Epinephrine-Induced Arrhythmias
Halothane and, to a lesser extent, other volatile anesthetics
have been shown to sensitize myocardium to the arrhythmogenic effects of epinephrine.
[214]
[215]
[216]
Sensitization is the interaction between volatile anesthetics and catecholamines
that leads to reductions in the threshold for atrial and ventricular arrhythmias.
Sequentially escalating doses of epinephrine produce premature ventricular contractions
and sustained ventricular tachyarrhythmias during halothane anesthesia.[214]
Halothane-epinephrine-induced arrhythmias are attenuated by pretreatment with thiopental,
[214]
presumably by means of effects on the atrioventricular
node or the upper His bundle.[217]
A synergistic
interaction between α1
- and β-adrenoceptors has been strongly
implicated in the pathogenesis of halothane-epinephrine-induced ventricular arrhythmias.
[218]
Stimulation of the α1A
-adrenoceptor
in the His-Purkinje system by epinephrine during halothane anesthesia transiently
slows Purkinje fiber conduction.[219]
[220]
This proarrhythmogenic effect is mediated by phospholipase C and the intracellular
second messenger inositol triphosphate.[220]
Evidence
indicates that enhanced conduction in the Purkinje-ventricular muscle junction accompanied
by simultaneous α1
-adrenoceptor-mediated depression of Purkinje
conduction also plays important roles in halothane-epinephrine-induced arrhythmias.
[221]
The doses of epinephrine required to produce
ventricular arrhythmias during desflurane or sevoflurane anesthesia[218]
[222]
are similar to, but significantly less than,
those observed during administration of isoflurane and halothane, respectively.
Halothane-catecholamine sensitization also promotes abnormal automaticity of dominant
and latent atrial pacemakers.[223]
[224]
[225]
[226]
These
effects may produce premature ventricular contractions and arrhythmias originating
from the His bundle.[223]
Intact sinoatrial node
function reduces the incidence of epinephrine-induced ventricular escape during halothane
anesthesia and is protective against His bundle arrhythmias.[226]
 |
