Pre-Arrest Acidemia and the Effect of Sodium Bicarbonate on ROSC


Sodium bicarbonate during a cardiac arrest is widely debated and used in many cases. In a 2018 PULMCrit post, Dr. Josh Farkas reviews much of the data and concludes that use of sodium bicarbonate is a “source of eternal disagreement.” A 2013 EMCrit article and podcast by Dr. Scott Weingart also details some of the controversy. The 2020 ACLS Guidelines state that routine use of sodium bicarbonate is not recommended in cardiac arrest [1]. Despite this recommendation, sodium bicarbonate is still often administered during resuscitations if a metabolic (or respiratory) acidosis is suspected or after a prolonged downtime. A recent study evaluated the effect of pre-arrest acid-base status on response to sodium bicarbonate and achievement of return of spontaneous circulation (ROSC) [2].


This was a retrospective review of in-hospital cardiac arrests (IHCA) in patients with pre-arrest serum bicarbonate levels ≤21 mmol/L compared to >21 mmol/L. Pre-arrest bicarbonate levels were obtained <24 hours prior to the arrest. Similarly, post-arrest bicarb levels were obtained <24 hours following the arrest. Bicarbonate levels were recorded from basic chemistry panels rather than blood gases. All patients received a median sodium bicarbonate dose of 100 mEq. The groups were relatively well-matched, with the only major difference being the time to first bicarb administration was faster in the ‘acidotic’ group (6.9 vs. 9.2 minutes). Initial ECG rhythms were similar between the groups.

  • 102 patients in ‘acidotic’ group with a median pre-arrest bicarb level of 17 mmol/L
  • 123 patients in ‘non-acidotic’ group with a median pre-arrest bicarb level of 27 mmol/L
  • There was no difference in ROSC (53.9% vs 48.8%, p=0.44) or survival to discharge (8.8% vs 5.7%, p=0.36) between the acidotic group versus the nonacidotic group

Thoughts and Limitations

  • A meta-analysis found no difference in sustained ROSC or survival to discharge with sodium bicarbonate (Alshahrani 2021).
  • In the current study, prearrest bicarb levels could have resulted up to 24 hours prior to the arrest and the authors don’t comment on when exactly they were drawn. The timing limits the ability to know true acid-base status just prior to the arrest. And, that really limits applying this to out-of-hospital cardiac arrest where patients may have more significant acidemia if resuscitation is delayed.
  • A median bicarbonate concentration of 17 mmol/L isn’t really that low, relatively speaking, to indicate a potential impact from administering sodium bicarbonate.
  • Retrospective cardiac arrest studies are challenging. Many interventions happen around the same, making it impossible to connect any one of them with a specific outcome.
  • The study that would be more helpful is taking patients with metabolic/respiratory acidosis and giving have bicarb and the other placebo.

Bottom Line

  • In this cohort of IHCA patients, sodium bicarbonate administration did not improve the chances of ROSC or survival to hospital discharge, irrespective of pre-arrest acid-base status. In other words, attempting to correct ‘acidosis’ does not seem to change rate of ROSC.
  • Sodium bicarbonate use in cardiac arrest should be targeted (e.g., hyperkalemia with metabolic acidosis, sodium channel blockade secondary to an overdose).

Want to learn more about EM Pharmacology?

Read other articles in the EM Pharm Pearls Series and find previous pearls on the PharmERToxguy site.


  1. Panchal AR, Bartos JA, Cabañas JG, et al. Part 3: adult basic and advanced life support: 2020 american heart association guidelines for cardiopulmonary resuscitation and emergency cardiovascular care. Circulation. 2020;142(16_suppl_2):S366-S468. doi: 10.1161/CIR.0000000000000916. PMID: 33081529.
  2. Mclean H, Wells L, Marler J. The effect of prearrest acid-base status on response to sodium bicarbonate and achievement of return of spontaneous circulation. Ann Pharmacother. Published online August 5, 2021:10600280211038392. doi: 10.1177/10600280211038393. PMID: 34353142.

