Biomedical subjects

C Contant

Publications and source records attributed to C Contant.

At least 19 recordsLinked to original sources

PubMed2005

Continuous cerebral compliance monitoring in severe head injury: its relationship with intracranial pressure and cerebral perfusion pressure.

BACKGROUND: Cerebral compliance expresses the capability to buffer an intracranial volume increase while avoiding a rise in intracranial pressure (ICP). The autoregulatory response to Cerebral Perfusion Pressure (CPP) variation influences cerebral blood volume which is an important determinant of compliance. The direction of compliance change in relation to CPP variation is still under debate. The aim of the study was to investigate the relationship between CPP and compliance in traumatic brain injured (TBI) patients by a new method for continuous monitoring of intracranial compliance as used in neuro-intensive care (NICU). METHOD: Three European NICU's standardised collection of CPP, compliance and ICP data to a joint database. Data were analyzed using an unpaired student t-test and a multi-level statistical model. RESULTS: For each variable 108,263 minutes of data were recorded from 21 TBI patients (19 patients GCS</=8; 90% male; age 10-77 y). The average value for the following parameters were: ICP 15.1+/-8.9 mmHg, CPP 74.3+/-14 mmHg and compliance 0.68+/-0.3 ml/mmHg. ICP was >/=20 mmHg in 20% and CPP<60 mmHg for 10.7% of the time. Compliance was lower (0.51+/-0.34 ml/mmHg) at ICP>/=20 than at ICP<20 mmHg (0.73+/-0.37 ml/mmHg) (p<0.0001). Compliance was significantly lower at CPP<60 than at CPP>/=60 mmHg: 0.56+/-0.36 and 0.70+/-0.37 ml/mmHg respectively (p<0.0001). The CPP - compliance relationship was different when ICP was above 20 mmHg compared with below 20 mmHg. At ICP<20 mmHg compliance rose as CPP rose. At ICP>/=20 mmHg, the relation curve was convexly shaped. At low CPP, the compliance was between 0.20 and 0.30 ml/mmHg. As the CPP reach 80 mmHg average compliance was 0.55 ml/mmHg., but compliance fell to 0.40 ml/mmHg when CPP was 100 mmHg. CONCLUSIONS: Low CPP levels are confirmed to be detrimental for intracranial compliance. Moreover, when ICP was pathological, indicating unstable intracranial equilibrium, a high CPP level was also associated with a low volume-buffering capacity.

Adolescent↗

PubMed2005

Survey of traumatic brain injury management in European Brain-IT centres year 2001.

BACKGROUND: The aim of this study was to obtain basic knowledge about the current local conditions and neurointensive care of traumatic brain injury (TBI) in the new multi-centre collaborative BrainIT group. MATERIALS AND METHODS: The survey comprised a background part on local policies (Part A), and a case study section (Part B). The information was gathered by questionnaire followed by telephone interviews. Twenty-three BrainIT centres participated in the survey and answers from two respondents were available from 18 of the sites. RESULTS: The average proportion of agreement between duplicate respondents was 0.778 (range 0.415-1.00). All BrainIT centres monitored ICP. The treatment protocols seem to have a pattern concerning escalation of treatment of intracranial hypertension: 1/ evacuation of mass lesions and head elevation; 2/ increased sedation and mannitol; 3/ hyperventilation; 4/ ventricular drainage; 5/ craniectomy and barbituates. CONCLUSIONS: There seemed to be an agreement on neurointensive care policies within the BrainIT group. The suggested order of treatment was generally in accordance with published guidelines although the suggested order and combinations of different treatments varied. Variation of treatment within the range of prescribed standards provides optimal conditions for an interesting future analysis of treatment and monitoring data in reality using the BrainIT database.

Brain Injuries↗

PubMed2005

Assessment of different data representations and averaging methods on the Spiegelberg compliance device.

