HOMEOSTASIS
� Body fluids and electrolytes play an important role in maintaining a stable internal environment of the body.
� A number of adaptive responses keep the composition and volume of body fluids and electrolytes within the narrow limits of normal to maintain
WATER CONTENT OF BODY
� Water is the primary component of the body, accounting for approximately 60% of the body weight in the adult.
� The two major fluid compartments in the body are intracellular fluid (ICF), or inside the cells, and extracellular fluid (ECF), or outside th
ELECTROLYTES
� Electrolyte composition varies between the ECF and ICF, though the overall concentration of the electrolytes is approximately the same in the two compartments.
� The measurement of electrolytes is important in evaluating electrolyte balance, as well as
MECHANISMS CONTROLLING FLUID AND ELECTROLYTE MOVEMENT
� Many different processes are involved in the movement of electrolytes and water between the ICF and ECF. Some of these include simple diffusion, facilitated diffusion, and active transport. Two forces drive water movement: hydrostatic pressure and osmot
FLUID MOVEMENT IN CAPILLARIES
� The amount and direction of fluid movement between the interstitium and the capillary is determined by the interaction of (1) capillary hydrostatic pressure, (2) plasma oncotic pressure, (3) interstitial hydrostatic pressure, and (4) interstitial oncoti
FLUID SPACING
� Fluid spacing describes the distribution of body water.
� First spacing describes the normal distribution of fluid in the ICF and ECF compartments.
� Second spacing refers to an abnormal accumulation of interstitial fluid (i.e., edema).
� Third spacing
REGULATION OF WATER BALANCE
� Water balance is maintained by water intake and excretion.
� An intact thirst mechanism is important for fluid balance. The patient who cannot recognize or act on the sensation of thirst is at risk for fluid deficit and hyperosmolality.
� An increase in
FLUID AND ELECTROLYTE IMBALANCES
� Fluid and electrolyte imbalances are classified as either deficits or excesses.
o Fluid volume deficit can occur with abnormal loss of body fluids (e.g., diarrhea, drainage, hemorrhage, and polyuria), inadequate intake, or a plasma-to-interstitial fluid
SODIUM IMBALANCES
� Sodium is the major ECF cation and plays a major role in maintaining the concentration and volume of the ECF.
� Hypernatremia is an elevated serum sodium that may occur with water loss or sodium gain.
o Symptoms include those of dehydration and any acco
POTASSIUM IMBALANCES
� Potassium is the major ICF cation and is the major factor in the resting membrane potential of nerve and muscle cells. Changes in potassium balance cause a number of clinical problems.
� Hyperkalemia is an elevated serum potassium level.
o The most comm
CALCIUM IMBALANCES
� The functions of calcium include transmission of nerve impulses, myocardial contractions, blood clotting, formation of teeth and bone, and muscle contractions.
� Calcium is present in the serum in three forms: free or ionized; bound to protein (primaril
PHOSPHATE IMBALANCES
� Phosphorus is a primary anion in the ICF and is essential to the function of muscle, red blood cells, and the nervous system.
� Hyperphosphatemia is an elevated serum phosphorus level. It is usually associated with acute or chronic renal failure.
o Symp
MAGNESIUM IMBALANCES
� Magnesium plays an important role in many essential cellular processes.
� Hypermagnesemia is an elevated serum magnesium level. It usually occurs when a patient with renal insufficiency or failure has an increased magnesium intake.
o Initial clinical ma
ACID-BASE IMBALANCES
� Patients with a number of clinical conditions frequently develop acid-base imbalances. You must always consider the possibility of acid-base imbalance in patients with serious illnesses.
� Normally the body has three mechanisms by which it regulates aci
Alterations in Acid-Base Balance
� Acid-base imbalances are classified as respiratory or metabolic. Respiratory imbalances affect carbonic acid concentrations; metabolic imbalances affect the base bicarbonate.
� Respiratory acidosis (carbonic acid excess) occurs whenever there is hypoven
ASSESSMENT OF FLUID, ELECTROLYTE, AND ACID-BASE IMBALANCES
� Assess for the specific clinical manifestations of fluid, electrolyte, and acid-base imbalances as presented throughout this chapter.
� Other health history data consist of assessment of past health history, medications, surgery or other treatments, and
ORAL FLUID AND ELECTROLYTE REPLACEMENT
� Fluid replacement therapy is used to correct many fluid and electrolyte imbalances. The amount and type of solution used is determined by patient requirements and laboratory results.
� Hypotonic solutions, such as 5% dextrose in water and 0.45% NaCl, pr
Central venous access devices
� Central venous access devices (CVADs) are placed in large blood vessels. This permits frequent, continuous, rapid, or intermittent administration of IV fluids, complex medication treatments, vesicant agents, blood and blood products, and parenteral nutr