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PubMed1988

Interaction between diltiazem and halothane or enflurane in the canine blood-perfused papillary muscle and sinoatrial node preparations cross-circulated by chronically instrumented conscious donor dog.

Interaction of cardiovascular effects of diltiazem with those of halothane or enflurane was estimated in the canine isolated papillary muscle and sinoatrial node preparations perfused by arterial blood of the chronically instrumented conscious and halothane- or enflurane-anesthetized donor dog, into which diltiazem was infused i.v. at a rate of 20 micro g/kg/min for 60 min. One hour after diltiazem infusion, in the conscious donor dog, mean arterial pressure (MAP) and heart rate (DHR) were decreased to 84 +/- 3 and 84 +/- 2% and PQ interval (PQ) was prolonged to 148 +/- 5%, while in the isolated preparations, developed tension (DT) of the papillary muscle and sinoatrial rate (SAR) were decreased to 68 +/- 3 and 74 +/- 3% and blood flow (BF) was increased to 155 +/- 5% (n = 10). On the other hand, halothane (0.8%) anesthesia per se decreased MAP, DHR, DT and SAR to 89 +/- 8, 84 +/- 3, 79 +/- 3 and 89 +/- 5% (n = 7) of each basal value in conscious state 20 min after the inhalation. During halothane anesthesia, the same dose of diltiazem infused decreased MAP to 74 +/- 4 (n = 7), DHR to 66 +/- 4 (n = 6), DT to 62 +/- 7 (n = 7) and SAR to 69 +/- 1% (n = 3) of each value suppressed by halothane itself. Meanwhile, enflurane (1.7%) anesthesia itself decreased MAP, DHR, DT and SAR to 81 +/- 3, 85 +/- 2, 81 +/- 2 and 88 +/- 2% (n = 10) of each basal value in conscious state 30 min after enflurane inhalation. During enflurane anesthesia diltiazem decreased MAP to 74 +/- 3 (n = 10), DHR to 67 +/- 3 (n = 8), DT to 45 +/- 5 (n = 10) and SAR to 74 +/- 6% (n = 3) of each value under enflurane anesthesia alone. PQ interval of the donor dog heart was prolonged by halothane alone to 111 +/- 5% (n = 7) and by enflurane alone to 110 +/- 2% (n = 10) of the value before each anesthesia, and then diltiazem prolonged PQ interval to 160 +/- 8% (n = 6) and 174 +/- 10% (n = 8) of each value suppressed by the anesthetic itself during halothane- or enflurane-anesthesia, respectively. The second degree AV conduction block was induced in 1 of 7 halothane- and in 2 of 10 enflurane-anesthetized donor dogs, respectively. The sinus arrest was induced by diltiazem in 4 of 7 sinoatrial node preparations under halothane and in 7 of 10 ones during enflurane anesthesia. Moreover, plasma concentration of diltiazem 60 min after the start of infusion was 556 +/- 121 ng/ml in conscious dogs and tended to increase to 752 +/- 101 ng/ml in enflurane anesthetized donor dogs (n = 4), but there was no significant difference between two values (0.05 < P < 0.1). These results indicate that effects of diltiazem could be potentiated during halothane or enflurane anesthesia by elimination of compensatory reflex noted in conscious state, and that the negative inotropic effect of diltiazem was enhanced by enflurane anesthesia due to unknown mechanisms which probably include a slight but insignificant increase in plasma concentration.

Journal Article↗
PubMed1982

Evaluation and outcome of emergency room patients with transient loss of consciousness.

We identified 198 patients who presented to our emergency room with transient loss of consciousness. Seizures (29 percent of patients) and vasovagal/psychogenic episodes (40 percent of patients) were the most common presumptive causes of loss of consciousness, but the cause of loss of consciousness remained uncertain even at follow-up in 11 +/- 6 months in 13 percent of the patients. The history and physical examinations were sufficient for diagnosis in 85 percent of the patients in whom a diagnosis could be established. These data guided inpatient and outpatient with potentially dangerous causes of loss of consciousness except for one patient who had pulmonary embolism. In selected patient, diagnostic tests such as blood chemistries (three patients), electrocardiograms (four patients) electroencephalograms (three patients), and Holter monitoring (four patients) provided crucial information, and CT scans identified new brain tumors in four patients with focal neurologic presentations. At the time of follow-up, 7.5 percent of patients had suffered either major morbidity or death related to the cause of the index episode of loss of consciousness. Patients with cardiac causes represented a high risk (33 percent) group for such poor outcome, whereas patients who were under age 30, or who were under age 70 and had loss of consciousness on a vasovagal/psychogenic or unknown basis, constituted a low risk (1 percent) subgroup.

