Abstract
Background
Treatment of blunt traumatic spinal cord injuries (SCIs) often includes maintaining elevated mean arterial blood pressures (MAP) to enhance perfusion to the spinal cord. Optimal hyperperfusion protocols and treatment algorithms have yet to be delineated due to a paucity of large volume prospective studies. This study aims to identify predictors of neurological improvement in American Spinal Injury Association (ASIA) impairment score following blunt SCI.
Study design
Prospective (January 10, 2021 to June 1, 2023) multicenter study included blunt SCI patients age >18 with complete neurological examination documented on hospital arrival. Patients were divided into two groups: neurological improvement and no improvement, based on their change in ASIA score from arrival to hospital discharge.
Results
A total of 19 centers contributed 222 patients of those, 164 had pre-ASIA and post-ASIA scores. The ASIA improvement group had 36 patients (22%). There was no statistical difference in the median percentage of time patients spent at a MAP >85 mm Hg during treatment 80.7% (IQR 63.6, 93.4) no improvement vs 83.6% (IQR 70.1, 93.0) in the improvement, (p=0.87). There was no difference in the median duration of MAP treatment in hours between the groups (95.6 hours (IQR 62.55, 113.48) in the no improvement group versus 96 (IQR 72, 113.5) (p=0.40) in the improvement group).
Conclusions
Overall, 22% of all blunt SCI patients saw an improvement in their ASIA score. Adherence to and length of MAP augmentation was not a statistically significantly different between groups.
Level of evidence
Level IV Therapeutic/Care Management.
Keywords: Spinal Cord Injuries
WHAT IS ALREADY KNOWN ON THIS TOPIC
Mean arterial pressure augmentation is the current standard of practice for the treatment of blunt traumatic spine cord injuries.
WHAT THIS STUDY ADDS
This is the largest population study of mean arterial pressure augmentation in blunt traumatic spinal cord injured patients. This study questions the utility of this practice with association of improvement in neurologic outcomes.
HOW THIS STUDY MIGHT AFFECT RESEARCH, PRACTICE OR POLICY
This study might change how blunt traumatic spinal cord injured patients are treated in relation to mean arterial pressure augmentation.
Introduction
Blunt traumatic spinal cord injury (SCI) is prevalent across all age groups, and with increased incidence, there is increased attentiveness to treatment in the trauma community.1 The physiology of blunt SCI involves a mechanical disruption of the spinal cord which negatively impacts nutrient delivery and autoregulation.2 3 Neurological deficits from these injuries are based on the initial severity as well as secondary insults at the molecular level related to ischemia and inflammation.4 SCI recovery encompasses short-term (inpatient care) and long-term (postdischarge/rehabilitation) treatment plans with the aim to recover as much neurological function as possible.5 The American Spinal Injury Association Impairment Scale (ASIA) is an established grading system to classify the complete or incomplete nature of both motor and sensory neurological deficits. ASIA grades range from complete motor and sensory loss classified as ASIA A to a normal neurological exam classified as ASIA E. It is a reliable tool in evaluating neurological deficits in adult SCI patients.6
The goal of acute inpatient acute care for blunt SCI is to minimize spinal cord tissue hypoperfusion/hypoxia and prevent ongoing spinal cord damage which leads to worsening neurological function.2 3 Clinical measurements of intraspinal pressures have been recorded by Werndle et al using a catheter placed in the dural sac at the time of laminectomy for traumatic SCI from which the authors were able to derive spinal perfusion pressures.7 This is a cumbersome process, so mean arterial pressure (MAP) is used as a surrogate marker of spinal cord perfusion.7 Specific treatment regimens targeting MAP goals and duration of MAP augmentation vary without consensus, and no randomized control trial detailing this treatment exists in the literature.8,14 The current best practice guidelines for spine injury as outlined by the Trauma Quality Improvement Program published by the American College of Surgeons and the American Congress of Rehabilitation Medicine is to obtain a MAP of 85–90 mm Hg for up to 7 days postinjury.15
Vasopressor therapy to augment MAP is not without potential risks, including arrhythmias and myocardial infarction.16 The existing literature lacks large population studies examining MAP augmentation in SCI. A meta-analysis of the existing studies failed to find a conclusive correlation between elevated MAP augmentation and improved neurological function.11 Even with a lack of evidence for MAP augmentation, this treatment algorithm continues across the trauma community. This study aims to create a large population study of blunt traumatic SCI patients and assess if MAP augmentation is associated with improved ASIA scores from admission to discharge. We hypothesize that acute, postinjury MAP augmentation treatment is associated with improved neurological function as demonstrated by an improvement in ASIA score.
