Article Bites #24: More than a Moment in Time: The Association between Out-of-Hospital Hypoxia and Hypotension on Traumatic Brain Injury

Article:  Spaite DW, Hu C, Bobrow BJ, Chikani V, Barnhart B, Gaither JB, et al.The effect of combined out-of-hospital hypotension and hypoxia on mortality in major traumatic brain injury. Ann Emerg Med 2017 Jan;69(1):62-72.

Background:  Hypoxia and hypotension are known to independently increase mortality in patients with severe traumatic brain injury, but their combined effects are less clear.  The objective of this study was to evaluate the association between survival with out-of-hospital hypoxia (SpO2 < 90%), hypotension (SBP< 90 mmHg) or both following traumatic brain injury.

Methods: This was a retrospective study utilizing EPIC (Excellence in Prehospital Injury Care) database which links the Arizona State Trauma Registry data with detailed out-of-hospital data for patients with major traumatic brain injury.  The EPIC trial (subsequently published) evaluated the effect of implementing out-of-hospital traumatic brain injury guidelines on outcome following major traumatic brain injury.  This study analyzed the EPIC pre-intervention cohort, including patients age > 10 years of age and treated between January, 2007 and March 2014.

Blood pressure and oxygen saturation data were evaluated by reviewing every documented measurement for each patient during the out-of-hospital phase of care.  A patient was categorized as having hypotension if there was single documented SBP < 90 mmHg and categorized as having hypoxia if there was a single documented SpO2 < 90%.  The primary outcome of interest was survival to hospital discharge.

The association between mortality, hypotension and hypoxia was examined by logistic regression with adjustment for potential confounding variables including age, sex, race, ethnicity, payment source, trauma type and head region injury score.

Key Results:  

·      13,151 patients met study inclusion criteria.  11,545 (87.8%) had neither hypotension nor hypoxia, 604 (4.6%) had hypotension only, 790 (6.0%) had hypoxia only, and 212 (1.6%) had both hypotension and hypoxia.

·      Hypotension and hypoxia had additive effects on mortality.  Adjusted Odds Ratio (aOR) for death in each group was

• hypotension only: 2.49 (95% CI, 1.87-3.32)

• hypoxia only:  3.00 (95% CI, 4.20 – 8.86)

• both hypoxia and hypotension: 6.10 (4.20-8.86)

Conclusions: The combination of out-of-hospital hypotension and hypoxia is associated with more than doubling of the risk of death compared either alone following major traumatic brain injury.

What this Means for EMS: The prehospital phase of care, even though it may be brief, can have dramatic impact on patient survival following traumatic brain injury.  This suggests that anticipating and minimizing hypoxia and hypotension as part of a clinical bundle of care may have a dramatic impact on patient mortality, as was confirmed by the EPIC trial results. Incidence of hypoxia and hypotension should be tracked as quality measures for traumatic brain injury.

Article Summary by Maia Dorsett, MD PhD FAEMS, @maiadorsett

Article Bites #23: Applying the K.I.S.S. Principle to Trauma Triage.

Article: Kupas, D. F., Melnychuk, E. M., & Young, A. J. (2016). Glasgow coma scale motor component (“patient does not follow commands”) performs similarly to total glasgow coma scale in predicting severe injury in trauma patients. Annals of emergency medicine, 68(6), 744-750.

 Background: Trauma patients are often triaged to trauma centers based on their GCS.  Indeed, a GCS < 13 is one of the physiologic criteria within the CDC Field Trauma Triage Guidelines for transport to a trauma center.  However, when GCS is calculated by providers, there is a great deal of variability and inaccuracy. One proposed substitution is a simpler binary assessment of a GCS-motor (GCS-m) score < 6 (“patient does not follow commands”).  The objective of this study was to compare the total GCS score < 13 with a GCS-m<6 in predicting trauma-related outcomes.

Methods:  This was a retrospective study of prospectively-collected data over a four-year period (1999-2013) from the Pennsylvania Trauma System Foundation registry, which captures all patients with a trauma diagnosis who are admitted to state-accredited Level I, II, II or IV trauma centers.  Only patients age > 18 yo were included. 370,392 complete patient care encounters were included in the study. 

The out-of-hospital GCS score, out-of-hospital GCS-m score, and Injury Severity Score (ISS) were obtained for each patient. In addition, they collected CDC Field Trauma Triage Box 1 physiologic data including systolic blood pressure and respiratory rate.

 The primary outcome by which GCS was compared to GCS-m was an ISS>15, which is the established definition of a major trauma or polytrauma.  They also evaluated secondary outcomes including ISS > 24, death, ICU admission, need for craniotomy, any surgery, intubation, and a composite variable of “Trauma center need” which was defined as a ISS > 15, ICU admission 24 hrs or greater, need for surgery or death before discharge.   

