Prehospital End-tidal Carbon Dioxide Predicts Mortality in Trauma Patients

Advanced Critical Care Techniques in the Field

Critical care principles and techniques continue to hold promise for improving patient outcomes in time-dependent diseases encountered by emergency medical services such as cardiac arrest, acute ischemic stroke, and hemorrhagic shock. In this review, the authors discuss several current and evolving advanced critical care modalities, including extracorporeal cardiopulmonary resuscitation, resuscitative endovascular occlusion of the aorta, prehospital thrombolytics for acute ischemic stroke, and low-titer group O whole blood for trauma patients. Two important critical care monitoring technologies-capnography and ultrasound-are also briefly discussed.

Utility of non-invasive monitoring of exhaled carbon dioxide and perfusion index in adult patients in the emergency department

BACKGROUND

Several noninvasive solutions are available for the assessment of patients at risk of deterioration. Capnography, in the form of end-tidal exhaled CO2 (ETCO2) and perfusion index (PI), could provide relevant information about patient prognosis. The aim of the present project was to determine the association of ETCO2 and PI with mortality of patients admitted to the emergency department (ED).

METHODS

Multicenter, prospective, cohort study of adult patients with acute disease who needed continuous monitoring in the ED. The study included two tertiary hospitals in Spain between October 2022 and June 2023. The primary outcome of the study was in-hospital mortality (all-cause). Demographics, vital signs, ETCO2 and PI were collected.

RESULTS

A total of 687 patients were included in the study. The in-hospital mortality rate was 6.8%. The median age was 79 years (IQR: 69-86), and 63.3% were males. The median ETCO2 value was 30 mmHg (26-35) in survivors and 23 mmHg (16-30) in nonsurvivors (p = 0.001). For the PI, the medians were 4.7% (2.8-8.1) for survivors and 2.5% (0.98-4-4) for nonsurvivors (p < 0.001). The model that presented the best AUC was age (odds ratio (OR): 1.02 (1.00-1.05)), the respiratory rate (OR: 1.06 (1.02-1.11)), and the PI (OR: 0.83 (0.75-0.91)), with a result of 0.840 (95% CI: 0.795-0.886); the model with the respiratory rate (OR: 1.05 (1.01-1.10)), the PI (OR: 0.84 (0.76-0.93)), and the ETCO2 (no statistically significant OR), with an AUC of 0.838 (95% CI: 0.787-0.889).

CONCLUSIONS

The present study showed that the PI and respiratory rate are independently associated with in-hospital mortality. Both the PI and ETCO2 are predictive parameters with improved prognostic performance compared with that of standard vital signs.

Diagnostic utility of capnography in emergency department triage for screening acidemia: a pilot study

BACKGROUND

Capnography is a quantitative and reliable method of determining the ventilatory status of patients. We describe the test characteristics of capnography obtained during Emergency Department triage for screening acidemia.

RESULTS

We performed an observational, pilot study of adult patients presenting to Emergency Department (ED) triage. The primary outcome was acidemia, as determined by the basic metabolic panel and/or blood gas during the ED visit. Secondary outcomes include comparison of estimated and measured respiratory rates (RR), relationships between end-tidal CO2 (EtCO2) and venous partial pressure of CO2, admission disposition, in-hospital mortality during admission, and capnogram waveform analysis. A total of 100 adult ED encounters were included in the study and acidemia ([Formula: see text] or [Formula: see text]) was identified in 28 patients. The measured respiratory rate (20.3 ± 6.4 breaths/min) was significantly different from the estimated rate (18.4 ± 1.6 breaths/min), and its area under the receiver operating curve (c-statistic) to predict acidemia was only 0.60 (95% CI 0.51-0.75, p = 0.03). A low end-tidal CO2 (EtCO2 < 32 mmHg) had positive (LR+) and negative (LR-) likelihood ratios of 4.68 (95% CI 2.59-8.45) and 0.34 (95% CI 0.19-0.61) for acidemia, respectively-corresponding to sensitivity 71.4% (95% CI 51.3-86.8) and specificity 84.7% (95% CI 74.3-92.1). The c-statistic for EtCO2 was 0.849 (95% CI 0.76-0.94, p = 0.00). Waveform analysis further revealed characteristically abnormal capnograms that were associated with underlying pathophysiology.

CONCLUSIONS

Capnography is a quantitative method of screening acidemia in patients and can be implemented feasibly in Emergency Department triage as an adjunct to vital signs. While it was shown to have only modest ability to predict acidemia, triage capnography has wide generalizability to screen other life-threatening disease processes such as sepsis or can serve as an early indicator of clinical deterioration.

Prehospital ETCO2 is predictive of death in intubated and non-intubated patients

BACKGROUND

Prehospital identification of shock in trauma patients lacks accurate markers. Low end tidal carbon dioxide (ETCO2) correlates with mortality in intubated patients. The predictive value of ETCO2 obtained by nasal capnography cannula (NCC) is unknown. We hypothesized that prehospital ETCO2 values obtained by NCC and in-line ventilator circuit (ILVC) would be predictive of mortality.

