Cauterizing Conductive Catheter for Percutaneous and/or Vascular

Intervention

Brad Wood, M.D.Charles Blyth

Cristina FernandezScott Hittinger

Cameron JonesBrian McGee

National Institute of Health

• NIH– “NIH is the steward of medical and behavioral

research for the Nation. Its mission is science in pursuit of fundamental knowledge about the nature and behavior of living systems and the application of that knowledge to extend healthy life and reduce the burdens of illness and disability.” (www.nih.gov)

Our Project

• Catheter material selection, design, and testing for nephrostomies, biliary tubes, and possibly the vascular tree.– Conductivity

• Deliver RF pulse via catheter, not a needle• Dielectric Constants• Maxwell’s Equations

– Biocompatibility• Maneuverable!

– Practicality• Price• Ease of manufacture• Use in the OR

Past Attempts

• Biopsy Environment Only• High RF Pulse

– Cauterize after biopsy• Tissue damage• RF tip on a metal needle inserted through the

catheter.

• Collagen/Fibrin Plug– Pull Biopsy needle, inject compound

• Impractical• Expensive

Biopsy Approach

Fig. 1 – Fibrin Plug Injection1

Fig. 2 – Left no plug Right with plug1

Fig. 3 – High frequency RF ablation2

1. Paulson et al. “Use of Fibrin Sealant as a Hemostatic Agent after Liver Biopsy in Swine”. Hepatic Intervention 2000.2. Pritchard et al. “Radiofrequency Cauterization with Biopsy Introducer Needle”. Journal of Vascular Interventional Radiology

2004.

Specifics

• Current catheters are Polyparaxylylene (PPX) which cost approximately $13 a piece or more and is not a conductive material.

• RF pulse upwards of 100 kHz– Testing for biopsy procedure uses 200W, 480

kHz RF generator (CCI Cosman coagulator system, Radonics, Burlington, MA)

• “Radiofrequency cauterization with introducer needle”. JOURNAL OF VASCULAR INTERVENTIONAL RADIOLOGY. 2004. 15:183-187.

Let’s Burn Someone

• Cauterization of 1mm +/- 0.5mm outside of the catheter – assumes no cooking within the catheter

• 70˚C – 100˚C – this value is based on the cauterization temperature of tissue and the possible melting temperatures of many biocompatible materials.

• “Radiofrequency cauterization with introducer needle”. JOURNAL OF VASCULAR INTERVENTIONAL RADIOLOGY. 2004. 15:183-187.

Size Does Matter

• 5 French (5F) catheters - .038 inch diameter

• 1-2 mm in diameter– Currently using 2.0mm Tru-Cut needles or

1.6mm Jamshidi needles for biopsy procedures. (just a reference size)

• Current biopsy RF pulse ablation– Animal testing with 14 gauge, 10cm coaxial

introducer needle.

Our Turn

• So lets find something with these properties that will make for a useful, practical, RF pulse generating catheter!

• “Surgical glues and sealants are expected to significantly take over sutures and staples in the next 10 years.”

September 24, 1998 – “Marine Polymer Technologies”

Closure Devices/Companies

• Epotek

• AngioSeal

• StarClose – produced by Abbott Vascular

• Syvek

• Kumpe Access Catheter – from Cook Urological

Timeline

Current Work

• Looking into all companies and material properties of promising compounds for catheter manufacturing– Conducting Silicone based material– Conducting Polyurethane material

• Focusing in on most important aspects of thermal properties, biocompatibility (toxicity, density, maneuverability), and in contact with Dr. Wood’s colleagues regarding thermal calculations regarding heat loss, and other colleagues regarding current volume loss of urine (nephrostomies) and blood (liver and vasculature).

Future Steps

• Obtain possible biomaterials for production of catheters.

• Create prototype

• TEST IN COW LIVER!!!

• Approach VU individuals about biomaterials for possible solution.

• Proof of Concept