The purpose of this pilot study is to prepare for a larger study to determine whether Vasopressin following the Fontan operation will decrease chest tube output and duration.

A pilot randomized, double blinded clinical trial to evaluate the use of vasopressin following the Fontan operation.

Phase one of the study will be a single center pilot study and will be conducted at Advocate Children's Hospital, Oak Lawn IL. This will be a randomized and double blinded. Ten patients will be enrolled with five patients as control group and five receiving Vasopressin. Vasopressin levels will be obtained just prior to initiation of Vasopressin and 48 hours later in the pilot study. Safety and effect size will be evaluated after this pilot study.

Drug administration protocol:

Vasopressin at a dose of 0.4 mU/kg/min will be started on subjects in the study group while coming off cardiopulmonary bypass. The dose of Vasopressin will not be titrated. Study drug drip will infuse for 48 hours after which will be discontinued.

The placebo group will be receiving normal saline at the same rate of the vasopressin group. The treating physician will be blinded.

Inclusion Criteria:

• Subjects between 1.5-7 years old undergoing Fontan operation.

Exclusion Criteria:

• Patients with a planned fenestrated Fontan.
• Patients undergoing revision surgery for failing Fontan.
• Evidence of renal insufficiency prior to surgery defined by creatinine >1 mg/dl.
• Planned arch reconstruction at the time of the Fontan procedure

Through study completion, an average of 3 years.