The Waiting Game: Biphasic Anaphylaxis

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Written by: Kumar Gandhi, MD, MPH (NUEM PGY-2) Edited by: Andrew Moore, MD, MS (NUEM PGY-4) Expert Commentary by: Aaron Kraut, MD

Case Scenario

18 y.o. female with history of asthma and multiple food allergies presents with rash and
shortness of breath following ingestion of assortment of cookies at a Halloween party. A diffuse erythematous pruritic rash started fifteen minutes following the ingestion of cookies. Associated symptoms include tingling in the back of the throat and wheezing. The patient reports one prior episode requiring use of an EpiPen, but she never refilled her prescription.

Vitals: HR: 90, RR: 25, BP: 105/70, Temp: 98.6, SpO2: 97% on room air

Pertinent findings on physical exam include:

  • Mild pharyngeal edema with no uvular deviation.
  • Moderatewheezing in bilateral lung fields
  • Diffuse abdominal tenderness
  • Blanching (urticarial) rash on the back,nabdomen, axilla, femoral creases, and posterior legs.

An Epi-Pen injection in the right thigh, coupled with concomitant 125mg of methylprednisolone IV Push, 25mg of Benadryl IV push [1] results in decreased wheezing and resolution of the urticarial rash.

Now that the patient is stable we need to ask ourselves a few important questions:

  1. Was this an allergic reaction or anaphylaxis?
  2. When can we discharge the patient?

Anaphylaxis: Overview

Anaphylaxis is a life-threating systemic hypersensitivity reaction. Pathophysiology includes [1]:

  • IgE-mediated Type 1 hypersensitivity reaction
  • Degranulation of mast cells releases vasoactive mediators including histamine, prostaglandins, and leukotrienes
  • Histamine mediates systemic vasodilation, cardiac contractility, and vascular permeability
  • Leukotrienes mediate vascular permeability and in combination with prostaglandins cause bronchoconstriction


Common Triggers:

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  • Foods: Peanut, tree nut, shellfish, finned fish, milk, egg
  • Insects: Insect stings and Insect bites
  • Medications: Antibiotics, Aspirin, and NSAID’s
  • Biologic materials: Monoclonal antibodies, chemotherapy, vaccines
  • Physical Factors: Exercise, cold, heat
  • Iatrogenic: Latex and radiocontrast agents


Signs and Symptoms of Anaphylaxis [2]:

  • Skin and mucosal symptoms occur in 90% of episodes
  • Respiratory symptoms and signs occur in up to 70% of episodes
  • GI symptoms such as nausea, vomiting, and diarrhea occur in 45% of episodes
  • Cardiovascular symptoms such syncope, dizziness, and tachycardia can occur in 45% of episodes


NIAID/FAAN Criteria for the Diagnosis of Anaphylaxis [3]

Diagnosis of Anaphylaxis:

  • Anaphylaxis is primarily a clinical diagnosis.
  • Diagnosis of anaphylaxis is made when any one of three NIAID/FAAN diagnostic criteria are fulfilled.

A 2012 retrospective cohort study of the NIAID/FAAN criteria demonstrated 97% sensitivity and 82% specificity for the diagnosis of anaphylaxis in 214 ED patients [3].



What is Biphasic Anaphylaxis?

Biphasic anaphylaxis is an anaphylactic episode followed by an asymptomatic period with return of anaphylactic symptoms in the absence of further exposure to the triggering antigen [4]. Incidence of secondary reaction following primary anaphylactic reaction can range from 1% to 23%, and
occurs in up to 23% of adults and up to 11% of children. [4] [5] [6]. The time interval from primary to secondary reaction ranges from 1 to 72 hours, though predominantly occurs within 8 hours of primary event [6].

Risk Factors for Biphasic Anaphylaxis

Predicting the occurrence of a biphasic reaction poses a diagnostic challenge. Previously studied risk factors for the development of biphasic anaphylaxis include [4]:

  • Severity of the primary anaphylactic reaction
  • Time from exposure of antigen to development of the primary response
  • Presence of hypotension or laryngeal edema
  • History of a previous biphasic reaction or asthma
  • Time to delivery of epinephrine for primary anaphylaxis [7]
  • Initial dosing of epinephrine in treatment of primary anaphylaxis [8]


How long should we watch patients?

Previous Practice
World Allergy Organization 2011 guidelines recommend an individualized approach, ranging from at
least 4 hours for patients with moderate respiratory or cardiovascular compromise to up to 8-10 hours or
longer if indicated for a protracted anaphylactic response. [9]

Often referenced in the anaphylactic observation time conundrum, Ellis et al. performed a 3-year
prospective study in a Canadian tertiary hospital, which found 103 cases of true anaphylaxis with a
19.4% occurrence of biphasic reactivity and an average time of secondary reaction onset of 10 hours.
Biphasic reactivity occurred in 60% cases before 10 hours [8]. The increased prevalence of biphasic reactions in this study is likely secondary to inclusion of all biphasic reactivity, including recurrent minor reactions and reactions that were not truly biphasic requiring epinephrine. [8] [10].

