Study of Fentanyl-Propofol-EMLA of L.M.X4 Technique for Bone Marrow Aspiration

The study focusses on the following primary aims: * To compare 0.5 mg/kg versus 1.0 mg/kg of fentanyl to control pain in patients who have a BMT/LPIT procedure in the context of propofol anesthesia and topical anesthesia with EMLA or L•M•X 4™cream (or when necessary, lidocaine for injection). * To compare placebo versus fentanyl (0.5 mg/kg or 1.0 mg/kg) in these same patients. The first BMT/LPIT for which patients receive any fentanyl will be used in this comparison. The study focusses on the following secondary aims: * To determine which dose regimen ensures best conditions to perform bone marrow aspiration (lack of motion) and maintains hemodynamic and respiratory stability as indicators of adequate levels of analgesia during bone marrow aspiration. * To evaluate the safety and complications for each dose regimen.