Exploration of the relationship between partial pressure of brain tissue oxygen and intracranial pressure.

Introduction: Partial pressure of brain tissue oxygen (PbtO2) has been shown to be a safe an effective monitoring modality to compliment intracranial pressure (ICP) monitoring. It is related to metabolic activity, disease severity and mortality. Research question: Understanding the complex relationship between PbtO2 and ICP for patients with traumatic brain injury will enable better clinical decision making beyond simple threshold treatment strategies. Material and methods: Patients with PbtO2 monitoring were identified from the BrainIT database, a multi-centre dataset, containing minute by minute PbtO2 and ICP readings. Missing data was imputed and a multi-level log-normal regression model with a compound symmetry correlation structure was built. This accounted for any increased correlation due to the repeated measurements. The model was adjusted for mean arterial pressure and the partial pressure of carbon dioxide. Non-linearity was assessed using analysis of deviance and trends using expected marginal means. Results: 11 subjects with over 82,000 readings were included. They had a median age of 38 (IQR: 37-47), 73% were male, a median length of stay of 11.8 (IQR: 6.6-19.7) days and a median extended Glasgow outcome scale of 7.00 (IQR: 5-8).There is a statistically significant (p < 0.001) non-linear effect of ICP on PbtO2. With an overall increase in PbtO2 of 5.2% (95% CI 4%-6.4%, p < 0.001) for a 10 mmHg increase in ICP below 22 mmHg and a decrease of 5.5% (95% CI 2.7%-8.3%, p=<0.001) in PbtO2 for a 10 mmHg increase in ICP above 22 mmHg. As well as a decrease of 40.9% (95% CI 2.3%-64.3%, p = 0.040) in PbtO2 per day in the intensive care unit. Discussion and conclusion: This model demonstrates that there is a significant non-linear relationship between ICP and PbtO2, however, this is a small heterogeneous cohort and further validation will be required.

Use of Direct Intracranial Pressure and Brain Tissue Oxygen Monitoring in Perioperative Management of Patients with Moyamoya Disease.

Intracranial pressure monitoring and brain tissue oxygen monitoring are commonly used in head injury for goal-directed therapies, but there may be more indications for its use. Moyamoya disease involves progressive stenosis of the arterial circulation and formation of collateral vessels that are at risk of hemorrhage. The risk of ischemic events during revascularization surgery and postoperatively is high. Impaired cerebral autoregulation may be one of the factors that are implicated. We present our experience with monitoring of cerebral oxygenation and autoregulation in the pathological hemisphere during the perioperative period in four patients with moyamoya disease.

Influence of Patient Demographics on Optimal Cerebral Perfusion Pressure Following Traumatic Brain Injury.

The relationship between optimal cerebral perfusion pressure (CPPopt) and patient characteristics has yet to be defined but could have significant implications for future guidelines recommending cerebral perfusion pressure (CPP) targets.Data from 36 traumatic brain injured patients admitted to neurological intensive care were analysed retrospectively. Linear mixed effects (LME) analysis was performed using an unadjusted-adjusted approach.Clinical characteristics with p < 0.10 were included in the adjusted model. A second adjusted model which included all variables of interest was created. Model fit was assessed using the root-mean-square error (RMSE).The adjusted model included time from initiation of intracranial pressure (ICP) monitoring (estimate = 0.00292, p < 0.001), age (estimate = -0.211, p = 0.0750) and the presence of diffuse axonal injury (DAI) (estimate = -35.5, p < 0.001). The RMSE of this model was 8.11 mmHg. The RMSE of the model containing all variables was 8.09 mmHg.Time, age and the presence of DAI may be important predictors of CPPopt. The models were too inaccurate at predicting CPPopt for employment in clinical practice but warrant further investigation. CPPopt is a dynamic measurement influenced by many factors, supporting the utility of investigating the feasibility of CPPopt-guided therapy.

Evaluation of Software for Automated Measurement of Adherence to ICP-Monitoring Threshold Guideline.

Challenges inherent in clinical guideline development include a long time lag between the key results and incorporation into best practice and the qualitative nature of adherence measurement, meaning it will have no directly measurable impact. To address these issues, a framework has been developed to automatically measure adherence by clinicians in neurological intensive care units to the Brain Trauma Foundation's intracranial pressure (ICP)-monitoring guidelines for severe traumatic brain injury (TBI).The framework processes physiological and treatment data taken from the bedside, standardises the data as a set of process models, then compares these models against similar process models constructed from published guidelines. A similarity metric (i.e. adherence measure) between the two models is calculated, composed of duration and scale of non-adherence.In a pilot clinical validation test, the framework was applied to physiological/treatment data from three TBI patients exhibiting ICP secondary insults at a local neuro-centre where clinical experts coded key clinical interventions/decisions about patient management.The framework identified non-adherence with respect to drug administration in one patient, with a spike in non-adherence due to an inappropriately high dosage; a second patient showed a high severity of guideline non-adherence; and a third patient showed non-adherence due to a low number of associated events and treatment annotations.

