Clinical experience with a continuous monitor of intracranial compliance

1989 ◽  
Vol 71 (5) ◽  
pp. 673-680 ◽  
Author(s):  
Claudia S. Robertson ◽  
Raj K. Narayan ◽  
Charles F. Contant ◽  
Robert G. Grossman ◽  
Ziya L. Gokaslan ◽  
...  
Keyword(s):  
Mortality Rate ◽  
Clinical Signs ◽  
Weighted Average ◽  
Volume Index ◽  
Power Density Spectrum ◽  
Intracranial Volume ◽  
Density Spectrum ◽  
Content Type ◽  
Intracranial Compliance ◽  
The Mean

✓ Intracranial compliance, as estimated from a computerized frequency analysis of the intracranial pressure (ICP) waveform, was continuously monitored during the acute postinjury phase in 55 head-injured patients. In previous studies, the high-frequency centroid (HFC), which was defined as the power-weighted average frequency within the 4- to 15-Hz band of the ICP power density spectrum, was found to inversely correlate with the pressure-volume index (PVI). An HFC of 6.5 to 7.0 Hz was normal, while an increase in the HFC to 9.0 Hz coincided with a reduction in the PVI to 13 ml and indicated exhaustion of intracranial volume-buffering capacity. The mean HFC for individual patients in the present study ranged from 6.8 to 9.0 Hz, and the length of time that the HFC was greater than 9.0 Hz ranged from 0 to 104.8 hours. The mortality rate increased concomitantly with the mean HFC, from 7% when the mean HFC was less than 7.5 Hz to 46% when the mean HFC was 8.5 Hz or greater. The length of time that the HFC was 9.0 Hz or greater was also associated with an increased mortality rate, which ranged from 16% if the HFC was never above 9.0 Hz to 60% if the HFC was 9.0 Hz or greater for more than 12 hours. In 12 patients who developed uncontrollable intracranial hypertension or clinical signs of tentorial herniation during the monitoring period, 75% were observed to have had an increase in the HFC to 9.0 Hz or more 1 to 36 hours prior to the clinical decompensation. The more rapid the increase in the HFC, the more likely the deterioration was to be caused by an intracranial hematoma. Continuous monitoring of intracranial compliance by computerized analysis of the ICP waveform may provide an earlier warning of neurological decompensation than ICP per se and, unlike PVI, does not require volumetric manipulation of intracranial volume.

Intracranial volume-pressure relationship in man

1982 ◽  
Vol 56 (4) ◽  
pp. 524-528 ◽  
Author(s):  
Joseph Th. J. Tans ◽  
Dick C. J. Poortvliet
Keyword(s):  
Best Approximation ◽  
Continuous Monitoring ◽  
Fluid Pressure ◽  
Constant Term ◽  
Volume Index ◽  
Intracranial Volume ◽  
Content Type ◽  
The Best Approximation ◽  
Ventricular Fluid Pressure ◽  
Fine Print

✓ The pressure-volume index (PVI) was determined in 40 patients who underwent continuous monitoring of ventricular fluid pressure. The PVI value was calculated using different mathematical models. From the differences between these values, it is concluded that a monoexponential relationship with a constant term provides the best approximation of the PVI.

Subtle deterioration in shunted childhood hydrocephalus

1986 ◽  
Vol 65 (2) ◽  
pp. 211-216 ◽  
Author(s):  
Arno Fried ◽  
Kenneth Shapiro
Keyword(s):  
Buffering Capacity ◽  
Volume Index ◽  
Shunt Revision ◽  
Pressure Waves ◽  
Ventricular Size ◽  
Csf Shunts ◽  
Content Type ◽  
The Mean ◽  
Childhood Hydrocephalus ◽  
Fine Print

✓ Eighteen hydrocephalic children who presented with subtle deterioration when their shunts malfunctioned were studied during shunt revision by means of the pressure-volume index (PVI) technique. Bolus manipulation of cerebrospinal fluid (CSF) was used to determine the PVI and the resistance to the absorption of CSF (Ro). Ventricular size was moderately to severely enlarged in all the children. Steady-state intracranial pressure (ICP) at the time of shunt revision was 17.5 ± 7.3 mm Hg (range 8 to 35 mm Hg). Pressure waves could not be induced by bolus injections in the 8- to 35-mm Hg range of ICP tested. The mean ± standard deviation (SD) of the predicted normal PVI for this group was 18.5 ± 2.7 ml. The mean ± standard error of the mean of the measured PVI was 35.5 ± 2.1 ml, which represented a 187% ± 33% (± SD) increase in volume-buffering capacity (p < 0.001). The ICP did not fall after bolus injections in three children, so that the Ro could not be measured. In the remaining 15 patients, Ro increased linearly as a function of ICP (r = 0.74, p < 0.001). At ICP's below 20 mm Hg, Ro ranged from 2.0 to 5.0 mm Hg/ml/min, but increased to as high as 21 mm Hg/ml/min when ICP was above 20 mm Hg. This study documents that subtle deterioration in shunted hydrocephalic children is accompanied by abnormally compliant pressure-volume curves. These children develop ventricular enlargement and neurological deterioration without acute episodic pressure waves. The biomechanical profile of this group differs from other children with CSF shunts.

