Source: Julianna Jung, MD, FACEP, Associate Professor of Emergency Medicine, The Johns Hopkins University School of Medicine, Maryland, USA For unstable patients requiring urgent administration of medications, fluids, or blood products, establishing vascular access quickly is essential. However, there are many factors that can complicate placement of a peripheral intravenous cannula (PIV), and it is extremely common for PIV attempts to fail. PIV placement may be technically challenging in small children, injection drug users, obese people, people with chronic illnesses necessitating frequent vascular access, and in those with burns and other skin conditions. Furthermore, for patients in shock, blood is shunted away from the periphery in order to compensate for impaired perfusion of vital organs, making peripheral vessels difficult to find and cannulate. In these situations, intraosseous (IO) needle placement is an extremely effective alternative to PIV placement, allowing rapid and technically straightforward access to the highly vascularized intramedullary space inside the long bones. From here, medications and fluids are readily absorbed into the bloodstream, permitting stabilization of critically ill patients.