Methods
This was a prospective observational multicenter trial studying MAP augmentation in the treatment of SCI (MAP Study). It was endorsed by The Eastern Association for the Surgery of Trauma’s Multi-Institutional Trial Committee in 2021. After institutional review board approval and waiver of informed consent was granted, participating trauma centers (level I and II) collected data from October 1, 2021,to June 30, 2023. Strengthening the Reporting of Observational Studies in Epidemiology guidelines were used to ensure proper reporting of data, methods, and results. Participant data were stored and managed securely in a Research Electronic Data Capture tool.
Any blunt traumatic SCI patients ages 18 and older who were treated with a MAP augmentation protocol were included. MAP augmentation protocols varied by institution, but specific data points were collected for the first 96 hours of treatment. This time period was used as it encompassed the treatment duration of every contributing center regardless of individual protocol. Exclusion criteria were as follows: penetrating mechanisms, prisoners, pregnant patients, non-trauma patients treated with MAP augmentation, and patients missing a pretreatment and/or post-treatment ASIA score.
The primary outcome of neurological improvement was determined by the ASIA score on the day of discharge relative to the day of admission. Patients were divided into two groups: Improvement (positive change in ASIA score from hospital day 1 (HOD) to discharge) and No improvement (worsened or no change in ASIA score from HOD 1 to discharge). To reduce bias, the patient’s ASIA score was calculated or recorded from the electronic documentation of a neurosurgical provider, trauma provider, or physical medicine and rehabilitation physician.
Specifics of MAP treatment included admission vitals and hourly vitals for a total of 96 hours. MAP readings were directly recorded from the electronic medical record or calculated using the systolic and diastolic blood pressure readings. To account for the hourly vital signs during a patient’s operative intervention, we used the vital signs associated with the top of the hour for each hour while the patient was in a neurosurgical procedure. Blood pressure specifics, systolic, diastolic, and MAP readings, were recorded from an arterial line or a blood pressure cuff, whichever the patient had at the time of the recording.
Additional variables collected included demographics, injury specifics including SCI anatomic location (cervical, thoracic, and lumbar), Injury Severity Score (ISS), type of intravenous vasopressor, duration of vasopressor use, and neurosurgical operative intervention. Incidence of complications while undergoing MAP augmentation, such as elevated serum troponin, arrhythmias, and in-patient cardiology consultations, was collected. Other outcomes, including intensive care unit (ICU) length of stay, hospital length of stay, discharge location (postacute care location type), and mortality after 96 hours of MAP augmentation were collected.
Continuous variables are presented using median and IQR while categorical variables are presented using frequencies and percentages. Continuous variables were compared using Wilcoxon rank-sum test. Categorical variables were compared using χ2 and Fisher’s exact tests. A proportional odds model was performed modeling the probability of ASIA score at discharge being improved. Proportional ORs with 95% CIs were determined for each factor on ASIA score at discharge. A p<0.05 was used for statistical significance. A loess analysis was performed to plot the relationship between HOD 1 ASIA score and discharge ASIA score. All statistical analyses were performed using SAS software (SAS Institute).
Results
A total of 19 level I and II trauma centers enrolled 222 patients to the study. After exclusions, a total of 164 patients were included in the analysis (figure 1). The patients were divided into two groups based on ASIA difference from HOD 1 to discharge. The improvement group consisted of patients whose ASIA scores improved, n=36 (22%); the no improvement group consisted of patients whose ASIA scores worsened or did not change, n=128 (78%).
Figure 1. Flow chart of inclusion and exclusions. ASIA, American Spinal Injury Association; MAP, mean arterial pressure.
