Whole Blood Resuscitation and Association with Survival in Injured Patients with an Elevated Probability of Mortality.

BACKGROUND: Low-titer group O whole blood (LTOWB) resuscitation is becoming common in both military and civilian settings and may represent the ideal resuscitation intervention. We sought to characterize the safety and efficacy of LTOWB resuscitation relative to blood component resuscitation. STUDY DESIGN: A prospective, multicenter, observational cohort study was performed using 7 trauma centers. Injured patients at risk of massive transfusion who required both blood transfusion and hemorrhage control procedures were enrolled. The primary outcome was 4-hour mortality. Secondary outcomes included 24-hour and 28-day mortality, achievement of hemostasis, death from exsanguination, and the incidence of unexpected survivors. RESULTS: A total of 1,051 patients in hemorrhagic shock met all enrollment criteria. The cohort was severely injured with >70% of patients requiring massive transfusion. After propensity adjustment, no significant 4-hour mortality difference across LTOWB and component patients was found (relative risk [RR] 0.90, 95% CI 0.59 to 1.39, p = 0.64). Similarly, no adjusted mortality differences were demonstrated at 24 hours or 28 days for the enrolled cohort. When patients with an elevated prehospital probability of mortality were analyzed, LTOWB resuscitation was independently associated with a 48% lower risk of 4-hour mortality (relative risk [RR] 0.52, 95% CI 0.32 to 0.87, p = 0.01) and a 30% lower risk of 28-day mortality (RR 0.70, 95% CI 0.51 to 0.96, p = 0.03). CONCLUSIONS: Early LTOWB resuscitation is safe but not independently associated with survival for the overall enrolled population. When patients were selected with an elevated probability of mortality based on prehospital injury characteristics, LTOWB was independently associated with a lower risk of mortality starting at 4 hours after arrival through 28 days after injury.

Optimal Prehospital Crystalloid Resuscitation Volume in Trauma Patients at Risk for Hemorrhagic Shock.

BACKGROUND: Prehospital resuscitation guidelines vary widely, and blood products, although likely superior, are not available for most patients in the prehospital setting. Our objective was to determine the prehospital crystalloid volume associated with the lowest mortality among patients in hemorrhagic shock. STUDY DESIGN: This is a secondary analysis of the Prehospital Air Medical Plasma trial. Injured patients from the scene with hypotension and tachycardia or severe hypotension were included. Segmented regression and generalized additive models were used to evaluate nonlinear effects of prehospital crystalloid volume on 24-hour mortality. Logistic regression evaluated the association between risk-adjusted mortality and prehospital crystalloid volume ranges to identify optimal target volumes. Inverse propensity weighting was performed to account for patient heterogeneity. RESULTS: There were 405 patients included. Segmented regression suggested the nadir of 24-hour mortality lay within 377 to 1,419 mL prehospital crystalloid. Generalized additive models suggested the nadir of 24-hour mortality lay within 242 to 1,333 mL prehospital crystalloid. A clinically operationalized range of 250 to 1,250 mL was selected based on these findings. Odds of 24-hour mortality were higher for patients receiving less than 250 mL (adjusted odds ratio [aOR] 2.46; 95% CI 1.31 to 4.83; p = 0.007) and greater than 1,250 mL (aOR 2.57; 95% CI 1.24 to 5.45; p = 0.012) compared with 250 to 1,250 mL. Propensity-weighted regression similarly demonstrated odds of 24-hour mortality were higher for patients receiving less than 250 mL (aOR 2.62; 95% CI 1.34 to 5.12; p = 0.005) and greater than 1,250 mL (aOR 2.93; 95% CI 1.36 to 6.29; p = 0.006) compared with 250 to 1,250 mL. CONCLUSIONS: Prehospital crystalloid volumes between 250 and 1,250 mL are associated with lower mortality compared with lower or higher volumes. Further work to validate these finding may provide practical volume targets for prehospital crystalloid resuscitation.

