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PubMed1992

Evolution of consciousness.

The hypothesis of the origin of consciousness is built upon the unique properties of the mammalian neocortex. The apical dendrites of the pyramidal cells bundle together as they ascend to lamina I to form neural receptor units of approximately 100 apical dendrites plus branches receiving hundreds of thousands of excitatory synapses, the collective assemblage being called a dendron. It is proposed that the whole world of consciousness, the mental world, is microgranular, with mental units called psychons, and that in mind-brain interaction one psychon is linked to one dendron through quantum physics. The hypothesis is that in mammalian evolution dendrons evolved for more effective integration of the increased complexity of sensory inputs. These evolved dendrons had the capacity for interacting with psychons that came to exist, so forming the mental world and giving the mammal conscious experiences. In Darwinian evolution, consciousness would have occurred initially some 200 million years ago in relation to the primitive cerebral cortices of evolving mammals. It would give global experiences of a surrounding world for guiding behavior beyond what is given by the unconscious operation of sensory cortical areas per se. So conscious experiences would give mammals evolutionary advantage over the reptiles, which lack a neocortex giving consciousness. The Wulst of the avian brain needs further investigation to discover how it could give birds the consciousness that they seem to have.

Animals↗
PubMed1982

Human consciousness and sleep/waking rhythms: a review and some neuropsychological considerations.

The relevance of sleep/waking rhythms to issues of human consciousness is reviewed from data in the literature and from personal studies. Consciousness is often considered to be markedly attenuated or absent in sleep. There is, however, much evidence for a rich subjective experience during sleep, much of which is not recalled later. This implies that William James' "stream of consciousness' persists continuously throughout sleep as well as wakefulness, but that problems of memory recall interfere with its being reported as such. Sleeping subjects show selective awareness of external stimuli, with significant stimuli generally leading to awakening and relatively nonsignificant stimuli, at least at times, being incorporated into the ongoing mental activity of REM or NREM sleep. Mentation throughout sleep is characterized by a high degree of autonomy and little willful control. Creative insight and problem solving of a very high order may occur in sleep and involve either dreaming or thought-like mentation. Parameters of waking consciousness show possibly sleep-related rhythmic fluctuations at both circadian (24 hr sleep/waking) and ultradian (90-120) min, NREM/REM sleep) rates. Moreover, waking consciousness is markedly influenced by the quality of temporal stability of preceding sleep. A substantial number of so-called "altered states of consciousness" is found to involve primarily or exclusively dysfunction of sleep/waking mechanisms. Cerebral lesions can produce selective impairment of aspects of sleep mentation. It is concluded that further analysis of subjective awareness in sleep or in partial sleep states is very relevant and indeed vital to a more comprehensive understanding of human consciousness.

Arousal↗
PubMed1994

Left ventricular mechanical consequences of dihydropyridine calcium channel modulation in conscious and anesthetized chronically instrumented dogs.

BACKGROUND: Volatile anesthetics depress left ventricular contractile function by altering voltage-dependent slow calcium (Ca2+) channel activity in the sarcolemmal membrane. This investigation examined the left ventricular systolic and diastolic mechanical effects of the dihydropyridine Ca2+ channel antagonist nifedipine and agonist Bay k 8644 (Bay k) in dogs in the conscious state and during anesthesia. METHODS: Forty-eight experiments were conducted using 16 chronically instrumented dogs during autonomic nervous system blockade. Myocardial contractility was evaluated with the slope (Mw) of the regional preload recruitable stroke work relationship. Diastolic function was assessed using a time constant of isovolumic relaxation (tau), a regional chamber stiffness constant (Kp), and maximum segment lengthening velocity during rapid ventricular filling (dL/dtmax). On 3 separate days (24 experiments), a nifedipine infusion at 0.5, 1.0, 2.0, or 4.0 micrograms.kg-1.min-1 was administered. Hemodynamics and left ventricular pressure-segment length diagrams were recorded after a 10-min equilibration at each dose in the conscious state or during isoflurane or halothane anesthesia (0.8 MAC). In 24 parallel experiments, a Bay k infusion at 0.5, 1.0, 2.0, or 4.0 micrograms.kg-1.min-1 was administered, and hemodynamics and left ventricular function parameters were assessed after a 10-min equilibration in the conscious state or during isoflurane or halothane administration (1.2 MAC). RESULTS: In conscious dogs, nifedipine significantly (P < 0.05) decreased Mw (71 +/- 5 to 42 +/- 4 mmHg during the high dose) and increased tau (35 +/- 1 to 48 +/- 3 ms during the high dose) without changes in dL/dtmax or Kp. In anesthetized dogs, nifedipine decreased Mw and dL/dtmax) (31 +/- 4 during isoflurane to 27 +/- 3 mm/s during the high dose) and increased tau and Kp (0.43 +/- 0.05 during isoflurane to 0.53 +/- 0.04 mm-1 during the high dose). Administration of Bay k increased Mw, decreased tau, and increased dL/dtmax in conscious dogs. In contrast, no changes in tau were observed in dogs anesthetized with isoflurane or halothane during infusions of Bay k despite concomitant increases in Mw. Bay k also enhanced dL/dtmax and decreased Kp during isoflurane but not halothane anesthesia. CONCLUSIONS: Nifedipine caused direct negative inotropic actions in conscious and anesthetized dogs and worsened volatile anesthetic-induced negative lusitropic effects. Bay k improved left ventricular systolic and diastolic function in the conscious state. Bay k also improved contractility during anesthesia; however, Bay k only partially reversed volatile anesthetic-induced abnormalities in indexes of left ventricular diastolic function in dogs during autonomic nervous system blockade.

