A patient is arriving in the emergency department after severe Haemorrhage. The sister in charge told the nursing sister to perform cannulation quickly. Which of the following cannulas provides the highest amount of fluid to prevent shock?

1. A

   22 G

2. B

   20 G

3. C

   18 G

4. D

   16 G

Appeared in: NIMHANS Nursing Officer - 2019

Explanation

• In medical emergencies like severe hemorrhage, rapid fluid replacement is critical to prevent hypovolemic shock.
• The flow rate of an IV cannula is inversely related to its gauge number; a smaller gauge number signifies a larger internal diameter.
• A larger diameter allows for a much higher volume of fluid to be infused per minute, which is essential for stabilizing the patient.
• Among the given options, the 16 G cannula has the smallest gauge number, meaning it has the largest bore and the highest flow rate (approximately 180 mL/min).
• The color-coding seen in the image (Grey for 16 G) allows for quick identification in emergency settings.

Why Other Options Were Wrong

• Option A: A 22 G (Blue) cannula has a very small diameter and a low flow rate (around 36 mL/min), making it completely inadequate for rapid fluid resuscitation in a patient with severe bleeding.
• Option B: A 20 G (Pink) cannula is a common size for general IV infusions but its flow rate (around 60 mL/min) is insufficient for the massive fluid volumes needed to counteract hemorrhagic shock.
• Option C: An 18 G (Green) cannula is a large-bore catheter and a good choice for many situations, but its flow rate (around 90 mL/min) is half that of a 16 G cannula. In a case of severe hemorrhage, the highest possible flow rate is prioritized.

Related Visual

Clinical Relevance

• Nursing practice connection: Prioritize focused assessment, early escalation, and real-time monitoring when managing IV Cannula Gauge and Flow Rates for Fluid Resuscitation in acute care settings.
• In any trauma or emergency setting, establishing large-bore IV access (ideally two lines, 14G or 16G) is a top priority for the nursing staff to facilitate rapid fluid and blood product administration.
• The principle behind the flow rate is described by Poiseuille's law, which states that flow is proportional to the radius to the fourth power. This means even a small increase in cannula diameter leads to a massive increase in flow rate.
• What if? If a 16 G cannula cannot be inserted due to difficult venous access, the next best step is to attempt an 18 G cannula. If peripheral access fails entirely, the team may proceed to central venous access or intraosseous (IO) infusion.

How to Approach the Question

• First, identify the core clinical problem in the question: the patient has 'severe Haemorrhage' and needs fluid 'quickly' to 'prevent shock'.
• Recognize that this requires the highest possible rate of fluid infusion.
• Recall the relationship between IV cannula gauge and flow rate: a smaller gauge number means a larger diameter and a higher flow rate.
• Evaluate the options provided (22 G, 20 G, 18 G, 16 G) based on this principle.
• Compare the gauge numbers and select the smallest number, as it represents the largest cannula and the highest flow rate.
• Therefore, the 16 G cannula is the correct choice for this emergency scenario.

Concept Tested & Keywords

• Concept Tested: IV Cannula Gauge and Flow Rates for Fluid Resuscitation
• Stem keywords: severe Haemorrhage, cannulation, highest amount of fluid, shock
• Lead-in keywords: Which
• Clinical cues: Patient with severe hemorrhage requiring rapid cannulation, indicating an emergency need for high-volume fluid resuscitation.

Question ID

QCu4psW2Fj1usqI2f8wA8V

Copy ID

Reference Book

E6 Nursing Fundamentals Taylor pp. 1092-1094, 798-800

E6 Medicine Davidson Principles Practice 24e p. 226-228