METHODS

This was a prospective, observational, multicenter study. ETCO2 values were collected by a NCC or through ILVC. AUROCs were compared with prehospital systolic blood pressure (SBP) and shock index (SI). The Youden index defined optimal cutoffs.

RESULTS

Of 550 enrolled patients, 487 (88.5%) had ETCO2 measured through an NCC. Median age was 37 (27-52) years; 76.5% were male; median ISS was 13 (5-22). Mortality was 10.4%. Minimum prehospital ETCO2 significantly predicted mortality with an AUROC of 0.76 (CI 0.69-0.84; Youden index ​= ​22 ​mmHg), outperforming SBP with an AUROC of 0.68; (CI 0.62-0.74, p ​= ​0.04) and shock index with an AUROC of 0.67 (CI 0.59-0.74, p ​= ​0.03).

CONCLUSION

Prehospital ETCO2 measured by non-invasive NCC or ILVC may be predictive of mortality in injured patients.

The potential of point-of-care diagnostics to optimise prehospital trauma triage: a systematic review of literature

PURPOSE

In the prehospital care of potentially seriously injured patients resource allocation adapted to injury severity (triage) is a challenging. Insufficiently specified triage algorithms lead to the unnecessary activation of a trauma team (over-triage), resulting in ineffective consumption of economic and human resources. A prehospital trauma triage algorithm must reliably identify a patient bleeding or suffering from significant brain injuries. By supplementing the prehospital triage algorithm with in-hospital established point-of-care (POC) tools the sensitivity of the prehospital triage is potentially increased. Possible POC tools are lactate measurement and sonography of the thorax, the abdomen and the vena cava, the sonographic intracranial pressure measurement and the capnometry in the spontaneously breathing patient. The aim of this review was to assess the potential and to determine diagnostic cut-off values of selected instrument-based POC tools and the integration of these findings into a modified ABCDE based triage algorithm.

METHODS

A systemic search on MEDLINE via PubMed, LIVIVO and Embase was performed for patients in an acute setting on the topic of preclinical use of the selected POC tools to identify critical cranial and peripheral bleeding and the recognition of cerebral trauma sequelae. For the determination of the final cut-off values the selected papers were assessed with the Newcastle-Ottawa scale for determining the risk of bias and according to various quality criteria to subsequently be classified as suitable or unsuitable. PROSPERO Registration: CRD 42022339193.

RESULTS

267 papers were identified as potentially relevant and processed in full text form. 61 papers were selected for the final evaluation, of which 13 papers were decisive for determining the cut-off values. Findings illustrate that a preclinical use of point-of-care diagnostic is possible. These adjuncts can provide additional information about the expected long-term clinical course of patients. Clinical outcomes like mortality, need of emergency surgery, intensive care unit stay etc. were taken into account and a hypothetic cut-off value for trauma team activation could be determined for each adjunct. The cut-off values are as follows: end-expiratory CO2: < 30 mm/hg; sonography thorax + abdomen: abnormality detected; lactate measurement: > 2 mmol/L; optic nerve diameter in sonography: > 4.7 mm.

DISCUSSION

A preliminary version of a modified triage algorithm with hypothetic cut-off values for a trauma team activation was created. However, further studies should be conducted to optimize the final cut-off values in the future. Furthermore, studies need to evaluate the practical application of the modified algorithm in terms of feasibility (e.g. duration of application, technique, etc.) and the effects of the new algorithm on over-triage. Limiting factors are the restriction with the search and the heterogeneity between the studies (e.g. varying measurement devices, techniques etc.).

End-tidal carbon dioxide measured at emergency department triage outperforms standard triage vital signs in predicting in-hospital mortality and intensive care unit admission

OBJECTIVES

This study assessed the ability of end-tidal carbon dioxide (ETCO2 ) in predicting in-hospital mortality and intensive care unit (ICU) admission compared to standard vital signs at ED triage as well as comparing to measures of metabolic acidosis.

METHODS

This prospective study enrolled adult patients presenting to the ED of a tertiary care Level I trauma center over 30 months. Patients had standard vital signs measured along with exhaled ETCO2 at triage. Outcome measures included in-hospital mortality; ICU admission; and correlations with lactate, sodium bicarbonate (HCO3 ), and anion gap.

RESULTS

There were 1136 patients enrolled and 1091 patients with outcome data available. There were 26 (2.4%) patients who did not survive to hospital discharge. Mean ETCO2 levels were 34 (33-34) in survivors and 22 (18-26) nonsurvivors (p < 0.001). The area under the curve (AUC) for predicting in-hospital mortality for ETCO2 was 0.82 (0.72-0.91). In comparison the AUC for temperature was 0.55 (0.42-0.68), respiratory rate (RR) 0.59 (0.46-0.73), systolic blood pressure (SBP) 0.77 (0.67-0.86), diastolic blood pressure (DBP) 0.70 (0.59-0.81), heart rate (HR) 0.76 (0.66-0.85), and oxygen saturation (SpO2 ) 0.53 (0.40-0.67). There were 64 (6%) patients admitted to the ICU, and the ETCO2 AUC for predicting ICU admission was 0.75 (0.67-0.80). In comparison the AUC for temperature was 0.51, RR 0.56, SBP 0.64, DBP 0.63, HR 0.66, and SpO2 0.53. Correlations between expired ETCO2 and serum lactate, anion gap, and HCO3 were rho = -0.25 (p < 0.001), rho = -0.20 (p < 0.001), and rho = 0.330 (p < 0.001), respectively.

