Out-of-Hospital Intranasal Ketamine as an Adjunct to Fentanyl for the Treatment of Acute Traumatic Pain: A Randomized Clinical Trial.

STUDY OBJECTIVE: To evaluate if out-of-hospital administration of fentanyl and intranasal ketamine, compared to fentanyl alone, improves early pain control after injury. METHODS: We conducted an out-of-hospital randomized, placebo-controlled, blinded, parallel group clinical trial from October 2017 to December 2021. Participants were male, aged 18 to 65 years, receiving fentanyl to treat acute traumatic pain prior to hospital arrival, treated by an urban fire-based emergency medical services agency, and transported to the region's only adult Level I trauma center. Participants randomly received 50 mg intranasal ketamine or placebo. The primary outcome was the proportion with a minimum 2-point reduction in self-described pain on the verbal numerical rating scale 30 minutes after study drug administration assessed by 95% confidence interval overlap. Secondary outcomes were side effects, pain ratings, and additional pain medications through the first 3 hours of care. RESULTS: Among the 192 participants enrolled, 89 (46%) were White, (median age, 36 years; interquartile range, 27 to 53 years), with 103 receiving ketamine and 89 receiving placebo. There was no difference in the proportion experiencing improved pain 30 minutes after treatment (46/103 [44.7%] ketamine versus 32/89 [36.0%] placebo; difference in proportions, 8.7%; 95% confidence interval, -5.1% to 22.5%; P=.22) or at any time point through 3 hours. There was no difference in secondary outcomes or side effects. CONCLUSION: In our sample, we did not detect an analgesic benefit of adding 50 mg intranasal ketamine to fentanyl in out-of-hospital trauma patients.

Intra-arrest blood-based biomarkers for out-of-hospital cardiac arrest: A scoping review.

Objective: Blood-based biomarkers play a central role in the diagnosis and treatment of critically ill patients, yet none are routinely measured during the intra-arrest phase of out-of-hospital cardiac arrest (OHCA). Our objective was to describe methodological aspects, sources of evidence, and gaps in research surrounding intra-arrest blood-based biomarkers for OHCA. Methods: We used scoping review methodology to summarize existing literature. The protocol was designed a priori following the Preferred Reporting Items for Systematic Reviews and Meta-Analyses (PRISMA) Extension for Scoping Reviews. Inclusion criteria were peer-reviewed scientific studies on OHCA patients with at least one blood draw intra-arrest. We excluded in-hospital cardiac arrest and animal studies. There were no language, date, or study design exclusions. We conducted an electronic literature search using PubMed and Embase and hand-searched secondary literature. Data charting/synthesis were performed in duplicate using standardized data extraction templates. Results: The search strategy identified 11,834 records, with 118 studies evaluating 105 blood-based biomarkers included. Only eight studies (7%) had complete reporting. The median number of studies per biomarker was 2 (interquartile range 1-4). Most studies were conducted in Asia (63 studies, 53%).  Only 22 studies (19%) had blood samples collected in the prehospital setting, and only six studies (5%) had samples collected by paramedics. Pediatric patients were included in only three studies (3%). Out of eight predefined biomarker categories of use, only two were routinely assessed: prognostic (97/105, 92%) and diagnostic (61/105, 58%). Conclusions: Despite a large body of literature on intra-arrest blood-based biomarkers for OHCA, gaps in methodology and knowledge are widespread.

Prehospital Stroke Care Part 2: On-Scene Evaluation and Management by Emergency Medical Services Practitioners.

The prehospital phase is a critical component of delivering high-quality acute stroke care. This topical review discusses the current state of prehospital acute stroke screening and transport, as well as new and emerging advances in prehospital diagnosis and treatment of acute stroke. Topics include prehospital stroke screening, stroke severity screening, emerging technologies to aid in the identification and diagnosis of acute stroke in the prehospital setting, prenotification of receiving emergency departments, decision support for destination determination, and the capabilities and opportunities for prehospital stroke treatment in mobile stroke units. Further evidence-based guideline development and implementation of new technologies are critical for ongoing improvements in prehospital stroke care.

Ventilation rates measured by capnography during out-of-hospital cardiac arrest resuscitations and their association with return of spontaneous circulation.

