What is the angle between the needle and skin during an intramuscular injection on the vastus lateralis?

AIIMS Rishikesh NO - 2019

Fundamental of Nursing

Easy

Appeared in: AIIMS Rishikesh NO - 2019

Explanation

The standard angle for an intramuscular (IM) injection is 90 degrees.
This perpendicular angle ensures the needle passes through the subcutaneous layer and deposits medication deep into the muscle tissue.
Deep muscle delivery is crucial for rapid and effective absorption due to the muscle's rich blood supply.
The vastus lateralis is a common IM site, and a 90-degree angle is the correct technique for administration at this location.

Option A: A 45-degree angle is too shallow for an IM injection and would likely deposit the medication into the subcutaneous fat instead of the muscle.
Option C: A 25-degree angle is far too shallow for an IM injection and is not a standard angle for subcutaneous injections either.
Option D: A 60-degree angle is not a standard for any specific injection type. It creates uncertainty about whether the medication is delivered into the muscle or the subcutaneous tissue, leading to inconsistent absorption.

Clinical Relevance

Nursing practice connection: This is primarily an exam-oriented knowledge point with limited direct bedside application, so retain Intramuscular Injection Technique as background academic context rather than a clinical decision trigger.
Using the correct injection angle is a critical nursing skill for patient safety and medication efficacy. An incorrect angle can lead to complications such as sterile abscesses, nerve damage, or ineffective drug absorption.
The choice of needle length is as important as the angle. The needle must be long enough to reach the muscle. For an obese patient, a longer needle is required, while a very thin patient may need a shorter needle.
What if the patient is very thin or emaciated? While 90 degrees is the standard, the nurse must assess the muscle mass. In a cachectic patient, the nurse might need to bunch the muscle to ensure the needle reaches muscle tissue and does not hit the bone.

How to Approach the Question

First, identify the key terms in the question: 'intramuscular injection' and 'vastus lateralis'.
Recall the standard nursing procedures for different types of parenteral injections (Intradermal, Subcutaneous, Intramuscular).
Visualize the layers of tissue: skin, fat (subcutaneous), and muscle. An IM injection needs to reach the deepest layer, the muscle.
Consider the angle required to pass through the overlying layers and deposit medication directly into the muscle. A perpendicular (90-degree) angle is the most direct and effective route.
Evaluate the given options. 45 degrees is for subcutaneous, and 25 and 60 degrees are not standard for IM injections, making 90 degrees the only correct choice.
If an image is provided, use it to confirm your understanding. The image shows a 90-degree angle, reinforcing the correct answer.

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