Prehospital low titer group O whole blood is feasible and safe: Results of a prospective randomized pilot trial.

INTRODUCTION: Low titer group O whole blood (LTOWB) resuscitation is increasingly common in both military and civilian settings. Data regarding the safety and efficacy of prehospital LTOWB remain limited. METHODS: We performed a single-center, prospective, cluster randomized, prehospital through in-hospital whole blood pilot trial for injured air medical patients. We compared standard prehospital air medical care including red cell transfusion and crystalloids followed by in-hospital component transfusion to prehospital and in-hospital LTOWB resuscitation. Prehospital vital signs were used as inclusion criteria (systolic blood pressure ≤90 mm Hg and heart rate ≥108 beats per minute or systolic blood pressure ≤70 mm Hg for patients at risk of hemorrhage). Primary outcome was feasibility. Secondary outcomes included 28-day and 24-hour mortality, multiple organ failure, nosocomial infection, 24-hour transfusion requirements, and arrival coagulation parameters. RESULTS: Between November 2018 and October 2020, 86 injured patients were cluster randomized by helicopter base. The trial has halted early at 77% enrollment. Overall, 28-day mortality for the cohort was 26%. Injured patients randomized to prehospital LTOWB (n = 40) relative to standard care (n = 46) were similar in demographics and injury characteristics. Intent-to-treat Kaplan-Meier survival analysis demonstrated no statistical mortality benefit at 28 days (25.0% vs. 26.1%, p = 0.85). Patients randomized to prehospital LTOWB relative to standard care had lower red cell transfusion requirements at 24 hours (p < 0.01) and a lower incidence of abnormal thromboelastographic measurements. No transfusion reactions during the prehospital or in-hospital phase of care were documented. CONCLUSION: Prehospital through in-hospital LTOWB resuscitation is safe and may be associated with hemostatic benefits. A large-scale clinical trial is feasible with protocol adjustment and would allow the effects of prehospital LTOWB on survival and other pertinent clinical outcomes to be appropriately characterized. LEVEL OF EVIDENCE: Therapeutic/Care Management, Level II.

Multimodal Long-Term Predictors of Outcome in Out of Hospital Cardiac Arrest Patients Treated with Targeted Temperature Management at 36 °C.

Introduction: Early prediction of long-term outcomes in patients resuscitated after cardiac arrest (CA) is still challenging. Guidelines suggested a multimodal approach combining multiple predictors. We evaluated whether the combination of the electroencephalography (EEG) reactivity, somatosensory evoked potentials (SSEPs) cortical complex and Gray to White matter ratio (GWR) on brain computed tomography (CT) at different temperatures could predict survival and good outcome at hospital discharge and six months after the event. Methods: We performed a retrospective cohort study including consecutive adult, non-traumatic patients resuscitated from out-of-hospital CA who remained comatose on admission to our intensive care unit from 2013 to 2017. We acquired SSEPs and EEGs during the treatment at 36 °C and after rewarming at 37 °C, Gray to white matter ratio (GWR) was calculated on the brain computed tomography scan performed within six hours of the hospital admission. We primarily hypothesized that SSEP was associated with favor-able functional outcome at distance and secondarily that SSEP provides independent information from EEG and CT. Outcomes were evaluated using the Cerebral Performance Category (CPC) scale at six months from discharge. Results: Of 171 resuscitated patients, 75 were excluded due to missing data or uninterpretable neurophysiological findings. EEG reactivity at 37 °C has been shown the best single predictor of good out-come (AUC 0.803) while N20P25 was the best single predictor for survival at each time point. (AUC 0.775 at discharge and AUC 0.747 at six months follow up). The predictive value of a model including EEG reactivity, average GWR, and SSEP N20P25 amplitude was superior (AUC 0.841 for survival and 0.920 for good out-come) to any combination of two tests or any single test. Conclusions: Our study, in which life-sustaining treatments were never suspended, suggests SSEP cortical complex N20P25, after normothermia and off sedation, is a reliable predictor for survival at any time. When SSEP cortical complex N20P25 is added into a model with GWR average and EEG reactivity, the predictivity for good outcome and survival at distance is superior than each single test alone.