Adult↗
PubMed1993

Changes in nociception, arterial blood pressure and heart rate produced by intravenous morphine in the conscious rat.

The present study shows that intravenous (i.v.) administration of morphine produces dose-dependent increases in tail flick and hot plate latencies in conscious rats. I.v. morphine also decreased heart rate, but had no significant effects on arterial blood pressure. Transection of the right vagus at the cervical level or pre-treatment with the peripherally acting opioid receptor antagonist naloxone methobromide attenuated the increased tail flick latency produced by either 1.75 or 2.5 mg/kg morphine. In addition, either right vagotomy or naloxone methobromide attenuated the increased hot plate latency produced by 1.75 mg/kg of morphine but not by 2.5 mg/kg of morphine. Following pre-treatment with naloxone methobromide, 1.75 and 2.5 mg/kg of morphine produced a small pressor response 1-3 min after injection. The bradycardia produced by 1.75 mg/kg of morphine was attenuated by naloxone methobromide, but not by right vagotomy. The bradycardia produced by 2.5 mg/kg of morphine was attenuated by either naloxone methobromide or vagotomy. These data obtained in the conscious rat are similar to previous reports using pentobarbital-anesthetized rats except for the following: (i) the dose-response function for inhibition of the tail flick was shifted to the right in conscious rats, (ii) the depressor response to morphine observed in anesthetized rats was attenuated in conscious rats, (iii) following naloxone methobromide, but not unilateral vagotomy, i.v. morphine produced a pressor response in the conscious rat, and (iv) unilateral vagotomy was not as effective in attenuating the antinociception and bradycardia in conscious rats as bilateral vagotomy is in pentobarbital-anesthetized rats.

Animals↗
PubMed1990

Requirement for solutions with oncotic pressure to release ANF during blood volume expansion in conscious and anesthetized rats.

We examined the effect of a 30% blood volume expansion with either blood, isotonic saline, or isotonic saline plus albumin on the release of immunoreactive-atrial natriuretic factor (IR-ANF) in conscious and barbiturate-anesthetized rats. Immediately prior to volume expansion, resting plasma IR-ANF levels were significantly (p less than 0.05) higher in the conscious animals (61 +/- 5 pg/mL, n = 19) compared to the anesthetized animals (41 +/- 3 pg/mL, n = 19). Volume expansion with blood from donor rats significantly (p less than 0.05) elevated IR-ANF in both groups, but the increase in the conscious rats (+492 +/- 32 pg/mL, n = 6) was significantly (p less than 0.05) greater than that of the anesthetized rats (74 +/- 25 pg/mL, n = 6). Similarly, volume expansion with isotonic saline containing 38 mg/mL albumin significantly (p less than 0.05) elevated IR-ANF levels in both groups, but the increase in the conscious group (379 +/- 102 pg/mL, n = 7) was significantly (p less than 0.05) greater than that of the anesthetized group (94 +/- 32 pg/mL, n = 7). These elevations in IR-ANF levels were not significantly different between either of the conscious groups or either of the anesthetized groups. Volume expansion with isotonic saline alone did not have any significant effect upon resting IR-ANF levels in either conscious (+8 +/- 14 pg/mL, n = 6) or anesthetized (-7 +/- 6 pg/mL, n = 6) animals. From these results, it would appear that a) isotonic saline alone does not stimulate IR-ANF release when used to expand blood volume, and b) barbiturate anesthesia significantly lowers resting plasma IR-ANF levels and attenuates the release of IR-ANF in response to volume expansion.

Albumins↗
PubMedDate not supplied

Separate neural definitions of visual consciousness and visual attention; a case for phenomenal awareness.