CONCLUSIONS

ETCO2 was a better predictor of in-hospital mortality and ICU admission than the standard vital signs at ED triage. ETCO2 correlated significantly with measures of metabolic acidosis.

The effect of surgical masks on vital signs and EtCO2 in patients on oxygen therapy

BACKGROUND

There are conflicting data on the effects of masks on vital signs and end-tidal CO₂ (EtCO₂) values in the literature.

AIMS

This study aims to evaluate the changes in the vital parameters and EtCO₂ values of the patients who were administered oxygen through nasal cannula (NC) and simple oxygen mask (SOM) and wore surgical masks (SM) on top during their treatment.

METHODS

The prospective, observational study was conducted from January 2021, over consecutive 30 days, in the emergency department of a tertiary-care university hospital. The vital signs and EtCO₂ values of the subjects administered O₂ were noted at the time of arrival and at the 30th and 120th minutes of treatment. Changes in vital signs and EtCO₂ values were compared with regard to NC-SM and SOM-SM applications over a 120-min study period.

RESULTS

Sixty-eight subjects were included in two groups (NC-SM [n = 49] and SOM-SM [n = 19]). At the 120th minute, a decrease in systolic and diastolic blood pressure, heart rate, and respiratory rate and an increase in oxygen saturation were observed in the group including all subjects. After decreasing slightly in the first 30 min, the EtCO₂ value remained stable.

CONCLUSIONS

NC-SM and SOM-SM applications do not affect adversely, and even seem to lead to recovery of, the vital signs and EtCO₂ values during 120 min in subjects with acute complaints.

Prehospital end-tidal carbon dioxide is predictive of death and massive transfusion in injured patients: An Eastern Association for Surgery of Trauma multicenter trial

BACKGROUND

Prehospital identification of the injured patient likely to require emergent care remains a challenge. End-tidal carbon dioxide (ETCO2) has been used in the prehospital setting to monitor respiratory physiology and confirmation of endotracheal tube placement. Low levels of ETCO2 have been demonstrated to correlate with injury severity and mortality in a number of in-hospital studies. We hypothesized that prehospital ETCO2 values would be predictive of mortality and need for massive transfusion (MT) in intubated patients.

METHODS

This was a retrospective multicenter trial with 24 participating centers. Prehospital, emergency department, and hospital values were collected. Receiver operating characteristic curves were created and compared. Massive transfusion defined as >10 U of blood in 6 hours or death in 6 hours with at least 1 U of blood transfused.

RESULTS

A total of 1,324 patients were enrolled. ETCO2 (area under the receiver operating characteristic curve [AUROC], 0.67; confidence interval [CI], 0.63-0.71) was better in predicting mortality than shock index (SI) (AUROC, 0.55; CI, 0.50-0.60) and systolic blood pressure (SBP) (AUROC, 0.58; CI, 0.53-0.62) (p < 0.0005). Prehospital lowest ETCO2 (AUROC, 0.69; CI, 0.64-0.75), SBP (AUROC, 0.75; CI, 0.70-0.81), and SI (AUROC, 0.74; CI, 0.68-0.79) were all predictive of MT. Analysis of patients with normotension demonstrated lowest prehospital ETCO2 (AUROC, 0.66; CI, 0.61-0.71), which was more predictive of mortality than SBP (AUROC, 0.52; CI, 0.47-0.58) or SI (AUROC, 0.56; CI, 0.50-0.62) (p < 0.001). Lowest prehospital ETCO2 (AUROC, 0.75; CI, 0.65-0.84), SBP (AUROC, 0.63; CI, 0.54-0.74), and SI (AUROC, 0.64; CI, 0.54-0.75) were predictive of MT in normotensive patients. ETCO2 cutoff for MT was 26 mm Hg. The positive predictive value was 16.1%, and negative predictive value was high at 98.1%.

CONCLUSION

Prehospital ETCO2 is predictive of mortality and MT. ETCO2 outperformed traditional measures such as SBP and SI in the prediction of mortality. ETCO2 may outperform traditional measures in predicting need for transfusion in occult shock.

LEVEL OF EVIDENCE

Diagnostic test, level III.

Prehospital end-tidal carbon dioxide predicts hemorrhagic shock upon emergency department arrival

BACKGROUND

In addition to reflecting gas exchange within the lungs, end-tidal carbon dioxide (ETCO2) also reflects cardiac output based on CO2 delivery to the pulmonary parenchyma. We hypothesized that low prehospital ETCO2 values would be predictive of hemorrhagic shock in intubated trauma patients.