Massive transfusion and the response to prehospital plasma: It is all in how you define it.

BACKGROUND: A recent analysis derived from the Prehospital Air Medical Plasma trial data set demonstrated no significant independent plasma survival benefit in those who required massive transfusion (≥10 units of red cells in 24 hours). The definition of massive transfusion has evolved over time to minimize bias and predict those at highest risk of death. We sought to characterize the definition of massive transfusion, their associated mortality risks and the survival benefit associated with prehospital plasma. METHODS: A secondary analysis was performed using data from a recent prehospital plasma trial. Patients transferred directly from the scene were characterized. We defined historic massive transfusion using ≥10 units red cells in 24 hours and critical administration threshold (CAT) as ≥3 units per hour in the first hour (CAT1hr) or in any of the first 4 hours (CAT4hr) from arrival. The primary outcome was 30-day mortality. Kaplan-Meier analysis and Cox hazard regression were used to characterize the survival benefit of prehospital plasma. RESULTS: There were a total of 390 enrolled patients who were transferred from the scene and represent the study cohort. Overall, 126 patients were positive for the CAT1hr metric, 183 patients were positive for the CAT4hr metric and 84 patients were positive for historic massive transfusion metric. The overall study mortality rate for those patients who met each transfusion definition was 13.1%, 17.4% and 10.0%, respectively. The CAT4hr metric had the lowest potential for survival bias. Kaplan-Meier survival analysis demonstrated a prehospital plasma survival benefit in the patients who were CAT4hr positive. CONCLUSION: The current analysis demonstrates the superior utility of the CAT4hr definition with optimization of survival bias while conserving mortality risk prediction. This transfusion definition was associated with a prehospital plasma survival benefit and may be the most appropriate definition of massive transfusion for pragmatic studies which focus on hemorrhagic shock. LEVEL OF EVIDENCE: Epidemiologic, Level II.

Prehospital plasma in injured patients is associated with survival principally in blunt injury: Results from two randomized prehospital plasma trials.

INTRODUCTION: Recent evidence demonstrated that prehospital plasma in patients at risk of hemorrhagic shock was safe for ground transport and resulted in a 28-day survival benefit for air medical transport patients. Whether any beneficial effect of prehospital plasma varies across injury mechanism remains unknown. METHODS: We performed a secondary analysis using a harmonized data set derived from two recent prehospital plasma randomized trials. Identical inclusion/exclusion criteria and primary/secondary outcomes were used for the trials. Prehospital time, arrival shock parameters, and 24-hour transfusion requirements were compared across plasma and control groups stratified by mechanism of injury. Stratified survival analysis and Cox hazard regression were performed to determine the independent survival benefits of plasma across blunt and penetrating injury. RESULTS: Blunt patients had higher injury severity, were older, and had a lower Glasgow Coma Scale. Arrival indices of shock and coagulation parameters were similar across blunt and penetrating injury. The percentage of patients with a prehospital time less than 20 minutes was significantly higher for penetrating patients relative to blunt injured patients (28.0% vs. 11.6%, p < 0.01). Stratified Kaplan-Meier curves demonstrated a significant separation for blunt injured patients (n = 465, p = 0.01) with no separation demonstrated for penetrating injured patients (n = 161, p = 0.60) Stratified Cox hazard regression verified, after controlling for all important confounders, that prehospital plasma was associated with a 32% lower independent hazard for 28-day mortality in blunt injured patients (hazard ratio, 0.68; 95% confidence interval, 0.47-0.96; p = 0.03) with no independent survival benefit found in penetrating patients (hazard ratio, 1.16; 95% confidence interval, 0.4-3.1; p = 0.78). CONCLUSION: A survival benefit associated with prehospital plasma at 24 hours and 28 days exists primarily in blunt injured patients with no benefit shown in penetrating trauma patients. No detrimental effects attributable to plasma are demonstrated in penetrating injury. These results have important relevance to military and civilian trauma systems. LEVEL OF EVIDENCE: Therapeutic, I.