SmilER 101: Oral Exam and Regional Anesthesia in Dental Care

The purpose of the SmilER series on dental trauma and infection management is to teach fundamental principles, pearls, and pitfalls in the care for dental patients in the emergency department. As many as 1.5% of ED visits are dental-related¹ and many emergency physicians have expressed the need for more comprehensive training in the oral cavity. This series was created as an introductory guide on the management of patients who report to the ED with dental-related conditions. The first module teaches the oral examination and demonstrates how to provide anesthesia in the oral cavity.

Author: Richard Ngo, DMD
Editors: Cameron Lee, DMD, MD; Andrew Eyre, MD, MS-HPEd
Series Editor: Chris Nash, MD

Learning Objectives

  1. Review basic anatomy of the oral cavity.
  2. Understand how to perform a basic oral examination.
  3. Learn to perform basic regional anesthesia to each region of the oral cavity.

How well did you learn the material? Go to ALiEMU to take the multiple-choice quizzes to receive your badges and certificates.


The typical adult oral cavity contains 32 teeth split into 4 sections, with each quadrant containing 2 incisors, 1 canine, 1 premolars, and 3 molars. The universal numbering system labels dentition with numbers from 1 through 32 starting with the right maxillary third molar. When assessing the oral cavity for avulsed or damaged dentition, it is essential to note some individuals may have congenitally missing teeth or may have had dentition extracted in the past due to various reasons. Premolars can be found anterior to the molars, and they are smaller in width.

Adult Dental Anatomy Chart

Permanent dentition named and numbered (modified from Shutterstock)


Whereas adults have 32 teeth, pediatric patients have 20 primary teeth, labeled A through T. Pre-adolescents have mixed dentition, consisting of both deciduous (“baby” or “primary”) dentition and succedaneous (“permanent”) dentition. Most pediatric patients will have lost all of their primary teeth by 12 years of age.

Tooth Anatomy

Each tooth follows the same overall anatomical structure, as seen in the diagram below. However, the shape, number of roots, function, and other attributes vary from tooth to tooth. When referencing dentition, coronal is the portion of the tooth towards the crown. On the other hand, apical (as in apex) is the portion of the tooth towards the root.

A thorough oral examination is essential in the ED assessment of patients with dental complaints. When assessing the oral cavity for avulsed or damaged dentition, it is essential to note that some individuals may have congenitally missing teeth or may have had dentition extracted in the past. Obtaining a thorough dental history and oral examination may help to alleviate any potential confusion regarding special anatomical considerations. Note findings such as absence of teeth, poor/damaged dentition, supernumerary teeth, extracted teeth, and tori.

This diagram reveals the eight regions of the oral cavity that the provider should examine carefully. Manual manipulation of the tongue is easier when gauze is used to obtain a steadier grip. A tongue depressor is recommended for examination of the posterior oropharynx.

Oral Tori

Oral tori are uncommon but normal variants of bone found along the palate or lingual aspect of the mandible. They are bony structures in the hard palate or the mandible, as shown below. It is important to know that these structures exist so as to avoid being unnecessarily alarmed.

Photo and CT Scan of a Torus Palatinus

Torus seen on the hard palate [exam, CT image]

Maxillary Tori photo and a CT scan demonstrating the same

Maxillary tori [exam, CT image]

Notably, tori differentiate themselves from cancers and abscesses in a few ways.

  1. Tori are typically bony to the touch as they arise from bone. In contrast, abscesses and soft tissue cancers are more fluctuant and/or softer than bone.
  2. Tori are typically symmetrical from side to side.
  3. Tori are typically asymptomatic.

Local anesthesia is necessary before splint placement, incision and drainage, or any other procedure which involves significant and painful dental manipulation. It may also be used for temporary relief of substantial pain. Note that this is not a long-term solution but simply a temporary measure to bridge a patient to an outpatient dental appointment. In these cases, bupivacaine is recommended due to its longer half-life. The maximum dosage of local anesthetics should be calculated prior to administration (MDcalc).