BACKGROUND: Clinical guidelines for adult out-of-hospital cardiac arrest (OHCA) recommend a ventilation rate of 8-10 per minute yet acknowledge that few data exist to guide recommendations. The goal of this study was to evaluate the utility of continuous capnography to measure ventilation rates and the association with return of spontaneous circulation (ROSC). METHODS: This was a retrospective observational cohort study. We included all OHCA during a two-year period and excluded traumatic and pediatric patients. Ventilations were recorded using non-invasive continuous capnography. Blinded medically trained team members manually annotated all ventilations. Four techniques were used to analyze ventilation rate. The primary outcome was sustained prehospital ROSC. Secondary outcomes were vital status at the end of prehospital care and survival to hospital admission. Univariable and multivariable logistic regression models were constructed. RESULTS: A total of 790 OHCA were analyzed. Only 386 (49%) had useable capnography data. After applying inclusion and exclusion criteria, the final study cohort was 314 patients. The median ventilation rate per minute was 7 (IQR 5.4-8.5). Only 70 (22%) received a guideline-compliant ventilation rate of 8-10 per minute. Sixty-two (20%) achieved the primary outcome. No statistically significant associations were observed between any of the ventilation parameters and patient outcomes in both univariable and multivariable logistic regression models. CONCLUSIONS: We failed to detect an association between intra-arrest ventilation rates measured by continuous capnography and proximal patient outcomes after OHCA. Capnography has poor reliability as a measure of ventilation rate. Achieving guideline-compliant ventilation rates remains challenging.

Ketamine Stability over Six Months of Exposure to Moderate and High Temperature Environments.

Background: All medications should be stored within temperature ranges defined by manufacturers, but logistical and operational challenges of prehospital and military settings complicate adherence to these recommendations. Lorazepam and succinylcholine experience clinically relevant heat-related degradation, whereas midazolam does not. Because ketamine's stability when stored outside manufacturer recommendations is unknown, we evaluated the heat-related degradation of ketamine exposed to several temperature ranges. Methods: One hundred twenty vials of ketamine (50 mg/mL labeled concentration) from the same manufacturer lot were equally distributed and stored for six months in five environments: an active EMS unit in southwest Ohio (May-October 2019); heat chamber at constant 120 °F (C1); heat chamber fluctuating over 24 hours from 86 °F-120 °F (C2); heat chamber fluctuating over 24 hours from 40 °F-120 °F (C3); heat chamber kept at constant 70 °F (manufacturer recommended room temperature, C4). Four ketamine vials were removed every 30 days from each environment and sent to an FDA-accredited commercial lab for high performance liquid chromatography testing. Data loggers and thermistors allowed temperature recording every minute for all environments. Cumulative heat exposure was quantified by mean kinetic temperature (MKT), which accounts for additional heat-stress over time caused by temperature fluctuations and is a superior measure than simple ambient temperature. MKT was calculated for each environment at the time of ketamine removal. Descriptive statistics were used to describe the concentration changes at each time point. Results: The MKT ranged from 73.6 °F-80.7 °F in the active EMS unit and stayed constant for each chamber (C1 MKT: 120 °F, C2 MKT: 107.3 °F, C3 MKT: 96.5 °F, C4 MKT: 70 °F). No significant absolute ketamine degradation, or trends in degradation, occurred in any environment at any time point. The lowest median concentration occurred in the EMS-stored samples removed after 6 months [48.2 mg/mL (47.75, 48.35)], or 96.4% relative strength to labeled concentration. Conclusion: Ketamine samples exhibited limited degradation after 6 months of exposure to real world and simulated extreme high temperature environments exceeding manufacturer recommendations. Future studies are necessary to evaluate ketamine stability beyond 6 months.

Duration of exposure to a prehospital advanced airway and neurological outcome for out-of-hospital cardiac arrest: A retrospective cohort study.

