Effect of coronavirus disease 2019 pandemic on children’s visits to the emergency department

Purpose@#In the coronavirus disease 2019 pandemic, it is essential to supplement the changes in visiting patterns of individual emergency departments (EDs) to determine how to allocate emergency medicine resources. We compared the clinical features of children visiting the ED before and during the pandemic. @*Methods@#Children younger than 18 years who visited the ED from February 2019 through December 2020, except January 2020, were enrolled, and divided into those who visited before and after January 2020 (the pre-pandemic and pandemic groups, respectively). We compared the 2 groups in terms of the baseline characteristics (age, sex, mode and route of arrival, cause of visit, and time of visit), chief complaint, ED diagnosis, initial acuity and its accuracy, and ED outcomes (length of stay and disposition). @*Results@#The 31,036 children were categorized into the pre-pandemic (21,027 [67.8%]) and pandemic (10,009 [32.2%]) groups with a 52.4% decrease in the number of visits to the ED in the latter group. This decrease was more prominent in age 2-5 years (from 37.3% to 33.2%; P < 0.001), fever as a chief complaint (from 27.8% to 16.5%), diagnoses related to infection or the respiratory system (from 36.8% to 14.3%) or transfer to the ED (from 8.1% to 6.4%; P < 0.001). In contrast, increases were noted in age 12-17 years (from 14.9% to 17.4%; P < 0.001), injury (from 36.5% to 52.5%; P < 0.001), visits in the evening (from 54.9% to 57.4%; P < 0.001), length of stay longer than 6 hours (from 3.5% to 6.3%; P = 0.033), and low acuity (from 97.8% to 98.2%; P = 0.031). @*Conclusion@#The pandemic has brought about changes in visiting patterns of the ED. This study may help prepare strategies for the appropriate allocation and deployment of emergency medicine resources in the pandemic era.

Application of convolutional neural networks for distal radio-ulnar fracture detection on plain radiographs in the emergency room

Objective@#Recent studies have suggested that deep-learning models can satisfactorily assist in fracture diagnosis. We aimed to evaluate the performance of two of such models in wrist fracture detection. @*Methods@#We collected image data of patients who visited with wrist trauma at the emergency department. A dataset extracted from January 2018 to May 2020 was split into training (90%) and test (10%) datasets, and two types of convolutional neural networks (i.e., DenseNet-161 and ResNet-152) were trained to detect wrist fractures. Gradient-weighted class activation mapping was used to highlight the regions of radiograph scans that contributed to the decision of the model. Performance of the convolutional neural network models was evaluated using the area under the receiver operating characteristic curve. @*Results@#For model training, we used 4,551 radiographs from 798 patients and 4,443 radiographs from 1,481 patients with and without fractures, respectively. The remaining 10% (300 radiographs from 100 patients with fractures and 690 radiographs from 230 patients without fractures) was used as a test dataset. The sensitivity, specificity, positive predictive value, negative predictive value, and accuracy of DenseNet-161 and ResNet-152 in the test dataset were 90.3%, 90.3%, 80.3%, 95.6%, and 90.3% and 88.6%, 88.4%, 76.9%, 94.7%, and 88.5%, respectively. The area under the receiver operating characteristic curves of DenseNet-161 and ResNet-152 for wrist fracture detection were 0.962 and 0.947, respectively. @*Conclusion@#We demonstrated that DenseNet-161 and ResNet-152 models could help detect wrist fractures in the emergency room with satisfactory performance.

Application of convolutional neural networks for distal radio-ulnar fracture detection on plain radiographs in the emergency room

Objective@#Recent studies have suggested that deep-learning models can satisfactorily assist in fracture diagnosis. We aimed to evaluate the performance of two of such models in wrist fracture detection. @*Methods@#We collected image data of patients who visited with wrist trauma at the emergency department. A dataset extracted from January 2018 to May 2020 was split into training (90%) and test (10%) datasets, and two types of convolutional neural networks (i.e., DenseNet-161 and ResNet-152) were trained to detect wrist fractures. Gradient-weighted class activation mapping was used to highlight the regions of radiograph scans that contributed to the decision of the model. Performance of the convolutional neural network models was evaluated using the area under the receiver operating characteristic curve. @*Results@#For model training, we used 4,551 radiographs from 798 patients and 4,443 radiographs from 1,481 patients with and without fractures, respectively. The remaining 10% (300 radiographs from 100 patients with fractures and 690 radiographs from 230 patients without fractures) was used as a test dataset. The sensitivity, specificity, positive predictive value, negative predictive value, and accuracy of DenseNet-161 and ResNet-152 in the test dataset were 90.3%, 90.3%, 80.3%, 95.6%, and 90.3% and 88.6%, 88.4%, 76.9%, 94.7%, and 88.5%, respectively. The area under the receiver operating characteristic curves of DenseNet-161 and ResNet-152 for wrist fracture detection were 0.962 and 0.947, respectively. @*Conclusion@#We demonstrated that DenseNet-161 and ResNet-152 models could help detect wrist fractures in the emergency room with satisfactory performance.

