Hi, Thanks for writing to health care magic. There could be several causes for that high heart rate. One of the causes could be sepsis. This means infection in the body. Various investigations like CRP, total blood counts, blood culture and sensitivity help in diagnosis. Your doctor will start her on antibiotics along with other treatment required. Other cause could be because of low oxygen levels that she is having in the body. There are several causes including conditions of the heart which can cause a high heart rate. It is very difficult to comment with out having a physical examination. Continue to ask further queries as required. Hope this helps. Take care. Dr Y V Siva Sankara Murty M.D.(Pediatrics) Associate Professor of Pediatrics