METHODS

A retrospective observational study of adult trauma patients intubated in the prehospital setting and transported to a single Level I trauma center from 2016 to 2019. Continuous prehospital ETCO2 data were linked with patient care registries. We developed a novel analytic approach that allows for reflection of prehospital ETCO2 over the entire prehospital course of care. The primary outcome was hemorrhagic shock on emergency department (ED) presentation, defined as either initial ED systolic blood pressure of 90 mm Hg or less or initial Shock Index (SI) > 0.9, and transfusion of at least one unit of blood product during their ED stay. Prehospital ETCO2 less than 25 mm Hg was evaluated for predictive value of hemorrhagic shock.

RESULTS

Three hundred and seven patients (82% men, 34% penetrating injury, 42% in hemorrhagic shock on ED arrival, 27% mortality) were included in the study. Patients in hemorrhagic shock had lower median ETCO2 values (26.5 mm Hg vs. 32.5 mm Hg; p < 0.001) than those not in hemorrhagic shock. Patients with prehospital ETCO2 less than 25 mm Hg were 3.0 times (adjusted odds ratio = 3.0; 95% confidence interval, 1.1-7.9) more likely to be in hemorrhagic shock upon ED arrival than patients with ETCO2 ≥ 25 mm Hg.

CONCLUSION

Intubated patients with hemorrhagic shock upon ED arrival had significantly lower prehospital ETCO2 values. Incorporating ETCO2 assessment into prehospital care for trauma patients could support decisions regarding prehospital blood transfusion, and triage to higher-level trauma centers, and trauma team activation.

LEVEL OF EVIDENCE

Prognostic, level III.

"Low initial pre-hospital end-tidal carbon dioxide predicts inferior clinical outcomes in trauma patients"

INTRODUCTION

Current guidelines continue to lead to under- and over-triage of injured patients in the pre-hospital setting. End-tidal carbon dioxide (ETCO2) has been correlated with mortality and hemorrhagic shock in trauma patients. This study examines the correlation between ETCO2 and in-hospital outcomes among non-intubated patients in the pre-hospital setting.

METHODS

We retrospectively studied a cohort of non-intubated adult trauma patients with initial pre-hospital side-stream capnography-obtained ETCO2 presenting via ground transport from a single North Carolina EMS agency to a level one trauma center from January 2018 to December 2018. Using the Liu method, the optimal threshold for low ETCO2 was ≤ 28.5 mmHg.

RESULTS

Initial pre-hospital ETCO2 was recorded for 324 (22.0%) of 1473 patients with EMS data. Patients with low ETCO2 (N = 98, 30.3% of cohort) were older (median 58y vs 45y), but mechanisms of injury and scene vital signs were similar (p>0.05) between low and normal/high ETCO2 cohorts. Median injury severity score (ISS) did not differ significantly between the low and normal/high ETCO2 groups (5 vs 8, p=0.48). Compared to normal/high ETCO2, low ETCO2 correlated with increased unadjusted odds of mortality (OR 5.06), in-hospital complications (OR 2.06), and blood transfusion requirement (OR 3.05), p<0.05. Low ETCO2 was associated with 7.25 odds of mortality (95% CI 2.19,23.97, p=0.001) and 3.94 odds of blood transfusion (95% CI 1.32-11.78) after adjusting for age, ISS, and scene GCS. All but one of the massive transfusion patients (N = 8/9) had a low pre-hospital ETCO2.

CONCLUSIONS

Low initial pre-hospital ETCO2 associates with poor clinical outcomes despite similar ISS and mechanisms of injury. ETCO2 is a potentially useful pre-hospital point-of-care tool to aid triage of trauma patients as it may identify hemorrhaging patients and predict mortality.

The utility of transcutaneous carbon dioxide measurements in the emergency department: A prospective cohort study

BACKGROUND

Rapid identification of patients with occult injury and illness in the emergency department can be difficult. Transcutaneous carbon dioxide (TCO2) and oxygen (TO2) measurements may be non-invasive surrogate markers for the identification of such patients.

OBJECTIVES

To determine if TCO2 or TO2 are useful adjuncts for identifying severe illness and the correlation between TCO2, lactate, and end tidal carbon dioxide (ETCO2).

METHODS

Prospective TCO2 and TO2 measurements at a tertiary level 1 trauma center were obtained using a transcutaneous sensor on 300 adult patients. Severe illness was defined as death, intensive care unit (ICU) admission, bilevel positive airway pressure, vasopressor use, or length of stay >2 days. TCO2 and TO2 were compared to illness severity using t tests and correlation coefficients.

RESULTS

Mean TO2 did not differ between severe illness (58.9, 95% CI 54.9-62.9) and non-severe illness (58.0, 95% CI 54.7-61.1). Mean TCO2 was similar between severe (34.6, 95% CI 33-36.2) vs non-severe illness (35.9, 95% CI 34.7-37.1). TCO2 was 28.7 (95% CI 24.0-33.4) for ICU vs. 35.9 (95% CI 34.9-36.9) for non-ICU patients. The mean TCO2 in those with lactate > 2.0 was 29.8 (95% CI 25.8-33.8) compared with 35.7 (95% CI 34.9-36.9) for lactate < 2.0. TCO2 was not correlated with ETCO2 (r = 0.32, 95% CI 0.22-0.42).