With appropriate dosing and administration, you shouldn’t have to worry about toxicity, but you can read more about local anesthetic systemic toxicity (LAST) to be extra prepared.

Supraperiosteal Block

Anesthesia of the maxillary dentition is achieved through supraperiosteal (“local”) infiltration of lidocaine. tThe maxilla is more porous than the mandible, allowing easier penetration of the bone and anesthesia of the dentition.

1. Anterior Maxilla

Administration of local anesthesia to the anterior maxillary dentition can be particularly painful for patients given the extensive neural anatomy of the nose. Thus, it is essential to begin laterally and work in a stepwise fashion medially. Additionally, one can consider topical anesthesia with viscous lidocaine or benzocaine before using the needle.

2. Posterior Maxilla

For posterior maxillary teeth, use a short needle to minimize the risk for developing a hematoma. Taut retraction of the lip and the attached mucosa provides tension which makes needle penetration easier. Additionally, retraction activates proprioceptive fibers, which helps distract the patient from the pain of needle insertion.

Supraperiosteal Block: Site of local anesthetic deposition for infiltration technique to anesthetize regions of the maxilla. Source: NYSORA.COM


  1. Aim for the tooth apex and advance the needle while maintaining a needle position parallel to the long axis of the tooth.
  2. Penetrate the mucogingival junction with the bevel pointing towards the bone.
  3. Make contact with bone.
  4. Aspirate.
  5. Inject 1-2 cc of anesthetic.

Inferior Alveolar Nerve Block

The inferior alveolar nerve (IAN) is a branch of the mandibular nerve (V3 of the trigeminal nerve). Anesthesia of this nerve will result in anesthesia of the ipsilateral mandibular teeth to the midline, as well as the skin and mucous membranes of the lower lip, skin of the chin, and the labial gingiva of the anterior teeth. The goal is to inject local anesthetic in the region of the IAN before it enters the mandibular foramen at the medial aspect of the mandible.

Landmark Anatomy

The following figures help to clarify major anatomical landmarks for the IAN block:

IAN Landmarks

Inferior Alveolar Nerve Block: Pay attention to the site of entrance of the alveolar nerve into the mandible, and note the coronoid notch as an important landmark.

Inferior Alveolar Nerve Block Landmarks

Inferior Alveolar Nerve Block: The pterygomandibular raphe is a useful landmark to guide the intraoral injection point. When the patient’s mouth is held as wide as possible, the raphe tenses and becomes a visible reference line. The injection point (labeled with an X above) should be just lateral to the line so that the needle does not penetrate the raphe itself. An optional pre-step is to apply topical anesthesia with viscous lidocaine or benzocaine at the planned injection site prior injection.


  1. Place the thumb in the ipsilateral coronoid notch and visualize a line extending from the thumb back to the pterygomandibular raphe (roughly two-thirds up the finger nail).
  2. Keep the needle parallel to the occlusal plane with the bevel positioned away from the bone.
  3. Enter with the syringe oriented on the contralateral mandibular premolars.
  4. Insert the needle 1 cm above the occlusal plane and 3-5 mm lateral of the pterygomandibular raphe.
  5. Advance the needle 20-25 mm to sound bone.
  6. Retract 1-2 mm.
  7. Aspirate.
  8. Inject 75% of the total dose in this region.
  9. While removing the needle, inject the remaining 25% dose to anesthetize the lingual nerve. The total amount injected will be approximately 1-2 cc of anesthetic.
  10. Ensure adequate anesthesia by testing the patient for any acute pain upon manipulation. Keep in mind that it may take up to 5 minutes for the block to take effect following administration.

Of note, given its proximity to the IAN, the lingual nerve is also sometimes anesthetized during this block. This leads to anesthesia of the anterior two thirds of the tongue, the lingual gingiva, and the mucosa of the floor of the mouth.