3-Pyridinecarboxylic acid, 1,4-dihydro-2,6-dimethy↗
PubMed2004

Can bispectral index monitoring predict recovery of consciousness in patients with severe brain injury?

BACKGROUND: The probability of recovering consciousness in acute brain-injured patients depends on central nervous system damage and complications acquired during their stay in the intensive care unit. The objective of this study was to establish a relation between the Bispectral Index (BIS) and other variables derived from the analysis of the electroencephalographic signal, with the probability of recovering consciousness in patients in a coma state due to severe cerebral damage. METHODS: Twenty-five critically ill, unconscious brain-injured patients from whom sedative drugs were withdrawn at least 24 h before BIS recording were prospectively studied. BIS, 95% spectral edge frequency, burst suppression ratio, and frontal electromyography were recorded for 20 min. The neurologic condition of the patients was measured according to the Glasgow Coma Score (GCS). Patients were followed up for assessment of recovery of consciousness for 6 months after the injury. The studied variables were compared between the group of patients who recovered consciousness and those who did not recover. Their predictive ability was evaluated by means of the Pk statistic. Univariate and multivariate logistic regression was used to model the relation between variables and probability of recovery of consciousness. Cross-validation was used to validate the proposed model. RESULTS: There were statistically significant differences between the group of patients who recovered consciousness and those who did not with respect to BISmax, BISmin, BISmean, and BISrange, frontal electromyography, signal quality index values, and GCSBIS. The Pk (SE) values were 0.99 (0.01) for electromyelography, 0.96 (0.05) for BISmax, 0.92 (0.05) for BISmean, 0.92 (0.06) for BISrange, and 0.82 (0.09) for GCSBIS. The odds ratio for BISmax in the logistic regression model was 1.17 (95% confidence interval, 1.1-1.35). Cross-validation results reported a high-accuracy median absolute cross-validation performance error of 3.06% (95% confidence interval, 1-22.15%) and a low-bias median cross-validation performance error of 0.84% (0.56-2.12%). CONCLUSIONS: The study BIS and other electrophysiologic and clinical variables has enabled construction and cross-validation of a model relating BIS(max) to the probability of recovery of consciousness in patients in a coma state due to a severe brain injury, after sedation has been withdrawn.

APACHE↗
PubMed2003

Quality of life philosophy IV. The brain and consciousness.