Current Literature
New literature indicates a much lower prevalence of clinically significant biphasic anaphylaxis. Gruanau et al. performed a retrospective chart review of 2,819 adult ED patients at two large urban ED’s
over a five-year span. 496 patients were classified as anaphylactic, of the total number of anaphylactic
patients evaluated only 5 (0.18%) had clinically significant biphasic reactions and zero mortality. Of the 3
patients that actually left the ED, the biphasic reaction occurred up to 6-days post-discharge, indicating
these reactions could occur at any time after discharge. This study concluded given such a low prevalence
of biphasic anaphylaxis, zero mortality, and variability in time to the secondary reaction it is unnecessary
to observe patients following resolution of symptoms [10] [11] [12].

Rohacek M et al. also performed a retrospective chart review 1,334 adult ED patients in a Swiss tertiary
care hospital over a 12-year span. 495 patients met the diagnosis of anaphylaxis, of which only 12 (2.3%)
were clinically significant anaphylactic reactions, with only 2 (0.36%) occurring in the hospital. Similar to
the Gruanau et al. study there were no deaths during the 10-day follow-up period. The study also
demonstrated no difference in the biphasic response rate for those patients watched for less than 8-
hours vs greater than 8 hours. [10] [13].

The new literature indicates a prevalence of 0.18%-2.3% clinically significant biphasic anaphylactic
reactions and zero mortality over the 4100 patients who were included in both studies. This indicates it is
likely safe to discharge patients home following resolution of their anaphylactic episode.

Recommendations/Take Home Points

Consider 1-hour observation period following resolution of symptoms for those patients [10]:

  • Promptly and adequately treated with Epi-Pen and demonstrate early resolution of symptoms
  • Patients who can be trusted with strong return precautions and with ability to access medical interventions should a biphasic response occur and demonstrate competence with utilizing an Epi-Pen at home [9]
  • 1-hour observation period is to ensure no recurrence of anaphylaxis following complete metabolism of epinephrine [10]

Consider observation time of 4-8 hours for those patients with:

  • Previous episodes of biphasic anaphylaxis or history of asthma [4]
  • Anaphylaxis with severe features including refractory hypotension, laryngeal edema, and respiratory compromise [4]
  • Patients who may have experienced significant delays in treatment with epinephrine or received a subtheraputic initial dose of epinephrine [7] [8]

Anaphylaxis Discharge Instructions
The discharge process presents a critical opportunity to educate patients about the signs and symptoms of a potential biphasic episode of anaphylaxis as well as provide the necessary education and tools for a patient to quickly intervene should a future episode of anaphylaxis occur. Per World Allergy Organization guidelines for the assessment and management of anaphylaxis, discharge management should include [9]:

World Allergy Organization Discharge Management Guidelines [9]

Expert Commentary

This is a great summary of an important and controversial topic. In my relatively short career as an emergency physician, I’ve probably heard 17 different answers to the seemingly simple question of how long to observe someone with anaphylaxis in the ED.  

You did a very nice job of summarizing the best available evidence to guide our practice as emergency physicians. A few key points I’ll highlight again for emphasis:

  1.  Not all allergic reactions are anaphylaxis- in a nutshell, you need multisystem organ involvement (usually skin/mucosa +respiratory or GI) or skin/mucosal involvement and hypotension to have anaphylaxis.

  2.  Severe biphasic responses are RARE and vary greatly in their time to onset

One of my biggest take homes on this topic comes from the Grunau 2014 Annals of EM article.  In that study, all of the severe/clinically significant biphasic anaphylactic reactions occurred in patients who did not meet the diagnostic criteria for anaphylaxis on their initial ED visit.   In my mind, this represents a huge opportunity for education and preemptive intervention in our emergency department patients who present with moderate/severe allergic reactions in general.

If I treat a patient for a moderate/severe allergic reaction with diphenhydramine and steroids, I universally discharge that patient with a prescription for an EpiPen and an explicit warning about the rare event of a biphasic reaction. Ideally, if they are one of those rare few who has a biphasic reaction because of an ‘inadequately treated’ initial reaction (one of the risk factors for a biphasic reaction), I’d like them to be able to administer life-saving epinephrine before they arrive back to the ED.

As far as the question of how long to observe once we’ve pulled the trigger on IM epinephrine in the ED, there is still no magic formula despite the several well-conducted studies you’ve reviewed here.

For me, it comes back to patient education. Since we know we cannot reliably predict the time to onset of biphasic symptoms, I do not put a strict time limit on patient observation after Epi administration. However, I will offer several criteria that a patient must meet before I’m comfortable with discharge.

