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Basic Purpose of Intravenous Therapy

Basic Purpose of Intravenous Therapy

                                                                                                            Ashok Kumar Shah


The Process of Fluid and electrolyte balance goes unnoticed in a healthy person. who eats properly, exercises occasionally and maintains tolerable stress levels. However, when the fluid and electrolyte balance is interrupted by illness, stress, surgery or, trauma, the body’s ability to adapt or not to adapt to fluid changes becomes more obvious. Fluid management is an interesting balance of cellular forces. Intravenous therapy is prescribed to persons requiring electrolyte replacement, fluid, calories, vitamins, or other nutritional substancess. It may also be prescribed for administration of medications, chemotherapy or for transfusion of blood products. 

Electrolytes Symbol Normal Range
Bicarbonate HC03 20-30 MeQ/l
Calcium Ca 4.5-5.5 MeQ/l
Chloride Cl 96-106 MeQ/l
Magnesium Mg 1.2 – 2.5 MeQ/l
Phosphate Po4 2.8-4.5 MeQ/l
Potassium K 3.5 – 5.5 MeQ/l
Sodium Na 135-145 MeQ/l

Regulatiors of Fluid Balance :

The greatest single constituent of the human body is fluid, the majority of people pass the whole day without a conscious thought of fluid needs. The feeling of thirst is the front line regulator of fluid need in the healthy person. The young and elderly are more prone to dehydration and fluid loss because the thirst mechanism, located in the medulla, may not effectively respond to their fluid needs.

Under normal circumstances, people lose fluids through perspiration, breathing, evacuation, of faces and urination. An ill person may lose fluids through vomiting, diarrhoea or blood loss. Body fluids are utilized as a medium for food digestion, excertion of waste products, lubrication of joints and membrances and for transportation of oxygen, nutrients and electrolytes in the cells. The intercellular compartment contains approxmately two-thirds of the total body fluid. The remaining fluid is contained in the extracellular spaces, known as the interstitial and intravascular areas. Hydrostatic and osmotic pressure more fluids between the cellular compartment resulting in constant volume of blood for circulation.

Sodium :

The major extracellular cation, promotes retention of the body’s fluids, when a fluid defict exists, less sodium is lost through the kidneys. So more fluid is retained within the body. Sodium not only maintains body water distribution but also promotes neuromusclular function. Helps acid-base balance and influences chloride and potasium levels.

Age Group % of body weight is fluid
Embroy 97%
New born 77%
Adult 60%
Dlerly 54%

Intravenous (IV) fluids have an isotonic, hypotonic or, hypertonic osmolatity. The osmolality of IV solutins is in relation to human plasma which is isotonic. The average serum osmolatity of 290 m osm determines the osmolality of the IV solution. An isotonic solution is 240-340 momsm arrived at by adding or, substracting 50 from the average serum osmolality of 290 mosm because the isotonic solution has the same solute concentration as our plasma. A solution having greater than 340 mosm is hypertonic. The hypertonic solution has a higher solute concentrate than plasma. A solution having less than 240 mosm is hypertonic. The hypotonic fluid has a lower solute concertation than plasma.

When the fluid surrounding the cells is hypertonic or, has more solutes than the cells, osmotic pressure pulls the fluids from the cells. So, hypertonic fluids dehydrate the cells and cause them to shrink and becomes smaller in size.

When the fluid surrounding the cells is hypotonic or, has less soluted then the cell, osmotic pressures pull the fluid into the cells. So, hypotinic fluids swell the cells.

The following is a list of IV fluids their osmolatity and considerations.

Solution Osmolatity usage & limitations
5% Dextrose Isotonic(252 mosm/L) Provides free water to the extracellular and intracellular spaces, as the dextrose in quickly metabolized, promotes renal eliminations of solutes, treats hypernatremia, does not provede electrolytes. one liter is 170 calories.
10% Dextroses Hypertonic(505 mosm/L) osmotic diuretic, provides free water and 340 calories per liter, but no electrolytes, hypertonic solutions may irritate the veins.
25% Dextrose Very hypertonic(1264 mosm/L) Osmotic Diuretic, provides calories but no  electrolytes.
50 % Dextrose Very Hpertonic(1700 mosm/L) Osmotic Diuretic, provides calories but no  electrolytes.
NS 0.9 % Nacl Isotonic(308 M Osm/L) Replaces Nacl deficit and restres/expands extracellular fluid volume.
1/2 NS (0.45 % Nacl) Hypotonic(154 M Osm/L) Assists with renal function provides free water, Na and Cl, replacess normal hypotinic daily fluids losses. but not with electrolytes, replacement.
5% Dextrose1/5 NS Isotonic(315 m osm/L) For daily maintenance of body fluids when cl and Na are required, treats hypernatremia, replaces hypotonic losses, 170 calories per liter.
DNS Hypertonic(559 M Osm/L) To treat fluid volume deficit, for daily maintenance of body fluids and nutrition.
RL Isotonic(273 M Osm/L) Closely resemble the electrolyte composition of normal blood serum and plasma, will need additional K, does not provide calories, or free water used to treat losses from lower GI tract & burns.

Hourly manitenance IV fliud requirements.

Weitht Kg 4 6 8 10 12 14 16 20 30 40 50 60 70
ML/hr 16 24 32 40 44 48 52 60 70 80 90 100 100