured with needles inserted bevel down.The order of the two followup treatments (bevel-up vs. bevel-down insertion) for a given patient was randomized (Figure 2).
During each of the intervention phases, the minimum compression time required for hemostasis at the end of dialysis was determined.For each patient, a gradual decrease in compression time from the baseline compression time was attempted: compression time was reduced by 1 min every 3 weeks, repeated as necessary until two or more bleeds occurred within a 3-week period.The minimum compression time was defined as one where no bleeding occurred after puncture-site compression was stopped.
Each patient serves as his or her own control: the minimum compression time during the bevel-up versus the bevel-down needle insertion period was the primary comparison of interest.
In order to avoid bias in the assessment of compression time, one nurse punctured the fistula and another nurse performed the needle removal and compression of the puncture site postdialysis to determine the minimum compression time.The incidence of re-bleeding from the puncture site after the patient was discharged from the dialysis unit was also determined.
Other measurements at each dialysis session during follow-up included an assessment of puncture-related pain.The patient was asked (by the nurse who performed the access puncture) "Can you give me a score from 0 to 10 to describe the level of pain that you felt during access puncture, with score of 0 being no pain and score of 10 being unimaginable pain?"

Data analysis
Data were analyzed using statistical software R version 4.2.1 (R Foundation for Statistical Computing, Vienna, Austria).The primary analysis of the difference in compression times between the two needle placement techniques was performed using a linear mixed model with the final minimum compression time as the dependent variable.

RESULTS
We included 42 patients in this study, comprising both men and women with a mean age of 68 years.A radial artery arteriovenous fistula was the most common vascular access (43%).Hypertension and diabetes were the leading causes of renal failure (Table 1).
The baseline compression times in the UP-DN and DN-UP patient groups were similar (Table 2), 10.1 ± 4.6 and 10.6 ± 5.1 min, respectively, (P NS).The mean difference between baseline compression time and minimum compression time during the bevel-up needle insertion period was 0.8 ± 3.7 min, and the difference in compression time during the bevel-down needle insertion period was 1 ± 3.3 min (P NS).The required time spent in each intervention period to establish the minimum compression time was 26 ± 74 and 21 ± 27 days for the bevel-up and bevel-down periods, respectively (P NS).The minimum compression time required for homeostasis after needle removal was on average 10.8 min (9.23-12.4)when the access needle had been inserted in the bevel-down orientation and 11.1 min (9.61-12.5)when the needle orientation during insertion was bevel up (p = 0.723; Table 2).
The orientation of the access needles during puncture of the arteriovenous fistula did not significantly influence the pain related to access puncture felt by the patient (p = 0.06) (Table 3).
The needle bevel orientation during insertion had no significant effect on average blood flow (p = 0.327), on dialysis circuit prepump arterial pressure ( p = 0.178) nor on postdialyzer venous pressure (p = 0.371).No adverse events were observed in this study (Table 4).
T A B L E 1 Patients' characteristics.

Patient characteristics
All patients (n = 42)

DISCUSSION
In this study, we found that the orientation of the bevel of the vascular access needle during insertion had no impact on hemostasis after needle removal nor on the pain associated with puncture.Our results are not in agreement with some previous studies.For example, a 6-month study of 17 patients with 374 bevel-up and 374 bevel-down punctures by Gaspar and colleagues showed that orienting the needle bevel downward during fistula insertion was associated with reduced blood loss during the session and significantly reduced the occurrence of hemorrhage on needle removal. 4Ozen et al, studying 35 patients over six sessions with bevel-up puncture and six with bevel down, found a reduction in postdialysis compression time after needle removal when a downward bevel technique was used for fistula puncture. 5Montero and colleagues, in a study of 48 patients, compared the size of the skin incision with a needle bevel-down insertion approach versus a needle bevel-up technique.They reported that the size of the skin incision was smaller with the needle bevel don method. 6Parisotto et al. reported that rotation of a needle that had been inserted bevel-up was done in 42%-50% of cases, and speculated that this postinsertion rotation might cause damage to the vascular endothelium. 7he effect of needle orientation during insertion has been reported to affect the degree of puncture-associated pain.Montero et al found that puncture-related pain was less when the needle bevel was oriented downward during insertion; however, they were unable to correlate puncture pain with incision size.Ozen et al., in their study of 35 patients, reported a significant reduction in pain during access puncture using the downward bevel technique. 5In our study, needle orientation was not associated with puncture-associated pain.The pain reported by our patients on access puncture was quite mild, averaging only 1 on a 0-10 intensity scale.Aitken et al. reported that the intensity of access puncturerelated pain might depend on how pain intensity was assessed: while 25% of the patients reported severe pain in their questionnaire, the average pain score found by numerical scale of 0-10 was 3, ranging from 0.5 to 4.5. 8everal questions remain unanswered: what is the optimal distance between an access puncture point and any access aneurysms when present?What is the optimum angle between the skin and the needle during insertion?What is the optimum amount of pressure to use during compression after needle removal?Each of these factors might potentially influence the needed compression time for hemostasis after needle removal.

Limitations
This was a single-center study and therefore subject to potential selection bias concerning patients and nurses.A larger, multicentric study would be useful to confirm our results, especially given the different results from some other investigators.Some patients refused to be included (n = 14) in the study because, since compression had to be performed by a nurse rather than by the patients themselves, patients in the study were disconnected last, thus lengthening their dialysis session slightly.

CONCLUSION
This study showed that the orientation of the needle bevel during the puncture of an arteriovenous fistula for hemodialysis had no impact on the compression time needed postdialysis to achieve hemostasis.There was also no effect on puncture pain nor on ability to achieve the desired blood flow rate, nor on the prepump arterial or venous pressures.At this stage, we cannot propose best practices in terms of any particular needle orientation during access puncture.

F
I G U R E 1 Illustration of the theoretical anatomical advantage of the bevel down compared to bevel up access puncture. 2[Color figure can be viewed at wileyonlinelibrary.com]

F
I G U R E 2 Protocol diagram.Decrease compression time by 1 min every 3 weeks from baseline.Continue to decrease compression time if one or no bleeding episodes over the 3 weeks.Stop the intervention period if two or more bleeds occur, and then change to the opposite intervention.
Effect of needle position on postremoval hemostasis.
a Patients may have one or several of the following disease.T A B L E 2