the physiologic effects of ECT?
The goal of
ECT is the generation of a
generalized seizure. This is accomplished by the placement of cuta-neous
electrodes over various points on the scalp through which an electric current
is produced. There is a direct rela-tionship between seizure duration and the
success of ECT treatment. Successful treatments provide seizure activity of
between 15 and 120 seconds. In addition to the local con-traction of the facial
muscles, there is a dramatic systemic hormonal response. Initially a
parasympathetic discharge resulting in bradycardia, heart block, or asystole
may occur. This is typically followed by a sympathetic discharge, which
manifests as tachycardia, hypertension, and increased secre-tions. As a result,
there are increases in cerebral blood flow, cerebral metabolic rate and oxygen
demand, intracranial pressure, cardiac output, and myocardial oxygen demand.
Patients with questionable myocardial reserve as well as organic brain lesions
are at significant risk for ischemic sequelae, cardiac dysrhythmias, and
cerebral hemorrhage. Along with these circulatory effects, there are violent
muscular contractions. The seizures generated by ECT are self-limited, and these
derangements subside within minutes of seizure termination. It is the goal of
the anes-thesiologist to limit the physical manifestations of these physiologic
responses and prevent the sequelae associated with them.