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Query: UMLS:C0268318 (ICP)
 10,007 document(s) hit in 31,850,051 MEDLINE articles (0.00 seconds)

Extended craniectomy has been employed in 148 +/- 4 month old infants with bilateral synostosis of lambdoid suture. Intraoperatively the ICP was less than 180 mm H2O in 6, 180-200 in 1, greater than 200 in 7. 18 +/- 10 months following surgery clinical signs as psychomotor retardation and so forth were present in 4 compared to 11 patients preoperatively. With 1 exception there was a distinct remodelling of neurocranium and an almost complete ossification of the operative site.
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PMID:The clinical significance of bilateral synostosis of the lambdoid suture and the usefulness of its treatment. 672 30

Increased intracranial pressure due to brain oedema was produced in albino rabbits by combining a cryogenic lesion in the left hemisphere with the intraperitoneal administration of 6-aminonicotinamide (cytotoxic agent). The most effective reduction in ICP (74%) was achieved when furosemide and mannitol were used in combination. When either mannitol or furosemide was employed alone, the average ICP reduction was approximately 53%. Peak ICP reduction occurred at 45 minutes with furosemide, 30 minutes with mannitol and furosemide combined, and at 60 minutes with a combination of mannitol and acetazolamide. Also studied simultaneously in these animals were investigated elastance (Em), brain water content, hemispheric water volume content, electrolytes, EEG, and gross pathology. Following therapy there was a statistically significance reduction of water content in the left hemisphere (cryogenic lesion) by all therapeutic modalities except with furosemide alone. In the right hemisphere the water content was reduced by furosemide and the furosemide-mannitol combination but not by the association of mannitol with acetazolamide. A significant decrease of brain sodium was noted only for the combination of mannitol and furosemide. This study indicates that effective reduction of cytotoxic-cryogenic brain oedema and intracranial hypertension can be obtained with a variety of diuretic agents. From the standpoint of tissue dehydration, restoration of tissue electrolyte balance, and rate of ICP reduction, the combination of furosemide-mannitol appears to offer advantages over furosemide alone, or acetazolamide-mannitol.
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PMID:Intracranial hypertension and brain oedema in albino rabbits. Part 2: Effects of acute therapy with diuretics. 679 66

Studies about ICP-variations of brain-injured patients under artificial ventilation seem to become important, since most of those patients, especially those with various additional injuries, do not breathe spontaneously. After having ventilated 10 patients with endexpiratory pressure from 0 to 10 cm H2O, significant ICP-rises could be monitored. A significant linear ICP-decrease could be induced by lifting the upper part of the body in corresponding linear rates. If applied in clinical work, the combination of these two methods we studied, seems to mean some sort of compensation of any ICP-changes during artificial ventilation. Therefore the indication for peep ventilation of brain-injured patients can be put less limited by ventilation-caused ICP-rises.
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PMID:[Intracranial pressure - variations in brain-injured patients caused by PEEP-ventilation and lifted position of the upper part of the body (author's transl)]. 744 42

Brain edema represents a disturbance of the volume equilibrium which, in the early stages of formation, must be compensated for by a reduction in other fluid and blood compartments. When this compensation is inadequate, tissue pressure and intracranial pressure increase, the magnitude of which depends on the compliance of the tissue. Tissue pressure gradients develop within the same hemisphere and between hemispheres, but these pressure gradients are transient and dissipate within a few hours after injury. The rate of dissipation is proportional to the product of hydraulic tissue resistance and compliance. These tissue pressure gradients are small in magnitude, less than 15 mm Hg; however, studies with an infusion model of edema in animals show that they are more than sufficient to propel fluid through the parenchyma by a process of bulk flow. The distention caused by the fluid increases the conductance and compliance of the tissue. This biomechanical response favors the dissipation of pressure gradients, and as a result hydrostatic gradients can be sustained only with a continued leakage of fluid from the site of injury. Without a continued extravasation of fluid, equilibration of the tissue pressure to the level of the ICP occurs rapidly. For this reason, the role of hydrostatic gradients in the resorption process may be limited. The development of an infusion model allows more rigid control and simulates the edematous process. Ultrastructural studies of the infusion model have shown that the tissue changes are similar to those reported for vasogenic edema, with the exception that in the infusion model the blood-brain barrier remains intact in the vicinity of the lesion and is not compromised by the mechanical distention of the ECS. The response of the cerebrovasculature to the infusion edema is in contrast to the usual reduction of flow seen after cryogenic injury. The CBF remains constant despite increased tissue water, as confirmed by gravimetric technique. The CO2 reactivity of the vessels in the area of edema is reduced, but the autoregulation to changes in perfusion pressure remains intact. When arterial pressure is raised beyond the limit of autoregulation, the pressure increase of CBF in the edematous area is less than the rise of CBF in normal tissue and suggests a "false autoregulation" caused by an increased tissue pressure. The differences in both the intracranial pressure and CBF response between these two models suggests that other factors must be operative. The cryogenic injury is indeed a traumatic injury to the brain and cannot be simply characterized by the increase in brain tissue water. In some animals a vasomotor paralysis disrupting the vascular compartmental volume and leading to a rapid rise in ICP with eventual reduction of CPP and CBF may explain these differences. Release of vasoactive substances into the ECS is an exciting hypothesis and is an area of investigation ideally suited to the infusion edema process where chemical composition of the fluid can be easily controlled.
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PMID:Biomechanics of brain edema and effects on local cerebral blood flow. 745 51

