Med Surg - Fluid/Electrolyte Imbalances

• Filtration
• Diffusion
• Osmosis

Note: these all occur in the in the intercellular spaces.

Filtration

Blood pressure; it moves whole blood from the heart to capillaries where filtration can occur to exchange water, nutrients and waste products and tissues.

Hydrostatic pressure

• volume of blood on the right side of the heart increases greatly because the right ventricle is too weak to pump blood efficiently into the pulmonary blood vessels. 
• blood backs up into venous system
• venous hydrostatic pressure rises
• capillary hydrostatic pressure rises until it is higher than the hydrostatic pressure of the interstitial space
• as a result, excess filtration of fluid from capillaries into the interstitial space occurs, forming visible edema.

Diffusion

Osmolarity

Osmolality

Osmosis

270 to 300 mOsm/L

300 mOsm/L

Hypertonic

Hypotonic

• extracellular fluid; ECF
• contains about 1/3 (15 L) of total body water

• interstitual fluid; also called third space fluid (blood, lymph, bone and connective tissue water
• transcellular fluids; cerebrospinal fluid, synovial fluid, peritoneal fluid, and pleural fluid

Osmosis and Filtration

• Sodium (Na)      136-145 mEq/L
• Potassium (K)    3.5-5.0 mEq/L
• Calcium (Ca)      9.0-10.5 mg/dL
• Chloride (Cl)      98-106 mEq/L
• Magnesium (Mg) 1.3-2.1 mEq/L
• Phosphorus (P)   3.0-4.5 mg/dL

• 136-145 mEq/L
• elevated: Hypernatremia; dehydration; kidney disease; hypercortisolism
• low: Hyponatremia; fluid overload; liver disease; adrenal insufficiency

• 3.5-5.0 mEq/L
• elevated: Hyperkalemia; dehydration; kidney disease; acidosis; adrenal insufficiencies; crush injuries
• low: hypokalemia; fluid overload; diuretic therapy; alkalosis; insulin administration; hyperadoseronism

• 9.0-10.5 mg/dL
• 2.25-2.75 mmol/L
• elevated: Hypercalcemia; hyperthyroidism; hyperparathyroidism
• low: hypocalcemia; vitamin D deficiency; hypothyroidism; kidney disease; excessive intake of phosphorus-containing foods and drinks

• 98-106 mEq/L
• elevated: Hyperchloremia; metabolic acidosis; respiratory alkalosis; hypercortisolism
• low: Hypochloremia; fluid overload; excessive vomiting or diarrhea; adrenal insufficiency; diuretic therapy

• 1.3-2.1 mEq/L
• 0.65-1.05 mmol/L
• elevated: hypermagnesemia; kidney disease; hypothyroidism; adrenal insufficiency
• low: hypomagnesemia; malnutrition; alcoholism; ketoacidosis

• 3.0-4.5 mg/dL
• 0.97-1.45 mmol/L
• elevated: Hyperphosphatemia; kidney disease; hypoparathyroidism; acidosis; hypocalcemia
• low: Hypophosphatemia; chronic atacid use; hyperparathyroidism; hypercalcemia; vitamin D deficiency; alcoholism; malnutrition

Reference Ranges

•                60-90 years              >90 years
• Ca          9.0-10.5 mg/dL       8.2-9.6 mg/dL
• Cl           98-106 mEq/L         98-111 mEq/L
• Mg           1.3-2.1 mEq/L        1.3-2.1 mEq/L
• P            3.0-4.5 mg/dL        3.0-4.5 mg/dL 
• Na         136-145 mEq/L        132-146 mEq/L

• loss of elasticity
• decreased turgor
• decreased oil production
• result: skin becomes an unreliable indicator of fluid status, especially the back of the hand; dry, easily damaged skin

• decreased glomerular filtration
• decreased concentrating capacity
• result: poor excretion of waste products; increased water loss, increasing the risk for dehydration

• decreased muscle mass
• result: decreased total body water; greater risk for dehydration

• diminished thirst reflex
• result: decreased fluid intake, increasing the risk for dehydration

• Adrenal atrophy
• result: poor regulation of sodium and potassium, predisposing the patient to hyponatremia and hyperkalemia

a rising blood osmolarity or a decreasing blood volume

400 to 600 mL

insensible water loss

• 500 to 1000 mL/day
• this loss increases greatly during thyroid crisis, trauma, burns, states of extreme stress, and fever.

