Hyperventilation in Craniotomy for Brain Tumor

Abstract

The effect of the method of pulmonary ventilation on cerebrospinal fluid pressure (CSF), brain tension, and blood gas changes was investigated in 20 patients undergoing craniotomy for brain tumor. Five different methods of ventilation were successively employed in the same patient during halothane/oxygen anesthesia. Assisted ventilation gave the highest values for CSF pressure (average =238 mm. of water). Intermittent positive pressure breathing caused a moderate fall in CSF pressure (mean =212 mm. of water). Positive-negative pressure breathing at minute volumes equal to or less than 15 liters per minute resulted in the lowest values for CSF pressure (mean =115 mm. of water), and clinically was associated with a slack brain. When a minute ventilation volume greater than 15 liters per minute was employed, CSF pressure tended to rise (mean =179 mm. of water), while the brain became tight and congested. This occurred in spite of respiratory alkalosls and a negative phase during expiration. Large ventilatory volumes were also associated with a progressive increase in cerebral arterial-venous oxygen difference and fall in oxygen saturation of blood sampled from the sagittal sinus. The data indicate that brain tension and CSF pressure can be modified by varying the method of ventilation under halothane/oxygen anesthesia.