Podcast 1024: Caffeine Toxicity
Emergency Medical Minute
Contributor: Taylor Lynch, MD Educational Pearls: Excessive caffeine intake can be dangerous. For normal adults, the toxicity level starts at 1000mg, which is equivalent to about 10 cups of coffee or 5 celsius drinks. For normal adults, lethal levels are about 5-10 grams, which is equivalent to about 50-100 cups of coffee. Most of these outcomes are not from drinking caffeine, but instead concentrated caffeine pills. For children, toxic levels are 15mg per kg of the child. Within the last 10 years 20-40 deaths due to caffeine intake have been reported. This...
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Podcast 1023: Torsades de pointes
Emergency Medical Minute
Contributor: Aaron Lessen, MD Educational Pearls: Case review of a patient with recurrent episodes of syncope and shortness of breath, during which she is found to have intermittent runs of polymorphic ventricular tachycardia Torsades de pointes is polymorphic ventricular tachycardia occurring in the setting of a prolonged QT/QTc Risk of torsades increases substantially when QTc exceeds 500ms Causes: Common reversible causes include QT-prolonging medications, hypokalemia, hypomagnesemia, hypocalcemia, bradycardia, and structural heart disease Congenital causes of a prolonged QT...
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Podcast 1022: Emergent Dialysis
Emergency Medical Minute
Contributor: Taylor Lynch, MD Educational Pearls: When a patient who missed dialysis presents to the emergency department, our clinical concern is who needs to be admitted to the hospital for emergent dialysis and who can wait for their next regularly scheduled session. Dialysis sessions typically occur on Monday, Wednesday, and Friday, or Tuesday, Thursday, and Saturday. Acronym for indications for emergent dialysis: AEIOU Acidosis Patients may have an underlying cause for acidosis such as sepsis or DKA. Treat the underlying cause, but if the acidosis is unable to be...
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Podcast 1021: Pulmonary Edema From Naloxone Administration
Emergency Medical Minute
Contributor: Travis Barlock, MD Educational Pearls: What is pulmonary edema? Pulmonary edema is the accumulation of fluid initially in the interstitium of the lungs, that when severe enough can also accumulate in the alveolar air sacs. It develops when the rate of fluid filtration through the pulmonary vasculature out-paces the lymphatics ability to drain the fluid. There are 2 theories for what causes pulmonary edema in the setting of naloxone administration: catecholamine surge vs negative pressure/barotrauma Catecholamine Surge : Naloxone administration precipitates an...
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Podcast 1020: Benign Paroxysmal Positional Vertigo (BPPV)
Emergency Medical Minute
Contributor: Alec Coston, MD Educational Pearls: Benign Paroxysmal Positional Vertigo (BPPV) Common inner ear condition that can cause dizziness Diagnosis of BPPV can help to avoid admissions and extra imaging Three categories: positional, horizontal, and anterior Positional is the most common Dizziness is not a positive indicator, a torsional nystagmus must be induced Dix's hallpike maneuver is done to diagnose and an epley maneuver is then used for treatment Horizontal Usually determined to be the case if the vertigo seems positional and the dix...
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Podcast 1019: Trauma Blunt Cardiovascular Injuries (BCVI)
Emergency Medical Minute
Contributor: Aaron Lessen, MD Educational Pearls: Blunt cerebrovascular injury (BCVI) BCVI is a traumatic injury to the carotid or vertebral arteries Patients may initially have no neurologic symptoms In some cases, a thrombus can form at the site of the injury and later cause ischemic stroke, sometimes hours after the original trauma CT angiography (CTA) of the neck is a useful screening tool for BCVI HIstorically, CTA was reserved for patients with high-risk mechanisms or neurologic symptoms CTA screening has expanded as understanding of BCVIs and their prevention...
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Podcast 1018: Occult Ventricular Fibrillation on Echocardiography
Emergency Medical Minute
Contributor: Aaron Lessen, MD Educational Pearls: Big question in cardiac arrest: is the rhythm shockable? Shockable: ventricular fibrillation (VF) and pulseless ventricular tachycardia Non-shockable: asystole and pulseless electrical activity (PEA) Rhythm classification is typically based on ECG, but echocardiography can directly visualize myocardial fibrillation Occult VF: a rhythm that appears non-shockable on ECG but demonstrates VF on echocardiography A 2025 multicenter prospective study looked at 811 patients with out-of-hospital cardiac arrest 5.3% had occult VF...
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Podcast 1017: CPR Hand Placement
Emergency Medical Minute
Contributor: Taylor Lynch, MD Educational Pearls: CPR is an important life-saving measure designed for anyone to perform. Chest compressions works by two mechanisms: Cardiac pump: Direct squeezing of the heart Thoracic pump: Increasing intrathoracic pressure, causing increased blood flow Proper hand placement per current AHA guidelines: Hands are placed in the center of the chest, on the lower half of the sternum A recent study challenged this approach, using TEE during chest compressions to visualize the cardiac structures being compressed. They found...