  1. Objective airway findings must be resolved (uvular, lip/tongue edema, change in voice)
  2. Skin findings must be stable or improving
  3. Hemodynamics must be normal

Some patients may satisfy those criteria 45 minutes after Epi administration, while others may take 120 minutes or longer.  If my patient has worsening skin findings or continued objective airway findings at >120minutes, I will usually admit them for close monitoring and consideration of repeat epi dosing. 

If a patient meets the aforementioned discharge criteria, then it’s time for the education piece. If I know that the patient understands the signs and symptoms of a recurrent or biphasic anaphylactic reaction, has an Epi-Pen and knows how to use it, and understands that he/she must return to the ED immediately if he/she uses the Epi-Pen, I will discharge the patient as early as 40min-1hr after ED arrival. My thought is that there isn’t much to be gained from observation, where any worsening of symptoms would prompt re-administration of epinephrine (which the patient can accomplish themselves). The key, however, is that the patient understands the necessity of immediately returning to the ED upon re-dosing of epinephrine.

Finally, I am not personally a fan of the 4-8 hour observation, as I don’t believe there is much to be gained by keeping a patient in the ED for that amount of time. Either they respond to epinephrine and rapidly improve, or they do not respond and require repeated dosing or close airway monitoring/intervention for continued objective airway involvement. I’ll decide to admit many of these patients within the first 15 minutes of their ED stay. These rapid “decision to admit” patients also include those with anaphylactic shock (persistent hypotension or altered mental status/end-organ dysfunction), or severe objective airway findings (e.g. stridor, hypoxemia) on ED arrival.

And with that, you have an 18th different answer to the question of how long to observe someone with anaphylaxis in the ED. But do remember that biphasic anaphylaxis can also occur in patients who did not present with frank anaphylaxis on their initial ED visit. Be mindful of your discharge instructions for all allergic reactions and consider prescribing Epi-Pens to those whom you treat with diphenhydramine and steroids.

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Aaron Kraut, MD

Assistant Professor, Assistant Program Director, University of Wisconsin Emergency Medicine

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How to cite this post

[Peer-Reviewed, Web Publication] Gandhi K,  Moore A (2017, Sep 12). The Waiting Game: Biphasic Anaphylaxis.  [NUEM Blog. Expert Commentary By Kraut A]. Retrieved from


  1. Adams, James “immune System Disorders. “Emergency Medicine: Clinical Essentials. Philadelphia, PA: Elsevier/Saunders, 2013 924-28. Print.
  2. Lieberman P, Nicklas RA, Randolph C, et al. Anaphylaxis--a practice parameter update 2015. Ann Allergy Asthma Immunol 2015; 115:341.
  3. Campbell RL, Hagan JB, Manivannan V, et al. Evaluation of national institute of allergy and infectious diseases/food allergy and anaphylaxis network criteria for the diagnosis of anaphylaxis in emergency department patients. J Allergy Clin Immunol 2012; 129:748
  4. Lieberman P. Biphasic anaphylactic reactions. Ann Allergy Asthma Immunol. 2005;95:217e226. III
  5.  Rohacek, M, H Edenhofer, A Bircher, and R Bingisser. 2014. Biphasic anaphylactic reactions: occurrence and mortality. Allergy, no. 6 ( 12). doi:10.1111/all.12404. 
  6. Tole JW, Lieberman P. Biphasic anaphylaxis: review of incidence, clinical predictors, and observation recommendations. Immunol Allergy Clin North Am 2007;27:309–326.
  7.  Lee JM, Greenes DS. Biphasic anaphylactic reactions in pediatrics. Pediatrics 2000; 106:762.
  8. Ellis AK, Day JH. Incidence and characteristics of biphasic anaphylaxis: a prospective evaluation of 103 patients. Ann Allergy Asthma Immunol 2007; 98:64.
  9. Simons FE, Ardusso LR, Bilo MB, El-Gamal YM, Ledford DK, Ring J et al. World allergy organization guidelines for the assessment and management of anaphylaxis. World Allergy Organ J 2011;4:13–37.
  10. Swaminathan, Anand, and Salim Rezaie. "REBELcast Episode 1." Audio blog post. REBEL E.M. N.p., 1 July 2014. Web.
  11. Grunau BE et al. Incidence of Clinically Important Biphasic Reactions in Emergency Department Patients with Allergic Reactions or Anaphylaxis.
  12. Swaminathan, Anand. "SGEM#57: Should I Stay or Should I Go (Biphasic Anaphylactic Response)." Blog post. N.p., 13 Dec. 2013. Web.
  13. Rohacek, M, H Edenhofer, A Bircher, and R Bingisser. 2014. Biphasic anaphylactic reactions: occurrence and mortality. Allergy, no. 6 ( 12). doi:10.1111/all.12404. 

Posted on September 11, 2017 and filed under Pharmacology.

