Slow and rhythmic oscillations in intracranial pressure (ICP), also known as B waves, have been claimed to be one of the best preoperative predictive factors in idiopathic adult hydrocephalus syndrome (IAHS). Definitions of B waves vary widely, and previously reported results must be treated with caution. The aims of the present study were to develop a definition of B waves, to develop a method to estimate the B-wave content in an ICP recording by using computer algorithms, and to validate these procedures by comparison with the traditional visual interpretation.
In eight patients with IAHS, ICP was continuously monitored for approximately 20 hours. The ICP B-wave activity as a percentage of total monitoring time (B%) was estimated by using visual estimation according to the definition given by Lundberg, and also by using two computer algorithms (Methods I and II). In Method I each individual wave was classified as a B wave or not, whereas Method II was used to estimate the B-wave content by evaluating the B-wave power in 10-minute blocks of ICP recordings.
The two computerized algorithms produced similar results. However, with the amplitude set to 1 mm Hg, Method I yielded the highest correlation with the visual analysis (r = 0.74). At least 5 hours of monitoring time was needed for an acceptable approximation of the B% in an overnight ICP recording. The advantages of using modern technology in the analysis of B-wave content of ICP are obvious and these methods should be used in future studies.
"This method is very inaccurate hence it might lead to contradictory conclusions of the predictive value of ICP slow waves. There have been a few studies of the methodologies of detecting ICP slow waves (Hara et al., 1990; Eklund et al., 2001; Walter et al., 2002). However, these methods neglected changes and characteristics of individual ICP pulses during ICP slow waves presence. "
[Show abstract][Hide abstract] ABSTRACT: This study aimed to develop a new approach to detect intracranial pressure (ICP) slow waves based on morphological changes of ICP pulse waveforms. A recently proposed Morphological Clustering and Analysis of ICP Pulse (MOCAIP) algorithm was utilized to calculate a set of metrics that characterize ICP pulse morphology. A regularized linear quadratic classifier was used to test the hypothesis that classification between ICP slow wave and flat ICP could be achieved using features composed of mean values and dispersion of 24 MOCAIP metrics. To optimize the classification performance, three feature selection techniques (differential evolution, discriminant analysis and analysis of variance) were applied to find an optimal set of MOCAIP metrics under different criteria. In addition, we selected three sets of metrics common to those found by combination of two selection methods, to be used as classification features (differential evolution and analysis of variance, discriminant analysis and analysis of variance, and combination of differential evolution and discriminant analysis). To test the approach, a total of 276 selections of ICP recordings corresponding to two patterns without waves and containing slow waves were obtained from overnight ICP studies of 44 hydrocephalus patients performed at the UCLA Adult Hydrocephalus Center. Our results showed that the best classification performance of differentiation of slow waves from the ICP recording without slow waves was obtained using the combination of metrics common to both differential evolution and analysis of variance methods; achieving an accuracy of 89%, specificity 96%, and sensitivity 83%.
[Show abstract][Hide abstract] ABSTRACT: In idiopathic adult hydrocephalus syndrome (IAHS), a pathophysiological model of "chronic ischaemia" caused by an arteriosclerotic process in association with a CSF hydrodynamic disturbance has been proposed.
To investigate whether CSF hydrodynamic manipulation has an impact on biochemical markers related to ischaemia, brain tissue oxygen tension (PtiO(2)), and intracranial pressure.
A microdialysis catheter, a PtiO(2) probe, and an intracerebral pressure catheter were inserted into the periventricular white matter 0-7 mm from the right frontal horn in 10 patients with IAHS. A subcutaneous microdialysis probe was used as reference. Intracranial pressure and intracerebral PtiO(2) were recorded continuously. Samples were collected for analysis between 2 and 4 pm on day 1 (baseline) and at the same time on day 2, two to four hours after a lumbar CSF hydrodynamic manipulation. The concentrations of glucose, lactate, pyruvate, and glutamate on day 1 and 2 were compared.
After CSF drainage, there was a significant rise in the intracerebral concentration of lactate and pyruvate. The lactate to pyruvate ratio was increased and remained unchanged after drainage. There was a trend towards a lowering of glucose and glutamate. Mean intracerebral PtiO(2) was higher on day 2 than on day 1 in six of eight patients.
There is increased glucose metabolism after CSF drainage, as expected in a situation of postischaemic recovery. These new invasive techniques are promising tools in the future study of the pathophysiological processes in IAHS.
[Show abstract][Hide abstract] ABSTRACT: Maintaining adequate cerebral perfusion is the primary goal of management of patients with traumatic brain injury and intracranial pressure is one of the major factors affecting cerebral blood flow. Intracranial pressure measurement is necessary to confirm or exclude intracranial hypertension and to determine cerebral perfusion pressure. It also helps guide therapy in head injury patients. There is a substantial body of evidence to support the use of intracranial pressure monitoring and it is now a central part of the critical care management of the severely brain injured patient. This is a review of intracranial pressure monitoring with specific reference to traumatic brain injury. A brief description of the physiology of cerebral blood flow and intracranial pressure is given followed by the principles of measurement, indications, techniques and problems associated with intracranial pressure monitoring.
Current Anaesthesia and Critical Care 10/2003; 14(5–6):229-235. DOI:10.1016/j.cacc.2003.09.003
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