• Aldosterone
• Antidiuretic Hormone
• Natriuretic Peptide

• Hormone secreted by the adrenal cortex when sodium levels in the ECF are decreased
• prevents both water and sodium loss

• acts on the kidney nephrons; triggering them to reabsorb sodium and water from the urine back into the blood
• this increases blood osmolarity and volume
• prevents excessive kidney excretion of sodium
• helps prevent blood potassium levels from becoming to high

• produced in the brain
• stored in the posterior pituitary gland
• release from the posterior pituitary is controlled by the hypothalmus in response to changes in blood osmolarity.

• acts directly on kidney tubules and collecting ducts, making them more permeable to water
• more water is reabsorbed by the tubules and returned to the blood decreasing blood osmolarity by making it more dilute

Natriuretic Peptide

BNP: brain natriuretic peptide

• secreted in response to increased blood volume and pressure
• NP binds to receptors in the nephrons creating effects opposite of aldosterone
• Kidney reabsorption of sodium is inhibited while glomerular filtration is increased; causing increased urine output

• blood pressure
• blood volume
• blood oxygen levels
• blood osmolarity (related to Na concentration)

Renin

Kidneys; special cells in the kidney tubule in an area of the nephron known as the juxtaglomerular complex

• any change in the blood that indicates to the kidney that tissue and organ perfusion are at risk. ie.
• Low blood pressure
• Low blood volume
• Low blood oxygen
• Low blood Na level

Renin activates-------> Angiotensinogen: when activated is Angiotensin I----->Agiotensin I is acted on by ACE (angiotensin-converting enzyme)----> ACE converts Angiotensin I into Angiotensin II: most active form of Angiotensin I

• 1. Causes constriction of arteries and veins throughout the body
•   result: increased peripheral resistance & reduced size of vascular bed; raises blood pressure without adding blood volume
• 2. Constrict the size of the arterioles that feed the kidney nephrons
•   result: lower glomerular filtration rate & reduced urine ouput preventing further water loss which helps raise blood pressure
• 3. Cause adrenal glands to secrete aldosterone
•   result: kidneys reabsorb water and Na, preventing them from being excreted which allows more water and sodium to be returned to the blood increasing blood pressure and volume.

Maintenance of adequate tissue perfusion by increasing blood pressure and volume.

because the RAA pathway is greatly stimulated when a patient is in shock or stressed as in surgery.

• Diuretic drugs
• ACE inhibitors
• ARBs

• hypertension management
• they increase the excretion of Na so that less is present in blood, resulting in lower blood volume

• hypertension management
• disrupt the renin-angiotensin II pathway by reducing the amount of angtiotensin-converting enzyme (ACE) made so that less angtiotensin II is present.
• with less angiotensin II present there is less vasoconstriction and peripheral resistence, less aldosterone production, and greater excretion of water. All leading to decreased blood volume and blood pressure.

• a class of drugs to manage hypertension
• Angiotensin receptor blockers
• they disrupt the renin-angiotensin II pathway by blocking the receptors that bind with angiotensin II so that the tissues cannot respond to it and blood pressure is lowered.

500 mL

• Isotonic Dehydration
• most common type of fluid loss problem

• Hypovolemia
• leads to inadequate tissue perfusion

• heart rate increases
• weak peripheral pulses
• decreased pulse pressure
• decreased blood pressure
• orthostatic or postural hypotension
• light-headed or dizziness
• neck vein distension in the supine position
• neck veins flat when sitting
• neck and hand veins are flat even when they aren't raised above heart level

increased rate due to decreased blood volume reduces perfusion and oxygenation

• assess for color, moisture and turgor
• in older person check turgor over the sternum or on the forehead
• check for tenting
• oral mucous membranes will not be moist; may be covered with a thick sticky pastelike coating and may have cracks or fissures.

• confusion
• low grade fever; temp over 102 for more than 6 hrs is especially at risk
• for every degree Celsius increase above normal in body temp a minimum additional 500 mL is lost.

• monitor urine output comparing total output with total fluid intake and daily weights
• urine may be concentrated, with a spec. grav. of 1.030
• urine color is dark amber with strong odor
• output below 500 mL/day for any patient without kidney disease is cause for concern
• Weigh patient same time each day; same scale

• to prevent injury
• prevent further fluid losses
• increase fluid compartment volumes to normal ranges

patient safety: monitor vitals, esp. heart rate and blood pressure. Pt. at risk for falls due to orthostatic hypotension, dysrhythmia, muscle weakness and possible confusion. Assess muscle strength, gait stability and alertness. Fall precautions.

fluid replacement: mild to mod. dehydration is corrected with oral fluid replacement. Urge fluid intake and measure. Divide total amount needed by nurses shifts to avoid overload. Oral rehydration therapy.

drug therapy: severe or life threatening dehydration requires  IV. Antidiahrreals, antiemetics, antipyretics, and antimicrobials may be used if caused diahrrea, vomiting, or fever.