In this article we look at the brain's structure and function from a philosophical perspective. Although the brain at micro-level, with its trillions of ultra-thin nerve fibers, is one of the most complicated structures in the known universe, you can still grasp its composition if you go up to the level of the cell. How this structure functions is not quite clear. You can understand its function at fiber level, because it is fairly simple, and you can understand it at cell level, but it is already vague. Roughly speaking, you can envision a single nerve cell as a tiny, independent computer whose behavior is dependent on continuous calculations of all input. At organ level, the function can be understood as an extremely complex pattern machine. Finally, the brain"s function can be understood at the cognitive level as what provides consciousness through its ability to keep order in our complicated reality. The superior function of the brain is to connect the real us, our higher self, to the surrounding world. The brain has been developed so that it can create all possible complex patterns. The connectivity seems to imply that the patterns of the human brain are 1000-dimensional. It is our vision that these complicated patterns arise from basic patterns in the quantum matter of which everything is created. In our opinion, our consciousness" special utilization of a patterned aspect of nature is what lies behind inscrutable statements like "Man is created in God"s image". We suggest that these patterns in matter are the basic, creative force that influences all living organisms. Unfortunately, science has only just begun to understand these patterns. The Bible's description of the origin of man is two people eating from the Tree of Knowledge and as punishment they are expelled from the Garden of Eden. What does that mean? It means that, as conscious creatures, we no longer were an unproblematic, harmonious part of the world around us. The great question is why this consciousness about the world, provided by the brain, is not a gift that makes life better instead of getting us expelled from the Garden of Eden. We think that our real problem is the fact that we are still not in control of our consciousness. Instead of it serving us, we have become its slaves. If we come to understand brain and consciousness in order to solve this basic problem of our existence, we shall again be able to become a coherent part of the world, both as individuals and as a species. We share the vision that such an understanding of the problems of consciousness will make medical science holistic and will bring quality of life, health, and the ability to function to its patients.

Animals↗
PubMed2006

Postmodern consciousness in psychotherapy.

Modern consciousness is a cultural and historical achievement in the West and a developmental task for each person now. Modern consciousness consists in the emancipation from the power of community, animistic nature and the unconscious. It is connected with neurosis and psychotherapy because it has to do with inner conflicts. But today there is an increasing number of cases which are characterized by dissociation and acting out, without the feeling of conflicts. Consciousness seems to be changing toward a new conception which might be called 'postmodern consciousness'. The essence of postmodern consciousness is shown by interpreting two dreams internally. The first dream from a case of depersonalization indicates that it is not necessary to be entangled with the object. There is a different kind of coniunctio in the mode of seeing. The second dream from a case of dissociative disorder shows a world which has neither traces of pre-modern cosmology-high and low, here and the beyond-nor modern interiority. There is only surface and self-reflection without content. The discussion of dreams suggests that postmodern consciousness is not to be understood as premature and pathological. It is therapeutically important to refine and deepen postmodern consciousness.

Adult↗
PubMed2003

Lack of hemispheric dominance for consciousness in acute ischaemic stroke.

BACKGROUND: Previous reports have suggested left hemispheric dominance for maintaining consciousness, although there is controversy over this claim. OBJECTIVE: To compare early impairment of level of consciousness between patients with right and left hemispheric stroke. METHODS: Data from 564 patients with ischaemic stroke enrolled in the placebo arm of a trial of a putative neuroprotectant were analysed. All patients had major hemispheric stroke with cortical dysfunction, visual field deficit, and limb weakness, with symptom onset within 12 hours of enrolment. Patients were prospectively evaluated on a predefined scale (1-6; 1 = fully awake, higher scores representing greater impairment) to measure level of consciousness at multiple time points over the initial 24 hours after presentation. The National Institutes of Health (NIH) stroke scale score at presentation and infarct volume at 30 days were determined. RESULTS: Some degree of impairment in level of consciousness was observed in 409 of the 564 patients (73%). Median maximum sedation score was 2 for both right and left hemispheric stroke (p = 0.91). Mean sedation score over 24 hours was 1.5 for both right and left stroke (p = 0.75). There was no difference between level of consciousness scores in right and left stroke at any individual time point during the 24 hour monitoring period. No association between side and impairment in level of consciousness was seen after adjustment for stroke severity and infarct volume. CONCLUSIONS: In contrast to previous reports, there was no evidence for hemispheric dominance for consciousness in the setting of a major hemispheric stroke.

Aged↗
PubMed1990

Atrial natriuretic factor-induced systemic vasoconstriction in conscious dogs, rats, and monkeys.