BACKGROUND: Out-of-hospital cardiac arrest (OHCA) studies have focused on the benefits and harms of placing an intra-arrest advanced airway, but few studies have evaluated the benefits and harms after successful placement. We hypothesize that increased time in the tumultuous prehospital environment after intra-arrest advanced airway placement results in reduced patient survival. METHODS: This was a secondary analysis of adult, non-traumatic, OHCA patients with an advanced airway placed in the PRIMED trial. The exposure variable was the time interval between successful advanced airway placement and Emergency Department (ED) arrival. The outcome was cerebral performance category (CPC) 1 or 2 at hospital discharge. Multivariable logistic regression, adjusted for Utstein variables and resuscitation-associated time intervals, was used to estimate adjusted odds ratios (aOR). RESULTS: The cohort of complete cases included 4779 patients. The median time exposed to a prehospital advanced airway was 27 min (IQR 20-35). The total prehospital time was 39.4 min (IQR 32.3-48.1). An advanced airway was placed intra-arrest in 3830 cases (80.1%) and post-return of spontaneous circulation (post-ROSC) in 949 cases (19.9%). Overall, 486 (10.2%) of the cohort achieved the CPC outcome, but this was higher in the post-ROSC (21.7%) versus intra-arrest (7.5%) cohort. CPC was not associated with the time interval from advanced airway placement to ED arrival in the intra-arrest airway cohort (aOR 0.98, 95%CI 0.94-1.01). CONCLUSIONS: In OHCA patients who receive an intra-arrest advanced airway, longer time intervals exposed to a prehospital advanced airway are not associated with reduced patient survival.

Emergency Medical Services Traumatic Brain Injury Protocols Do Not Reflect Brain Trauma Foundation Guidelines.

OBJECTIVES: Implementation of traumatic brain injury (TBI) guideline recommendations for prehospital care is associated with improved outcomes, but prehospital guideline uptake is frequently delayed. Our objective was to estimate how well TBI guidelines are reflected in a national sample of prehospital TBI protocols in 2012 and 2018, 5 and 11 years after guideline publication. Methods: A purposeful sample of publicly accessible prehospital protocols were obtained in 2012, and updates of those protocols were obtained in 2018. Guideline recommendations were codified into a 23-item tool that was used to dual-abstract each prehospital protocol set. Descriptive statistics and chi-square testing were used to compare differences. Fifty-three sets of protocols representing 25 states and multiple administrative structures were identified. Results: None of the protocols contained all twenty-three elements of the guidelines, and more than one-third (19/53, 35%) did not have a TBI-specific protocol. While some individual items appeared more frequently in 2018 than 2012, more than half of the reviewed protocols do not contain guidance on ventilation or definitions of hypoxemia, hypotension, or pupil asymmetry. Conclusions: Evaluation of a diverse sample of EMS protocols demonstrates a significant deficit in the adoption of TBI guidelines more than a decade after publication.

The Cincinnati Prehospital Stroke Scale Compared to Stroke Severity Tools for Large Vessel Occlusion Stroke Prediction.

BACKGROUND: Various screening tools, ranging in complexity, have been developed to predict large vessel occlusion (LVO) stroke in the prehospital setting. Our objective was to determine whether newly-developed LVO stroke scales offer a clinically-meaningful advantage over the Cincinnati Prehospital Stroke Scale (CPSS). METHODS: We retrospectively analyzed prehospital patient care records linked with hospital data from 151 EMS agencies in the United States, between January 1, 2018 and December 31, 2018. We compared the CPSS to the Rapid Arterial Occlusion Evaluation (RACE), Los Angeles Motor Scale (LAMS), and the Vision, Aphasia, Neglect (VAN) assessment for LVO prediction. For each stroke scale, we used the intersection of sensitivity and specificity curves to determine optimal prediction cut-points. We used area under the ROC curve and 95% confidence intervals to assess for differences in discriminative ability between scales. RESULTS: We identified 13,596 prehospital records with one or more documented stroke scales of interest. Among these, 4,228 patients were diagnosed with stroke. Over half (57%, n = 2,415) of patients diagnosed with stroke experienced an acute ischemic stroke. Of patients with ischemic stroke, 26% (n = 628) were diagnosed with LVO. A CPSS score of 2 or higher demonstrated sensitivity = 69% and specificity = 78% for LVO. A RACE score of 4 or higher demonstrated sensitivity = 63%, specificity = 73%. A LAMS score of 3 or higher demonstrated sensitivity = 63%, specificity = 72% and a positive VAN score demonstrated sensitivity = 86%, specificity = 65%. Comparing the area under the ROC curve for each scale revealed no statistically significant differences in discriminative ability for LVO stroke. CONCLUSIONS: In this large sample of real-world prehospital patient encounters, the CPSS demonstrated similar predictive performance characteristics compared to the RACE, LAMS, and VAN for detecting LVO stroke. Prior to implementing a specific screening tool, EMS agencies should evaluate ease of use and associated implementation costs. Scored 0-3, the simple, widely-used CPSS may serve as a favorable prehospital screening instrument for LVO detection with a cut-point of 2 or higher maximizing the tradeoff between sensitivity and specificity.

