To assess the potential risks of cold stress, each participant's body temperature will be obtained pre and post cold liquid exposure. To assess digestive functioning, the temperature of each participant's gastric contents will be obtained pre and post cold liquid exposure by extraction of the gastric content via a naso-gastric tube (NGT). If the child does not have a naso-gastric tube in place at the time of the study, the subjects will be enrolled but no documentation of the stomach content temperature will be obtained.