Final answer:
The treatment plan for a 0.9% NaCl fluid bolus in individuals aged 12 or older consists of providing an isotonic saline solution intravenously for dehydration and to replace fluid and electrolyte losses, especially when significant blood loss is anticipated or observed.
Step-by-step explanation:
The treatment plan for a 0.9% NaCl fluid bolus under the ROSC (Return of Spontaneous Circulation) medical directive for patients who are 12 years or older involves administrating an isotonic saline solution intravenously. This serves to correct dehydration and replenish fluid and electrolyte losses, particularly in cases where there's a high excretion of fluids that contain sodium (Na) and bicarbonate (HCO3). Moreover, when there is a risk of significant blood loss, such as at least 500 mL in adults or 7 mL/kg of body weight in children, establishing appropriate intravenous access and having fluids available for rapid infusion is crucial.