The Spiegelberg Compliance Device (Spiegelberg KG, Hamburg, Germany) has been available for the automated measurement and calculation of minute by minute intracranial compliance. Widespread practical use has been somewhat limited by the instability of values: especially at low intracranial pressures. We looked at two aspects of a methodology in an attempt to increase the value of the Spiegelberg device in the clinical setting. Firstly, we discussed the difference in representing measured values as elastance (dp/dv) instead of compliance (dv/dp); and secondly we proposed the use of an averaging algorithm called the Exponentially Weighted Moving Average (ewma), which could be applied as a flexible method to follow trends and rapid changes in the elastance (or compliance). Clinical data from sixteen patients were gathered and statistical analysis was focused on three particular aspects, the coefficient of variation which indicates the variability of data values, the correlation between the elastance (or compliance) time series and the underlying ICP signal and the percentage of outliers greater than 2.5 standard deviations from the mean. Our results showed that expressing elastance (dp/dv) instead of compliance (dv/dp) yielded fewer outliers and had a better correlation to ICP, and the ewma method had a better correlation to ICP than the Spiegelberg method.

Adult↗

PubMed2005

The BrainIT Group: concept and current status 2004.

Brain Injuries↗

PubMed2005

Accurate data collection for head injury monitoring studies: a data validation methodology.

BACKGROUND: BrainIT is a multi centre, European project, to collect high quality continuous data from severely head injured patients using a previously defined [6] core data set. This includes minute-by-minute physiological data and simultaneous treatment and management information. It is crucial that the data is correctly collected and validated. METHODS: Minute-by-minute physiological monitoring data is collected from the bedside monitors. Demographic and clinical information, intensive care management and secondary insult management data, are collected using a handheld computer. Data is transferred from the handheld device to a local computer where it is reviewed and anonymised before being sent electronically, with the physiological data, to the central database in Glasgow. Automated computer tools highlight missing or ambiguous data. A request is then sent to the contributing centre where the data is amended and returned to Glasgow. Of the required data elements 20% are randomly selected for validation against original documentation along with the actual number of specific episodic events during a known period. This will determine accuracy and the percentage of missing data for each record. CONCLUSION: Advances in patient care require an improved evidence base. For accurate, consistent and repeatable data collection, robust mechanisms are required which should enhance the reliability of clinical trials, assessment of management protocols and equipment evaluations.

Brain Injuries↗

PubMed2004

Bench test assessment of the new Raumedic Neurovent-P ICP sensor: a technical report by the BrainIT group.

BACKGROUND: In clinical practice, fiberberoptic and piezo-electric ICP probes are often used for measuring intracranial pressure (ICP). A number of similar technologies, although performing well in bench test studies, have been shown to exhibit unacceptable zero drift, fragility or both during trials conducted under clinical conditions. Recently, a new technology has become available, the Neurovent-P (Raumedic AG + CO, Raumedic, Germany). As a pre-requisite for a clinical trial, we have conducted and report on bench test studies to confirm the manufacturer's long term zero-drift performance for this technology. METHOD: In a test rig static tests (recording of 20 mmHg pressure) and dynamic tests, ranging from 5 to 50 mmHg have been performed. FINDINGS: 10 ICP probes have been tested for a total of 60 days. All the catheters, after the connection with the ICU monitor displayed a static pressure of 0 +/- 1 mmHg and did not required pre-insertion alteration. At five days, mean zero drift was 0.6 +/- 0.9 mmHg. Overall, zero drift ranged from 0 to 2 mmHg. At a fixed static pressure of 20 mmHg, the mean recorded value was 20.6 +/- 0.8 mmHg, ranging from 19 to 23 mmHg. A regression analysis of the relationship between the applied pressure and the recorded pressure during the dynamic tests of the 10 catheters yielded a correlation coefficient R2 of 0.997. Applying the Altman and Bland method to assess the bias and confidence limits for the Raumedic catheter responses during the dynamic tests against the applied gold-standard hydrostatic column pressures, the average bias of -0.66 +/- 0.85 mmHg, with 95% CLs of -2 mmHg and 1 mmHg. CONCLUSIONS: Mean zero drift, after five days, was very small and long-term continuous recording of a stable pressure was very precise. The response at dynamic tests, i.e. the changes of pressure in a wide range, was excellent. The average bias of the Raumedic catheter compared with the hydrostatic column is very small. After this bench test, the next and most critical step will be to conduct a trial of this promising technology under more demanding clinical environment.

Calibration↗

PubMed2004

R3-survey of traumatic brain injury management in European Brain IT centres year 2001.

