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Query: UMLS:C0020440 (hypercapnia)
 7,939 document(s) hit in 31,850,051 MEDLINE articles (0.00 seconds)

CPP reflects perfusion problems related to increased ICP or inadequate MAP. CPP is a most helpful and practical management tool. The relationship of CBF and CPP depends on cerebral vascular resistance (flow equals pressure divided by resistance). At present, we do not have a practical method to measure vascular resistance or CBV. A close relationship between an increase in CBV and increase in ICP exists. However, the relationship between CBF and ICP is more complex. Whereas CBV is strongly dependent on vasodilation and venous return, CBF is influenced by CPP, vascular resistance, viscosity changes, and focally or diffusely increased ICP. For instance, in hypotensive shock one finds a low CBF with an elevated CBV (and ICP) from vasodilation related to hypercapnia, anoxia, or acidosis. Nevertheless, about two thirds of patients with increased ICP after head injury have increased CBF (hyperemia) and increased CBV. This frequent hyperemia is one rationale for the wide usage of hyperventilation to treat increased ICP. It must be recognized that a group of patients may have ischemia caused by excessive hyperventilation therapy for increased ICP. The PaCO2 must not be allowed to decrease to 20 mmHg or lower, but in some patients a PaCO2 level of 21 to 25 may be predisposing to ischemia. Strong consideration is thus given to monitoring CBF and cerebral oxygen metabolism (arteriovenous oxygen content difference [AVDO2], CMRO2) in states of coma and increased ICP. In such patients, continuous infusion of mannitol may result in improved CBF, and hyperventilation therapy can be less aggressive.(ABSTRACT TRUNCATED AT 250 WORDS)
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PMID:Nonsurgical management of increased intracranial pressure. 270 May 10

It is widely accepted that a tremendous increase in cerebral blood volume (CBV) due to progressive cerebral vasoparesis is an essential to the development of acute brain swelling. This study was designed to determine whether neurogenic and/or metabolic factors are predominant and how these interact with each other in producing cerebral vasoparesis. Fifty-one awake cats immobilized with pancuronium bromide were divided into 4 groups: group I, control; group II, normocapnic hypoxia (PaO2 = 50 mmHg); group III, normoxic hypercapnia (Pa-CO2 = 70 mmHg), and group IV, increased intracranial pressure (ICP = 40 mmHg) by brain compression. Systemic arterial pressure (BP), CBV (photoelectric method), and ICP (epidural pressure) were continuously recorded. The dorsomedial hypothalamic nucleus (DM) and the reticular formation of the midbrain (MB-RF) were bilaterally coagulated by a stereotaxic technique (3mA, 1 min). Therefore alterations in cerebrovascular tonus created by destruction of the cerebral vasomotor centers were examined in the animals with metabolically induced cerebral vasodilatation to various degree's. In group I, vasomotor center destruction resulted in an immediate and transient decrease in BP (DM; -14.1 +/- 6.7 mmHg, MB-RF; -10.2 +/- 4.8 mmHg) and simultaneous increase in CBV and ICP (DM; 7.6 +/- 7.0 mmHg, MB-RF; 6.0 +/- 5.6 mmHg) for 3 to 4 minutes. Increase in ICP by destruction of vasomotor centers reduced significantly in group II (DM; 2.3 +/- 2.6 mmHg, MB-RF; 1.6 +/- 1.2 mmHg) and reduced slightly in group IV (DM; 7.5 +/- 4.0 mmHg, MB-RF; 4.8 +/- 3.2 mmHg). In these 3 groups, autoregulation of cerebral blood flow and CO2 vasoreactivity were not changed by destruction of vasomotor centers.(ABSTRACT TRUNCATED AT 250 WORDS)
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PMID:[Interaction between neurogenic and metabolic factors upon deterioration in cerebrovascular tonus--experimental study on the etiology of cerebral vasoparesis]. 344 37