CONCLUSION

TCO2 could be a useful adjunct for identifying significant injury and illness and patient outcomes in an emergency department (ED) population. TO2 did not predict severe illness. TCO2 and ETCO2 are only moderately correlated, indicating that they are not equivalent and may be useful under different circumstances.

Association of Ventilation during Initial Trauma Resuscitation for Traumatic Brain Injury and Post-Traumatic Outcomes: A Systematic Review

OBJECTIVES

In the absence of evidence of acute cerebral herniation, normal ventilation is recommended for patients with traumatic brain injury (TBI). Despite this recommendation, ventilation strategies vary during the initial management of patients with TBI and may impact outcome. The goal of this systematic review was to define the best evidence-based practice of ventilation management during the initial resuscitation period.

METHODS

A literature search of PubMed, CINAHL, and SCOPUS identified studies from 2009 through 2019 addressing the effects of ventilation during the initial post-trauma resuscitation on patient outcomes.

RESULTS

The initial search yielded 899 articles, from which 13 were relevant and selected for full-text review. Six of the 13 articles met the inclusion criteria, all of which reported on patients with TBI. Either end-tidal carbon dioxide (ETCO2) or partial pressure carbon dioxide (PCO2) were the independent variables associated with mortality. Decreased rates of mortality were reported in patients with normal PCO2 or ETCO2.

CONCLUSIONS

Normoventilation, as measured by ETCO2 or PCO2, is associated with decreased mortality in patients with TBI. Preventing hyperventilation or hypoventilation in patients with TBI during the early resuscitation phase could improve outcome after TBI.

Prehospital End-Tidal CO2: A Superior Marker for Mortality Risk in the Acutely Injured Patient

BACKGROUND

Emergency medical personnel must expeditiously triage acutely injured patients to the appropriate medical facility. Efficient and objective variables to facilitate this process and provide information to the receiving trauma center are needed. Currently, multiple variables are used to prognosticate injury severity and risk of mortality including vital signs, mental status, lactate, and base excess. We investigated the prehospital use of end-tidal carbon dioxide (ETCO₂) as a noninvasive physiologic measure that can be obtained in the acutely injured patient.

METHODS

We performed a retrospective analysis of 557 acutely injured patients over 2 years at a Level 1 trauma center. All patients arriving as trauma activations with ETCO₂ measurements were included in analysis. End-tidal carbon dioxide measurements were categorized as low, normal, and high based on reference levels. Mortality was the primary outcome. Secondary receiver operator curves (ROC) for base excess, venous lactate, blood pressure, and venous pH were compared. We hypothesized ETCO₂ levels would be able to predict mortality.

RESULTS

End-tidal carbon dioxide levels conferred a mortality rate of 38%, 17.3%, and 2.9% for low, normal, and high, respectively (P < .001). Receiver operator curve analysis produced an area under the curve predictive value for ETCO₂ (.748) which was superior to lactate (.660), SBP (.578), pH (.560), and base excess (.497).

DISCUSSION

End-tidal carbon dioxide is a more sensitive and specific predictor of mortality in the acutely injured patient compared to venous lactate, base deficit, blood pressure, or venous pH. Additional studies are needed to determine if ETCO₂ can be used as an effective prehospital adjunct to prevent mortality in acutely injured patients.

Association of Prehospital Oxygen Saturation to Inspired Oxygen Ratio With 1-, 2-, and 7-Day Mortality

IMPORTANCE

The early identification of patients at high risk of clinical deterioration represents one of the greatest challenges for emergency medical services (EMS).

OBJECTIVE

To assess whether use of the ratio of prehospital oxygen saturation measured by pulse oximetry (Spo2) to fraction of inspired oxygen (Fio2) measured during initial contact by EMS with the patient (ie, the first Spo2 to Fio2 ratio) and 5 minutes before the patient's arrival at the hospital (ie, the second Spo2 to Fio2 ratio) can predict the risk of early in-hospital deterioration.

DESIGN, SETTING, AND PARTICIPANTS

A prospective, derivation-validation prognostic cohort study of 3606 adults with acute diseases referred to 5 tertiary care hospitals in Spain was conducted between October 26, 2018, and June 30, 2020. Eligible patients were recruited from among all telephone requests for EMS assistance for adults who were later evacuated with priority in advanced life support units to the referral hospitals during the study period.

MAIN OUTCOMES AND MEASURES

The primary outcome was hospital mortality from any cause within the first, second, third, or seventh day after EMS transport to the hospital. The main measure was the Spo2 to Fio2 ratio.

RESULTS

A total of 3606 participants comprised 2 separate cohorts: the derivation cohort (3081 patients) and the validation cohort (525 patients). The median age was 69 years (interquartile range, 54-81 years), and 2122 patients (58.8%) were men. The overall mortality rate of the patients in the study cohort ranged from 3.6% for 1-day mortality (131 patients) to 7.1% for 7-day mortality (256 patients). The best model performance was for 2-day mortality with the second Spo2 to Fio2 ratio with an area under the curve of 0.890 (95% CI, 0.829-0.950; P < .001), although the other outcomes also presented good results. In addition, a risk-stratification model was generated. The optimal cutoff resulted in the following ranges of Spo2 to Fio2 ratios: 50 to 100 for high risk of mortality, 101 to 426 for intermediate risk, and 427 to 476 for low risk.