Validation and modification of HEART score components for patients with chest pain in the emergency department

Objective@#This study aimed to clarify the relative prognostic value of each History, Electrocardiography, Age, Risk Factors, and Troponin (HEART) score component for major adverse cardiac events (MACE) within 3 months and validate the modified HEART (mHEART) score. @*Methods@#This study evaluated the HEART score components for patients with chest symptoms visiting the emergency department from November 19, 2018 to November 19, 2019. All components were evaluated using logistic regression analysis and the scores for HEART, mHEART, and Thrombolysis in Myocardial Infarction (TIMI) were determined using the receiver operating characteristics curve. @*Results@#The patients were divided into a derivation (809 patients) and a validation group (298 patients). In multivariate analysis, age did not show statistical significance in the detection of MACE within 3 months and the mHEART score was calculated after omitting the age component. The areas under the receiver operating characteristics curves for HEART, mHEART and TIMI scores in the prediction of MACE within 3 months were 0.88, 0.91, and 0.83, respectively, in the derivation group; and 0.88, 0.91, and 0.81, respectively, in the validation group. When the cutoff value for each scoring system was determined for the maintenance of a negative predictive value for a MACE rate >99%, the mHEART score showed the highest sensitivity, specificity, positive predictive value, and negative predictive value (97.4%, 54.2%, 23.7%, and 99.3%, respectively). @*Conclusion@#Our study showed that the mHEART score better detects short-term MACE in high-risk patients and ensures the safe disposition of low-risk patients than the HEART and TIMI scores.

Experience of administration of intravenous propafenone in single emergency medical center

Objective@#We aimed to share our experience studying the effects and stability of intravenous propafenone in patients with atrial fibrillation (AF). @*Methods@#This single-center retrospective study evaluated the baseline and clinical characteristics of patients with atrial fibrillation admitted to the emergency room and treated with propafenone between December 2018 and May 2019;patients were analyzed according to new onset AF and chronic AF groups. @*Results@#Among 24 patients included in the present study, 15 patients were in the new onset AF group while nine were in the chronic AF group. Cardioversion was successful in 15 (73.3%) in the new onset AF group and two (22.2%) in the chronic AF group (P=0.033). The time to cardioversion was relatively short in patients in the new onset AF group (81 minutes vs. 122 minutes, log-rank, P=0.019). Recurrence of AF at 30 days was two (17.2%) in the new onset AF group and 0 (0.0%) in the chronic AF group. No major adverse event was observed except each hypotension in the new onset and chronic AF groups. @*Conclusion@#Sinus conversion of propafenone in patients with AF occurring within 48 hours in the emergency room may be considered.

Central Venous Catheterization before Versus after Computed Tomography in Hemodynamically Unstable Patients with Major Blunt Trauma: Clinical Characteristics and Factors for Decision Making

PURPOSE@#When hemodynamically unstable patients with blunt major trauma arrive at the emergency department (ED), the safety of performing early whole-body computed tomography (WBCT) is concerning. Some clinicians perform central venous catheterization (CVC) before WBCT (pre-computed tomography [CT] group) for hemodynamic stabilization. However, as no study has reported the factors affecting this decision, we compared clinical characteristics and outcomes of the pre- and post-CT groups and determined factors affecting this decision.@*METHODS@#This retrospective study included 70 hemodynamically unstable patients with chest or/and abdominal blunt injury who underwent WBCT and CVC between March 2013 and November 2017.@*RESULTS@#Univariate analysis revealed that the injury severity score, intubation, pulse pressure, focused assessment with sonography in trauma positivity score, and pH were different between the pre-CT (34 patients, 48.6%) and post-CT (all, p < 0.05) groups. Multivariate analysis revealed that injury severity score (ISS) and intubation were factors affecting the decision to perform CVC before CT (p=0.003 and p=0.043). Regarding clinical outcomes, the interval from ED arrival to CT (p=0.011) and definite bleeding control (p=0.038), and hospital and intensive care unit lengths of stay (p=0.018 and p=0.053) were longer in the pre-CT group than in the post-CT group. Although not significant, the pre-CT group had lower survival rates at 24 hours and 28 days than the post-CT group (p=0.168 and p=0.226).@*CONCLUSIONS@#Clinicians have a tendency to perform CVC before CT in patients with blunt major trauma and high ISS and intubation.

