PODCAST: EM Quick Hits 63 S-TEC and HUS, IM Epinephrine in OHCA, Dengue, Geriatric Trauma Imaging, TTP

Topics in this EM Quick Hits podcast

Stephen Freedman on pediatric bloody diarrhea, S-TEC and hemolytic uremic syndrome (1:06)

Justin Morgenstern on the evidence for IM epinephrine in out of hospital cardiac arrest (27:04)

Matthew McArther on recognition and ED management of dengue fever (33:56)

Andrew Petrosoniak on imaging decision making in trauma in older patients (47:20)

Brit Long & Michael Gotlieb on recognition and management of TTP (59:10)

Podcast production, editing and sound design by Anton Helman

Podcast content, written summary & blog post by Brandon Ng, edited by Anton Helman, March, 2025

Cite this podcast as: Helman, A. Freedman, S. Morgenstern, J. McArther, M. Petrosoniak, A. Long, B. Gotlieb, M. EM Quick Hits 63 – S-TEC and HUS, IM Epinephrine in OHCA, Dengue, Geriatric Trauma Imaging, TTP. Emergency Medicine Cases. March, 2025. https://emergencymedicinecases.com/em-quick-hits-march-2025/. Accessed March 12, 2025.

Pediatric bloody diarrhea: Shiga Toxin Producing E. Coli (S-TEC) and HUS

Consider obtaining a stool specimen or rectal swab in the ED for PCR testing (not culture) to detect S-TEC, Salmonella, Shigella, and Campylobacter.

Which children with bloody diarrhea require bloodwork? Most children with blood in stool do not require blood work. Indications for bloodwork include:

• Hemodynamic instability
• S-TEC is high on your differential (bloodwork may be useful as baseline)
• Recent travel with bloody diarrhea and fever
• Close contact with S-TEC cases (~10% household transmission rate)

When to suspect S-TEC?

• Severe crampy abdominal pain
• >15-20 small frequent, mucousy, bloody stools per day
• Low grade fever
• Signs of microangiopathy (e.g. petechiae, jaundice)
• Endemic area

Children generally do not require stool O&P for acute diarrhea but should be considered for chronic abdominal pain, chronic diarrhea, or failure to thrive.

When to test for C.difficile? There is a high carriage rate of C. diff (up to ~50% in children under 2 years old). Consider C. diff testing only in children with risk factors such as recent antibiotic use or hospitalization, or as a second line test on follow up if bloody diarrhea persists that is not noted to be from another bacterial etiology.

Why is it important to recognize S-TEC?

A complication of S-TEC infection is Hemolytic Uremic Syndrome (HUS), caused by Shiga toxin accumulation in the kidney which leads to the HUS triad: acute kidney injury, hemolysis, and thrombocytopenia.

• Shiga toxin 2 (STX2) is specifically associated with a 15-20% risk of HUS in children <5 years
  • HUS development increases risk of dialysis to 50-60% within 1 week
  • Differentiating between STX1 (<1% risk of HUS) and STX2 toxin can help risk-stratify patients

How to risk stratify a positive STEC result:

• Assume blood in stool to be STX2 producing STEC until proven otherwise (non-bloody STEC unlikely making Shiga toxin 2 and unlikely to cause HUS)
• Determine duration of diarrhea: HUS develops a median of 7 days after diarrhea onset
  • Diarrhea >10 days = low risk of HUS
• Determining if toxin result is STX2+ (high risk)

How to manage high risk patients with confirmed S-TEC?

• Manage dehydration aggressively (volume depletion is associated with adverse outcomes in HUS)
• Blood work q24h until reaching termination criteria (to allow early identification of microangiopathy)
  • Platelet drop is the earliest marker of evolving HUS
  • Consider LDH to identify hemolysis

Bottom line: Obtain early stool testing to identify children who present with bloody diarrhea for STEC, as some are at high risk of developing complications such as HUS. Children with STEC and their hydration status should be closely monitored.

Does IM epinephrine improve mortality in Out of Hospital Cardiac Arrest (OHCA)?

The Paper: Early intramuscular adrenaline administration is associated with improved survival from out-of-hospital cardiac arrest by Palatinus et al. Resuscitation 2024.

