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James M van Gelder

Publications and source records attributed to James M van Gelder.

7 recordsLinked to original sources
PubMed2006

Subdural haematomas complicating insertion of the low-pressure Novus hydrocephalus valve: a simple method for intra-operative testing of the anti-siphon device.

We previously reported 52 patients with hydrocephalus who were followed up after insertion of low-pressure Novus valves. These valves have a normally open anti-siphon device (ASD) incorporated. There were no cases of subdural haematomas (SDH). Subsequently, three new patients suffered SDH after insertion of these valves. We investigated a simple method for intra-operative testing of the ASD. These new patients had their valves replaced. In the laboratory, flow rates through five valves were recorded as a function of proximal positive pressure and distal negative pressures (siphoning). The flow rates were influenced by both proximal positive and distal negative pressures. The ASD stopped flow at distal negative pressures between -40 and -60 cm H(2)O. Proximal positive pressures increased this threshold. The flow can be measured by counting drops per minute. Three valves removed from patients were functioning as expected, one had unexpectedly slow flow at very high siphoning pressure and one had unexpectedly slow flow rates. In three patients with SDH complicating low-pressure Novus valves, the valves and anti-siphon devices were functioning adequately. Using a simple device, measuring flow rates in drops per minute was reliable and reproducible.

Cerebrospinal Fluid Shunts↗
PubMed2005

Association between compensation status and outcome after surgery: a meta-analysis.

CONTEXT: Compensation, whether through workers' compensation or through litigation, has been associated with poor outcome after surgery; however, this association has not been examined by meta-analysis. OBJECTIVE: To investigate the association between compensation status and outcome after surgery. DATA SOURCES: We searched MEDLINE (1966-2003), EMBASE (1980-2003), CINAHL, the Cochrane Controlled Trials Register, and reference lists of retrieved articles and textbooks, and we contacted experts in the field. STUDY SELECTION: The review included any trial of surgical intervention in which compensation status was reported and results were compared according to that status. No restrictions were placed on study design, language, or publication date. Studies were selected by 2 unblinded independent reviewers. DATA EXTRACTION: Two reviewers independently extracted data on study type, study quality, surgical procedure, outcome, country of origin, length and completeness of follow-up, and compensation type. DATA SYNTHESIS: Two hundred eleven studies satisfied the inclusion criteria. Of these, 175 stated that the presence of compensation (workers' compensation with or without litigation) was associated with a worse outcome, 35 found no difference or did not describe a difference, and 1 described a benefit associated with compensation. A meta-analysis of 129 studies with available data (n = 20,498 patients) revealed the summary odds ratio for an unsatisfactory outcome in compensated patients to be 3.79 (95% confidence interval, 3.28-4.37 by random-effects model). Grouping studies by country, procedure, length of follow-up, completeness of follow-up, study type, and type of compensation showed the association to be consistent for all subgroups. CONCLUSIONS: Compensation status is associated with poor outcome after surgery. This effect is significant, clinically important, and consistent. Because data were obtained from observational studies and were not homogeneous, the summary effect should be interpreted with caution. Compensation status should be considered a potential confounder in all studies of surgical intervention. Determination of the mechanism for this association requires further study.

Compensation and Redress↗
PubMed2004

Estimating the annual rate of de novo multiple aneurysms: three statistical approaches.

OBJECT: Individuals with unruptured intracranial aneurysms experience a higher rate of rupture if their history includes another aneurysm that has previously bled. The authors used systematic review and metaregression to estimate the annual rate of development of second de novo aneurysms after subarachnoid hemorrhage. METHODS: This investigation included studies in which more than 300 patients with intracranial aneurysms were described, and in which the age of the patients and the proportion with multiple aneurysms were documented. Studies describing delayed follow-up angiography that was performed after treatment of aneurysms were also reviewed. Twenty studies were included in a between-study analysis. The univariate odds ratio (OR) for multiple intracranial aneurysms per year of age was 1.085 (95% confidence interval [CI] 1.015-1.165); this value was calculated using a hierarchical model for between-study heterogeneity. Five studies were included that provided age stratification. The estimated OR for multiple intracranial aneurysms per year was 1.011 (95% CI 1.005-1.018). Four follow-up studies were available. CONCLUSIONS: According to the three different approaches (study-level, patient-level, and follow-up analyses), the estimated annual rates of development of de novo aneurysms were 1.62% (95% CI 0.28-3.59%), 0.28% (95% CI 0.12-0.49%), and 0.92% (95% CI 0.64-1.25%), respectively. The estimated annual rate of development of second de novo aneurysms ranged from 0.28 to 1.62%.

