The relationship of intracranial pressure Lundberg waves to electroencephalograph fluctuations in patients with severe head trauma
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Lundberg (or B) waves, defined as repetitive changes in intracranial pressure (ICP) occurring at frequencies of 0.5 to 2 waves/min, have been attributed to cerebral blood flow fluctuations induced by central nervous system pace-makers or cerebral pressure autoregulation. We prospectively recorded and digitalized at a frequency rate of 10 Hz (AcqKnowledgeTM software) the following parameters in 6 brain injured patients: mean arterial pressure, heart rate, ICP, mean flow velocity of the middle cerebral artery (MFVMCA) (transcranial Doppler WAKITM) and left and right spectral edge frequency (SEFl, SEFr) of continuous electroencephalogram (EEG) recordings (PhilipsTM technologies). All patients were sedated using a combination of sufentanil and midazolam and mechanically ventilated. Cerebral electrical activity (oscillations of SEF at a mean frequency of 26±9 mHz) and MFVMCA fluctuations were found strongly correlated with the intracranial Lundberg B waves (mean frequency 23±7 mHz). These result support the existence of a neuropacemaker at the origin of the Lundberg B waves. The change in cerebral electrical activity, resulting from cerebral pacemakers, could increase cerebral metabolic rate of oxygen (CMRO2) and thus lead to an increase in cerebral blood flow and secondarily of ICP through a change in cerebral blood volume.
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