OBJECTIVE: To obtain knowledge about the conditions and management of traumatic brain injury (TBI) in a collaborative network of Brain Information Technology centres. DESIGN: The Brain IT (Brain monitoring with Information Technology) survey comprised two parts: local conditions and policies (part A), and a case study part (part B). The information was gathered by written questionnaires followed by telephone interviews. PARTICIPANTS: Twenty-four Brain IT centres participated (two respondents from 18 sites). RESULTS: The average proportion of agreement between duplicate respondents was 0.79 (range 0.44-1.00). All Brain IT centres monitored ICP. The reported order of treatment for intracranial hypertension was: evacuation of mass-lesions and head elevation (1), increase of sedation and Mannitol scheme (2), hyperventilation (3), ventricular drainage (4), craniectomy and pentothal coma (5), and decompressive lobectomy (6). The respondents were less prone to evacuate expansive contusions in relation to extra cerebral hematomas. The most common suggested interventions (alone or in combination) for treatment of intracranial hypertension without mass lesions was the Mannitol scheme (included in 71% of the suggestions), CSF drainage (included in 56%), hyperventilation (included in 32%), and pentothal coma (included in 22%). CONCLUSIONS: The suggested management of TBI was mainly in accordance with published guidelines, although a minor proportion of the answers deviated to some extent. The suggested order and combinations of different treatment interventions varied. Variation of treatment within the range of prescribed standards provides optimal conditions for an interesting future analysis of treatment and monitoring data as collected prospectively in a Brain IT database.

Adult↗

PubMed2004

A model for studies of intracranial volume pressure dynamics in traumatic brain injury.

The present study was undertaken to establish an experimental trauma model where it was possible to alter intracranial pressure (ICP) dynamics without raising intracranial pressure to abnormal levels and monitor metabolic disturbances with microdialysis. Thirty rats were intubated and mechanically ventilated before and after trauma. ICP was measured in the left ventricle. A weight-drop technique (21 g from 35 cm) with a brain compression of 1.5 mm was used to produce the injury. Intracranial compensatory volume was decreased 20 or 60 microL by placement of rubber film between the dura mater and bone. A bolus injection technique was used for the pressure volume response. ICP remained within normal limits for 2 h after trauma irrespective of the reduction in compensatory intracranial volume. Pressure-volume index decreased from 0.0825 +/- 0.009 to 0.0779 +/- 0.011 mL in the sham trauma and from 0.0871 +/- 0.018 to 0.0748 +/- 0.017 mL in the trauma groups (p < 0.015) when the intracranial volume was reduced by 60 microL. Intracranial compliance was not affected significantly. The present study shows that it is possible to vary ICP dynamics in a traumatic brain injury model without causing pathological increases in baseline ICP. This model may be used to study the effects of secondary insults (i.e., hypotension, hypoxia, hypercarbia, and hyperthermia) on the injured brain when ICP is normal but intracranial compensatory volume is impaired.

Animals↗

PubMed2003

The BrainIT group: concept and core dataset definition.

INTRODUCTION: An open collaborative international network has been established which aims to improve inter-centre standards for collection of high-resolution, neurointensive care data on patients with traumatic brain injury. The group is also working towards the creation of an open access, detailed and validated database that will be useful for post-hoc hypothesis testing. In Part A, the underlying concept, the group coordination structure, membership guidelines and database access and publication criteria are described. Secondly, in part B, we describe a set of meetings funded by the EEC that allowed us to define a "Core Dataset" and we present the results of a feasibility exercise for collection of this core dataset. METHODS: Four group meetings funded by the EEC have enabled definition of a "Core Dataset" to be collected from all centres regardless of specific project aim. A paper based pilot collection of data was conducted to determine the feasibility for collection of the core dataset. Specially designed forms to collect the core dataset demographic and clinical information as well as sample the time-series data elements were distributed by both email and standard mail to 22 BrainIT centres. A deadline of two months was set to receive completed forms back from centres. A pilot data collection of minute by minute physiological monitoring data was also performed. FINDINGS: A core-dataset was defined and can be downloaded from the BrainIT web-site (go to "Core dataset" link at: www.brainit.org). Eighteen centres (82%) returned completed forms by the set deadline. Overall the feasibility for collection of the core data elements was high with only 10 of the 64 questions (16%) showing missing data. Of those 10 fields with missing data, the average number of centres not responding was 12% and the median 6%. An SQL database to hold the data has been designed and is being tested. Software tools for collection of the core dataset have been developed. Ethics approval has been granted for collection of multi-centre data as part of a pilot data collection study. INTERPRETATION: The BrainIT network provides a more standardised and higher resolution data collection mechanism for research groups, organisations and the device industry to conduct multi-centre trials of new health care technology in patients with traumatic brain injury.

