The effect of sevoflurane and isoflurane on vasopressor need

In modern anesthesia a variety of volatile anesthetics is available. To decide
which anesthetic should be used in different settings, it is relevant to know
the beneficial and side effects of these anesthetics.
An ideal volatile anesthetic agent should have a number of qualities, which all
contribute to the ease of use and the safety of the patient.
Like virtually all anesthetics, volatile anesthetics are known to decrease
blood pressure. During cardiac surgery, and especially during open-heart
surgery with the use of the cardiopulmonary bypass, maintenance of adequate
blood pressure is important, because severe hypotension is associated with poor
clinical outcomes.

At present both isoflurane and sevoflurane are frequently used in cardiac
anesthesiology.
It is unclear, however, to which degree isoflurane and sevoflurane decrease
blood pressure and whether this effect is predominantly caused by depression of
myocardial contractility or a decrease in systemic vascular resistance (SVR).
The decision as to which of both volatiles should be used during cardiac
surgery is therefore not evidence-based, but is based on personal preference of
the anesthesist.

At present the number of studies comparing the influence of isoflurane and
sevoflurane on blood pressure and systemic vascular resistance is limited.
Moreover, the results presented in the available literature are inconsistent.
Although most publications did not report any significant difference between
isoflurane and sevoflurane, a small number of publications did find a possible
beneficial effect on blood pressure of sevoflurane, compared to isoflurane.

Cardiopulmonary bypass (CPB) offers an unique opportunity to study the effect
of anesthetics on SVR, without concurrent effect of changes in cardiac output.
This is because there is no contraction of the heart during CPB and other
variables that might affect blood pressure, like cardiac index, body
temperature, hematocrite and expired CO2, can be kept stable.

Aim of this study is to determine the effect of isoflurane versus sevoflurane
on blood pressure and systemic vascular resistance.

The study is designed as a crossover randomized double-blinded controlled
single center trial.

patients will be randomized to a 10 minute treatment with isoflurane, followed
by a wash-out period, followed by a 10 minute treatment with sevoflurane, or
the otherway round.

There is no substantial risk, nor are there any benefits for the participants.