Cerebral Apoplexy (Stroke) Treated With or Without Prolonged Artificial Hyperventilation: 2. Cerebrospinal Fluid Acid-Base Balance and Intracranial Pressure

Abstract

CSF acid-base changes and intracranial pressure (ICP) were studied in 50 patients with cerebral apoplexy (stroke) in the acute phase. Thirty-three of the patients were treated afterward with artificial hyperventilation for 72 hours (15 hypocapnic [Pa CO_CO2 25 mm Hg] and 18 normocapnic). The remaining 17 patients were breathing spontaneously throughout. Arterial P CO_CO2, CSF lactate, pyruvate and bicarbonate and ICP were followed during the course. Compared to a control group initial mean values showed significant increases of CSF lactate (2.36 mmol per liter) and pyruvate (0.183 mmol per liter) but with a normal lactate/pyruvate ratio (13.3), a reduced bicarbonate (22.0 mmol per liter), and reduced Pa CO_CO2 (34 mm Hg), indicating spontaneous hyperventilation. No correlation between the degree of initial hyperventilation or CSF lactate and the mortality rate was found. ICP averaged initially 15 mm Hg. The untreated patients had almost unchanged CSF values and Pa CO_CO2 during the following six days. During induced and sustained hypocapnia and normocapnia, CSF bicarbonate slowly followed changes in Pa CO_CO2 with CSF pH tending to return toward normal. The time course of this CSF pH adaptation had an estimated half-time of about six hours, and was complete within 30 hours. A similar time course of changes induced in ICP by ventilation was observed.