NBME-style questions › Fluid, Electrolyte, Acid-Base
Fluid, Electrolyte, Acid-Base · Multisystem Processes · NBME-Style

Fluid, Electrolyte, Acid-Base — NBME-style practice question

A physician-validated, board-style question from the Active Transport QBank. Try it, then check the reasoning for every option.

A 9-year-old girl is admitted to the hospital with a one-day history of acute abdominal pain and vomiting. She also has a two-day history of fever, headache, and neck pain. Her immunizations are up-to-date. She is confused and oriented only to place and person. Her temperature is 39.7°C (103.5°F), pulse is 148/min, blood pressure is 90/50 mm Hg, and respiratory rate is 28/min. Cervical range of motion is limited by pain. The remainder of the neurologic examination shows no abnormalities. Laboratory studies show: Hemoglobin 10.9 g/dL Leukocyte count 44,000/mm3 Serum pH 7.33 Na+ 130 mEq/L Cl- 108 mEq/L K+ 6.1 mEq/L HCO3- 20 mEq/L Urea nitrogen 34 mg/dL Glucose 180 mg/dL Creatinine 2.4 mg/dL Urine ketones negative A CT scan of the head shows enhancement of the arachnoid and pia mater. Cerebrospinal fluid analysis shows a leukocyte count of 3,400/μL (90% neutrophils), a glucose concentration of 50 mg/dL, protein concentration of 81 mg/dL, and no erythrocytes. Gram stain of the CSF shows gram-negative diplococci. This patient is at increased risk for which of the following complications?"

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Answer: B. A child with rapid-onset fever, headache, neck stiffness, altered mental status, hypotension, and CSF showing neutrophilic pleocytosis (3,400 WBC, 90% neutrophils), low glucose, high protein, and gram-negative diplococci has acute bacterial meningitis from Neisseria meningitidis (meningococcal meningitis). She also has signs of septic shock and probable adrenal involvement (hypotension out of proportion, hyperkalemia, hyponatremia). The feared complication of meningococcemia is Waterhouse-Friderichsen syndrome — bilateral adrenal hemorrhage with adrenocortical insufficiency, occurring in the setting of fulminant meningococcal sepsis with DIC. Hemorrhage into the adrenal glands leads to acute primary adrenal failure with refractory shock, hyponatremia, hyperkalemia, and hypoglycemia. This patient's electrolyte pattern (Na 130, K 6.1) plus hypotension already raises concern. Urgent treatment is IV antibiotics (ceftriaxone, vancomycin), aggressive fluid resuscitation, and stress-dose hydrocortisone if adrenal insufficiency is suspected. Close contacts need chemoprophylaxis (rifampin, ciprofloxacin, or ceftriaxone). **Why each option:** **A.** Pancreatitis is associated with mumps and other viral infections, not classically with meningococcal meningitis. **B.** Correct — meningococcemia can cause Waterhouse-Friderichsen syndrome, bilateral adrenal hemorrhage producing acute adrenal insufficiency with refractory shock and electrolyte abnormalities. **C.** Vesicular skin eruptions are typical of HSV/VZV CNS infection; meningococcemia classically causes petechiae and purpura, not vesicles. **D.** Temporal lobe inflammation (encephalitis) is characteristic of HSV-1 encephalitis, not meningococcal meningitis.

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