Inguinal Hernia Imaging and Reduction

Written by: Jesus Trevino MD, MBA (NUEM PGY-3) Edited by: Samia Farooqi, MD (NUEM 2016 Graduate) Expert Commentary by: Adriana Segura Olson, MD


Mr. FJ is a 84 year old male with history of bilateral inguinal hernias status post repair with mesh 26 years ago who presents with constipation.  Five days ago, he suffered from a profuse diarrheal illness that also affected his household members.  Two days ago, he developed constipation with gradually progressive abdominal bloating, belching, and today bilious emesis.  On exam, he is afebrile, hemodynamically stable with moderate abdominal distention and right inguinal swelling that is tender, non-mobile and without overlying skin changes.

A CT abdomen and pelvis revealed a small bowel obstruction secondary to a right-sided incarcerated inguinal hernia!

Types of abdominal hernias

Abdominal hernias can be classified based on etiology (i.e., congenital vs acquired) and location (Adams): 

A retrospective review of 2510 hernia repairs from a single institution in Scotland (1985-2008) found the following distribution of abdominal hernias by location (Dabbas):

  • Inguinal (70.7%)

  • Umbilical (13.9%)

  • Epigastric (6.6%)

  • Incisional (4.7%)

  • Femoral (3.7%)

  • Spigelian/other (0.4)

Of inguinal hernias, the indirect form account for 65% of cases (Adams).

Clinical presentation and physical exam findings

Patient characteristics associated with an increased risk of abdominal hernia include (Fitzgibbons):

  • Male sex

  • Lower BMI

  • Family history of abdominal hernia

  • COPD

  • Smoking

  • Collagen vascular disease

  • Thoracic or abdominal aortic aneurysm

  • Open abdominal surgery

  • Peritoneal dialysis

On presentation, patients typically complain of abdominal or scrotal pain with or without superficial abdominal wall swelling that may worsen with maneuvers that increase intra-abdominal pressures (Adams).  There may be a preceding event involving heavy lifting, coughing or other form of straining.  (Adams).  Symptoms such as nausea, emesis, constipation, and abdominal distention raise concern for small bowel obstruction.

On exam, inspection may reveal swelling in a ventral, umbilical, inguinal or femoral location.  Often, the swelling can be reduced with gentle pressure - a reducible hernia; those that cannot be reduced at bedside are classified as incarcerated hernias.  Tenderness to palpation and overlying skin changes, such as red, purple or blue coloration, increases suspicion for strangulated hernia.


CT abdomen and pelvis is a good imaging modality to assess for abdominal hernia, especially when there is concern for acute incarceration or strangulation.  CT findings include a “zone of transition” depicting a change in diameter of small bowel from dilated to a normal or decreased diameter such as the “pinch point” seen in the case image.  Signs concerning for strangulation include engorged vessels within incarcerated hernia, fat stranding and thickened bowel wall (Strange).

A prospective study in Australia of patients with abdominal pain presenting to an ambulatory practice showed CT without contrast was 90% sensitive and 97% specific for the diagnosis of abdominal hernia, yielding a LR+ 26 and LR- 0.10 (Garvey). Assuming greater acuity of symptoms in the Emergency Department is associated with greater anatomical abnormalities more easily detected on CT, these test statistics can be generalized to the emergency setting.


Bedside reduction is indicated when a hernia is incarcerated without evidence of strangulation.  Signs suggestive of necrosis of hernia contents include peritonitis and erythema or necrosis of the overlying skin (Adams).

To prepare for reduction, place the patient supine in Trendelenburg (-20 degrees) with an ice pack overlying the area of swelling (Roberts).  In addition to procedural sedation, immediate pain control soon after ED arrival facilitates abdominal wall muscle relaxation and increases likelihood of reduction success, sometimes even spontaneously when the patient is properly positioned.

Next, palpate the outline of the abdominal wall defect with the nondominant hand and place gentle inward pressure with the dominant hand at the base (i.e., the most proximal portion) of the hernia contents to slide the contents intra-abdominally.  As the hernia contents slide through the abdominal wall defect, take care to avoid completely collapsing the lumen of the trapped small bowel at the “pinch point” as this will lead the remaining trapped bowel to distend (i.e., the ballooning effect), exceed the dimension of the wall defect and reduce the chances of a successful reduction at the bedside.


Reducible abdominal wall hernias without signs of bowel ischemia can be discharged with appropriate outpatient general surgery follow-up for elective repair.

Hernias that remain incarcerated or have evidence of strangulation require general surgery consult for eventual OR reduction.  Factors associated with difficult bedside reduction include duration of incarceration and small abdominal wall defect.

Case resolution

Bedside reduction failed; in retrospect, there was a low likelihood success based on the small “pinch point” (1.3 cm) relative to the bulk of the hernia contents.  Mr. FJ was admitted and underwent open inguinal hernia repair with small bowel resection, primary anastomosis and discharged on post-operative day 14.

