Catheter

Catheter
Catheter disassembled
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In

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.

Etymology

"Catheter" (from Greek καθετήρ kathetḗr) comes from the Greek verb καθίεμαι kathíemai, meaning "to thrust into" or "to send down" because the catheter allowed fluid to be "sent down" from the body.^[9]

Uses

Placement of a catheter into a particular part of the body may allow:

• Draining
  intermittent catheters or Foley catheter inserted through urethra. When the urethra is damaged, suprapubic catheterisation is used instead. The suprapubic catheter is inserted through the lower part of the abdomen directly into the urinary bladder.^[10]
• drainage of urine from the kidney by percutaneous (through the skin) nephrostomy
• drainage of fluid collections, e.g. an abdominal abscess
• pigtail catheter: used to drain air from around the lung (pneumothorax)
• administration of
  intravenous fluids, medication or parenteral nutrition with a peripheral venous catheter or central venous catheter
• balloon sinuplasty, cardiac electrophysiology testing, catheter ablation. Often the Seldinger technique
  is used.
• direct measurement of blood pressure in an artery or vein
• direct measurement of intracranial pressure
• administration of
  subarachnoid space, or around a major nerve bundle such as the brachial plexus
• transfer of fertilized embryos, from
  in vitro fertilization, or sperm, during artificial insemination
  , into the uterus
• administration of
  volatile anesthetic agents, and other breathing gases into the lungs using a tracheal tube
• subcutaneous administration of insulin or other medications, with the use of an infusion set and insulin pump

History

Ancient inventors

Ancient Chinese used onion stalks, the Romans, Hindus, and Greeks used tubes of wood or precious metals.^[11]

The ancient Egyptians created catheters from reeds.

Modern

The earliest invention of the flexible catheter was during the 18th century.^[12] Extending his inventiveness to his family's medical problems, Benjamin Franklin invented the flexible catheter in 1752 when his brother John suffered from bladder stones. Franklin's catheter was made of metal with segments hinged together with a wire enclosed to provide rigidity during insertion.^[13][14]

According to a footnote in his letter in Volume 4 of the Papers of Benjamin Franklin (1959), Franklin credits Francesco Roncelli-Pardino from 1720 as the inventor of a flexible catheter. In fact, Franklin claims the flexible catheter may have been designed even earlier.^[15]

An early modern application of the catheter was employed by Claude Bernard for the purpose of cardiac catheterization in 1844. The procedure involved entering a horse's ventricles via the jugular vein and carotid artery.^[16]

In 1929, Werner Forssman first performed central venous catheterization,^[17] work which led to the development of cardiac catherization as a treatment, for which he, André F. Cournand and Dickinson W. Richards would win the Nobel Prize for Medicine in 1959.^[18] Central venous catheterization allows for continuous administration of medications, fluids and blood products to a large vein, particularly in critically ill patients.^[17] Cardiac catheterization is the insertion of a catheter into one of the chambers of the heart, which is used for imaging, diagnosis, and the placement of devices such as stents.^[19]

Other reusable catheters consisted of red rubber tubes. Although sterilized prior to reuse, they still posed a high risk of infection and often led to the spread of disease.[22]^: 142

To prevent

Materials

Urinary catheters

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

]

Catheters used in interventional procedures

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.

Interventional procedures

Diagnostic catheters

There are various catheters used in

Balloon catheters

There are also balloon catheters used in angioplasty procedures such as plain balloon catheters that is useful in passing tight vessel stenosis, drug coated balloons that contains paclitaxel on the surface to prevent smooth muscle cells proliferation of the vessel walls, thus reducing the likehood of vessel blockage in the future, high pressure balloons that can open stubborn vessel stenoses in veins and arteriovenous fistula, and cutting balloon angioplasty that contains 3 to 4 small blades on its surface (endotomes) that helps to control the distribution of balloon dilatation more uniformly and cut through resistant stenosis due to fibrous scar tissue.^[34]

Dialysis catheters

There is no difference in achieving adequacy of blood flow, period of catheter usage, infection, and thromboembolism risk whether the dialysis catheter has step-tip, split-tip, or symmetrical tip.^[35] Palidrome catheter is superior to Permcath catheter in terms of maximum blood flow, dialysis adequacy, and annual patency rate. Similar to Permcath, Palidrome catheter has high infection and thromboembolism rate.^[36]

Adverse effects

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.

See also

• Cannula
• Foley catheter
• French catheter scale
• Gastrostomy
• G-Tube
• Jejunostomy
• Stent
• Catheter lock solution

References

• Millward, Steven F. (September 2000). "Percutaneous Nephrostomy: A Practical Approach". Journal of Vascular and Interventional Radiology. 11 (8): 955–964.
  PMID 10997456
  .

External links

Wikimedia Commons has media related to Catheters.

Look up catheter in Wiktionary, the free dictionary.