[Brain temperature in patients with central nervous system lesions]. / Temperatura mózgu u chorych operowanych z powodu uszkodzen osrodkowego ukladu nerwowego.

The knowledge of human brain temperature is still very limited. In this report we investigated the relationship between brain and trunk temperature in neurosurgical patients during normothermia and fever. Another problem addressed was that of possible gradients of temperature within the brain. We carried out direct recordings of temperature in 63 operated, neurosurgical patients with a variety of intracranial pathologies. Flexible, teflon-coated thermocouples were placed intracranially during neurosurgical procedures. Oesophageal, rectal and tympanic temperatures were also monitored. An error of up to 1.3 degrees C is to be expected in single cases if brain temperature is deduced from the rectal or oesophageal temperature. Mean differences between brain temperature and core body temperature measured in the rectum or in the oesophagus, were between 0 to 0.3 degree C. Tympanic temperature (Tty) improved the approximation of brain temperature (Tbr) to within the mean difference between Tbr-Tty close to 0 degree C. Nevertheless Tty also differed from Tbr by as much as 1 degree C in single cases. Brain temperature was the highest body temperature measured, either in normothermia or in fever. Temperature gradients were proved to exist between the warmer brain interior and cooler surface, with maximal differences in temperature reaching 0.6 degree C. This temperature gradient tended to increase along with the rise in intracranial pressure and deterioration of the level of consciousness. Our results suggest that conclusions regarding brain temperature drawn on the basis of other core temperatures, may lead to significant errors, and intracranial temperature measurement is desirable in neurosurgical intensive care. Temperature gradients within the brain may exacerbate its biochemical injury during ischaemia and fever--a combination seen frequently in neurosurgical patients. This may be particularly so, since brain temperature in fever is the highest body temperature in a high proportion of these patients.

[Transcranial color Doppler estimation of blood flow parameters in respective basal cerebral arteries in healthy subjects]. / Ocena parametrów hemodynamicznych w poszczególnych tetnicach podstawy mózgu u ludzi zdrowych, za pomoca przezczaszkowej ultrasonografii dopplerowskiej z obrazowaniem w kolorze.

Transcranial colour-coded Doppler sonography enables estimation of blood flow parameters in the basal cerebral arteries. Reference values as well as age and gender dependence of these parameters are not sufficiently established in transcranial Doppler studies. There are no reports regarding blood flow in the respective arteries of the circle of Willis. Therefore we examined 185 healthy volunteers--82 men (mean age 47, range 20-78 years old) and 103 women (mean age 47, range 22-86 years old). The subjects were divided into three age groups: 20-40 years old (group I), 41-60 years old (group II) and more than 60 years old (group III). The examinations were performed via the temporal acoustic window with a 2.5 MHz probe. Angle-corrected peak systolic, mean and end-diastolic velocities as well as impedance indices were determined in the anterior, middle and posterior cerebral arteries. In the group I mean velocity values (mean +/- SD) for the anterior, middle and posterior arteries amounted to 56 +/- 14 cm/s, 81 +/- 20 cm/s and 52 +/- 12 cm/s, respectively. In group II the values were 53 +/- 16 cm/s, 73 +/- 19 cm/s and 51 +/- 12 cm/s, and in group III the values were 44 +/- 11 cm/s, 59 +/- 11 cm/s and 40 +/- 9 cm/s. Decline in the blood flow velocities and increase in the impedance indices were found in all vessels with advancing age. This was most pronounced in subjects who were more than 40 years old. The decrease with age in blood flow velocities was more substantial in the middle cerebral arteries than in the anterior and posterior cerebral arteries. In contrast, the impedance indices increased more distinctly in the anterior cerebral arteries than in the middle and posterior cerebral arteries. We have demonstrated that the blood flow Doppler parameters are age and, in the group I (20-40 years old), also gender dependent. The range of the normal reference values of these parameters has proved to be wide. Decrease with age in blood flow velocities was found to be varied in the major cerebral arteries.

Intracranial pressure processing with artificial neural networks: prediction of ICP trends.

