Objective measurement of hepatic encephalopathy by means of automated EEG analysis

Automated analysis of the electroencephalogram as an objective measurement of hepatic encephalopathy for the individual patient was investigated. The mean dominant frequency of patients with grades 0 and 1 hepatic encephalopathy was in the normal range (greater than or equal to 6.4 Hz); grade 1 hepatic encephalopathy, however, was characterized by abnormal relative power of theta activity of more than 35%. Twelve out of 34 patients with clinical grade 0 hepatic encephalopathy also had an elevated power of theta activity and probably therefore latent hepatic encephalopathy. Patients with grades 2, 3 and 4 hepatic encephalopathy had a low mean dominant frequency (less than 6.4 Hz) and could be identified by a biphasic power spectrum (theta and delta peaks, grade 2) or by a high power of delta activity (greater than or equal to 70%, grade 3-4). We conclude that automated EEG analysis based on the parameters mean dominant frequency and the relative powers of the delta and theta band is very suitable for objective classification of hepatic encephalopathy in individual patients.     

Analysis of cerebral echo-pulsation curves and plethysmograms in cases of cardiac arrhythmia

Cerebral echo-pulsations in 18 patients with atrial fibrillation of the heart were compared with finger and toe plethysmograms. A normalization technique was used to equalize curves recorded with different kinds of measurements. The average linear correlation coefficient between echo-pulsation and plethysmographic curves was 0.72 and indicates that a relationship exists between the RR-interval of the E.C.G. and the amplitude of echo movements in range and plethysmographic excursions.     

Chimerism pattern following allogeneic bone marrow transplantation; a retrospective study of the connection with post-transplantation complications

Allogeneic bone marrow transplantation is generally followed by disappearance of all host haematopoietic cells and replacement by donor cells, resulting in complete chimerism. In some cases, however, residual host cells can be detected after transplantation; this is called partial chimerism. We have analysed the chimerism pattern in 106 patients, by erythrocyte antigen typing, erythrocyte and leucocyte isoenzymes, immunoglobulin allotyping and karyotyping of bone marrow and blood. Recipients of a T cell-depleted marrow transplant exhibited partial chimerism significantly more often. In most cases this involved T lymphocytes, sometimes in combination with other cell populations. Persisting B lymphocytes of host origin were detected only in recipients of a T cell-depleted marrow graft. No relationship was found between chimerism pattern and GVHD, interstitial pneumonitis, relapse of the underlying disease or disease free survival.     

Tolerance to Nitrous Oxide in Volunteers

Nociception and loss of awareness during exposure to anaesthetic concentration of nitrous oxide (N2O) were studied in eight male medical students. The cold water nociception test, where a hand is immersed in 0 degree C stirred water, was used for measurement of nociception. At irregular intervals an auditory command was given to oppose two fingers, and this served to monitor consciousness. The selected inspiratory concentration of N2O used per individual was sufficient to induce a loss of consciousness for more than 2.5 min, within 10 min of exposure to N2O. This concentration of N2O varied from 60% to 80%. The experimental exposure to N2O lasted 3 h. In all volunteers significant antinociception was observed within 2 min of exposure to N2O. The maximal analgesic effect was observed between 20 and 30 min of exposure to N2O. The analgesic effect of N2O gradually decreased and was absent in all eight volunteers within 150 min. Two volunteers regained consciousness at 77 and 91 min of exposure, whilst still breathing 60 and 80% N2O. These results show that tolerance to antinociceptive effects of N2O in man rapidly develops and that awareness may occur in some volunteers during prolonged exposure to N2O.     

Detection of galactomannan in bronchoalveolar lavage fluid samples of patients at risk for invasive pulmonary aspergillosis: analytical and clinical validity

Invasive pulmonary aspergillosis (IPA) is frequent and often fatal in immunosuppressed patients. Timely diagnosis of IPA improves survival but is difficult to make. We examined the analytical and clinical validity of galactomannan (GM) testing of bronchoalveolar lavage (BAL) fluid in diagnosing IPA in a mixed population by retrospectively reviewing records of 251 consecutive at-risk patients for whom BAL fluid GM testing was ordered. The performance of the enzyme immunoassay was evaluated by using a range of index cutoffs to define positivity. Three samples were associated with proven IPA, 56 were associated with probable IPA, 63 were associated with possible invasive fungal disease (IFD), and 129 were associated with no IFD. Using a BAL fluid GM index of ≥0.8 (optimal optical density [OD] index cutoff identified by a receiver operating characteristic curve), the sensitivity in diagnosing proven and probable IPA was 86.4%, and the specificity was 90.7%. At this cutoff, positive and negative predictive values were 81% and 93.6%, respectively. However, an OD index value of ≥3.0 corresponded to a 100% specificity, thus ruling the disease in, irrespective of the pretest probability. Conversely, an OD index cutoff of <0.5 corresponded to a high sensitivity, virtually always ruling the disease out. For all values in between, the posttest probability of IPA depends largely on the prevalence of disease in the at-risk population and the likelihood ratio of the OD index value. Detection of GM in BAL fluid samples of patients at risk of IPA has an excellent diagnostic accuracy provided results are interpreted in parallel with clinico-radiological findings and pretest probabilities.