Adjunctive Blocks

  1. Mandibular Incisors: The IAN block is typically sufficient to anesthetize the ipsilateral mandibular dentition and soft tissues. However it can somestimes under-anesthetize the mandibular incisors, If this occurs, we recommend adjunctive supraperiosteal blocks, as noted in the previous section. Note that supraperiosteal blocks, while useful in the maxilla, will not reliably attain complete anesthesia of the mandibular dentition as the mandible is less porous.
  2. Lips: The mental block is useful for the soft tissues of the lip anteriorly

Peer Reviewed

All information has been expert peer-reviewed by an oral and maxillofacial surgeon. 


  1. Hupp J, Ellis E, Tucker M. Contemporary Oral and Maxillofacial Surgery. Elsevier; 2019.
  2. Kademani D, Tiwana P. Atlas of Oral and Maxillofacial Surgery. Saunders; 2015.
By |2021-09-15T06:17:56-07:00Sep 15, 2021|ALiEMU, Dental, SmilER|

SAEM Clinical Image Series: Pediatric Penis Swelling

A 3-year-old healthy uncircumcised male presents to the Emergency Department with five days of penis swelling and pain. Five days prior, his father noted that the patient’s foreskin appeared stuck behind the head of the penis. The patient was seen at an urgent care facility four days prior and was given an antifungal cream for presumed balanitis, however, this did not resolve the patient’s symptoms. Since that time, the penis has been getting progressively more swollen and painful. The patient has not experienced the inability to urinate, decreased urine output, penile discharge, other penile lesions, fever, chills, abdominal pain, nausea, vomiting, testicular pain, or testicular swelling.

Vitals: Within normal limits

General: Alert, anxious

Genitourinary: Penile swelling, erythema, and tenderness to palpation


Paraphimosis is a medical emergency due to the risk of tissue necrosis. A preputial or phimotic ring – a circumferential band of tissue – caught behind the glans causes swelling of penile tissue.

In the evaluation of painful penile swelling, the first step is to determine whether the patient is circumcised or not through a review of the medical record or discussion with the patient’s family. In an uncircumcised male, the critical next step is to assess for an entrapped and retracted foreskin (paraphimosis). Visualization of the glans penis and the urethral meatus as in this case demonstrates that the foreskin is retracted. Additionally, visualization of the glans penis and urethral meatus makes a scarred and unretractable foreskin (pathologic paraphimosis) unlikely to be the primary diagnosis. The differential diagnosis also includes hair tourniquet syndrome, chigger bites, and inflammation of the glans and foreskin (balanitis and balanoposthitis).

Take-Home Points

  • In any male presenting with penile pain, it is critical to first ascertain his circumcision status. In an uncircumcised male, visualizing the glans and urethral meatus demonstrates that the foreskin is retracted.
  • Paraphimosis is a medical emergency caused by an entrapped, retracted foreskin.
  1. Bragg BN, Kong EL, Leslie SW. Paraphimosis. 2021 May 4. In: StatPearls [Internet]. Treasure Island (FL): StatPearls Publishing; 2021 Jan–. PMID: 29083645.
  2. 2. Simonis K, Rink M. Paraphimosis. In: Urology at a Glance. Springer Berlin Heidelberg; 2014:361-364. doi:10.1007/978-3-642-54859-8_65




By |2021-09-13T10:34:13-07:00Sep 13, 2021|Genitourinary, Pediatrics, SAEM Clinical Images|

EMRad: Can’t Miss Adult Traumatic Hip and Pelvis Injuries


Have you ever been working a shift at 3 AM and wondered, “Am I missing something? I’ll just splint and instruct the patient to follow up with their PCP in 1 week.” This is a reasonable approach, especially if you’re concerned there could be a fracture. But we can do better. Enter the “Can’t Miss” series: a series organized by body part that will help identify injuries that ideally should not be missed. This list is not meant to be a comprehensive review of each body part, but rather to highlight and improve your sensitivity for these potentially catastrophic injuries. We’ve already covered the adult elbow, wrist, shoulder, ankle/foot, and knee. Now: the hip.