Biomechanical and hydrodynamic characterization of the hydrocephalic infant

1985 ◽  
Vol 63 (1) ◽  
pp. 69-75 ◽  
Author(s):  
Kenneth Shapiro ◽  
Arno Fried ◽  
Anthony Marmarou
Keyword(s):  
Steady State ◽  
Ventricular Volume ◽  
Volume Index ◽  
Injection Technique ◽  
Infantile Hydrocephalus ◽  
Content Type ◽  
Two Factors ◽  
The Mean ◽  
Fine Print

✓ The pressure-volume index (PVI) technique of bolus manipulation of cerebrospinal fluid (CSF) was used to measure neural axis volume-buffering capacity and resistance to the absorption of CSF in 16 hydrocephalic infants prior to shunting. The mean steady-state intracranial pressure (ICP) was 11.7 ± 5.7 mm Hg (± standard deviation (SD)), representing a modest elevation of ICP in infants. The mean measured PVI was 28.1 ± 1.5 ml (± standard error of the mean (SEM)) compared to the predicted normal level for these infants of 12.1 ± 2.7 ml (± SD) (p < 0.001). This resulted from an enhanced volume storage capacity in the hydrocephalic infants. The PVI was not related to ventricular size in these hydrocephalic infants. Although absorption of the additional bolus of fluid did not occur at steady-state ICP, it was readily absorbed once ICP was raised above a mean threshold pressure of 16.0 ± 5.0 mm Hg (± SD) in 13 of the 16 infants. Above this pressure, the mean CSF absorption resistance was 7.2 ± 1.3 mm Hg/ml/min (± SEM) which is twice the normal values as measured by the bolus injection technique. The biomechanical profile of infantile hydrocephalus described in this study indicates that two factors are required for progression of ventricular volume. While an absorptive defect may initiate the hydrocephalic process, progressive volume storage requires an alteration in the mechanical properties of the intracranial compartment.

Ventricular volume change in childhood

2002 ◽  
Vol 97 (3) ◽  
pp. 584-590 ◽  
Author(s):  
Chris Xenos ◽  
Spyros Sgouros ◽  
Kalyan Natarajan
Keyword(s):  
Statistical Difference ◽  
Linear Regression Analysis ◽  
Ventricular Volume ◽  
Intracranial Volume ◽  
Normal Children ◽  
Content Type ◽  
Ventricular Volumes ◽  
Significant Difference ◽  
The Mean ◽  
Fine Print

Object. The aim of this study was to construct a model of age-related changes in ventricular volume in a group of normal children ages 1 month to 15 years, which could be used for comparative studies of cerebrospinal fluid circulation disorders and cerebral atrophy developmental syndromes. Methods. A magnetic resonance imaging—based segmentation technique was used to measure ventricular volumes in normal children; each volume was then plotted against the child's age. In addition, intracranial volumes were measured and the ratio of ventricular to intracranial volume was calculated and plotted against age. The study group included 71 normal children, 39 boys and 32 girls, whose ages ranged from 1 month to 15.3 years (mean 84.9 months, median 79 months). The mean ventricular volume was 21.3 cm3 for the whole group, 22.7 cm3 in boys and 19.6 cm3 in girls (p = 0.062, according to t-tests). The mean ventricular volume at 12 months for the whole group was 17 cm3 (20 cm3 in boys and 15 cm3 in girls), representing 65% of the volume achieved by 15 years of age (87% in boys and 53% in girls). The volume increased by a factor of 1.53, to 26 cm3 (23 cm3 in males and 28 cm3 in females, increase factors of 1.15 and 1.86, respectively) at 15 years of age. The change in ventricular volume with age is not linear, but follows a segmental pattern. These age periods were defined as: 0 to 3, 4 to 6, 7 to 10, and 11 to 16 years. A statistical difference based on sex was only demonstrated in the first 6 years of life. The mean ventricular volume for the first 6-year period was 22.4 cm3 in boys and 15.7 cm3 in girls, and the difference was significant for the two sexes (linear regression analysis for age and sex, significant according to analysis of variance regression at 0.007, p = 0.108 for age, p = 0.012 for sex). Thereafter, there was no significant difference in ventricular volume between boys and girls with further growth. The ratio of ventricular volume to intracranial volume was 0.0175 for the whole group, 0.017 in boys and 0.018 in girls (p = 0.272, according to t-tests). At 12 months of age the ratio was 0.019; it stabilized to 0.015 at 8 years of age, and increased to 0.018 at 15 years of age. No statistical difference based on sex was demonstrated with growth. Conclusions. The ventricular volume in normal children increases with age by a factor of 1.5; the increase is in a nonlinear segmental pattern. Boys have significantly higher ventricular volumes only in the first 6 years of life. The ventricular/intracranial volume ratio remains stable throughout childhood.

