Monitoring Spinal Cord Tissue Oxygen in Patients With Acute, Severe Traumatic Spinal Cord Injuries

Spinal cord blood flow elevation with systemic vasopressor noradrenaline is partly mediated by vasodilation of spinal arteries due to reduced expression of alpha adrenoreceptors

BACKGROUND CONTEXT

Elevation of mean arterial blood pressure (MAP) has been proposed to raise spinal cord blood flow (SCBF) after traumatic spinal cord injury (TSCI). Current clinical guidelines for cervical TSCI suggest maintaining MAP 85-90 mmHg for 5-7 days using vasopressors, eg, noradrenaline. However, it remains unknown whether these interventions that promote an increased systemic MAP result in improved perfusion in the spinal cord. The local effect of vasopressors on the spinal cord arteries also remains unknown.

PURPOSE

The aim of this study was to investigate whether the increased systemic MAP results in increased SCBF, and secondly, to examine the mechanism behind noradrenaline (NA) action in spinal cord arteries.

STUDY DESIGN

An experimental animal study.

METHODS

The study included nine 38-42 kg landrace pigs. In six pigs, MAP was gradually elevated using NA and continuous SCBF was recorded by laser doppler flowmetry. Spinal cord samples from these 6 pigs were excised for isolation of spinal cord arteries that were used for ex-vivo vascular function assessment in isometric myograph. Segments of mesentery from another 3 pigs were used to dissect mesenteric small arteries that were also studied in myograph, as control peripheral arteries. Other spinal cord and mesenteric arterial segments from the same biopsies were dissected and snap-frozen for the following expression analysis. Adrenoceptor's expression in arteries of all included animals was assessed with quantitative PCR.

RESULTS

The controlled mixed model found that SCBF was lower at MAP below 50 mmHg and that SCBF increased significantly in the MAP range of 50-100 mmHg (p=.02). Further increase of MAP did not significantly affect SCBF (at MAP range of 100-150 mmHg, p=.15; at 150-200 mmHg, p=.51). However, SCBF significantly increased over the study time-course (at 80 min, p=.002; at 100 min, p<.001), which was dependent on the experimental duration being a confounder of increased exposure to large doses of NA. Isolated spinal arteries did not contract to NA ex-vivo and even showed a tendency for vasorelaxation. This relaxation was abolished by β-adrenoceptor inhibitor, propranolol. In contrast, mesenteric arteries were contracted by NA and propranolol potentiated this contraction. Mesenteric arteries showed a higher expression of α1A adrenoceptors than spinal arteries, while no significant difference was found in other adrenoceptor isoforms.

CONCLUSIONS

We found SCBF reduced at MAP below 50 mmHg and that the SCBF increased significantly in MAP range between 50 and 100 mmHg. Elevating MAP above 100 mmHg was not associated with a further increase in SCBF. We also showed that NA increases SCBF in-vivo and relaxes spinal arteries ex-vivo. This effect was associated with a low arterial expression of α adrenoceptors over β adrenoceptors in the spinal cord.

CLINICAL SIGNIFICANCE

These findings challenge the assumption that SCBF is solely dictated by MAP within autoregulatory limits, emphasizing the necessity of considering noradrenaline-induced vasorelaxation in the spinal arteries of TSCI patients.

The acute phase management of traumatic spinal cord injury (tSCI) with polytrauma: A narrative review

Introduction

Traumatic spinal cord injury (tSCI) is frequently observed in polytrauma patients.

Research question

What is the optimal strategy to manage tSCI in the setting of polytrauma?

Material and methods

This narrative review focuses on: 1) extraspinal damage control surgery and resuscitation, 2) the perioperative protection of the injured spine during emergency surgery, 3) imaging and timing of spinal surgery in polytrauma, 4) early interventions for skin, bowel and bladder, and 5) the multidisciplinary approach to tSCI polytrauma patients.

Results

Damage control resuscitation (DCR) and damage control surgery (DCS), aim to prevent/correct post-traumatic physiological derangements to minimize bleeding until definitive hemostasis is achieved. Spinal protection during emergency surgery is of paramount importance to reduce secondary insults to the injured spine. Imaging, especially magnetic resonance imaging (MRI), is useful for decision-making regarding surgical management of the injured spine. Early decompressive surgery (within 24 h from trauma) is associated with better neurological outcomes. Early consultation with a physical medicine and rehabilitation physician is beneficial to optimize recovery. A close collaboration between different medical specialties involved in the early management of tSCI patients with polytrauma is advisable to improve outcome.

