The purpose of this study is to identify whether or not the addition of a numbing medicine that is injected directly into the site of the bone marrow procedure can reduce pain and the use of opioid pain medication after bone marrow procedures. The addition of this medicine, called ropivacaine, is the experimental part of this study. This is the first time ropivacaine will be directly injected into the bone marrow site at MSKCC Pediatrics.