Endocrine function following Heart Surgery in Infants less than 3 months of age.

This observational study aims to further the understanding of how the endocrine system recovers following congenital heart surgery. Infants less than 3 months of age have more deaths and complications following congenital heart surgery than older children and adults. They have immature organ systems and may not be able to respond as rapidly as older children to the critical illness that congenital heart surgery causes. The study requires extra blood samples to be taken in addition to the routine blood tests that are taken during the recovery period in the paediatric intensive care unit. These blood samples will be obtained from indwelling lines that the patients will have in place. The test results will be analysed to delineate what an acceptable range for thyroid and adrenal hormones is in this age group following congenital heart surgery, to assess the association of low hormone levels and poor outcome measures, and to identify a group of patients for enrolment in future studies of hormone replacement.