Venous access is an essential prerequisite for safe anaesthesia and is as much required in several other clinical situations. It can be peripheral, central or peripherally inserted central venous cannulation.
Peripheral venous access can be easy, difficult or rarely impossible. Anaesthesiologist has to establish intravenous access under all circumstances, both in elective and emergency surgery. Importance of venous access, general principles and techniques are described:
Importance of venous access
- Free flowing, easily accessible intravenous line (IV line) is the life line for patients who require anaesthesia, emergency medical care, intensive care or intravenous medications.
- IV line is required for administration of anaesthetic drugs (a significant number of anaesthetic drugs are always administered IV), fluids (crystalloids and colloids) and blood. Drugs are given as bolus or as infusion.
- When there is a severe hypotension due to acute and massive blood loss (which can sometimes take place within a matter of minutes),anaphylaxis, central neuraxial blockade or transfusion mismatch, rapid administration of fluids and blood could be lifesaving.
Principles of peripheral venous access
- Establish a secure venous access with a wide bore cannula at a site which is easily accessible to the anaesthesiologist throughout the procedure.
- For adult patients, ideally, 18G (green) should be the minimal standard size, irrespective of the severity of surgery. If surgery is a major one with potential for significant blood loss or fluid shift and if the vein is prominent, a 16G (gray) or 14G (orange) cannula can be chosen. Larger the inner diameter of the cannula, faster the infusion rate.
- For older cchildren, 20G (pink) and for smaller children 22G (blue) is the size of the cannula. 24G (yellow) cannula is not very reliable, because of short length rendering it more prone for dislodgement. 26G (violet) is available for small and premature babies also available.
- The size of cannula matters a lot. The flow rate is inversely proportion to the size of the cannula. Lager the size and larger the diameter, higher the flow rate. Though rate is inversely related to length, it does not matter much in case of peripheral venous cannula.
- Usually, non-dominant upper limb is preferred. Site should be as distal as possible (commonly on the dorsal of the hand), avoiding the joint and away from the artery.
- The venous segment chosen should be straight and without valves.
- Change in the site or limb may be required for specific surgical procedures or due to associated comorbid conditions.
- A second cannula, preferably a 16 or even 14G cannula may be inserted immediately after the induction of anaesthesia, before the surgical incision.
- Often establishing an additional venous access becomes progressively difficult as the surgery proceeds, due to blood loss, vasoconstriction, hypothermia, inadequate lighting etc.
- Use of extension lines may be required.
- Avoid cannulations in the following areas a) areas of flexion b) previous catheter insertion site c) presence of bruise or phlebitis d) presence of A-V fistula e) previous lymph node dissection or mastectomy f) stroke g) cellulitis
Steps of IV cannulation
- explain to the patient
- select the limb
- select the site
- make the vein prominent
- use disinfectant and clean the area
- inject local anesthesia with 2% lignocaine
- insert the cannula and watch for blood in the hub
- push the cannula for a few millimetres and stabilize
- withdraw the needle few millimetres into the cannula, without pulling it out completely and simultaneously push the catheter and withdraw the needle
- connect the appropriate intravenous fluid
- fix the cannula firmly
- Document the procedure and appropriate instructions
Difficult venous cannulation
- Not infrequently, the anaesthesiologist encounters patients in whom the venous access becomes extremely difficult if not impossible. These patients/clinical conditions include
- Patients for emergency surgery
- dehydration: prolonged fasting, fluid loss
- hypotension: blood loss
- post chemotherapy and radiotherapy
- previous multiple cannulation as in patients who had multiple surgeries, intensive care unit or prolonged use of antibiotics
- children with congenital malformations
- contracture and trauma
Management of these situations include,
- Search for the veins which have not been utilized carefully. This requires patience and diligence and often successful. Look for veins in locations which are not often selected by the nurses or other medical practitioners.
- Lower limb veins, especially saphenous vein is often available. It’s easier after induction of anaesthesia and painful in awake patients. Lower limb veins are very useful as the second or additional cannula in major surgeries, especially if the procedure is in the upper part of the body.
- Use of smaller size cannula, like 20G, before induction and placement of additional cannula after induction when the veins become more prominent.
Use of extension lines, 3 way stopcocks and maintenance of lines and cannula
- Extension lines are required when the access to the venous cannula is difficult due to its location, surgical position or procedure. Use of an extension provides access to the circulation through a 3 way connection. Different lengths of extension are available and include 10cm, 15cm and 100 cm. Longer the extension, slower the speed of infusion.
- If a 3 way stopcock is used, it should be flushed before the use so that there is no dead space left. Sometimes, an additional infusion is attached to the 3 way, but this slows down the rate of primary fluid being administered.
- The intravenous lines which are attached to the cannula needs to be flushed and the chamber filled before connecting to cannula. When there are more than one lines to a patient, each should be labelled properly and documented. This becomes all the more important when patient is receiving multiple infusions and is in an unstable condition. Also, the intravenous connection should not be confused with the Arterial line flush which should also be clearly labelled.
- If a cannula is kept without any fluid in the postoperative period, it should be flushed with saline or very small dose of heparin (hemlock), to maintain the potency. According to NABH standards all cannulas should be flushed with saline before and after antibiotics injection.
Newer intravenous cannula designs
- The traditional intravenous cannula come with or without (Jelco cannula) injection ports and the side wings. The ones without ports are also used for arterial pressure monitoring.
- Needle stick injury is one of the important professional hazards for the anaesthesiologist. Hence, it is recommended to avoid re insertion of cannula into the catheter and also to properly dispose the needle.
- Newer cannula come with an unique needle design wherein the needle will automatically gets distorted loosing it’s sharpness, the movement it is withdrawn from the cannula. It cannot be re inserted. Eg Venflon Pro Safety shielded catheters.
- Latex free material. vialon is one of them.
Complications with Intravenous cannula
- Counter puncture chasing extravasation and hematoma.
- Accidental arterial placement. Easy to detect due to the high pressure with which the flow comes out in case of artery. One has to be. Ore careful when a cannula is inserted in a location which is known to have an artery, like radial artery near the wrist.
- Thrombophlebitis is related to the size of the cannula, duration for which it is left in place, maintenance of the potency and also the injection if certain drugs.
- Cannula blockade
Peripheral venous access in children
Principles are similar to the adult venous access as described above.
Main differences in a children are,
- Technically may be more difficult requiring expertise
- Small veins permitting placement of small size cannula
- Visibility or identification of the vein can be difficult
- Trans illumination can be helpful and commonly used
- Maintenance of the cannula is more difficult
- Since the child can’t understand, it can’t cooperate. Hence awake cannulation is more difficult
How to achieve cannulation in a child,
- Try to establish rapport with the child and parents
- Identify the site clearly
- Hope the child comfortably without shouting or threatening
- Stabilize the hand firms
- Use Trans illumination with a “cold light” source. Though it is called cold light, one has to be extremely careful to prevent burns which can readily occur. It is safer to cover it with a layer of gauze and use for as minimum time as possible.
NABH guidelines for maintenance of intravenous line
- Inspect the site every 6h for redness, swelling and pain. If present, change the site
- Keep the ports always closed
- Flush the line with heparin saline, 6h and after every injection
- Inject saline (S) before and after antibiotics (A). S-A-S sequence
- Change the infusion set every 24-48h