It is has been demonstrated that clinical outcome following head injury is correlated with the reactivity of the cerebrovasculature to carbon dioxide changes. Since CBF measurements are difficult to perform in these patients, a new technique is proposed utilizing the ICP response to capnic stimuli. In 40 head injured patients, the responses of ICP, pressure volume index (PVI) and middle cerebral artery velocities to hypocapnia and to hypercapnia were determined. Hypocapnia reduced ICP and MCA velocity while hypercapnia was followed by ICP and MCA velocity increases. Both changes were in the same magnitude supporting the concept the global ICP response reflects vascular reactivity. The fact that the velocity response to hypocapnia in lesioned hemispheres was less compared to the ICP response indicates the loss of ability to dilate in injured vessels and is consistent with earlier findings relating reduced reactivity to poor outcome.
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PMID:Measurement of vascular reactivity in head injured patients. 790 77

We investigated the effect of methylprednisolone on pathophysiological alterations in experimental pneumococcal meningitis. Untreated rats injected with pneumococcal cell wall components after hydrolization with M1 muramidase (PCW-M) developed an increase of regional cerebral blood flow (rCBF; 165.0 +/- 12.8%, baseline 100%, mean +/- S.E.M.), brain water content (79.23 +/- 0.10%), intracranial pressure (ICP; 11.9 +/- 1.0 mmHg) and white blood cell (WBC) count in the cerebrospinal fluid (CSF) (2,709 +/- 482 cells/microliters) within 8 h after intracisternal (i.c.) challenge. Pretreatment with methylprednisolone or administration of methylprednisolone 4 h after i.c. challenge significantly attenuated the increase of brain water content (78.88 +/- 0.08% and 78.82 +/- 0.05%, resp.), ICP (7.7 +/- 1.1 mmHg and 4.9 +/- 0.8 mmHg, resp.) and CSF WBC count (1,257 +/- 168 cells/microliters and 976 +/- 105 cells/microliters, resp.). However, methylprednisolone did not inhibit the increase of rCBF (163.5 +/- 13.7% and 160.9 +/- 6.8%, resp.), whereas dexamethasone significantly attenuated microvascular changes. Hypercapnia-induced reactivity of cerebral vessels tested 8 h after i.c. injection was preserved in all groups. In conclusion, we found that methylprednisolone significantly attenuated the increase of brain water content, ICP and CSF WBC count, but had no effect on microvascular changes during the early phase of experimental pneumococcal meningitis.
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PMID:Methylprednisolone attenuates inflammation, increase of brain water content and intracranial pressure, but does not influence cerebral blood flow changes in experimental pneumococcal meningitis. 803 46

Standardized volume-pressure craniospinal system loadings based on physiological loadings were developed in order to study the CSF outflow route efficiency and to evaluate the intracranial volume-pressure relations. The study was carried out on 10 cats. Standardized abdominal compression was applied in order to produce a central venous pressure increased and subsequently ICP increase to the level of 20 and 30 mmHg for 2 minutes. The abdominal compression test seems to be useful in the CSF outflow route evaluation. The orthostatic changes were studied in control animals and in cats with an epidural balloon. The animal body was evaluated to an angle of 50 degrees and 80 degrees with the head directed upwards and downwards. This test was found suitable for the intracranial volume reserve estimation. Similar application, especially in experimental conditions can be found in the hypercapnia test. PaCO2 concentration was increased by means of respiration with a gas mixture containing 5% CO2. A steady increase of ICP of 9 +/- 1 mmHg was obtained. Vascular dilatation resulted in an intracranial volume loading. The ICP response in subjects with normal CO2 response can be related to the intracranial volume reserve. The studies performed show the usefulness of the standardized volume-pressure loadings. The loadings applied are more physiological than lumbar infusion tests used so far.
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PMID:Evaluation of craniospinal system condition using standardized volume-pressure loadings. 874 65

In order to evaluate the relationship between brain oxygen supply and demand (O2 balance) in real time, it is necessary to use a multiparametric monitoring approach. Cerebral blood flow (CBF) is a representative parameter of O2 supply. The extracellular level of K+ is a reliable indicator of O2 demand since more than 60% of the energy consumed by the brain is utilized by active transport processes. Mitochondrial NADH redox state can represent the balance between O2 supply and demand. In order to monitor the brain of experimental animals or patients, we constructed the multiparametric assembly (MPA) and the following parameters were monitored simultaneously and in real time: CBF, CBV, NADH redox state, extracellular K+, DC potential, EEG, tissue temperature and ICP. Animals were exposed to hypoxia, ischemia, hypercapnia, hyperoxia and spreading depression (SD) and the relative changes in CBF and NADH were calculated and found to be significant indicators of brain energy state. Monitoring these two parameters increases the possibility of differentiating between various pathophysiological states. Each added parameter increases the power of diagnosis and determination of the functional state of the brain. Preliminary results obtained in patients monitored in the ICU or in the OR show that the responses to hypercapnia, spreading depression or ischemia are similar to those measured in experimental animals.
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PMID:Multiparametric monitoring of brain oxygen balance under experimental and clinical conditions. 958 30

