Pro/con clinical debate: tracheostomy is ideal for withdrawal of mechanical ventilation in severe neurological impairment.
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Most clinical trials on the topic of extubation have involved patients outside the neurological intensive care unit. As a result, in this area clinicians are left with little evidence on which to base their decision making. Although tracheostomies are increasingly common procedures, they are not without complications and costs, and hence a decision to perform them should not be taken lightly. In this issue of Critical Care two groups debate the merits of tracheostomy before extubation in a patient with neurological impairment. What becomes very clear is the need for more high quality data for this common clinical problem. (+info)
Narcotrend does not adequately detect the transition between awareness and unconsciousness in surgical patients.
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BACKGROUND: The Narcotrend index (MonitorTechnik, Bad Bramstedt, Germany) is a dimensionless number between 0 and 100 that is calculated from the electroencephalogram and inversely correlates with depth of hypnosis. The current study evaluates the capability of the Narcotrend to separate awareness from unconsciousness at the transition between these levels. METHODS: Electroencephalographic recordings of 40 unpremedicated patients undergoing elective surgery were analyzed. Patients were randomly assigned to receive (1) sevoflurane-remifentanil (/= 0.2 microg . kg . min), (3) propofol-remifentanil (/= 0.2 microg . kg . min). Remifentanil and sevoflurane or propofol were given until loss of consciousness. After tracheal intubation, propofol or sevoflurane was stopped until return of consciousness and then restarted to induce loss of consciousness. After surgery, drugs were discontinued. Narcotrend values at loss and return of consciousness were compared with each other, and anesthetic groups were compared. Prediction probability was calculated from values at the last command before and at loss and return of consciousness. RESULTS: At 105 of 316 analyzed time points, the Narcotrend did not calculate an index, and the closest calculated value was analyzed. No significant differences between loss and return of consciousness were found. In group 1, Narcotrend values were significantly higher than in group 3. Prediction probability was 0.501. CONCLUSIONS: In these challenging data, the Narcotrend did not differentiate between awareness and unconsciousness. In addition, Narcotrend values were not independent from the anesthetic regimen. (+info)
Individual effect-site concentrations of propofol are similar at loss of consciousness and at awakening.
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Reported effect-site concentrations of propofol at loss of consciousness and recovery of consciousness vary widely. Thus, no single concentration based on a population average will prove optimal for individual patients. We therefore tested the hypothesis that individual propofol effect-site concentrations at loss and return of consciousness are similar. Propofol effect-site concentrations at loss and recovery of consciousness were estimated with a target-control infusion system in 20 adults. Propofol effect-site concentrations were gradually increased until the volunteers lost consciousness (no response to verbal stimuli); unconsciousness was maintained for 15 min, and the volunteers were then awakened. This protocol was repeated three times in each volunteer. Our major outcomes were the concentration producing unconsciousness and the relationship between the estimated effect-site concentrations at loss and recovery of consciousness. The target effect-site propofol concentration was 2.0 +/- 0.9 at loss of consciousness and 1.8 +/- 0.7 at return of consciousness (P <0.001). The average difference between individual effect-site concentrations at return and loss of consciousness was only 0.17 +/- 0.32 microg/mL (95% confidence interval for the difference 0.09-0.25 microg/mL). Our results thus suggest that individual titration to loss of consciousness is an alternative to dosing propofol on the basis of average population requirements. (+info)
Giant intrasellar arachnoid cyst manifesting as adrenal insufficiency due to hypothalamic dysfunction--case report--.
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A 67-year-old man first noticed loss of pubic and axillary hair in 1992 and then a visual field defect in 2001. He experienced loss of consciousness attributed to hyponatremia in April 2002. Magnetic resonance imaging showed a giant intrasellar cystic mass, 40 mm in diameter, that had compressed the optic chiasm. The patient complained of chronic headache, and neurological examination revealed bitemporal hemianopsia. Preoperative endocrinological examination indicated adrenal insufficiency, and hypothyroidism due to hypothalamic dysfunction. The patient underwent endonasal transsphenoidal surgery. The cyst membrane was opened and serous fluid was drained. Histological examination identified the excised cyst membrane as arachnoid membrane. The patient's headaches resolved postoperatively, but the bitemporal hemianopsia and endocrinological function were unchanged. This arachnoid cyst associated with hypothalamic dysfunction might have been caused by an inflammatory episode in the suprasellar region. (+info)
Quantification of motor cortex activity and full-body biomechanics during unconstrained locomotion.