A Case of Vibrio vulnificus Sepsis: A Potential Use of Extracorporeal Membrane Oxygenation

Necrotizing fasciitis caused by Vibrio vulnificus can rapidly progress to septic shock and death. Hence, early surgical debridement of the involved tissue is vital. However, this can be a challenging task due to the coagulopathy and unstable conditions often associated with these patients. Herein, we present a patient with necrotizing fasciitis caused by V. vulnificus who received extracorporeal membrane oxygenation (ECMO) support for refractory hypotension. After initiating ECMO, his vital signs stabilized, and lactate, C-reactive protein, and procalcitonin levels continued to decrease. He underwent several rounds of surgical debridement and vacuum-assisted drainage on both lower legs. On ECMO day 15, he was successfully weaned off the device and his condition was uneventful for several days. However, on the 24th day of intensive care unit (ICU), he was again placed on ECMO due to clinical deterioration. On ICU day 32, he underwent bilateral below-knee amputations due to delayed wound healing. Unfortunately, he subsequently developed multi-organ failure and died. Nonetheless, this case is instructive regarding the potential use of ECMO. We suggest that ECMO could provide the necessary time for sepsis patients to undergo aggressive medical and surgical interventions.

SEALONE (Safety and Efficacy of Coronary Computed Tomography Angiography with Low Dose in Patients Visiting Emergency Room) trial: study protocol for a randomized controlled trial

OBJECTIVE: Chest pain is one of the most common complaints in the emergency department (ED). Cardiac computed tomography angiography (CCTA) is a frequently used tool for the early triage of patients with low- to intermediate-risk acute chest pain. We present a study protocol for a multicenter prospective randomized controlled clinical trial testing the hypothesis that a low-dose CCTA protocol using prospective electrocardiogram (ECG)-triggering and limited-scan range can provide sufficient diagnostic safety for early triage of patients with acute chest pain. METHODS: The trial will include 681 younger adult (aged 20 to 55) patients visiting EDs of three academic hospitals for acute chest pain or equivalent symptoms who require further evaluation to rule out acute coronary syndrome. Participants will be randomly allocated to either low-dose or conventional CCTA protocol at a 2:1 ratio. The low-dose group will undergo CCTA with prospective ECG-triggering and restricted scan range from sub-carina to heart base. The conventional protocol group will undergo CCTA with retrospective ECG-gating covering the entire chest. Patient disposition is determined based on computed tomography findings and clinical progression and all patients are followed for a month. The primary objective is to prove that the chance of experiencing any hard event within 30 days after a negative low-dose CCTA is less than 1%. The secondary objectives are comparisons of the amount of radiation exposure, ED length of stay and overall cost. RESULTS AND CONCLUSION: Our low-dose protocol is readily applicable to current multi-detector computed tomography devices. If this study proves its safety and efficacy, dose-reduction without purchasing of expensive newer devices would be possible.

Rapid Response Systems Reduce In-Hospital Cardiopulmonary Arrest: A Pilot Study and Motivation for a Nationwide Survey / 대한중환자의학회지

BACKGROUND: Early recognition of the signs and symptoms of clinical deterioration could diminish the incidence of cardiopulmonary arrest. The present study investigates outcomes with respect to cardiopulmonary arrest rates in institutions with and without rapid response systems (RRSs) and the current level of cardiopulmonary arrest rate in tertiary hospitals. METHODS: This was a retrospective study based on data from 14 tertiary hospitals. Cardiopulmonary resuscitation (CPR) rate reports were obtained from each hospital to include the number of cardiopulmonary arrest events in adult patients in the general ward, the annual adult admission statistics, and the structure of the RRS if present. RESULTS: Hospitals with RRSs showed a statistically significant reduction of the CPR rate between 2013 and 2015 (odds ratio [OR], 0.731; 95% confidence interval [CI], 0.577 to 0.927; P = 0.009). Nevertheless, CPR rates of 2013 and 2015 did not change in hospitals without RRS (OR, 0.988; 95% CI, 0.868 to 1.124; P = 0.854). National university-affiliated hospitals showed less cardiopulmonary arrest rate than private university-affiliated in 2015 (1.92 vs. 2.40; OR, 0.800; 95% CI, 0.702 to 0.912; P = 0.001). High-volume hospitals showed lower cardiopulmonary arrest rates compared with medium-volume hospitals in 2013 (1.76 vs. 2.63; OR, 0.667; 95% CI, 0.577 to 0.772; P < 0.001) and in 2015 (1.55 vs. 3.20; OR, 0.485; 95% CI, 0.428 to 0.550; P < 0.001). CONCLUSIONS: RRSs may be a feasible option to reduce the CPR rate. The discrepancy in cardiopulmonary arrest rates suggests further research should include a nationwide survey to tease out factors involved in in-hospital cardiopulmonary arrest and differences in outcomes based on hospital characteristics.