Mechanical Ventilation of Severe Traumatic Brain Injury Patients in the Prehospital Setting.

OBJECTIVE: Suboptimal ventilation may impact outcomes in patients with traumatic brain injury (TBI). This study compares the incidence of eucapnia between manually and mechanically ventilated patients with severe TBI during helicopter transport. METHODS: This retrospective chart review included consecutive intubated adults with severe TBI (Glasgow Coma Scale score < 9) transported by helicopter from the scene of injury to a level 1 trauma center between 2009 and 2015. The primary outcome was the first venous partial pressure of carbon dioxide obtained in the emergency department. Hypocapnia, eucapnia, and hypercapnia were defined based on the normal range for the testing instrument. The Fisher exact test was used to compare groups. RESULTS: Of 1,070 trauma patients intubated and transported, 93 met the inclusion criteria with full data. The mean age was 43 years, 81 of 93 were white, and 70 of 93 were men. The mean Injury Severity Score was 29, and 26 of 93 were mechanically ventilated. Hypocapnia occurred in 4 of 93 and hypercapnia in 56 of 93. There was no difference in the rate of eucapnia in manually ventilated compared with mechanically ventilated patients (36% vs. 35%, P = 1.00). CONCLUSION: Eucapnia at emergency department arrival occurred in 36% of patients and was unaffected by whether ventilation was manually or mechanically controlled. Few patients were hypocapnic, indicating a low incidence of hyperventilation during helicopter transport.

Predictors of Definitive Airway Sans Hypoxia/Hypotension on First Attempt (DASH-1A) Success in Traumatically Injured Patients Undergoing Prehospital Intubation.

Background: Prehospital intubation success is routinely treated as a dichotomous outcome based on an endotracheal tube passing through vocal cords regardless of number of attempts or occurrence of hypoxia, or hypotension, which are associated with worse outcomes. We explore patient, provider, and procedure-related variables associated with successful definitive airway sans hypoxia/hypotension on first attempt (DASH-1A) in traumatically injured subjects undergoing endotracheal intubation at the scene of injury by a helicopter EMS system.Methods: This single-center retrospective chart review included patients with traumatic injuries and at least one attempted intubation by helicopter EMS at the scene of injury. Demographic and clinical variables were tested for association with DASH-1A and overall first-attempt success using univariate comparisons and multivariable logistic regression to produce adjusted odds ratios (aORs) and 95% confidence intervals (CIs). Purposeful backwards stepwise elimination was used to develop logistic regression models for outcomes. Initial inclusion of covariates in multivariable models was based on clinical judgement, known or suspected risk factors and confounders for intubation success, and univariate associations.Results: Of 419 subjects screened, 263 met inclusion criteria. Median age was 34 years and the majority of subjects were Caucasian (95%), male (76%), and suffered blunt trauma (90%). The endotracheal tube was successfully placed on the first attempt in 198 (75.3%) of patients, but only 142 (55.3%) had a successful DASH-1A, and overall, 246 (94%) had an endotracheal tube passed successfully before hospital arrival. Factors significantly associated with successful DASH-1A were no ground EMS intubation attempt prior to arrival [aOR 2.2 (CI 1.0-4.9)], lack of airway secretions/blood [1.9 (1.0-3.4)], Cormack-Lehane Score of I and II [12.3 (4.5-33.2) & 3.2 (1.2-9.1), respectively], and bougie use [5.4 (1.8-15.8)]. For endotracheal tube passing only, the following were significantly associated with first pass success: grade of view I and II [aORs 87.3 (CI 25.8-295.7) & 6.8 (2.3-19.5), respectively], lack of secretions/blood [4.9 (2.1-11.2), bougie use [7.8 (2.3-26.3)], direct laryngoscopy [5.1 (1.5-17.0)] and not using apneic oxygenation through a nasal cannula [2.5 (1.1-5.6)].Conclusion: In our helicopter EMS system, successful endotracheal intubation on the first attempt and without an episode of hypoxia was associated with no ground EMS intubation attempt prior to flight crew arrival, lack of airway secretions/blood, Cormack-Lehane Score, and bougie use.

Potential Impact of C-STAT for Prehospital Stroke Triage up to 24 Hours on a Regional Stroke System.