Challenges in the development and implementation of a healthcare system based extracorporeal cardiopulmonary resuscitation (ECPR) program for the treatment of out of hospital cardiac arrest.

INTRODUCTION: Extracorporeal cardiopulmonary resuscitation (ECPR) can treat cardiac arrest refractory to conventional therapies. Many institutions are interested in developing their own ECPR program. However, there may be challenges in logistics and implementation. AIMS: The aim of our protocol was to demonstrate that an ECPR team was feasible within our healthcare system and that the identification of UPMC Presbyterian as a receiving center allowed for successful treatment within 30 min from EMS dispatch. METHODS: We developed out of hospital cardiac arrest (OHCA) ECPR protocols for Emergency Medical Services (EMS), EMS communications, and our in-hospital ECPR team. Inclusion criteria indentified patients with a potentially reversible arrest etiology and high probability of recoverable brain injury using a simple checklist: witnessed collapse, layperson CPR, initial shockable rhythm, and age 18-60 years. We trained local EMS crews to screen patients and reviewed the criteria with a Medic Command Physician prior to transport to our hospital. RESULTS: From October 2015 to March 31st 2018, EMS treated 1165 EMS OHCA cases, transported 664 (57%) to a local hospital, and transported 120 (10%) to our institution. Of these, five (4.1%) patients underwent ECPR. Among excluded cases, 64 (53%) had nonshockable rhythms, 48 (40%) were unwitnessed arrests, 50 (42%) were over age 60 and the remaining 20 (17%) had no documented reasons for exclusion. For ECPR cases, median pre-hospital CPR duration was 26 [IQR 25-40] min. Four patients (80%) received mechanical CPR. Interval from arrest to arrival on scene was 5 [IQR 4-6] min and interval from radio call to activation of ECPR was 13 [IQR 7-21] min. Interval from EMS dispatch to departure from scene was 20 [IQR 19-21] min. Time from EMS dispatch to initiation of ECPR was 63 [IQR 59-69] min. CONCLUSIONS: ECPR is an infrequent occurrence in EMS practice. Most apparently eligible patients did not get ECPR, highlighting the need for ongoing programmatic development, provider education, and qualitative work exploring barriers to implementation.

Severity of hemorrhage and the survival benefit associated with plasma: Results from a randomized prehospital plasma trial.

BACKGROUND: Recent randomized clinical trial evidence demonstrated a survival benefit with the use of prehospital plasma in patients at risk of hemorrhagic shock. We sought to characterize the survival benefit associated with prehospital plasma relative to the blood transfusion volume over the initial 24 hours. We hypothesized that the beneficial effects of prehospital plasma would be most robust in those with higher severity of hemorrhage. METHODS: We performed a prespecified secondary analysis using data derived from a prospective randomized prehospital plasma trial. Blood component transfusion volumes were recorded over the initial 24 hours. Massive transfusion (MT) was defined a priori as receiving ≥10 units of red cells in 24 hours. We characterized the 30-day survival benefit of prehospital plasma and the need for MT and overall 24-hour red cell transfusion volume utilizing Kaplan-Meier survival analysis and Cox proportional hazard regression. RESULTS: There were 501 patients included in this analysis with 230 randomized to prehospital plasma with 104 patients requiring MT. Mortality in patients who received MT were higher compared with those that did not (MT vs. NO-MT, 42% vs. 26%, p = 0.001). Kaplan-Meier survival curves demonstrated early separation in the NO-MT subgroup (log rank p = 0.008) with no survival benefit found in the MT group (log rank p = 0.949). Cox regression analysis verified these findings. When 24-hour red cell transfusion was divided into quartiles, there was a significant independent association with 30-day survival in patients who received 4 to 7 units (hazard ratio, 0.33, 95% confidence interval, 0.14-0.80, p = 0.013). CONCLUSION: The survival benefits of prehospital plasma was demonstrated only in patients with red cell requirements below the transfusion level of MT. Patients who received 4 to 7 units of red cells demonstrated the most robust independent survival benefit attributable to prehospital plasma transfusion. Prehospital plasma may be most beneficial in those patients with moderate transfusion requirements and mortality risk. LEVEL OF EVIDENCE: Therapeutic, Level I.

