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Gregory W. J. Hawryluk, Nicolas Phan, Adam R. Ferguson, Diane Morabito, Nikita Derugin, Campbell L. Stewart, M. Margaret Knudson, Geoffrey Manley and Guy Rosenthal

OBJECTIVE

The optimal site for placement of tissue oxygen probes following traumatic brain injury (TBI) remains unresolved. The authors used a previously described swine model of focal TBI and studied brain tissue oxygen tension (PbtO2) at the sites of contusion, proximal and distal to contusion, and in the contralateral hemisphere to determine the effect of probe location on PbtO2 and to assess the effects of physiological interventions on PbtO2 at these different sites.

METHODS

A controlled cortical impact device was used to generate a focal lesion in the right frontal lobe in 12 anesthetized swine. PbtO2 was measured using Licox brain tissue oxygen probes placed at the site of contusion, in pericontusional tissue (proximal probe), in the right parietal region (distal probe), and in the contralateral hemisphere. PbtO2 was measured during normoxia, hyperoxia, hypoventilation, and hyperventilation.

RESULTS

Physiological interventions led to expected changes, including a large increase in partial pressure of oxygen in arterial blood with hyperoxia, increased intracranial pressure (ICP) with hypoventilation, and decreased ICP with hyperventilation. Importantly, PbtO2 decreased substantially with proximity to the focal injury (contusion and proximal probes), and this difference was maintained at different levels of fraction of inspired oxygen and partial pressure of carbon dioxide in arterial blood. In the distal and contralateral probes, hypoventilation and hyperventilation were associated with expected increased and decreased PbtO2 values, respectively. However, in the contusion and proximal probes, these effects were diminished, consistent with loss of cerebrovascular CO2 reactivity at and near the injury site. Similarly, hyperoxia led to the expected rise in PbtO2 only in the distal and contralateral probes, with little or no effect in the proximal and contusion probes, respectively.

CONCLUSIONS

PbtO2 measurements are strongly influenced by the distance from the site of focal injury. Physiological alterations, including hyperoxia, hyperventilation, and hypoventilation substantially affect PbtO2 values distal to the site of injury but have little effect in and around the site of contusion. Clinical interpretations of brain tissue oxygen measurements should take into account the spatial relation of probe position to the site of injury. The decision of where to place a brain tissue oxygen probe in TBI patients should also take these factors into consideration.

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Ryan Hirschi, Gregory W. J. Hawryluk, Jessica L. Nielson, J. Russell Huie, Lara L. Zimmermann, Rajiv Saigal, Quan Ding, Adam R. Ferguson and Geoffrey Manley

OBJECTIVE

Brain tissue hypoxia is common after traumatic brain injury (TBI). Technology now exists that can detect brain hypoxia and guide corrective therapy. Current guidelines for the management of severe TBI recommend maintaining partial pressure of brain tissue oxygen (PbtO2) > 15–20 mm Hg; however, uncertainty persists as to the optimal treatment threshold. The object of this study was to better inform the relationship between PbtO2 values and outcome for patients with TBI.

METHODS

PbtO2 measurements were prospectively and automatically collected every minute from consecutive patients admitted to the San Francisco General Hospital neurological ICU during a 6-year period. Mean PbtO2 values in TBI patients as well as the proportion of PbtO2 values below each of 75 thresholds between 0 mm Hg and 75 mm Hg over various epochs up to 30 days from the time of admission were analyzed. Patient outcomes were determined using the Glasgow Outcome Scale. The authors explored putative treatment thresholds by generating 675 separate receiver operating characteristic curves and 675 generalized linear models to examine each 1–mm Hg threshold for various epochs.

RESULTS

A total of 1,380,841 PbtO2 values were recorded in 190 TBI patients. A high proportion of PbtO2 measures were below 20 mm Hg irrespective of the examined epoch. Time below treatment thresholds was more strongly associated with outcome than mean PbtO2. A treatment window was suggested: a threshold of 19 mm Hg most robustly distinguished patients by outcome, especially from days 3–5; however, benefit was suggested from maintaining values at least as high as 33 mm Hg.

CONCLUSIONS

This analysis of high-frequency physiological data substantially informs the relationship between PbtO2 values and outcome. The results suggest a therapeutic window for PbtO2 in TBI patients along with minimum and preferred PbtO2 treatment thresholds, which may be examined in future studies. Traditional treatment thresholds that have the strongest association with outcome may not be optimal.

