Cannula Health Dictionary

The puncture by hollow needle or TROCAR and CANNULA of any body cavity (e.g. abdominal, pleural, pericardial), for tapping or aspirating ?uid. (See ASPIRATION.)... paracentesis

An instrument provided with a sharp three-sided point ?tted inside a tube or cannula, and used for puncturing cavities of the body in which ?uid has collected.... trocar

The general term for any one of a group of HORMONES which govern the development of the sexual organs and the secondary sexual characteristics of the male. TESTOSTERONE, the androgenic hormone formed in the interstitial cells of the testis (see TESTICLE), controls the development and maintenance of the male sex organs and secondary sex characteristics. In small doses it increases the number of spermatozoa (see SPERMATOZOON) produced, but in large doses it inhibits the gonadotrophic activity of the anterior PITUITARY GLAND and suppresses the formation of the spermatozoa. It is both androgenic and anabolic in action. The anabolic e?ect includes the ability to stimulate protein synthesis and to diminish the catabolism of amino acids, and this is associated with retention of nitrogen, potassium, phosphorus and calcium. Doses in excess of 10 mg daily to the female may produce VIRILISM.

Unconjugated testosterone is rarely used clinically because its derivatives have a more powerful and prolonged e?ect, and because testosterone itself requires implantation into the subcutaneous fat using a trocar and cannula for maximum therapeutic bene?t. Testosterone propionate is prepared in an oily solution, as it is insoluble in water; it is e?ective for three days and is therefore administered intramuscularly twice weekly. Testosterone phenyl-propionate is a long-acting microcrystalline preparation which, when given by intramuscular or subcutaneous injection, is e?ective for four weeks. Testosterone enantate is another long-acting intramuscular preparation. Mesterolone is an e?ective oral androgen and is less hepatoxic: it does not inhibit pituitary gonadotrophic production and hence spermatogenesis is unimpaired. Testosterone undecanoate is also an e?ective oral form.... androgen

A visualising technique enabling the operator to examine the internal organs with the minimum of disturbance or damage to the tissues. The procedure has transformed the management of, for example, gastrointestinal disease. In chest disease, ?breoptic bronchoscopy has now replaced the rigid wide-bore metal tube which was previously used for examination of the tracheo-bronchial tree.

The principle of ?breoptics in medicine is that a light from a cold light source passes down a bundle of quartz ?bres in the endoscope to illuminate the lumen of the gastrointestinal tract or the bronchi. The re?ected light is returned to the observer’s eye via the image bundle which may contain up to 20,000 ?bres. The tip of the instrument can be angulated in both directions, and ?ngertip controls are provided for suction, air insu?ation and for water injection to clear the lens or the mucosa. The oesophagus, stomach and duodenum can be visualised; furthermore, visualisation of the pancreatic duct and direct endoscopic cannulation is now possible, as is visualisation of the bile duct. Fibreoptic colonoscopy can visualise the entire length of the colon and it is now possible to biopsy polyps or suspected carcinomas and to perform polypectomy.

The ?exible smaller ?breoptic bronchoscope has many advantages over the rigid tube, extending the range of view to all segmental bronchi and enabling biopsy of pulmonary parenchyma. Biopsy forceps can be directed well beyond the tip of the bronchoscope itself, and the more ?exible ?breoptic instrument causes less discomfort to the patient.

Fibreoptic laparoscopy is a valuable technique that allows the direct vizualisation of the abdominal contents: for example, the female pelvic organs, in order to detect the presence of suspected lesions (and, in certain cases, e?ect their subsequent removal); check on the development and position of the fetus; and test the patency of the Fallopian tubes.

(See also ENDOSCOPE; BRONCHOSCOPE; LARYNGOSCOPE; LAPAROSCOPE; COLONOSCOPE.)... fibreoptic endoscopy

Also known as plasmapheresis. The removal of the circulating PLASMA from the patient. It is done by removing blood from a patient and returning the red cells with a plasma expander. The plasma exchange is carried out through an in-dwelling CANNULA in the femoral vein, and the red cells and plasma are separated by a hemonetics separator. Usually a sequence of three or four sessions is undertaken, at each of which 2–3 litres of plasma are removed. The lost plasma can either be replaced by human serum albumin (see ALBUMINS) or a plasma expander.