scholarly journals The Limit of Photoreceptor Sensitivity

2005 ◽  
Vol 125 (6) ◽  
pp. 641-660 ◽  
Author(s):  
David Holcman ◽  
Juan I. Korenbrot
Keyword(s):  
Time Course ◽  
Single Photon ◽  
Detection Threshold ◽  
Light Sensitivity ◽  
Power Density Spectrum ◽  
Noise Power ◽  
High Concentration ◽  
Density Spectrum ◽  
Dark Noise ◽  
The Mean

Detection threshold in cone photoreceptors requires the simultaneous absorption of several photons because single photon photocurrent is small in amplitude and does not exceed intrinsic fluctuations in the outer segment dark current (dark noise). To understand the mechanisms that limit light sensitivity, we characterized the molecular origin of dark noise in intact, isolated bass single cones. Dark noise is caused by continuous fluctuations in the cytoplasmic concentrations of both cGMP and Ca2+ that arise from the activity in darkness of both guanylate cyclase (GC), the enzyme that synthesizes cGMP, and phosphodiesterase (PDE), the enzyme that hydrolyzes it. In cones loaded with high concentration Ca2+ buffering agents, we demonstrate that variation in cGMP levels arise from fluctuations in the mean PDE enzymatic activity. The rates of PDE activation and inactivation determine the quantitative characteristics of the dark noise power density spectrum. We developed a mathematical model based on the dynamics of PDE activity that accurately predicts this power spectrum. Analysis of the experimental data with the theoretical model allows us to determine the rates of PDE activation and deactivation in the intact photoreceptor. In fish cones, the mean lifetime of active PDE at room temperature is ∼55 ms. In nonmammalian rods, in contrast, active PDE lifetime is ∼555 ms. This remarkable difference helps explain why cones are noisier than rods and why cone photocurrents are smaller in peak amplitude and faster in time course than those in rods. Both these features make cones less light sensitive than rods.

Effects of positive end-expiratory pressure on intracranial pressure and compliance in brain-injured patients

1977 ◽  
Vol 47 (2) ◽  
pp. 195-200 ◽  
Author(s):  
Elizabeth A. M. Frost
Keyword(s):  
Intracranial Pressure ◽  
Brain Injuries ◽  
Head Injuries ◽  
Venous Pressure ◽  
Neurological Status ◽  
Volume Index ◽  
Positive End Expiratory Pressure ◽  
Content Type ◽  
Intracranial Compliance ◽  
Fine Print

✓ Hypoxic pulmonary disorders and head injuries associated with increased intracranial pressure (ICP) frequently co-exist. Positive end-expiratory pressure (PEEP) improves hypoxemia but has been reported to impede cerebral venous return, potentially causing a further increase in ICP. This study examined the effects of PEEP on ICP at different levels of brain compliance. Continuous ICP recordings were obtained after insertion of Scott cannulas to the lateral ventricles of seven comatose patients. Brain compliance was assessed by calculation of the pressure volume index. Patients were maintained in a 30° head-up position. Maintenance of PEEP to levels of 40 cm H2O pressure for as long as 18 hours did not increase ICP in patients with either normal or low intracranial compliance, and did not increase ICP in the absence of pulmonary disease. Central venous pressure and pulmonary artery wedge pressure increased proportionately as PEEP was increased. No consistent changes were found in blood pressure recordings, nor were there any reductions in cardiac output found during the studies. Abrupt discontinuation of PEEP did not result in increased ICP except for a transient rise on two occasions when respiratory secretions became copious and the patients were inadequately ventilated. Improved oxygenation in two patients as a result of PEEP was concomitant with improved intracranial compliance and neurological status. In patients with brain injuries, PEEP improves arterial oxygenation without increasing ICP as previously supposed. Consequently, PEEP is a valuable form of therapy for the comatose patient with pulmonary disorders such as pneumonia or pulmonary edema.

