A physician is preparing to administer post-exposure prophylaxis for a patient who has been bitten by a potentially rabid animal. Which of the following statements about the administration of rabies immunoglobulin (RIG) is INCORRECT? It is exclusively given in the deltoid The dose is 20 IU/kg Not given after 7 days of the 1st dose of the vaccine If human RIG is unavailable, equine is preferred
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rabies immunoglobulin RIG administration site dose post-exposure prophylaxis guidelines
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Answer
The INCORRECT statement is: "It is exclusively given in the deltoid."
Here is a breakdown of each option:
Option A - "It is exclusively given in the deltoid" - INCORRECT ✓
RIG is NOT given exclusively in the deltoid. The correct administration is:
- As much of the dose as anatomically possible should be infiltrated directly into and around the wound site(s)
- Any remaining volume (if the wound site cannot accommodate the full dose) is then injected intramuscularly at a site distant from the vaccine injection site
The deltoid is where the rabies vaccine is given - not RIG. RIG goes into the wound, not into the deltoid. (Park's Textbook of Preventive and Social Medicine, p. 325; CDC guidelines)
Option B - "The dose is 20 IU/kg" - CORRECT
- Human RIG (HRIG): 20 IU/kg body weight
- Equine RIG (ERIG): 40 IU/kg body weight
(Park's Textbook, p. 325; WHO guidelines)
Option C - "Not given after 7 days of the 1st dose of the vaccine" - CORRECT
RIG is administered only once, preferably at or as soon as possible after initiating post-exposure vaccination. Beyond day 7 after the first vaccine dose, RIG is not indicated because an active antibody response to the vaccine is presumed to have already developed by that point.
(Park's Textbook, p. 325; WHO Guide for Rabies PEP)
Option D - "If human RIG is unavailable, equine is preferred" - CORRECT
When HRIG is unavailable, equine RIG (ERIG) is an acceptable alternative. Modern equine preparations are potent, highly purified, and considerably less expensive than HRIG. They carry a small risk of anaphylaxis (~1/45,000 cases), but no skin test is required beforehand as it does not reliably predict reactions.
(Park's Textbook, p. 325)
Summary: RIG must be infiltrated into and around the wound - the deltoid is strictly for vaccine administration. Saying RIG is "exclusively" given in the deltoid is completely wrong.
Supre consular fracture median or AIN which nerve is injured
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supracondylar fracture humerus nerve injury AIN median nerve which is most common
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Supracondylar Fracture - Nerve Injury
The answer is the Anterior Interosseous Nerve (AIN).
Why AIN and not the main median nerve trunk?
Both the median nerve and its branch AIN can be injured, but the AIN is the most commonly injured nerve in supracondylar fractures. Here is how to remember the distinction:
| Feature | AIN (most common) | Median nerve (trunk) |
|---|---|---|
| Type | Branch of median nerve | Main trunk |
| Injury mechanism | Traction / contusion | Direct injury in severe/posterolateral displacement |
| Sensory loss | None (pure motor branch) | Yes - palm, lateral 3½ fingers |
| Motor deficit | Flexor pollicis longus, lateral FDP, pronator quadratus | All median-innervated muscles |
| Classic sign | "Pointing/OK sign" - cannot pinch (thumb & index fail to flex) | Thenar wasting + sensory loss |
Key Points
- AIN = most commonly injured nerve in supracondylar fractures (Rosen's Emergency Medicine; Tintinalli's)
- The order of nerve injury frequency: AIN > radial > median (trunk) > ulnar
- AIN is a pure motor branch - so there is no sensory loss, which is a classic exam trap
- The hallmark test: ask the patient to make an "OK" sign - AIN palsy produces a "pinch deformity" (pointing finger sign) because FPL and FDP to index are paralyzed
- Most injuries are neuropraxias that resolve within 7-12 weeks with conservative management
Memory Aid
"AIN = A IN supracondylar" - AIN is the #1 nerve injured.
The reason the question contrasts "median vs AIN" is that while many students say "median nerve," the more precise answer is AIN - the specific branch of the median nerve that is injured, not the whole trunk. Both are technically correct in clinical discussions, but for exam purposes AIN is the preferred answer.
- Tintinalli's Emergency Medicine, p. (block 11)
- Rosen's Emergency Medicine (block 7, p. 631)
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