Gene/Protein Disease Symptom Drug Enzyme Compound
Pivot Concepts:   Target Concepts:
Query: UMLS:C0268318 (ICP)
 10,007 document(s) hit in 31,850,051 MEDLINE articles (0.00 seconds)

During the last decade several studies of cerebral blood flow (CBF) and metabolism in the acute phase of head injury have been published. It is the aim of this review to describe the dynamic changes in CBF, cerebral metabolic rate of oxygen (CMRO2), cerebral autoregulation (CA), and reactivity to PaCO2 and barbiturate (metabolic reactivity) in the acute phase after severe head injury and to discuss the therapeutical consequences with reference to prolonged artificial hyperventilation, hypothermia, barbiturate sedation, and mannitol therapy. On the basis of present knowledge concerning cerebral circulation and its regulation, the author reviews the literature concerning methodology for experimental and clinical CBF measurements and regulation of CBF and cerebral oxygen uptake. Emphasis is placed on studies of the effect of body temperature (hypothermia) as a therapeutic tool in the control of cerebral metabolism, blood flow, and intracranial pressure. Although hypothermia significantly reduces cerebral metabolism and blood flow, the effect of hypothermia on cerebral blood flow, metabolism, ICP, and outcome after acute head injury has never been investigated in clinically controlled studies. Experimental and clinical studies concerning sensitivity of CBF for changes in PaCO2 are reviewed. The normal CO2 reactivity defined as absolute (delta CBF/delta PaCO2) and relative (% change CBF/delta PaCO2) or delta in CBF/PaCO2 mm Hg are mentioned. In awake normocapnic man the relative CO2 reactivity averages 4%/mm Hg and the absolute CO2 reactivity 2ml/mm Hg. Uncontrolled prospective studies show a therapeutic effect of artificially prolonged hyperventilation on outcome. Only one preliminary controlled study indicates that the outcome is poorer and recovery prolonged. Nevertheless, in the acute phase of HI, artificial hyperventilation is used routinely for control of intracranial hypertension and during the intensive care management of the patients. The steal and inverse steal phenomena are reviewed. Although of considerable theoretical interest these phenomena are without clinical significance in patients with head injury, unless clinical CBF measurements are performed. The frequency of the inverse steal phenomenon in studies of rCBF with a 16-channel Cerebrograph (intraarterial approach) is found to be about 10%. During prolonged hyperventilation experimental studies and clinical studies of apoplexy show an adaptation of CBF and CSF-pH and bicarbonate.(ABSTRACT TRUNCATED AT 400 WORDS)
 ...
PMID:Cerebral blood flow in acute head injury. The regulation of cerebral blood flow and metabolism during the acute phase of head injury, and its significance for therapy. 227 29

We found that under conditions of sustained edema production, the rate of edema resolution by the CSF is not appreciably enhanced with lowering of the ICP. Although the entrance of edema fluid into CSF for the high-pressure series was notably slower, the amount of edema remaining in the brain was not appreciably affected. This appears somewhat contradictory to the principle that increasing the bulk flow pressure gradient should increase flow into the CSF. However, simultaneous steady-state measurements of the change in brain tissue pressure for a corresponding change in CSF pressure showed that the two pressures are identical. As a result, when ICP is lowered, the brain tissue pressure follows with no gradient increase. This also suggests that lowering of ICP and the concomitant reduction of tissue pressure may increase the intravascular tissue pressure gradient, which may act to increase the edema production. More work is required to resolve this issue.
 ...
PMID:Clearance of infusion edema fluid at high and low levels of intracranial pressure. 239 23

Of 148 patients with infratentorial brain tumours which were operated upon during a 5 year period, 59 patients had associated obstructive hydrocephalus, as evidenced by preoperative CT scan. External ventricular drainage was performed in these cases at time of surgery. CSF drainage was continued in the postoperative period for a mean of 2.3 (+/- 1.6) days. Only 6 of these 59 patients (10%) required a subsequent indwelling shunt. The infection rate was 10% and the total mortality was 8%. Perioperative ventricular drainage during and following the removal of posterior fossa tumours causing hydrocephalus provides an effective alternative to the preoperative placement of an indwelling shunt. Problems of shunt dysfunction, tumour seeding and upward herniation are thereby avoided. Postoperative ICP monitoring and drainage of blood and debris laden CSF is performed, increasing the safety of the postoperative period and possibly reducing the incidence of aseptic meningitis and postoperative shunt requirement.
 ...
PMID:Perioperative external ventricular drainage in obstructive hydrocephalus secondary to infratentorial brain tumours. 271 95

