Final answer:
If venous access fails, an intraosseous (IO) needle can be used as an alternative route for administering fluids and medication directly into the bone marrow cavity. This is often employed in emergency situations.
Step-by-step explanation:
If venous access cannot be obtained after three attempts or within 90 seconds, an alternative route for vascular access should be considered. One common alternative is the insertion of an intraosseous (IO) needle, which involves drilling a needle into the bone marrow cavity, usually of the proximal tibia or humerus. This allows immediate access to the vascular system for the administration of fluids and medication. Intraosseous access is often used in emergency situations when venous access is not readily obtainable and can allow for the administration of fluids and drugs directly into the bone marrow, which is then quickly absorbed into the bloodstream.