Background and Purpose: Thrombectomy for large vessel occlusion acute ischemic stroke (AIS-LVO) may benefit patients up to 24 hour since last known normal (LKN). Prehospital tools, like the Cincinnati Stroke Triage Assessment Tool (C-STAT), are used to select hospital destination for suspected AIS-LVO patients. The objective of this study was to estimate the potential impact of the expanded thrombectomy time window on suspected AIS-LVO cases transported to the regional comprehensive stroke center (CSC). Methods: From June to November 2015, C-STAT was performed by prehospital providers following a positive prehospital Cincinnati Prehospital Stroke Scale (CPSS) stroke screen in suspected stroke/TIA patients. There was no preferential triage based on C-STAT results. Final diagnoses, including the presence of AIS-LVO was ascertained via medical record review. Impact of positive C-STAT cases on CSC volumes was estimated for up to 24 hours since LKN. Results: Of 158 patients with prehospital suspicion for stroke/TIA, 105 were CPSS positive within 24 hours of onset and had complete C-STAT and clinical data available for analysis. Forty-six percent (17/37) of C-STAT + were non-strokes. C-STAT sensitivity and specificity for LVO were 71% (95% CI 36-92) and 67% (95% CI 58-80), respectively. C-STAT triage would increase transport of prehospital suspected stroke cases to the CSC by 11% (12/105) within six hours and 21% (22/105) within 24 hours. Of 37 C-STAT + patients, only 5 (13.5%) had LVO as final diagnosis. Conclusions: Preferential triage of prehospital suspected stroke patients using C-STAT would increase the number of patients transported to the CSC by 11% within six hours and an additional 10% from six to 24 hours. For every patient with LVO as final diagnosis, approximately an additional 6 non-LVO patients would be triaged to a CSC.

The Impact of Video Laryngoscopy on the Clinical Learning Environment of Emergency Medicine Residents: A Report of 14,313 Intubations.

BACKGROUND: The introduction of video laryngoscopy (VL) may impact emergency medicine (EM) residents' intubation practices. METHODS: We analyzed 14,313 intubations from 11 EM training sites, July 1, 2002, to December 31, 2012, assessing the likelihood of first-attempt success and likelihood of having a second attempt, by rank and device. We determined whether direct laryngoscopy (DL) first-attempt success decreased as VL became more prevalent using a logistic regression model with proportion of encounters initiated with VL at that center in the prior 90 and 365 days as predictors of DL first-attempt success. RESULTS: First-attempt success by PGY-1s was 71% (95% confidence interval [CI] = 63% to 78%); PGY-2s, 82% (95% CI = 78% to 86%); and PGY-3+, 89% (95% CI = 85% to 92%). Residents' first-attempt success rate was higher with the C-MAC video laryngoscope (C-MAC) versus DL, 92% versus 84% (risk difference [RD] = 8%, 95% CI = 4% to 11%), but there was no statistical difference between the GlideScope video laryngoscope (GVL) and DL, 80% versus 84% (RD = -4%, 95% CI = -10% to 1%). PGY-1s were more likely to have a second intubation attempt after first-attempt failure with VL versus DL: 32% versus 18% (RD = 14%, 95% CI = 5% to 23%). DL first-attempt success rates did not decrease as VL became more prevalent. CONCLUSIONS: First-attempt success increases with training. Interns are more likely to have a second attempt when using VL. The C-MAC may be associated with increased first-attempt success for EM residents compared with DL or GVL. The increasing prevalence of VL is not accompanied by a decrease in DL success.

Timing of Advanced Airway Placement after Witnessed Out-of-Hospital Cardiac Arrest.