Demographics and injury specifics
Demographics between the groups were statistically similar (table 1). However, female sex was associated with improved neurological function (p=0.04). The median age was similar in both groups. The two groups had similar hospital length of stay, ICU length of stay, prehospital transfer percentage, and mortality after 96 hours. Injury specifics were also similar between groups. There was no difference in ISS, AIS cervical spine, AIS thoracic spine, or AIS lumbar spine between the two groups. Neurosurgical operative intervention was similar between groups, with 77.8% of patients in the improvement group (n=28) and 65.6% patients in the no improvement group (n=84) (p=0.17). Postinjury discharge location distributions were similar, with most patients in each group discharging to an inpatient rehabilitation facility (58.20% of the non-improved patients and 58.33% of the improved patients, (p=0.064)).
Table 1. Demographics, injury specifics, and patient specifics.
| Descriptive statistics | ||||
|---|---|---|---|---|
| Variables | No improvement (n=128) |
Improvement (n=36) |
P value*† | |
| Age, median (IQR) | 54.0 (36.5, 66.0) | 53.0 (43.0, 66.0) | 0.965 | |
| Sex, N (%) | Female | 31 (24.22) | 15 (41.67) | 0.0395* |
| Male | 97 (75.78) | 21 (58.33) | ||
| Race, N (%) | White | 91 (71.65) | 22 (61.11) | 0.226 |
| Non-white | 36 (28.35) | 14 (38.89) | ||
| BMI, median (IQR) | 27.9 (24.5, 32.9) | 27.35 (22.95, 31.85) | 0.502 | |
| Hopsital LOS, median (IQR) | 12 (7, 20) | 13 (8.5, 27.5) | 0.271 | |
| ICU LOS, median (IQR) | 6 (3.5, 9) | 5 (4, 7.5) | 0.747 | |
| Mortality, N (%) | Yes | 13 (10.48) | 1 (2.78) | 0.195 |
| No | 111 (89.52) | 35 (97.22) | ||
| Hospital transfer, N (%) | Yes | 29 (23.39) | 10 (29.41) | 0.470 |
| No | 95 (76.61) | 24 (70.59) | ||
| Injury specifics | ||||
| Injury Severity Score, median (IQR) | 20.5 (16, 30) | 21.0 (17.0, 27.5) | 0.538 | |
| AIS head, median (IQR) | 2 (1, 3) | 2 (1, 4) | 0.827 | |
| AIS C-Spine, median (IQR) | 4 (3.5, 4) | 4 (3, 5) | 0.904 | |
| AIS T-Spine, median (IQR) | 4 (3, 5) | 4 (2, 5) | 0.856 | |
| AIS L-Spine, median (IQR) | 2 (2, 3) | 4 (2, 4) | 0.259 | |
| AIS abdomen, median (IQR) | 2 (2, 2) | 2 (1, 3) | 0.815 | |
| AIS chest, median (IQR) | 3 (2, 3) | 2 (2, 4) | 0.947 | |
| Cervical spine injury, N (%) | Yes | 101 (78.91) | 29 (80.56) | 0.829 |
| No | 27 (21.09) | 7 (19.44) | ||
| Thoracic spine injury, N (%) | Yes | 38 (29.69) | 6 (16.67) | 0.119 |
| No | 90 (70.31) | 30 (83.33) | ||
| Lumbar spine injury, N (%) | Yes | 11 (8.59) | 5 (13.89) | 0.348 |
| No | 117 (91.41) | 31 (86.11) | ||
| Mechanism of injury, N (%) | Fall (standing or a height) | 56 (44.09) | 17 (47.22) | 0.784 |
| MVC (motor vehicle) | 43 (33.86) | 10 (27.78) | ||
| Others* | 28 (22.05) | 9 (25.00) | ||
| Discharge location, N (%) | Home (includes home with services) | 24 (19.67) | 6 (16.67) | 0.064 |
| Inpatient rehabilitation | 71 (58.20) | 21 (58.33) | ||
| Long-term care facility (LTACH) | 11 (9.02) | 2 (5.56) | ||
| Skilled nursing facility | 4 (3.28) | 6 (16.67) | ||
| If deceased (Coroner) | 12 (9.84) | 1 (2.78) |
Wilcoxon rank-sum test as used to compare the median between the two groups; χ2 and Fisher’s exact tests were used to test the difference of categorical variables between the two groups.