Expert Commentary

This is an excellent summary by Dr. Trevino of the Emergency Department management of hernias with respect to imaging and reduction.

As mentioned in this post, it is important to determine whether an incarcerated hernia is associated with strangulation, which indicates bowel necrosis. Hernias that are clearly strangulated should not be reduced at the bedside and surgical consultation is warranted; however, these are not always easily distinguishable on physical exam. While patients with incarcerated hernias without strangulation can present with systemic symptoms including nausea and vomiting, signs of strangulation include toxic appearance of the patient, significant systemic symptoms, or pain that persists after reduction of the hernia. A lactate is often sent in cases of an incarcerated hernia, but its sensitivity and specificity is limited and therefore, when there is a high index of suspicion, a normal lactate level should not be used to rule out strangulation (Derikx). 

We often feel reassured with a normal lactate, but be wary of relying on this test and don’t let your surgical consultants rely too heavily on the lactate either!

It’s worth mentioning cases of internal hernias, which involve bowel protrusion through the peritoneum or mesentery into another compartment in the abdominal cavity. While rare, they are important to keep on the differential of undifferentiated abdominal pain as they can lead to small bowel obstruction or bowel necrosis. Internal hernias can be difficult to diagnose clinically because their presentation is often vague and intermittent, and they are not palpable on physical exam. CT scan of the abdomen and pelvis is the diagnostic modality of choice and this imaging may be normal in cases of reducible internal hernias. When diagnosed, prompt surgical consultation is indicated.


Adriana Segura Olson, MD

Assistant Professor, UT San Antonio Department of Emergency Medicine

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How to cite this post

[Peer-Reviewed, Web Publication] Trevino J,  Farooqi S (2017, Aug 15). Inguinal Hernia Imaging and Reduction.  [NUEM Blog. Expert Commentary By Olson AS]. Retrieved from


Adams, James. Emergency Medicine: Clinical Essentials. Philadelphia, PA: Elsevier/Saunders, 2013. Print.

Dabbas, N., K. Adams, K. Pearson, and G. Royle. "Frequency of Abdominal Wall Hernias: Is Classical Teaching out of Date?" JRSM Short Reports 2.1 (2011): 5. Print.

Garvey, J. F. W. "Computed Tomography Scan Diagnosis of Occult Groin Hernia." Hernia 16.3 (2011): 307-14. Print.

Roberts, James R., Catherine B. Custalow, Todd W. Thomsen, and Jerris R. Hedges. Roberts and Hedges' Clinical Procedures in Emergency Medicine. Print.

Solomon, Caren G., Robert J. Fitzgibbons, and R. Armour Forse. "Groin Hernias in Adults." New England Journal of Medicine N Engl J Med 372.8 (2015): 756-63. Print.

Strange, Chad D., Krista L. Birkemeier, Spencer T. Sincleair, and J. Robert Shepherd. "Atypical Abdominal Hernias in the Emergency Department: Acute and Non-acute." Emerg Radiol Emergency Radiology 16.2 (2008): 121-28. Print.

Derikx, Joep P.m., Dirk H.s.m. Schellekens, and Stefan Acosta. "Serological markers for human intestinal ischemia: A systematic review." Best Practice & Research Clinical Gastroenterology 31, no. 1 (2017): 69-74.

Adriana Segura Olson, MD. Assistant Professor, Assistant Program Director, Department of Emergency Medicine, University of Texas Health San Antonio

AAA-OK: Approach to Imaging of Abdominal Aortic Aneurysm

Around 30% of symptomatic abdominal aortic aneurysms (AAAs) are misattributed to non-vascular causes, leading to poor outcomes. This post offers an approach to imaging of symptomatic and ruptured AAA's and presents data demonstrating that bedside ultrasound is a powerful tool when this diagnosis is in the differential. 

When Our Minds Lead Us Astray: Cognitive Bias in the Emergency Department

As anyone who has spent time in the ED can attest, emergency physicians are faced with a constant stream of decisions to make. In order to help navigate this challenging milieu of constant decision making, experienced emergency physicians rely on cognitive shortcuts. This post highlights the cognitive biases that creep into medical decision making and cognitive shortcuts, and how to prevent those biases from negatively impacting patient care. 

Priapism: The ED-Focused Approach


Written by: Aaron Quarles, MD (EM Resident Physician, PGY-3, NUEM), Emmanuel Ogele, MS4, Northwestern University Feinberg School of Medicine ; Edited by: Meghan Quigley, MD (NEUM 2017 Graduate); Expert Commentary by: Nelson Bennett, Jr., MD

The Case

An otherwise healthy 36 year old man presents to the emergency department late on a Saturday night. You enter the exam room to find a man who appears anxious and cannot seem to get comfortable. He immediately informs you that he is in the adult film industry and they were doing a shoot earlier in the day. He states that he took Viagra, but was unable to achieve an erection as rapidly as needed. So he injected an intracavernosal prostaglandin E1 with rapid and resolute effect.