Discussion and conclusion

This narrative review aims to collate basic knowledge regarding acute phase management of tSCI patients in the context of polytrauma. More evidence and data form well-powered studies are necessary in this setting.

The concepts of Intra Spinal Pressure (ISP), Intra Thecal Pressure (ITP), and Spinal Cord Perfusion Pressure (SCPP) in acute, severe traumatic spinal cord injury: Narrative review

There is increasing interest in monitoring pressure from the injured spinal cord to guide the management of patients with acute, severe traumatic spinal cord injuries (TSCI). This is analogous to monitoring intracranial pressure and cerebral perfusion pressure in traumatic brain injury (TBI). Here, we explore key concepts in this field and novel therapies that are emerging from these ideas. We argue that the Monro-Kellie doctrine, a fundamental principle in TBI, may also apply to TSCI as follows: The injured cord swells, initially displacing surrounding cerebrospinal fluid (CSF) that prevents a rise in spinal cord pressure; once the CSF space is exhausted, the spinal cord pressure at the injury site rises. The spinal Monro-Kellie doctrine allows us to define novel concepts to guide the management of TSCI based on principles employed in the management of TBI such as intraspinal pressure (ISP), intrathecal pressure (ITP), spinal cord perfusion pressure (SCPP), spinal pressure reactivity index (sPRx), and optimum SCPP (SCPPopt). Draining lumbar CSF and expansion duroplasty are currently undergoing clinical trials as novel therapies for TSCI. We conclude that there is acknowledgement that blood pressure targets applied to all TSCI patients are inadequate. Current research aims to develop individualised management based on ISP/ITP and SCPP monitoring. These techniques are experimental. A key controversy is whether the spinal cord pressure is best measured from the injury site (ISP) or from the lumbar cerebrospinal fluid (ITP).

Invasive devices to monitor the intraspinal perfusion pressure in the hemodynamic management of acute spinal cord injury: A systematic scoping review

BACKGROUND

Various methods for measuring intrathecal pressure (ITP) after spinal cord injury (SCI) to guide hemodynamic management have been investigated. To synthesize the current literature, this current study conducted a scoping review of the use of intrathecal devices to monitor ITP during acute management of SCI with the aim of understanding the association between ITP monitoring with physiological and clinical outcomes.

METHODS

A systematic review of literature following the Cochrane Handbook for Systematic Reviews of Interventions and Preferred Reporting Items for Systematic Reviews and Meta-Analysis statement. All eligible studies were screened for inclusion and exclusion criteria. Data extracted included number of patients included, severity of injury, characteristics of the intervention-intrathecal device used to record the ITP, outcomes -hemodynamic parameters observed, changes in the American Spinal Injury Association (ASIA) Impairment Scale (AIS), total motor scores, association of ITP with other physiological variables.

RESULTS

The search yielded a total of 1,698 articles, of which 30 observational studies and 2 randomized clinical trials were deemed eligible based on their use of an intrathecal invasive device to monitor spinal cord perfusion pressure (SCPP) in patients with SCI. Of these, 9 studies used a lumbar drain, 23 a Codman pressure probe and 1 study that used both. These studies underscore the crucial interplay between ITP, the SCPP and physiological variables, with neurological outcome. It is still unclear whether monitoring from a lumbar drain is accurate enough to highlight what is occurring at the site of SCI, which is the main advantage of Codman Probe, however, the latter requires specialized personnel that may not be available in most settings. Minor adverse effects were associated with lumbar drain catheters, while cerebrospinal fluid leak requiring repair (~ 7%) is the main concern with Codman Probes.

CONCLUSION

Future investigation of SCPP protocols via lumbar drains and Codman probes ought to involve multi-centered randomized controlled trials and continued translational investigation with animal models.