Two experiments were conducted to assess the feasibility of near infrared spectrophotometry (niroscopy) to monitor directly the effects of increased intracranial pressure on brain metabolism. ICP was increased in cats by subarachnoid infusion of a "mock" CSF solution. Cytochrome a,a3 redox state, oxyhemoglobin, deoxyhemoglobin and cerebral blood flow were noninvasively and continuously monitored by niroscopy. The results of both experiments indicated that changes in ICP correlated with a reduction in cytochrome a,a3 redox state (p less than 0.01), a decrease in the quantity of oxyhemoglobin and cerebral flow (p less than 0.01) and an increase in deoxyhemoglobin. The study results suggest that niroscopy has the potential for providing noninvasive and continuous data for assessing brain metabolic activity. The correlations obtained with simultaneous measurements of intracranial pressure make this an attractive method for application to those at risk for increased intracranial pressure.
 ...
PMID:A noninvasive method for monitoring the effects of increased intracranial pressure with near infrared spectrophotometry. 299 7

Intracranial pressure was increased in cats by infusing 'mock' CSF intracranially, thus decreasing cerebral perfusion and oxygenation. The cats then randomly received either 50% O2 or 50% O2-5% CO2 by inhalation. As monitored by in vivo near-infrared spectroscopy (NIR), no improvement was noted after 50% O2 whereas 50% O2-5% CO2 resulted in increased perfusion, an oxidation of cytochrome a,a3, an increase in oxyhemoglobin, and reduced quantities of de-oxyhemoglobin (p less than 0.01) despite a further increase in intracranial pressure. The authors conclude that: NIR is a useful means of noninvasively and directly assessing brain metabolism and has advantages over simple ICP monitoring; and continued investigations of CO2 as a possible therapeutic modality after head injury appear warranted.
 ...
PMID:Direct noninvasive assessment of brain metabolism during increased intracranial pressure: potential therapeutic vistas. 302 65

A dynamic head injury produced by an unconstrained head impact was induced in 30 dogs, out of a total of 45; 15 constituted the control group. Where the energy absorbed by the dog's head is of 59,95 Joules primary brain damage is produced. If the energy absorbed is of 340.31 Joules a severe brain swelling with increase in ICP takes place, leading to the animal's death within 48-96 hours. In the group of animals with a primary brain damage there was no significant change in I.C.P. However, the concentration of cAMP in CSF rose significantly, and this rise continued for 48 hours after impact. In the group of animals with severe secondary brain damage ICP rose significantly from the first post-injury control onwards. The concentration of cAMP in CSF increases significantly after the trauma, but reaches sub-normal levels 48 hours after impact. The plasma concentration of cAMP, on the other hand, is not significantly altered in any of the three groups. The modifications of cAMP in CSF could, in our opinion constitute a good guide for the assessment of the degree of brain damage.
 ...
PMID:Modifications of cAMP in plasma and CSF after experimental brain injury. 303 3

The 8 Italian centers participating in the International Cooperative Study on Timing of Aneurysm Surgery operated upon 68% of their patients eligible for the study. This low operative rate is mainly explained by the prevailing use of a delayed surgical policy. Only 28% of cases were operated on within 3 days of hemorrhage. Although early surgery was applied in more than 50% of patients from Centers 2, 6 and 7, most other centers operated on approximately 10% of patients within this time interval. Italian centers exhibited a wide variation in planned and actual surgery interval, with only 48% of their patients eventually operated on at the planned time. Differences from planned and actual timing of surgery were less consistent in the units performing early surgery. Preoperative conditions were different between the individual centers. The percent of patients alert at the time of surgery varied from approximately 50% in Centers 3 and 7 to 90% in Center 5. Centers 2 and 6 never operated on comatose patients and rarely stuporous patients. During surgery, induced hypotension was used in 67% of Italian patients. The brain was tight at exposure in 42% of patients from Italian centers; the difference from the other study centers was very significant (p = 0.0009). Consequently major brain resection was more frequently performed in Italy than in the other centers. Brain conditions depended mainly upon timing of surgery and preoperative grade (except for comatose patients) and varied accordingly between the individual centers. Temporary arterial occlusion was rarely used in Italian centers. Intraoperative bleeding from the aneurysm was slightly more frequent than in the other centers. The overall incidence of intraoperative complications was unremarkable. There were significant differences between the Italian and the other centers regarding the use of postoperative routines and medications. In Italian centers ventricular CSF drainage, shunt insertion, ICP monitoring, sedatives and analgesics were less frequently used; lumbar CSF drainage, anticonvulsants, steroids, and diuretics were applied more frequently. In the individual centers the major differences were in the use of antihypertensives, vasopressor agents, diuretics, hypervolemia, and low-molecular weight dextran.
 ...
PMID:Surgical findings and postoperative therapeutic modalities. 340 50

