Goose. Geese. Moose. Meese. Cannulas. Cannulae. Whatever!

Blood Extraction

Why throw away the first 10mL of blood when collecting it from an existing cannula? It’s because that portion is theoretically contaminated, such as by previous infusions.

Saline Flush

The purpose is, also theoretically, to keep the cannula open and working. Patent, as they say. That’s why this is recommended after giving IV medications or just periodically. Basically, after each use.

Not Water

Normal saline is injected, not water. This is because a pure water injection would lead to the water rushing into red blood cells, due to that trusty process of osmosis. This sudden water influx would make them explode.

Which, as you can imagine, would run counter to the usual hospital purpose of trying to heal people, not atomically bomb their bloodstream.

References

1. Blood collection from intravenous cannula. (2019). Retrieved from https://vitualis.wordpress.com/2006/05/15/blood-collection-from-intravenous-cannula/
2. Keogh, S., Flynn, J., Marsh, N., Mihala, G., Davies, K., & Rickard, C. (2016). Varied flushing frequency and volume to prevent peripheral intravenous catheter failure: a pilot, factorial randomised controlled trial in adult medical-surgical hospital patients. Trials, 17(1), 348. doi:10.1186/s13063-016-1470-6
3. Labos, C. (2019). Why can I taste saline and medications when they’re inserted into my IV?. Retrieved from https://www.mcgill.ca/oss/article/you-asked/why-can-i-taste-saline-when-its-injected-my-iv

If you like controversy, there is a One Nation Party in Australia.

But wouldn’t life be more interesting with a Cannulation Party? Make well-calculated intravenous access sites, not war.

The minutes would run something like this.

OFFICIAL MINUTES OF THE CANNULATION PARTY OF AUSTRALIA

Foreword

Cannulation means putting a tube into a vein to deliver substances. The tube stays in the patient for a period of time.

Venepuncture, equivalent to phlebotomy, means accessing a vein to draw blood. It involves sticking a needle into a patient but not leaving any in-dwelling devices.

Agenda

1. Discussion of cannulation
   1. Indications
   2. Contraindications
   3. Risks
   4. Procedure
2. Discussion of venepuncture
   1. Indications
   2. Contraindications
   3. Risks
   4. Procedure

Item 1.1: Cannulation Indications

• Rapid delivery of substances, such as fluid, antibiotics or contrast for imaging
• Not to draw blood, although blood can be taken when the cannula is first applied

Why not oral? A patient might ask you this. Cannulation is for situations where quick bloodstream access is desirable, such as in sepsis, and oral delivery is unlikely to have the necessary effect. For example, gut metabolism might be an issue.

Cannulation is relevant when repeated access is needed. It certainly beats jabbing an unfortunate patient countless times.

Item 1.2: Cannulation Contraindications

• Arteriovenous fistula
• Mastectomy, lymph node issues
• Trauma, burns, infection

For example, the standard procedure in cardiology is to use the patient’s left side, as the cardiologist approaches the patient from the right. This allows nursing staff convenient access to the patient’s left.

However, this can vary according to the patient’s situation; if the left arm has a contraindication, use the right one instead — unless that too has a contraindication.

Item 1.3: Cannulation Risks

• Primary risk is infection
• Secondary risk is haematoma

As with any procedure, other risks are imaginable. The main ones for cannulation are infection and, with a smaller chance, haematoma.

Importantly, sterile gloves are to be used during cannulation. As with any procedure, appropriate hand hygiene should be used throughout. For example, before and after touching a patient or before touching an aseptic field. If in doubt, it’s better to wash your hands too many times than not enough.

Even if there is no sign of infection, your hospital might have a maximum time for which a cannula can remain in a patient, such as 72 hours.