Brain Injuries↗

PubMed2002

Multi-centre assessment of the Spiegelberg compliance monitor: interim results.

Analyses of a multi-centre database of 71 patients at risk of raised ICP showed that in head injured patients (n = 19) and tumour patients (n = 13) clear inverse relationships of ICP vs compliance exist. SAH patients (n = 5) appear to exhibit a biphasic relationship between ICP and compliance, however greater numbers of patients need to be recruited to this group. Patients with hydrocephalus (n = 34) show an initial decrease in compliance while ICP is less than 20 mmHg, thereafter compliance does not show a dependence upon ICP. A power analysis confirmed that sufficient numbers of patients have been recruited in the hydrocephalus group and a ROC analysis determined that a mean compliance value of 0.809 (lower and upper 95% CL = 0.725 & 0.894 resp.) was a critical threshold for raised ICP greater than 10 mmHg. Preliminary time-series analyses of the ICP and compliance data is revealing evidence that the cumulative time compliance is in a low compliance state (< 0.5 ml/mmHg), as a proportion of total monitoring time, increases more rapidly than the cumulative time ICP is greater than 25 mmHg. Before trials testing compliance thresholds can be designed, we need to consider not just the absolute threshold, but the duration of time spent below threshold. A survey may be required to identify a consensus of what is the minimum duration of raised ICP above 25 mmHg needed to instigate treatment.

Automation↗

PubMed2001

[Reproducibility and interchangeability of the Thromboelastograph, Sonoclot and Hemochron activated coagulation time in cardiac surgery].

PURPOSE: Despite their common use in cardiac surgery, few studies have evaluated the reproducibility of the Thromboelastograph (TEG), of the Sonoclot (SCT), and of the activated coagulation time with celite (ACT-C) or kaolin (ACT-K) measured with the Hemochron, in clinical conditions of on-site monitoring of hemostasis. This study determined the reproducibility of those measurements, and evaluated the ability of various devices to substitute for the ACT-C. METHODS: Blood samples collected from 20 volunteers and 21 patients undergoing myocardial revascularization were analyzed in the two channels of the TEG, in two SCT and four Hemochron analyzers. The overall of TEG and SCT coagulation profiles were analyzed by a computerized TEG and an experienced observer respectively. The variation rate (V%) was calculated for each variable. The ability of ACT-K and SCT to substitute for ACT-C under different clinical conditions was evaluated. RESULTS: ACT-C and ACT-K V% ranged between 5.6% and 10.8% and between 6.7% and 12.4% respectively. TEG and SCT V% ranged between 3.1% and 9.5% and between 5.8% and 33.6% respectively, according to different conditions and parameters. In volunteers and non-heparinized patients, the ACT-C and ACT-K were interchangeable. No other test can substitute for the ACT-C when patients are heparinized during cardiopulmonary bypass (CPB). CONCLUSIONS: In the clinical conditions of use, on-site hemostasis monitoring devices providing the most reproducible measurements are, in decreasing order, the TEG, the Hemochron and the SCT. In heparinized patients and during CPB, results from different tests are not interchangeable, stressing the importance of establishing appropriate instrument-specific values for monitoring anticoagulation during cardiac surgery.

Adult↗

PubMed2001

Validity and sensitivity to change of the extended Glasgow Outcome Scale in mild to moderate traumatic brain injury.