Implementation of a prehospital air medical thawed plasma program: Is it even feasible?

BACKGROUND: The Prehospital Air Medical Plasma (PAMPer) trial demonstrated a 30-day survival benefit among hypotensive trauma patients treated with prehospital plasma during air medical transport. We characterized resources, costs and feasibility of air medical prehospital plasma program implementation. METHODS: We performed a secondary analysis using data derived from the recent PAMPer trial. Intervention patients received thawed plasma (5-day shelf life). Unused plasma units were recycled back to blood bank affiliates, when possible. Distribution method and capability of recycling varied across sites. We determined the status of plasma units deployed, utilized, wasted, and returned. We inventoried thawed plasma use and annualized costs for distribution and recovery. RESULTS: The PAMPer trial screened 7,275 patients and 5,103 plasma units were deployed across 22 air medical bases during a 42-month period. Only 368 (7.2%) units of this total thawed plasma pool were provided to plasma randomized PAMPer patients. Of the total plasma pool, 3,716 (72.8%) units of plasma were returned to the blood bank with the potential for transfusion prior to expiration and 1,019 (20.0%) thawed plasma units were deemed wasted for this analysis. The estimated average annual cost of implementation of a thawed plasma program per air medical base at an average courier distance would be between US $24,343 and US $30,077, depending on the ability to recycle plasma and distance of courier delivery required. CONCLUSION: A prehospital plasma program utilizing thawed plasma is resource intensive. Plasma waste can be minimized depending on trauma center and blood bank specific logistics. Implementation of a thawed plasma program can occur with financial cost. Products with a longer shelf life, such as liquid plasma or freeze-dried plasma, may provide a more cost-effective prehospital product relative to thawed plasma. LEVEL OF EVIDENCE: Therapeutic, level III.

Impact of shift duration on alertness among air-medical emergency care clinician shift workers.

BACKGROUND: Greater than half of Emergency Medical Services (EMS) shift workers report fatigue at work and most work long duration shifts. We sought to compare the alertness level of EMS shift workers by shift duration. METHODS: We used a multi-site, 14-day prospective observational cohort study design of EMS clinician shift workers at four air-medical EMS organizations. The primary outcome was behavioral alertness as measured by psychomotor vigilance tests (PVT) at the start and end of shifts. We stratified shifts by duration (< 24 h and 24 h), night versus day, and examined the impact of intra-shift napping on PVT performance. RESULTS: One hundred and twelve individuals participated. The distribution of shifts <24 h and 24 h with complete data were 54% and 46%, respectively. We detected no differences in PVT performance measures stratified by shift duration (P > 0.05). Performance for selected PVT measures (lapses and false starts) was worse on night shifts compared to day shifts (P < 0.05). Performance also worsened with decreasing time between waking from a nap and the end of shift PVT assessment. CONCLUSIONS: Deficits in performance in the air-medical setting may be greatest during night shifts and proximal to waking from an intra-shift nap. Future research should examine alertness and performance throughout air-medical shifts, as well as investigate the timing and duration of intra-shift naps on outcomes.

Fatigue mitigation with SleepTrackTXT2 in air medical emergency care systems: study protocol for a randomized controlled trial.