Item 1.4: Cannulation Procedure

1. Understand the indication
   1. Why is cannulation requested for this patient?
   2. What gauge cannula should be used?
   3. Does the patient have any contraindications?
   4. What site is most appropriate?
2. Gather equipment
   1. Bung
   2. Cannula
   3. Chlorhexidine and alcohol swab
   4. Dressing pack
      1. Includes needle, syringe, gauze and stickers
   5. Kidney dish
   6. Saline bottle
   7. Sterile gloves
   8. Tourniquet
3. Introduce self
4. Explain procedure
5. Obtain consent
6. Apply tourniquet
   1. 10cm above the desired cannulation site
   2. Find the target vein
      1. Back of the hand is a common site
      2. Standard practice is to work distal to proximal to avoid affecting the flow if an attempt fails
      3. Look for veins that are visible and straight if possible
7. Remove tourniquet
   1. Reduce patient discomfort as much as possible
8. Unpack dressing pack
9. Open saline bottle
10. Clean patient’s skin with chlorhexidine and alcohol swab
    1. This lets the disinfectant dry while you reapply the tourniquet and put on gloves
11. Reapply tourniquet
12. Put on sterile gloves
13. Combine syringe and needle
    1. Like when the Power Rangers combine to form their giant Transformer at the end of every episode — seriously, every episode
    2. Use this to draw the saline from the bottle without touching the bottle
    3. Although not a strictly sterile procedure like scrubbing before surgery, this no-touch technique preserves what is available of the aseptic field
14. Remove the needle
    1. Dispose of it in the sharps bin
    2. If no sharps bin is nearby, dispose of the needle in your kidney dish
    3. Keep paper rubbish in a separate location so that you can simply tip the kidney dish contents into a sharps bin later on
    4. This prevents you from digging around in the kidney dish for needles afterwards, which helps to avoid needlestick injuries
15. Put bung on syringe
16. Place gauze distal to cannulation site
17. Unpack cannula
18. Cannulate
    1. Pierce the cannula needle into the patient’s skin
       1. There is a degree of preference here, but a 15°-45° angle is standard enough
       2. People will tell you to have the “bevel down”
          1. That’s very confusing
          2. No one even knows what a bevel is
       3. The pointy end of the needle is shaped like a triangle
       4. It just means to have the pointiest, longest part of the triangle at the bottom, closest to the patient’s skin
    2. Once it’s in, advance the cannula part, not the needle
    3. Retract the needle
    4. Put the not-attached-to-the-syringe side of the bung on the not-in-the-patient’s-skin side of the cannula
    5. Note that there are multiple techniques to choose from
       1. Another school of thought is an angle in the 15°-30° range
       2. Much closer to the 15° side is advised
       3. After you see flashback, ensure the needle is as close to parallel to the vein as possible
       4. Advance the needle a small way to ensure you are in the vein and not merely subcutaneous
       5. Then advance the cannula part
    6. Tip
       1. What hurts the patient the most is the needle being moved through the skin, which produces an unpleasant sting
       2. Although hesitation is natural at this point, piercing the skin incompletely or slowly only complicates the process
       3. It is better to do the procedure confidently to avoid having to retry or prolonging the sting
       4. Although you might wish to avoid inflicting pain on the patient, some pain is inevitable for this procedure and it is better to work through it quickly than to futilely try to avoid it
19. Remove tourniquet
20. Flush with saline
    1. This checks that the connection is patent
    2. A test of any abnormalities if you are in the wrong site, such as swelling
21. Put stickers on
    1. Secure the cannula
    2. Place the appropriate identification stickers on
    3. Document in the patient notes

Item 2.1: Venepuncture Indications

• Draw blood for analysis, such as coagulation studies, full blood count, EUC or other tests

Item 2.2: Venepuncture Contraindications

• As with cannulation
• See Item 1.2

Item 2.3: Venepuncture Risks

• Primarily bruising or pain from failed attempts

Item 2.4: Venepuncture Procedure

1. Gather equipment
   1. Alcohol swab
   2. Butterfly needle
   3. Cotton ball
   4. Gloves
      1. Cannulation and collection of blood for culture are considered sterile techniques
      2. However, standard venepuncture does not require sterile gloves
         1. As in gloves from a sterile pack
         2. Not unclean gloves you picked up from the street
         3. Don’t pick up gloves from the street
   5. Tourniquet
   6. Tube for blood collection
   7. Vacutainer
2. Introduce
3. Consent
4. Apply tourniquet
   1. Find vein of choice
5. Remove tourniquet
6. Unpack equipment
   1. Merge butterfly needle and vacutainer
7. Alcohol swab
   1. Wipe area clean
8. Reapply tourniquet
9. Put on gloves
10. Venepuncture
    1. Pierce butterfly needle into vein until there is flashback
       1. Like bevel, another fancy word that means nothing
       2. It refers to blood visibly coming back through the tube
    2. Hold butterfly needle still
       1. Stop moving the butterfly needle if you see blood coming back, because that means you’re where you want to be
       2. Advancing further could puncture through the other side of the vein
       3. Despite the name, entirely puncturing a vein is not the aim of the procedure
    3. Collect blood
       1. Attach blood tubes to the other side of the vacutainer
       2. Watch the blood pour in
11. Remove tourniquet
12. Remove butterfly needle
    1. But remove the tourniquet first to avoid blood gushing in your face
    2. Apply a cotton ball to the area
       1. The patient can be asked to hold this
13. Sheath needle
14. Dispose of equipment appropriately

References

1. Australian National University. Intravenous cannulation. Medical Student Journal of Australia. Retrieved from http://msja.anu.edu.au/
2. Louisiana State University Health Sciences Center. (2001). Venipuncture. Retrieved from https://www.medschool.lsuhsc.edu/