The Annals of Thoracic Surgery, Vol 35, 643-650, Copyright © 1983 by The Society of Thoracic Surgeons
The hemodynamic effect of phentolamine and dobutamine after open-heart operations in children: influence of the underlying heart defect
M Berner, JC Rouge and B Friedli
The hemodynamic effects of phentolamine alone and in combination with
dobutamine were studied in the immediate postoperative period in two groups
of children. Group 1 (N = 6; mean age, 152 months) had open- heart
operation for acquired mitral valve disease. Group 2 (N = 6; mean age, 60
months) had intracardiac repair for tetralogy of Fallot. Before drug
administration, cardiac index did not differ between groups, but patients
with tetralogy of Fallot had a higher heart rate and smaller stroke volume
index; systemic vascular resistance was high in both groups. With
phentolamine (10 micrograms/kg/min), cardiac index and stroke volume index
increased similarly in both groups (+ 13% for cardiac index in Group 1, +9%
in Group 2), while systemic vascular resistance, pulmonary vascular
resistance, and pulmonary wedge pressure decreased. When dobutamine (5
micrograms/kg/min) was added, there was a further increase in cardiac index
in both groups, but it was greater in Group 1 (+17% vs +12%, p less than
0.01, compared with phentolamine alone; +33% vs +22%, p less than 0.01,
compared with control). Systemic vascular resistance remained unchanged and
heart rate increased in both groups, so that the left ventricular stroke
work index increased. Although stroke volume index increased significantly
with dobutamine in Group 1 (+11%, p less than 0.01), it remained unchanged
in Group 2 (+3%, not significant). Thus in Group 2, dobutamine increased
cardiac index only by increasing heart rate. This suggests that the
relatively small, noncompliant left ventricle in patients with tetralogy of
Fallot cannot further respond to inotropic drugs by increasing stroke
volume index.