Rapid Response Systems Reduce In-Hospital Cardiopulmonary Arrest: A Pilot Study and Motivation for a Nationwide Survey / 대한구급학회지

BACKGROUND: Early recognition of the signs and symptoms of clinical deterioration could diminish the incidence of cardiopulmonary arrest. The present study investigates outcomes with respect to cardiopulmonary arrest rates in institutions with and without rapid response systems (RRSs) and the current level of cardiopulmonary arrest rate in tertiary hospitals. METHODS: This was a retrospective study based on data from 14 tertiary hospitals. Cardiopulmonary resuscitation (CPR) rate reports were obtained from each hospital to include the number of cardiopulmonary arrest events in adult patients in the general ward, the annual adult admission statistics, and the structure of the RRS if present. RESULTS: Hospitals with RRSs showed a statistically significant reduction of the CPR rate between 2013 and 2015 (odds ratio [OR], 0.731; 95% confidence interval [CI], 0.577 to 0.927; P = 0.009). Nevertheless, CPR rates of 2013 and 2015 did not change in hospitals without RRS (OR, 0.988; 95% CI, 0.868 to 1.124; P = 0.854). National university-affiliated hospitals showed less cardiopulmonary arrest rate than private university-affiliated in 2015 (1.92 vs. 2.40; OR, 0.800; 95% CI, 0.702 to 0.912; P = 0.001). High-volume hospitals showed lower cardiopulmonary arrest rates compared with medium-volume hospitals in 2013 (1.76 vs. 2.63; OR, 0.667; 95% CI, 0.577 to 0.772; P < 0.001) and in 2015 (1.55 vs. 3.20; OR, 0.485; 95% CI, 0.428 to 0.550; P < 0.001). CONCLUSIONS: RRSs may be a feasible option to reduce the CPR rate. The discrepancy in cardiopulmonary arrest rates suggests further research should include a nationwide survey to tease out factors involved in in-hospital cardiopulmonary arrest and differences in outcomes based on hospital characteristics.

Air reduction of intussusception after abdominal blunt trauma and a literature review

The typical presentation of intussusception includes intermittent severe abdominal pain, vomiting, rectal bleeding, and the presence of an abdominal mass. We present a case of intussusception after abdominal blunt trauma along with a literature review. A 4-year-old girl was admitted to the emergency department after a bicycle accident. She complained of progressively worsening abdominal pain, but there was no vomiting, fever, bloody stool, or abdominal mass. She was finally diagnosed with traumatic intussusception by ultrasonography and treated with air reduction. Because the typical symptoms are unusual in traumatic intussusception, close attention must be paid to avoid a delayed diagnosis.

Immature Platelet Fraction in Septic Patients: Clinical Relevance of Immature Platelet Fraction is Limited to the Sensitive and Accurate Discrimination of Septic Patients From Non-Septic Patients, Not to the Discrimination of Sepsis Severity

