A 37-year-old woman complained of dyspneic sensation, headache, easy fatigability, cold sensation at the extremities and palpitation for a year. Arterial blood gas analysis showed the chronic respiratory alkalosis was fully compensated by the kidneys. Slow recovery of the end tidal PCO2 (PETCO2) after 2min of hyperventilation provocation test (HVPT) was also observed. These symptoms and findings indicated that the patient showed chronic type hyperventilation. Treatment by metoprolol (80mg/kg) and diazepam (6mg/kg) alleviated symptoms and improved the values in arterial gases as well as the slow recovery of PETCO2 after HVPT. Diazepam was stopped and treatment was maintained with only metoprolol. There was no deterioration of symptoms after stopping diazepam, indicating that metoprolol was effective in this patient. The CO2-ventilatory responsiveness was increased by treatment of metoprolol and diazepam. The effect of metoprolol and diazepam on a HVPT and CO2-ventilatory response in hyperventilation syndrome was discussed.