Despite the popular refrain to “seek immediate medical help for erections lasting more than 4 hours,” your patient waited until hour 9 before presenting. He was thorough, however, in his attempt to detumesce; employing such strategies as repeated masturbation, warm baths, alcohol, and even cocaine (the latter two may actually cause priapism!).

Physical exam revealed an extremely firm, fully erect penis that was painful to touch. The glans was soft and not discolored. At this point, all the patient can say is, “Please doc, you have to help me.”

A Bit About Priapism

Priapism is most commonly defined as an erection lasting longer than 4 hours and is unrelated to sexual stimulation. Between 2006 and 2009, somewhere between 5 and 8 visits per 100,000 male subjects to the emergency department (ED) in the United States were due to priapism. In adult males, erectile dysfunction drugs are the usual culprit, accounting for up to 25% of presentations. There is also a notable increase in incidence during the summer months and in patients with sickle cell disease, leukemia, pelvic tumors, & trauma [1,2,3].

What is the pathophysiology behind this condition?

Ischemic priapism occurs secondary to obstruction of venous outflow. The nitric oxide-phosphodiesterase-5 (NO-PDE5) pathway has been implicated in the pathogenesis of ischemic priapism. Dysregulation of this pathway leads to failure to control vasodilation, which in turn leads to prolonged arterial inflow and subsequent obstruction of venous outflow. This causes prolonged erection and ischemia in the penis [3,4].

Non ischemic priapism is not caused by obstruction but rather is due to extravasation of blood into the corpus cavernosum from an arterial fistula. This is less common than the ischemic variant and often happens in the setting of trauma to the perineum (think bicycle seats and other straddle injuries).

A third type of priapism, known as stuttering priapism, represents unwanted intermittent erections usually lasting 3 hours and confined mostly to the sickle cell population. Given its veno-occlusive pathophysiology, stuttering priapism is akin to a self-limited ischemic priapism. These patients are sometimes managed with self-injection of sympathomimetic agents.

How can I distinguish between the types of priapism and why is it important to do so?

It is important to distinguish ischemic from non-ischemic priapism because ischemic priapism is a urologic emergency. This is the first step in management. In ischemic priapism, microscopic changes begin to occur at 4 hours of persistent erection and irreversible fibrotic damage occurs after 24 hours. 90% of cases lasting over 24 hours develop erectile dysfunction with severe impairment in sexual function, which is why early intervention along with counseling the patient on likely outcomes is critical.

Is a physical exam necessary for patient presenting with priapism?

Although presentation is usually self-evident, a fast, focused physical examination of the genitals, perineum and abdomen are warranted. Ischemic priapism will usually present with a painful, tender and a fully rigid phallus. Non-ischemic is usually less rigid and less painful. Abdominal and perineal inspection are helpful to rule out any other traumatic injuries.

Management in the ED

Ischemic Priapism

Once the diagnosis of ischemic priapism has been made, intervention is required to prevent long term dysfunction. Underlying conditions such as sickle cell, should be considered and treated as appropriate (hydration, O2 etc), but they should not delay treatment of priapism. A general approach to management of ischemic priapism is demonstrated below:

Analgesia → Systemic Vasodilators → Direct Vasoconstrictor → Aspiration/Irrigation → Urologic surgery

 Provide oral or parenteral analgesia as appropriate. You may consider systemic vasodilators such as terbutaline (Roberts and Hedges recommends 0.25 to 0.5 mg subQ q15minutes; or 5mg PO once). However, the AUA guidelines suggest no indication for oral systemic vasodilators given limited efficacy. And let’s be honest, the next steps provide significantly more bang for your buck.

Both the European and American Urological Associations recommend cavernosal aspiration and intracavernosal sympathomimetic injection as the treatment of choice. When sympathomimetic injection was added to aspiration and irrigation there was a significant associated increase in resolving priapism [7].

But first, provide local anesthesia. A dorsal penile nerve block can be achieved using a 27-gauge needle and 1% lidocaine (without epinephrine). Raise a skin wheal at the 10 and 2 o’clock positions of the penis as close to the base as possible. Inject through the wheals in a medial direction, being careful to avoid cavernous artery injury. Alternatively a subcutaneous ring block over the dorsal aspect of the penis is effective. Or simply anesthetize the skin on either side of the mid penile shaft where you anticipate entering for aspiration. Be careful to avoid superficial veins.


Next, sterilely attach a 19 or 21 gauge butterfly needle to a syringe or tubing irrigation system of your choice (a useful video demonstrating a convenient way to set up aspiration and irrigation tubing by Dr. Larry Melick ).