BACKGROUND: Most air medical Emergency Medical Services (EMS) clinicians work extended duration shifts, and more than 50% report inadequate sleep, poor sleep quality, and/or poor recovery between shifts. The SleepTrackTXT pilot trial (ClinicalTrials.gov, NCT02063737) showed that use of mobile phone text messages could impact EMS clinician self-reported fatigue and sleepiness during long duration shifts. The purpose of the SleepTrackTXT2 trial is to leverage lessons learned from the first SleepTrackTXT study and test an enhanced intervention targeting air medical EMS clinicians. METHODS/DESIGN: We will conduct a multi-site randomized trial with a sample of adult EMS clinicians recruited from four air medical EMS systems located in the midwest, northeastern, and southern USA. Participants will be allocated to one of two possible arms for a 4-month (120-day) study period. The intervention arm will involve text-message assessments of sleepiness, fatigue, and difficulty concentrating at the beginning, every 4 hours during, and at the end of scheduled shifts. Participants reporting high levels of sleepiness, fatigue, or difficulty with concentration will receive one of nine randomly selected intervention messages to promote behavior change during shift work to improve alertness. Intervention participants will receive a text-message report on Friday of each week that shows their sleep debt over the previous 7 days followed by a text message to promote paying back sleep debt recovery when feasible. Participants in the control group receive text messages that only include assessments. Both arms will receive text-message assessments of perceived recovery since last shift, sleepiness, fatigue, or difficulty with concentration at noon (1200 hours) on days between scheduled shifts (off-duty days). We have two aims for this study: (1) to determine the short-term impact of the enhanced SleepTrackTXT2 intervention on air medical clinician fatigue reported in real time during and at the end of shift work, and (2) to determine the long-term impact of the SleepTrackTXT2 intervention on sleep quality and sleep health indicators including hours of sleep and recovery between shift work. DISCUSSION: The SleepTrackTXT2 trial may provide evidence of real-world effectiveness that would support widespread expansion of fatigue mitigation interventions in emergency care clinician shift workers. The trial may specifically support use of real-time assessments and interventions delivered via mobile technology such as text messaging. TRIAL REGISTRATION: ClinicalTrials.gov, NCT02783027 . Registered on 23 May 2016.

Biochemical signaling by remote ischemic conditioning of the arm versus thigh: Is one raise of the cuff enough?

Remote Ischemic Conditioning (RIC), induced by brief cycles of ischemia and reperfusion, protects vital organs from a prolonged ischemic insult. While several biochemical mediators have been implicated in RIC's mechanism of action, it remains unclear whether the localization or "dose" of RIC affects the extent of protective signaling. In this randomized crossover study of healthy individuals, we tested whether the number of cycles of RIC and its localization (arm versus thigh) determines biochemical signaling and cytoprotection. Subjects received either arm or thigh RIC and then were crossed over to receive RIC in the other extremity. Blood flow, tissue perfusion, concentrations of the circulating protective mediator nitrite, and platelet mitochondrial function were measured after each RIC cycle. We found that plasma nitrite concentration peaked after the first RIC cycle and remained elevated throughout RIC. This plasma nitrite conferred cytoprotection in an in vitro myocyte model of hypoxia/reoxygenation. Notably, though plasma nitrite returned to baseline at 24h, RIC conditioned plasma still mediated protection. Additionally, no difference in endpoints between RIC in thigh versus arm was found. These data demonstrate that localization and "dose" of RIC does not affect cytoprotection and further elucidate the mechanisms by which nitrite contributes to RIC-dependent protection.

A Geospatial Analysis of Severe Firearm Injuries Compared to Other Injury Mechanisms: Event Characteristics, Location, Timing, and Outcomes.

