Vessel identification and selection identification
Identification
- A vein is a non-pulsatile vessel and easily compresses with the ultrasound probe.
- An artery is a pulsatile structure that is difficult to compress with the ultrasound probe.
Once the vessel has been accessed, the practitioner must observe the flow of blood from the needle to ascertain if the vessel is a vein or an artery. Blood flow from an artery will pulsate, be excessive and may be bright red in colour.
Vein selection
The veins of choice for the placement of a midline when using ultrasound guidance are the basilic and the brachial veins in the upper arm. The cephalic vein should only be used if the aforementioned veins are unsuitable. Midlines should not be placed in a small cephalic vein. Care must be taken when cannulating. If veins are easily identified by simple examination of the patient’s arm then ultrasound may not be required.
Patient preparation and consent
An explanation of the following must be provided prior to obtaining informed consent:
- reason for midline and available alternatives
- explanation of procedure
- time frame of the procedure
- aftercare
- potential complications.
All patients must be verbally consented for midline insertion. If a patient lacks capacity for consent an adults with incapacity form must be completed.
Patients on warfarin therapy should have an INR <3.0 prior to placement. If patient parameters fall below these criteria discuss plan with medical team.
Infection control
Ideally, a dedicated procedure room should always be adopted.
All lines must be placed using strict maximal barrier precautions.
This includes:
- Cleansing the site with chlorhexidine 2% in 70% alcohol (Chloraprep) using a friction scrub with a single use applicator for 3mls for at least 30 seconds in an area of approximately 6cm squared around the proposed exit site and allowed to dry for at least 30 seconds.
- In the event of chlorhexidine allergy, use 70% alcoholic povidone iodine for skin cleansing.
- Full body draping.
- Thorough hand-washing using a surgical scrub technique and drying with sterile towels.
- Wearing hat, mask, sterile gloves and eye protection.
- The use of sterile equipment placed onto a sterile field.
Venepuncture
When inserting the needle into the vein, the probe can be held perpendicular (across) or longitudinal (along) the vein. The needle should be placed slowly into the skin. When the needle approaches the vessel target, the anterior wall will indent. A swift insertion into the vein at this time will prevent excessive collapse of the vein wall. Once venipuncture has taken place, the vessel returns to normal shape. Always observe for a blood return from the needle or cannula.
Inadvertent arterial puncture
The inadvertent puncture of an artery can be avoided by:
- Recognising the position and location of all main and aberrant arteries.
- If the vein accessed is close to an artery, visualize and identify brachial artery with ultrasound.
- During insertion, if the artery is punctured (pulsatile and excessive flow). Remove needle immediately and apply pressure.
- Please note: If line has been placed and brachial vein used and excessive bleeding is noted, blood gas analysis or doppler ultrasound should be considered.
- In the event of inadvertent introducer or line placement in an artery, leave device in place, secure device and seek advice from the medical team.
Inadvertent nerve damage
The inadvertent damage of a nerve can be avoided by:
- Possessing the knowledge of anatomic location of the nerve.
- If brachial vein to be accessed for midline insertion, visualize and identify median nerve with ultrasound.
- During insertion, if the patient reports sudden “electric shock” like pain shooting down the arm or has involuntary and rapid movement of the arm, when nerve is touched. Remove the needle immediately.