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Effects of dietary protein content on weaning from the ventilator.
The effect of enteral nutrition with different protein contents on metabolic and ventilatory variables during weaning from the ventilator was studied in 10 mechanically ventilated patients as indication of the effect of protein on the ventilatory drive. Resting energy expenditure (R.E.E.) was assessed in the post-absorptive state and 2 enteral regimens both with a fat and carbohydrate content 1.25 times R.E.E. but with a moderate (190 mg N/kg/24 h) and high (260 mgN/kg/24 h) protein content were given to the patients in random order. Minute ventilation (V(E)), CO2-production (VCO2), O2-consumption (VO2) and arterial blood-gases were obtained during mechanical ventilation and weaning. Compared with post-absorptive state, both intakes gave significant increases in VCO2 during mechanical ventilation; the VCO2 values were equal for both regimens before the start of the weaning procedures. High protein intake was associated with significantly higher VCO2 during weaning and smaller increases in paCO2 from mechanical ventilation to the end of the weaning-period, compared with the moderate protein intake. This result is in agreement with studies in which an infusion of amino-acids in spontaneous breathing healthy volunteers increased ventilatory sensitivity to CO2. For mechanically ventilated patients high protein nutrition may be beneficial in enhancing weaning from the ventilator.
EEG synchronization likelihood in mild cognitive impairment and Alzheimer's disease during a working memory task.
OBJECTIVE: Synchronization likelihood analysis of resting state EEG has shown that cognitive dysfunction in Alzheimer's disease (AD) and its precursor mild cognitive impairment (MCI) are associated with a loss of functional connectivity in high (upper alpha and beta) frequency bands. Working memory tasks are known to change functional connectivity, but it is unknown whether this increases the differences between AD, MCI and healthy controls. Our objective was to investigate the behavior of synchronization likelihood of multichannel EEG in AD, MCI and cognitively healthy controls, both at rest and during a working memory task. METHODS: EEGs (200 Hz sample frequency, 21 channels, average reference) were recorded at rest as well as during a visual working memory task in 14 patients with AD according to the NINCDS-ADRDA criteria (mean age 76.4; SD 13.6), 11 patients with MCI according to the criteria of Petersen (mean age 78.4; SD 6.4) and 14 with subjective memory complaints but no demonstrable memory disturbance (mean age 61.6; SD 26.6). The synchronization likelihood was computed over 19 channels, comparing each channel with all the other channels for the 0.5-4, 4-8, 8-10, 10-12, 12-30, 30-50 Hz frequency bands. RESULTS: The synchronization likelihood was significantly decreased in the upper alpha (10-12) and beta (12-30) bands in AD compared to persons with subjective memory complaints. The working memory task scores strongly correlated with Mini-Mental State Examination scores. During the working memory task the synchronization likelihood was significantly higher in MCI compared to the control subjects in the lower alpha band (8-10 Hz). CONCLUSIONS: Decrease of beta band synchronization occurs in mild AD, both in a resting condition and during a working memory task. SIGNIFICANCE: Decrease of beta band synchronization in mild AD is a robust finding. The present study confirms our findings in a different cohort of patients, using alternative frequency bands. The diagnostic value of the synchronization likelihood in AD and MCI needs to be further established.
Thyroid diseases and cerebrovascular disease.
BACKGROUND AND PURPOSE: Acute cerebral ischemia has been described in different diseases of the thyroid gland, and not only as a result of thyrotoxic atrial fibrillation and cardioembolic stroke. The purpose of this review is to summarize the studies on the relationship between thyroid diseases and cerebrovascular diseases, discussing the main findings for overt hyperthyroidism and hypothyroidism, as well as for subclinical thyroid dysfunction. SUMMARY OF REVIEW: In overt hyperthyroidism, cardioembolic stroke is clearly associated to thyrotoxic atrial fibrillation, and in subclinical hyperthyroidism with serum thyroid-stimulating hormone levels <0.1 mU/L, the incidence of atrial fibrillation is increased. Although in vitro and in vivo studies indicate a hypercoagulability state in hyperthyroidism, there is insufficient evidence to prove that this state leads to an increased risk of cardiac emboli. However, the hypothesis that overt hyperthyroidism may cause acute cerebral venous thrombosis is intriguing. Possible associations between hyperthyroidism and Moyamoya or Giant cell arteritis have only been described in case reports. There is enough evidence that overt hypothyroidism is associated with several traditional and newer atherosclerotic risk factors, especially hypertension, hyperlipidemia, and hyperhomocysteinemia. For subclinical hypothyroidism, these associations are less certain. Hypothyroidism has been associated with signs of aortic or coronary atherosclerosis, but no case-control or cohort studies have ever investigated hypothyroidism as a possible risk factor for atherothrombotic stroke. CONCLUSIONS: Hyperthyroidism is associated with atrial fibrillation and cardioembolic stroke. Hypothyroidism is associated with a worse cardiovascular risk factor profile and leads to progression of atherosclerosis. Associations between hyperthyroidism and acute cerebral venous thrombosis, Moyamoya, and Giant cell arteritis have been suggested, but sound evidence is lacking. Additional studies are needed to clarify these issues.