This before-and-after study suggests 5mg IM epinephrine may improve survival when given while IV access is being secured during an out of hospital cardiac arrest.

P: Adult patients with out-of-hospital cardiac arrest at a single-center urban setting

I (After): Single dose 5mg IM epinephrine prior IV/IO access in patient between November 2019 and May 2024

C (Before): Standard EMS ACLS protocol without IM epinephrine in patients between January 2010 and October 2019

O: Time to epi administration: 4.3 min in IM epi group, 7.8 min in standard protocol group. Survival to hospital admission: 37% in IM epi group, 32% in standard protocol group. Hospital survival: 11% in IM epi group, 7% in standard protocol group. Favourable neurological status at hospital discharge: 10% in IM epi group, 6% in standard protocol group

Limitations of this study:

• Before-and-after design (not an RCT), so confounding factors may have influenced results.
• Trial takes place over 14 years, and other aspects of care (e.g. temperature management, ECMO involvement, airway management techniques) may have changes over time which leads to improved outcomes in the after group.
  • An example of this is evidenced in the changes in baseline group data, where bystander CPR in the after group is ~14% higher and the age of patients are on average 3 years younger.
• Results are somewhat contrary to other RCT studies, which suggests epinephrine improves overall survival but not neurologic outcomes.

Bottom line: There is insufficient evidence for early administration of IM epinephrine compared to standard ACLS protocols to improve outcomes in out of hospital cardiac arrest.

Recognition and management of dengue fever

Background: Dengue is a mosquito-borne flavivirus (related to Zika and West Nile) which transmits between humans by mosquitos and is endemic to many countries in tropical and subtropical regions. It has been an increasing public health concern due to increasing outbreaks over the last decade. All 4 types of Dengue cause acute infections in humans but are not known to cause chronic infections.

75% of dengue infections are asymptomatic. However, 2-5% of dengue can progress to severe dengue.

There are 3 phases of dengue:

• Febrile phase (2-7 days): Rapid onset of high fever, headache, joint pain, eye pain, myalgia, nausea, vomiting, and a macular or maculopapular rash
  • Minor bleeding and petechiae can be elicited by the tourniquet test (inflation to halfway between SBP and DBP x5 min, +ve test if >10 new petechiae appear in a 1 square inch of skin within 1-2 min of cuff deflation)
  • Blood work may show leukopenia, thrombocytopenia, and mild liver enzyme elevation
  • Confirmatory test for dengue: Viral molecular testing and IgM levels (positive within 4-7 days of infection
• Critical phase (severe cases only): Plasma leakage leading to shock, bleeding, and organ dysfunction
  • Treatment: IV fluid resuscitation and supportive care
  • Risk factors for developing into severe dengue include extremes of age, immunosuppression, baseline comorbidities, and previous dengue infection
• Recovery phase: Resolution of plasma leakage and hemorrhage. Reabsorption of extravasated fluids
  • Some may develop further rashes or severe post-viral fatigue lasting days to weeks

The updated WHO classification system for dengue includes dengue, dengue with warning signs, or severe dengue. Consider the diagnosis of dengue in patients coming from an endemic area who have fever and any 2 of: aches, rash, nausea, vomiting, leukopenia, and positive tourniquet test.

Warning signs for severe dengue:

• Intense, continuous abdominal pain or tenderness
• Persistent vomiting
• Fluid accumulation (e.g. ascities, pleural effusion)
• Mucosal bleeding
• Altered mental status
• Hepatomegaly
• Rapidly rising hematocrit (in measures six hours apart)

Severe dengue = shock, clinically significant bleeding, or severe organ impairment

There are no specific therapies or vaccines for Dengue. Management is primarily supportive:

• Mild cases without warning signs: Outpatient management with close follow up, oral hydration, and tylenol for fever
  • Avoid NSAIDs and steroids (increased risk of GI bleed)
• Patients with risk factors (e.g. age, comorbidities): consider admission for close observation
• Patients with warning signs: admission and IV fluid resuscitation with isotonic fluids (10mL/kg over 1 hour) followed by reassessment and gradual tapering of IV fluids
• Severe dengue: ICU level care with large volume resuscitation (consider IV colloids if not responsive to aggressive crystalloids).
  • Prophylactic platelet transfusion is not recommended

Bottom line: Dengue is self-limiting in most cases but can be life-threatening in 2-5% of patients. Management of dengue is primarily supportive with oral or IV fluid resuscitation.