BACKGROUND: The immature platelet fraction (IPF) reflects the degree of reticulated platelets. We evaluated performances of IPF as a biomarker for the discrimination of septic patients from non-septic patients and sepsis severity. METHODS: Total 312 patients admitted between March and July 2013 were enrolled and samples were obtained at admission. Lactate (LA), procalcitonin (PCT), C-reactive protein (CRP), immature granulocyte fraction (IG), immature reticulocyte fraction (IRF), and IPF were analyzed as sepsis biomarkers and their performances were compared. RESULTS: The performance of IPF (area under the curve [AUC]=0.868) in the discrimination of septic patients from non-septic patients was comparable to PCT/CRP/LA/IG (AUC=0.923/0.940/0.781/0.812, P=0.233/0.106/0.186/0.353, respectively), and was significantly better than the IRF (AUC=0.658, P=0.007). Sensitivity (89.8%, 95% confidence interval [CI] 84.9-99.8%) and accuracy (83.2%, 95% CI 78.8-90.0%) of IPF were the best among all biomarkers. The performance of IPF in discriminating septic patients from non-septic patients with local infection showed similar results. However, the IPF could not efficiently discriminate sepsis severity (AUC=0.599), similar to other biomarkers (AUC=0.519-0.752). CONCLUSIONS: The IPF possessed high sensitivity/accuracy in discriminating septic patients from non-septic patients, regardless of local infection status. However, the IPF did not efficiently discriminate sepsis severity. The clinical relevance of IPF as a sepsis biomarker is, therefore, limited to sensitive and accurate discrimination of septic patients from non-septic patients, not discrimination of sepsis severity.

Performance Evaluation of Five Different Disseminated Intravascular Coagulation (DIC) Diagnostic Criteria for Predicting Mortality in Patients with Complicated Sepsis

Disseminated intravascular coagulation (DIC) is a major complication in sepsis patients. We compared the performance of five DIC diagnostic criteria, focusing on the prediction of mortality. One hundred patients with severe sepsis or septic shock admitted to intensive care unit (ICU) were enrolled. Routine DIC laboratory tests were performed over the first 4 days after admission. The overall ICU and 28-day mortality in DIC patients diagnosed from five criteria (International Society on Thrombosis and Haemostasis [ISTH], the Japanese Association for Acute Medicine [JAAM], the revised JAAM [R-JAAM], the Japanese Ministry of Health and Welfare [JMHW] and the Korean Society on Thrombosis and Hemostasis [KSTH]) were compared. Both KSTH and JMHW criteria showed superior performance than ISTH, JAAM and R-JAAM criteria in the prediction of overall ICU mortality in DIC patients (odds ratio 3.828 and 5.181, P = 0.018 and 0.006, 95% confidence interval 1.256–11.667 and 1.622–16.554, respectively) when applied at day 1 after admission, and survival analysis demonstrated significant prognostic impact of KSTH and JMHW criteria on the prediction of 28-day mortality (P = 0.007 and 0.049, respectively) when applied at day 1 after admission. In conclusion, both KSTH and JMHW criteria would be more useful than other three criteria in predicting prognosis in DIC patients with severe sepsis or septic shock.

Effect of Alcohol on Death Rate in Organophosphate Poisoned Patients

PURPOSE: Many patients who are acutely poisoned with organophosphorus pesticides have co-ingested alcohol. The purpose of this study was to identify the factors that influence mortality in organophosphate intoxication and the differences between alcohol coingested patients and non-coingested patients, looking at vital signs, length of admission, cholinesterase activity, complications, and mortality. METHODS: All patients visiting one Emergency Department (ED) with organophosphate intoxication between January 2000 and December 2012 were reviewed retrospectively. The patients were divided into two groups, alcohol coingested group and non-coingested group. RESULTS: During the study period, 136 patients (alcohol coingested group, 95 patients; non-coingested group, 41 patients) presented to the ED with organophosphate intoxication. Seventy-one alcohol coingested patients (74.1%) vs. 16 non-coingested patients (39.0%) received endotracheal intubation, with results of the analysis showing a clear distinction between the two groups (p=0.001). Twenty-three alcohol coingested patients (24.2%) vs. 1 non-coingested patient (2.4%) required inotropics, indicating a significant gap (p=0.002). Twenty-eight alcohol coingested patients (29.5%) vs. 2 non-coingested patients (4.9%) died, with results of the analysis showing a clear distinction between the two groups (p=0.002). CONCLUSION: In cases of organophosphate intoxication, alcohol coingested patients tended to receive endotracheal intubation, went into shock, developed central nervous system complications, and more died.

