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January
1998
Sevoflurane
or halothane anesthesia: can we tell the difference?
Bacher
A, Brton AW, Uchida T, Zornow MH; Anesth Analg 1997; 85: 1203-6.
[ see
abstract below ]
Bacher et al are to be congratulated for carrying out an interesting study
which should give us all food for thought. Whenever new drugs are introduced
we are very quick to embrace their "advantages" over old drugs and thus
replace older and cheaper drugs with newer and more expensive drugs. When
desflurane was introduced the manufacturer had thought that this might
represent a "new cyclopropane" and become "the agent" of choice for anesthetic
induction of children. Obviously the pungent odor and propensity for laryngospasm
prevented the hoped for effect in children.
Sevoflurane was the next agent introduced which is truly very acceptable
for the gaseous induction of children and it does result in slightly lower
airway irritability and a slightly more rapid induction than with halothane
but is it really very different? These authors were concerned, as we all
should be, with the approximate 30 fold higher cost when compared with
halothane. Is sevoflurane in fact 30 times better than halothane?
The authors hypothesis was to test whether anesthesiologists could separate
the two agents based on clinical signs and symptoms by hiding the vaporizers
from the anesthetizing team and then making adjustments to anesthetic
concentrations based on MAC multiples as adjusted by another individual
not involved in making patient assessments. Fifty-eight children were
assessed 113 times by 15 faculty and 21 residents in training.
Most interesting was the fact that the anesthesiologists did not correctly
identify the anesthetic agent in 43% of the assessments! Furthermore there
was no difference in the frequency of choosing halothane instead of sevoflurane
or sevoflurane instead of halothane. In this study they also found no
difference in the anesthesiologists' assessment of the quality of induction,
speed of induction, or speed of emergence.
I agree with the authors that we need to assess the role of sevoflurane
in pediatric anesthesia. It is my personal practice to induce with sevoflurane
and then change to halothane for maintenance of anesthesia. Perhaps I
need to reassess my own practice.
Return to the Current Literature Review
Front Page , or read the abstract:
ABSTRACT
This study was performed to evaluate the ability of anesthesiologists to
differentiate between sevoflurane, a newer, more expensive anesthetic, and
halothane.
A total of 113 assesments were made by 36 anesthesiologists on 58 children,
aged 6 mo to 6 yr, scheduled for bilateral myringotomy and tube placement.
All patients received midazolam (0.5 mg/kg per os) approximately
30 min before the induction of anesthesia. Sevoflurane or halothane was
randomly selected for anesthetic induction and maintenance. The anesthesiologists,
who were unaware of the anesthetic being used, were asked to identify the
anesthetic based on clinical signs and to asses the quality of induction,
speed of induction, and speed of emergence using a visual analog scale (VAS;
minimum score = 0, maximum score = 100).
The anesthesiologists correctly identified the anesthetic only 56.6% of
the time. This was not significantly different from the 50% that would result
from random guessing (P = 0.08). Further, there were no significant differences
in VAS scores between the two groups.
This study suggests that in premedicated pediatric patients undergoing brief
surgical procedures, anesthesiologists cannot correctly differentiate between
sevoflurane and halothane. The lack of significant differences in VAS scores
suggests that the speed of induction, the speed of emergence, and the quality
of induction are similar under these clinical conditions. Any purported
benefits of sevoflurane seem to be of minor consequence under the circumstances
studied.
Implications: When the anesthetic halothane or sevoflurane is administered
in a blind, randomized fashion, anesthesiologists could not reliably identify
which drug was being used to anesthetize children for a brief surgical procedure.
These results suggest that the differences between the two drugs in clinical
practice are small and may not justify the additional cost of sevoflurane.
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