Using a structured outcome interview, this study addressed the validity and sensitivity to change of the Glasgow Outcome Scale (GOS) and the Extended GOS (GOSE) in a prospective study of patients who sustained mild (n = 30) to moderate (n = 13) traumatic brain injury (TBI) or general trauma (n = 44). The patients were recruited from the emergency center or inpatient units of Ben Taub General Hospital and invited to participate in follow-up examinations at 3 and 6 months. Using a series of functional outcome measures, assessment of affective status, and neuropsychological tests as criteria, the validity of the GOSE generally exceeded the GOS. Analysis of the outcome data for the patients who completed both the 3-month and 6-month assessments disclosed that the GOSE was more sensitive to change than the GOS. Comparison of the 3-month outcome data disclosed that the GOSE and GOS scores did not differ for the TBI and general trauma groups. These findings lend further support for utilization of the GOSE in clinical trials when it is based on a structured interview.

Adult↗

PubMed2000

Multi-centre assessment of the Spiegelberg compliance monitor: preliminary results.

Acute brain injury states (e.g. head injury, subarachnoid haemorrhage) show clear inverse relationships of ICP vs compliance, with ICP instability at times of lower compliance states. Variance in compliance values is large in hydrocephalus where ICP is relatively lower and compliance higher. Nonetheless, early experience shows that compliance data influence decisions on CSF diversion treatments. Future work will focus on the ability of intracranial compliance to predict ensuing ICP instability and methodological refinement for monitoring patients who have higher compliance states.

Brain↗

PubMed2000

Weight gain following unilateral pallidotomy in Parkinson's disease.

OBJECTIVE: To determine the clinical correlates and infer pathogenesis of weight gain following pallidotomy in patients with Parkinson's disease (PD). BACKGROUND: Surgical ablation of the globus pallidus internus (GPi) improves levodopa induced dyskinesias, moderately improves most other "cardinal" manifestations of PD, and has been noted to result in increased weight. METHODS: We incorporated Unified Parkinson's Disease Rating Scales (UPDRS) subscales, the Beck depression inventory and feeding questionnaire data into a linear regression model in order to determine which post-surgical change(s) may lead to weight gain over the first year following pallidotomy, n = 60. RESULTS: The mean weight gain 1 year after pallidotomy was 4.0 +/- 4.1 kg. Improvement in "off" motor scores (P < 0.005), especially gait subscores (P<0.0001), and to a lesser extent improvement in "on" motor scores (P<0.05) predicted weight gain. Changes in dyskinesia ratings, mood, food intake, dysphagia, levodopa dose, weight loss in the year prior to pallidotomy, age, and duration of PD did not correlate with subsequent weight gain. CONCLUSION: The high correlation between post-pallidotomy weight gain and "off" motor scores, suggests that this phenomenon is related to some change in underlying homeostasis associated with changes in the cardinal manifestations of PD itself, rather than secondary changes resultant from the surgery.

Dyskinesia, Drug-Induced↗

PubMed1998

Are there clinical and laboratory predictors of 5-year mortality in HIV-infected children and adolescents with hemophilia?

To determine factors associated with survival in a cohort of HIV-infected children and adolescents with hemophilia, an analysis of the 5-year mortality data for 207 HIV-infected young men was performed to examine the effect of selected clinical covariates on survival. The subjects were enrolled into the Hemophilia Growth and Development Study cohort from 1989 to 1990. Estimated mean time since infection at baseline was 6.7 years and mean estimated age at infection was 6.5 years. The baseline characteristics examined for their association with the hazard of death over the 5-year follow-up period were the following: absolute CD4+ cell count, hemoglobin status, skin test anergy, results of brain magnetic resonance imaging, non-hemophilia-related muscle atrophy (NHRMA), height for age, and impaired neuropsychological functioning as measured by the Vineland Adaptive Behavior and the Pediatric Behavior Scales. In all, 66 deaths occurred over the 5-year follow-up, 62 of whom met the 1987 (n = 56) or 1993 (n = 6) U.S. Centers for Disease Control and Prevention (CDC) definition of AIDS. Although each of the characteristics listed previously significantly increased the hazard of death by Cox proportional hazard regression models, only NHRMA remained a significant predictor of AIDS-related death when added to models that included each of the other cited baseline covariates.

Adolescent↗

PubMed1996

Combination suicide and cytokine gene therapy for hepatic metastases of colon carcinoma: sustained antitumor immunity prolongs animal survival.