This study addresses the hypothesis that atrial natriuretic factor (ANF) is a primary vasodilator, which reduces arterial pressure directly and increases total peripheral resistance secondarily by reflex mechanisms. The effects of 30-minute infusions of ANF (0.3 micrograms/kg/min i.v.) were examined in conscious dogs, rats, and monkeys before and after ganglionic blockade with hexamethonium. In seven intact, conscious dogs, ANF reduced mean arterial pressure by 7 +/- 1% and cardiac output by 19 +/- 3% and increased total peripheral resistance by 15 +/- 3%. After ganglionic blockade, ANF reduced mean arterial pressure by 7 +/- 2% but still increased total peripheral resistance by 15 +/- 3%. Similar results were observed in four dogs with total cardiac denervation and in six dogs with arterial baroreceptor denervation. Furthermore, in two dogs, combined ganglionic and alpha 1-adrenoceptor blockades failed to alter the rise in total peripheral resistance observed with ANF. In six intact, conscious rats, ANF reduced mean arterial pressure by 8 +/- 2% and cardiac output by 27 +/- 2% and increased total peripheral resistance by 27 +/- 5%. After ganglionic blockade, ANF still increased total peripheral resistance by 13 +/- 3%. In six intact, conscious monkeys, ANF reduced mean arterial pressure by 14 +/- 2% and cardiac output by 26 +/- 3% and increased total peripheral resistance by 17 +/- 3%. However, after ganglionic blockade. ANF decreased total peripheral resistance by 11 +/- 2%. These data provide evidence for a fundamental species difference in the vascular actions of ANF. In conscious dogs, ANF elicits "direct" vasoconstriction, which increases total peripheral resistance, even in the presence of denervation of reflexes or autonomic blockade. In conscious rats, ANF elicits both direct and reflexly mediated vasoconstriction. In conscious monkeys, although a component of direct vasoconstriction may also be present, the most prominent component appears to be reflexly mediated, since it was abolished by ganglionic blockade.

Adrenergic alpha-Antagonists↗
PubMed2003

The "dreamy state": John Hughlings-Jackson's ideas of epilepsy and consciousness.

OBJECTIVE: The authors review John Hughlings-Jackson's writings on the "dreamy state" and his subsequent derivation of degrees of consciousness. METHOD: They reviewed the publications of Hughlings-Jackson from his initial description of the "dreamy state" in 1876 until his writing about the "uncinate group of fits" in 1899. They then examined Hughlings-Jackson's use of the associated signs and symptoms of the "dreamy state" to formulate his ideas about human consciousness. RESULTS: Hughlings-Jackson defined the "dreamy state" as "over-consciousness," or a heightened intellectual state. He described associated symptoms of "crude sensations" of smell and taste, an unusual epigastric sensation, chewing and lip smacking, automatisms, postictal symptoms, and at least some degree of alteration of consciousness. Using his observations of the "dreamy state" as a model, Hughlings-Jackson proposed three degrees of consciousness, each with an object and subject component. CONCLUSIONS: Through his description of the "dreamy state," Hughlings-Jackson accurately characterized and localized medial temporal epilepsy. Correlating the ictal semiology of the "dreamy state" with consciousness, he developed a theory of consciousness that remains relevant to current understanding of the mind-brain relationship.

Brain↗
PubMed1983

Comparison of hepatic extraction of insulin and glucagon in conscious and anesthetized dogs.

Previous studies in anesthetized dogs demonstrated that basal hepatic extraction of insulin and glucagon are approximately 50 and 10-20%, respectively. Because of the stress of anesthesia and surgery, these values may not be relevant to normal physiology. In this study, hepatic extraction of insulin and glucagon were compared in conscious and anesthetized dogs. The conscious dogs had chronically implanted catheters in the portal and hepatic vein and the carotid artery and Doppler flow probes on the portal vein and hepatic artery. The mean basal portal vein insulin (42 +/- 10 and 44 +/- 7 microU/ml, respectively) and glucagon (247 +/- 37 and 219 +/- 20 pg/ml, respectively) concentrations were similar in conscious and anesthetized animals. The mean basal portal vein, but not hepatic artery, plasma flow was significantly increased in conscious dogs (462 +/- 62 vs. 294 +/- 35 ml/min, respectively). Despite the increased portal vein plasma flow in conscious animals, the basal hepatic extractions of insulin (42 +/- 6 vs. 39 +/- 6%, respectively) and glucagon (12 +/- 7 vs. 7 +/- 7%, respectively) were similar in both types of animals. Arginine and cholecystokinin-pancreozymin (CCK-PZ) infusion, which increased the amount of insulin and glucagon presented to the liver in conscious and anesthetized dogs, significantly decreased the hepatic extraction of insulin. Hepatic extraction of glucagon did not change in either group of animals. In contrast, infusion of insulin (1.0 mU/kg X min) and glucagon (4 ng/kg X min) into the portal system did not alter hepatic extraction of insulin even though the amounts of insulin and glucagon presented to that organ were similar to those obtained with arginine and CCK-PZ. The basal arterial glucose level was significantly lower in the conscious dogs but the basal hepatic glucose output was similar in the two groups. The glucose response to the infusion of arginine and CCK-PZ and exogenous hormones was significantly greater in the anesthetized animals.