Cerebral Angiography↗
PubMed2004

A probabilistic and interactive decision-analysis system for unruptured intracranial aneurysms.

OBJECT: The goal in this study was to develop an interactive, probabilistic decision-analysis system for clinical use in the decision to treat or observe unruptured intracranial aneurysms. Further goals were to enable users of the system to adapt decision-analysis methods to individual patients and to provide a tool for interactive sensitivity analysis. METHODS: A computer program was designed to model the outcomes of treatment and observation of unruptured aneurysms. The user supplies probabilistic estimates of key parameters relating to a specific patient and nominates discount rate and quality of life adjustments. The program uses Monte Carlo discrete-event simulation methods to derive probability estimates of the outcomes of treatment and observation. Results are expressed as summary statistics and graphs. Discounted quality-adjusted life years are graphed using survival methods. Hierarchical simulations are used to enable investigators to perform probabilistic sensitivity analysis for one or multiple parameters simultaneously. The results of sensitivity analysis are expressed in graphs and as the expected value of perfect information. The system can be distributed and updated using the Internet. CONCLUSIONS: Further research is required into the benefits of clinical application of this system. Further research is also required into the optimum level of complexity of the model, into the user interface, and into how clinicians and patients are likely to interpret results. The system is easily adaptable to a range of medical decision analyses.

Confidence Intervals↗
PubMed2003

Computed tomographic angiography for detecting cerebral aneurysms: implications of aneurysm size distribution for the sensitivity, specificity, and likelihood ratios.

OBJECTIVE: This study examined the efficacy of computed tomographic angiography (CTA) for detection of ruptured and unruptured aneurysms after adjustment for their size distributions under various conditions of aneurysm prevalence. METHODS: A systematic review was used to estimate 1) the aneurysm size-specific sensitivity and specificity of CTA, and 2) the size distributions of ruptured and unruptured aneurysms. Probabilistic computer simulation was used to estimate the efficacy of CTA in the detection of aneurysms. RESULTS: The sensitivity of CTA ranged from 53% (95% confidence interval [CI], 44-62%) for 2-mm aneurysms to 95% (95% CI, 92-97%) for 7-mm aneurysms. The overall specificity was 98.9% (95% CI, 91.5-99.99%), but there was between-study heterogeneity. The estimated negative likelihood ratios for ruptured, unruptured, and at least 6-mm unruptured aneurysms were 0.081, 0.18, and 0.012, respectively. The positive likelihood ratio for CTA was sensitive to the pretest probability, the size of the positive finding, and the clinical context. With a small pretest probability, the positive likelihood ratio for unruptured aneurysms ranged from 15 for 2-mm aneurysms to 61 for 5-mm aneurysms. The positive likelihood ratio for ruptured aneurysms with an intermediate pretest probability (50%) ranged from 3.9 to 56 for 2- to 5-mm aneurysms. CONCLUSION: Small aneurysms detected on CTA should be investigated further unless there is a high pretest probability of a ruptured aneurysm. During screening for ruptured aneurysms, a negative CTA should be investigated further. During screening for unruptured aneurysms, a negative CTA results in a very low probability of a clinically important aneurysm.

Aneurysm, Ruptured↗
PubMed2002

The probability of sudden death from rupture of intracranial aneurysms: a meta-analysis.

OBJECTIVE: To estimate the proportion of patients with aneurysmal subarachnoid hemorrhage (SAH) who die before receiving medical attention. METHODS: We performed a systematic literature review. RESULTS: Eighteen population-based studies between 1965 and 2001 described the incidence of death from SAH before the patients received medical attention. The combined overall risk of sudden death was 12.4% (95% confidence interval, 11-14%). Patient level analysis was possible for two studies. No significant association between age and sudden death was identified. Aneurysms in the posterior circulation had an estimated probability of sudden death of 44.7% (95% confidence interval, 7.4-86%). Statistical sensitivity analysis was performed to examine some possible causes for the heterogeneity between the studies. Study factors statistically associated with a higher rate of sudden death include origin in England, computed tomographic scans not available for diagnosis, inclusion of patients with SAH from arteriovenous malformations, lower or not stated rate of autopsy for deaths in the community, and a higher rate of patients with confirmed aneurysms. CONCLUSION: The combined overall estimated risk of sudden death was 12.4% for aneurysmal SAH and 44.7% for posterior circulation aneurysms. However, there are several sources of heterogeneity or possible bias in the reported studies. Further information on patient and aneurysm characteristics is required.

Aneurysm, Ruptured↗