The effect of a supratentorial expanding mass lesion and of uniform increase of ICP on regional cerebral blood flow was examined in 31 cats. The blood flow was measured using the radioactive microsphere technique and continuous ICP increase was produced by inflating an extradural balloon or by infusion of mock CSF into subarachnoid lumbar space. Four additional animals in whom no ICP rise was produced were used as controls; several blood flow measurements were performed at different ICP levels and after sudden ICP release. The analysis of the data obtained revealed that intracranial hypertension caused inhomogenous pattern of blood flow change with compartmentalization of flow between supra- and infratentorial structures connected with cisternal herniation. The flow decrease may correspond to the craniocaudal pressure gradients in the brain stem. Irrespective of the method used to produce intracranial hypertension the blood flow in the lower brain stem was less susceptible to diminished perfusion pressure. Sparing of cerebral blood flow in the lower brain stem during progressive brain compression can be explained by compartmentalization. The ranking of regions at cerebral perfusion pressure below 60 mm Hg was similar for the lower brain stem regions independently of the method which was used to increase the ICP. This suggests that when CBF becomes reduced due to increase of ICP the perfusion favours the areas where neurons related to control of circulation are located. Diffuse increase of ICP produced no interhemispheric differences in the blood flow. These differences were detected when balloon compression was used. Asymmetry of perfusion in the brain stem structures was not observed. During continuously increasing ICP an increase of blood pressure taking place before pupillary dilatation occurred was not caused by medullary ischaemia. If the pressure continued to increase the vasopressor response occurring after pupillary dilatation took place did not improve the cerebral blood flow. Increase of cerebral perfusion followed a sudden release of ICP. In an experimental animal subjected to unilateral compressive lesion producing tentorial herniation, hyperperfusion involved especially the thalamus and the midbrain with relative flow decrease in the lower brain stem.
 ...
PMID:Blood flow in brain structures during increased ICP. 348 Nov 99

Pial arterial and venous calibre changes during intracranial hypertension were studied in 11 cats under barbiturate- and nitrous oxide-anaesthesia by using a closed cranial window technique and multichannel videoangiometry. Intracranial pressure was elevated from a normal mean level of 6.4 mm Hg by cisternal infusion of mock CSF in steps to 20, 30, 40, 50 mm Hg and finally to the level of systolic pressure. Pial arteries dilated significantly, small ones more than large ones, by 42 +/- 5.6% and 33 +/- 3%, respectively at ICP 50. With a further elevation of ICP up to systolic pressure, dilatation diminished to 28 +/- 10% in small, and to near resting calibres in large arteries. Pial veins remained unreactive on the average. Grouping into veins smaller and larger than 100 microns of resting size revealed, however, minor though statistically significant 5-10% dilatation of small, and a 5-10% diminution of large veins. Blood flow stopped, when cerebral perfusion pressure was zero, however, neither arteries nor veins collapsed. The present data support the hypothesis that CBF during acute elevation of CSF pressure depends on perfusion pressure rather than local vascular compression.
 ...
PMID:Cerebrovascular response to intracranial hypertension. 357 56

Nineteen pericerebral collections (18 subdural and 1 epidural) occurred in a series of 682 consecutive initial shunt insertions for hydrocephalus in children, performed between 1976 and 1984. No collections were observed in 358 reoperations performed in the same patients during the same period. The incidence rate of this complication is nearly four times higher after 2 years of age than in younger children (6.5% versus 1.7%). The rate is also higher, regardless of age, in noncommunicating than in communicating hydrocephalus. Pericerebral collections are observed with high- as well as low-closing pressure valves. Pericerebral collections after shunting were diagnosed in 80% of the cases less than 2 months after surgery. They were asymptomatic in nearly 60% of the cases but could become symptomatic later when they were not treated. At the onset at least, these pericerebral collections are compensated by the outflow of an equal quantity of intraventricular CSF so that ICP is only moderately elevated. Postshunt pericerebral collections may be the consequence of CSF loss at the time of surgery. In most cases, however, they are due to a CSF overdrainage by the valve. This overdrainage, together with the reversal of CSF flow in the highly resistant CSF pathways of hydrocephalus, establishes a pressure lower in the ventricles than in the subarachnoid space and tends to open up the subdural space. The treatment of postshunt subdural collections is the insertion of a simple tubing without valve between the subdural space and the peritoneum, the ventriculoperitoneal shunt being left in place. With this treatment, more than 80% of the collections disappeared or were improved.(ABSTRACT TRUNCATED AT 250 WORDS)
 ...
PMID:Pericerebral collections after shunting. 362 Dec 34


<< Previous 1 2 3 4 5 6 7 8 9 10 Next >>