Fcps part 1 anesthesiology mcq solve with reason
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The question is asking what pathological finding is seen in a patient with Polyarteritis Nodosa (PAN) presenting with BP 220/120 mmHg (hypertensive crisis/malignant hypertension). This is a two-part pathology question combining PAN + severe hypertension.
✅ Answer: A — Fibrinoid necrosis of arterioles
Reasoning
Understanding the question
The stem gives you two important clues:
- Polyarteritis nodosa (PAN) — a necrotizing vasculitis
- BP 220/120 mmHg — this is malignant/accelerated hypertension (BP >180/120 with end-organ damage)
The question asks what vascular change would be seen. Both conditions converge on the same pathological lesion.
Pathology of PAN
PAN is a necrotizing vasculitis of small- and medium-sized muscular arteries. Its hallmark lesion is segmental fibrinoid necrosis of vessel walls, involving the arteries and arterioles.
"The vascular lesion in polyarteritis nodosa is a necrotizing inflammation of small- and medium-sized muscular arteries... fibrinoid necrosis of the vessel wall." — Harrison's Principles of Internal Medicine 22E
"Polyarteritis nodosa demonstrating the typical lesion, consisting of segmental fibrinoid necrosis of the vessel wall." — Quick Compendium of Clinical Pathology, 5th Edition
Pathology of Malignant Hypertension (BP 220/120)
Malignant hypertension independently produces fibrinoid necrosis of arterioles, along with hyperplastic arteriolosclerosis ("onion-skin" appearance).
"In patients with severe 'malignant' hypertension... vascular injury may be sufficient to produce fibrinoid necrosis of arterioles and small arteries associated with intravascular thrombosis." — Robbins & Kumar Basic Pathology
"Fibrinoid necrosis may involve arterioles and glomeruli, sometimes with microthrombi within the glomeruli." — Robbins, Cotran & Kumar Pathologic Basis of Disease
Why not the other options?
| Option | Why Wrong |
|---|---|
| B — Fibrinoid necrosis of venules | Neither PAN nor hypertension targets venules. PAN affects arteries/arterioles; hypertension affects arterioles. Venule involvement is seen in hypersensitivity vasculitis (e.g., leukocytoclastic vasculitis). |
| C — Fibrous change | Fibrous/fibrotic changes are a late/healed stage (chronic hypertension produces hyaline arteriolosclerosis → fibrosis). This is an acute hypertensive crisis. |
| D — None of above | Incorrect, as fibrinoid necrosis of arterioles is well-documented. |
Summary
Both PAN and malignant hypertension independently cause fibrinoid necrosis of arterioles. In this clinical scenario, the combination makes Option A the unambiguous correct answer.
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I have enough from the library results and pharmacology knowledge. Here's the full answer:
✅ Answer: C — Benzathine Penicillin G
The app confirms this is correct (highlighted in green at 39%).
Reasoning
The question
"Single dose drug of choice for streptococcal community-acquired pneumonia is?"
The key phrase is "single dose" — this dramatically narrows the answer.
Why Benzathine Penicillin G?
Benzathine penicillin G is a long-acting depot formulation of penicillin G that is given as a single intramuscular injection. It produces prolonged, low-level serum concentrations, making it the ideal single-dose penicillin.
- Streptococcus pneumoniae (pneumococcus) remains highly susceptible to penicillin G
- Historically, parenteral penicillin G was the drug of choice for pneumococcal infections including community-acquired pneumonia
- Benzathine penicillin G is specifically used when single-dose, long-acting coverage is required
"Historically, the activity of penicillin against pneumococci made parenteral penicillin G the drug of choice for disease caused by susceptible organisms, including community-acquired pneumonia." — Harrison's Principles of Internal Medicine, 22E
The app also notes it on the explanation card: "Benzathine penicillin G → important antibiotic for group A streptococcal infections."
Why not the others?
| Option | Why Wrong |
|---|---|
| A — Ampicillin | Broad-spectrum aminopenicillin; used for CAP but requires multiple doses (every 6–8 hours), not single dose |
| B — Benzyl Penicillin | Short-acting penicillin G (IV/IM); requires frequent dosing (every 4–6 hours) — not a single-dose drug |
| D — Amoxicillin | Oral aminopenicillin; also multi-dose (1g every 8 hours for CAP); not a single-dose option |
Key Concept to Remember
| Drug | Route | Dosing |
|---|---|---|
| Benzyl penicillin G | IV/IM | Every 4–6 hours |
| Procaine penicillin | IM | Once or twice daily |
| Benzathine penicillin G | IM | Single dose (lasts 2–4 weeks) |
| Amoxicillin | Oral | Every 8 hours |
The "single dose" qualifier = Benzathine Penicillin G every time you see it in an MCQ.
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The library results are sufficient. Here's the complete answer:
✅ Answer: B — SIADH (Syndrome of Inappropriate ADH Secretion)
Clinical Data Analysis
| Parameter | Patient's Value | Interpretation |
|---|---|---|
| Serum Na⁺ | 112 mEq/L | Severe hyponatremia (normal 135–145) |
| Serum K⁺ | 3.9 mEq/L | Normal |
| Serum Osmolality | 175 mOsm/L | Low (normal 285–295) |
| Urine Osmolality | 1200 mOsm/L | Very HIGH (concentrated urine) |
| Context | Head injury (65F) | CNS lesion → inappropriate ADH |
Why SIADH?
The diagnostic hallmark of SIADH is the paradox:
- Low serum osmolality (dilute blood)
- High urine osmolality (concentrated urine)
Despite the serum being dilute (175 mOsm/L), the kidney is still producing maximally concentrated urine (1200 mOsm/L). This means ADH is being secreted inappropriately — the kidney refuses to dilute the urine even though the body is already water-overloaded.
"In SIADH, despite serum hypo-osmolality, urine osmolality is typically 250–1400 mOsm/kg. The diagnosis of SIADH should be suspected in any patient with hyponatremia who excretes urine that is inappropriately concentrated relative to serum osmolality." — Miller's Anesthesia, 10E & Tietz Textbook of Laboratory Medicine, 7th Edition
"SIADH is associated with hyponatremia, low serum osmolality, and high urine osmolality." — Kaplan & Sadock's Comprehensive Textbook of Psychiatry
Head injury is a classic cause — CNS lesions (trauma, tumors, meningitis) are well-recognized triggers of inappropriate ADH secretion.
Why NOT the Others?
| Option | Serum Osm | Urine Osm | Why Wrong Here |
|---|---|---|---|
| A — Diabetes Insipidus | ↑ High | ↓ Low (<300) | DI = dilute urine + high serum osm. The opposite of this case |
| C — Pure water deprivation | ↑ High | ↑ High | Serum osm would be HIGH (dehydration), not low |
| D — Nephrogenic DI | ↑ High | ↓ Low | Same as central DI — dilute urine + hypernatremia. Opposite of this case |
Key Rule for MCQs
| Condition | Serum Na | Serum Osm | Urine Osm |
|---|---|---|---|
| SIADH | ↓ Low | ↓ Low | ↑ High |
| Central DI | ↑ High | ↑ High | ↓ Low |
| Nephrogenic DI | ↑ High | ↑ High | ↓ Low |
| Water deprivation | ↑ High | ↑ High | ↑ High |
Low serum Na + Low serum Osm + High urine Osm after head injury = SIADH always.
Thank you so much
You're welcome! Good luck with your FCPS Part 1 Anesthesiology exam! 🎯
Feel free to share more MCQs anytime — I'll break down the reasoning from authoritative textbooks (Harrison's, Robbins, Miller's Anesthesia, etc.) each time. You're doing great!
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