CONCLUSIONS AND RELEVANCE

This study suggests that use of the prehospital Spo2 to Fio2 ratio was associated with improved management of patients with acute disease because it accurately predicts short-term mortality.

Prehospital end-tidal carbon dioxide predicts massive transfusion and death following trauma

BACKGROUND

The lack of an accurate marker of prehospital hemorrhagic shock limits our ability to triage patients to the correct level of care, delays treatment in the emergency department, and inhibits our ability to perform prehospital interventional research in trauma. End-tidal carbon dioxide (ETCO2) is the measurement of alveolar carbon dioxide concentration at end expiration and is measured noninvasively in the ventilator circuit for intubated patients in continuous manner. Several hospital-based studies have been able to demonstrate that either low or decreasing levels of ETCO2 as well as disparities between ETCO2 and plasma carbon dioxide correlate with increasing mortality in trauma. We hypothesized that prehospital ETCO2 values will be predictive of mortality and need for massive transfusion following injury.

METHODS

This is a single-center retrospective study from an urban level 1 trauma center. We reviewed all intubated adult patients transported for injury who had prehospital ETCO2 values available. Unadjusted comparisons of continuous variables were done with the Wilcoxon two-sample test. The predictive performance of prehospital ETCO2, the prehospital shock index, and prehospital systolic blood pressure were assessed and compared using areas under the receiver operating characteristic curves. Optimal cutoffs were estimated by maximizing the Youden index. Massive transfusion was defined as >10 U of blood or death in 24 hours.

RESULTS

A total of 173 patients were identified with prehospital ETCO2 values during the 2-year study period. Population was 78.5% male with a median age of 37.5 years (interquartile range, 23.5-53.5 years). Injury mechanism was penetrating in 22.8%. This cohort had a median Injury Severity Score of 26 (interquartile range, 17-36), massive transfusion rate of 34.7%, and mortality of 42.1%. In the evaluation of prediction of postinjury mortality and massive transfusion, ETCO2 outperformed systolic blood pressure and shock index, but these differences did not reach statistical significance.

CONCLUSION

End-tidal carbon dioxide is a novel prehospital predictor of mortality and massive transfusion after injury.

LEVEL OF EVIDENCE

Prognostic/Epidemiologic, level III.

Correlation of Nasal Cannula End-Tidal Carbon Dioxide Concentration With Need for Critical Resources for Blunt Trauma Patients Triaged to Lower-Tier Trauma Activation

Patients assigned lower-tier trauma activation may be undertriaged. Delayed recognition and intervention may adversely affect outcome. For critically injured intubated patients, research shows that abnormally low end-tidal carbon dioxide (EtCO2) values correlate with need for blood transfusion, surgery, and mortality. The purpose of this study was to evaluate EtCO2 monitoring for patients triaged to lower-tier trauma activation. EtCO2 monitoring may aid in the recognition of patients who have greater needs than anticipated. This is a prospective observational study conducted at a Level I trauma center. Potential subjects presenting from the field were identified by lower-tier trauma activation for blunt mechanism. EtCO2 measurements acquired using nasal cannula sidestream technology were prospectively recorded in the trauma bay during the initial assessment. The medical record and trauma registry were queried for demographics, injury data, mortality, and critical resource data defined as intubation, blood transfusion, surgery, intensive care unit admission, and vasoactive medication infusion. EtCO2 data were obtained for 682 subjects during a 10.5-month period. Following exclusions, 262 patients were enrolled for data collection. EtCO2 values less than 30 mmHg were significantly associated with blood transfusion (p = .03) but not with other critical resources or mortality. Although capnography had limited utility for patients triaged to lower-tier trauma activation, EtCO2 values less than 30 mmHg correlated with blood transfusion, consistent with previous studies of critically injured intubated patients. EtCO2 monitoring is noninvasive and may serve as a simple prompt for earlier initiation of blood transfusion, a resource-intensive intervention.

Out-of-hospital Respiratory Measures to Identify Patients With Serious Injury: A Systematic Review

OBJECTIVES

The objective was to systematically review the published literature on the diagnostic accuracy of out-of-hospital respiratory measures for identifying patients with serious injury, focusing on measures feasible for field triage by emergency medical services personnel.

METHODS

We searched Ovid MEDLINE, CINAHL, and the Cochrane databases from January 1, 1996, through August 31, 2017. We included studies on the diagnostic accuracy (sensitivity, specificity, and area under the receiver operating characteristic curve [AUROC]) for all respiratory measures used to identify patients with serious injury (resource use, serious anatomic injury, and mortality). We assessed studies for risk of bias and strength of evidence (SOE). We performed meta-analysis for measures with sufficient data.