Neurocritical care and neuromonitoring considerations in acute pediatric spinal cord injury

Management of pediatric spinal cord injury (SCI) is an essential skill for all pediatric neurocritical care physicians. In this review, we focus on the evaluation and management of pediatric SCI, highlight a novel framework for the monitoring of such patients in the intensive care unit (ICU), and introduce advancements in critical care techniques in monitoring and management. The initial evaluation and characterization of SCI is crucial for improving outcomes as well as prognostication. While physical examination and imaging are the main stays of the work-up, we propose the use of somatosensory evoked potentials (SSEPs) and transcranial magnetic stimulation (TMS) for challenging clinical scenarios. SSEPs allow for functional evaluation of the dorsal columns consisting of tracts associated with hand function, ambulation, and bladder function. Meanwhile, TMS has the potential for informing prognostication as well as response to rehabilitation. Spine stabilization, and in some cases surgical decompression, along with respiratory and hemodynamic management are essential. Emerging research suggests that targeted spinal cerebral perfusion pressure may provide potential benefits. This review aims to increase the pediatric neurocritical care physician's comfort with SCI while providing a novel algorithm for monitoring spinal cord function in the ICU.

Traumatic cervical spinal cord injury: Comparison of two different blood pressure targets on neurological recovery

BACKGROUND

Controversy exists whether blood pressure augmentation therapy benefits patients suffering from spinal cord injury (SCI). This retrospective comparative study was designed to assess the impact of two different mean arterial pressure (MAP) targets (85-90 mmHg vs. 65-85 mmHg) on neurological recovery after traumatic cervical SCI.

METHODS

Fifty-one adult patients with traumatic cervical SCI were retrospectively divided into two groups according to their intensive care unit (ICU) MAP targets: 85-90 mmHg (higher MAP group, n = 32) and 65-85 mmHg (lower MAP group, n = 19). Invasive MAP measurements were stored as 2-min median values for 3-7 days. The severity of SCI (AIS grade and neurological level) was evaluated upon ICU stay and during rehabilitation. Neurological recovery was correlated with individual mean MAP values and with the proportion of MAP values ≥85 mmHg upon the first 3 days (3d-MAP%≥85 ).

RESULTS

The initial AIS grades were A 29.4%, B 17.6%, C 31.4%, and D 21.6%. AIS grade improved in 24 patients (47.1%). During ICU care, 82.0% and 36.8% of the measured MAP values reached ≥85 mmHg in the higher and the lower MAP groups, respectively (p < .001). The medians of individual mean MAP values were different between the groups (90.2 mmHg vs. 81.4 mmHg, p < .001). Similarly, 3d-MAP%≥85 was higher in the higher MAP group (85.6% vs. 50.0%, p < .001). However, neurological recovery was not different between the groups, nor did it correlate with individual mean MAP values or 3d-MAP%≥85 .

CONCLUSION

The currently recommended MAP target of 85-90 mmHg was not associated with improved outcomes compared to a lower target in patients with traumatic cervical SCI in this cohort.

Early management of adult traumatic spinal cord injury in patients with polytrauma: a consensus and clinical recommendations jointly developed by the World Society of Emergency Surgery (WSES) & the European Association of Neurosurgical Societies (EANS)

BACKGROUND

The early management of polytrauma patients with traumatic spinal cord injury (tSCI) is a major challenge. Sparse data is available to provide optimal care in this scenario and worldwide variability in clinical practice has been documented in recent studies.

METHODS

A multidisciplinary consensus panel of physicians selected for their established clinical and scientific expertise in the acute management of tSCI polytrauma patients with different specializations was established. The World Society of Emergency Surgery (WSES) and the European Association of Neurosurgical Societies (EANS) endorsed the consensus, and a modified Delphi approach was adopted.

RESULTS

A total of 17 statements were proposed and discussed. A consensus was reached generating 17 recommendations (16 strong and 1 weak).

CONCLUSIONS

This consensus provides practical recommendations to support a clinician's decision making in the management of tSCI polytrauma patients.

Adverse Effect of Neurogenic, Infective, and Inflammatory Fever on Acutely Injured Human Spinal Cord

