2004 OPEN FORUM Abstracts
APPARENT HYPOXEMIA FOLLOWING AWAKE INTUBATION
Charles G. Durbin, Jr.,
MD, FAARC, Amy Wilborn, MD, Department of Anesthesiology,
University of Virginia, Charlottesville, VA 22940.
Case
Presentation: We report a complication from topical
anesthetic administration following awake intubation in a patient for
neck surgery. A 77 year old man with Parkinson’s Disease and a
C1-C2 fusion presented to the operating room with a neck wound
infection for a washout procedure. His neck had been fused with
metal braces and bone graphs approximately 2 weeks previously. Due
to the patient’s potentially unstable neck and the presence of
a rigid neck collar, an awake, fiberoptic intubation (FO) under
sedation, and topical anesthesia, was selected to secure his airway.
A transtracheal injection with 3 cc of 2% lidocaine was administered
following 2 mg of midazolam for sedation. Pharyngeal analgesia was
achieved with several short sprays of Cetacaine Spray®
(benzoxcaine 14%, teracaine 2%, benzoaminobenzoate 2%, and two
preservatives). Due to the patients active gag reflex, an additional
Cetacaine dose was administered. The FO intubation was uneventful
and anesthesia was induced with Desflurane in oxygen by inhalation.
Approximately 10 minutes following induction, the pulse oximeter
(Nelcor 395) indicated a saturation of 91%. Despite employing
recruitment breaths, PEEP and confirming correct tube placement with
the FO bronchoscope, the saturation continued to decline to a value
of 88%. At this time an arterial blood gas was obtained and the
sample also sent for co-oximetry. The following results were
obtained: pH = 7.46, PO2 = 297
mmHg, HCO3- = 25 meq/l, oxyhemoglobin 75%, carboxyhemoglobin 0.3%,
methemoglobin. Since there was no evidence of developing acidosis,
no specific treatment for the identified methemoglobinemia (MET) was
instituted. By the time the patient left the recovery room, his
pulse oximetric saturation was > 95% on 3 l/min nasal O2.
Discussion:Although MET is a reported complication of topical anesthesia, we
were surprised to observe it following a “routine” dose
administration.(1) Consequences of MET relate to the level of MET
and underlying hemoglobin levels. Acidosis is an early sign of
toxicity. Levels less than 40% rarely require treatment with
reducing compounds (methylene blue) or exchange transfusion. This
case illustrates the ability of the pulse oximeter to give a sign of
elevated MET, however other causes of hypoxemia need to be
considered.
1. Kuschner WG, et al.
Benzocaine-associated methemoglobinemia following bronchoscopy in a
healthy research participant. Respir Care. 2000; 45(8):953-6