Time Series Analysis and Prediction of Intracranial Pressure Using Time-Varying Dynamic Linear Models.

Intracranial pressure (ICP) monitoring is a key clinical tool in the assessment and treatment of patients in a neuro-intensive care unit (neuro-ICU). As such, a deeper understanding of how an individual patient's ICP can be influenced by therapeutic interventions could improve clinical decision-making. A pilot application of a time-varying dynamic linear model was conducted using the BrainIT dataset, a multi-centre European dataset containing temporaneous treatment and vital-sign recordings. The study included 106 patients with a minimum of 27 h of ICP monitoring. The model was trained on the first 24 h of each patient's ICU stay, and then the next 2 h of ICP was forecast. The algorithm enabled switching between three interventional states: analgesia, osmotic therapy and paralysis, with the inclusion of arterial blood pressure, age and gender as exogenous regressors. The overall median absolute error was 2.98 (2.41-5.24) mmHg calculated using all 106 2-h forecasts. This is a novel technique which shows some promise for forecasting ICP with an adequate accuracy of approximately 3 mmHg. Further optimisation is required for the algorithm to become a usable clinical tool.

Telemetric Intracranial Pressure: A Snapshot Does not Give the Full Story.

Telemetric intracranial pressure (ICP) monitors are useful tools in the management of complex hydrocephalus and idiopathic intracranial hypertension (IIH). Clinicians may use them as a "snapshot" screening tool to assess shunt function or ICP. We compared "snapshot" telemetric ICP recordings with extended, in-patient periods of monitoring to determine whether this practice is safe and useful for clinical decision making.

Prior endoscopic third ventriculostomy does not increase ventriculoperitoneal shunt failure rate.

PURPOSE: To determine whether prior endoscopic third ventriculostomy (ETV) influences the failure rate of subsequently placed ventriculoperitoneal (VP) shunts. METHODS: Our institution's operative database and patient records were reviewed retrospectively to identify all paediatric patients who had undergone a first VP shunt or ETV at our institution between January 2012 and December 2015. Data was analysed using the Microsoft Excel, GraphPad Prism v7 and SPSS statistics. The literature on this topic to date was also reviewed. RESULTS: Eighty-six children were included in the study: 61 patients had a primary VP shunt inserted during the study period and 25 had a VP shunt inserted following failed ETV. There was no significant difference in the underlying aetiology or age of the patients in each group. In the primary VP shunt group, 47.5% (29 patients) required shunt removal at an average of 274 days post-insertion (range 7 days to 3.4 years). The 1-year revision rate was 34.4%. In the shunt post-ETV group, 48% (12 patients) required shunt removal at an average of 207 days post-insertion (range 2 days to 2.7 years). The 1-year revision rate was 36%. The most common reason for revision in both groups was blockage. CONCLUSIONS: We found no significant difference in failure rate or pattern between primarily inserted VP shunts and those inserted following an endoscopic third ventriculostomy. On the basis of this study and the small number of previously reported studies, we would advocate a trial of ETV where feasible to allow a chance at shunt independence.

Changing the consultant on calls from a daily to weekly rotation system reduces time to theater for patients with hip fracture to improve quality of care: a retrospective study of 2 cohorts of patients presenting with hip fracture.

OBJECTIVE: To determine whether changing the consultant on-call schedule resulted in a reduction in time to theater for patients presenting with a hip fracture. SUMMARY BACKGROUND DATA: Guidelines in the United Kingdom state that patients presenting with a neck of femur fracture should ideally be operated on the day of or the day after admission. However, there is a best practice tariff in the United Kingdom persuading trusts to operate on elderly patients with hip fracture within 36 hours of admission. Differing formats of daily trauma operating lists and varying consultant on-call schedules have the potential to affect a trusts ability to successfully meet such demands. METHODS: This study retrospectively analyzed whether changing the on-call schedule from a system where the on-call consultant is changed on a daily basis to one which changes weekly resulted in a reduction in time to theater for such patients and an increase in best practice tariffs paid. RESULTS: With the initial rotation system, the average time to theater for a fractured neck of femur was 44 hours 46 minutes, with 44.7% of patients having a time to surgery of less than 36 hours. Patients in the modified system underwent surgery with an average time to theater of 32 hours 19 minutes. In 71.7% of these patients, time to surgery was less than 36 hours. CONCLUSION: This study demonstrates that changing the schedule to permit a consultant to have a 7-day period of trauma on call at a time instead of only 1 day dramatically reduced the time to theater for patients with hip fracture. This significantly reduced the number of these cases done outside 36 hours and increased trust financial reward.