Emergency Medical Minute

Contributor: Travis Barlock, MD
Educational Pearls:
D-dimer: fibrin degradation product used to evaluate for clot formation and breakdown Threshold: Elevated D-dimer indicates recent or ongoing intravascular coagulation and fibrinolysis

YEARS score: algorithm to assess PE risk using three clinical criteria Criteria: signs of DVT, hemoptysis, and PE as the most likely diagnosis
YEARS score of 0 with D-dimer YEARS score of ≥1 with D-dimer A study found that YEARS score accurately predicted the presence or absence of PE in 80% of enrolled patients with 90% sensitivity and 65% specificity

D-dimer may also help exclude aortic dissection: Aortic Dissection Detection Risk Score (ADD-RS) When ADD-RS = 0 or 1 and D-dimer When ADD-RS >1, patients are considered high probability for aortic dissection and CT should be performed

References
Fayiad, H., Moussa, H., Nosair, Y. et al. Predictive accuracy of years score in diagnosis of pulmonary embolism. Egypt J Bronchol 18, 18 (2024). https://doi.org/10.1186/s43168-024-00269-y
Weitz JI, Fredenburgh JC, Eikelboom JW. A Test in Context: D-Dimer. J Am Coll Cardiol. 2017 Nov 7;70(19):2411-2420. doi: 10.1016/j.jacc.2017.09.024. PMID: 29096812.
Yichao Ma,Zhenjiang Ding,Yunong Zhao,Paijiao Zhang,Bo Du,Ye Shen,Junmei Hu,Luqi Zhu,Honghong Zhao,Chunrong Jin,Yuhong Wang,Lizhen Gao,Research progress on multi-marker detection technology for cardiovascular diseases (review), Journal of Electroanalytical Chemistry, 1008, (119969), (2026).
Summarized by Meg Joyce, MS2 | Edited by Meg Joyce & Jorge Chalit, OMS4
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Contributor: Taylor Lynch MD
Educational Pearls:
Melatonin is an endogenous hormone released primarily by the pineal gland Also released by extrapineal regions in the retina, the GI tract, and some immune cells

Peak secretion occurs at night and is suppressed during the day Secretion and production decrease with age
Older patients experience the greatest improvement in sleep latency and sleep quality

Mechanism of action in the suprachiasmatic nucleus of the hypothalamus MT1 receptor Reduces normal firing

MT2 receptor Shifts the circadian rhythm


FDA approved for insomnia Decreases sleep latency by 7 minutes
Increases total sleep time by 8 minutes

FDA approved for circadian sleep-wake disorders Jet lag Most effective in west-to-east travel
Best if crossing at least 5 time zones

Shift work A study examined ED physicians and nurses with rotating shifts
Modest increase in deep sleep percentage
No difference in cognition or reaction time the day after taking melatonin
Nurses on rotating night shifts experienced increased total sleep time by 20 minutes


Dosing 0.5 - 3 mg is the most evidence-based dosing
Higher doses increase the risk of rebound grogginess but do not improve outcomes