Others include motorcycle accident, pedestrian struck, assault and others.
P value * < 0.05
AIS, Abbreviated Injury Score; BMI, body mass index; ICU, intensive care unit; LOS, length of stay; LTACH, Long Term Care Facility; MVC, Motor vehicle collision.
MAP augmentation specifics
The median duration of treatment, in hours, for the no improvement group was 95.6 (IQR 62.55, 113.48) vs 96 (IQR 72, 113.5) (p=0.40) in the improvement group. The median total treatment time the patient spent at greater than or equal to the target MAP of 85 mm Hg (represented as a percentage) was 80.7% (IQR 63.6, 93.4) for the no improvement vs 83.6% (IQR 70.1, 93.0) (p=0.87) in the improvement. Finally, rates of steroid use and number of invasive lines, both arterial and central venous, were similar between groups (table 2).
Table 2. Patient treatment specifics.
| Trauma bay labs/vitals |
No improvement(n=128) | Improvement (n=36) | P value* | |
|---|---|---|---|---|
| Heart rate, Median (IQR) | 77 (69, 93) | 78 (65, 91) | 0.777 | |
| Systolic blood pressure, median (IQR) | 131 (117.5, 145) | 132 (114, 148) | 0.816 | |
| Diastolic blood pressure, median (IQR) | 79 (67.5, 91) | 81 (70, 99) | 0.510 | |
| Mean arterial pressure, median (IQR) | 98.0 (85.0, 107.0) | 95.0 (85, 115) | 0.921 | |
| Respiratory rate, median (IQR) | 18 (16, 22) | 18 (17, 23) | 0.570 | |
| Lactate, median (IQR) | 1.9 (1.3, 2.6) | 2.05 (1.3, 2.7) | 0.619 | |
| pH, median (IQR) | 7.360 (7.315, 7.410) | 7.34 (7.31, 7.37) | 0.423 | |
| Creatinine, median (IQR) | 0.92 (0.73, 1.10) | 0.9 (0.64, 1.11) | 0.687 | |
| Hemoglobin, median (IQR) | 13.3 (12.0, 14.7) | 13.35 (11.1, 14.65) | 0.722 | |
| MAP specifics | ||||
| MAP duration hours, median (IQR) | 95.6 (62.55, 113.48) | 96 (72, 113.5) | 0.400 | |
| % Treatment time MAP≥85 mm Hg, median (IQR) | 80.7 (63.6, 93.4) | 83.6 (70.1, 93.0) | 0.874 | |
| Steroid use N, (%) | Yes | 19 (15.97) | 5 (14.29) | 0.810 |
| No | 100 (84.03) | 30 (85.71) | ||
| Number of arterial lines, median (IQR) | 1 (1, 1) | 1 (1, 1) | 0.610 | |
| Number of central lines, median (IQR) | 0 (0, 1) | 0 (0, 1) | 0.998 | |
| Complications | ||||
| Atrial fibrillation, N (%) | Yes | 9 (7.44) | 3 (8.82) | 0.726 |
| No | 112 (92.56) | 31 (91.18) | ||
| Ventricular tachycardia, N (%) | Yes | 2 (1.67) | 2 (5.88) | 0.212 |
| No | 118 (98.33) | 32 (94.12) | ||
| Elevated troponin, N (%) | Yes | 10 (8.55) | 5 (14.71) | 0.330 |
| No | 107 (91.45) | 29 (85.29) | ||
| Cardiology consultation, N (%) | Yes | 18 (14.88) | 8 (23.53) | 0.233 |
| No | 103 (85.12) | 26 (76.47) | ||
Wilcoxon rank-sum test as used to compare the median between the two groups; χ2 and Fisher’s exact tests were used to test the difference of categorical variables between the two groups.
P value < 0.05
MAP, mean arterial pressure.