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Jason F. Talbott, William D. Whetstone, William J. Readdy, Adam R. Ferguson, Jacqueline C. Bresnahan, Rajiv Saigal, Gregory W. J. Hawryluk, Michael S. Beattie, Marc C. Mabray, Jonathan Z. Pan, Geoffrey T. Manley and Sanjay S. Dhall

OBJECT

Previous studies that have evaluated the prognostic value of abnormal changes in signals on T2-weighted MRI scans of an injured spinal cord have focused on the longitudinal extent of this signal abnormality in the sagittal plane. Although the transverse extent of injury and the degree of spared spinal cord white matter have been shown to be important for predicting outcomes in preclinical animal models of spinal cord injury (SCI), surprisingly little is known about the prognostic value of altered T2 relaxivity in humans in the axial plane.

METHODS

The authors undertook a retrospective chart review of 60 patients who met the inclusion criteria of this study and presented to the authors’ Level I trauma center with an acute blunt traumatic cervical SCI. Within 48 hours of admission, all patients underwent MRI examination, which included axial and sagittal T2 images. Neurological symptoms, evaluated with the grades according to the American Spinal Injury Association (ASIA) Impairment Scale (AIS), at the time of admission and at hospital discharge were correlated with MRI findings. Five distinct patterns of intramedullary spinal cord T2 signal abnormality were defined in the axial plane at the injury epicenter. These patterns were assigned ordinal values ranging from 0 to 4, referred to as the Brain and Spinal Injury Center (BASIC) scores, which encompassed the spectrum of SCI severity.

RESULTS

The BASIC score strongly correlated with neurological symptoms at the time of both hospital admission and discharge. It also distinguished patients initially presenting with complete injury who improved by at least one AIS grade by the time of discharge from those whose injury did not improve. The authors’ proposed score was rapid to apply and showed excellent interrater reliability.

CONCLUSIONS

The authors describe a novel 5-point ordinal MRI score for classifying acute SCIs on the basis of axial T2-weighted imaging. The proposed BASIC score stratifies the SCIs according to the extent of transverse T2 signal abnormality during the acute phase of the injury. The new score improves on current MRI-based prognostic descriptions for SCI by reflecting functionally and anatomically significant patterns of intramedullary T2 signal abnormality in the axial plane.

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William J. Readdy, William D. Whetstone, Adam R. Ferguson, Jason F. Talbott, Tomoo Inoue, Rajiv Saigal, Jacqueline C. Bresnahan, Michael S. Beattie, Jonathan Z. Pan, Geoffrey T. Manley and Sanjay S. Dhall

OBJECT

The optimal mean arterial pressure (MAP) for spinal cord perfusion after trauma remains unclear. Although there are published data on MAP goals after spinal cord injury (SCI), the specific blood pressure management for acute traumatic central cord syndrome (ATCCS) and the implications of these interventions have yet to be elucidated. Additionally, the complications of specific vasopressors have not been fully explored in this injury condition.

METHODS

The present study is a retrospective cohort analysis of 34 patients with ATCCS who received any vasopressor to maintain blood pressure above predetermined MAP goals at a single Level 1 trauma center. The collected variables were American Spinal Injury Association (ASIA) grades at admission and discharge, administered vasopressor and associated complications, other interventions and complications, and timing of surgery. The relationship between the 2 most common vasopressors—dopamine and phenylephrine—and complications within the cohort as a whole were explored, and again after stratification by age.

RESULTS

The mean age of the ATCCS patients was 62 years. Dopamine was the most commonly used primary vasopressor (91% of patients), followed by phenylephrine (65%). Vasopressors were administered to maintain MAP goals fora mean of 101 hours. Neurological status improved by a median of 1 ASIA grade in all patients, regardless of the choice of vasopressor. Sixty-four percent of surgical patients underwent decompression within 24 hours. There was no observed relationship between the timing of surgical intervention and the complication rate. Cardiogenic complications associated with vasopressor usage were notable in 68% of patients who received dopamine and 46% of patients who received phenylephrine. These differences were not statistically significant (OR with dopamine 2.50 [95% CI 0.82–7.78], p = 0.105). However, in the subgroup of patients > 55 years, dopamine produced statistically significant increases in the complication rates when compared with phenylephrine (83% vs 50% for dopamine and phenylephrine, respectively; OR with dopamine 5.0 [95% CI 0.99–25.34], p = 0.044).