Imaging decision making in geriatric trauma

Falls in the older patient can result in significant injuries despite seemingly minor mechanisms.

• For example, there is a 2-5x higher mortality rate in patients >65 with rib fractures, with increasing mortality rates up to 11% and 35% with 6 and >8 rib fractures, respectively
• Pre-existing imaging rules may not have inclusion criteria that fit common patient presentations

CT imaging considerations:

• CT Head/C-Spine: Low threshold if patient >65, or other risk factors such as being on anticoagulants, or a high-risk mechanism.
  • Consider no imaging in patients without the main predictors of C-spine injury: head injury, neck pain, and increasing age
• CT Chest/Abdomen/Pelvis: Consider if chest X-ray is abnormal or if chest X-ray is normal but significant pain is present.
  • 16% of patients >65 and 28% of patient >85 with blunt chest trauma develop a complication such as pneumonia or respiratory failure
  • Chest X-rays demonstrate rib fractures only 50% of the time
  • There is conflicting data on whether older patients with radiographically occult injuries e.g. rib fractures require admission

The Eastern Association for the Surgery of Trauma (EAST) developed an imaging decision algorithm for the evaluation of blunt trauma patients > 65 although it has not received external validation. They recommend:

• CT Head and C-spine for all
• CT Chest/Abdomen/Pelvis if there are abnormal torso findings or high-risk factors
• Full CT spine if imaging Chest/Abdo/Pelvis: there is a 15% chance of another fracture elsewhere in the spine with any vertebral fracture

TTP recognition and management

Thrombotic thrombocytopenic purpura (TTP) is a rare but important disorder as it is associated with a mortality rate of 4-30%, even with early recognition and treatment.

In TTP, enzyme ADAMTS13 (responsible for cleaving large von Willebrand factor (vWF) becomes dysfunctional, resulting in large vWF multimers which accumulates in platelets, form clots, and destroys RBCs, leading to thrombocytopenia and hemolysis.

The classic pentad is seen in less than 7% of patients with TTP, and many of these findings can be transient:

• Thrombocytopenia (petechiae, purpura in ~50%)
• Microangiopathic hemolytic anemia
• Fever (seen in ~10% of cases)
• Neurologic symptoms
  • 40% of patients may have confusion, seizures, stroke
  • ~25% of patient swill have minor symptoms including headache or transient confusion
  • Up to 1/3 of patients have no neurologic symptoms
• Acute renal injury

Lab work for TTP

• End organ dysfunction: renal and liver dysfunction
• Hemolytic anemia: Hgb <10 g/dL, platelet <150 x10^9/L., ADAMTS13 activity level <10%, schistocyte on blood smear, increased indirect bilirubin, increased LDH, decreased haptoglobin, reticulocytosis
• Others: HIV, coagulation panel with normal INR, D-dimer, normal fibrinogen, troponin, urinalysis

A PLASMIC Score ≥5 has a 99% sensitivity and 57% specificity for TTP (incorporates elements including platelet count, hemolysis, active cancer, solid organ or stem cell transplant, low MCV, INR <1.5, Cr <2mg/dL).

Management of TTP:

1. Address the underlying etiology and end organ dysfunction
2. Consultation with hematology
3. Focused treatment of TTP: FFP (limited success), plasma exchange therapy, and methylprednisolone 1mg/kg/d. Rituximab (limited evidence from RCTs)
   1. Active bleeding is rare and transfusions are generally not necessary
   2. Platelet transfusions can be given if patients have major bleeding or are severely thrombocytopenic (current evidence suggests no significant impact on mortality)
   3. Low-molecular weight heparin + ASA for patients with platelet >50 as thromboembolic prophylaxis

Bottom line: Patients with TTP may not present with all elements of the classic pentad. Early identification and therapy can significantly improve mortality. The PLASMIC score can be used to assist in identifying patients with TTP.