In autoimmune disorders, disease is due to damage wrought by circulating ANTIBODIES or sensitised lymphocytes (see LYMPHOCYTE). If the disease is due to circulating humoral antibodies, removal of these antibodies from the body should theoretically relieve the disorder. This is the principle on which plasma exchange was used in the management of autoimmune diseases due to circulating antibodies. Such disorders include Goodpasture’s syndrome, SYSTEMIC LUPUS ERYTHEMATOSUS (SLE) and MYASTHENIA GRAVIS. One of the problems in the use of plasma exchange in the treatment of such diseases is that the body responds to the removal of an antibody from the circulation by enhanced production of that antibody by the immune system. It is therefore necessary to suppress this homeostatic response with cytotoxic drugs such as AZATHIOPRINE. Nevertheless, remissions can be achieved in autoimmune diseases due to circulating antibodies by the process of plasma exchange.... plasma exchange

The slow introduction, over hours or days, of fluid into the bloodstream through a cannula (thin plastic tube) inserted into a vein.

Commonly known as a drip, an intravenous injection is used to give blood (see blood transfusion) or, more commonly, fluids and essential salts.

Other uses include providing nutrients to people unable to digest food (see feeding, artificial) and the administration of certain drugs.... intravenous infusion

The process of supplying a person with oxygen-enriched air to relieve severe hypoxia (inadequate oxygen in body tissues). The oxygen is usually delivered through a face-mask or a nasal cannula (a length of narrow plastic tubing with two prongs that are inserted into the nostrils). Piped oxygen is used in hospitals; oxygen in cylinders can be used at home for acute attacks of hypoxia, such as those occurring in severe asthma. Long-term therapy for people with persistent hypoxia may involve the use of an oxygen concentrator.

(See also hyperbaric oxygen treatment.)... oxygen therapy

Analysis of a sample of blood to give information on its cells and proteins and any of the chemicals, antigens, antibodies, and gases that it carries. Such tests can be used to check on the health of major organs, as well as on respiratory function, hormonal balance, the immune system, and metabolism. Blood tests may look at numbers, shape, size, and appearance of blood cells and assess the function of clotting factors. The most important tests are blood count and blood group tests if transfusion is needed. Biochemical tests measure chemicals in the blood (see acid–base balance; kidney function tests; liver function tests). Microbiological tests (see immunoassay) look for microorganisms that are in the blood, as

in septicaemia. Microbiology also looks for antibodies in the blood, which may confirm immunity to an infection. blood transfusion The infusion of large volumes of blood or blood products directly into the bloodstream to remedy severe blood loss or to correct chronic anaemia. In an exchange transfusion, nearly all of the recipient’s blood is replaced by donor blood. Before a transfusion, a sample of the recipient’s blood is taken to identify the blood groups, and it is matched with suitable donor blood. The donor blood is transfused into an arm vein through a plastic cannula. Usually, each unit (about 500 ml) of blood is given over 1–4 hours; in an emergency, 500 ml may be given in a couple of minutes. The blood pressure, temperature, and pulse are monitored during the procedure.

If mismatched blood is accidentally introduced into the circulation, antibodies in the recipient’s blood may cause donor cells to burst, leading to shock or kidney failure. Less severe reactions can produce fever, chills, or a rash. Reactions can also occur as a result of an allergy to transfused blood components. All

blood used for transfusion is carefully screened for a number of infectious agents, including HIV (the AIDS virus) and hepatitis B and hepatitis C.

In elderly or severely anaemic patients, transfusion can overload the circulation, leading to heart failure.

In patients with chronic anaemia who need regular transfusion over many years, excess iron may accumulate (haemosiderosis) and damage organs such as the heart, liver, and pancreas.

Treatment with desferrioxamine to remove excess iron may be needed.... blood tests

A common procedure in which a vein, usually in the forearm, is pierced with a needle to inject fluid or withdraw blood. A tourniquet is used to swell the veins, and a sterile needle is inserted. A syringe is attached to the needle if blood is to be taken or medication injected. For intravenous infusion, a cannula (tube) is inserted via the needle. After the fluid has been injected or withdrawn, the needle or cannula is removed. The area is then covered and pressure applied to stop any bleeding. The procedure is not usually painful but may cause some discomfort.... venepuncture

the use of enteral feeding tubes or cannulas to administer nutrients and fluids directly into the gastrointestinal tract or bloodstream when the oral route cannot be used owing to disability or disease. When other intensive treatments are judged *futile, artificial nutrition and hydration are considered *extraordinary means of prolonging life in patients who have no prospect of recovery. It is permissible to withdraw such treatment when it is no longer in the patient’s interests and when the primary intention is not to kill the patient, although death is foreseen (see doctrine of double effect). In cases of patients in a *persistent vegetative state in England and Wales, the matter must be referred to the courts following the case of Tony Bland. Where food and water are withdrawn it is still considered important to moisten the patient’s lips and to keep him or her comfortable until death.... artificial nutrition and hydration

a disease associated with diffuse atherosclerosis and sloughing of atheromatous plaques in the aorta and main renal arteries. This results in occlusion of smaller arteries and arterioles downstream within the kidney, with ischaemic and inflammatory reactions. This leads to the onset of renal impairment. Precipitating factors include invasive procedures with aortic cannulae, vascular surgery, and therapy with thrombolytics or anticoagulants. Less commonly the condition can occur spontaneously.... atheroembolic renal disease