Severe head injury is frequently associated with extracranial injuries causing hemorrhagic hypotension. Volume replacement with isotonic fluids not only is therapeutically of limited efficacy but may aggravate posttraumatic brain edema. On the other side, hypertonic/hyperoncotic saline/dextran solution (HHS) shown to restore cardiovascular function in hemorrhagic shock instantaneously, was found to decrease intracranial pressure in experimental head injury. Currently the therapeutic efficacy of HHS and mannitol on ICP was compared at 24 hrs after a focal cerebral lesion and inflation of an epidural balloon in rabbits. Both solutions given at an equimolar dose rapidly lowered the ICP. After the first injection, ICP reduction was longer maintained with mannitol (189 +/- 27 min) as compared to HHS (98 +/- 14 min), while no difference in duration of lowering ICP was found after the second injection. Due to its blood pressure effects, HHS afforded a higher cerebral perfusion pressure than mannitol. In animals with HHS, the water content of the traumatized hemisphere was increased while the contralateral hemisphere was dehydrated. With mannitol, no differences in water content were found between the injured and uninjured hemisphere. The efficiency of HHS in hemorrhagic shock and intracranial hypertension render the fluid mixture particularly promising in patients with polytrauma in combination with head injury.
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PMID:7.2% NaCl/10% dextran 60 versus 20% mannitol for treatment of intracranial hypertension. 752 28

Development of a new method for the determination of Cr(III) and Cr(VI) is described. Anion-exchange high-performance liquid chromatography (HPLC) was used to separate Cr(III) and Cr(VI) with on-line detection by inductively coupled plasma atomic emission spectroscopy (ICP-AES) at 2766 A in preliminary studies, and inductively coupled plasma mass spectrometry (ICP-MS) with single-ion monitoring at m/z 52 and m/z 53 for final work. A mobile phase consisting of ammonium sulfate and ammonium hydroxide was used, and a simple chelation procedure with EDTA was followed to stabilize the Cr(III) species in standard solutions. ICP-MS results indicated the feasibility of using chromium isotope m/z 53 instead of the more abundant m/z 52 isotope due to a high mobile-phase background most significantly from the SO+ polyatomic interference. The absolute detection limits based on peak-height calculations were 40 pg for Cr(III) and 100 pg for Cr(VI) in aqueous media by HPLC-ICP-MS. The linear dynamic range extended from 5 ppb (ng/ml) to 1 ppm (micrograms/ml) for both species. By HPLC-ICP-AES, detection limits were 100 ng for Cr(III) and 200 ng for Cr(VI). Cr(III) was detected in NIST-SRM 1643c (National Institute of Standards and Technology-Standard Reference Material, Trace Elements in Water) by HPLC-ICP-MS at the 20 ppb level.
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PMID:Chromium speciation by anion-exchange high-performance liquid chromatography with both inductively coupled plasma atomic emission spectroscopic and inductively coupled plasma mass spectrometric detection. 758 51

Boron is present at low levels in groundwater and rainfall in the UK, ranging between 2 and 200 ng ml-1. A sensitive technique has been developed using inductively coupled plasma mass spectrometry (ICP-MS) to measure boron isotope ratios at low concentrations with a precision (Sr) of between 0.1 and 0.2%. Samples were evaporated to increase elemental boron concentrations to 200 ng ml-1 and interfering matrix elements were removed by an adapted cation-exchange separation procedure. The validity of measuring boron isotopic ratios by ICP-MS at this concentration level is discussed in relation the theoretical instrument precision attainable based on counting statistics. Using the developed procedure it is possible to use ICP-MS to establish a reliable database documenting the natural variation in boron isotope compositions in aquifers and rain water in the UK. Preliminary results demonstrate a trend in boron isotopic compositions with increasing boron concentration. The method may be used to evaluate possible levels of boron pollution from anthropogenic inputs into natural aqueous systems.
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PMID:Measurement of boron isotope ratios in groundwater studies. 759 15