By |2021-09-01T17:23:13-07:00Sep 3, 2021|Orthopedic, Radiology, SplintER, Trauma|

SAEM Clinical Image Series: Pulseless and Painful Blue Leg

painful blue leg

A 57-year-old male who works as a truck driver with a history of hypertension, type 2 diabetes, and recent COVID-19 infection presents with right lower extremity pain for two hours. He reports experiencing one day of dull aching of the right leg, then being suddenly awakened with the abrupt onset of severe right leg pain and shortness of breath. He denies chest pain. EMS reports a pulseless and painful blue leg en route. The patient denies any history of trauma, irregular heartbeat, or anticoagulation.

Vitals: T 97.5°F; BP 120/78; HR 102; RR 20; oxygen saturation 100%

General: Writhing and moaning in pain

Cardiovascular: Tachycardic; 2+ pulses in all extremities except for the right lower extremity

Pulmonary: No respiratory distress

Hemoglobin: 12.9 g/dL

INR: 1.02

Phlegmasia cerulea dolens

When a patient presents with a painful, pulseless extremity, acute limb ischemia, with etiologies including aortic dissection, arterial thromboembolism, and phlegmasia dolens, is of the highest concern. Unlike a typical deep venous thrombosis (DVT), phlegmasia dolens is a DVT that causes complete occlusion, resulting in venous congestion and hypoperfusion. Risk factors for phlegmasia dolens and DVT are the same; this patient had both a sedentary occupation and recent COVID-19 as risk factors.

Phlegmasia is usually characterized early on with pale discoloration (alba) due to patency of collaterals and later with blue/cyanotic discoloration (cerulea) after complete occlusion of the venous system. It is important to remember this exam finding might be limited in pigmented skin. Venous gangrene and compartment syndrome can be delayed exam findings. The exam should include immediate evaluation of pulses with doppler and compartment checks. Imaging modalities are controversial and should not delay vascular surgery consultation. Bedside ultrasound can be rapidly performed for clot evaluation, but CT venogram would be the preferred method for surgical planning. A common femoral vein DVT can be seen on the accompanied ultrasound and CT images. The limb should be elevated, and heparin infusion should be initiated. Surgical consultation should include a discussion of thrombectomy or catheter-directed thrombolysis.

Take-Home Points

  • Phlegmasia cerulea dolens is an uncommon complication of DVT that presents with a discolored, painful, pulseless extremity, and is associated with high morbidity and mortality.
  • Initial management includes vascular surgery consultation, elevation of the extremity, and heparinization.
  1. Baker, William, and Samuel Kim. “Risking Life And Limb: Management Of Phlegmasia AlbaAnd Cerulea Dolens”. Emra.Org, 2020,–alba-and-cerulea-dolens/.
  2. Gardella L, Faulk J. Phlegmasia Alba And Cerulea Dolens. 2020 Oct 12. In: StatPearls [Internet]. Treasure Island (FL): StatPearls Publishing; 2021 Jan–. PMID: 33085284.



Diagnosis on Sight: “I have a rapid heart rate”

A 31-year-old male presented to the emergency department with palpitations. The patient stated that he thinks his symptoms began “last night” and felt like he had “a rapid heart rate.” He said that prior to last night he felt fine. He did admit to drinking alcohol with his friends 2 nights prior. The patient estimated that he “must have drunk about 30 beers.” On review of systems, he reported feeling anxious. He denied illicit drug use, headache, chest pain, cough, shortness of breath, fevers, nausea, vomiting, abdominal pain, dysuria, or increased urinary frequency. He reported that he was unaware of any family history of early heart disease or sudden death. His initial EKG is shown below.