Given a lack of statistically significant differences between both groups when a logistic regression model was introduced, a proportional odds model was completed to assess the odds of ASIA score change at discharge with results found in table 3. Females were more likely to have increased odds of improvement in ASIA score compared with males, OR 2.9 (95% CI 1.207 to 7.019 p=0.017). Higher ASIA scores on HOD 1 were significantly less likely to show odds of improvement in discharge ASIA scores, OR 0.028 (95% CI 0.012 to 0.062, p<0.001). Percentage of treatment time at a MAP goal of 85 mm Hg was not significantly associated with an increased odd of neurological improvement, OR 2.029 (95% CI 0.282 to 14.579, p=0.482).
Table 3. Proportional odds modeling for improvement.
| Variable | Comparison | OR | 95% CI | P value |
|---|---|---|---|---|
| Age | Per year increase | 0.977 | (0.953 to 1.003) | 0.0784 |
| Biological sex | Female vs male | 2.911 | (1.207 to 7.019) | 0.0174* |
| Race | Non-white vs white | 2.066 | (0.855 to 4.987) | 0.1068 |
| ASIA Score HOD 1 | Per unit increase | 0.028 | (0.012 to 0.062) | <0.0001* |
| Injury Severity Score | Per unit increase | 0.991 | (0.960 to 1.022) | 0.5701 |
| Mechanism of injury | Fall vs others† | 0.993 | (0.342 to 2.884) | 0.9901 |
| MVC vs others† | 0.461 | (0.145 to 1.470) | 0.1906 | |
| % MAP total treatment time >85 | Per percent increase | 2.029 | (0.282 to 14.579) | 0.4821 |
| Hospital transfer | Yes vs No | 1.186 | (0.431 to 3.265) | 0.7415 |
| Cervical spine injury | Yes vs No | 0.699 | (0.196 to 2.492) | 0.5809 |
| Thoracic spine injury | Yes vs No | 0.454 | (0.127 to 1.616) | 0.2228 |
| Steroid use | Yes vs No | 0.644 | (0.192 to 2.162) | 0.4766 |
Statistically significant values.
Others include motorcycle, automobile versus pedestrians, assault.
ASIA, American Spinal Injury Association; HOD, hospital day; MAP, mean arterial pressure.
Secondary outcomes
Neither hospital nor ICU length of stay was significantly different between the improvement and no improvement cohorts. Complications were similar between the two groups (table 2), with no significant difference found in incidence of atrial fibrillation, ventricular tachycardia, troponin elevation, or consults placed to Cardiology. Mortality was not significantly different between the two groups.
ASIA score
Change in ASIA score from HOD 1 to discharge was examined with regard to admission ASIA score. ASIA change in both groups from HOD 1 to discharge can be found in figure 2. There were 51 ASIA A patients on HOD 1 and 42 ASIA A patients at discharge. Of the 11 HOD 1 ASIA A patients that improved, 6 became ASIA B, 4 became ASIA C, and 1 became ASIA D. All HOD 1 ASIA B (n=5) and ASIA C (n=16) patients improved by one ASIA level at discharge (figure 2). A loess analysis was completed, which displays the relationship between HOD 1 ASIA and discharge ASIA as a logistical regression model (figure 3). The smooth linear upward trend shows the relationship between HOD 1 ASIA and discharge ASIA remains constant. This visually demonstrates that, despite some variability in discharge ASIA score relative to admission, most ASIA scores remain the same from HOD 1 to discharge.
Figure 2. (a) Change in ASIA score from HOD 1 to discharge all patients combined. With all patients combined, fewer patients had an ASIA A at discharge as compared to the ASIA score of all patients on HOD 1. (B) Improvement group change is ASIA score from HOD 1 to discharge. Overall, more patients were discharged as ASIA D. (C) No improvement group ASIA change HOD 1 to discharge. Two patients who were determined to be ASIA C on HOD 1 were discharged with a worsened ASIA score of A. Of the patients who did improve, HOD 1 score a B, C, and E remained at those ASIA’s upon discharge. ASIA, American Spinal Injury Association; HOD, hospital day.
Figure 3. Loess plot of HOD 1 to discharge ASIA score. Charts the HOD 1 ASIA score (start) and the ASIA score at discharge as a linear regression. ASIA, American Spinal Injury Association; HOD, hospital day.