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Recent progress in the understanding of motor cortex function has been achieved primarily by simultaneously recording motor cortex neuron activity and the movement kinematics of the corresponding limb. We have expanded this approach by combining high-quality cortical single-unit activity recordings with synchronized recordings of full-body kinematics and kinetics in the freely behaving cat. The method is illustrated by selected results obtained from two cats tested while walking on a flat surface. Using this method, the activity of 43 pyramidal tract neurons (PTNs) was recorded, averaged over 10 bins of a locomotion cycle, and compared with full-body mechanics by means of principal component and multivariate linear regression analyses. Patterns of 24 PTNs (56%) and 219 biomechanical variables (73%) were classified into just four groups of inter-correlated variables that accounted for 91% of the total variance, indicating that many of the recorded variables had similar patterns. The ensemble activity of different groups of two to eight PTNs accurately predicted the 10-bin patterns of all biomechanical variables (neural decoding) and vice versa; different small groups of mechanical variables accurately predicted the 10-bin pattern of each PTN (neural encoding). We conclude that comparison of motor cortex activity with full-body biomechanics may be a useful tool in further elucidating the function of the motor cortex. (+info)
Amnesia for loss of consciousness in carotid sinus syndrome: implications for presentation with falls.
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OBJECTIVES: The goal of this study was to compare the clinical characteristics of patients with carotid sinus syndrome who presented with falls with those who presented with syncope. BACKGROUND: Carotid sinus syndrome presents with both falls and syncope. The reasons for this differential presentation are unknown, but amnesia for loss of consciousness may be the underlying cause. METHODS: Two groups of 34 consecutive patients with carotid sinus syndrome as the sole cause of falls and syncope were recruited. Cognitive function and clinical characteristics were compared between the two groups. RESULTS: Syncopal subjects with carotid sinus syndrome were more likely to be older males (18 [53%] vs. 7 [21%] years; p = 0.006) with a longer duration of symptoms (27.9 vs. 13.3 months; p = 0.009) and more soft tissue injuries (19 [56%] vs. 9 [26%]; p = 0.03). Duration of asystole during carotid sinus massage was similar in both groups (5.1 vs. 5.4 s; p = 0.42), but witnessed amnesia for loss of consciousness was more frequent in fallers than those with syncope (21 [95%] vs. 4 [12%]; p < 0.001). Clinical characteristics and cognitive function were otherwise similar in both groups. CONCLUSIONS: Patients with carotid sinus syndrome have similar rates of witnessed loss of consciousness during laboratory testing regardless of symptoms. However, those presenting with falls are far less likely to perceive any disturbance of consciousness than those with syncope, showing for the first time the manner in which such patients manifest symptoms. Cognitive impairment does not explain the amnesia for loss of consciousness seen in fallers with carotid sinus syndrome. (+info)
Effect of blood-letting puncture at twelve well-points of hand on consciousness and heart rate in patients with apoplexy.
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OBJECTIVE: To observe the effect of blood-letting puncture at Twelve Well-Points of Hand on consciousness and heart rate in patients with early apoplexy. METHOD: Under observation were patients with disturbance of consciousness within 3 days after the apoplectic seizure. The patients were divided into a large injury team, a moderate injury team and a mild injury team. Each team was again randomly divided into a puncture group and a control group, with routine treatment in both groups but blood-letting puncture only in the puncture group. Quantitative changes in consciousness, blood pressure and heart rate of the patients were observed. RESULT: Blood-letting puncture at Twelve Well-Points of Hand can improve the consciousness and raise the systolic pressure in patients of the mild injury team, and accelerate the heart rate in all the patients in the puncture group. CONCLUSION: Blood-letting puncture at Twelve Well-Points of Hand can improve the consciousness of patients with brain injury in small area. (+info)
Usefulness of delayed enhancement magnetic resonance imaging for detecting cardiac rupture caused by small myocardial infarction in a case of cardiac tamponade.
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Delayed enhancement magnetic resonance imaging (DE-MRI) has excellent spatial resolution and compared with other cardiac imaging techniques it can detect a small myocardial infarction (MI) or a subendocardial infarction. A 76-year-old man was admitted for loss of consciousness because of cardiac tamponade. The cause of tamponade was unknown, but electrocardiography and blood test suggested a recent MI. The removal of 100 ml bloody fluid by immediate pericardiocentesis normalized his hemodynamics, and he regained consciousness. Neither echocardiography nor scintigraphy could determine the location of the MI or rupture, but DE-MRI clearly demonstrated a transmural enhancement in a very narrow range of the lateral wall of the left ventricle. Coronary angiography revealed a severely stenotic lesion in the obtuse marginal branch of the left circumflex artery. DE-MRI is a powerful tool for diagnosing small MI that are undetectable with other imaging. Therefore, DE-MRI should be applied in cases with cardiac tamponade by unknown causes. (+info)