Contributor: Megan Hurley MD

Educational Pearls:

What is the mediastinum?

• The thoracic cavity is separated into different compartments by membranes

• The lungs exist in their own pleural cavities, and the mediastinum is everything in between

• The mediastinum extends from the sternum to the thoracic vertebrae and includes the heart, the aorta, the trachea, the esophagus, the thymus, as well as many lymph nodes and nerves.

What is a pneumomediastinum?

• Air in the mediastinum

How can pneumomediastinum be categorized?

• Traumatic

• • Ex. Stab wound to the trachea

  • Ex. Boerhaave’s Syndrome of the esophagus, possibly from an endoscopic procedure. This mechanism in particular is a higher risk of infection because not only air but food can accumulate in the mediastinum

  • Ex. Intubation with a bougie

  • These will likely need surgical repair

• Nontraumatic

• • Ex. Forceful inhalation causing microperforations in the trachea. Possibly while inhaling something like drugs

  • Ex. Bad asthma for similar reasons

  • Ex. Gas forming bacteria

What happens if you use positive pressure ventilation on a patient with a hole in their trachea?

• The positive pressure will force extra air into the mediastinum

• The air will move between the layers of subcutaneous tissue and can track up into the neck and face regions recognized as crepitus on exam

• This can also cause a tension pneumomediastinum in which the air pressure in the compartment constricts the heart, impeding its ability to fill during diastole

• These patients can undergo bronchoscopy because that procedure does not require positive pressure and will not worsen the condition. Endoscopies do require positive pressure so endoscopies are not an option

How is a tension pneumomediastinum treated?

• By inserting a needle into the space from below the xiphoid process to allow the air to escape, similar to a pericardiocentesis

• As a temporizing measure, if the hole is high enough in the trachea, the intubation can be continued by deliberately pushing the endotracheal tube into the right main bronchus, creating a seal, and only ventilating the right lung while the patient heads to surgery. This is called right-mainstemming.

References

1. Clancy DJ, Lane AS, Flynn PW, Seppelt IM. Tension pneumomediastinum: A literal form of chest tightness. J Intensive Care Soc. 2017 Feb;18(1):52-56. doi: 10.1177/1751143716662665. Epub 2016 Aug 3. PMID: 28979537; PMCID: PMC5606356.

2. Grewal, J., & Gillaspie, E. A. (2024). Pneumomediastinum. Thoracic surgery clinics, 34(4), 309–319. https://doi.org/10.1016/j.thorsurg.2024.06.001

3. Underner, M., Perriot, J., & Peiffer, G. (2017). Pneumomédiastin et consommation de cocaïne [Pneumomediastinum and cocaine use]. Presse medicale (Paris, France : 1983), 46(3), 249–262. https://doi.org/10.1016/j.lpm.2017.01.002

Summarized by Jeffrey Olson, MS3 | Edited by Meg Joyce & Jorge Chalit, OMS3

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Contributor: Ricky Dhaliwal MD

Educational Pearls:

• Etomidate was previously the drug of choice for rapid sequence intubation (RSI)

• • However, it carries a risk of adrenal insufficiency as an adverse effect through inhibition of mitochondrial 11-β-hydroxylase activity

• A recent meta-analysis analyzing etomidate as an induction agent showed the following:

• • 11 randomized-controlled trials with 2704 patients

  • Number needed to harm is 31; i.e. for every 31 patients that receive etomidate for induction, there is one death

  • The probability of any mortality increase was 98.1%

• Ketamine is preferable due to a better adverse effect profile

• • Laryngeal spasms and bronchorrhea are the most common adverse effects after IV push

  • Beneficial effects on hemodynamics via catecholamine surge, albeit not as pronounced in shock patients

• 2023 meta-analysis compared ketamine and etomidate for RSI

• • Ketamine’s probability of reducing mortality is cited as 83.2%

  • Overall, induction with ketamine demonstrates a reduced risk of mortality compared with etomidate

• The dosage of each medication for induction

• • Etomidate: 20 mg based on 0.3 mg/kg for a 70 kg adult

  • Ketamine: 1-2 mg/kg (or 0.5-1 mg/kg in patients with shock)

• Patients with asthma and/or COPD also benefit from ketamine induction due to putative bronchodilatory properties