Anesthesia, General↗
PubMed2006

Consciousness and the self-sensing brain: implications for feeling and meaning.

A number of authors have proposed or alluded to the significance for consciousness of sensing within the brain. This article reviews some of these proposals along with questions that have been raised and argues that consciousness might be understood as a property of a system that functions as a sense in the biological meaning of that term. The sense of consciousness is conceived not as a fixed structure but rather as a structure with variations, consistent with contemporary notions of complexity theory. A sense of consciousness has implications for concepts central to an understanding of consciousness, most notably the concepts of feeling and meaning. William James and others have proposed feeling as a ubiquitous aspect of consciousness. The concept of sensing, like that of feeling, provides a bridge between the organic and phenomenological aspects of consciousness, and the rudiments of meaning can be seen in the symbolizing role of a sense as it relates to adaptive problem solving.

Brain↗
PubMed1995

Skull fractures in children: altered conscious level is the main indication for urgent CT scanning.

It has been suggested that all children with skull fractures require urgent CT scanning to exclude intracranial injury. Adhering to such a policy could both tax limited scanning facilities and result in unnecessary exposure to radiation. The aim of this study is to assess the level of consciousness in determining the need for urgent CT scanning, and the possible role of the mechanism of injury as a secondary risk factor. We identified 140 children admitted during a 7-year period with a skull fracture after falling outside the home. Thirteen children had a diminished level of consciousness. Scans were performed in nine, and seven of the scans revealed significant intracranial injuries. By comparison, all 127 children with a normal level of consciousness recovered fully. Scanning was performed in only eight of them; seven scans were normal and one revealed a small subarachnoid heamorrhage which did not require active treatment. In addition, all 13 children with a diminished level of consciousness had sustained their injuries by falling from greater than their own standing height. By comparison, none of the children who had sustained their skull fractures by tripping up had a diminished level of consciousness or a significant intracranial injury. We conclude that all children with a diminished level of consciousness need to undergo an urgent CT scan. Children with skull fractures and a normal conscious level may be managed initially by neuroobservations and the clinician may be further reassured if the child's injury resulted from tripping up.

Child↗
PubMed1991

Altered states of consciousness therapy. A missing component in alcohol and drug rehabilitation treatment.

Attaining altered states of consciousness is described as a basic human motive. The substance dependent population is distinguished from other populations because they pursue these states destructively by inappropriate use of alcohol and drugs. Despite a body of literature supporting the benefits of altered states of consciousness, alcohol and drug rehabilitation treatment programs fail to address this motive because of social disapproval, means-end confusion, and inadequate staff training. The authors maintain that Alcoholics Anonymous directs its members toward an altered state of consciousness called a spiritual awakening, which replaces the self-destructive pursuit of substance induced "highs." Failure to address patients' need for alternative methods of achieving altered states of consciousness is presented as part of the reason for relapse. An Altered States of Consciousness Therapy (ASCT) program is described that can be used to teach patients to consciously manipulate affect and cognition to achieve a new consciousness.

Alcoholics Anonymous↗
PubMed2000

Consciousness: mapping the theoretical landscape.

What makes us conscious? Many theories that attempt to answer this question have appeared recently in the context of widespread interest about consciousness in the cognitive neurosciences. Most of these proposals are formulated in terms of the information processing conducted by the brain. In this overview, we survey and contrast these models. We first delineate several notions of consciousness, addressing what it is that the various models are attempting to explain. Next, we describe a conceptual landscape that addresses how the theories attempt to explain consciousness. We then situate each of several representative models in this landscape and indicate which aspect of consciousness they try to explain. We conclude that the search for the neural correlates of consciousness should be usefully complemented by a search for the computational correlates of consciousness.

Journal Article↗
PubMed1999

Stigma consciousness: the psychological legacy of social stereotypes.

