Michael D. Wood

Brain Tissue Oxygenation in Patients with Septic Shock: a Feasibility Study.

BACKGROUND Delirium is common in critically ill patients and its presence is associated with increased mortality and increased likelihood of poor cognitive function among survivors. However, the cause of delirium is unknown. The purpose of this study was to demonstrate the feasibility of using near-infrared spectroscopy (NIRS) to assess brain tissue oxygenation in patients with septic shock, who are at high risk of developing delirium. METHODS This prospective observational study was conducted in a 33-bed general medical surgical intensive care unit (ICU). Patients with severe sepsis or septic shock were eligible for recruitment. The FORESIGHT NIRS monitor was used to assess brain tissue oxygenation in the frontal lobes for the first 72 hours of ICU admission. Physiological data was also recorded. We used the Confusion Assessment Method-ICU to screen for delirium. RESULTS From March 1st 2014-September 30th 2014, 10 patients with septic shock were recruited. The NIRS monitor captured 81% of the available data. No adverse events were recorded. Brain tissue oxygenation demonstrated significant intra- and inter-individual variability in the way it correlated with physiological parameters, such as mean arterial pressure, heart rate, and peripheral oxygen saturation. Mean brain tissue oxygen levels were significantly lower in patients who were delirious for the majority of their ICU stay. CONCLUSION It is feasible to record brain tissue oxygenation with NIRS in patients with septic shock. This study provides the infrastructure necessary for a larger prospective observational study to further examine the relationship between brain tissue oxygenation, physiological parameters, and acute neurological dysfunction.

Low brain tissue oxygenation contributes to the development of delirium in critically ill patients: A prospective observational study

Purpose: To test the hypothesis that poor brain tissue oxygenation (BtO2) during the first 24 h of critical illness correlates with the proportion of time spent delirious. We also sought to define the physiological determinants of BtO2. Materials and methods: Adult patients admitted to the ICU within the previous 24 h were considered eligible for enrollment if they required mechanical ventilation, and/or vasopressor support. BtO2 was measured using near‐infrared spectroscopy, for 24 h after enrollment. Hourly vital signs and clinically ordered arterial and central venous blood gases were collected throughout BtO2 monitoring. Patients were screened daily for delirium with the confusion assessment method for the intensive care unit (CAM‐ICU). Results: BtO2 and the proportion of time spent delirious did not result in a significant correlation (p = 0.168). However, critically ill patients who spent the majority of their ICU stay delirious had significantly lower mean BtO2 compared to non‐delirious patients, (p = 0.017). BtO2 correlated positively with central venous pO2 (p = 0.00003) and hemoglobin concentration (p = 0.001). Logistic regression indicated that lower BtO2, higher narcotic doses and a history of alcohol abuse were independent risk factors for delirium. Conclusions: Poor cerebral oxygenation during the first 24 hours of critical illness contributes to the development of delirium. Trial registration: This trial is registered on clinicaltrials.gov (Identifier: NCT02344043), retrospectively registered January 8, 2015. HIGHLIGHTSLow BtO2 is an independent risk factor for the subsequent development of delirium.BtO2 and the proportion of time spent delirious were not significantly correlated.BtO2 was positively associated with central vpO2 and hemoglobin concentration.Other delirium risk factors: higher narcotic doses and a history of alcohol abuse

Using principal component analysis to reduce complex datasets produced by robotic technology in healthy participants

BackgroundThe KINARM robot produces a granular dataset of participant performance metrics associated with proprioceptive, motor, visuospatial, and executive function. This comprehensive battery includes several behavioral tasks that each generate 9 to 20 metrics of performance. Therefore, the entire battery of tasks generates well over 100 metrics per participant, which can make clinical interpretation challenging. Therefore, we sought to reduce these multivariate data by applying principal component analysis (PCA) to increase interpretability while minimizing information loss.MethodsHealthy right-hand dominant participants were assessed using a bilateral KINARM end-point robot. Subjects (Ns = 101–208) were assessed using 6 behavioral tasks and automated software generated 9 to 20 metrics related to the spatial and temporal aspects of subject performance. Data from these metrics were converted to Z-scores prior to PCA. The number of components was determined from scree plots and parallel analysis, with interpretability considered as a qualitative criterion. Rotation type (orthogonal vs oblique) was decided on a per task basis.ResultsThe KINARM performance data, per task, was substantially reduced (range 67–79%), while still accounting for a large amount of variance (range 70–82%). The number of KINARM parameters reduced to 3 components for 5 out of 6 tasks and to 5 components for the sixth task. Many components were comprised of KINARM parameters with high loadings and only some cross loadings were observed, which demonstrates a strong separation of components.ConclusionsComplex participant data produced by the KINARM robot can be reduced into a small number of interpretable components by using PCA. Future applications of PCA may offer potential insight into specific patterns of sensorimotor impairment among patient populations.

Robotic technology provides objective and quantifiable metrics of neurocognitive functioning in survivors of critical illness:A feasibility study

Purpose: To assess the feasibility of using an integrated multimodal data collection strategy to characterize the post‐intensive care syndrome (PICS). Materials and methods: Adult patients admitted to the ICU requiring invasive mechanical ventilation for >24 h and/or requiring vasopressor support were eligible for enrollment. We assessed cognitive and sensorimotor function at 3‐ and 12‐months after ICU discharge with the Repeatable Battery for the Assessment of Neuropsychological Status (RBANS) and with the KINARM robot. Results: At 3‐ and 12‐months after ICU discharge, 28/70 (40%) and 22/70 (31%) returned for follow‐up testing, respectively. Prominent reasons for declining testing at 3‐ and 12‐months included: not interested (40% and 38%) and health complications (31% and 31%). The majority of returning participants completed all tasks (96%–100%) and 100% of available data was recorded. On the RBANS, 54% (3 months) and 32% (12 months) of individuals were impaired in visuospatial/constructional skills. Similarly, the KINARM assessments demonstrated that 56% of individuals had visuospatial/executive dysfunction at 3 months, and 40% had impairment at 12 months. Individual scores indicated substantial variability. Conclusions: We demonstrated that it was feasible to quantify neurological dysfunction among participants that returned for follow‐up testing. However, future investigations will need to implement multiple retention strategies. Trial registration: This trial is registered on clinicaltrials.gov (Identifier: NCT02344043), retrospectively registered January 8, 2015.

Using robotic technology to quantify neurological deficits among survivors of critical illness: do they relate to brain tissue oxygen levels? a pilot study

Long-term cognitive dysfunction is common among survivors of critical illness. The etiology of this cognitive dysfunction is unknown, but it may relate to cerebral hypoxemia and hypoperfusion. Near infrared spectroscopy (NIRS) has been used to measure brain tissue oxygenation(BtO2) in patients during cardiac surgery and after cardiac arrest. Preliminary studies have suggested that BtO2 levels may correlate with neurological recovery. The KINARM robot provides quantitative metrics of sensory, motor, and cognitive function involving the upper limbs. It can quantify sensory processing of the limb, basic motor skills as well as a range of cognitive processes including executive function, working memory, and attention. There is a large normative database for the majority of tasks to which patient performance can be compared. It can detect subtle neurological deficits post ischemic stroke, which are not apparent on routine clinical testing. It is unknown if deficits can be identified in survivors of critical illness.