References

1. Goyal S, Agrawal A. Ketamine in status asthmaticus: A review. Indian J Crit Care Med. 2013;17(3):154-161. doi:10.4103/0972-5229.117048

2. Koroki T, Kotani Y, Yaguchi T, et al. Ketamine versus etomidate as an induction agent for tracheal intubation in critically ill adults: a Bayesian meta-analysis. Crit Care. 2024;28(1):1-9. doi:10.1186/s13054-024-04831-4

3. Kotani Y, Piersanti G, Maiucci G, et al. Etomidate as an induction agent for endotracheal intubation in critically ill patients: A meta-analysis of randomized trials. J Crit Care. 2023;77(April 2023):154317. doi:10.1016/j.jcrc.2023.154317

Summarized & Edited by Jorge Chalit, OMS3

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Contributor: Aaron Lessen MD

Educational Pearls:

• Pregnant patients at high risk of cardiac arrest, in cardiac arrest, or in extremis require special care

• A useful mnemonic to recall the appropriate management of critically ill pregnant patients is TOLDD

• T: Tilt the patient to the left lateral decubitus position

• • This position relieves pressure exerted from the uterus onto the inferior vena cava, which reduces cardiac preload

  • If the patient is receiving CPR, an assistant should displace the uterus manually from the IVC towards the patient’s left side

• O: Administer high-flow adjunctive oxygen

• L: Lines should be placed above the diaphragm

• • Lines below the diaphragm are ineffective due to uterine compression of the IVC

  • May consider humeral interosseous line vs. internal jugular or subclavian central line

• D: Dates should be estimated

• • > 20 weeks, can consider a resuscitative hysterotomy (previously known as perimortem c-section) to improve chances of survival

  • The uterus is palpable at the umbilicus at 20 weeks and 1 cm superior to the umbilicus for every week thereafter

• D: Call the labor and delivery unit for additional help

References

1. ACOG Practice Bulletin No. 211 Summary: Critical Care in Pregnancy. Obstetrics & Gynecology. 2019;133(5)

2. Fujita N, Higuchi H, Sakuma S, Takagi S, Latif MAHM, Ozaki M. Effect of Right-Lateral Versus Left-Lateral Tilt Position on Compression of the Inferior Vena Cava in Pregnant Women Determined by Magnetic Resonance Imaging. Anesth Analg. 2019;128(6):1217-1222. doi:10.1213/ANE.0000000000004166

3. Jeejeebhoy FM, Zelop CM, Lipman S, et al. Cardiac Arrest in Pregnancy. Circulation. 2015;132(18):1747-1773. doi:doi:10.1161/CIR.0000000000000300

4. Singh, Ajay; Dhir, Ankita; Jain, Kajal; Trikha, Anjan1. Role of High Flow Nasal Cannula (HFNC) for Pre-Oxygenation Among Pregnant Patients: Current Evidence and Review of Literature. Journal of Obstetric Anaesthesia and Critical Care 12(2):p 99-104, Jul–Dec 2022. | DOI: 10.4103/JOACC.JOACC_18_22

Summarized & Edited by Jorge Chalit, OMS3

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Contributor: Travis Barlock MD

Educational Pearls:

What is the ST segment?

• The ST segment on an ECG represents the interval between the end of ventricular depolarization (QRS) and the beginning of ventricular repolarization (T-wave).

• It should appear isoelectric (flat) in a normal ECG.

What if the ST segment is elevated?

• This is evidence that there is an injury that goes all the way through the muscular wall of the heart (transmural)

• This is very concerning for a heart attack (STEMI) but can be occasionally caused by other pathology, such as pericarditis

What if the ST segment is depressed?

• This is evidence that only the innermost part of the muscular wall of the heart is becoming ischemic

• This has a much broader differential and includes a partial occlusion of a coronary artery but also any other stress on the body that could cause a supply-and-demand mismatch between the oxygen the coronaries can deliver and the oxygen the heart needs

• This is called subendocardial ischemia

What else should you look for in the ECG to identify subendocardial ischemia?

• The ST-depressions should be at least 1 mm

• The ST depressions should be present in leads I, II, V4-6 and a variable number of additional leads.

• There is often reciprocal ST elevation in aVR > 1 mm

The most important thing to remember when you see subendocardial ischemia is…history

• Still, keep all cardiac causes on your differential, such as unstable angina, stable angina, Prinzmetal angina, etc.

