Severe hypercapnia can be predicted by a decrease in cerebral electrical activity. The authors describe a sudden decrease in spectral entropy due to severe hypercapnia-induced respiratory acidosis in a patient with chronic pulmonary obstructive disease during lung resection. After two and a half hours of low tidal volume ventilation in the lateral position, the state entropy suddenly dropped from 45 to 7, without any changes in the effect-site concentration of propofol, end-tidal carbon dioxide (CO₂) tension, oxygen saturation, or arterial pressure. However, arterial blood gas analysis showed severe respiratory acidosis (pH 7.01, PaCO₂ 115 mmHg and PaO₂ 246 mmHg with FIO₂ of 0.5). Immediate hyperventilation improved the state entropy and acid-base balance. Electroencephalography-based spectral entropy can detect severe hypercapnia in chronic pulmonary obstructive disease patients with a large arterial to end-tidal CO2 difference due to prolonged hypoventilation during thoracic surgery.
Acid-Base Equilibrium ; Acidosis, Respiratory ; Arterial Pressure ; Blood Gas Analysis ; Carbon Dioxide ; Electroencephalography ; Entropy* ; Humans ; Hypercapnia* ; Hyperventilation ; Hypoventilation ; Lung ; Oxygen ; Propofol ; Thoracic Surgery ; Tidal Volume* ; Ventilation

Severe hypercapnia can be predicted by a decrease in cerebral electrical activity. The authors describe a sudden decrease in spectral entropy due to severe hypercapnia-induced respiratory acidosis in a patient with chronic pulmonary obstructive disease during lung resection. After two and a half hours of low tidal volume ventilation in the lateral position, the state entropy suddenly dropped from 45 to 7, without any changes in the effect-site concentration of propofol, end-tidal carbon dioxide (CO₂) tension, oxygen saturation, or arterial pressure. However, arterial blood gas analysis showed severe respiratory acidosis (pH 7.01, PaCO₂ 115 mmHg and PaO₂ 246 mmHg with FIO₂ of 0.5). Immediate hyperventilation improved the state entropy and acid-base balance. Electroencephalography-based spectral entropy can detect severe hypercapnia in chronic pulmonary obstructive disease patients with a large arterial to end-tidal CO2 difference due to prolonged hypoventilation during thoracic surgery.
Acid-Base Equilibrium ; Acidosis, Respiratory ; Arterial Pressure ; Blood Gas Analysis ; Carbon Dioxide ; Electroencephalography ; Entropy* ; Humans ; Hypercapnia* ; Hyperventilation ; Hypoventilation ; Lung ; Oxygen ; Propofol ; Thoracic Surgery ; Tidal Volume* ; Ventilation