RESULTS

We identified 46 articles reporting results of 44 studies. Out-of-hospital respiratory measures included respiratory rate, pulse oximetry, and airway support. Meta-analysis was only possible for respiratory rate, which demonstrated a pooled sensitivity for serious injury of 13% (95% confidence interval [CI] = 5 to 29, I²  = 97.8%), specificity of 96% (95% CI = 83 to 99, I²  = 99.6%), and AUROC of 0.70 (95% CI = 0.66 to 0.79, I²  = 16.6%). For oxygen saturation, sensitivity ranged from 13% to 63%; specificity, 85% to 99%; and AUROC, 0.53 to 0.76. Need for airway support had a sensitivity of 8% to 53% and specificity of 61% to 100%; studies did not report AUROC. Across respiratory measures, the SOE was low. Other respiratory measures (pH, end-tidal carbon dioxide [CO₂ ], and sublingual partial pressure of CO₂ ) were reported only in emergency department studies.

CONCLUSIONS

Data on the accuracy of out-of-hospital respiratory measures for field triage are limited and of low quality. Based on available research, respiratory rate, oxygen saturation, and need for airway intervention all have low sensitivity, high specificity, and poor to fair discrimination for identifying seriously injured patients.

Mechanical ventilation of patients in helicopter emergency medical service transport: an international survey

BACKGROUND

Mechanical ventilation in helicopter emergency medical service (HEMS) environments is a procedure which carries a significant risk of complications. Limited data on the quality and performance of mechanical ventilation in HEMS are available in the literature.

METHOD

We conducted an international survey to evaluate mechanical ventilation infrastructure in HEMS and collect data of transported ventilated patients. From June 20-22, 2019, the participating HEMS bases were asked to provide data via a web-based platform. Vital parameters and ventilation settings of the patients at first patient contact and at handover were compared using non-parametric statistical tests.

RESULTS

Out of 215 invited HEMS bases, 53 responded. Respondents were from Germany, Denmark, United Kingdom, Luxembourg, Austria and Switzerland. Of the HEMS bases, all teams were physician staffed, mainly anesthesiologists (79%), the majority were board certified (92.5%) and trained in intensive care medicine (89%) and had a median (range) experience in HEMS of 9 (0-25) years. HEMS may provide a high level of expertise in mechanical ventilation whereas the majority of ventilators are able to provide pressure controlled ventilation and continuous positive airway pressure modes (77%). Data of 30 ventilated patients with a median (range) age of 54 (21-100) years and 53% male gender were analyzed. Of these, 24 were primary missions and 6 interfacility transports. At handover, oxygen saturation (p < 0.01) and positive end-expiratory pressure (p = 0.04) of the patients were significantly higher compared to first patient contact.

CONCLUSION

In this survey, the management of ventilated HEMS-patients was not associated with ventilation related serious adverse events. Patient conditions, training of medical crew and different technical and environmental resources are likely to influence management. Further studies are necessary to assess safety and process quality of mechanical ventilation in HEMS.

TRIAL REGISTRATION

The survey was prospectively registered at Research Registry ( researchregistry2925 ).

End-tidal carbon dioxide underestimates plasma carbon dioxide during emergent trauma laparotomy leading to hypoventilation and misguided resuscitation: A Western Trauma Association Multicenter Study

BACKGROUND

End-tidal carbon dioxide (ETCO2) is routinely used during elective surgery to monitor ventilation. The role of ETCO2 monitoring in emergent trauma operations is poorly understood. We hypothesized that ETCO2 values underestimate plasma carbon dioxide (pCO2) values during resuscitation for hemorrhagic shock.

METHODS

Multicenter trial was performed analyzing the correlation between ETCO2 and pCO2 levels.

RESULTS

Two hundred fifty-six patients resulted in 587 matched pairs of ETCO2 and pCO2. Correlation between these two values was very poor with an R of 0.04. 40.2% of patients presented to the operating room acidotic and hypercarbic with a pH less than 7.30 and a pCO2 greater than 45 mm Hg. Correlation was worse in patients that were either acidotic or hypercarbic. Forty-five percent of patients have a difference greater than 10 mm Hg between ETCO2 and pCO2. A pH less than 7.30 was predictive of an ETCO2 to pCO2 difference greater than 10 mm Hg. A difference greater than 10 mm Hg was predictive of mortality independent of confounders.

CONCLUSION

Nearly one half (45%) of patients were found to have an ETCO2 level greater than 10 mm Hg discordant from their PCO2 level. Reliance on the discordant values may have contributed to the 40% of patients in the operating room that were both acidotic and hypercarbic. Early blood gas analysis is warranted, and a lower early goal of ETCO2 should be considered.

LEVEL OF EVIDENCE

Therapeutic, level IV.

Utilizing End-Tidal Carbon Dioxide to Diagnose Diabetic Ketoacidosis in Prehospital Patients with Hyperglycemia

Background:

Early identification of diabetic ketoacidosis (DKA) may improve clinical outcomes. Prior studies suggest exhaled end tidal carbon dioxide (ETCO2) provides a non-invasive, real-time method to screen for DKA in the emergency department (ED).