OBJECTIVES: Relatively little is known about the context and location of firearm injury events. Using a prospective cohort of trauma patients, we describe and compare severe firearm injury events to other violent and nonviolent injury mechanisms regarding incident location, proximity to home, time of day, spatial clustering, and outcomes. METHODS: This was a secondary analysis of a prospective cohort of injured children and adults with hypotension or Glasgow Coma Scale score ≤ 8, injured by one of four primary injury mechanisms (firearm, stabbing, assault, and motor vehicle collision [MVC]) who were transported by emergency medical services to a Level I or II trauma center in 10 regions of the United States and Canada from January 1, 2010, through June 30, 2011. We used descriptive statistics and geospatial analyses to compare the injury groups, distance from home, outcomes, and spatial clustering. RESULTS: There were 2,079 persons available for analysis, including 506 (24.3%) firearm injuries, 297 (14.3%) stabbings, 339 (16.3%) assaults, and 950 (45.7%) MVCs. Firearm injuries resulted in the highest proportion of serious injuries (66.3%), early critical resources (75.3%), and in-hospital mortality (53.5%). Injury events occurring within 1 mile of a patient's home included 53.9% of stabbings, 49.2% of firearm events, 41.3% of assaults, and 20.0% of MVCs; the non-MVC events frequently occurred at home. While there was geospatial clustering, 94.4% of firearm events occurred outside of geographic clusters. CONCLUSIONS: Severe firearm events tend to occur within a patient's own neighborhood, often at home, and generally outside of geospatial clusters. Public health efforts should focus on the home in all types of neighborhoods to reduce firearm violence.

The effect of prolonged light intensity exercise in the heat on executive function.

OBJECTIVE: When people are involved in outdoor activities, it is important to be able to assess a situation and make rational decisions. The goal of this study is to determine the effects of 90 minutes of light-intensity exercise in a hot environment on executive functioning capabilities of healthy individuals. METHODS: In this prospective laboratory study, 40 healthy male and female subjects 18 to 45 years of age performed treadmill exercise while wearing athletic clothing and a backpack in either a hot or temperate environment. Vital signs, core and skin temperature, and perceptual measures (thermal sensation, sweating, comfort, and perceived exertion) were measured before, during, and after the treadmill test. Cognitive function was measured before and after the treadmill test using the Wisconsin Card Sorting Test (WCST) and a Psychomotor Vigilance Test (PVT). RESULTS: Subjects in the hot condition reached a similar core temp of 38.2° ± 0.5°C vs 37.7° ± 0.3°C (P = .325) in the temperate group but had a higher heart rate (P < .001) and skin temperature (P < .001). Hot and normal temperature groups did not differ in their PVT performance. There were more correct responses (P < .001), fewer errors (P < .001), and more conceptual responses (P = .001) on the WCST after exertion in both the hot room and normal temperature room conditions. Perseverations and perseverative errors (P = .002) decreased in both groups after exertion. CONCLUSIONS: Conditions of mild heat stress coupled with modest rehydration and short hiking treks do not appear to negatively affect executive function or vigilance.

The effect of body mass index on intubation success rates and complications during emergency airway management.

We evaluated the effect of body mass index (BMI) on intubation success rates and complications during emergency airway management. We retrospectively analyzed an airway registry at an academic medical center. The primary outcomes were the incidence of difficult intubation and complication rates, stratified by BMI. We captured 1,075 (98 %, 1,075/1,102; 95 % CI 97-99) intubations. Four hundred twenty-six patients (40 %) had a normal BMI, 289 (27 %) were overweight, 261 (25 %) were obese, and 77 (7 %) were morbidly obese. In a multivariate analysis, obesity (OR 1.90; 95 % CI 1.04-3.45; p = 0.04), but not morbid obesity (OR 2.18; 95 % CI 0.95-4.99; p = 0.07), predicted difficult intubation. BMI was not predictive of post-intubation complications. Airway management in the morbidly obese differed when compared with lean patients, with less use of rapid sequence intubation and increased use of fiberoptic bronchoscopy in the former. During emergency airway management, difficult intubation is more common in obese patients, and morbidly obese patients are more commonly treated as potentially difficult airways.