CONCLUSIONS

Vasopressor usage in ATCCS patients is associated with complication rates that are similar to the reported literature for SCI. Dopamine was associated with a higher risk of complications in patients > 55 years. Given the increased incidence of ATCCS in older populations, determination of MAP goals and vasopressor administration should be carefully considered in these patients. While a randomized control trial on this topic may not be practical, a multiinstitutional prospective study for SCI that includes ATCCS patients as a subpopulation would be useful for examining MAP goals in this population.

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Anthony M. DiGiorgio, Rachel Tsolinas, Mohanad Alazzeh, Jenny Haefeli, Jason F. Talbott, Adam R. Ferguson, Jacqueline C. Bresnahan, Michael S. Beattie, Geoffrey T. Manley, William D. Whetstone, Praveen V. Mummaneni and Sanjay S. Dhall

OBJECTIVE

Spinal cord injuries (SCIs) occur in approximately 17,000 people in the US each year. The average length of hospital stay is 11 days, and deep venous thrombosis (DVT) rates as high as 65% are reported in these patients. There is no consensus on the appropriate timing of chemical DVT prophylaxis for this critically injured patient cohort. The object of this study was to determine if low-molecular-weight heparin (LMWH) was safe and effective if given within 24 hours of SCI.

METHODS

The Transforming Research and Clinical Knowledge in SCIs study is a prospective observational study conducted by the UCSF Brain and Spinal Injury Center. Protocol at this center includes administration of LMWH within 24 hours of SCI. Data were retrospectively reviewed to determine DVT rate, pulmonary embolism (PE) rate, and hemorrhagic complications.

RESULTS

Forty-nine patients were enrolled in the study. There were 3 DVTs (6.1%), 2 PEs (4.1%), and no hemorrhagic complications. Regression modeling did not find an association between DVT and/or PE and age, American Spinal Injury Association grade, sex, race, or having undergone a neurosurgical procedure.

CONCLUSIONS

A standardized protocol in which LMWH is given to patients with SCI within 24 hours of injury is effective in keeping venous thromboembolism at the lower end of the reported range, and is safe, with a zero rate of adverse bleeding events.

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Darryl Lau, Cecilia L. Dalle Ore, Phiroz E. Tarapore, Michael Huang, Geoffrey Manley, Vineeta Singh, Praveen V. Mummaneni, Michael Beattie, Jacqueline Bresnahan, Adam R. Ferguson, Jason F. Talbott, William Whetstone and Sanjay S. Dhall

OBJECTIVE

The elderly are a growing subpopulation within traumatic spinal cord injury (SCI) patients. Studies have reported high morbidity and mortality rates in elderly patients who undergo surgery for SCI. In this study, the authors compare the perioperative outcomes of surgically managed elderly SCI patients with those of a younger cohort and those reported in the literature.

METHODS

Data on a consecutive series of adult traumatic SCI patients surgically managed at a single institution in the period from 2007 to 2017 were retrospectively reviewed. The cohort was divided into two groups based on age: younger than 70 years and 70 years or older. Assessed outcomes included complications, in-hospital mortality, intensive care unit (ICU) stay, hospital length of stay (LOS), disposition, and neurological status.

RESULTS

A total of 106 patients were included in the study: 83 young and 23 elderly. The two groups were similar in terms of imaging features (cord hemorrhage and fracture), operative technique, and American Spinal Injury Association Impairment Scale (AIS) grade. The elderly had a significantly higher proportion of cervical SCIs (95.7% vs 71.1%, p = 0.047). There were no significant differences between the young and the elderly in terms of the ICU stay (13.1 vs 13.3 days, respectively, p = 0.948) and hospital LOS (23.3 vs 21.7 days, p = 0.793). Elderly patients experienced significantly higher complication (73.9% vs 43.4%, p = 0.010) and mortality (13.0% vs 1.2%, p = 0.008) rates; in other words, the elderly patients had 1.7 times and 10.8 times the rate of complications and mortality, respectively, than the younger patients. No elderly patients were discharged home (0.0% vs 18.1%, p = 0.029). Discharge AIS grade and AIS grade change were similar between the groups.

CONCLUSIONS

Elderly patients had higher complication and mortality rates than those in younger patients and were less likely to be discharged home. However, it does seem that mortality rates have improved compared to those in prior historical reports.