Patients with Fontan physiology are at increased risk of developing hypotension during
periods of illness or with anesthesia. These patients have changes in venous capacitance,
compliance, and venomotor tone. When hypotension occurs, the approach to management
requires a careful understanding of these changes and the selection of appropriate,
efficacious vasoactive agents. Vasoconstrictive medications are frequently used to treat
hypotension when patients are refractory to fluid resuscitation. However, most of these
medications have an effect on both the systemic and pulmonary circulations, raising the
vascular pressures of both circuits. However, these patients often do not tolerate abrupt
increases in pulmonary arterial pressures or vascular resistance, and a low
transpulmonary gradient is imperative to maintain cardiac output. The ideal agent would
be one that raises systemic vascular pressure while having a minimal effect on the
pulmonary circulation.
One promising medication for treating hypotension in Fontan patients is vasopressin. One
prior study evaluated the hemodynamic effect of vasopressin in pediatric patients with
pulmonary hypertension. Compared to other vasopressor agents (phenylephrine,
epinephrine), vasopressin increased systemic blood pressure with the least effect on
pulmonary artery pressure. In a second study evaluating the use of vasopressin
specifically for patients undergoing cardiac surgery for the creation of a Fontan, those
who were treated with vasopressin as part of their postoperative management demonstrated
lower transpulmonary gradients than those treated with placebo. Other studies have
evaluated the use of vasopressin in Fontan patients for other clinical outcomes, such as
decreasing postoperative chest tube output. On the basis of these studies, as well as our
clinical experience managing these patients in the operating room, procedural suites, and
in the intensive care unit, the investigator believes that vasopressin is not only safe
but may be the preferred agent for this patient population.
Although vasopressin has been studied extensively in the context of sepsis, post
cardiopulmonary bypass, and other vasoplegic disease states, the use of vasopressin has
not yet been studied in the general population of patients who have Fontan physiology.
The investigator hopes to demonstrate the efficacy of vasopressin as a medication
specifically for these patients, as one that can elevate systemic blood pressure without
compromising cardiac output or having a deleterious effect on the pulmonary vasculature.
