Which gauze cannula is commonly used for blood transfusion?

Appeared in: Combined AIIMS - 2020 (Jodhpur, Bhopal, Patna, Raipur)

Explanation

The 18 Gauge (Green) cannula is the standard choice for routine blood transfusions in adult patients.
Its large bore (90 mL/min flow rate) allows blood to flow easily, minimizing the risk of mechanical damage (hemolysis) to red blood cells.
This size provides a good balance between adequate flow for viscous blood products and patient comfort.

Option A: A 16G (Gray) cannula has a very high flow rate (180 mL/min) and is larger than typically needed for a routine transfusion. It can cause more discomfort and vessel trauma.
Option C: A 22G (Blue) cannula is generally considered too small for routine blood transfusions in adults. The smaller diameter increases the pressure and shear stress on red blood cells, which can lead to hemolysis.
Option D: A 23G cannula is too small for a blood transfusion, posing a significant risk of hemolysis. Additionally, the color coding is inconsistent; 23G is typically blue (for butterfly needles) and 25G is orange.

Clinical Relevance

Nursing practice connection: Knowing IV cannula gauge selection for blood transfusion helps nurses interpret findings accurately and avoid errors in routine assessment, medication administration, and patient teaching.
Selecting the correct cannula gauge is a critical nursing skill that directly impacts patient safety and treatment efficacy during blood transfusions.
Using a cannula that is too small can lead to hemolysis, where red blood cells are destroyed. This not only renders the transfusion ineffective but can also release potassium into the bloodstream (hyperkalemia) and cause kidney damage.
Using a cannula that is unnecessarily large can cause pain, and damage to the vein, and increase the risk of phlebitis and infiltration.

How to Approach the Question

First, identify the core of the question: it asks for the 'commonly used' cannula for 'blood transfusion'. This implies a standard, routine procedure, not an emergency.
Recall the relationship between IV cannula gauge numbers and their size: a smaller gauge number means a larger cannula diameter.
Consider the properties of blood: it is more viscous than IV fluids. A larger cannula is needed to allow it to flow without being damaged.
Evaluate the options based on this knowledge. Eliminate gauges that are too small (22G, 23G) due to the risk of hemolysis and slow flow. Eliminate gauges that are excessively large (16G) for a 'common' or 'routine' transfusion, as they are reserved for trauma/rapid infusion.
This process will lead you to the 18G cannula as the most appropriate choice for a standard adult blood transfusion.

Concept Tested & Keywords

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E6 Medicine Davidson Principles Practice 24e p. 806-808

Practise the full Combined AIIMS - 2020 (Jodhpur, Bhopal, Patna, Raipur)

Attempt every question from this paper in a timed mock, then review the full solution for each one.