Effects of novelty and conditioned fear on small intestinal and colonic motility and behaviour in the rat.
Novelty and conditioned fear were used to investigate the effects of psychological stress on fasting small intestinal and colonic myoelectric activity and their relation with behaviour in freely moving rats fitted with bipolar electrodes on proximal jejunum and colon. Rats in both novelty and conditioned fear groups spent a 15 min session in a novel box, where only rats in the fear group received unescapable, repeated foot shock (10 x 6 s, 0.5 mA). Behaviour in groups reexposed to the box on day 1 or day 7 indicated a profound difference in emotional state. Conditioned fear rats remained largely immobile, while novelty rats displayed active exploratory behaviour. Behaviour during conditioned fear did not differ significantly between rats reexposed to the box either 1 or 7 days after foot shock, while novelty animals appeared more aroused on day 7. Conditioned fear on day 1 caused a significant increase in colonic spike burst frequency compared to basal values in the home cage. A smaller but significant increase was found in novelty rats. In groups tested after 7 days, both novelty and conditioned fear resulted in small increases in colonic burst frequency that did not differ significantly from each other. No effects were found on the incidence of the fasting jejunal Migrating Motility Complex. Defecation was see only in conditioned fear rats, but did not differ quantitatively between day 1 and day 7. We conclude that, in the rat, colonic myoelectric spike burst activity is highly responsive to psychological stress, while the fasting pattern of small intestinal activity is more resistant.(ABSTRACT TRUNCATED AT 250 WORDS)
Abnormal fronto-parietal coupling of brain rhythms in mild Alzheimer's disease: a multicentric EEG study.
Cholinergic deafferentation/recovery in rats mainly impinges on the fronto-parietal coupling of brain rhythms [D. P. Holschneider et al. (1999) Exp. Brain Res., 126, 270-280]. Is this reflected by the functional coupling of fronto-parietal cortical rhythms at an early stage of Alzheimer's disease (mild AD)? Resting electroencephalographic (EEG) rhythms were studied in 82 patients with mild AD and in control subjects, such as 41 normal elderly (Nold) subjects and 25 patients with vascular dementia (VaD). Patients with AD and VaD had similar mini-mental state evaluation scores of 17-24. The functional coupling was estimated by means of the synchronization likelihood (SL) of the EEG data at electrode pairs, accounting for linear and non-linear components of that coupling. Cortical rhythms of interest were delta (2-4 Hz), theta (4-8 Hz), alpha (1 8-10.5 Hz), alpha 2 (10.5-13 Hz), beta 1 (13-20 Hz), beta 2 (20-30 Hz) and gamma (30-40 Hz). A preliminary data analysis (Nold) showed that surface Laplacian transformation of the EEG data reduced the values of SL, possibly because of the reduction of influences due to head volume conduction. Therefore, the final analysis was performed on Laplacian-transformed EEG data. The SL was dominant at alpha 1 band in all groups. Compared with the Nold subjects, patients with VaD and mild AD presented a marked reduction of SL at both fronto-parietal (delta-alpha) and inter-hemispherical (delta-beta) electrode pairs. The feature distinguishing the patients with mild AD with respect to patients with VaD groups was a more prominent reduction of fronto-parietal alpha 1 SL. These results suggest that mild AD is characterized by an abnormal fronto-parietal coupling of the dominant human cortical rhythm at 8-10.5 Hz.