What is the relation between visual attention and visual awareness? It is difficult to imagine being aware of something without attending to it, and by some, visual consciousness is simply equated to what is in the focus of attention. However, findings from psychological as well as from neurophysiological experiments argue strongly against equating attention and visual consciousness. From these experiments clearly separate neural definitions of visual attention and visual consciousness emerge. In the model proposed here, visual attention is defined as a convolution of sensori-motor processing with memory. Consciousness, however, is generated by recurrent activity between cortical areas. The extent to which these recurrent interactions involve areas in executive or mnemonic space depends on attention and determines whether a conscious report is possible about the sensory experience, not whether the sensory experience is there. This way, a strong case can be made for a pure non-cognitive form of seeing, independent of attentional selection, called phenomenal awareness. This can be dissociated from the reportable form, depending on attention, called access awareness. The hypothesis explains why attention and consciousness seem so intricately related, even though they are fully separate phenomena.

Attention↗
PubMed2006

Chronic disorders of consciousness.

The vegetative state and the minimally conscious state are disorders of consciousness that can be acute and reversible or chronic and irreversible. Diffuse lesions of the thalami, cortical neurons, or the white-matter tracts that connect them cause the vegetative state, which is wakefulness without awareness. Functional imaging with PET and functional MRI shows activation of primary cortical areas with stimulation, but not of secondary areas or distributed neural networks that would indicate awareness. Vegetative state has a poor prognosis for recovery of awareness when present for more than a year in traumatic cases and for 3 months in non-traumatic cases. Patients in minimally conscious state are poorly responsive to stimuli, but show intermittent awareness behaviours. Indeed, findings of preliminary functional imaging studies suggest that some patients could have substantially intact awareness. The outcomes of minimally conscious state are variable. Stimulation treatments have been disappointing in vegetative state but occasionally improve minimally conscious state. Treatment decisions for patients in vegetative state or minimally conscious state should follow established ethical and legal principles and accepted practice guidelines of professional medical specialty societies.

Awareness↗
PubMed2001

Radical embodiment: neural dynamics and consciousness.

We propose a new approach to the neuroscience of consciousness, growing out of the 'enactive' viewpoint in cognitive science. This approach aims to map the neural substrates of consciousness at the level of large-scale, emergent and transient dynamical patterns of brain activity (rather than at the level of particular circuits or classes of neurons), and it suggests that the processes crucial for consciousness cut across the brain-body-world divisions, rather than being brain-bound neural events. Whereas standard approaches to the neural correlates of consciousness have assumed a one-way causal-explanatory relationship between internal neural representational systems and the contents of consciousness, our approach allows for theories and hypotheses about the two-way or reciprocal relationship between embodied conscious states and local neuronal activity.

Journal Article↗
PubMed2004

Performance of bispectral index and auditory evoked potential monitors in detecting loss of consciousness during anaesthetic induction with propofol with and without fentanyl.

BACKGROUND AND OBJECTIVE: To investigate and compare the performance of bispectral index (BIS) and auditory evoked response index (AAI) in detecting the transition from consciousness to unconsciousness during anaesthesia induction by propofol, alone and in combination with fentanyl. METHODS: Anaesthesia was induced with either an intravenous infusion of 30 mg kg(-1)h(-1) of propofol plus 2 microg kg(-1) of fentanyl (Group PF, n = 20) or an intravenous infusion of 30 mg kg(-1) h(-1) of propofol plus normal saline (Group P, n = 20). BIS, AAI and the doses of propofol administered were recorded at the end-point of unresponsiveness to verbal commands. The propofol plasma concentration was also measured. RESULTS: The propofol dose and plasma propofol concentration required to achieve loss of consciousness were significantly lower in patients pretreated with fentanyl (P < 0.001). The mean BIS value at loss of consciousness was significantly different between the two groups (74.10 in Group PF vs. 60.80 in Group P) (P < 0.001). However, no difference in the AAI was seen between the two groups at loss of consciousness (32.90 in Group PF vs. 31.80 in Group P) (P > 0.05). In both groups, the regression analysis values (r-values) between BIS and plasma propofol concentrations at the onset of unconsciousness were higher than those between AAI and propofol concentrations (0.553 vs. 0.180 in Group P; 0.432 vs. 0.308 in Group PF). CONCLUSIONS: These results show that a fentanyl bolus is effective in augmenting the hypnotic effect of propofol during anaesthesia induction. AAI appears to be able to measure the transition from consciousness to unconsciousness at similar values, regardless of whether or not fentanyl pretreatment is used whereas the BIS values were not independent of fentanyl pretreatment. This suggests that AAI may be a better indicator of conscious status during propofol/fentanyl anaesthesia, where it appears to be independent of the anaesthesia regimen.

