Vascular access ports

Vascular access ports Vascular homeostasis Vasectomy Vasicine [6159-55-3]... 

Vascular access ports typically consist of a self-sealing siUcone septum within a rigid housing which is attached to a radiopaque catheter (see Radiopaques). The catheter must be fabricated from a low modulus elastomeric polymer capable of interfacing with both soft tissue and the cardiovascular environment. A low modulus polyurethane-based elastomer is preferred to ensure minimal trauma to the fragile vein. 

Placement of vascular access ports is similar to that of a long-term indwelling arterial catheter. A small incision is made over the selected vein and a second incision is made lower in the anterior chest to create a pocket to house the port. The catheter is tuimeled subcutaneously from its entry point into the vein with the tip inside the right atrium. The final position of the catheter is verified by fluoroscopy, secured with sutures, and the subcutaneous pocket is closed. The port septum is easily palpable transcutaneously, and the system may be used immediately. A surgeon typically inserts the vascular access port in an outpatient setting. 

Garramone, J.P (1986). Vascular Access Port Model SLA. User s Manual. Norfolk Medical Products, Skokie, IL. 

Sinko et al. [92] established an Intestinal and Vascular Access Port (IVAP) model where dogs were fitted with three intestinal catheters for site-specific administration to various section of the intestine (i.e. duodenum, ileum, and colon), one vascular catheter for access to the portal vein, and a peripheral vein (e.g. branchial) for IV access. The animals were allowed to recover for 2 weeks prior to initiation of studies. The extent of intestinal versus hepatic first-pass metabolism was determined by comparing blood levels following intra-duodenal (AUQ.d.) versus portal (AUVi.p.v.) versus intravenous (AUQ.V.) administration. The model also lends itself to a comparison of the impact of site-specific preferential absorption, and hence a determination of the optimal site for intestinal delivery. 

Kunta JR, Lee SH, Perry BA, Lee YH and Sinko PJ (2004) Differentiation of Gut and Hepatic First-Pass Loss of Verapamil in Intestinal and Vascular Access-Ported (IVAP) Rabbits. Drug Metab Dispos 32 pp 1293-1298. 

FIGURE 17-2 Schematic representation of an implantable vascular access port that can be used with PCA. The port can be connected to a PCA pump via a percutaneous needle, and a catheter leads from the port to a large central vein. [From Knox LS. Crit Care Nurse. 1987 7 71 with permission.]... 

Clearance procedures can be conducted in all laboratory animal species anesthetized and conscious animal models may be used. Measurement of arterial pressure is advisable, especially in anesthetized preparations, to insure that renal perfusion pressure remains within the autoregulatory range (usually 80-120 mmHg). Vascular access ports can be helpful to provide continuous arterial access for pressure measurements (Mann et al. 1987). 

Blood collection from the femoral artery is mentioned by Davis et al. (1994) after surgically preparing vascular access ports to the femoral artery. Using dogs with surgically instrumented indwelling venous access ports into the femoral vein and using a 6 min infusion instead of a intravenous bolus injection is mentioned by... 

Horizon Medical Products http //www.hmpvascular.com Vascular access ports... 

Kunta, J. R. et al., Differentiation of gut and hepatic first-pass loss of verapamil in intestinal and vascular access-ported (IVAP) rabbits, Drug Metab. Dispos., 32(11), 1293, 2004. 

Sinko, P. J., et al. (1997). Oral absorption of anti-aids nucleoside analogues 3. Regional absorption and in vivo permeability of 2 3 -dideoxyinosine in an intestinal-vascular access port (IVAP) dog model. Biopharmaceutics Cf Drug Disposition, 18(3), 697—710. 

FIGURE 20.11 An implantable vascular access port is shown. The port is accessed through the skin via needle and is lesilioit enough to allow hundreds of punctures and infusions before needing to be replaced. 

One issue with the use of blood gases as an endpoint in a safety pharmacology study is the technical challenge to collect them. For proper evaluation of respiratory effects, the blood sample must be collected from an artery which is difficult to locate in small species such as rats and difficult to obtain safely from any species without some form of physical or chemical restraint. As a modification for access, an arterial vascular access port (VAP) can be placed surgically, prior to study activities, but then requires subsequent careful maintenance to ensure patency. 

Konikoff MR, Denson LA (2006) Role of fecal calprotectin as a biomarker of intestinal inflammation in inflammatory bowel disease. Inflamm Bowel Dis 12 524-534 Kunta JR, Perry BA, Sutyak JP, Sinko PJ (2001) Development of a novel intestinal and vascular access port (IVAP) rabbit model to study regiospecific oral absorption pharmacokinetics. Comp Med 51(4) 349-356... 

---