Whereas past researchers have treated targets of stereotypes as though they have uniform reactions to their stereotyped status (e.g., J. Crocker & B. Major, 1989; C. M. Steele & J. Aronson, 1995), it is proposed here that targets differ in the extent to which they expect to be stereotyped by others (i.e., stigma consciousness). Six studies, 5 of which validate the stigma-consciousness questionnaire (SCQ), are presented. The results suggest that the SCQ is a reliable and valid instrument for detecting differences in stigma consciousness. In addition, scores on the SCQ predict perceptions of discrimination and the ability to generate convincing examples of such discrimination. The final study highlights a behavioral consequence of stigma consciousness: the tendency for people high in stigma consciousness to forgo opportunities to invalidate stereotypes about their group. The relation of stigma consciousness to past research on targets of stereotypes is considered as is the issue of how stigma consciousness may encourage continued stereotyping.

Adolescent↗
PubMed2003

The regulatory function of self-conscious emotion: insights from patients with orbitofrontal damage.

Although once considered disruptive, self-conscious emotions are now theorized to be fundamentally involved in the regulation of social behavior. The present study examined the social regulation function of self-conscious emotions by comparing healthy participants with a neuropsychological population--patients with orbitofrontal lesions--characterized by selective regulatory deficits. Orbitofrontal patients and healthy controls participated in a series of tasks designed to assess their social regulation and self-conscious emotions. Another task assessed the ability to infer others' emotional states, an appraisal process involved in self-conscious emotion. Consistent with the theory that self-conscious emotions are important for regulating social behavior, the findings show that deficient behavioral regulation is associated with inappropriate self-conscious emotions that reinforce maladaptive behavior. Additionally, deficient behavioral regulation is associated with impairments in interpreting the self-conscious emotions of others.

Affect↗
PubMed2003

Conscious and subliminal conflicts in normal subjects and patients with schizophrenia: the role of the anterior cingulate.

The human anterior cingulate cortex (ACC), which is active during conflict-monitoring tasks, is thought to participate with prefrontal cortices in a distributed network for conscious self-regulation. This hypothesis predicts that conflict-related ACC activation should occur only when the conflicting stimuli are consciously perceived. To dissociate conflict from consciousness, we measured the behavioral and brain imaging correlates of a motor conflict induced by task-irrelevant subliminal or conscious primes. The same task was studied in normal subjects and in patients with schizophrenia in whom the ACC and prefrontal cortex are thought to be dysfunctional. Conscious, but not subliminal, conflict affected anterior cingulate activity in normal subjects. Furthermore, patients with schizophrenia, who exhibited a hypoactivation of the ACC and other frontal, temporal, hippocampal, and striatal sites, showed impaired conscious priming but normal subliminal priming. Those findings suggest that subliminal conflicts are resolved without ACC contribution and that the ACC participates in a distributed conscious control network that is altered in schizophrenia.

Adolescent↗
PubMed2002

Volume kinetic analysis of the distribution of 0.9% saline in conscious versus isoflurane-anesthetized sheep.

BACKGROUND: The distribution and elimination of 0.9% saline given by intravenous infusion has not been compared between the conscious state and during inhalational anesthesia. METHODS: Six adult sheep received an intravenous infusion of 25 ml/kg of 0.9% saline over 20 min in the conscious state and also during isoflurane anesthesia and mechanical ventilation. The distribution and elimination of infused fluid were studied by volume kinetics based on serial analysis of hemoglobin dilution in arterial blood and by mass balance that incorporated volume calculations derived from volume kinetic analysis and measurements of urinary volumes. RESULTS: The mass balance calculations indicated only minor differences in the time course of plasma volume expansion between the conscious and anesthetized states. However, isoflurane anesthesia markedly reduced urinary volume (median, 9 vs. 863 ml; P < 0.03). In conscious sheep, the central and peripheral volume expansion predicted by volume kinetics agreed well with the calculations based on mass balance. However, during isoflurane anesthesia and mechanical ventilation, calculation using volume kinetic analysis of the variable kr, an elimination factor that, in conscious humans and sheep, is closely related to urinary excretion, represented both urinary excretion and peripheral accumulation of fluid. This suggests that the previous assumption that kr approximates urinary excretion of infused fluid requires modification, i.e., kr simply reflects net fluid movement out of plasma. CONCLUSIONS: In both conscious and anesthetized, mechanically ventilated sheep, infusion of 0.9% saline resulted in minimal expansion of plasma volume over a 3-h interval. In conscious sheep, infused 0.9% saline was rapidly eliminated from the plasma volume by urinary excretion; in contrast, the combination of isoflurane anesthesia and mechanical ventilation reduced urinary excretion and promoted peripheral accumulation of fluid.

Algorithms↗