Note to my readers: I recommend you go to the EMC Ep 204 podcast and show notes and listen to the podcast and review the show notes there. I only excerpt from resources I have reviewed because it helps me fix the learning in my memory.
And I also recommend reviewing:
- Nebulized nitroglycerin in the emergency department [Full-Text HTML] [Full-Text PDF]. Clin Exp Emerg Med. 2023 Jan 20;10(1):104–106. doi: 10.15441/ceem.22.411.
- I’ve included the article’s excellent summary table in today’s post after the chart “Recognition And Management Of High-Risk PE”.
- PulmCrit- Nebulized nitroglycerin: The stealth pulmonary vasodilator hiding under your nose?
December 21, 2019 by Josh Farkas - Links To Articles With Guidance On The Use Of High Flow Nasal Oxygen Cannulas
Posted on July 31, 2024 by Tom Wade MD - Linking To And Excerpting From PulmCrit’s “Bilevel Sequence Intubation (BSI) – The new standard”
Posted originally on May 14, 2025 by Tom Wade MD
Today, I review, link to, and excerpt from Emergency Medicine Cases‘ Ep 204 High Risk Pulmonary Embolism Management*. Podcast production, sound design & editing by Anton Helman; Voice editing by Braedon Paul. Written Summary and blog post by Sara Brade, edited by Anton Helman May, 202
*Helman, A. Morgenstern, J. Tillmann B. Westafer, L. High Risk Pulmonary Embolism Management. Emergency Medicine Cases. May, 2025 https://emergencymedicinecases.com/high-risk-pulmonary-embolism-management. Accessed May 18, 2025
All that follows is from the above resource.
Our patient from part 1 of this 2-part podcast series on pulmonary embolism management is now tanking. Recall she is a 30-year-old female on oral contraceptive pill who was satting 68% on room air when EMS picked her up after 6 hours of shortness of breath and a syncopal episode. She had an initial ECG and PoCUS suggestive of right heart strain, was started on IV heparin and had a saddle embolus on CTPA.
This time, however, instead of just being admitted to the ICU, she comes back from the donut of truth satting 88% on a non-rebreather with a blood pressure of 70/40 and now she’s altered. She now has a high-risk pulmonary embolism. How is this going to change our management?
These are the sickest of the PE patients – about 5-10% of all PE cases, but with a high mortality rate of 30-40% at 30 days. All of these patients, unless there are absolute contraindications, should be considered for timely thrombolysis, which is guideline recommended despite the evidence for mortality benefit being fair at best. Just like in intermediate-risk patients, high-risk PE patients are a heterogenous group ranging from the patient with persistent systolic BP under 90 and otherwise looking not bad, to the cardiac arrest patient. There are many nuances in the management of these patients in oxygenation and airway management, hemodynamic support, acid/base management, thrombolysis, catheter-directed therapies that we dive into with our guest experts Dr. Lauren Westafer, Dr. Bourke Tillmann and Dr. Justin Morgenstern…
Play the podcast in new window.
Part 1 of this 2-part podcast is on Intermediate Risk PE Risk Stratification and Management
Nebulized nitroglycerin in the emergency department [Full-Text HTML] [Full-Text PDF]. Clin Exp Emerg Med. 2023 Jan 20;10(1):104–106. doi: 10.15441/ceem.22.411.
Table 1.
Summary of the indications, pathophysiology, dose, and effect of nebulized nitroglycerinRV, right ventricular.
DOSING AND LIMITATIONS
For a critically ill or crashing patient, the dose of nitroglycerin is 5 mg nebulized over 20 to 30 minutes and repeated as necessary [1]. The main limitation is the volume of medication that will fit in the nebulizer, which is 3 to 5 mL. Some formulations of nitroglycerin have a 1 mg/mL concentration, which achieves the desired dosage of 5 mg. The studies mentioned above utilize lower doses such as 20 μg/kg or 2.5 μg/kg/min and demonstrate a statistically significant reduction in pulmonary vascular resistance [2,3]. Therefore, even if your department does not carry the 1 mg/mL concentration, it is reasonable to nebulize 3 to 5 mL of the dilute nitroglycerin (200 or 400 μg/mL) and repeat dosing as needed. The duration of action of nebulized nitroglycerin is approximately 20 to 30 minutes. Finally, inhaled nitroglycerin should be used with extreme caution in those with profound left ventricular failure, as the decrease in pulmonary vascular resistance results in an increase in left ventricular preload. This may worsen cardiogenic pulmonary edema.
PulmCrit- Nebulized nitroglycerin: The stealth pulmonary vasodilator hiding under your nose?
December 21, 2019 by Josh Farkas
How does PE kill our patients? The Pulmonary Embolism Spiral of Death
In pulmonary embolism, there is a physical obstruction (ie. clot) decreasing the flow from RV to LV. The RV is a weak muscle to begin with and this obstruction increases the pressure the RV has to pump against. As the RV starts to fail, it dilates and becomes even weaker resulting in hypotension. In an undifferentiated patient, we’re likely to start by giving them fluids. But the RV is very sensitive to fluids and as we give more fluids to a patient in this state, this causes the RV to dilate further. The RV then becomes ischemic and bows into the LV. The LV now can’t fill well because the RV is in the way and because there is limited flow coming from the pulmonary vessels. This worsens systemic hypotension. Further, vasoconstriction in areas of the lungs obstructed by clot causes hypoxemia, and hypoxemia worsens myocardial perfusion. This cycle is how our high risk pulmonary embolism patients die from if we don’t intervene.