This study aims to determine the effect of neurogenic, inflammatory, and infective fevers on acutely injured human spinal cord. In 86 patients with acute, severe traumatic spinal cord injuries (TSCIs; American Spinal Injury Association Impairment Scale (AIS), grades A-C) we monitored (starting within 72 h of injury, for up to 1 week) axillary temperature as well as injury site cord pressure, microdialysis (MD), and oxygen. High fever (temperature ≥38°C) was classified as neurogenic, infective, or inflammatory. The effect of these three fever types on injury-site physiology, metabolism, and inflammation was studied by analyzing 2864 h of intraspinal pressure (ISP), 1887 h of MD, and 840 h of tissue oxygen data. High fever occurred in 76.7% of the patients. The data show that temperature was higher in neurogenic than non-neurogenic fever. Neurogenic fever only occurred with injuries rostral to vertebral level T4. Compared with normothermia, fever was associated with reduced tissue glucose (all fevers), increased tissue lactate to pyruvate ratio (all fevers), reduced tissue oxygen (neurogenic + infective fevers), and elevated levels of pro-inflammatory cytokines/chemokines (infective fever). Spinal cord metabolic derangement preceded the onset of infective but not neurogenic or inflammatory fever. By considering five clinical characteristics (level of injury, axillary temperature, leukocyte count, C-reactive protein [CRP], and serum procalcitonin [PCT]), it was possible to confidently distinguish neurogenic from non-neurogenic high fever in 59.3% of cases. We conclude that neurogenic, infective, and inflammatory fevers occur commonly after acute, severe TSCI and are detrimental to the injured spinal cord with infective fever being the most injurious. Further studies are required to determine whether treating fever improves outcome. Accurately diagnosing neurogenic fever, as described, may reduce unnecessary septic screens and overuse of antibiotics in these patients.

Spinal cord perfusion pressure correlates with breathing function in patients with acute, cervical traumatic spinal cord injuries: an observational study

OBJECTIVE

This study aims to determine the relationship between spinal cord perfusion pressure (SCPP) and breathing function in patients with acute cervical traumatic spinal cord injuries.

METHODS

We included 8 participants without cervical TSCI plus 13 patients with cervical traumatic spinal cord injuries, American Spinal Injury Association Impairment Scale grades A-C. In the TSCI patients, we monitored intraspinal pressure from the injury site for up to a week and computed the SCPP as mean arterial pressure minus intraspinal pressure. Breathing function was quantified by diaphragmatic electromyography using an EDI (electrical activity of the diaphragm) nasogastric tube as well as by ultrasound of the diaphragm and the intercostal muscles performed when sitting at 20°-30°.

RESULTS

We analysed 106 ultrasound examinations (total 1370 images/videos) and 198 EDI recordings in the patients with cervical traumatic spinal cord injuries. During quiet breathing, low SCPP (< 60 mmHg) was associated with reduced EDI-peak (measure of inspiratory effort) and EDI-min (measure of the tonic activity of the diaphragm), which increased and then plateaued at SCPP 60-100 mmHg. During quiet and deep breathing, the diaphragmatic thickening fraction (force of diaphragmatic contraction) plotted versus SCPP had an inverted-U relationship, with a peak at SCPP 80-90 mmHg. Diaphragmatic excursion (up and down movement of the diaphragm) during quiet breathing did not correlate with SCPP, but diaphragmatic excursion during deep breathing plotted versus SCPP had an inverse-U relationship with a peak at SCPP 80-90 mmHg. The thickening fraction of the intercostal muscles plotted versus SCPP also had inverted-U relationship, with normal intercostal function at SCPP 80-100 mmHg, but failure of the upper and middle intercostals to contract during inspiration (i.e. abdominal breathing) at SCPP < 80 or > 100 mmHg.

CONCLUSIONS

After acute, cervical traumatic spinal cord injuries, breathing function depends on the SCPP. SCPP 80-90 mmHg correlates with optimum diaphragmatic and intercostal muscle function. Our findings raise the possibility that intervention to maintain SCPP in this range may accelerate ventilator liberation which may reduce stay in the neuro-intensive care unit.

Spontaneous spinal cord infarctions: a systematic review and pooled analysis protocol

INTRODUCTION

Spinal cord infarction (SCInf) is a rare ischaemic event that manifests with acute neurological deficits. It is typically classified as either spontaneous, defined as SCInf without any inciting event, or periprocedural, which typically occur in conjunction with vascular surgery with aortic manipulations. While periprocedural SCInf has recently been the subject of intensified research, especially focusing on the primary prevention of this complication, spontaneous SCInf remains less studied.