• Also consider a wide array of non-cardiac causes such as severe anemia, severe hypertension, pulmonary embolism, COPD, severe pneumonia, sepsis, shock, thyrotoxicosis, stimulant use, DKA, or any other state that lead to reduced oxygen supply to the subendocardium and/or increased myocardial oxygen demand.

References

1. Birnbaum, Y., Wilson, J. M., Fiol, M., de Luna, A. B., Eskola, M., & Nikus, K. (2014). ECG diagnosis and classification of acute coronary syndromes. Annals of noninvasive electrocardiology : the official journal of the International Society for Holter and Noninvasive Electrocardiology, Inc, 19(1), 4–14. https://doi.org/10.1111/anec.12130

2. Buttà, C., Zappia, L., Laterra, G., & Roberto, M. (2020). Diagnostic and prognostic role of electrocardiogram in acute myocarditis: A comprehensive review. Annals of noninvasive electrocardiology : the official journal of the International Society for Holter and Noninvasive Electrocardiology, Inc, 25(3), e12726. https://doi.org/10.1111/anec.12726

3. Cadogan, E. B. a. M. (2024, October 8). Myocardial Ischaemia. Life in the Fast Lane • LITFL. Retrieved December 7, 2024, from https://litfl.com/myocardial-ischaemia-ecg-library/#:~:text=ST%20depression%20due%20to%20subendocardial,left%20main%20coronary%20artery%20occlusion.

Summarized by Jeffrey Olson, MS3 | Edited by Meg Joyce & Jorge Chalit, OMS3

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Contributor: Alec Coston MD

Educational Pearls:

• Causes of seizures in a fairly well-appearing child with diarrhea:

• • Electrolyte abnormalities: hypocalcemia, hyponatremia

  • • Also hyperkalemia which causes arrhythmias and syncope - can appear like seizures

  • Hypoglycemia

• If the child has diarrhea and appears very sick, differential diagnosis may include:

• • Hemolytic uremic syndrome (HUS):

  • • simultaneous occurrence of microangiopathic hemolytic anemia, thrombocytopenia, and acute kidney injury

    • Typically caused by Shiga-like toxin producing Escherichia coli (also known as EHEC, or enterohemorragic E. coli)

    • One of the main causes of acute kidney injury in children

  • Toxic ingestions such as salicylates, lead, or iron

• In this case, the child had a seizure but appeared well and was afebrile:

• • Consult with neurology led to a diagnosis of benign convulsions with mild gastroenteritis (CwG)

  • • First identified in 1982 in Japan

    • Viral gastroenteritis with diarrhea and convulsions but does not include fever, severe dehydration, or electrolyte abnormalities

    • Uncommon illness caused by rotavirus and norovirus pathogens

  • Criteria for discharge is similar to a febrile seizure - the patient had one seizure that lasted less than 15 minutes and he quickly returned to his baseline, so he was able to be safely discharged home

  • • This diagnosis does not predispose him to epilepsy later in life

References

1. Lee YS, Lee GH, Kwon YS. Update on benign convulsions with mild gastroenteritis. Clin Exp Pediatr. 2022 Oct;65(10):469-475. doi: 10.3345/cep.2021.00997. Epub 2021 Dec 27. PMID: 34961297; PMCID: PMC9561189.

2. Mauritz M, Hirsch LJ, Camfield P, et al. Acute symptomatic seizures: an educational, evidence-based review. Epileptic Disorders. 2200;1(1). doi:https://doi.org/10.1684/epd.2021.1376

3. ‌Noris, Marina*; Remuzzi, Giuseppe*, †. Hemolytic Uremic Syndrome. Journal of the American Society of Nephrology 16(4):p 1035-1050, April 2005. | DOI: 10.1681/ASN.2004100861

Summarized by Meg Joyce, MS1 | Edited by Meg Joyce & Jorge Chalit, OMS3

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Contributor: Aaron Lessen MD

Educational Pearls:

• Induction agent selection during rapid sequence intubation involves accounting for hemodynamic stability in the post-intubation setting

• Many emergency departments use ketamine or etomidate

• A recent study sought to explore the rates of post-induction hypotension of ketamine compared with propofol

  • Single center retrospective cohort study of patients between 2018-2021

• Ketamine and propofol were both significantly associated with post-induction hypotension