Adolescent↗
PubMed1983

The roles of self-esteem and self-consciousness in the Wortman-Brehm model of reactance and learned helplessness.

The present experiments were designed to study the conditions under which failure would enhance or inhibit subsequent task performance. Based on the theory of Wortman and Brehm (1975), it was expected that small amounts of failure would produce reactance (manifested by improved performance at a subsequent task), whereas large amounts would lead to learned helplessness (i.e., impaired later performance). It was further expected that individual differences in self-esteem and private self-consciousness would serve as moderator variables for the above effects. In Experiment 1, subjects were exposed to either a small amount of failure or no failure before working on an anagrams task. As predicted, subjects high in self-consciousness, who have shown greater reactance arousal in attitude change studies, performed better on the anagrams task than subjects low in self-consciousness in the small-failure condition, but not in the no-failure condition. Further analyses revealed that this Self-Consciousness X Small Failure interaction was attributable to the performance data of the low, but not the high self-esteem subjects. Experiment 2 was designed to replicate and extend these results. Subjects were pretreated with either a small amount of failure, an extended amount of failure, or no failure before working on the anagrams task. A significant Self-Esteem X Helplessness Training interaction emerged. Relative to the no-failure condition, in which the two self-esteem groups did not differ, low self-esteem participants (low SEs) performed marginally better than did high self-esteem individuals (high SEs) in the small-failure condition but significantly worse than high SEs in the extended-failure condition. The effect of private self-consciousness was considerably weaker in this study, possibly because the sample included few low SEs (who are especially influenced by self-focused attention) who were also relatively low in self-consciousness. Questionnaire data from Experiment 2 were consistent with the notion that enhanced performance reflected reactance, whereas impaired performance signified helplessness.

Arousal↗
PubMed1999

Impairment of consciously controlled use of memory in schizophrenia.

Recent studies of memory in schizophrenia have shown that explicit but not implicit memory performance is impaired. The hypothesis that schizophrenia is associated with a failure of consciously but not unconsciously (automatic) controlled influence of memory on performance was tested using a procedure providing uncontaminated estimates of consciously controlled and automatic memory processes (i.e., the process-dissociation procedure in a stem completion task). Performance of 35 patients with schizophrenia was compared with that of 35 normal participants. Consciously controlled use but not automatic influences of memory was significantly lower in patients with schizophrenia than in controls. Consciously controlled use of memory was negatively and significantly correlated with positive symptoms of schizophrenia. Schizophrenia differentially affects 2 types of memory processes: It impairs consciously controlled use of memory but spares automatic influences. Positive symptoms could reflect the lack of control from higher level conscious processes.

Adult↗
PubMed2004

Deceiving oneself about being in control: conscious detection of changes in visuomotor coupling.

Previous research has demonstrated that compensatory movements for changes in visuomotor coupling often are not consciously detected. But what factors affect the conscious detection of such changes? This issue was addressed in 4 experiments. Participants carried out a drawing task in which the relative velocity between the actual movement and its visual consequences was perturbed. Unconscious compensatory movements and conscious detection rates were simultaneously recorded. There was an invariant relationship between the extent of the change and its conscious detection that was proportional to the initial drawing velocity. This suggests that conscious change detection relies on a system that integrates visual and motor information-as, for instance, suggested by the internal model theory of motor control. Figural discrepancies increased the detection rates, indicating that additional cues for the what system facilitate conscious change detection.

Adult↗
PubMed2006

Individual differences in the "Greek effect" on risky drinking: the role of self-consciousness.

