Utilization of Bispectral Index (BIS) in an ICU Patient for Titration of Sedation During Neuromuscular Blockade
Mehmet S. Ozcan MD, Dietrich Gravenstein MD
Department of Anesthesiology, University of Florida, Gainesville, FL
Case Report
Introduction
We present a case where high propofol infusion rates and
activity by a patient in an ICU led to use of BIS monitoring.
The BIS monitor contributed to our clinical decision making in
an unexpected way and reiterated the subtleties distinguishing
short- from long-term memory formation.
Case Presentation
A 15-year-old girl with severe tracheal stenosis secondary to
acid ingestion was admitted to our pediatric intensive care unit
following direct laryngoscopy and rigid bronchoscopy with
tracheal dilatation. Previously she had 44 other similar
procedures on almost biweekly intervals. The postoperative
course of all these procedures typically included overnight
sedation in ICU with mechanical ventilation and extubation the
following day. Sedation had been successfully achieved with
infusion of propofol, although with progressively higher rates.
On the day of the procedure, patient was once again transferred
from the OR intubated and mechanically ventilated in pressure
support mode. Propofol infusion at 100 µg/kg/min provided light
sedation, allowing her to follow complex commands and to
communicate through writing. A few hours after surgery she
became increasingly agitated and self-extubated. Stridor,
tachypnea and desaturation unmitigated by conservative measures
resulted in her reintubation and propofol infusion was increased
to 150 µg/kg/min.
The surgical team wished to leave the patient intubated for
several days before repeating the rigid bronchoscopy. A
vecuronium infusion was started to prevent another self-extubation
and BIS monitoring instituted to guide propofol infusion rate. A
target bispectral index range of 50-60 was chosen to offer high
confidence of averting recall. To our surprise, we saw that a
propofol infusion rate of only 50 to 80 mcg/kg-min-1 achieved
that level of sedation. She remained on vecuronium and propofol
exclusively for four consecutive days. Following her return to
the OR for a repeat rigid bronchoscopy and tracheal dilatation,
she again returned to the ICU intubated but was extubated the
following morning.
One week after her discharge from ICU, our patient was
specifically questioned about recall of any events in the ICU.
She denied any recall of her ICU stay, her interactions with ICU
staff or recollection of being awake but weak or paralyzed. Her
only memory was of those several hours just prior to her
transfer from ICU
Discussion
Attainment of an amnestic state is highly desirable during
utilization of neuromuscular blocking agents. Level of
responsiveness to a given sedative agent may not necessarily
correlate with lack of recall. We believe that BIS monitoring is
a valuable tool during neuromuscular blockade to avoid excessive
as well as inadequate administration of sedative agents.