Methods:

This a retrospective cohort study among patients who activated Emergency Medical Services (EMS) during a one-year period. Initial out-of-hospital vital signs documented by EMS personnel, including ETCO2 and first recorded blood glucose level (BGL), as well as in-hospital records, including laboratory values and diagnosis, were collected. The main outcome was the association between ETCO2 and the diagnosis of DKA.

Results:

Of the 118 patients transported with hyperglycemia (defined by BGL >200), six (5%) were diagnosed with DKA. The mean level of ETCO2 in those without DKA was 35mmHg (95% CI, 33-38mmHg) compared to mean levels of 15mmHg (95% CI, 8-21mmHg) in those with DKA (P <.001). The Area Under the Receiver Operating Characteristics (ROC) Curve (AUC) for ETCO2 identifying DKA was 0.96 (95% CI, 0.92-1.00). The correlation coefficient between ETCO2 and serum bicarbonate (HCO3) was 0.436 (P <.001) and the correlation coefficient between ETCO2 and anion gap was -0.397 (P <.001).

Conclusion:

Among patients with hyperglycemia, prehospital levels of ETCO2 were significantly lower in patients with DKA compared to those without and were predictive of the diagnosis of DKA. Furthermore, out-of-hospital ETCO2 was significantly correlated with measures of metabolic acidosis.

Epidemiological and Accounting Analysis of Ground Ambulance Whole Blood Transfusion

INTRODUCTION

In October 2017, the American Association of Blood Bankers (AABB; Bethesda, Maryland USA) approved a petition to allow low-titer group O whole blood as a standard product without the need for a waiver. Around that time, a few Texas, USA-based Emergency Medical Services (EMS) systems incorporated whole blood into their ground ambulances. The purpose of this project was to describe the epidemiology of ground ambulance patients that received a prehospital whole blood transfusion. The secondary aim of this project was to report an accounting analysis of these ground ambulance prehospital whole blood programs.

METHODS

The dataset came from the Harris County Emergency Service District 48 Fire Department (HCESD 48; Harris County, Texas USA) and San Antonio Fire Department (SAFD; San Antonio, Texas USA) whole blood Quality Assurance/Quality Improvement (QA/QI) databases from September 2017 through December 2018. The primary outcome of this study was the prehospital transfusion indication. The secondary outcome was the projected cost per life saved during the first 10 years of the prehospital whole blood initiative.

RESULTS

Of 58 consecutive prehospital whole blood administrations, the team included all 58 cases. Hemorrhagic shock from a non-traumatic etiology accounted for 46.5% (95% CI, 34.3%-59.2%) of prehospital whole blood recipients. In the non-traumatic hemorrhagic shock cohort, gastrointestinal hemorrhage was the underlying etiology of hemorrhagic shock in 66.7% (95% CI, 47.8%-81.4%) of prehospital whole blood transfusion recipients. The projected average cost to save a life in Year 10 was US$5,136.51 for the combined cohort, US$4,512.69 for HCESD 48, and US$5,243.72 for SAFD EMS.

CONCLUSION

This retrospective analysis of ground ambulance patients that receive prehospital whole blood transfusion found that non-traumatic etiology accounted for 46.5% (95% CI, 34.3%-59.2%) of prehospital whole blood recipients. Additionally, the accounting analysis suggests that by Year 10 of a ground ambulance whole blood transfusion program, the average cost to save a life will be approximately US$5,136.51.

Delayed Sequence Intubation by Intensive Care Flight Paramedics in Victoria, Australia

OBJECTIVE

Delayed sequence intubation (DSI) involves the administration of ketamine to facilitate adequate preoxygenation in the agitated patient. DSI was introduced into the Clinical Practice Guideline for Intensive Care Flight Paramedics in Victoria in late 2013. We aimed to describe the clinical characteristics of patients receiving DSI.

METHODS

A retrospective analysis was undertaken of patients who received DSI between January 1, 2014, and December 31, 2016, during both primary response and retrieval missions. Patients' clinical characteristics, DSI success rates, and complications were determined from electronic patient care records.

RESULTS

Forty patients received DSI during the study period. Of these, 32 were intubated to manage traumatic injury and the remaining 8 were intubated for medical reasons. On arrival of the first road ambulance, median oxygen saturation was 96.5%, and immediately prior to DSI the median was 98.0%. One patient had a period of self-limiting apnea (< 15 seconds) following ketamine administration. Oxygen saturation was either maintained or increased prior to laryngoscopy in all patients. Post-intubation, one patient experienced bradycardia (heart rate < 60 beats per minute), two patients had a systolic blood pressure drop of > 20 mm Hg, one patient experienced an increase in heart rate of > 20 beats per minute, and two patients had transient oxygen desaturation (< 85%). No patients experienced cardiac arrest or required surgical airway intervention. All patients were successfully intubated. After DSI, the median oxygen saturation was 100%.

CONCLUSIONS

DSI provides a reasonably safe and effective approach for intensive care flight paramedics in the preoxygenation of agitated, hypoxic patients in order to decrease the risk of peri-intubation desaturation and related hypoxic injury.