Although the environmental influence of Greek affiliation on drinking has been established, little is known about intrapersonal characteristics that make individuals susceptible to this influence. Self-consciousness (attending to one's self) was hypothesized to represent dispositional vulnerability to environmental influence. The potential moderating effect of self-consciousness on the relation between Greek involvement and drinking was examined longitudinally among college students (N = 319). The effect of Greek status was moderated by private and public self-consciousness and by gender. Specifically, non-Greek members' drinking was not influenced by self-consciousness. However, sorority members increased drinking as private self-consciousness increased, whereas fraternity members increased drinking as private and public self-consciousness decreased. These findings indicate that the "Greek effect" interacts with individual characteristics to affect drinking.

Adult↗
PubMed1991

Regional cerebral blood flow during spreading cortical depression in conscious rats.

Spreading cortical depression (SCD) of EEG activity was induced in one cerebral hemisphere of conscious restrained rats by direct current stimulation of the lateral frontal cortex. Regional CBF was measured using [14C]iodoantipyrine and brain dissection. An early phase of increased CBF was not measured in conscious rats, but an early relative hyperperfusion was measured if the resting CBF was first reduced by treatment with pentobarbital or indomethacin. A long-lasting reduction in CBF was measured in conscious rats following the passage of SCD. This flow reduction resolved after 3 h. In conscious rats, CBF decreased in the striatum and thalamus ipsilateral to the SCD, paralleling the CBF changes occurring in the cortex. The CBF change in these deep structures was abolished by pentobarbital. An early transient increase in regional CBF was measured in the cerebral cortex contralateral to the hemisphere involved with SCD in conscious rats. This early contralateral hyperperfusion was also abolished by pentobarbital or indomethacin but not by atropine or propranolol. The vascular response to SCD in conscious rats differs from that which occurs in anesthetized rats.

Animals↗
PubMed2003

Intravenous conscious sedation in patients under 16 years of age. Fact or fiction?

Recently published guidelines on the use of conscious sedation in dentistry have published varying recommendations on the lower age limit for the use of intravenous conscious sedation. There are a large number of dentists currently providing dental treatment for paediatric patients under intravenous conscious sedation. The 18 cases reported here (age range 11-15 years), were successfully managed with intravenous conscious sedation. The experience in this paper is not sufficient evidence to recommend the wholesale use of intravenous conscious sedation in patients who are under 16 years. The fact that a range of operators can use these techniques on paediatric patients would suggest that further study should be carried out in this population. The guidance should be modified to say there is insufficient evidence to support the use of intravenous conscious sedation in children, rather than arbitrarily selecting a cut off point at age 16 years.

Adolescent↗
PubMed2000

Conscious sedation of pediatric patients with combination oral benzodiazepines and inhaled nitrous oxide.

BACKGROUND: Pediatric patients undergoing surgical procedures may experience considerable anxiety. Use of conscious sedation may be helpful in managing mild to moderate anxiety. OBJECTIVE: To assess the effectiveness of combination oral benzodiazepines and inhaled nitrous oxide conscious sedation in pediatric surgical patients. METHODS: Eleven episodes of conscious sedation in eight pediatric patients were prospectively monitored, with recording of indications, patient characteristics, clinical scenarios, surgical procedure, sedative regimen, quality of sedation, and complications. Extensive training in conscious sedation had been obtained, and emergency preparedness was at a high level. RESULTS: Combination oral benzodiazepines and inhaled nitrous oxide produced good to excellent results in all patients but one. Complications were uncommon and mild. No emergency intervention was necessary. CONCLUSION: Monitored use of a combination of oral benzodiazepine and low to moderate concentrations of inhaled nitrous oxide can provide safe and effective conscious sedation in pediatric patients. Training in conscious sedation and emergency preparedness are essential.

Administration, Inhalation↗
PubMed1981

Pancreatic response of anaesthetized and conscious rats to bolus injection of cholecystokinin-pancreozymin.

