IV cannulae and giving sets Flashcards
Identify the different parts of a needle
History of IV cannulation: early methods
- 1845: Francis Rynd designed a hollow needle, allowing him to inject drugs
- 1853: Charles Pravaz developed the first practical metal syringe
- 1933: Baxter Travenol Company marketed the first IV solutions in vacuum bottles, which reduced microbial growth and pyrogens
- 1950s: plastic tubing replaced rubber tubing
- 1970s: plastic bags introduced, to reduce the risk of air embolism from air venting in glass bottles
History of IV cannulation: mid-twentieth century development
- 1950: David Massa developed a catheter which could be direclty threaded into a vessel after venupuncture with a needle. Similar to an epidural needle
- 1964: Angiocath introduced: disposable, made of PVC, had a hypodermic-style needle, flashback chamber and a flow control plug
- 1969: Teflon used, reducing the stickness of the canular
- 1983: first polyurethane over-the-needle cannula. Polyurethane is less traumatic to veins, decreased phlebitis and blood clotting in cannulae lumens
Features of modern IV cannulae:
* Ported IVCs
* Straight IVCs
* Safety catheters
* Integrated devices
* New closed IVC
- Ported IVCs have integrated ports which allow easy bolus administration, large wings for gripping, and a luer lock cap
- Straight IVCs are non ported, may come with or without wings, require added attachments to administer bolus medication, no luer lock
- Safety catheters are engineered to prevent needle stick injuries and blood exposure - passive devices (safety mechanism activated during routine performance of procedure) vs active (which require user to deploy point-protection mechanism
- Integrated devices have fixed addition of extension tubing to a standard device: protects against blood exposure, allows for eash bolus administration and remote manipulation of the line
- New closed IVCs: closed, needleless access systems that may offer better protection against bacterial exposure than conventional ‘open’ ports, as well as reduced risk of blood exposure
Benefits of new closed IVCs compared to classic peripheral IVCs
- No blood contact with clinician
- Needleless access system -> reduced needle stick injuries
- No exposure to disposed sharps due to needlepoint protection
Ideal design features of an intravenous cannula
- Rapid, reliable blood flashback (notched needles provide earliest flashback)
- Clear visibility of puncture site
- Minimal pain and discomfort to the patient (sharpness and geometry of needle tip, cannula gaugue, type of plastic)
- Minimal infection and thrombotic risks (cannula material)
- Dynamic softening of the cannula in the vein (some cannula materials change their stiffness after some time at body temp -> less likely to cause phlebitis, kink or obstruct)
- Minimal risks to the operator (e.g. needle stick, blood exposure)
- Multilumen needle-less ports access (simulatenous administration of number of therapies)
- Difficult to snag and easy to dress (ideally would be completly flat, allowing dressing to cover it smoothly - less likely to catch on objects, less friction of external catheter body on skin)
‘Gauge’: definition
‘Gauge’ (G) is used to describe the external diameter of the intravascular part of a catheter.
The number of needles of that size that would fit into a cylinder that is 25mm (1 inch) wide
What determines the flow rate through a cannula
Resistance to flow is determined by the Hagan-Poiseuille equation, therefore key determinants of flow of liquid through a cannula:
* Gauge size i.e. radius of tube (to the power 4)
* Cannula length
* Viscoscity of the infusing fluid (i.e. flow of water»_space; blood)
* Pressure of the infusion
* Blood pressure of the patient (to a small degree)
Note that flow rates are stated on the back of catheter packaging in ml/min, but these are ideal, determined by in-vitro gravity studies using water or saline. In-vivo flow rates are slower becuase of resistance in veins (which is highly variable) and viscoscity of fluids. Flow rates stated also vary between different manufacturers
What is the length the catheter for cannulas of the following gauges (BD Venflon 2 catheter)
14, 16, 17, 18, 20, 22
14-18: 45mm
20: 32mm
22: 25
Flow rates of water, plasma and blood through cannulas of 14, 16, 17, 18, 20, 22G
Note that flow rate of water > plasma > blood
Flow rates through 14G are just under 10x higher than flow rates through 22G
What are the recommended uses for cannulas of
12G, 14G, 16G, 17G, 18G, 20G, 22G, 24G
12G: major resuscitation
14, 16G: high volume transfusions, theatre or emergency for operative procedures
17, 18, 20G: IV fluid therapy, blood transfusion, medications (20G)
22, 24G: medications, paediatrics
What size of cannula will minimise trauma to the vein
Small diameter, short length
Adult giving set: dimensions, components, difference for fluid vs blood giving sets, drip rates
- Usually clear plastic tube 175cm in length, 4mm internal diameter
- One end designed for insertion into fluid bag, other attached to intravascular cannula with luer lock connection. Rubber injection site at patients end allows for direct injection (use 21-23G needles)
- Flow controller determines the drip rate: 20 drops of clear fluid =1ml, 15 drops of blood = 1ml
- Some designs have a 15 micron filter at bottom of fluid chamber to stop air entering
Giving sets used to administer blood also have
* Filter with mesh of 150-200 microns
* Fluid chamber with a ball float
Paediatric giving set: differences from adult, drop sizes/drip rates
In addition to basic principles of adult giving sets:
* Burette (30-200ml) in 1ml divisions is used to measure the volume of fluid used to improve accuracy. Has a filter, air inlet and injection site on top, and flap/ball valve at the bottom to prevent air entry when the burette is entry
* Two flow controllers: one between the fluid bag and burette and used to fill the burette, second between the burette and the patient to control the drip rate
* Injection site close to the patient to reduce dead space
* Drop size is 60 drops per 1ml of clear fluid. Note burette with drop size similar to adults (15drops/ml) used for blood transfusion
What is the rate of bacteraemia with IV cannula insertion? What are the most commonly isolated organisms from intravenous cannulae
- 1/3000 cannulae
- Coagulase negative staphylococci (35%), staph aureus (25%, and MRSA accounts for 40-45% of staph aureus infections)
What actions to take for signs of infection and peripheral phlebitis
0: observe
1-2: remove and replace cannula
3: remove, send tip for culture, treat
4: remove, sent tip for culture, treat, clinical incidence form
i.e. induration, pus or palpable venous cord above 3cm are indications to send tip