Direct the butterfly needle into the now anesthetized 10 or 2 o’clock position of your choice and begin to aspirate. Advance carefully until you get return of dark venous blood. The corpora communicate, so in most cases, only one side needs to be aspirated. If one side isn’t working, try the other. After about 30-60 cc’s of blood are removed, if priapism persists, irrigation with 10-20 ml aliquots of saline or a diluted phenylephrine solution may be attempted. Continue with this approach until the dark venous blood becomes bright red or until flaccidity is achieved.  

Alternatively, direct injections of phenylephrine diluted to a concentration of 100-500 mcg/mL dosed in 1 mL injections can be performed every 3-5 minutes. Treatment failure is considered after one hour of these injections. Patients should be placed on a cardiac monitor while administering these medications given the risk of systemic effects (severe hypertension, dysrhythmia). Proceed with caution in those patients with such underlying conditions.

If these methods fail, urgent urological consultation is required for possible placement of a corpus cavernosum-spongiosum shunt.


Pearl: Phenylephrine is less capable of binding its receptor in acidotic conditions. Thus in patients presenting with 2-3 days of sustained erection, although one should try Phenylephrine as first line, keep in mind this patient will most likely need surgery and should be moved to the OR faster. 

Pearl: For patients with a positive history of sickle cell disease, ischemic priapism is managed in the same way it is when caused by other etiologies. In addition, narcotic analgesia, IV hydration, supplemental oxygen, and alkalization is indicated. 


Non – ischemic Priapism

Non-ischemic priapism is not an emergency. Management consists of observation with the expectation that it will resolve spontaneously.

Pitfall: Injection of sympathomimetics is not recommended as arterial flow will distribute the drug promptly into systemic circulation. In the setting of trauma, other injuries should be managed accordingly. If non – ischemic priapism does not resolve spontaneously, it can be treated by embolization of the fistula in the IR suite [10].


Following successful aspiration, observation is recommended. The patient may be sent home with urology follow up.

Pearls and Pitfalls:

  • A good history can often distinguish between ischemic and nonischemic priapism
  • Time is functional penis
  • Providing proper analgesia is critical, dorsal penile nerve block makes you and your patient’s life easier
  • Intracorporeal injection = intravenous injection (patients should be placed on a monitor when administering vasoactive agents & caution should be taken in severe hypertension, dysrhythmias, etc)
  •  Be mindful that this can be embarrassing and traumatic for patients so care should be taken in addressing the patient as a whole

Expert Commentary

Definition and Etiology

Table 1: Causes of Priapism

Priapism, a prolonged erection lasting more than 4 hours in the absence of sexual stimulation, is a urologic emergency that can result in ischemia, corporal fibrosis, and erectile dysfunction[15].   The duration of corporal ischemia results in variable reversible and irreversible smooth muscle and endothelial injury with histologic changes seen by 12 hours[16].  After 48 hours of ischemia, there is permanent smooth muscle cell death and erectile dysfunction[16-18].  Incidence of all-cause priapism has been reported between 0.3 per 100,000 person-years up to 2.9 per 100,000 person-years[19]

Although the etiology of priapism is not completely understood, it is believed to be a failure of detumescence[17].  Many disease states have been associated with priapism, including hematologic disorders, malignancy, neurologic disorders, trauma, infection, medications, recreational drugs (see Table 1)[15, 17].  Evaluation should include a complete history, physical exam, CBC with differential, hemoglobin electrophoresis, and urine toxicology screen.


For the proper management of priapism, it is important to distinguish between ischemic and non-ischemic subtypes.  Ischemic priapism is comparable to a compartment syndrome causing hypoxia of the corpora cavernosa that is typically painful and requires emergent intervention to preserve erectile function.  Non-ischemic priapism is a high-flow state that is typically not painful and resolves spontaneously.  Non-ischemic priapism is more often associated with trauma.  A cavernous blood gas can be performed to differentiate the two.  Patients with ischemic priapism will have hypoxia with pH <7.25, pCO2 >60 mmHg, and pO2 >30 mmHg.  Blood gas results for patients with non-ischemic priapism will be consistent with normal arterial blood gases.  The blood gas on a detumesced penis would be consistent with a mixed venous blood gas.[15]

The practical aspects of priapism treatment deserve special comment.  Understand that the patient will be embarrassed, anxious, and in pain. Do everything needed to ensure patient comfort and privacy.

