In addition to providing the fluid and electrolytes, intravenous fluids too are used to supplement parenteral nutrition. When patients are unable to take oral nutrition or fluids for longer period, usually more than weeks, total parenteral nutrition (TPN) is recommended. The TPN is meant to provide all essential nutrients to minimise tissue breakdown and to maintain normalcy within the body. The TPN usually are protein solutions containing high concentrations of dextrose (approximately 20%), electrolytes, vitamins and in some instances insulin.
 
Nitrogen is the primary and most important component of our body’s protein molecules. The protein is thus administered in the form of L-amino acids. The TPN contains both essential and non essential amino acids. The essential amino acids are not synthesised in body. The dextrose increases the caloric value of the solution. Inclusion of dextrose in TPN decreases or prevents the depletion of body’s own protein. Fat is included as a source of essential fatty acids. It also serves as vehicle for fat soluble vitamins. The following electrolytes are commonly included in TPN: sodium, potassium, magnesium, calcium, phosphate and chloride. Calcium as calcium gluconate, potassium as potassium phosphate and sodium as sodium chloride or phosphate are used. Trace elements, also called micronutrients, are required to be included in TPN meant for extended period of time. Zinc, manganese, copper, iron, chromium, molybdenum and selenium are the trace elements. Many of the trace elements are involved as cofactors in enzyme system. For effective use of the administered dextrose and protein, adequate amounts of all vitamins are included.  Both oil soluble and water soluble vitamins are included.



Other uses of intravenous fluids
Besides above uses, the intravenous fluids are also used as vehicles for drug administration through venous route. The formulation and manufacturing of these intravenous fluids are done under regulatory guidance enforcing quality assurance programme following Good Manufacturing Practices. Thus the chances of quality issues are less; never the less, if occurs it can be disastrous. On the other hand, as these products are directly introduced into the blood stream, there are several safety issues of concern while handling and using intravenous fluids.

Isotonic solutions may be infused safely into a peripheral vein while concentrated solutions (hypertonic solutions) are best advised through an indwelling catheter positioned in a large vein. The needle or catheter is placed in a prominent vein of the forearm or leg and firmly taped to the patient so that it will not slip from place during infusion. The main concern of intravenous infusion is thrombus (blood clot) and embolus (clot in circulation) formation induced by needles and catheters. The reactions may occur either due to solution or the administration technique including febrile response. The rapid infusion of hypertonic solutions may cause local pain and venous irritation. Rate of administration should be adjusted according to tolerance. Use of the largest peripheral vein and a small bore needle is recommended. The infusion or flow rate may need to be adjusted according to the need of the patient.
The administration of intravenous fluids can cause fluid and/or solute overload resulting in dilution of serum electrolyte concentration, over hydration, congested states or pulmonary oedema. There is a need of great care infusing solutions with sodium ions especially in patients with congestive heart failure, severe renal insufficiency, and in clinical states in which there is sodium retention with oedema. Similarly there are likely risk of hyperkalemia and renal failure with potassium; phosphate intoxication, hypocalcaemia, tetany with phosphate; and so on.

Some drugs are reported to be adsorbed to the inner linings of intravenous containers and tubing or administration sets. Thus they get lost from aqueous solutions during infusions through plastic intravenous administration sets: chlorpromazine, diazepam, insulin, promethazine, warfarin etc.. It is preferable to use short lengths of small-diameter tubing made of inert plastic to minimise adsorption loss. The advances in infusion technology and computer technology have led to the designing of administration devices with extremely sophisticated drug delivery capabilities.  These new devices provide greater accuracy and reliability of drug delivery than the traditional gravity flow infusion methods. However, the greater convenience and other advantages must be weighed against their price. At the basest minimum: the administration sets must be sterile, pyrogen free and disposable.

While there will be little control of health facilities over the quality of intravenous fluids manufactured, the use of good procurement practices involving inbuilt quality checking in accredited laboratories and checking at receiving points would ensure quality of procured products. A qualified and trained pharmacist in charge of procurement would help the system. The following check points would ensure the quality intravenous fluids and safe administration:

• Procurement from reputed manufacturing units or suppliers.
• Checking of procured products while receiving: clarity or free from particulate matters, leakage.
• Ensuring the use of sterile and disposable administration sets.
• Ensuring correct product:  administration of inappropriate fluid may be detrimental or even fatal to the patient.
• Checking for clarity, presence of particulate matter, precipitate etc.
• Ensuring that the product has not expired. The expired medicines must not be used.
• Ensuring good hand hygiene and aseptic/sterile practice in administration.

The intravenous fluids like electrolyte solutions and total parenteral solutions are life saving products. They are used for correction of electrolyte balance, correction of disturbances in body fluids, as means of providing basic nutrition and vehicle for intravenous administration of many drugs. But they should be used after careful assessment of clinical and biochemical examination of each individual.