Baylor University Medical Center Proceedings April 2014, Volume 27, Number 2 | Page 59

Methemoglobinemia precipitated by benzocaine used during
intubation
Aasim Afzal, MD, Ruth Collazo, MD, Andrew Z. Fenves, MD, and John Schwartz, MD

Methemoglobinemia is a rare cause of tissue hypoxia that can quickly become fatal without immediate recognition and prompt treatment. It refers
to an increase in methemoglobin in the red blood cells, which can be due
to genetic deficiency of the enzymes responsible for reducing hemoglobin
or can develop after exposure to oxidizing agents or xenobiotics. Local
anesthetics, particularly benzocaine, have long been implicated in the
formation of methemoglobin. Benzocaine is used for teething pain as well
as before invasive procedures such as intubation and transesophageal
echocardiogram. In this case report, we describe a patient with acute
appendicitis who developed severe methemoglobinemia following use of
benzocaine during an emergent intubation. Our objective is to increase
awareness of this rare but potentially fatal complication associated with
the use of this anesthetic.

ethemoglobin is found in small quantities in red
blood cells (RBCs) in the normal physiologic state.
The reductive capacity of the RBCs can be compromised when exposed to overwhelming oxidative
stress. Typical symptoms of methemoglobinemia range from
confusion and dizziness to arrhythmias, coma, and death.
Methylene blue is the recommended treatment for severe cases
of methemoglobinemia. However, for this treatment to be effective, it must be given immediately, which requires prompt
recognition of the condition. We describe a patient who developed severe methemoglobinemia from benzocaine, which was
used during intubation in preparation for surgery. As of 2011,
the Food and Drug Administration had reported 319 cases of
methemoglobinemia related to benzocaine, including seven
cases of death and 32 cases categorized as life-threatening (1).

M

CASE DESCRIPTION
A 56-year-old white woman with known gluten and lactose
intolerance was admitted with severe right-sided abdominal pain,
nausea, vomiting, and fever. Appendicitis was diagnosed and an
uneventful laparoscopic appendectomy was performed. On the
second postoperative day, the patient became hypotensive and
tachypneic and developed bilateral pleural effusions followed
by profound respiratory failure requiring emergent intubation,
which was traumatic and caused significant damage to the oral
mucosa. Benzocaine was used during the intubation procedure.
Proc (Bayl Univ Med Cent) 2014;27(2):133–135

The patient developed significant cyanosis immediately after
intubation. Bloo