References
Ahmad SB, Ali A, Bilal M, et al. Melatonin and Health: Insights of Melatonin Action, Biological Functions, and Associated Disorders. Cell Mol Neurobiol. 2023;43(6):2437-2458. doi:10.1007/s10571-023-01324-w
Herxheimer A, Petrie KJ. Melatonin for the prevention and treatment of jet lag. Cochrane Database Syst Rev. 2002;(2):CD001520. doi:10.1002/14651858.CD001520
Morgenthaler TI, Lee-Chiong T, Alessi C, Friedman L, Aurora RN, Boehlecke B, Brown T, Chesson AL Jr, Kapur V, Maganti R, Owens J, Pancer J, Swick TJ, Zak R; Standards of Practice Committee of the American Academy of Sleep Medicine. Practice parameters for the clinical evaluation and treatment of circadian rhythm sleep disorders. An American Academy of Sleep Medicine report. Sleep. 2007 Nov;30(11):1445-59. doi: 10.1093/sleep/30.11.1445. Erratum in: Sleep. 2008 Jul 1;31(7):table of contents. PMID: 18041479; PMCID: PMC2082098.
Thottakam BMVJ, Webster NR, Allen L, Columb MO, Galley HF. Melatonin Is a Feasible, Safe, and Acceptable Intervention in Doctors and Nurses Working Nightshifts: The MIDNIGHT Trial. Front Psychiatry. 2020;11:872. Published 2020 Aug 27. doi:10.3389/fpsyt.2020.00872
Summarized and edited by Jorge Chalit, OMS4
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Contributor: Travis Barlock, MD
Educational Pearls: 
Foul-smelling urine and cloudy urine are commonly misinterpreted as indicators of a UTI. However, these findings alone are not diagnostic.
Criteria for UTI: Presence of localized urinary symptoms:
Suprapubic pain
Dysuria
Hesitancy
Urgency
Urinalysis with WBC > 10
Urine culture with > 100,000 CFU/mL

Colonization differs from infection - many patients harbor asymptomatic bacteria but do not have a true infection.
Consequences of overtreatment One review showed 45% of patients treated with antibiotics for a presumed UTI actually had asymptomatic bacteriuria and were incorrectly treated.
Unnecessary antibiotic treatment can have deleterious effects on the gut microbiome, increasing the risk of multidrug-resistant infections.
Another problem with overdiagnosing UTI is missing the real diagnosis by explaining symptoms away as "just a UTI."

Be mindful of the risk of overtesting versus not testing at all. Clinicians must navigate a balance between moving patients efficiently through the ER and testing appropriately when a UTI is truly suspected.

References:
Baghdadi JD, Korenstein D, Pineles L, et al. Exploration of primary care clinician attitudes and cognitive characteristics associated with prescribing antibiotics for asymptomatic bacteriuria. JAMA Netw Open. 2022;5(5):e2214268. doi:10.1001/jamanetworkopen.2022.14268
Colgan R, Williams M. Acute uncomplicated urinary tract infections in adults. Am Fam Physician. 2024;109(2):167-174. Accessed February 21, 2026. https://www.aafp.org/pubs/afp/issues/2024/0200/acute-uncomplicated-utis-adults.html#afp20240200p167-ta1
Summarized by Ashley Lyons OMS3 | Edited by Ashley Lyons & Jorge Chalit OMS4
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Contributor: Aaron Lessen, MD
Educational Pearls:
What is anaphylaxis and what are its treatments? 
Anaphylaxis is a broad term for potentially life threatening allergic reactions that can progress to cardiovascular collapse (anaphylactic shock). 
It is triggered by IgE and antigen cross-linking on mast cells to induce degranulation and the release of histamines, which can cause diffuse vasodilation and respiratory involvement with end-organ hypoperfusion.
First line treatment is the immediate administration of epinephrine at 0.01 mg/kg (max dose for pediatrics is 0.3 mg and for adults is 0.5 mg) as well as removal of the offending agent causing the reaction.
Additional pharmacologic treatments such as anti-histamines and steroids should be considered but not used instead of epinephrine when anaphylactic shock is evident as the sole therapy.
What is biphasic anaphylaxis and what is its occurrence?
Biphasic anaphylaxis is the return of anaphylactic symptoms after the initial anaphylactic event. Previous studies have reported an incidence ranging from 1-20% of patients having an initial anaphylactic reaction having biphasic anaphylaxis, at a range of time from 1-72 hours.
The mechanism of biphasic anaphylaxis is not completely known, but can be contributed to by initial interventions wearing off (and why patients will be monitored for 2-4 hours after initial symptoms and treatment), or delayed immune mediators beginning to take effect.
Recent studies show that the rate of biphasic anaphylaxis may be closer to 16% occurrence with a median time of occurrence being around 10 hours.
What is the key take away and patient education on biphasic anaphylaxis?
After patients have been observed for the initial 2-4 hours in the emergency room, they are generally safe to go home.
Patients should be informed of the need to carry an Epi-Pen for similar anaphylactic reactions, and informed that there is a chance within the next day (10-20 hours) that they may have the symptoms occur once again.
The biphasic reaction may be more mild, and patients should be educated on how to treat it and to seek immediate emergency care if the symptoms do not improve.
References
Golden DBK, Wang J, Waserman S, et al. Anaphylaxis: A 2023 practice parameter update. Annals of Allergy, Asthma & Immunology. 2024;132(2):124-176. doi:10.1016/j.anai.2023.09.015
Rubin S, Drowos J, Hennekens CH. Anaphylaxis: Guidelines From the Joint Task Force on Allergy-Immunology Practice Parameters. afp. 2024;110(5):544-546.
Weller KN, Hsieh FH. Anaphylaxis: Highlights from the practice parameter update. CCJM. 2022;89(2):106-111. doi:10.3949/ccjm.89a.21076
Gupta RS, Sehgal S, Brown DA, et al. Characterizing Biphasic Food-Related Allergic Reactions Through a US Food Allergy Patient Registry. The Journal of Allergy and Clinical Immunology: In Practice. 2021;9(10):3717-3727. doi:10.1016/j.jaip.2021.05.009
Summarized by Dan Orbidan OMS2 | Edited by Dan Orbidan & Jorge Chalit OMS4
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Contributor: Alec Coston, MD
Educational Pearls:
Disclaimer: this has nothing to do with the ER but is too cool to not talk about.
Condition: Carbamoyl phosphate synthetase 1 (CPS1) deficiency