After consultation with cardiology, the decision was made to cardiovert the patient given the wide complex tachycardia.  After cardioversion, the resulting EKG is shown below:

On review of previous records, the patient had a recent ED visit 2 months ago with the EKG shown below:

What is the diagnosis?

Preexcited atrial fibrillation with underlying Wolf-Parkinson-White syndrome


Wolf-Parkinson-White (WPW) syndrome and the WPW pattern on EKG are rare disorders. Only 0.13 – 0.25% of the population have a WPW pattern on EKG [1,2]. However, only a small fraction of these people will develop WPW syndrome. WPW syndrome is defined as a symptomatic arrhythmia with a WPW pattern on EKG.

The patient’s initial EKG showed a wide complex tachycardia that was ultimately determined to be preexcited rapid atrial fibrillation. After cardioversion, the patient’s underlying baseline EKG tracing showed findings of Wolf-Parkinson-White with:

  • A shortened PR interval
  • Widened QRS complex
  • Delta wave: Slurred upstroke of the QRS complex

The most common arrhythmias associated with WPW syndrome are:

  • AV Reentrant Tachycardia (AVRT): Seen in over 90% of patients with WPW syndrome [3,4]
  • Atrial Fibrillation: 10-30% [5,6]
  • Atrial Flutter: Less than 5%

As in this case, AVRT (i.e. SVT) is often followed by atrial fibrillation in patients with WPW. Although the pathophysiology is unclear, up to 35% of instances of atrial fibrillation were preceded by AVRT [5,7,8].

Fortunately, fatal dysrhythmias such as ventricular fibrillation and ventricular tachycardia are very rare with WPW.

Case Conclusion:

Following cardioversion, the patient remained stable in sinus rhythm. After consultation with cardiology, the patient was discharged on Flecainide and Metoprolol and a referral for outpatient cardiology was placed for follow-up care. Soon after, the patient had an electrophysiology study that showed a left posterolateral accessory conduction pathway. He then underwent successful ablation of his orthodromic AVRT.

Want more visual stimulation? Check out the Diagnose on Sight archives!



  1. Krahn AD, Manfreda J, Tate RB, et al. The natural history of electrocardiographic preexcitation in men. The Manitoba Follow-up Study. Ann Intern Med 1992; 116:456. PMID: 1739235
  2. Kobza R, Toggweiler S, Dillier R, et al. Prevalence of preexcitation in a young population of male Swiss conscripts. Pacing Clin Electrophysiol 2011; 34:949. PMID: 21453334
  3. Josephson ME. Preexcitation syndromes. In: Clinical Cardiac Electrophysiology, 4th, Lippincot Williams & Wilkins, Philadelphia 2008. p.339.
  4. Chugh A, Morady F. Atrioventricular reentry and variants. In: Cardiac electrophysiology from cell to bedside, 5th edition, Zipes DP, Jalife J (Eds), Saunders/Elsevier, Philadelphia 2009. p.605-614.
  5. Campbell RW, Smith RA, Gallagher JJ, et al. Atrial fibrillation in the preexcitation syndrome. Am J Cardiol 1977; 40:514. PMID: 910715
  6. Sharma AD, Klein GJ, Guiraudon GM, Milstein S. Atrial fibrillation in patients with Wolff-Parkinson-White syndrome: incidence after surgical ablation of the accessory pathway. Circulation 1985; 72:161. PMID: 4006127
  7. Sung RJ, Castellanos A, Mallon SM, et al. Mechanisms of spontaneous alternation between reciprocating tachycardia and atrial flutter-fibrillation in the Wolff-Parkinson-White syndrome. Circulation 1977; 56:409. PMID: 884796
  8. Fujimura O, Klein GJ, Yee R, Sharma AD. Mode of onset of atrial fibrillation in the Wolff-Parkinson-White syndrome: how important is the accessory pathway? J Am Coll Cardiol 1990; 15:1082. PMID: 2312962
By |2021-08-27T09:10:41-07:00Aug 25, 2021|Cardiovascular, Diagnose on Sight, ECG|
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