Epidemiological shift of hepatitis A in EAGLE countries – a projection

2019 ◽  
Vol 33 (1) ◽  
pp. 110-119
Author(s):  
Nidhi Ghildayal
Keyword(s):  
Mortality Rate ◽  
Hepatitis A ◽  
Economic Status ◽  
Emerging Market ◽  
Rapid Development ◽  
Weighted Average ◽  
Prototype Model ◽  
Developed Country ◽  
Content Type ◽  
Productivity Costs

Purpose Many world regions are developing quickly and experiencing increasing levels of sanitation, causing an epidemiological shift of hepatitis A in these areas. The shift occurs when children avoid being infected with the disease until a later age due to cleaner water sources, food, and hygiene practices in their environment; but if they are infected at later age, the disease is much more severe and lost productivity costs are higher. The purpose of this paper is to examine what could occur if an epidemiological shift of the disease continues in these regions, and what type of future burden hepatitis A may have in a hypothetical rapidly developing country. Design/methodology/approach Initially, annual hepatitis A mortality was regressed on the Human Development Index (HDI) for each country classified as an emerging and growth-leading economy (EAGLE) to provide an overview of how economic development and hepatitis A mortality related. Data from the various EAGLE countries were also fit to a model of hepatitis A mortality rates in relation to HDI, which were both weighted by each country’s 1995–2010 population of available data, in order to create a model for a hypothetical emerging market country. A second regression model was fit for the weighted average annual hepatitis A mortality rate of all EAGLE countries from the years 1995 to 2010. Additionally, hepatitis A mortality rate was regressed on year. Findings Regression results show a constant decline of mortality as HDI increased. For each increase of one in HDI value in this hypothetical country, mortality rate declined by 2.3016 deaths per 100,000 people. The hypothetical country showed the HDI value increasing by 0.0073 each year. Also, results displayed a decrease in hepatitis A mortality rate of 0.0168 per 100,000 people per year. Finally, the mortality rate for hepatitis A in this hypothetical country is projected to be down to 0.11299 deaths per 100,000 people by 2030 and its economic status will fall just below the HDI criteria for a developed country by 2025. Originality/value The hypothetical country as a prototype model was created from the results of regressed data from EAGLE countries. It is aimed to display an example of the health and economic changes occurring in these rapidly developing regions in order to help understand potential hepatitis A trends, while underscoring the importance of informed and regular policy updates in the coming years. The author believes this regression provides insight into the patterns of hepatitis A mortality and HDI as these EAGLE countries undergo rapid development.

Experimental feline hydrocephalus

1985 ◽  
Vol 63 (1) ◽  
pp. 82-87 ◽  
Author(s):  
Kenneth Shapiro ◽  
Futoshi Takei ◽  
Arno Fried ◽  
Ira Kohn
Keyword(s):  
Steady State ◽  
Volume Index ◽  
Control Group ◽  
Moderate Increase ◽  
Content Type ◽  
The Mean ◽  
Dural Opening ◽  
Container Model ◽  
Csf Absorption ◽  
Fine Print

✓ In a craniectomy-durectomy model of kaolin-induced feline hydrocephalus, the pressure-volume index (PVI) technique of bolus manipulations of cerebrospinal fluid (CSF) was used to study the biomechanical changes associated with hydrocephalus. Steady-state intracranial pressure (ICP), PVI, and the resistance to the absorption of CSF were determined acutely and 3 to 5 weeks later in hydrocephalic cats and time-matched control cats. Steady-state ICP was 11.0 ± 2.1 mm Hg (± standard deviation) in the hydrocephalic cats, compared to 10.8 ± 2.2 mm Hg in the chronic control group (p > 0.1). The ICP in both the chronic hydrocephalic and chronic control groups was significantly higher (p < 0.001) than after acute durectomy (mean ICP 8.5 ± 1.2 mm Hg). Immediately after dural opening, the mean PVI was 3.6 ± 0.2 ml (± standard error of the mean); over time, it decreased to 1.3 ± 0.1 ml in the chronic control group (p < 0.001), but remained elevated in the hydrocephalic group at 3.5 ± 0.4 ml (p < 0.001). Resistance to CSF absorption was 9.1 ± 1.4 mm Hg/ml/min immediately after dural opening and increased to 28.8 ± 4.5 mm Hg/ml/min (p < 0.001) in the hydrocephalic cats; it increased even further in the chronic measurements in control cats, to 82.3 ± 9.2 mm Hg/ml/min (p < 0.001). Ventricular size was moderate to severely enlarged in all hydrocephalic cats, and normal in the control group. These results indicate that the biomechanical profile of the altered brain container model of kaolin-induced feline hydrocephalus resembles that described in hydrocephalic infants. As shown in the control subjects, an absorptive defect alone is not sufficient to cause progressive ventricular enlargement. Increased volume-buffering capacity coupled with a moderate increase of CSF absorption resistance facilitates volume storage in the ventricles.