Validation of Immature Granulocyte as a Predictor for the 28-Day Mortality in Patients with Severe Sepsis and Septic Shock

PURPOSE: Recently, several studies for immature granulocyte proportion (IG%) in patients with sepsis have revealed its association with diagnosis and prognosis of patients with sepsis. In this study, we enrolled patients with severe sepsis and septic shock and compared IG% with other biologic markers as a predictor of 28-day mortality. METHODS: This was a retrospective study for patients with severe sepsis and septic shock who were admitted to the emergency department of a tertiary care hospital for four-months. The IG% measured using Sysmex XE-2100 and other inflammatory markers, including C-reactive protein, lactate, and procalcitonin were evaluated and compared for 28-day mortality. RESULTS: A total of 85 patients with septic shock and 45 patients with severe sepsis were enrolled. In the non-survivors group (n=32, 24.6%), APACHE II score (p=0.017), use of continuous renal replacement therapy (CRRT) (p=0.002), and septic shock (p=0.009) were statistically higher compared with thesurvivors group. APACHE II score (Odd ratio [OR] 1.099, p=0.008) and IG% (> or =0.5%) (OR 3.568, p=0.036) predicted the 28-day mortality independently after adjusting SOFA score, septic shock,disseminated intravascular coagulopathy, use of CRRT, and gender. However, IG (> or =0.5%) had low specificity of 33.7% and positive predictive value (PPV) of 30.1% for 28-day mortality. CONCLUSION: IG% could be a useful biologic marker for prediction of 28-day mortality in patients with severe sepsis or septic shock. However, the limitation of low specificity and PPV must be considered in clinical use.

A Case of Pumpless Interventional Lung Assist Application in a Tuberculosis Destroyed Lung Patient with Severe Hypercapnic Respiratory Failure / 대한구급학회지

Pumpless extracorporeal interventional lung assist (iLA) is a rescue therapy allowing effective carbon dioxide removals and lung protective ventilator settings. Herein, we report the use of a pumpless extracorporeal iLA in a tuberculosis destroyed lung (TDL) patient with severe hypercapnic respiratory failures. A 35-year-old male patient with TDL was intubated due to CO2 retention and altered mentality. After 11 days, Ventilator Associated Pneumonia (VAP) had developed. Despite the maximal mechanical ventilator support, his severe respiratory acidosis was not corrected. We applied the iLA for the management of refractory hypercapnia with respiratory acidosis. This case suggests that the iLA is an effective rescue therapy for TDL patients with ventilator refractory hypercapnia.

Extracorporeal Membrane Oxygenation (ECMO) and Iliac Vein Injury / 대한구급학회지

The use of extracorporeal membrane oxygenation (ECMO) has increased after the 2009 pandemic H1N1 infections, and the ECMO-related complications have also increased. Specifically, the mechanical vessel injury due to catheter cannulation seems to be less frequent than other complications, but there is a risk of hemorrhagic shock which requires special attention. We experienced a case of successful management with graft stenting during ECMO operation for iliac vein injury. A 56-year-old female patient with non-small cell lung cancer developed endobronchial obstruction, and ECMO was applied for the ECMO-assisted rigid bronchoscopy. During catheter cannulation, hypovolemic shock was developed due to her right external iliac vein injury. We detected the hemorrhage with bedside ultrasound at an early stage and the hemorrhage was effectively managed with graft stenting on ECMO.

Clinical Characteristics and Worsening Prognosis for Undertriage Patients in the Emergency Department: A University Affiliated Hospital Observational Study

PURPOSE: Emergency department (ED) overcrowding is a common occurrence, and requires performance of appropriate triage to determine the priority for patient treatments. Undertriage, defined as inappropriate assignment of a low level of severity during triage, delays the initiation of treatment and may lead to deterioration of severely ill or injured patients. The aim of this observational study was to evaluate the clinical characteristics of undertriage patients and their risk exposure to a worsening prognosis. METHODS: Subjects were ED patients admitted to a university affiliated hospital from Jan 1, 2010 to Dec 31, 2010, and they were triaged according to the modified Canadian Triage and Acuity Scale. Patients who were initially categorized as non-emergency cases (scale 4 or 5) but later recategorized as emergency cases (scale 1 or 2) were defined as the undertriage group. Triage patients who did not receive a change of severity categorization were assigned to a low-acuity group for non-emergency cases, and a high-acuity group for emergency cases. The clinical characteristics and worsening prognosis of the undertriage group were compared with low- and high-acuity groups. Worsening prognosis included cardiac arrest and the admission to the intensive care unit. RESULTS: Patients in the undertriage group were 0.9% of the total study participants. The undertriage group predominantly included elderly males with head and neck injuries, or hemato-oncology diseases. Worsening prognosis was less likely in the undertriage group than in the high-acuity group, and more likely than in the low-acuity group. CONCLUSION: Undertriage was not common. However, worsening prognosis was very high in the undertriage group as compared to the low-acuity group. Prudential concern is required to avoid undertriage with the elderly, and patients with head and neck injuries, or hemato-oncology diseases.