Drugs to avoid in G6PD deficiency

Drugs to avoid in G6PD deficiency

Patients with glucose-6-phosphate dehydrogenase (G6PD) deficiency have diminished levels of a key enzyme, G6PD, which protects red blood cells against oxidative stress.  Therefore they should not be prescribed oxidative drugs, which can result in rapid hemolysis of their red blood cells.

Most patients with G6PD deficiency are asymptomatic, but they may have a history of neonatal jaundice, often requiring exchange transfusion, or a history of drug-induced hemolysis.

The following drugs should be avoided.  I have highlighted ones commonly prescribed from an ED setting.

1.  Nitrofurantoin
2.  Pyridium
3.  Sulfamethoxazole (i.e. component of TMP/SMX or Bactrim)
4.  Primaquine
5.  Dapsone
6.  Flutamide
7.  Methylene blue
8.  Sulfacetamide
9.  Nalidixic acid


[Frank JE.  Diagnosis and Management of G6PD Deficiency.  Am Fam Physician 2005:72(7):1277-1282.] 

Corneal ulcer versus corneal abrasion

I recently had a patient with what I thought was a huge corneal ulcer. According to the ophthalmologist who saw the patient, it was actually just a very large corneal abrasion. How do you distinguish a corneal ulcer from an abrasion? Quick review:

Corneal abrasion
A corneal abrasion occurs when the corneal epithelium is damaged from causes such as fingernail scratches, contact lens wear, and foreign objects. The epithelium is richly innervated so corneal abrasions are usually very painful, but onset of pain can be delayed several hours after injury. Symptoms include foreign body sensation, photophobia, and tearing. Vision is usually normal unless the abrasion is in the central visual axis or if there is associated iritis. Slit lamp exam with the cobalt blue light reveals fluorescein uptake in the region of the corneal defect. If the abrasion is > 24 hours old, cell and flare from iritis may be present. However, there is no infiltrate.

Figure 1.  Corneal abrasion

Treatment goals include relieving symptoms and preventing secondary infection. Cycloplegics relax the ciliary body and relieve pain from spasm.  Narcotic pain medicines may be required for analgesia. Do not prescribe topical anesthetics, as they inhibit corneal healing and inhibit the normal corneal protective reflex of blinking when something gets in the eye. Topical antibiotics should be prescribed--erythromycin ointment (for organic source), ciprofloxacin/ofloxacin/tobramycin for contact lens users to cover for pseudomonas.

Patients with very large corneal abrasions should have ophthalmology follow-up within 24 hours; others can follow-up within 48-72 hours.


Corneal ulcer
A corneal ulcer refers to infection of the various layers of the cornea. Corneal ulcers develop when a break of the corneal epithelium results in microbial access to the underlying corneal stroma. Breaks in the corneal epithelium can be caused by trauma, desquamation, or direct microbial invasion. Contact lens use is associated with increased risk of ulcers, particularly caused by Pseudomonas aeruginosa. S. pneumoniae is another common cause of corneal ulcers. Viruses and fungi are causes of corneal ulcers in the setting of immunosuppression.


Figure 2.  Corneal ulcer caused by herpes virus with dendritic lesions

Symptoms include redness, pain, foreign body sensation, photophobia, and blurry vision. Visual acuity may be decreased if the ulcer is in the central visual access or if uveal tract inflammation is present. Pupillary constriction and consensual photophobia may be present due to ciliary spasm. Examination of the corneal reveals a whitish infiltrate (WBCs in the corneal stroma) and sometimes heaped-up edges of the ulcer. On slit-lamp exam, cell and flare and occasionally hypoypon (WBCs in anterior chamber) may be present.

Corneal ulcers are an emergency and patients should be seen by ophthalmology the same day. Treatment includes antibiotic eye drops and cycloplegics. Corneal ulcers should not be patched because of risk of worsening ulceration and perforation


[From Tintinalli's Emergency Medicine: A Comprehensive Study Guide, 7th Ed. Tintinalli, JE, Ed, et al. New York: McGraw Hill, 2011: 594-596]

Salicylate toxicity

Pearls for treatment of salicylate toxicity:


1. Salicylate toxicity typically causes a mixed acid base picture: respiratory alkalosis PLUS elevated anion gap metabolic acidosis. In addition to direct stimulation of the respiratory center, patients also hyperventilate to blow off extra CO2 from their severe metabolic acidosis. If you do wind up intubating a patient with severe salicylate toxicity, remember to continue to hyperventilate them on the ventilator to avoid lethal acidemia.

