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Febuary
1997
Sevoflurane
depresses myocardial contractility less than halothane during induction
of anesthesia in children.
Holzman RS, van der Velde M, Kaus SJ, Body SC, Colan SD, Sullivan LJ,
Soriano SG;
Anesthesiology 85:1260-1267, 1996.
[ see
abstract below
]
The purpose of this study was to compare the echocardiographic derived
indices of cardiac contractility during induction with 1.0 and 1.5 MAC
sevoflurane and halothane. Twenty unpremedicated children ages 8.9 � 2.9
vs 8.1 � 3.2 yr. were randomized to halothane or sevoflurane. The authors
found that blood pressure and heart rate were stable with both agents.
Systolic blood pressure decreased equivalently with both agents, however
left ventricular shortening fraction and velocity of ventricular shortening
fraction corrected for heart rate decreased with both agents but to a
greater degree with halothane. Systemic vascular resistance was maintained
with halothane but decreased with sevoflurane at 1 and 1.5 MAC.
Interestingly at 1.5 MAC the decrease in systolic pressure observed with
halothane and sevoflurane and the decrease in diastolic pressure seen
with sevoflurane at 1 MAC reverted to baseline suggesting a compensatory
mechanism. The authors conclude that preservation of cardiac contractility
with sevoflurane make it an attractive alternative for inhalation induction
of anesthesia in children.
This is a very interesting paper that may have some important clinical
implications. A gaseous induction of anesthesia in children is often carried
out and then the IV is inserted. Many pediatric patients are particularly
vulnerable at this point. Generally high concentrations of potent agent
are avoided until the IV is inserted and then, as the patient is being
hydrated, a muscle relaxant is administered to facilitate tracheal intubation,
and high levels of potent agent are avoided.
If a child has had an excessively long fasting period, then relative hypovolemia
may exaggerate the normally expected fall in systolic blood pressure,
make insertion of the IV more difficult, and severe hypotension may result.
This study suggests that sevoflurane may offer an advantage in such patients
because there is less myocardial depression.
Unfortunately this study did not control the interval of fasting (6 -
12 hours). I am a bit uncomfortable with stating categorically that sevoflurane
offers a safety net over halothane because the actual change in blood
pressure was identical with both agents. If cardiac contractility is more
adversely affected in the hypovolemic patient then one could reach such
a conclusion.
I await with interest a comparison of children who have had the standard
3 hour fast from clear liquids prior to gaseous induction compared to
age matched controls who have had a 10 - 12 hour fast. Then we might be
able to make a more definitive statement regarding advantages of one agent
over the other.
Return to the Current
Literature Review Front Page, or read the abstract:
ABSTRACT
Background: Cardiovascular stability is an important prerequisite
for any new volatile anesthetic. We compared echocardiographically derived
incidences of myocardial contractility during inhalation induction with
sevoflurane and halothane in children.
Methods: Twenty children were randomized to receive either halothane
or sevoflurane for inhalation induction of anesthesia. No preoperative medications
were given. Myocardial contractility was evaluated at baseline and at sevoflurane
and halothane end-tidal concentrations of 1.0 minimum alveolar concentration
(MAC) and 1.5 MAC.
Results: There were no differences between groups in patient age,
sex, physical status, weight, or height. Equilibration times and MAC multiples
of sevoflurane and halothane were comparable. Vital signs remained stable
throughout the study. Left ventricular end-systolic meridionel wall stress
increased with halothane but remained unchanged with sevoflurane.
Systemic vascular resistance decreased from baseline to 1 MAC and 1.5 MAC
with sevoflurane. Halothane depressed contractility as assessed by the stress-velocity
index and stress-shortening index, whereas contractility remained within
normal limits with sevoflurane. Total minute stress and normalized total
mechanical energy expenditure, measures of myocardial oxygen consumption,
did not change with either agent.
Conclusions: Myocardial contractility was decreased less during inhalation
induction of anesthesia with sevoflurane compared with halothane in children.
Although the induction of anesthesia with sevoflurane or halothane was equally
well tolerated, the preservation of myocardial contractility with sevoflurane
makes it an attractive alternative for inducing anesthesia in children.
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