Background: Advanced airways (endotracheal tubes, supraglottic airways) are frequently placed by Emergency Medical Services (EMS) in patients with out-of-hospital cardiac arrest (OHCA). However, if an airway is to be placed, it is unknown whether this should occur early or late in the sequence of resuscitation events. This study evaluated the association between the timing of airway placement and the minute-to-minute probability of achieving return of spontaneous circulation (ROSC). Methods: This secondary analysis of Resuscitation Outcomes Consortium Prehospital Resuscitation using an Impedance Valve and Early versus Delayed (ROC PRIMED) study data included adult, non-traumatic, witnessed OHCA patients with airway placement by EMS before ROSC. The primary exposure variable was time from EMS arrival to advanced airway placement. The outcome was prehospital ROSC. Since resuscitations occur over time, a Cox proportional hazards model was fit to estimate the probability of ROSC as a function of the airway timing, adjusting for Utstein variables. Results: A total of 7,547 patients were included. Time to airway placement was 0-5 minutes in 12% of the cohort, >5-10 (36%), >10-15 (29%), >15-20 (14%), >20-25 (5%), >25-30 (2%), and >30 (2%). ROSC occurred in 43%. Time to airway had a statistically significant impact on ROSC. A negative association between the time to airway placement and the hazard of ROSC was observed, such that increasing intervals between EMS arrival and airway placement were associated with decreasing probabilities of ROSC, regardless of initial cardiac rhythm. Conclusions: EMS advanced airway placement has a time-dependent association with ROSC. In witnessed OHCA patients receiving advanced airways, early airway placement is associated with increased probability of ROSC.

Prehospital Prediction of Large Vessel Occlusion in Suspected Stroke Patients.

PURPOSE OF REVIEW: Recent advances in endovascular thrombectomy have made acute ischemic stroke due to a large vessel occlusion more treatable than ever. Rapid access to treatment remains paramount and multiple large vessel occlusion prediction scales have been created to enhance prehospital identification and triage of these patients. This review summarizes the current state of large vessel occlusion prediction scales, proposes a set of ideal scale features, and discusses the future of these scales and prehospital neurological emergency response systems. RECENT FINDINGS: A meta-analysis of the available data concluded that none of the currently published scales are more accurate than the others. However, other studies provide insight into important qualitative features beyond accuracy. At present, only a few large vessel occlusion prediction scales have been studied in the necessary prehospital suspected stroke patient population. Among these small studies, 26-51% of patients identified by scales had large vessel occlusions and 63-84% qualified for triage to a Comprehensive Stroke Center. Valuable scale features include binary scoring, inclusion of gaze deviation and arm weakness, exclusion of neglect, and prehospital validation in a suspected stroke cohort. Patients with neurological emergencies that mimic large vessel occlusion, such as intracranial hemorrhage, may also benefit from triage to Comprehensive Stroke Centers. Prehospital triage is more complex than ever and guidelines, tools, and systems continue to evolve.

Prehospital Triage of Acute Ischemic Stroke Patients to an Intravenous tPA-Ready versus Endovascular-Ready Hospital: A Decision Analysis.

BACKGROUND: American Stroke Association guidelines for prehospital acute ischemic stroke recommend against bypassing an intravenous tPA-ready hospital (IRH), if additional transportation time to an endovascular-ready hospital (ERH) exceeds 15-20 min. However, it is unknown when the benefit of potential endovascular therapy at an ERH outweighs the harm from delaying intravenous therapy at a closer IRH, especially since large vessel occlusion (LVO) status is initially unknown. We hypothesized that current time recommendations for IRH bypass are too short to achieve optimal outcomes for certain patient populations. METHODS: A decision analysis model was constructed using population-based databases, a detailed literature review, and interventional trial data containing time-dependent modified Rankin Scale distributions. The base case was triaged by Emergency Medical Services (EMS) 110 min after stroke onset and had a 23.6% LVO rate. Base case triage choices were (1) transport to the closest IRH (12 min), (2) transport to the ERH (60 min) bypassing the IRH, or (3) apply the Cincinnati Stroke Triage Assessment Tool and transport to the ERH if positive for LVO. Outcomes were assessed using quality-adjusted life years (QALYs). Sensitivity analyses were performed for all major variables, and alternative prehospital stroke scales were assessed. RESULTS: In the base case, transport to the IRH was the optimal choice with an expected outcome of 8.47 QALYs. Sensitivity analyses demonstrated that transport to the ERH was superior until bypass time exceeded 44 additional minutes, or when the onset to EMS triage interval exceeded 99 min. As the probability of LVO increased, ERH transport was optimal at longer onset to EMS triage intervals. The optimal triage strategy was highly dependent on specific interactions between the IRH transportation time, ERH transportation time, and onset to EMS triage interval. CONCLUSIONS: No single time difference between IRH and ERH transportation optimizes triage for all patients. Allowable IRH bypass time should be increased and acute ischemic stroke guidelines should incorporate the onset to EMS triage interval, IRH transportation time, and ERH transportation time.