It is well known that intracranial pressure (ICP) is influenced by an array of predictable and unpredictable factors, which gives rise to a signal heavily loaded with stochastic, i.e. random components. Hence, statistical modelling of this signal has proved to be of limited utility, in spite of the very sophisticated mathematical methods applied. In recent years, neural network algorithms (ANN), which are an alternative to statistical methods, have proved their effectiveness in the prediction of trends, as applied in a variety of medical and non-medical tasks. We therefore attempted to test the efficiency of neural models in the on-line prediction of ICP values, compare their effectiveness to statistically oriented algorithms and combine ANN methods with some newer signal processing algorithms, like wavelet decomposition. Prediction horizons of up to 5 minutes have been tested with various architectures of the neural predictor. For a 3 minute prediction horizon, a satisfactory accuracy of forecasting has been achieved with "plain" ANN, as expressed by the "average relative variance coefficient". This was measured by the ratio of the prediction error obtained, in relation to the error which would occur if a current value were taken as the forecasted one. The prediction quality with statistical autoregressive models has proved unsatisfactory, whilst the result obtained using the ANN model with the wavelet transform incorporated, performed significantly better than the ANN models alone. The prediction quality obtained with the ANN methodology seems to be satisfactory over a short time horizon, though no conclusion can be derived at this stage of the study, as to the clinical utility of this method. In particular, even with this methodology, it is not possible to forecast any sudden dehiscencies of the ICP signal with any practical reliability. From the point of view of modelling theory, such sharp deviations of the signal may be regarded as a "catastrophe". This implies the necessity for a different approach to the ICP signal analysis with the artificial intelligence methodology; one, that is more oriented towards the global properties of the signal.

Transcranial color Doppler sonography of basal cerebral arteries in 182 healthy subjects: age and sex variability and normal reference values for blood flow parameters.

OBJECTIVE: Only a limited number of transcranial color-coded Doppler studies have provided ranges for the normal reference values of cerebral hemodynamic parameters. These reports are not fully convergent in relation to the range of values or to the age and sex dependence of blood flow parameters. The aim of the present study was to provide data regarding normal reference ranges. SUBJECTS AND METHODS: We examined 182 healthy volunteers (79 men and 103 women; age range, 20-86 years old) with color-coded Doppler sonography via a temporal acoustic window with a 2.5-MHz transcranial probe. The subjects were divided into three age groups: 20-40 years old (group 1), 41-60 years old (group 2), and more than 60 years old (group 3). Angle-corrected peak systolic, end-diastolic, and mean velocities as well as impedance indexes were determined in anterior, middle, and posterior cerebral arteries. RESULTS: Mean velocity values for middle, anterior, and posterior cerebral arteries in age group 1 were 81+/-20, 56+/-14, and 52+/-12 cm/sec (mean +/- SD), respectively. In group 2, the values were 73+/-19, 53+/-16, and 51+/-12 cm/sec (mean +/- SD), and in group 3, the values were 59+/-11, 44+/-11, and 40+/-9 cm/sec (mean +/- SD). Decrease in blood flow velocities and a concomitant increase in impedance indexes were found in all vessels with advancing age-findings that were most pronounced in subjects who were more than 40 years old. In the 20- to 40-year-old group, mean velocities for all vessels were higher in women than in men, whereas impedance indexes were not significantly different. CONCLUSION: Flow velocities in basal cerebral arteries range widely and are significantly age dependent. Age and sex matching of Doppler sonographic data is a prerequisite for clinically valuable conclusions.

Failure of free fatty acids to influence degree of myocardial injury following acute coronary artery occlusion in pigs.

Elevation of circulating free fatty acids (FFA) has been implicated as a deleterious influence during conditions of myocardial ischemia. To further explore this question, acute coronary artery occlusion was produced in closed-chest, anesthetized pigs. FFA levels were elevated by injecting heparin and then infusing a lipid emulsion at 1 or 2 h following occlusion. Precordial ECG mapping was used to assess the degree of myocardial injury. At both 1 and 2 h following occlusion the lipid infusion elevated the mean FFA level to over 2,500 muM. ST segment levels failed to indicate any concomitant increase in degree of myocardial injury. By contrast, an isoproterenol infusion (30 min, 4-8 mug/min) under similar conditions did result in ST segment changes suggestive of extended myocardial injury. Augmented arterial FFA levels do not influence the degree of myocardial injury following acute coronary artery occlusion.