Discussion
In this study of 164 blunt SCI patients, 22% had an improvement in ASIA score from admission to discharge. Only female sex was significantly associated with this improvement. Use of MAP augmentation did not predict improvement in ASIA score, with neither the duration of MAP augmentation nor the percentage of time spent with a MAP >85 having any significant association with neurological improvement.
To the authors’ knowledge, this is the largest multicenter study of neurological prognosis for blunt traumatic SCI patients who underwent MAP augmentation. Patients received similar treatment duration and percentage of time at a goal MAP of 85 mm Hg during their acute care treatment without significant difference in their neurological outcome. Patients were discharged to similar locations, inpatient rehabilitation facilities, regardless of neurological improvement. This lack of association of MAP augmentation with neurological improvement raises important questions about the utility of MAP augmentation in the treatment of blunt SCI.
Vale et al performed one of the first intensive studies focused on improvement in neurological outcomes with MAP augmentation. They found that at 12 months postinjury, 60% of complete spinal cord injured patients treated with MAP augmentation had an improvement of one ASIA grade.12 Although our study did not include long-term follow-up, inpatient treatment is theorized to affect long-term outcomes. This work was expanded on with small population studies. Hawryluk et al, with a total of 74 patients, concluded the patient group that achieved an ASIA improvement of greater than 1 had higher mean MAPs and less proportion of time spent with a MAP <85 mm Hg.2 Although our methodology was similar, we found no difference in outcomes which could be attributed to our larger population size. Dakson et al examined change in ASIA motor scale from admission to discharge in 61 patients. The authors found 82% did not reach a target MAP of 85 mm Hg for at least two consecutive hours, but of those patients who met their MAP goal, 43% improved. Additionally, when confounding variables were not controlled, they found a MAP <85 mm Hg was associated with lack of neurological improvement at discharge OR 0.045 (95% CI 0.01 to 0.78, p=0.003).17 Our study had similar MAP target treatment durations, which could be attributed to improved ICU attentiveness to the MAP goal. In our study, we had a larger population, but none of the MAP-related variables were associated with increased odds of neurological improvement at discharge. The difference in study size could be a major reason for the differences in outcomes.
Weinberg et al published a study with similar methodology and population size to our study. The authors had 134 patients and examined the proportion of time patients spent at a target MAP of ≥85 mm Hg with the outcome of ASIA improvement. The median percentage of treatment time at the goal MAP of ≥85 mm Hg was similar in the non-improvement and improvement groups (80.7%, 83.6% p=0.874). However, using a multivariate model, the authors found a significant association of proportion target MAP time and neurological improvement, defined as an HR 1.17 (95% CI 1.03 to 1.42); (p=0.014).14
Most patients in the Weinberg et al study (69.9% n=95) did not have a change in ASIA score. Similarly, our study had a non-improvement rate of 78% (n=124); however, our study did not find that the proportion of time at a target MAP increased the odds of neurological improvement. One of our theories for the difference between our findings and the current literature including Weinberg’s work is the use of ASIA scores.
The ASIA score used in the acute postinjury period has many limitations. The reliability of assigning an ASIA score varies based on several factors, including level of injury, severity of injury, ability of the examiner to differentiate sensory changes and complete versus incomplete injuries.35 18,21 Additionally, assessing for an ASIA score in the setting of a traumatic brain injury or neurogenic shock influences the results.3 22 Although ASIA scores are imperfect, communicating neurological deficits in a common language requires the use of the ASIA scoring system. Some of the discrepancies in ASIA scores can be due to the provider who completed the examination. Our study limited the ASIA calculation or documentation to a trauma provider, neurosurgical provider, or physical medicine and rehabilitation provider. Much of the existing literature does not specify who provided these scores. Future work in this area should determine whose clinical documentation should be used or if ASIA scores are the most comprehensive classification of these injuries. In the meantime, we feel that possible discrepancies in ASIA calculations based on interobserver variability may explain the difference in outcomes between our study and Weinberg et al.
In the search for refined evidence-based treatment of SCI, other variables including patient selection for MAP augmentation, number of treatment days, target MAP goals, and timing of surgical intervention are in continued debate. Surgical decompression along with MAP augmentation has been shown to correlate with improved neurological outcome as measured by ASIA score change at 12 months postinjury.3 17 18 We did not examine the direct association of surgical decompression and improvement in ASIA scores, and this could be an area of future study.
