Monitoring of Intracranial Pressure in Patients with Brain Tumors

Abstract

Intracranial pressure (ICP) was continuously monitored in 70 patients with brain tumors. Simultaneous recording of respiration and systemic blood pressure was carried out in 20 and 13 cases, respectively. In 13 of the former 20 cases, blood gases were analyzed during typical A waves (Lundberg's A wave). In addition, in four cases cerebral blood flow (CBF) was measured during typical A waves. The A wave appeared when the baseline ICP exceeded 20 mmHg, and the higher the baseline pressure was, the more frequently the A wave was recorded. Three respiratory patterns occurred during typical A waves: hyperventilation, hypoventilation, and normal respiration. However, these respiratory patterns were not always clear-cut, and the three often were mixed. Systemic blood pressure during the typical A wave phase was either elevated (Cushing's response) or normal. All patients who showed Cushing's response had high baseline ICP and, with the frequently appearance of the A wave, had such symptoms of increased ICP as headache, nausea, and disturbance of consciousness. In all four cases studied, CBF decreased during typical A waves. These results, indicate that the A wave is associated with elevation of ICP and intracranial tightness. A particular region in the brainstem reportedly participates in the generation of the A wave. However, the mechanism of its development appears complex and involves such secondary factors as respiration and systemic blood pressure.