The brain of neurosurgical patients are exposed to various manipulations in the ICU or during surgery. Under such conditions brain O2 balance may become negative and as a result brain vitality and function will deteriorate. In order to evaluate brain vitality in real time it is important to measure more than one parameter. The multiparametric monitoring system used in our previous study to monitor comatose patients (Mayevsky et al., Brain Res. 740: 268-274, 1996) was changed into a "simplified" tissue spectroscope for real time monitoring of brain O2 balance. Mitochondrial function was evaluated by monitoring the NADH redox state by surface fluorometry. Microcirculatory blood flow was assessed by laser Doppler flowmetry. The combined optical probe was located on the surface of the brain during various neurosurgical procedures and the responses were recorded and presented in real time to the surgeon. A total of 32 patients were monitored during various procedures. The results could be summarized as follows: 1. Hypercapnia led to 3 different types of responses. In two patients the 'stealing' like event was recorded. In the other 7 patients the responses to high CO2 was not detectable. In the last group of 6 patients a clear CBF elevation was recorded with variable response of mitochondrial NADH. 2. Our monitoring device was able to evaluate the efficacy of the STA-MCA anastomosis during aneurysm surgery. 3. A significant correlation was recorded between CBF and NADH redox state during changes in blood pressure, papaverine injection, spontaneous drop in blood supply to the brain or during releasing of high ICP levels. We conclude that in order to evaluate the metabolic state of the brain during neurosurgical procedures it is necessary to monitor both CBF and mitochondrial NADH by using the tissue spectroscope.
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PMID:The evaluation of brain CBF and mitochondrial function by a fiber optic tissue spectroscope in neurosurgical patients. 1216 49

Secondary brain injury is a complicated, multifactorial process that results from hypoxemia, hypercapnia or hypocapnia, and increased ICP. Implementation of a traumatic brain injury protocol for patients with head injury including hemodynamic management, pulmonary care, maintenance of body temperature, control of the environment, positioning of patients, and seizure prophylaxis provides critical care nurses a proactive means to prevent or minimize the development of secondary brain injury in the emergency department.
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PMID:Nursing role on preventing secondary brain injury. 1758 40

The management of critically ill children with traumatic brain injury (TBI) requires a precise assessment of the brain lesions but also of potentially associated extra-cranial injuries. Children with severe TBI should be treated in a pediatric trauma center, if possible. Initial assessment relies mainly upon clinical examination, trans-cranial Doppler ultrasonography and body CT scan. Neurosurgical operations are rarely necessary in these patients, except in the case of a compressive subdural or epidural hematoma. On the other hand, one of the major goals of resuscitation in these children is aimed at protecting against secondary brain insults (SBI). SBI are mainly because of systemic hypotension, hypoxia, hypercarbia, anemia and hyperglycemia. Cerebral perfusion pressure (CPP = mean arterial blood pressure - intracranial pressure: ICP) should be monitored and optimized as soon as possible, taking into account age-related differences in optimal CPP goals. Different general maneuvers must be applied in these patients early during their treatment (control of fever, avoidance of jugular venous outflow obstruction, maintenance of adequate arterial oxygenation, normocarbia, sedation-analgesia and normovolemia). In the case of increased ICP and/or decreased CPP, first-tier ICP-specific treatments may be implemented, including cerebrospinal fluid drainage, if possible, osmotic therapy and moderate hyperventilation. In the case of refractory intracranial hypertension, second-tier therapy (profound hyperventilation with P(a)CO(2) < 35 mmHg, high-dose barbiturates, moderate hypothermia, decompressive craniectomy) may be introduced, after a new cerebral CT scan.
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PMID:Management of critically ill children with traumatic brain injury. 1831 8