Final answer:
In absence of TPN, intravenous solutions like normal saline or lactated Ringer's solution can be used as they are isotonic and helpful in maintaining proper fluid and electrolyte balance. They are commonly employed in emergency situations to temporarily substitute for lost blood volume.
Step-by-step explanation:
If TPN (total parenteral nutrition) is unavailable, medical professionals can hang intravenous fluids such as normal saline or lactated Ringer's solution as a temporary substitution. When a patient is dehydrated or suffers from acute hemorrhage, these solutions are administered to provide fluids and electrolytes. Both normal saline and lactated Ringer's solution are isotonic, which means they have the same osmotic pressure as blood, hence they are important for maintaining fluid balance without causing cells to shrink or swell.
During emergencies where blood transfusions are necessary but specific blood types are not available, medics may use saline solution intravenously to replace the lost volume of blood. Research is being conducted on artificial blood substitutes, which might include hemoglobin- or perfluorocarbon-based oxygen carriers, to perform the oxygen-transporting function of blood without the red blood cells (RBCs), thus removing the risk of blood-type incompatibility.
In a case of hypokalemia, where there's a need to quickly correct low potassium levels, a specific intravenous (IV) solution such as 0.5% KCl is used.