Additional data are necessary to determine who will benefit from MAP augmentation based on ASIA score. Catapano et al published results from 62 patients receiving MAP augmentation treatment. The authors concluded ASIA A, B, and C patients had a positive correlation of MAP augmentation treatment and improved outcome, but this relationship did not persist in the ASIA D group.23 Our study found that worse ASIA scores had a decreased odds of neurological improvement OR 0.028 (95% CI 0.012 to 0.062, p<0.001). This is also an area of future study.
It is noteworthy that female sex was a predictor of neurological improvement both as an independent predictor and as part of a multivariate analysis. While this could be viewed as a statistical anomaly, it is also in keeping with prior literature that has shown the neuroprotective effects of estrogen and progesterone.24
We feel that the greatest strength of this study is that of its size and diverse institutions contributing to the data, giving significant external validity to its results. While patients had similar demographics, mechanisms of injury, and equal severity of injury measured by ISS in both the non-improvement and improvement groups, there was no specific MAP augmentation protocol that was followed by all contributing institutions and varying practice patterns that make for a pragmatic, real-world view of SCI treatment. We were surprised that 15% of patients were given steroids as treatment. This study was a fascinating window into the variability in practice patterns throughout the country.
This study has many limitations, which should be highlighted. First, the observational nature of the methodology is associated with inherent bias. Regarding transferred patient data, it was difficult to determine the start of MAP augmentation time, so the first recorded vital signs available were used. With such a large data request, many patient records were missing some data points. To account for some of the missing MAP values, we used only the values recorded to calculate a unique per patient percentage of time at the target MAP goal. All patients were treated with MAP augmentation per their institution’s treatment algorithms, but we used a target MAP of 85 mm Hg for 96 hours for the analysis. In addition, the data lacks some degree of granularity such as which provider (trauma or neurosurgery) documented the ASIA score. As well, the neurological deficit was not broken down by motor and sensation for the purposes of this study. Although the large population size of this study is a strength, a power analysis was not performed for the specific primary outcome of interest. This study does not address long-term follow-up. Blunt SCI patients continue to rehabilitate, and improvements in neurological outcomes are observed months and years following acute injury.5 This study aimed to evaluate inpatient acute care of SCI patients not their long-term outcomes.
The most notable weakness of the study is a lack of cohort in whom MAP augmentation was not used. We collected data only on patients who underwent MAP augmentation. By breaking these patients into cohorts of improvement and no improvement, we lose the internal validity of assigning isolated association of MAP augmentation with neurological improvements and elected to study it within the constellation of demographics and treatments as a predictor of improved neurological outcome. We feel that, given the size of the study and the multiplicity of centers contributing data, there was enough variability in the two cohorts to be able to reasonably analyze the predictors and outcomes and infer clinical and statistical significance from the results.
Conclusions
Our study found the total treatment time at a goal MAP of ≥85 mm Hg was not associated with improvement in ASIA scores from HOD 1 to discharge. When controlling for confounding variables, the only clinically significant factors associated with odds of improvement were female gender and a less severe admission ASIA score. The use of MAP augmentation to improve neurological outcomes following blunt SCI continues to require refinement.
Acknowledgements
East Carolina University statistics department, Yuanuan Fu.
Footnotes
Funding: The authors have not declared a specific grant for this research from any funding agency in the public, commercial, or not-for-profit sectors.
Patient consent for publication: Not applicable.
Ethics approval: This study involves human participants and was approved by an Ethics Committee(s) or Institutional Board(s): OhioHealth IRBnet # 1810929-1; observational nature of the study with no risk.
Provenance and peer review: Not commissioned; externally peer reviewed.
Presented at: Meeting: Raymond H. Alexander MD Resident Paper Competition; 37th EAST Annual Scientific Assembly Orlando, FL, 10 January 2024.
Data availability statement
Data are available on reasonable request.
References
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Associated Data
This section collects any data citations, data availability statements, or supplementary materials included in this article.
Data Availability Statement
Data are available on reasonable request.