The natural history of symptomatic arteriovenous malformations of the brain: a 24-year follow-up assessment

1990 ◽  
Vol 73 (3) ◽  
pp. 387-391 ◽  
Author(s):  
Stephen L. Ondra ◽  
Henry Troupp ◽  
Eugene D. George ◽  
Karen Schwab
Keyword(s):  
Mortality Rate ◽  
Arteriovenous Malformations ◽  
Original Population ◽  
Major Morbidity ◽  
Content Type ◽  
History Of ◽  
The Mean ◽  
The Brain ◽  
Fine Print

✓ The authors have updated a series of 166 prospectively followed unoperated symptomatic patients with arteriovenous malformations (AVM's) of the brain. Follow-up data were obtained for 160 (96%) of the original population, with a mean follow-up period of 23.7 years. The rate of major rebleeding was 4.0% per year, and the mortality rate was 1.0% per year. At follow-up review, 23% of the series were dead from AVM hemorrhage. The combined rate of major morbidity and mortality was 2.7% per year. These annual rates remained essentially constant over the entire period of the study. There was no difference in the incidence of rebleeding or death regardless of presentation with or without evidence of hemorrhage. The mean interval between initial presentation and subsequent hemorrhage was 7.7 years.

Efficacy of lethal-trap devices to improve the welfare of trapped wild dogs

2019 ◽  
Vol 46 (1) ◽  
pp. 89 ◽  
Author(s):  
Paul D. Meek ◽  
Stuart C. Brown ◽  
Jason Wishart ◽  
Heath Milne ◽  
Paul Aylett ◽  
...  
Keyword(s):  
Mortality Rate ◽  
Animal Welfare ◽  
Canis Familiaris ◽  
Clinical Signs ◽  
Camera Trap ◽  
Main Trial ◽  
The Mean ◽  
Wild Dog ◽  
Wild Dogs ◽  
Mean Time

Context Wildlife and pest managers and stakeholders should constantly aim to improve animal-welfare outcomes when foot-hold trapping pest animals. To minimise stress and trauma to trapped animals, traps should be checked at least once every 24h, normally as soon after sunrise as possible. If distance, time, environmental or geographical constraints prevent this, toxins such as strychnine can be fitted to trap jaws to induce euthanasia. However, strychnine is considered to have undesirable animal-welfare outcomes because animals are conscious while clinical signs of intoxication are present. A toxin considered more humane, para-aminopropiophenone (PAPP), is available to induce euthanasia in trapped animals but is untested for presentation and efficacy. Aim We tested the efficacy of two types of lethal trap device (LTD’s), each using a paste formulation of PAPP as the active toxin to replace the use of strychnine on foot-hold jaw traps. Methods Elastomer LTDs and PAPP-cloths were fitted to jaw traps set to capture wild dogs (Canis familiaris). Camera-trap data was used to record animal behaviours after capture and to determine the efficacy of both modalities. Key results Every trapped wild dog (n=117) gnawed at the elastomer LTD’s or PAPP-cloth attached to the trap jaws that restrained them; one dog failed to liberate the toxin. From the dogs caught in the main trial (n=56), a mortality rate of 84% and 87% was reported respectively. The mean time from trap-to-death for elastomer LTDs was 64min and 68min for PAPP-cloths. Conclusions Elastomer LTDs and PAPP cloths combined caused the mortality of 85% of captured dogs. This efficacy could be improved by adopting the recommendations discussed in the present study for deploying PAPP-based LTDs during trap deployment. Implications PAPP-based LTDs offer an alternative option to the use of strychnine and improve the welfare outcomes for trapped predators, especially where traps are not checked within the recommended 24-h period.

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