The sensitivity and specificity of the two scores for both the primary outcome of major trauma and the secondary outcomes were compared using receiver operating curves. This was done both for all patients who had a GCS and GCS-m recorded, and also a secondary analysis which excluded patients who met CDC Field Trauma Triage criteria for trauma center need based on other physiologic parameters or documented injuries.   They defined a difference of < 5% in the area under the receiver operating characteristic curve as clinically unimportant.

 Key Results:  The differences between the GCS < 13 and GCS-m < 6 fell below the pre-specified 5% threshold for clinical importance for both analyses.

 Conclusions: The simpler decision point of “does not follow commands” is just as predictive of outcomes and trauma center need as the full GCS.

What this Means for EMS:  The physiologic trauma triage criteria should be simplified to incorporate the binary assessment of “not following commands” in place of calculating a full GCS.  Strongly consider transport of trauma patients who are not following commands directly to a trauma center.

Article Summary by Maia Dorsett, MD, PhD, FAEMS

Article Bites #22: Moving Beyond First Pass Success: A Clinical Bundle to Reduce the Incidence of Out-of-Hospital Peri-Intubation Hypoxia.

Article:  Jarvis, J. L., Gonzales, J., Johns, D., & Sager, L. (2018). Implementation of a clinical bundle to reduce out-of-hospital peri-intubation hypoxia. Annals of Emergency Medicine, 72(3), 272-279.

 Background:  Peri-intubation hypoxia is an important quality measure for EMS agencies performing rapid sequence intubation, as it is associated with poor patient outcomes including peri-intubation cardiac arrest and death and poor neurologic outcome following traumatic brain injury.  The aim of this study was to determine if implementation of a “clinical bundle encompassing positioning,  apneic oxygenation, delayed sequence intubation and goal-directed pre-oxygenation is associated with decreased peri-intubation hypoxia compared with standard out-of-hospital rapid sequence intubation.”

 Methods:  This was a retrospective before-and-after study utilizing data from Williamson County EMS in Texas.  Williamson County EMS is a suburban EMS system that staffs Paramedic-Paramedic, utilizes the King Vision video laryngoscope for intubation, has regular training in airway management and a baseline first pass intubation success rate of 85%. The study included all adult non-arrest patients requiring intubation.  The primary outcome of interest was the proportion of patients with peri-intubation hypoxia, defined as an oxygen saturation < 90% occurring at any time during intubation attempts.  

In the “before period”, the agency used standard rapid sequence intubation approach for non-cardiac arrest patients consisting of NRB, ketamine + paralytic, apneic oxygenation and intubation.  Following a training and implementation period, the agency implemented a clinical bundle consisting of the following components: ketamine administration (without paralytic), BVM+PEEP and NC oxygenation, patient positioning (head up/ear to sternal notch), minimum of 3 minutes of an SpO2 of > 93%, followed by paralytic administration and intubation.  If they were unable to achieve an acceptable pre-intubation SpO2, a supraglottic airway was inserted.  The clinical bundle required the second paramedic to act as an observer and timer.

Physiologic events were measured by manual review of monitor data, including continuous waveform capnography and pulse oximetry.  Patients were excluded from the analysis if they had incomplete pulse oximetry data or if in the after group, the clinical bundle was initiated but intubation was not attempted secondary to inability to meet pre-oxygenation goals (18/105 patients, 17%).

Key Results: The study included 104 patients in the before group and 87 patients in the after group. The before and after groups were not significantly different in terms of initial hypoxia (40.4% vs. 41.4%), first pass success (84.6% vs. 88.5%) or overall success (95.2% vs. 93.1%).  However, the rate of peri-intubation hypoxia dropped significantly (44.2% vs. 3.5%).  The median scene time increased by 9 minutes (95% CI 5.0 to 13.0 minutes) following bundle implementation. Even if you include the 17% of patients who were excluded for the “After” group for failure to meet pre-oxygenation goals, this represents a significant improvement.  There was no difference in incidence of peri-intubation cardiac arrest, but the study was not powered to detect a difference in this low frequency event.

 Conclusions: Implementation of a “clinical bundle emphasizing patient head positioning, apneic oxygenation, delayed sequence intubation, and goal-directed pre-oxygenation” has the ability to decrease the rate of peri-intubation hypoxia in non-cardiac arrest patients undergoing rapid sequence intubation.

What This Means for EMS: This study is an excellent potentially practice-changing study that blurs the lines between improvement science and research.  EMS providers, agency leadership, and medical oversight should be monitoring incidence of patient-oriented quality measures such as peri-intubation hypoxia to ensure quality of care of delivery.  Implementation of clinical care bundles and processes geared at improving performance on such measures have potential to greatly improve patient care.

Article Summary by Maia Dorsett, MD PhD FAEMS