IV access Flashcards
What are the types of cannula?
Over the needle ‘Through the needle’ • Large bore insertion needle • Cannula passed through the needle Peel away – place through an over the needle cannula Seldinger/over the wire cannulae
What are the biological properties of a perfect cannula?
Non-irritant - provokes minimal inflammatory response
Non-carcinogenic - low tendency to cause neoplasia (cancer)
Non-thrombogenic - low tendency to cause blood clotting
Non-toxic
Resists microbial adhesion
Resists biofilm deposition
What are the physical properties of a perfect cannula?
High tensile strength
Resists compression - maintains patent lumen
Optimum flexibility
Low friction coefficient
Dimensional stability
Tolerates physical sterilisation methods (e.g. heat, steam, irradiation)
Ease of fabrication (e.g. heat forming or welding)
Non-permeable (water, gases, solvents)
Radiopacity (ability to image catheter with X-rays)
What are the chemical properties of a perfect cannula?
Absence of leachable additives (e.g. catalysts and plasticisers)
Stable during storage
Stable on chemical sterilisation
Stable on implantation (non-biodegradable)
Permits adhesives in fabrication
Accepts surface coatings (e.g. hydrogel, antithrombotic, antibacterial)
Compatibility with chemical compounds and solvents
MRI compatible
Where can you place a cannula?
The cephalic vein
Saphenous veins - medial hindlimb
Jugular
Auricular
What size cannula will you use in small animals?
- 22g (blue) for v small patients
- 20g (pink) or greater for most patients including cats
- > 20kg dogs use 18g
- Very large dogs use 16g or 14g
How long do cannula last in patients?
Check cannula regularly and flush q 6 hours with heparinised saline
Normal cannulae can be maintained for up to 3 days after which they should be replaced
What problems can occur with cannula?
Extravasation Thrombosis (where do the thrombi occur) Thrombophlebitis Infection Emboli (air, catheter) Exsanguination
When would you use an intraosseous catheter?
- Patients with inaccessible peripheral vessels
- Or those in circulatory collapse needing fluids, blood products, or drugs -provides quick access via bone marrow sinusoids and medullary venous channels
- Allows rapid delivery of fluids (up to 11 ml/min) to neonates, small animals, and birds
Define Ambulatory infusion
An animal is freely moving without need for a tether to connect with the catheter. This is normally only possible with larger animals that can be fitted with jackets to carry an infusion pump and compound reservoir. Totally implanted pumps can sometimes be used in rodents but have size limitations
Define atraumatic
Minimal tissue injury is caused during the procedure
Define biocompatibility
Good toleration of implants by animal tissues after implantation
Define biofilm
A coating which develops on implanted materials derived from the animal’s own tissue fluids and cells
Define Catheter/cannula
Flexible tube inserted into body cavities or organs for medical or experimental procedures
Define Dehiscence
Bursting open or splitting along natural or sutured lines.
