What is
the treatment for perioperative right ventricular failure?
Following mitral valve replacement, weaning
from cardiopulmonary bypass is sometimes complicated by pulmonary hypertension
and RV failure. Monitoring of the left atrial pressure is helpful in
calculating the pulmonary vascular resistance, because a gradient is often
present between the pulmonary capillary wedge and left atrial pressures.
Factors that predispose to pulmonary vaso-constriction (e.g., hypoxia,
hypercarbia, acidosis, and hypothermia) should be corrected.
The main goals in the anesthetic management of
RV failure are to reduce RV afterload, optimize RV preload, maintain RV
coronary perfusion, and support RV contractil-ity. In the presence of
pre-existing pulmonary hypertension and increased pulmonary vascular
resistance, RV failure will respond favorably to pulmonary vasodilatation.
Drugs with pulmonary vasodilating activity that are used after termination of
cardiopulmonary bypass include nitroprus-side, nitroglycerin, and prostaglandin
E1. However, none of these medications is selective for the
pulmonary circulation and their use may be limited due to their systemic
effects. Milrinone, a phosphodiesterase III inhibitor, increases RV
contractility and has pulmonary vasodilating properties. This pharmacologic
profile makes phosphodiesterase III inhibitors particularly appealing in the
treatment of RV failure. Inhaled aerosolized milrinone is an experimental
therapy that may be used for selective pulmonary vaso-dilatation if preliminary
studies prove its effectiveness.
Inhaled nitric oxide (NO) is an established
therapy for pulmonary hypertension and RV failure following mitral valve
surgery. NO is an endothelium-derived vasodilator and when inhaled selectively
causes pulmonary vascular relaxation. Prostacyclin acts via specific
prostaglandin receptors and has also been shown to reduce pulmonary
hypertension after cardiac surgery. However, the vasodilation is not selective
for the pulmonary vasculature and systemic hypotension may ensue. Various newer
prostacyclin analogs are now given for chronic pulmonary hypertension, and may
be useful for intraoperative use in the future.
Vasopressin or norepinephrine is particularly effective for the
treatment of systemic hypotension in patients with RV failure. Vasopressin
(antidiuretic hormone) is a posterior pituitary hormone that causes
dose-dependent vasoconstric-tion and antidiuretic effects. Epinephrine is the
preferred cat-echolamine in patients with pulmonary hypertension and RV failure
when RV contractility is suspected to be severely impaired.
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