The effectiveness of combination therapy using a suicide gene and cytokine genes for the treatment of metastatic colon carcinoma in the mouse liver was investigated. Pre-established hepatic tumors treated with a recombinant adenoviral vector containing the herpes simplex virus thymidine kinase gene(tk) exhibited substantial regression, although all treated animals suffered from subsequent relapses. Although cotreatment with a mouse interleukin 2 (mIL-2)-containing adenoviral vector induced an effective antitumor immune response, the immunity waned with time, and the treated animals eventually succumbed to hepatic tumor relapse or distant metastases. In this study, mouse granulocyte macrophage colony-stimulating factor (mGM-CSF) gene was tested for its ability to further enhance and prolong the antitumoral cellular immunity. A fraction of the animals treated with tk + mIL-2 + mGM-CSF developed long-term antitumor immunity and survived for more than 4 months without recurrence. This long-term antitumor immunity could be enhanced further by subsequent "vaccination" with mIL-2-expressing parental tumor cells. The results indicate that local expression of GM-CSF in the hepatic tumors and prolonged mIL-2 expression are necessary to generate persistent antitumor immunity that is essential for the prevention of tumor recurrence and long-term animal survival.

Animals↗

PubMed1996

Evaluation of a regional oxygen saturation catheter for monitoring SjvO2 in head injured patients.

OBJECTIVES: Monitoring jugular venous oxygen saturation (SjvO2) has been useful for the early identification and treatment of cerebral ischemia in patients with severe head injury. However, the catheters that have been used for this purpose have not performed optimally. The purpose of this study was to evaluate the performance of a new regional oxygen saturation catheter for monitoring SjvO2. METHODS: Eighteen regional oxygen saturation catheters, 4-Fr in diameter (Baxter Healthcare Corporation, Edward Critical Care), were used in this study. Each catheter was inserted percutaneously into the dominant jugular vein and the catheter's tip position in the jugular bulb was verified by radiograph. The catheter was calibrated in vitro prior to insertion using the optic calibrator provided by the manufacturer. The catheter was recalibrated every 8 to 12 hours by comparing the oxygen saturation value from the catheter with that measured by a co-oximeter in a blood sample drawn through the catheter. RESULTS: In vitro calibration using the optic calibrator was not always successful. Five catheters could not be calibrated. The remaining 13 catheters could all be calibrated, but only 9 provided a value that was within 4% of the oxygen saturation derived from the blood sample. After the first in vivo calibration, the correlation between the catheter and the blood sample values was improved. A total of 196 comparisons were made. The median, 25th, and 75th quartile differences between the catheter and the blood sample measurement of SjvO2 were 0.00, -1.15, and 1.25%, respectively. Using longitudinal data regression, the overall slope of the regression between the catheter and blood values was 0.997 (p = 0.001). CONCLUSIONS: The new regional oxygen saturation catheter provided reliable measurement of SjvO2 83% of the time when the signal quality index was < or = 3, and may be useful for continuous monitoring of SjvO2.

Blood Gas Analysis↗

PubMed1996

Ultrastructural characterization of the acetylcholine innervation in adult rat neostriatum.

The ultrastructural features of acetylcholine axon terminals (varicosities) in adult rat neostriatum were characterized by electron microscopy after immunostaining with a sensitive monoclonal antibody against rat choline acetyltransferase. Several hundred single sections from these varicosities were analysed for shape, size and content, presence of a synaptic membrane specialization, and composition of the microenvironment. An equivalent number of unlabeled varicosities selected at random from the same micrographs were similarly examined. The immunostained varicosity profiles were relatively small and seldom showed a junctional membrane specialization. Stereological extrapolation to the whole volume of these varicosities indicated that less than 10% were synaptic. Far fewer dendritic spines were juxtaposed to these predominantly asynaptic profiles than to their unlabeled counterparts. This difference seemed imputable to the low synaptic incidence of the acetylcholine varicosities and was consistent with the view that these are randomly distributed in relation to surrounding elements. The bulk of the data was suggestive of volume transmission. This raised the possibility that, in such a densely innervated area, a basal level of acetylcholine is permanently maintained around all cellular elements, contributing to the modulatory properties of this transmitter. This basal level of acetylcholine could also serve as a regulatory signal controlling the expression of different receptor subtypes in neurons, glia and blood vessels.

Acetylcholine↗