The development of ACS during painful episodes is multi-factorial, but opioid selection may increase this rate. Patients on Nubain were less likely to develop ACS, and they had shorter hospital stays. These results were confounded by use of continuous analgesia infusion with PCA. However, Nubain may provide an alternative to morphine in the treatment of sickle cell pain episodes. A prospective clinical trial comparing these two analgesics would be a preferable next step.