Pancreatic secretion was studied in anaesthetized rats tested immediately after surgery or in conscious rats tested 48 hr after the cannulation of the pancreatic duct. Pancreatic flow, protein output and enzyme output were measured over a 30-min period in the unstimulated state and after the intravenous injection of bolus doses of cholecystokinin-pancreozymin (CCK-PZ) ranging from 1.25 to 20 Crick-Harper-Raper units (CHRU). Each animal received three doses of CCK-PZ, as either ascending or descending doses. In anaesthetized rats there was a linear relationship between the log-dose of CCK-PZ and the flow, protein and enzyme output with both the ascending and descending doses. In contrast, in conscious rats flow was unaffected by CCK-PZ, and protein output was greatest after the first dose, whether this was given in the ascending or descending doses. At all CCK-PZ levels flow in anaesthetized rats was less than that seen in conscious animals, but at doses of CCK-PZ above 5.00 CHRU protein output was greater in anaesthetized rats than in conscious rats. Ultrastructural studies of the pancreas showed areas of focal cytoplasmic degeneration and possible blockage of the duct with cellular debris after administration of high doses of CCK-PZ to conscious rats. These changes may be responsible for the reduced protein output with the second and third dose of CCK-PZ in these animals. No such changes were seen in anaesthetized rats after similar doses of CCK-PZ. These studies show fundamental differences in the response of the pancreas to CCK-PZ in anaesthetized and conscious rats. The mechanism for this difference is not clear, but it may represent a change in the normal response to CCK-PZ in the anaesthetized rats as a result of the effects of acute operative trauma, possibly acting through changes in pancreatic blood flow.

Amylases↗
PubMed2006

Disturbances of time consciousness from a phenomenological and a neuroscientific perspective.

The subjective experience of time is a fundamental constituent of human consciousness and can be disturbed under conditions of mental disorders such as schizophrenia or affective disorders. Besides the scientific domain of psychiatry, time consciousness is a topic that has been extensively studied both by theoretical philosophy and cognitive neuroscience. It can be shown that both approaches exemplified by the philosophical analysis of time consciousness (Husserl) and the neuroscientific theory of cross-temporal contingencies (binding of cognitive processes over time) as the neurophysiological basis of human consciousness implemented in the prefrontal cortex (Fuster) converge in 2 respects. Firstly, a tripartite conception of consciousness divides human cognition in 3 different temporal domains comprising retention, presentation, and protention (Husserl) and the past, the present, and the future corresponding to working memory, interference control, and preparatory set (Fuster). Secondly, both concepts refer to the present as an extended duration that integrates information from the recent past and the future. We propose that the integration of phenomenological and neuroscientific approaches can stimulate the development of enriched pathophysiological concepts of mental disorders. This approach appears to be particularly fruitful with respect to schizophrenia that is interpreted as a structural disturbance of time consciousness.

Awareness↗
PubMed2001

Early pregnancy does not reduce the C(50) of propofol for loss of consciousness.

UNLABELLED: Requirements for inhaled anesthetics decrease during pregnancy. There are no published data, however, regarding propofol requirements in these patients. Because propofol is often used for induction of general anesthesia when surgery is necessary in early pregnancy, we investigated whether early pregnancy reduces the requirement of propofol for loss of consciousness using a computer-assisted target-controlled infusion (TCI). Propofol was administered using TCI to provide stable concentrations and to allow equilibration between blood and effect-site (central compartment) concentrations. Randomly selected target concentrations of propofol (1.5-4.5 microg/mL) were administered to both pregnant women (n = 36) who were scheduled for pregnancy termination and nonpregnant women (n = 36) who were scheduled for elective orthopedic or otorhinolaryngologic surgery. The median gestation of the pregnant women was 8 wk (range, 6-12 wk). Venous blood samples for analysis of the serum propofol concentration were taken at 3 min and 8 min after equilibration of the propofol concentration. After a 10-min equilibration period of the predetermined propofol blood concentration, a verbal command to open their eyes was given to the patients twice, accompanied by rubbing of their shoulders. Serum propofol concentrations at which 50% of the patients did not respond to verbal commands (C(50) for loss of consciousness) were determined by logistic regression. There was no significant difference in C(50) +/- SE of propofol for loss of consciousness between the Nonpregnant (2.1 +/- 0.2 microg/mL) and Pregnant (2.0 +/- 0.2 microg/mL) groups. These results indicate that early pregnancy does not decrease the concentration of propofol required for loss of consciousness. IMPLICATIONS: The C(50) of propofol for loss of consciousness in early pregnancy did not differ from that in nonpregnant women, indicating that there is no need to decrease the propofol concentration for loss of consciousness when inducing general anesthesia for termination of pregnancy.

Abortion, Induced↗