Subcutaneous ported catheters

There is some disagreement as to whether infectious complications differ with the use of different types of chronic central venous access devices in patients with cancer. In one study there was no significant difference in the risk of infection between subcutaneous ports and external catheters (26). However, this has been disputed by other workers, who found that in children with cancer there was a lower infection rate when subcutaneous ports were used compared with external catheters (27). The differences between the studies and the conclusions reached may be the result of their size and design, rather than real differences. 

Long-term central venous access devices used for chemotherapy can be categorized into peripherally inserted central catheters (PlCCs), chest wall external catheters (tunneled and non-tunneled), and subcutaneous ports (chest wall and extremity). 

Several factors influence the choice of a specific venous access device length and frequency of therapy patient comfort or activity ability to care for the device personal preference (physician, nurse, home health care and patient). Devices suitable for intermediate lengths of treatment (weeks to months) include PICCs, non-tunneled, and tunneled chest wall catheters. Longer therapies (months to years) favor tunneled external chest wall catheters and subcutaneous ports. Daily access would favor an external... 

Analogous to the placement of externally tunneled catheters, there are three basic steps to the successful placement of subcutaneous ports (1) venous access, (2) pocket creation, and (3) catheter insertion. The reservoir and catheter may be attached prior to or following catheter insertion into the venous system. This distinction will modify the insertion procedure. 

When dealing with subcutaneous ports, choices for device revisions include (1) removal of the entire old device and insertion of a new device in an entirely different location (2) removal of the entire old device and insertion of a new device via the same venous access site and pocket (3) removing the entire old device and insertion of a new device with the same venous access site but new pocket location and (4) replacing only the catheter portion of the device. Our preference is to maintain the same venous access site and create a new pocket. As described above, local dissection at the original venous access site will allow one to maintain the same venous entry (Mauro 1998). 

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. 

Almost 30 routes exist for administration of drugs to patients, but only a handfbl of these are commonly used in preclinical safety studies (Gad, 1994). The most common deviation from what is to be done in clinical trials is the use of parenteral (injected) routes such as IV (intravenous) and SC (subcutaneous) deliveries. Such injections are loosely characterized as bolus (all at once or over a very short period, such as five minutes) and infusion (over a protracted period of hours, days, or even months). The term continuous infusion implies a steady rate over a protracted period, requiring some form of setup such as an implanted venous catheter or infusion port. 

Blanco and Samadani37 obtained a patent for the construction of a microprosessor-based insulin pump that works in a similar fashion to the Biostator. The implantable infusion device consists of a catheter, an information-transmitting sensor located in the catheter, a microprocessor, a pump, the drug reservoir, and a power source. The pump, the sensor, and the valves are connected by appropriate leads to the microprocessor. The device is implanted in the subcutaneous tissue in the chest area, and the infusion catheter is tethered intravenously to a central location, such as the right atrium. The device is inserted with the inlet port facing outward so that it may be refilled periodically by a physician. 

Central venous catheters are reluctantly used as blood access for hemodialysis because of safety concerns and frequent complications, for example sepsis, thrombosis, and vessel stenosis. Nevertheless, 20% or more of all patients rely on atrial catheters for chronic dialysis because of lack of other access. Potentially fatal risks related to central venous catheters include air embolism (1), severe blood loss (2), and electric shock (3). These specific risks have been substantially eliminated by the inherent design and implantation of Dialock (Biolink Corporation, USA). Dialock is a subcutaneous device consisting of a titanium housing with two passages with integrated valves connected to two silicone catheters. The system is implanted subcutaneously below the clavicle. The tips of the catheters are placed in the right atrium. The port is accessed percutaneously with needle cannulas. 

Mechanical difficulties, in the form of backflow of solution from epidural catheters, occurred in 31 of 32 patients and there were neurological complications in a further two of eight patients in whom the catheter had been tunnelled and connected to a subcutaneous access port epidural fibrosis with compression of the spinal cord was presumed to be the cause (144). 

Central venous catheters vary in composition, lumen size, number of injection ports, and other special features that affect ease or convenience of care and maintenance. They may be placed for shorter long-term access. Frequently, short-term central venous access is obtained in critically ill neonates via a catheter placed in the umbilical vein. ° Other sites for central venous access in infants and older children are similar to those in adults. When therapy is expected to last longer than 4 weeks, the catheter usually is tunneled subcutaneously before entering the central vessel, secured initially with retaining sutures, and anchored in place with a felt cuff that promotes the growth of subcutaneous flbrotic tissue around the catheter. The injection port may remain external or be concealed entirely beneath the skin. Implanted central venous catheters have a larger port or reservoir that is surgically placed beneath the skin surface and anchored in the muscle of the chest wall. 

Subcutaneous implantable devices are composed of a reservoir component made of stainless steel, titanium, or plastic connected to a polyurethane or silicone catheter (Fig. 6.3). The reservoirs are implanted into the subcutaneous tissues in the chest wall, upper arm, or forearm (Jaques et al. 1992 Foley 1995 Kaufman et al. 1996). The stainless steel ports produce significant artifacts on computed tomography (CT) and magnetic resonance imaging (MRl), and are not often used in the chest wall location. Titanium ports cause only local MRI degradation and plastic ports result in minimal CT... 

Following venous access, the transition dilator is exchanged over a working wire for the peel-away sheath. The catheter with its end clamped is inserted into the right atrium and flushed. The port is then created, followed by the creation of the subcutaneous tunnel. The end of the catheter is brought through the tunnel. The catheter tip is placed in its desired location fluoroscopically and the end of the catheter is cut and attached to the port The port is then re-positioned... 

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