  • Ketamine adjusted odds ratio = 4.50

  • Propofol adjusted odds ratio = 4.88

  • 50% of patients became hypotensive after induction with either propofol or ketamine

• These findings suggest post-induction hypotension is mainly due to sympatholysis rather than the choice of agent itself

References

1. Tamsett Z, Douglas N, King C, et al. Does the choice of induction agent in rapid sequence intubation in the emergency department influence the incidence of post-induction hypotension?. Emerg Med Australas. 2024;36(3):340-347. doi:10.1111/1742-6723.14355

Summarized & Edited by Jorge Chalit, OMS3

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Contributor: Aaron Lessen MD

Educational Pearls:

Can opioids cause cardiac arrest?

• Opioids can cause respiratory suppression and the subsequent low oxygen levels can lead to arrhythmias and eventually cardiac arrest.

• In 2023, 17% of out-of-hospital cardiac arrests (OHCA) were attributable to opioids.

Given that this is a rising cause of cardiac arrest, should we just treat all cardiac arrest with naloxone (Narcan)?

• Naloxone is correlated with an increased chance of return of spontaneous circulation (ROSC)

• Additionally, a wide variety of individuals can be exposed to opioids and therefore opioid overdose should be considered in all cases of OHCA

But does naloxone improve neurologic outcomes?

• Yes, naloxone, especially when given early on in the resuscitation can improve neuro outcomes

What is the dose?

• 2-4 mg IN/IV depending on access.

• High suspicion for opioid overdose consider going with an even higher dose such as 4-8 mg IN/IV

References

1. Orkin, A. M., & Dezfulian, C. (2024). Recognizing the fastest growing cause of out-of-hospital cardiac arrest. Resuscitation, 198, 110206. https://doi.org/10.1016/j.resuscitation.2024.110206

2. Quinn, E., & Du Pont, D. (2024). Naloxone administration in out-of-hospital cardiac arrest: What's next?. Resuscitation, 201, 110307. https://doi.org/10.1016/j.resuscitation.2024.110307

3. Saybolt, M. D., Alter, S. M., Dos Santos, F., Calello, D. P., Rynn, K. O., Nelson, D. A., & Merlin, M. A. (2010). Naloxone in cardiac arrest with suspected opioid overdoses. Resuscitation, 81(1), 42–46. https://doi.org/10.1016/j.resuscitation.2009.09.016

4. Wampler D. A. (2024). Naloxone in Out-of-Hospital Cardiac Arrest-More Than Just Opioid Reversal. JAMA network open, 7(8), e2429131. https://doi.org/10.1001/jamanetworkopen.2024.29131

Summarized by Jeffrey Olson, MS3 | Edited by Meg Joyce MS1 & Jorge Chalit, OMS3

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Contributor: Aaron Lessen MD

Educational Pearls:

• A study evaluated the patient-care impact and financial costs of holding patients in the ED, a nationwide issue

• • Prospective, observational study of acute stroke management

  • Conducted at a large urban, comprehensive stroke center

• The study evaluated patients in multiple categories:

1. admitted to med/surg

2. admitted to med/surg but held in the ED

3. admitted to the ICU

4. Admitted to ICU but held in the ED

• Examined the amount of time nurses and providers spent with each patient

• • This was analyzed in conjunction with the knowledge of each providers’ salaries and the overhead costs of the med/surg unit, ICU, and ED

• Conclusions:

• • Patients who required med/surg inpatient care but who were held in the ED resulted in a doubled daily cost

  • • $1856 for med/surg inpatient boarding vs $993 for med/surg inpatient care

  • Patients who required ICU care but who were held in the ED also resulted in an increased daily cost, but this difference was not as large

  • • $2267 for ICU inpatient boarding vs $2165 for ICU care

• Holding in the ED negatively impacts patients since they receive less time from providers

• Holding also results in increased financial costs

References

1. Canellas MM, Jewell M, Edwards JL, Olivier D, Jun-O’Connell AH, Reznek MA. Measurement of Cost of Boarding in the Emergency Department Using Time-Driven Activity-Based Costing. Annals of emergency medicine. Published online May 1, 2024. doi:https://doi.org/10.1016/j.annemergmed.2024.04.012

Summarized by Meg Joyce, MS1 | Edited by Meg Joyce & Jorge Chalit, OMS3

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