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Podcast 1016: Hypokalemia
Emergency Medical Minute
Contributor: Meghan Hurley, MD Educational Pearls: What is hypokalemia? Hypokalemia is when the measured blood level of potassium falls below 3.5 mEq/L (normal 3.5 - 5.2 mEq/L). Can generally be considered in mild (3.0 - 3.5 mEq/L); moderate (2.5 - 2.9 mEq/L); and severe (<2.5 mEq/L) categories with differing treatment goals based on levels. Should be noted that blood levels of potassium can be low while total body potassium is normal due to intracellular shift by certain agents like β-2 agonists (e.g. Albuterol) or insulin. There is no appreciable loss of insulin despite...
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Podcast 1015: Calcium in Hyperkalemia
Emergency Medical Minute
Contributor: Meghan Hurley, MD Educational Pearls: What is hyperkalemia? Hyperkalemia is when the measured blood level of potassium reaches above 5.2 - 5.5 mEq/L (normal 3.5 - 5.2 mEq/L). What are common causes of hyperkalemia? Chronic or acute kidney disease. Medications that impact the Renin-Angiotensin-Aldosterone-System (RAAS). Hypoaldosteronism and primary adrenal insufficiency (Addison’s Disease). What are concerns of hyperkalemia? The biggest concern with hyperkalemia is the impact on the cardiac conduction system. At differing levels of...
info_outlineContributor: Travis Barlock, MD
Educational Pearls:
Caffeine Geography and Types:
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Caffeine is found throughout the world and has evolved independently in various plants that are not evolutionarily related through direct lineage, but rather demonstrate convergent evolution (i.e. different species evolve the same traits).
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These plants use caffeine as an insecticide.
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Examples of caffeine sources include coffee, tea, yerba-mate, guaraná, cacao, and yaupon holly.
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Roughly 85% of Americans are estimated to consume caffeine daily.
Caffeine Pharmacology in Humans:
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In humans, caffeine is a nonselective competitive antagonist (blocker) of adenosine receptors (A1 and A2A).
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During waking hours, neuronal metabolic activity consumes ATP, and a byproduct of ATP hydrolysis is created: adenosine.
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Adenosine proceeds to build a “sleep pressure”.
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Acting on A1 and A2A adenosine receptors to induce sleep (on A1, it suppresses neuronal “wakefulness” and on A2A it is believed to be an inducer of sleep).
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Caffeine, by blocking those receptors, blunts sleep induction and feelings of being tired.
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Caffeine has a half-life of around 6 hours, and a quarter life of approximately 12 hours, which is when the caffeine will off-load and adenosine can once again occupy those receptors, potentially causing a “crash”.
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Thus, for shift-workers, it is important to time caffeine intake roughly 10 hours before target bed time.
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Caffeine exerts other effects on the body.
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It is methylxanthine similar to theophylline, which works as a bronchodilator (via phosphodiesterase and adenosine pathways). Caffeine has clinical use to promote bronchodilation in pre-term infants.
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Caffeine exerts diuretic effects as well (blocking proximal renal tubule reabsorption).
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Recent ingestion of caffeine may blunt therapeutic use of adenosine in patients with SVT.
Key Takeaway?
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Caffeine exerts a wide variety of effects beyond making us feel more awake. It has cardiovascular, pulmonary, and renal implications in its pharmacodynamics.
References
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Benarroch EE. Adenosine and its receptors: multiple modulatory functions and potential therapeutic targets for neurologic disease. Neurology. 2008;70(3):231-236. doi:10.1212/01.wnl.0000297939.18236.ec
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Mitchell DC, Knight CA, Hockenberry J, Teplansky R, Hartman TJ. Beverage caffeine intakes in the U.S. Food Chem Toxicol. 2014;63:136-142. doi:10.1016/j.fct.2013.10.042
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Bruschettini M, Brattström P, Russo C, Onland W, Davis PG, Soll R. Caffeine dosing regimens in preterm infants with or at risk for apnea of prematurity - Bruschettini, M - 2023 | Cochrane Library. Accessed May 23, 2026. https://www.cochranelibrary.com/cdsr/doi/10.1002/14651858.CD013873.pub2/full?cookiesEnabled
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Huang R, O’Donnell AJ, Barboline JJ, Barkman TJ. Convergent evolution of caffeine in plants by co-option of exapted ancestral enzymes. Proc Natl Acad Sci U S A. 2016;113(38):10613-10618. doi:10.1073/pnas.1602575113
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Cabalag MS, Taylor DM, Knott JC, Buntine P, Smit D, Meyer A. Recent caffeine ingestion reduces adenosine efficacy in the treatment of paroxysmal supraventricular tachycardia. Acad Emerg Med. 2010;17(1):44-49. doi:10.1111/j.1553-2712.2009.00616.x
Summarized by Dan Orbidan, OMS2 | Edited by Dan Orbidan & Ahmed Abdel-Hafiz, NREMT-P
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