Assessment of needle tip geometry during infusions into a brain phantom gel

Convection-enhanced delivery (CED) is a promising method to deliver therapeutic drugs directly into the brain that has shown limited efficacy, mainly attributed to backflow, in which the infused drug flows back along the needle track rather than forward into tissue. This study evaluates the effect of sharp and blunt needle tips on backflow length under different flow rates via CED. Infusions were performed in a transparent 0.6% (w/v) brain phantom agarose hydrogel. Backflow length was significantly higher using sharp-tip needles for higher flow rates. No significant differences were observed between tip shapes for lower flow rates. In conclusion, sharp-tip needles present limitations for higher flow rates, which are needed to deliver more drug during shortest times.

Non-randomized safety and performance evaluation of the av-Guardian vascular access system

Introduction: The ability to successfully cannulate the arteriovenous fistula reliably is a critical step in the delivery of hemodialysis therapy. The av-Guardian vascular access system (Advent Access, Singapore) is designed to overcome the technical barrier to establishing reliable blunt needle access in patients with mature arteriovenous fistula. Methods: This was a first-in-man, prospective, non-randomized trial (registered on the Australian New Zealand Clinical Trial Registry (ACTRN12617000501347)) performed to assess the safety and feasibility of achieving repeatable successful cannulation via av-Guardian vascular access system to facilitate blunt needling in patients with mature arteriovenous fistula. The primary endpoints of the study included rate of successful hemodialysis sessions via av-Guardian vascular access system cannulation over 3 months and safety of the implants. Results: A total of six patients (four patients with brachiocephalic and two with radiocephalic arteriovenous fistula) were enrolled in the study. A pair of av-Guardian vascular access system were implanted, one each at the arterial and venous cannulation sites, under local anesthesia. Overall, the rate of successful cannulation through the av-Guardian vascular access system over 3 months in 216 hemodialysis sessions was 98.1% (212/216) at the arterial site and 94.4% (204/216) at the venous site. Significantly, 90% and 85.5% of the cannulations at the arterial and venous site, respectively, were successful at first attempt. Blood flow rates within the arteriovenous fistula were unaffected by the devices. Conclusion: The results demonstrated the safety and feasibility of a subcutaneously implanted, extravascular device in achieving repeatable successful cannulation via a constant site, to facilitate blunt needling in matured arteriovenous fistula in limited number of patients.

Comparison of Intravascular Injection Rate Between Blunt and Sharp Needles During Cervical Transforaminal Epidural Block

Background: Cervical transforaminal epidural block (CTEB) is a useful option in the diagnosis and treatment of cervical radicular pain. However, inadvertent intravascular injection can lead to severe neurologic complications. Blunt needles are considered to displace instead of penetrate vessels because of their dull needle tip. Objectives: To investigate whether there is a difference between blunt and sharp needles in intravascular injection rates during CTEB. Study Design: Prospective, randomized, clinical trial. Setting: A tertiary hospital in South Korea. Methods: After institutional review board approval, 108 patients undergoing CTEB for treatment of radicular pain resulting from spinal stenosis and herniated nucleus pulposus were randomly assigned to one of 2 needle groups (blunt needle or sharp needle). The needle position was confirmed using biplanar fluoroscopy, and 2 mL of nonionic contrast medium was injected to detect intravascular injection. Intravascular injection was defined as the contrast medium spreading out through the vascular channel during injection under realtime fluoroscopy. This study was registered in ClinicalTrials.gov. Results: The intravascular injection rate was not significantly different between the blunt needle and sharp needle groups (35.2% vs. 33.3%, P > 0.05). The procedure time was longer in the blunt needle group than in the sharp needle group (101.00 ± 12.4 seconds vs. 56.67 ± 8.3 seconds, P < 0.001). Limitations: This was a single-center study. Additionally, the physicians could not be blinded to the type of needle used. Conclusions: In the present study, use of a blunt needle did not reduce the rate of intravascular injection during CTEB compared to use of a sharp needle. In addition, procedure time significantly increased with blunt needle use compared to sharp needle use. Key words: Analgesia, bleeding, blunt needle, cervical spine, clinical trials, complications, intravascular injection, radiculopathy, sharp needle, transforaminal epidural block