Rare inborn error of metabolism

Inability to properly break down ammonia

Leads to severe hyperammonemia and hepatic encephalopathy

Natural history:

Without treatment, typically fatal within the first few weeks of life

Even with current standard treatments, life expectancy is often limited to ~5–6 years

Breakthrough treatment:

A team of researchers at the Children's Hospital of Philadelphia and the Perelman School of Medicine at the University of Pennsylvania developed the CRISPR-based targeted gene therapy for this patient.

First-of-its-kind precision approach tailored to the patient's specific mutation

Key components of the therapy:

Whole-genome sequencing to identify the exact CPS1 mutation

Creation of a custom base-editing enzyme designed to correct that specific mutation

Design of a guide RNA to direct the base editor to the precise genomic location

Delivery method:

Lipid nanoparticles used to deliver the gene-editing machinery

Nanoparticles can be targeted to specific tissues

Why the liver works well:

CPS1 is primarily expressed in hepatocytes

The liver is relatively easy to target with lipid nanoparticles

Hepatocytes divide frequently, allowing edited genes to be passed on as cells replicate

Long-term impact:

Once edited, cells continue producing functional CPS1 enzyme

Potential for durable, possibly lifelong correction from a single treatment

References
https://www.nih.gov/news-events/news-releases/infant-rare-incurable-disease-first-successfully-receive-personalized-gene-therapy-treatment

Choi Y, Oh A, Lee Y, Kim GH, Choi JH, Yoo HW, Lee BH. Unfavorable clinical outcomes in patients with carbamoyl phosphate synthetase 1 deficiency. Clin Chim Acta. 2022 Feb 1;526:55-61. doi: 10.1016/j.cca.2021.11.029. Epub 2021 Dec 29. PMID: 34973183.

Bharti N, Modi U, Bhatia D, Solanki R. Engineering delivery platforms for CRISPR-Cas and their applications in healthcare, agriculture and beyond. Nanoscale Adv. 2026 Jan 5. doi: 10.1039/d5na00535c. Epub ahead of print. PMID: 41640466; PMCID: PMC12865601.

Summarized and edited by Jeffrey Olson MS4
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