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Subcutaneous Injections: A PLAB 2 Revision Blog

Preparing to demonstrate safe and effective subcutaneous (SC) injections in your PLAB 2 exam? Here’s a concise, high-yield guide tailored for UK-style clinical stations.


1. Indications & Rationale

  • Common Uses: Insulin, low‐molecular‐weight heparin (e.g., enoxaparin), vaccines (e.g., MMR), hormones, palliative medications and biologics (e.g., adalimumab).

  • Why SC? Slower, more predictable absorption than intramuscular routes; ideal for drugs requiring steady plasma levels.


2. Relevant Anatomy

  • Skin Layers:

    • Epidermis → Dermis → Subcutaneous fat (target layer) → Muscle

  • Landmarks & Sites:

    • Abdomen: 2 inches around the umbilicus avoided

    • Anterior Thigh: Mid–lateral aspect

    • Upper Arm: Posterolateral area of the deltoid region

    • Buttocks: Upper outer quadrant

Tip: In an exam you may be asked to verbalize your landmarks (“I’ll inject into the anterolateral thigh, halfway between the hip and knee.”).

3. Preparation & Asepsis

  1. Hand Hygiene: 20-second scrub or alcohol rub.

  2. Equipment Check:

    • Correct drug, dose, and concentration

    • Appropriate needle (usually 25–30 gauge, 4–8 mm length)

    • Syringe size matching volume (1 mL for <1 mL doses; 2–5 mL otherwise)

  3. Clean Site: Wipe skin in concentric circles from centre outward; allow to dry.


4. Injection Technique

  1. Pinch and Stabilize: Gently lift a skin‐and‐fat fold.

  2. Needle Insertion:

    • 45–90° angle depending on needle length and patient’s adipose layer.

  3. Aspirate? Generally not required in SC injections for insulin or heparin.

  4. Inject: Steady, slow push (5–10 seconds).

  5. Withdraw & Apply Pressure: Remove needle; press gently with sterile gauze.

  6. Dispose: Immediate sharps bin discard.


5. Site Rotation & Documentation

  • Rotation Pattern:

    • Abdomen: clockwise circle

    • Thigh/Arm/Buttock: divide into quadrants

  • Why Rotate? Prevent lipohypertrophy or lipoatrophy, ensure consistent drug absorption.

    • Lipodystrophy is when the fat under your skin changes shape—either building up into hard lumps (lipohypertrophy) or disappearing into little dents (lipoatrophy)—usually from repeatedly injecting in the same spot; these bumps or hollows can make injections more painful and affect how well your medicine is absorbed.

  • Record: Site, date/time, dose, batch number (for vaccines), and patient’s response.


6. Precautions & Contraindications

Precautions

Contraindications

• Clean, lesion-free skin

• Infection or inflammation at proposed site

• Correct needle size & angle

• Known allergy to medication or excipient

• Gentle technique; monitor for bleeding/bruising

• Bleeding disorders or anticoagulation without specialist advice

• Observe patient for local reactions (e.g., rash)

• Presence of significant lipodystrophy at the site

7. PLAB 2 Station Tips

  • Communication: Explain each step aloud: “I’m cleaning your skin… pinching the fold… inserting at a 45° angle…”

  • Consent & Comfort: Obtain verbal consent and ensure patient is relaxed and informed.

  • Safety First: Never recap needles; always use sharps bin.

  • Time Management: Practice the sequence until you can perform it smoothly within 5 minutes.


Reference

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