Defining high-risk Pulmonary Embolism
High-risk pulmonary embolism, previously called massive PE, includes patients with hemodynamic instability due to PE delineated by one of the following:
- Cardiac arrest
- Presence of obstructive shock with a systolic BP <90mmHg or use of vasopressors to maintain a BP >90mmHg AND evidence of end-organ ischemia (ie. altered mental status, cool skin, oliguria, increased lactate)
- Persistent hypotension with a systolic BP <90mmHg or a drop of 40 mmHg or more for longer than 15 minutes not explained by an alternative cause (ie. sepsis, hemorrhage, etc).
Heterogeneity within the high-risk group informs management decisions
Like the intermediate-risk pulmonary embolism group, the high-risk group encompasses a wide spectrum of patients from cardiac arrest to a patient who looks okay clinically but has a mildly elevated lactate and a soft BP. Group these patients broadly into three groups to help guide management:
- Cardiac arrest
- Peri-arrest
- High-risk non-peri-arrest – note that oxygenation status alone is not captured in the classic high-risk definition schema but consider patients with high oxygen needs in this group.
Cardiac Arrest: Pulmonary Embolism Special Considerations
PE is estimated to cause 2-5% of all out-of-hospital cardiac arrests.
Presence of a shockable rhythm and no prior history of VTE has a NPV of 98% for excluding PE as the cause of cardiac arrest. PE most often causes PEA arrest.
When patients come to the emergency department in cardiac arrest, we often do not have a preceding diagnosis of PE. It may be reasonable to consider empiric thrombolytics in patients in PEA with multiple VTE risk factors, history of PE, history suspicious for PE (ie. sudden onset dyspnea pre-arrest), and/or signs on exam/ PoCUS of DVT. PoCUS can also be used to assess the heart/ IVC for signs of PE/ obstructive shock, but RV dilation alone is not an indication for thrombolytics. PoCUS pulse checks/ arterial line placement can also help differentiate true PEA from pseudo-PEA, and the latter can be managed as profound hypotension.
While some evidence suggests quite favourable outcomes for patients given thrombolytics in arrest due to PE (up to 87% alive at 3 months), these numbers may be inflated due to selection bias. When selecting cardiac arrest patients for thrombolytics, it is important to consider baseline status and duration of arrest. Thrombolytics will likely have a more favourable outcome in patients with a short duration of arrest and minimal downtime.
There is no high-quality evidence to guide us on how long to continue CPR for post-lytics. Some experts recommend at least 15 minutes, while European guidelines recommend 60-90 minutes. We know that, in general, outcomes are very poor for cardiac arrests of prolonged duration. These guidelines can make the decision about when to terminate resuscitation challenging.
Peri-arrest Pulmonary Embolism Initial Management
These sick peri-arrest patients often come to us undifferentiated, and so manage the initial stages like any other resuscitation. However, in undifferentiated shock patients, we should force ourselves to consider, “Could this be an RV issue?” Consider using PoCUS to perform a RUSH protocol to help narrow your differential diagnosis and to evaluate for signs of hemodynamically significant PE/ RV compromise. In patients with known PE, evaluate whether it’s the PE causing shock or if there is an alternate cause (ie. sepsis, hemorrhage). Avoid anchoring on the PE diagnosis as the sole cause of instability.
In peri-arrest PE patients, there are 3 key initial management considerations that differ from other resuscitations:
- Avoid intubation if possible – In general, try to avoid intubation/ NIV in these patients. The transition to positive pressure can worsen RV performance and lead to cardiac arrest. Flush rate non-rebreather/ high-flow nasal cannula (HFNC) are the preferred oxygenation strategies for these patients.
- Minimize PEEP – If these patients do end up requiring intubation/ NIV, excessive PEEP can further worsen RV hemodynamics. Optimal PEEP value for these patients is not known. Target the level of PEEP required to optimize gas exchange and minimize hypoxic vasoconstriction.
- Minimize IV fluids – Excessive IV fluid distends the RV and leads to worsening RV cardiac output, myocardial ischemia, and LV filling. Use IV fluids judiciously in these patients.
Peri-arrest Pulmonary Embolism Oxygenation and Airway Management
These sick peri-arrest patients often come to us undifferentiated, and so manage the initial stages like any other resuscitation. However, in undifferentiated shock patients, we should force ourselves to consider, “Could this be an RV issue?” Consider using PoCUS to perform a RUSH protocol to help narrow your differential diagnosis and to evaluate for signs of hemodynamically significant PE/ RV compromise. In patients with known PE, evaluate whether it’s the PE causing shock or if there is an alternate cause (ie. sepsis, hemorrhage). Avoid anchoring on the PE diagnosis as the sole cause of instability.
In peri-arrest PE patients, there are 3 key initial management considerations that differ from other resuscitations:
- Avoid intubation if possible – In general, try to avoid intubation/ NIV in these patients. The transition to positive pressure can worsen RV performance and lead to cardiac arrest. Flush rate non-rebreather/ high-flow nasal cannula (HFNC)* are the preferred oxygenation strategies for these patients.
- Minimize PEEP*– If these patients do end up requiring intubation/ NIV, excessive PEEP can further worsen RV hemodynamics. Optimal PEEP value for these patients is not known. Target the level of PEEP required to optimize gas exchange and minimize hypoxic vasoconstriction.
- Minimize IV fluids – Excessive IV fluid distends the RV and leads to worsening RV cardiac output, myocardial ischemia, and LV filling. Use IV fluids judiciously in these patients.
*Links To Articles With Guidance On The Use Of High Flow Nasal Oxygen Cannulas
Posted on July 31, 2024 by Tom Wade MD
**Linking To And Excerpting From PulmCrit’s “Bilevel Sequence Intubation (BSI) – The new standard”
Posted originally on May 14, 2025 by Tom Wade MD