• Excessive fluid replacement
• kidney failure
• heart failure
• long term corticorsteroid therapy
• SIADH
• water intoxicatioin
• psychiatric disorders with polydipsia

• normal serum electrolyte
• decreased hemoglobin, hematocrit and serum protein levels.

elevated levels of hemoglobin, hematocrit, serum osmolarity, glucose, protein, blood urea nitrogen and various electrolytes because more water is lost and other substances remain, increasing the osmolarity or concentration of blood (hemoconcentration)

• bounding pulse
• increasing neck vein distention
• presence of crackles in lungs
• increasing peripheral edema
• reduced urine output

Note: check every two hours at least for these manifestations

• Children 1-10 y/o: 31%-41%
• Adult women: 38%-47%
• Adult men: 40%-54%
• Critical values: <15% or >60%

• Adult men: 14-18 g/dL
• Adult women: 12-16 g/dL
• Critical Values: <5g/dL

• Adult: 5-20 mg/dL
• Elderly: 8-21 mg/dL
• Critical Values: >100 mg/dL

• Adult Male: 0.2-0.6 mg/dL
• Adult Female: 0.6-1 mg/dL
• Critical Values: 4 mg/dL

Pottasium

Hypokalemia

• Drugs: diuretics, corticosteroids, digitalis
• increased aldosterone secretion
• cushing's syndrome
• diarrhea and vomiting
• wound drainage
• prolonged nasogastric suction
• heat-induced excessive diaphoresis
• kidney disease impairing reabsorption of potassium
• nothing by mouth
• Alkalosis
• hyperinsulinism
• hyperalimentation
• total parenteral nutrition
• water intoxication

Hyperkalemia

• over-ingestion of potassium containing foods or meds
• transfusion of whole blood or packed cells
• adrenal insufficiency (addison's disease, adrenalectomy)
• Kidney failure
• potassium sparing diuretics
• ACE inhibitors
• Tissue damage
• acidosis
• hyperuricemia
• uncontrolled uricemia

• Thready, weak irregular pulse
• weak peripheral pulses
• orthostatic hypotension
• shall, ineffective respirations
• diminished breath sounds
• anxiety, lethargy, confusion, coma
• skeletal muscle weakness, eventual flaccid paralysis
• loss of tactile discrimination
• paraesthesis
• deep tendon hyporeflexia
• decreased motility, hypoactive bowel sounds
• nausea, vomiting, constipation, abdominal distention
• paralytic ileus

• slow weak irregular heart rate
• decreased blood pressure
• skeletal weakness leading to respiratory failure
• early: muscle twitches, cramps, paresthesias, and burning numbness in hands, feet and around mouth
• late: profound weakness, ascending flaccid paralysis in the arms and legs (trunk, head and respiratory muscles become affected when the serum potassium level reaches a lethal level.
• increased motility, hyperactive bowel sounds
• diarrhea

• avocado
• bananas
• cantaloupe
• carrots
• fish
• mushroom
• oranges
• potatoes
• pork, beef, veal
• raisins
• spinach
• strawberries
• tomatoes

Sodium

Hyponatremia

• excessive diaphoresis
• diuretics (high-ceiling)
• wound drainage
• ↓ secretion of aldosterone
• hyperlipidemia
• kidney disease
• low salt diet
• nothing by mouth
• cerebral salt wasting syndrome
• hyperglycemia
• nephrotic syndrome
• heart failure
• excessive ingestion of hypotonic fluids
• psychogenic polydipsia

Hypernatremia

• hyperaldosteronism
• kidney failure
• corticosteroids
• cushings syndrom
• excess oral sodium ingestion
• nothing by mouth
• increased metabolic rate
• fever
• hyperventilation
• infection
• excessive diaphoresis
• watery diarrhea
• dehydration

see pg 89 in Saunders NCLEX book

• Bacon
• Butter
• canned food
• cheese
• frankfurters
• ketchup
• lunch meat
• milk
• mustard
• processed food
• snack food
• soy sauce
• table salt
• white and whole wheat bread

Calcium

Hypocalcemia