Editing Cannula (section)

=== Intravenous cannulation ===
{{see also|Peripheral venous catheter}}
[[File:Venflon intravenous cannula 2.jpeg|thumb|Intravenous cannula]]
[[File:Cannula A.jpg|thumb|Flexile - it is inserted into a vein, and a transfusion or dropper, for example, is attached to the cannula.]]
A [[Intravenous therapy|venous]] cannula is inserted into a vein, primarily for the administration of intravenous fluids, for obtaining blood samples and for administering medicines. An [[Arterial catheter|arterial cannula]] is inserted into an artery, commonly the radial artery, and is used during major operations and in critical care areas to measure beat-to-beat blood pressure and to draw repeated blood samples. Insertion of the venous cannula can be a painful procedure that can lead to anxiety and stress. Use of a [[vapocoolant]] (cold spray) immediately before cannulation reduces pain during the procedure, without increasing the difficulty of cannulation.<ref>{{cite journal|last1=Griffith|first1=Rebecca J|last2=Jordan|first2=Vanessa|last3=Herd|first3=David|last4=Reed|first4=Peter W|last5=Dalziel|first5=Stuart R|title=Vapocoolants (cold spray) for pain treatment during intravenous cannulation|journal=Cochrane Database of Systematic Reviews|date=26 April 2016|doi=10.1002/14651858.cd009484.pub2|language=en|pmid=27113639|volume=2016|issue=4 |pages=CD009484|pmc=8666144 |url=http://espace.library.uq.edu.au/view/UQ:387354/UQ387354_OA.pdf}}</ref>

Complications may arise in the vein as a result of the cannulation procedure, the four main groups of complication are:

* [[hematoma]]: a collection of blood, which can result from failure to puncture the vein when the cannula is inserted or when the cannula is removed. The selection of an appropriate vein and gently applying pressure slightly above the insertion point on removal of the cannula may prevent this.
* [[infiltration (medical)|infiltration]]: when infusate enters the subcutaneous tissue instead of the vein. To prevent this, a cannula with accurate trim distances may be used. It is essential to fix the cannula in place firmly.
* [[embolism]]: this can be caused by air, a [[thrombus]], or fragment of a catheter breaking off and entering the venous system. It can cause a [[pulmonary embolism]]. Air emboli can be avoided by making sure that there is no air in the system. A thromboembolism can be avoided by using a smaller cannula.
* [[phlebitis]]: an inflammation of the vein resulting from mechanical or chemical irritation or from an infection. Phlebitis can be avoided by carefully choosing the site for cannulation and by checking the type of infusate used.