Catheter
In medicine, a catheter (/ˈkæθətər/)[1] is a thin tube made from medical grade materials serving a broad range of functions. Catheters are medical devices that can be inserted in the body to treat diseases or perform a surgical procedure. Catheters are manufactured for specific applications, such as cardiovascular, urological, gastrointestinal, neurovascular and ophthalmic procedures. The process of inserting a catheter is called catheterization.
In most uses, a catheter is a thin, flexible tube (soft catheter) though catheters are available in varying levels of stiffness depending on the application. A catheter left inside the body, either temporarily or permanently, may be referred to as an "indwelling catheter" (for example, a peripherally inserted central catheter). A permanently inserted catheter may be referred to as a "permcath" (originally a trademark).
Catheters can be inserted into a body cavity, duct, or vessel, brain, skin or adipose tissue. Functionally, they allow drainage, administration of fluids or gases, access by surgical instruments, and also perform a wide variety of other tasks depending on the type of catheter.[2] Special types of catheters, also called probes, are used in preclinical or clinical research for sampling of lipophilic and hydrophilic compounds,[3] protein-bound and unbound drugs,[4][5] neurotransmitters, peptides and proteins, antibodies,[6][7][8] nanoparticles and nanocarriers, enzymes and vesicles.
Placement of a catheter into a particular part of the body may allow:
Materials[edit]
Urinary catheters[edit]
A range of polymers are used for the construction of catheters, including silicone rubber, nylon, polyurethane, polyethylene terephthalate (PET), latex, and thermoplastic elastomers. Silicone is one of the most common implantable choice because it is inert and unreactive to body fluids and a range of medical fluids with which it might come into contact. On the other hand, the polymer is weak mechanically, and a number of serious fractures have occurred in catheters.[24][25][26] For example, silicone is used in Foley catheters where fractures have been reported, often requiring surgery to remove the tip left in the bladder.
There are many different types of catheters for bladder problems. A typical modern intermittent catheter is made from polyurethane and comes in different lengths and sizes for men, women and children.
Catheters used in interventional procedures[edit]
Depending on the mechanical characteristics required, assorted polymers and polymer-metal composites can be used to build catheters used for interventional purposes. Common materials include polyamide (nylon), polyether block amide, polyuerathane, polyethylene terephthalate, and polyimides. These materials are often used in combination with each other and are frequently layered on top of stainless steel braiding, laser-cut stainless steel tubing, or other scaffold-like structures to impart desirable handling characteristics to the catheter, all dependent on the intended application. For example, the materials and the architectures used to manufacture vascular catheters for neurological applications might differ significantly from catheters destined for cardiovascular use.
Guiding catheters (catheters that guides angioplasty balloons and stents) is made up of polytetrafluoroethylene (PTFE) innermost layer which is lubricious, followed by stainless steel braid wire outer layer which helps to provide support for the catheter and prevent kinking while travelling through blood vessels, and Nylon elastomer outermost layer which provides extra support for the catheter and preserve the curvature of the catheter while passing through tortuous vessels.[27]
To enhance ease of insertion, some catheters have a lubricious surface coating to lessen friction. A lubricious coating creates a smooth, slippery film making the catheter easier to insert.
Adverse effects[edit]
In interventional procedures, Teflon catheters (which are hydrophobic) have higher risk of thrombus formation when compared to polyurethene catheters. The longer the duration of the catheter left inside the body, the higher the risk of thrombus formation. Larger catheters increase the risk of thrombus formation around the catheter, because they can block the flow of blood.[37]
"Any foreign object in the body carries an infection risk, and a catheter can serve as a superhighway for bacteria to enter the bloodstream or body", according to Milisa Manojlovich, a professor at the University of Michigan School of Nursing.[38]
Catheters can be difficult to clean, and therefore harbor antibiotic resistant[39] or otherwise pathogenic bacteria.