It really depends on why you are giving it. Typically, 0.9% NS is used for volume replacement because of its isotonic properties, or to correct a very mild hyponatremia. If volume is the issue, you can consider Lactated Ringers Solution (aka Ringers Lactate), which has some additional electrolytes, or Normosol R solution (which is a NSS base with some additional electrolytes) as these solutions are all isotonic and are used to maintain circulatory volume.

You should bear in mind that isotonic solutions for volume expansion have their limits. Blood products may eventually be required to maintain perfusion, or albumin to pull fluid from interstital spaces back into the circulatory spaces.

If you are treating a burn patient, LR is preferred. If you are administering blood or blood products, 0.9% NS is the ONLY solution that can be used.

There are other concentrations of saline. 0.45% NS is usually used instead of D5W for diabetic patients. 3% saline is seldom used, for very limited purposes.

A potassum salt solution (KCL) is very caustic to the vein, and is typcially used in dilute form (usually 20 mEq per liter, sometimes 40 mEq) to maintain a stable K+ level or correct a very mild hypokalemia (often if the patient is on diuretics). K+ "runs" of 10 mEq in 100 ml are used to correct a serious hypokalemia to prevent lethal cardiac arrhythmias, but again, those concentrations are very caustic to the vein and if you overdose you end up with HYPERkalemia.

The main issue with IV solutions is why the solution is needed. Istonic solutions are given to maintain circulatory volume. Hypertonic solutions will pull fluid OUT of cells, while hypotonic solutions will put fluid INTO cells. If you are a med student, you should consult with your medical faculty on why and when those solutions are used.

I don't know of any other electrolyte salt that is used in place of saline for the purposes I've described above. Any metallic salt that you use will have effects at the cellular level. Magnesium, for example, will affect both the nervous system and the cardiac system: it is a smooth muscle relaxer, a CNS depressant, and affects the electrical functioning of the heart.

It really depends on why you are giving it. Typically, 0.9% NS is used for volume replacement because of its isotonic properties, or to correct a very mild hyponatremia. If volume is the issue, you can consider Lactated Ringers Solution (aka Ringers Lactate), which has some additional electrolytes, or Normosol R solution (which is a NSS base with some additional electrolytes) as these solutions are all isotonic and are used to maintain circulatory volume.

You should bear in mind that isotonic solutions for volume expansion have their limits. Blood products may eventually be required to maintain perfusion, or albumin to pull fluid from interstital spaces back into the circulatory spaces.

If you are treating a burn patient, LR is preferred. If you are administering blood or blood products, 0.9% NS is the ONLY solution that can be used.

There are other concentrations of saline. 0.45% NS is usually used instead of D5W for diabetic patients. 3% saline is seldom used, for very limited purposes.

A potassum salt solution (KCL) is very caustic to the vein, and is typcially used in dilute form (usually 20 mEq per liter, sometimes 40 mEq) to maintain a stable K+ level or correct a very mild hypokalemia (often if the patient is on diuretics). K+ "runs" of 10 mEq in 100 ml are used to correct a serious hypokalemia to prevent lethal cardiac arrhythmias, but again, those concentrations are very caustic to the vein and if you overdose you end up with HYPERkalemia.

The main issue with IV solutions is why the solution is needed. Istonic solutions are given to maintain circulatory volume. Hypertonic solutions will pull fluid OUT of cells, while hypotonic solutions will put fluid INTO cells. If you are a med student, you should consult with your medical faculty on why and when those solutions are used.

I don't know of any other electrolyte salt that is used in place of saline for the purposes I've described above. Any metallic salt that you use will have effects at the cellular level. Magnesium, for example, will affect both the nervous system and the cardiac system: it is a smooth muscle relaxer, a CNS depressant, and affects the electrical functioning of the heart.

Beside the points described by Amy , there are issue of compatibility if you were to dilute a drug in a solution for IV infusion. For example Paracetamol is usually diluted in both Sodium chloride 0.9% or Glucose 5% but for Phenytoin, only NSS is suggested. There are possibility of Precipitation and change in stability and concentration. All of these could cause problem in patient therapy, such as thrombophlebitis, skin sloughing or necrosis caused by extravasation or pyrogenic reaction.

For further information I suggest reading BNF (Intravenous additives section).

Amy has a very good overview of the subject.

Just to add a point in use of 3% saline, also reffered to as hypertonic saline, its true its rarely used , as in dilutional hyponatremia. In clinical practice , patients who undergo transurethral resection of the prostate gland where 5% dextrose is used as irrigation fluid, as a complication they may develope hyponatremia.

Without going into details, if you are using it for volume depletion colloids can be used instead of crystalloids

Amy answered very well indeed. the only thing I would add is that NaCl is very commonly used to maintain isotonic solutions upon dilution because they are the most common ions in the blood and so less likely to make a significant difference to the homeostasis. If you need to use a different ion combination you need to understand the physiology involved and be sure you know the consequences. All bioavailable ions are used for specific purposes by the body, so these need to be considered.