  1. Prior to performing any treatment, obtain informed consent for treatment of priapism.
  2.  Place patient on a cardiac and BP monitor.
  3. Administer a dorsal penile nerve block with 1-2% lidocaine using a 25-27G needle. 
  4. Insert the needle at the base of the penis at the 10 o’clock position. Advance the needle towards the opposite side of the shaft (2 o’clock). Make sure that you have not entered the corpora by gently aspirated.
  5. Deposit 10 mL of lidocaine into the penile shaft. Note the distention of Buck’s fascia when injecting the lidocaine. Allow approximately 10 minutes for the local anesthesia to reach full effect. 
  6. Insert a 16 or 18 gauge needle into the penile shaft and aspirate 20 to 30 mL of blood. Irrigation with a saline solution is not routinely recommended as it rarely results in faster detumescence.
  7. Next, inject 1 mL of a diluted phenylephrine concentration (100-500 mcg/ml). This phenylephrine solution may be injected in 1 mL aliquots - no less than every five minutes
    • Pay special attention to the cardiac and BP monitor as phenylephrine may cause reflex bradycardia and hypertension
    • There is no upper limit in the amount of phenylephrine that can be injected. However, practically it may take 10 to 15 mL to achieve detumescence or to decide that surgical intervention is needed.

  8. Once the penis is detumesced, it should be wrapped loosely with gauze and non-adhesive dressing (Coban).
  9. The patient should be monitored in the emergency department for at least another hour to ensure continued penile detumescence.


Nelson Bennett, Jr, MD

Associate Professor, Department of Urology, Northwestern University, Feinberg School of Medicine 

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How to Cite this Blog Post

[Peer-Reviewed, Web Publication] Quarles A, Ogele E, Quigley M(2017, July 4). Priapism: The ED Focused Appropach.  [NUEM Blog. Expert Commentary By Bennett N]. Retrieved from


  1. Nationwide emergency department visits for priapism in the United States. Flum ASCashy JZhao LCMcVary KT. J Sex Med. 2013 Oct;10(10):2418-22.
  2.  Incidence of priapism in emergency departments in the United States. Roghmann F, Becker A, Sammon JD, Ouerghi M, Sun M, Sukumar S, Djahangirian O, Zorn KC, Ghani KR, Gandaglia G, Menon M, Karakiewicz P, Noldus J, Trinh QD J Urol. 2013;190(4):1275. 
  3.  Adeyoju AB, Olujohungbe ABK, Morris J, et al. Priapism in sickle-cell disease: Incidence, risk factors and complications — an international multicenter study. BJU Int 2002;90:898-902
  4.  Pryor J, Akkus E, Alter G, Jordan G, Lebret T, Levine L, Mulhall J, Perovic S, Ralph D, Stackl W Priapism. J Sex Med. 2004;1(1):116. 
  5. Arthur L Burnett Trinity J Bivalacqua. Priapism: current principles and practice. Urologic clinics of North America. 2007, Vol.34(4), p.631-42, viii
  6. Pryor JP, Hehir M. The management of priapism. Br J Urol. 1982;54(6):751. 
  7. Montague DK, Jarow J, Broderick GA, Dmochowski RR, Heaton JP, Lue TF, Nehra A, Sharlip ID, Members of the Erectile Dysfunction Guideline Update Panel, American Urological Association. American Urological Association guideline on the management of priapism. J Urol. 2003;170(4 Pt 1):1318. 
  8. Salonia A, Eardley I, Giuliano F, Hatzichristou D, Moncada I, Vardi Y, Wespes E, Hatzimouratidis K; European Association of Urology. Guidelines on Priapism. Eur Urol. 2014 Feb;65(2):480-9. doi: 10.1016/j.eururo.2013.11.008. Epub 2013 Nov 16.
  9. Dittrich A, Albrecht K, Bar-Moshe O, Vandendris M.Treatment of pharmacological priapism with phenylephrine. J Urol. 1991;146(2):323. 
  10. Sullivan P, Browne R, McEniff N, Lee MJ. Treatment of "high-flow" priapism with superselective transcatheter embolization: a useful alternative to surgery. Cardiovasc Intervent Radiol. 2006;29(2):198.
  11.  Rosen’s. Genitourinary and Renal Tract Disorders
  12.  Roberts and Hedges
  13. Spycher MA, Hauri D. The ultrastructure of the erectile tissue in priapism. J Urol 1986;135(1):142.
  14. Uptodate. Priapism.
  15. Montague, D.K., et al., American Urological Association guideline on the management of priapism. J Urol, 2003. 170(4 Pt 1): p. 1318-24.
  16. Spycher, M.A. and D. Hauri, The ultrastructure of the erectile tissue in priapism. J Urol, 1986. 135(1): p. 142-7.
  17.  Bivalacqua, T.J. and A.L. Burnett, Priapism: new concepts in the pathophysiology and new treatment strategies. Curr Urol Rep, 2006. 7(6): p. 497-502.
  18. Broderick, G.A., et al., Priapism: pathogenesis, epidemiology, and management. J Sex Med, 2010. 7(1 Pt 2): p. 476-500.
  19.  Eland, I.A., et al., Incidence of priapism in the general population. Urology, 2001. 57(5): p. 970-2.



Posted on July 3, 2017 and filed under Urology.

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