Central lines Flashcards
What is a central line and what’s it used for?
A central line is a large bore cannula or catheter inserted into one of the larger veins in the body where the tip of the cannula may lie either in the superior or inferior vena cava or right atrium
Why might we want to measure a patients CVP (central venous pressure)?
It indicates mean right atrial pressure and is frequently used as an estimate of right ventricular preload. The CVP does not measure blood volume directly, although it is often used to estimate this.
What are the possible complications associated with the insertion of a central line?
- Puncturing the apex of the lung that is superior to the clavicle leading to a pneumothorax
- Puncturing a major vessel leading to a haemothorax
- Accidentally cannulating a large artery
- Damage to the thoracic duct if placing line on left
- Introducing air into the circulation whilst inserting the line and causing an air embolism
- If inserted under un-sterile conditions then introducing infection to a major blood vessel and into the blood stream (even in sterile conditions this is a risk)
- Risk of damage to anomalous venous valves which may result in thrombus formation and the risk of a thrombus
Why might we want to measure a patients CVP (central venous pressure)?
The CVP indicates the mean right atrial pressure and is frequently used as an estimate of right ventricular preload and the function of the right atrium and return to heart.
A low CVP = venous return to heart is less than it should be, can occur in hypovolaemic shock or dehydration
A high CVP = right heart failure
CVP is normally in the range of 0 to 8 cm H2O
Where do we usually insert central lines into?
Central lines are usually inserted into the internal jugular vein or subclavian vein. Preferably on the right side as it’s not got as far to travel to heart as left does and could damage the thoracic duct.
Less commonly they are also inserted into the femoral vein and extended jugular vein.
How do you insert a central line?
Central lines are inserted into the patient when they are lying down facing away from the site of insertion to help identification of the vein. Most guidelines now recommend that ultrasound is used to ensure that the needle is placed correctly and not into the internal carotid or subclavian artery.
After vein is found a guide wire is passed through the needle into the vein and then the cannula or catheter is passed over the guide wires into the vein where the wire can then be removed.
What kind of central line is mostly used?
Multi lumen central lines as it allows us to have multiple cannula and connections running through one larger sheath allowing for different fluids and drugs to be given at the same time while the CVP is being measured from a different connection.
How long should we have a central line inserted in for?
They should be inserted for the shortest time as possible as they are uncomfortable for the patient and there is a higher risk of introducing infection into the bloodstream the longer they are left there
If access is needed for a longer period of time then we use a special kind of cannula such as one with a port placed under the skin to minimise infection.
