MCQ NO 1: ECG Abnormality
A 10-year-old boy is admitted with diabetic ketoacidosis (DKA). Treatment is initiated with intravenous fluids and insulin. A few hours later, an ECG is performed and shows mild ST-segment depression, prominent U waves, and QT interval prolongation. Laboratory investigations reveal the following:
| Investigation | Result |
|---|---|
| Serum sodium | 137 mmol/L |
| Serum potassium | 3.8 mmol/L |
| Random blood glucose | 310 mg/dL |
What is the most likely cause of these ECG changes?
A. Hyponatremia
B. Hypernatremia
C. Hypokalemia
D. Hyperkalemia
E. Hypocalcemia
Answer: C. Hypokalemia
Explanation: ECG changes in hypokalemia
The ECG findings of ST-segment depression, prominent U waves, and QT prolongation are classic features of hypokalemia. In diabetic ketoacidosis, there is a significant total body potassium deficit due to osmotic diuresis and potassium loss in urine. Although the serum potassium level may initially be normal or even elevated, it does not accurately reflect total body potassium stores. Once insulin therapy is started, potassium shifts into the cells, making hypokalemia more apparent. ECG changes are often a more reliable indicator of clinically significant potassium depletion.
Why not the other options?
- A. Hyponatremia: Usually does not produce characteristic ECG changes. Severe hyponatremia may rarely cause conduction abnormalities but not the ECG pattern seen here.
- B. Hypernatremia: Typically does not cause specific ECG abnormalities, and the serum sodium level is normal in this patient.
- D. Hyperkalemia: Characteristically causes tall peaked T waves, shortened QT interval, widening of the QRS complex, and eventually sine-wave changes in severe cases.
- E. Hypocalcemia: Causes QT prolongation by prolonging the ST segment but does not produce prominent U waves or the typical ECG findings seen in hypokalemia.
MCQ NO 2: Febrile illness with Rash
A 12-year-old boy presents with high-grade fever, purpuric rash, seizures, and altered consciousness. Cerebrospinal fluid (CSF) examination confirms the diagnosis of meningitis. Forty-eight hours after admission, he develops severe shock. Despite aggressive intravenous fluid resuscitation and inotropic support, the shock remains refractory. Laboratory investigations show:
| Investigation | Result |
|---|---|
| Serum sodium | 128 mmol/L |
| Serum potassium | 6.5 mmol/L |
What is the most likely complication that has developed in this patient?
A. Septic shock
B. Neurogenic shock
C. Intracranial hemorrhage
D. Hyponatremic dehydration
E. Waterhouse–Friderichsen syndrome
Answer: E. Waterhouse–Friderichsen syndrome
Explanation: Waterhouse-Friderichsen syndrome
This child most likely has meningococcal meningitis with meningococcemia, complicated by Waterhouse–Friderichsen syndrome, which is characterized by massive bilateral adrenal hemorrhage leading to acute adrenal insufficiency. The presence of a purpuric rash, refractory shock, hyponatremia, and hyperkalemia strongly suggests adrenal failure. Patients may rapidly progress to circulatory collapse, disseminated intravascular coagulation (DIC), coma, and death if not promptly recognized and treated.
Why not the other options?
- A. Septic shock: Although septic shock can occur in severe meningococcal infection, the combination of refractory shock, hyponatremia, and hyperkalemia is more characteristic of acute adrenal insufficiency due to Waterhouse–Friderichsen syndrome.
- B. Neurogenic shock: Typically results from spinal cord injury causing loss of sympathetic tone and is not associated with hyperkalemia or adrenal failure.
- C. Intracranial hemorrhage: May cause neurological deterioration and hemodynamic instability, but it does not explain the electrolyte abnormalities suggestive of adrenal insufficiency.
- D. Hyponatremic dehydration: Can cause shock and low sodium levels, but it does not account for the marked hyperkalemia and persistent inotrope-resistant shock seen in this patient.
Clinical Pearl:
In a child with meningococcemia, purpuric rash, refractory shock, hyponatremia, and hyperkalemia, always suspect Waterhouse–Friderichsen syndrome (acute adrenal hemorrhage causing adrenal crisis).
MCQ NO 3: Seizures
A 10-year-old boy is admitted to the Pediatric Intensive Care Unit with meningitis. Over the last 24 hours, his condition has progressively deteriorated, and he has experienced two episodes of seizures. His laboratory investigations show:
| Investigation | Result |
|---|---|
| Serum sodium | 126 mmol/L |
| Serum potassium | 3.9 mmol/L |
| Serum creatinine | 0.6 mg/dL |
| Serum urea | 40 mg/dL |
| Plasma osmolality | 253 mOsm/kg |
| Venous blood gas pH | 7.39 |
A repeat CT scan of the brain is normal.
What complication has most likely developed in this patient?
A. Hyponatremic dehydration
B. Subdural empyema
C. Syndrome of inappropriate antidiuretic hormone secretion (SIADH)
D. Hydrocephalus
E. Subtherapeutic anticonvulsant levels
Answer: C. Syndrome of inappropriate antidiuretic hormone secretion (SIADH)
Explanation: Syndrome of inappropriate ADH secretion(SIADH)
SIADH is a well-recognized complication of meningitis and is an important cause of hyponatremia in these patients. Excess secretion of antidiuretic hormone leads to water retention, resulting in hyponatremia and low plasma osmolality. Neurological manifestations include confusion, lethargy, seizures, altered consciousness, and, in severe cases, coma.
In this patient, the combination of hyponatremia (126 mmol/L), low plasma osmolality (253 mOsm/kg), seizures, and a normal CT scan strongly supports the diagnosis of SIADH.
Why not the other options?
- A. Hyponatremic dehydration: Usually presents with volume depletion and is associated with increased ADH secretion secondary to dehydration. The laboratory pattern and low plasma osmolality in a patient with meningitis are more suggestive of SIADH.
- B. Subdural empyema: Can complicate meningitis and cause seizures, but it would typically be detected on neuroimaging. The repeat CT scan is normal.
- D. Hydrocephalus: A recognized complication of meningitis that may cause neurological deterioration, but it would be evident on CT imaging.
- E. Subtherapeutic anticonvulsant levels: May contribute to seizures but do not explain the significant hyponatremia and low plasma osmolality.
Clinical Pearl:
In a patient with meningitis who develops hyponatremia, low plasma osmolality, and seizures, always consider SIADH as a potential complication, particularly when neuroimaging is normal.
MCQ NO 4: Diarrhea & dehydration
A 10-month-old infant is brought to the emergency department with a 4-day history of profuse diarrhea and vomiting. The mother reports that she has been giving the child plain water after each loose stool instead of ORS. On examination, the infant is lethargic, has sunken eyes, delayed capillary refill, and cool extremities. He develops a generalized tonic-clonic seizure shortly after arrival.
Laboratory investigations show:
- Serum sodium: 118 mmol/L
- Serum potassium: 3.8 mmol/L
- Blood glucose: 92 mg/dL
What is the most appropriate initial treatment?
A. 0.9% normal saline
B. 3% hypertonic saline
C. 5% dextrose
D. Lactated Ringer’s solution
E. Oral rehydration solution