Investigation into the use of osmotic therapy for ICP reduction began in 1919. Mannitol is the osmotic agent currently in use. Mannitol's effectiveness in reducing ICP has been shown. Osmotic therapy using mannitol reduces ICP by mechanisms that remain unclear. Mannitol is thought to decrease brain volume by decreasing overall water content, to reduce blood volume by vasoconstriction and to reduce CSF volume by decreasing water content. Mannitol may also improve cerebral perfusion by decreasing viscosity or altering red blood cell rheology. Lastly, mannitol may exert a protective effect against biochemical injury. The most common complications of therapy are fluid and electrolyte imbalances, cardiopulmonary edema and rebound cerebral edema. Nursing care of the patient receiving mannitol requires vigilant monitoring of electrolytes and overall fluid balance, and observation for the development of cardiopulmonary complications in addition to neurologic assessment.
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PMID:Mannitol revisited. 796 23

Intracarotid mannitol (HBBBD = hyperosmotic BBB disruption) as a method of transiently increasing solute/drug delivery to brain parenchyma has been associated in animals with a 1-2% increase in brain water and an increase in cisternal ICP. To determine whether these changes are clinically significant, we investigated ICP changes associated with HBBBD in 33 patients with malignant brain tumor utilizing flash VERs in which the N2 latency correlates well with ICP (N2 > 80 ms linearly corresponds to ICP > 20 cm H2O). VERs were obtained prior to, 4 and 24 h after 114 HBBBD/chemotherapy procedures. Additionally, in 10 patients (37 HBBBDs), VER monitoring was performed during the procedure. In 112/150 (75%) HBBBDs, good barrier opening was obtained (radionuclide brain scan). Postoperative mean N2 latencies did not differ significantly from pre-HBBBD values (N2 = 86 +/- 3.3 pre, 90 +/- 3.0/4 h, 87 +/- 3.6/24 h); there was no significant difference in N2 latencies in those patients with good vs poor BBBD. In the 10 patients monitored during HBBBD, peak N2 latency = 94.9 +/- 1.6, however, was significantly above pre- and post-HBBBD values (p < 0.04). We conclude that flash VERs are a useful noninvasive measure of ICP, and that HBBBD is associated with mild transient increase in ICP which is not clinically detrimental.
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PMID:Visual evoked responses as a monitor of intracranial pressure during hyperosmolar blood-brain barrier disruption. 797 25

Inductively coupled plasma mass spectrometry (ICP-MS) offers excellent detection limits and isotopic analysis of Ni in aqueous standards, but is prone to interferences--mainly from Ca-containing polyatomics--when biological matrices are analyzed for Ni. We have used multivariate calibration with principal components analysis (PCA) to correct for mass overlaps in serum digests. The resulting detection limit for Ni is below 1 microgram/l and the within-run imprecision is 6% at 1.46 micrograms Ni/l. In urine, the higher Ca content renders routine application of PCA problematic. We evaluated several methods of pre-concentration, and have developed a method of Ca oxalate precipitation that allows direct analysis of Ni in the diluted supernatant. The stable isotope 62Ni and the radiosotope 63Ni were co-administered i.v. to rats and the serum and urinary clearances were determined by liquid scintillation counting and ICP-MS. Ni measurements by both methods were in excellent agreement, and serum clearance fit a double exponential decay consistent with the two-compartment model of Onkelinx et al. [24]. A human volunteer ingested 61Ni (20 micrograms Ni/kg body wt.) in water after an overnight fast. Identical serum levels, peaking near 35 micrograms/l at 2 h, were measured by electrothermal atomic absorption spectrometry and ICP-MS with PCA. Urinary excretion of 61Ni measured by ICP-MS demonstrated absorption of 30% of the administered dose. We conclude that Ni isotopes can be measured in body fluids by ICP-MS at levels that allow stable isotope tracer studies in humans.
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PMID:Isotope-specific analysis of Ni by ICP-MS: applications of stable isotope tracers to biokinetic studies. 802


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