The more than 40 inpatient beds at Boston’s Tufts Children’s Hospital will be converted to much-needed ICU and medical/surgical beds for adults. The hospital’s operator, Wellforce Health System, said in a statement Thursday that pediatric patients will be referred to Boston Children’s Hospital, under a letter of intent to work together expected to become effective July 1, subject to regulatory approval. Wellforce says the move is being made because as fewer children need hospitalization, and those who do need inpatient treatment require highly advanced care, the number of adult patients in need of highly specialized care has soared.