Fluids and Electrolytes- Balance and Disturbance

Fluids and Electrolytes- Balance and Disturbance

60% of body weight consists of fluid (water and electrolytes), the factors influence the amount of body fluid are:
Age, gender, body fat

Body fluid located in two fluid compartments:

a- Intracellular space (ICF)- fluid in cell consists about 2/3of body fluid .Located in the skeletal muscle mass.

b- Extracelluler fluid (ECF)-which distributed as

Intravascular with blood vessels (plasma) consists 3L of 6L blood volume

Transcelluler –located in smallest space contains about 1L, such as cerebrospinal fluid pericardial, synovial, and intraocular, sweat, plural fluid, digestive secretions

Interstitial fluid which surrounds cells consists about 11-12L in adult

Loss of ECF in to space which not contribute to balance between ICF and ECF is referred to third –space fluid shift or third space ,early s&s of a third space fluid shift are : fluid deficit ,decrease urine out put edema , increase P.R ,hypotension ,decrease CVP, increase body weight and imbalance in fluid I&O it usually occurs in ascites ,burns ,peritonitis , bowel obstruction ,bleeding







Electrolytes :

Electrolytes in body fluid are active chemical substance divided to Cations (positive charge ) Anions (negative charge ) expressed by mill - equivalent which defined as being equivalent to the electrochemical activity of 1 mg of hydrogen .

Hydrostatic pressure: the pressure created by the weight of fluid against the wall that contains it. Hydrostatic pressure in vessels results from the weight of fluid and the force resulting from cardiac contraction.


Regulation of body fluid compartments


Osmosis : the process by which fluid move across a impermeable membrane from area of low solute ,concentration to an area of high solute concentration ,the process continues until the solute concentration are equal on both sides of the membrane

Tonicity : the ability of all solute to cause an osmtic driving force that promote water movement from one compartment to another .it control cell hydration , size sodium ,mannitol and glucose . There are three terms associated to osmosis as following :

1- Osmotic : is the amount of hydrostatic pressure needed to stop the flow water exchange depend on solute concentration .

2- Oncotic pressure: is osmotic pressure exerted by protein (albumin).
3- Osmotic diuresis: occurs when urine output increase due to execreation of substance glucose ,mannitol ,or contrast agent in the urine .



Diffusion: is natural tendency of a substance to move from an area of higher concentration to one of low concentration ,it occurs through random movement of ions and molecules , exchange between O2 and CO2 in pulmonary capillary or Na movement from ECF to ICF when concentration is low .

Filtration: hydrostatic pressure in the capillary tends to filter fluid out of the vascular compartment in to the interstitial fluid ,move from water and solute from high hydrostatic pressure area, filtration process allow the kidney to filtrate 180L of plasma /day .

Sodium- Potassium Pump
Routes of Gains and Losses: Kidneys, Lungs, Skin, GIT

Homeostasis Mechanism:
Kidney function, Heart and Blood Vessels, Lung, Pituitary function, Adrenal function