2. Hemodialysis for most severe ingestions. Indications for hemodialysis in acute salicylate toxicity:
a. Serum level > 120 mg/dL acutely or > 100 mg/dL (6 hours post ingestion)
b. Refractory acidosis
c. Coma or seizures
d. Noncardiogenic pulmonary edema
e. Volume overload
f. Renal failure



From Waseem, Muhammed, et al. Salicylate Toxicity Treatment & Management. Medscape. Available at: http://emedicine.medscape.com/article/1009987-treatment#aw2aab6b6b4. Accessed Dec. 22, 2011.

Tonometry

Tonometry:  How to check intraocular pressure.

I recently had to check intraocular pressure in a patient, and it had been awhile since I had done that.  Hence a good time for a review.

Tonometry is used to estimate intraocular pressure (IOP).  Elevated IOP is important to recognize because if unrecognized and untreated, it can cause visual field loss and blindness.  Sudden elevation of IOP can be seen after trauma and with primary angle closure glaucoma.

Tonometry is indicated:

1.  To confirm a diagnosis of acute angle closure glaucoma.  Patients typically complains of acute aching pain in one eye, blurry vision, red eye, "steamy cornea."  May also present with headache, nausea, vomiting, which can mislead the clinician to search for non-ophthalmologic causes of symptoms.

2.  After trauma.  Retrobulbar hematoma and hyphema can lead to elevated IOP.

3.  To determine baseline IOP in patient with iritis (this can be deferred to ophthalmology follow-up unless that patient has signs of elevated IOP).

Absolute contrindication to tonometry:  suspected globe perforation
Relative contraindication:  corneal defects

Technique for using Tono-pen XL
1.  Apply topical anesthetic to eye
2.  Calibrate Tono-pen and apply sterile latex cover
3.  Position can be sitting upright or supine; Tono-pen just needs to be perpendicular to corneal surface
4.  Hold the probe like a pen and lightly touch to cornea.  You will hear a click and see a reading on the screen.  After 4 valid readings a final beep will sound and the screen will display the average measurement.


Normal eye pressures range from 10-21 mm Hg.


[Clinical Procedres in Emergency Medicine, 4th Ed. Roberts and Hedges, Eds. Philadelphia: Elsevier, 2004]

Perirectal abscess management

Management of Perirectal Abscess:  Drain in the ED or OR?       

Perirectal abscesses almost always begin from obstruction of an anal crypt and its associated anal gland.  The normal anatomic pathway is for anal glands to drain out the anal crypt and into the anal canal.  However, when obstruction occurs, this drainage pattern is blocked, resulting in infection, inflammation, and abscess formation.

Abscesses are usually polymicrobial with both aerobic and anaerobic species. Infection can progress to involve any (or multiple) of the potential spaces in the area:  the perianal space (most common), the ischiorectal space (second most common), the intersphincteric space, the deep postanal space, and the supralevator space.  Patients can present with rectal and perianal pain, often worse with sitting and with defection, localized erythema and tenderness, fever, urinary retention, and signs of sepsis in severe infections.  Deeper abscesses may exhibit fewer localized signs, and tender inguinal adenopathy can be a clue to their presence.


It is crucial that emergency physicians distinguish between an isolated superficial perianal abscess and deeper abscesses.  Liberal use of CT scanning is recommended to aid in diagnosis.  

Isolated perianal abscess without any extension to deeper spaces is the only type of perirectal abscess which should be managed by an emergency physician.  These can be treated with incision and drainage, often with procedural sedation for patient comfort.  Because of involvement of deeper structures and potential for complications, all deeper abscesses should be managed by a general surgeon in the operating room.  

[From Tintinalli's Emergency Medicine:  A Comprehensive Study Guide, 7th Ed.  Tintinalli, JE, Ed, et al.  New York:  McGraw Hill, 2011:  594-596]