Cannulation

Cannulation

Intravenous (IV) cannulation is a technique in which a cannula is placed inside a vein to provide venous access. Venous access allows sampling of blood, as well as administration of fluids, medications, parenteral nutrition, chemotherapy, and blood products.

 

Cannula Gauges

 

Cannulation Technique

  • Once all equipment has been prepared and hands are washed and covered with sterile gloves the tourniquet should be fastened round the client’s arm (either just above the elbow for an inner elbow cannula or just above the wrist for a lower cannula on the hand).
  • A few seconds should be left for the veins to become distended; the desired area should then be palpated for a bouncy, static vein. (a well felt vein is better than a visible vein)
  • Once desired area has been found, the area should be cleaned thoroughly using a chlorhexidine 2%/ Alcohol 70% wipes and allow 30 seconds to dry before cannulating Do not palpate the skin again after cleaning.
  • Then, discard the cannula needle sheath to expose the needle tip, unscrew the cap at the rear of the cannula and place it safely on the phlebotomy tray; you will need it later if you are not using a needle-free connector.
  • Using your non-dominant hand, gently grip the patient’s arm with your thumb to hold the skin taut and immobilise the underlying vein

Using your dominant hand, hold the Braun cannula with your thumb securing the plastic base of the needle so that it does not slide out of the cannula, and confidently puncture the skin at a shallow angle of no more than 30 degrees

Diagram G – B-Braun Cannula – Blue – 22G

  • Gently advance the needle until you pierce the vein and see a flashback of blood in the needle hub
  • Holding the needle steady, lower the cannula to further reduce its angle from the skin, and advance a further 1-2 mm to ensure that the tip of the cannula has entered the lumen of the vein along with the needle
  • Using the wings at the base of the cannula, advance the cannula over the needle while holding the needle still
  • If there is limited or no resistance, continue to advance the cannula while holding the needle still until the base of the cannula is right up against the insertion site, at which point the cannula should be flat against the skin
  • If instead you encounter resistance when advancing the cannula, then it is likely that the cannula is not in the lumen of the vein, in which case you should gently retract the cannula and insert a fresh cannula
  • Once you have fully advanced the cannula, carefully remove the tourniquet
  • With the thumb of the non-dominant hand, occlude the end of the cannula with gentle pressure as the needle is removed completely
  • Dispose of the needle quickly and safely in the sharps bin
  • Collect the cap from the phlebotomy tray and apply it to the back of the cannula to stem any bleeding, or apply a needle-free valve antiseptic wipes to clean around the site if there is any blood
  • Flush the cannula with 0.9% sodium chloride using the injection port on the top of the base; it should flow easily
  • If you are met with resistance when attempting to flush, the cannula is either not in the lumen of the vein, or the cannula is abutting a valve. Either way, the cannula should be recited
  • Dispose of all packaging, used wipes, and cotton wool swabs
  • Document when and where the cannula was sited

 

Consideration Points

If a cannulation attempt fails after cannula sheath has been advanced over the needle, the cannula should never be re-sheathed and should be discarded of in the sharps bin as it is unsafe for use. All failed attempt cannulas must be discarded into a sharps bin and a new one must be used for a re-attempt. Applying pressure over the site of a failed cannulation will minimise bruising and bleeding.

Monitoring Client

Once a cannula has been placed, it is important for the client to be monitored throughout their infusion, especially at their site of cannulation.

Things to look out for:

  • If any part of the administration set is wet there could be a leak, which may pose an infection risk
  • The presence of air bubbles in the line can present extreme danger to the patient
  • Kinks in the administration lines, for example, due to the patient’s position, may cause an occlusion
  • Look for discolouration or precipitation
  • Loose connections: finger tightness required
  • Ensure client is experiencing no pain, redness or swelling around the site
  • Ensure the cannula remains in the vein. Extravasation and infiltration of surrounding tissue could result if the cannula becomes dislodged
  • You must document that infusion monitoring has occurred

Risks of IV Cannulation

  • Bruising/haematoma: relatively common, particularly after failed or vigorous cannulation attempts
  • Infection of the cannulation site: cellulitis may arise around the insertion site, which in some cases may progress to systemic sepsis
  • Displacement (tissuing): the cannula may become dislodged from the vein; in which case you must remove it and site a new cannula
  • Extravasation: if the cannula has not been properly sited injected fluids or drugs may pool under the skin, which may be irritating to the patient and in some cases cause tissue necrosis
  • Thrombophlebitis: irritation and clotting of the vein at the cannula site requires removal of the cannula
  • Blockage: clots or collections of infusion products may occlude the cannula. In some cases, you can resolve this by flushing the cannula with normal saline, but it may be necessary to remove the cannula
  • Arterial puncture: detected by pulsatile blood flow into the cannula chamber and from the end of the cannula after the needle is removed. Arterial puncture may be intensely painful and lead to distal limb ischaemia. If this occurs you should remove the cannula immediately, remove the tourniquet and apply firm pressure to the site
  • Peripheral nerve injury: this is rare. Remove the cannula immediately if the patient develops paraesthesia or numbness near the cannula site.