(intravenous drip) n. apparatus for the continuous infusion (*transfusion) of blood, plasma, saline, glucose solution, or other fluid into a vein. The fluid flows under gravity from a suspended bottle through a *cannula inserted into the patient’s vein. The rate of flow can be adjusted according to the rate of drips seen in a transparent section of the tube, but many *infusions are now controlled by electronically regulated infusion pumps.... drip

a fine plastic cannula usually inserted into the subclavian vein in the neck to allow administration of drugs and repeated blood samples. The catheter is tunnelled for several centimetres beneath the skin to prevent infection entering the bloodstream. It is used most frequently in patients receiving long-term chemotherapy, particularly infusion regimes (e.g. fluorouracil).... hickman catheter

n. 1. see obturator muscle. 2. a wire or rod within a cannula or hollow needle for piercing tissues or fitting aspirating needles. 3. a removable prosthetic device that both closes a defect in the palate and also restores the dentition. The defect may result from removal of a tumour or, less commonly, be congenital, as in a cleft palate.... obturator

a method for introducing a catheter into a blood vessel or cavity. First, a needle is used to puncture the structure, then a *guidewire is passed through the needle. The needle is removed, and the catheter is introduced over the wire. The technique is used in angiography, cardiac catheterization, cannulation of large veins, and drainage of abscesses and other body cavities. [S. I. Seldinger (1921–98), Swedish radiologist]... seldinger technique

n. a technique for obtaining an emergency airway through the *cricothyroid membrane when standard airway techniques have failed. There are two main techniques. In needle cricothyroidotomy, a large-bore intravenous cannula is inserted directly through the membrane. Ventilation by this technique can only be through a high-pressure system, must only be performed by trained personnel, and must only continue for a maximum of 45 minutes. Damage to the lungs can ensue. In surgical cricothyroidotomy, a surgical hole is made in the membrane and a cuffed tube, similar to a short endotracheal tube (see intubation), is inserted directly. This affords much better airway protection.... cricothyroidotomy

(lymphography) n. X-ray examination of the lymphatic vessels and lymph nodes after a contrast medium has been injected into them (see angiography). Lymphatic vessels in the upper part of the foot are dissected and cannulated after injecting methylene blue into the web space to identify them. Then a viscous contrast medium (Lipiodol) is injected into them at a very slow rate. Its main uses are in the investigation of the extent and spread of cancer of the lymphatic system, the investigation of lymphoedema, and postoperative collection from lymphatic damage. Newer techniques involve injection of contrast medium directly into the lymph nodes (intranodal lymphangiography). Alternatively, the lymphatic system can be imaged using a gamma camera following the injection of a radioactive tracer. This examination has now largely been replaced by other *cross-sectional imaging techniques.... lymphangiography

(PD) a form of renal replacement therapy (see dialysis) that utilizes the peritoneum as the semipermeable membrane separating blood and *dialysate. Peritoneal dialysis can be given as a temporary and emergency treatment using a rigid percutaneous cannula to deliver fluid into the peritoneal cavity; this cannula usually needs removal and/or replacement within a few days. Alternatively, PD can be used as a chronic treatment, either in the form of chronic ambulatory peritoneal dialysis (see CAPD) or automated peritoneal dialysis (APD), in which case fluid delivery is through a soft silastic catheter that is tunnelled subcutaneously out of the peritoneal cavity and is designed to stay in place for years. In all cases, the dialysis fluid is left within the peritoneal cavity for a period of time during which substances in the bloodstream diffuse into the fluid according to their concentration gradient and the permeability of the peritoneal membrane.... peritoneal dialysis

n. a technique for X-ray examination of the salivary glands. A series of X-ray images is taken after introducing contrast medium through a cannula into the ducts of the *parotid or *submandibular glands in the mouth. It enables the presence of degenerative disease or stones blocking the ducts to be detected.... sialography

(amethocaine) n. a potent local anaesthetic applied to the skin before intravenous injections or the insertion of a cannula. It is also applied as eye drops before eye operations.... tetracaine

n. an operation to introduce a hollow needle (cannula) into one of the lateral ventricles (cavities) of the brain. This may be done to relieve raised intracranial pressure, to obtain cerebrospinal fluid from the ventricle for examination, or to introduce antibiotics or contrast material for X-ray examination.... ventriculostomy