This study will evaluate the pharmacokinetics of antifibrinolytic drug epsilon-aminocaproic acid (EACA) in children undergoing Posterior spinal fusion surgery (PSF) at The Children's Hospital of Philadelphia (CHOP) who receive EACA at the standard dose reported in the literature for this population and currently in use at CHOP.

Posterior spinal fusion surgery (PSF) can be associated with significant blood loss, and perioperative transfusion is common. Various strategies have been employed to decrease intraoperative blood loss and reduce transfusion in children undergoing PSF. The intraoperative administration of the antifibrinolytic drug epsilon-aminocaproic acid (EACA) is one such strategy that has been shown to be effective in this regard. This study will evaluate the pharmacokinetics of EACA in children undergoing PSF at CHOP who receive EACA at the standard dose reported in the literature for this population and currently in use at CHOP.

Inclusion Criteria:

1)Males or females age 8 to 18 years 2)Subjects undergoing posterior spinal fusion surgery 3)Subjects in whom aminocaproic acid administration is planned by the anesthesiology team 4)Parental/guardian permission (written informed consent) and when appropriate, child assent.

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Exclusion Criteria:

1. Wards of the State are not eligible
2. Subjects with a history of abnormal renal function -

Children and Adolescents scheduled to have posterior spinal fusion surgery at The Children's Hospital of Philadelphia