What is the appropriate management for a young female with a 2-week history of cough and fever, presenting with hypokalemia and specific serologic test results?

Management of Severe Hypokalemia in a Young Female with Prolonged Respiratory Symptoms

This patient requires immediate aggressive potassium replacement for life-threatening hypokalemia (K+ 1.95 mEq/L), with concurrent evaluation for the underlying cause of both the hypokalemia and the 2-week respiratory illness.

Immediate Life-Threatening Priority: Severe Hypokalemia

Urgent Assessment and Stabilization

• Obtain an ECG immediately to assess for cardiac conduction abnormalities, as severe hypokalemia can cause life-threatening arrhythmias 1, 2.
• Assess for symptoms of severe hypokalemia including muscle weakness, paresis, hyperreflexia, cramps, dysesthesia, and cardiac dysrhythmias 3.
• Check serum magnesium levels, as hypomagnesemia frequently accompanies hypokalemia and must be corrected simultaneously 1.

Potassium Replacement Strategy

• Initiate intravenous potassium chloride replacement immediately for this critically low potassium level, as oral supplementation alone is insufficient for K+ <2.5 mEq/L 4, 2.
• Target serum potassium levels of 4.5-5.0 mEq/L to prevent ventricular arrhythmias 1.
• Administer potassium chloride 20-60 mEq/day in divided doses, with careful cardiac monitoring during IV administration 1, 4.
• Correct hypomagnesemia if present (serum magnesium <1.6 mEq/L), as this impairs potassium repletion 1.
• Monitor serum potassium levels closely during replacement therapy, checking levels every 2-4 hours initially 2.

Differential Diagnosis for Combined Presentation

Respiratory Illness Evaluation

The 2-week history of cough and fever requires systematic evaluation:

• Assess vital signs immediately for heart rate ≥100 bpm, respiratory rate ≥24 breaths/min, or temperature ≥38°C to rule out pneumonia 5.
• Perform focused lung examination listening for asymmetrical lung sounds, focal consolidation, rales, egophony, or fremitus 5.
• Obtain chest radiography if vital sign abnormalities are present or asymmetrical lung sounds are detected 5.
• Consider pertussis when cough lasts ≥2 weeks with paroxysms, post-tussive vomiting, or inspiratory whooping 5.
• Obtain nasopharyngeal culture and paired sera for pertussis if suspected, and initiate macrolide therapy 5.
• Screen for tuberculosis risk factors including travel history from high TB prevalence areas, and obtain chest X-ray and sputum cultures if indicated 5.

Serologic Interpretation

The negative NS1 antigen with negative IgM but positive IgG suggests:

• Past dengue infection rather than acute dengue, as IgG positivity without IgM indicates prior exposure 1.
• This serologic pattern does not explain the current acute illness and should not distract from evaluating other causes 1.

Investigating the Cause of Hypokalemia

Essential Diagnostic Workup

• Obtain 24-hour urine potassium, magnesium, and creatinine to calculate transtubular potassium gradient (TTKG) and determine if losses are renal or extrarenal 6.
• Check venous blood gas to assess for metabolic acidosis or alkalosis, which helps narrow the differential 7.
• Review all medications including over-the-counter cough preparations, as these may contain ammonium chloride, ephedrine, or pseudoephedrine causing hypokalemia 7.
• Assess for gastrointestinal losses including vomiting, diarrhea, or nasogastric suction 2.

Specific Considerations

• COVID-19 testing should be performed, as SARS-CoV-2 infection has been associated with persistent hypokalemia in over half of patients, potentially lasting months 6.
• Evaluate for renal potassium wasting if TTKG >4 with hypokalemia, suggesting renal losses rather than GI losses 6.
• Consider cough mixture abuse, particularly if the patient has been self-medicating for 2 weeks, as this can cause severe hypokalemia with metabolic acidosis 7.

Critical Monitoring During Treatment

• Avoid rapid correction that could cause rebound hyperkalemia, especially if transcellular shifts are involved 2.
• Monitor for respiratory muscle weakness from hypokalemia, which can cause hypoventilation and respiratory acidosis 7.
• Check renal function (BUN and creatinine) during aggressive potassium replacement 1.
• Reassess potassium levels daily even after initial correction, as some patients require ongoing supplementation for weeks to months 6.

Common Pitfalls to Avoid

• Do not delay potassium replacement while waiting for diagnostic workup results, as K+ 1.95 mEq/L is immediately life-threatening 2, 3.
• Do not use oral potassium alone for severe hypokalemia (K+ <2.5 mEq/L); IV replacement is mandatory 4, 2.
• Do not overlook magnesium deficiency, which prevents effective potassium repletion 1.
• Do not assume the respiratory illness and hypokalemia are unrelated; COVID-19, cough mixture abuse, and severe respiratory infections can all cause profound hypokalemia 6, 7.
• Do not discharge the patient until potassium is >3.0 mEq/L and stable, the underlying cause is identified, and cardiac rhythm is normal 2.