METHODS AND ANALYSIS

Electronic databases, including PubMed, Web of Science and Embase, will be searched using the keywords "spinal cord", "infarction", "ischemia" and "spontaneous". The search will be set to provide only English studies published from database inception. Editorials, letters and reviews will also be excluded. Reference lists of relevant records will also be searched. Identified studies will be screened for inclusion, by one reviewer in the first step and then three in the next step to decrease the risk of bias. The synthesis will address several topics of interest including epidemiology, presentation, diagnostics, treatment strategies, outcomes and predictors. The review aims to gather the body of evidence to summarise the current knowledge on SCInf. This will lead to a better understanding of the condition, its risk factors, diagnosis and management. Moreover, the review will also provide an understanding of the prognosis of patients with SCInf with respect to neurological function, quality of life and mortality. Finally, this overview of the literature will allow the identification of knowledge gaps to help guide future research efforts.

ETHICS AND DISSEMINATION

Ethics approval was not required for our review as it is based on existing publications. The final manuscript will be submitted to a peer-reviewed journal.

Differential Trajectory of Diffusion and Perfusion Magnetic Resonance Imaging of Rat Spinal Cord Injury

Traumatic spinal cord injury causes rapid neuronal and vascular injury, and predictive biomarkers are needed to facilitate acute patient management. This study examined the progression of magnetic resonance imaging (MRI) biomarkers after spinal cord injury and their ability to predict long-term neurological outcomes in a rodent model, with an emphasis on diffusion-weighted imaging (DWI) markers of axonal injury and perfusion-weighted imaging of spinal cord blood flow (SCBF). Adult Sprague-Dawley rats received a cervical contusion injury of varying severity (injured = 30, sham = 9). MRI at 4 h, 48-h, and 12-weeks post-injury included T1, T2, perfusion, and DWI. Locomotor outcome was assessed up to 12 weeks post-injury. At 4 h, the deficit in SCBF was larger than the DWI lesion, and although SCBF partially recovered by 48 h, the DWI lesion expanded. At 4 h, the volume of the SCBF deficit (R2 = 0.56, padj < 0.01) was significantly correlated with 12-week locomotor outcome, whereas DWI (R2 = 0.30, padj < 0.01) was less predictive of outcome. At 48 h, SCBF (R2 = 0.41, padj < 0.01) became less associated with outcome, and DWI (R2 = 0.38, padj < 0.01) lesion volume became more closely related to outcome. Spinal cord perfusion has unique spatiotemporal dynamics compared with diffusion measures of axonal damage and highlights the importance of acute perfusion abnormalities. Perfusion and diffusion offer complementary and clinically relevant insight into physiological and structural abnormalities following spinal cord injury beyond those afforded by T1 or T2 contrasts.

Significance of spinal cord perfusion pressure following spinal cord injury: A systematic scoping review

This scoping review systematically reviewed relevant research to summarize the literature addressing the significance of monitoring spinal cord perfusion pressure (SCPP) in acute traumatic spinal cord injury (SCI). The objectives of the review were to (1) examine the nature of research in the field of SCPP monitoring in SCI, (2) summarize the key research findings in the field, and (3) identify research gaps in the existing literature and future research priorities. Primary literature searches were conducted using databases (Medline and Embase) and expanded searches were conducted by reviewing the references of eligible articles and searches of Scopus, Web of Science core collection, Google Scholar, and conference abstracts. Relevant data were extracted from the studies and synthesis of findings was guided by the identification of patterns across studies to identify key themes and research gaps within the literature. Following primary and expanded searches, a total of 883 articles were screened. Seventy-three articles met the review inclusion criteria, including 34 original research articles. Other articles were categorized as conference abstracts, literature reviews, systematic reviews, letters to the editor, perspective articles, and editorials. Key themes relevant to the research question that emerged from the review included the relationship between SCPP and neurological recovery, the safety of monitoring pressures within the intrathecal space, and methods of intervention to enhance SCPP in the setting of acute traumatic SCI. Original research that aims to enhance SCPP by targeting increases in mean arterial pressure or reducing pressure in the intrathecal space is reviewed. Further discussion regarding where pressure within the intrathecal space should be measured is provided. Finally, we highlight research gaps in the literature such as determining the feasibility of invasive monitoring at smaller centers, the need for a better understanding of cerebrospinal fluid physiology following SCI, and novel pharmacological interventions to enhance SCPP in the setting of acute traumatic SCI. Ultimately, despite a growing body of literature on the significance of SCPP monitoring following SCI, there are still a number of important knowledge gaps that will require further investigation.