A 32-year-old female presents to the emergency department with right ankle pain after a high-speed motor vehicle accident. On exam, she is noted to have ecchymosis and swelling over the distal foot, and pain with ankle dorsiflexion and plantarflexion. An x-ray is obtained as shown above (Image 1. Case courtesy of Dr. Charlie Chia-Tsong Hsu, Radiopaedia.org, rID: 18235).
A 35-year-old male felt a painful “pop” in his posterior left lower leg while playing football. Afterward, his “foot didn’t work right anymore.” X-ray of the left ankle and tib/fib was normal but he was unable to ambulate. You plan an ultrasound over the area of maximal tenderness and discover the above image (Image 1.Ultrasound of the left posterior ankle 11cm proximal to the calcaneal insertion of the Achilles tendon. Case courtesy of Robert Lystrup.)
A 6-year-old boy with no past medical history presented when his parents noticed facial petechiae after picking him up from school. He had a series of four recent upper respiratory infections within four months since starting public kindergarten. He occasionally also complains of leg pain.
General: Non-toxic, cooperative child
Skin: Petechial rash in periorbital and infra-auricular areas
HEENT: Normal; no lymphadenopathy
Musculoskeletal: Normal strength and range of motion
Hemoglobin: 12.6 g/dL
White blood cell (WBC) count: 6.7×103/mL
Platelets: 352,000/mL
Increased pressure in the dermis from actions such as extended Valsalva maneuver, vomiting, crying, or coughing.
This child had a stressful day in kindergarten. He was holding his breath for extended periods of time to suppress crying. The increased pressure caused the facial petechiae, which was completely unrelated to his recent viral infection or growing pains
Take-Home Points
Figure 1: Initial radiographs in the ED with the elbow slightly flexed.
Figure 2: AP and lateral radiographs of the elbow.
An 18-year-old male presents with a painful and swollen left thumb. He removed a splinter from his finger a few days ago however, 2 days after removal, he began to experience edema and pain that has progressively gotten worse. An image of his finger is shown above (Image 1. Picture courtesy of Rosh Review [1]).
A 44-year-old female presents to the emergency department after noticing swelling of her tongue and face, specifically the cheeks and periorbital area. She states the swelling began two weeks ago and has progressively worsened. She also complains of redness.
Succinylcholine is frequently used in the ED to facilitate intubation, but it may be avoided in some cases due to the risk of hyperkalemia. The underlying physiology of this effect appears to be directly related to its therapeutic mechanism of action. When succinylcholine binds to and activates acetylcholine receptors, it leads to an influx of sodium and calcium and and an efflux of potassium into the extracellular space [1]. Additionally, when these acetylcholine receptors are immature or denervated, it seems that these channels may stay open significantly longer, allowing for an increased amount of potassium to exit the cell, leading to an increased risk of hyperkalemia.
Based on multiple studies that included patients with normal renal function, succinylcholine leads to a serum potassium increase of ~0.5 mEq/L [2-4]. This is likely clinically insignificant in most patients. In fact, an ED-based study found a variable response with serum potassium increasing in 46 cases, decreasing in 46 cases, and not changing in 8 cases [3]. It seems that even patients on chronic dialysis are not at increased risk of developing clinically-significant hyperkalemia from succinylcholine [5].
So, when should succinylcholine potentially be avoided specifically due to hyperkalemia concerns [6]?
In patients for whom succinylcholine is determined to be not an option, non-depolarizing muscular blocking agents (NMBAs), such as rocuronium, are still safe and do not lead to hyperkalemia.
Read other articles in the EM Pharm Pearls Series and find previous pearls on the PharmERToxguy site.
