Ch. 53: Fluid & Electrolyte Imbalances + Acid-Base Disorders

Osmolality

laboratory value of the concentration of solutes in body fluids; sodium greatest contributor due to its abundance

Tonicity

the relative concentration of IV fluids; the ability of a solution to cause a change in water movement across a membrane due to osmotic forces

Isotonic solutions

have the same concentration of solutes (osmolality) as the blood

Hypertonic solutions

have a greater concentration of solutes than plasma

Hypotonic solutions

have a lesser concentration of solutes than plasma

Osmosis

the movement of water from areas of low solute concentration (low osmolality) to areas of high solute concentration (high osmolality)

Water balance

water intake = water output

Thirst mechanism

primary physiological regulator of fluid intake; occurs when osmoreceptors in the hypothalamus sense a hypertonic ECF (high osmolality)

Fluid output

primarily regulated by kidneys; through RAAS, aldosterone is secreted by adrenal cortex and acts on kidneys, as well as ADH

Aldosterone

hormone secreted by adrenal cortex; causes kidneys to retain Na+ and H2O = increased ECF osmolality

ADH

hormone released during periods of high plasma osmolality; acts directly on the distal tubules of the kidney to increase water reabsorption

Common reasons for fluid loss

- loss of GI fluids (vomiting, diarrhea, etc)

- excessive sweating

- severe burns

- significant blood loss

- excessive renal fluid loss (diuretic therapy or diabetic ketoacidosis)

- surgical procedures

IV replacement fluids

two basic types: colloids and crystalloids

Colloids/plasma volume expanders

proteins/large molecules that remain in the blood for a long time because they are too large to cross the capillary membrane; draw water from cells into plasma

Uses of colloids

hypovolemic shock due to burns, hemorrhage, or surgery

Dextran

synthetic polysaccharide contained in colloids

Plasma protein fraction

solution of proteins composed of albumin & globulin from human plasma; used as a replacement therapy for hypoproteinemia

Crystalloids

IV solutions containing electrolytes and other agents used to replace lost fluids and promote urine output; quickly diffuse across membranes from plasma into ISF and ICF

Dextrose

form of glucose contained in some crystalloids; provides nutritional value and promotes water formation

Hypertonic crystalloids

contain more Na+; draw water from the cells and tissues and expand plasma volume

Hypotonic crystalloids

contain less Na+; cause water to move out of the plasma to tissues and cells, therefore not efficient plasma volume expanders

Normal saline

0.9% NaCl, isotonic, the only IV solution compatible with any blood products

Blood products

include whole blood, packed RBCs, fresh frozen plasma, cryoprecipitate, immune globulins, and platelet infusions

- administered to restore deficient numbers of blood cells or proteins or increase fluid volume

Whole blood transfusion

indicated for the treatment of acute, massive blood loss when there is a need to replace plasma volume as well as supply erythrocytes to increase blood's O2-carrying capacity

- largely replaced by use of blood components

Complications of whole blood transfusion

febrile nonhemolytic and chill-rigor reactions; acute hemolytic transfusion reaction; transmission of infections

febrile nonhemolytic reaction

symptoms of allergic reaction; back pain, low-grade fever, chills, dizziness, urticaria, headache

- Tylenol and Benadryl prn

Hemolytic transfusion reaction

occurs when the client receiving the transfusion develops antibodies against donor RBC antigens

Causes of hemolytic transfusion reaction

- ABO blood type incompatibility

- transfusion-related acute lung injury

Transfusion-related acute lung injury

occurs when the client receives donor antibodies that attack normal granulocytes in the lung; acute respiratory symptoms, may be fatal

Fresh frozen plasma (FFP)

unconcentrated source of all clotting factors, without platelets

Cryoprecipitate

concentrate prepared from FFP

Immune globulins

antibody preparations used to provide an immediate boost to immune system

Nursing implications - colloids

- monitor for fluid volume deficit and excess

- monitor vital signs and hemodynamic status

- contraindicated in renal failure, hypervolemia, severe HF, thrombocytopenia, clotting abnormalities

- caution with active hemorrhage, severe dehydration, chronic liver disease, impaired renal function

Normal serum albumin

prototype colloid; administered IV, rapidly increases the osmotic pressure of the blood and causes fluid to move from tissues to general circulation

- risk of protein overload or hypervolemia

Dextran 40

prototype colloid; polysaccharide that raises the osmotic pressure of the blood, causing fluid to move from tissues to vascular spaces + reduces platelet adhesiveness

- contraindicated in renal failure and severe dehydration

- risk of fluid overload

Signs of fluid overload/hypervolemia

high BP, tachycardia, peripheral edema, pulmonary edema, distended neck veins, dyspnea, cough, cyanosis

Sodium

major electrolyte in ECF; as levels increase, solute particles accumulate and osmolality increases. water will move toward this area = increased BP and volume

- neuromuscular function, acid-base balance, overall fluid distribution

Hypernatremia

serum Na+ > 145 mEq/L; increases osmolality of the plasma and draws fluid from interstitial spaces and cells = cellular dehydration

- thirst, fatigue, muscle twitching, convulsions, weight gain, dyspnea

Causes of hypernatremia

- kidney disease resulting in decreased Na+ excretion

- excessive intake of Na+

- high net water loss (watery diarrhea, fever, burns, inadequate water intake)

- high doses of glucocorticoids or estrogens

Treatment of hypernatremia

- low-salt diet

- rapidly return osmolality to normal and excrete excess Na+; hypotonic fluids for hypovolemia, diuretics for hypervolemia

Hyponatremia

serum Na+ level < 135 mEq/L; nausea, vomiting, anorexia, abdominal cramping > confusion, lethargy, convulsions, muscle twitching, tremors > tachycardia, hypotension, dry skin and mucous membranes

Causes of hyponatremia

- excessive dilution of plasma

- increased Na+ loss due to disorders of the skin, GI tract, kidneys

- excessive ADH secretion or administration of hypotonic IV solutions > increase plasma volume

- burns, excessive sweating, prolonged fever

- GI losses

- diuretic use, kidney disorders

Treatment of hyponatremia

solutions of NaCl

Nursing implications - Na+ replacement therapy

- monitor fluid balance

- monitor serum Na+, urine specific gravity, serum and urine osmolality

- monitor for fluid overload (hypertonic)

Sodium chloride

prototype Na+ replacement fluid; administered during hyponatremia; monitor for hypernatremia: lethargy, confusion, muscle tremor or rigidity, hypotension, restlessness, pulmonary edema

Potassium

most abundant intracellular cation; regulates intracellular osmolality and maintains acid-base balance

Hyperkalemia

serum K+ > 5 mEq/L

- dysrhythmias, heart block, muscle twitching, fatigue, paresthesias, dyspnea, cramping, diarrhea

Causes of hyperkalemia

- excessive consumption of K+

- K+-sparing diuretics, ex. spironolactone

- decreased renal excretion

Consequences of hyperkalemia

dysrhythmias, heart block

Treatment of hyperkalemia

- restrict dietary K+ sources

- lower dose of K+-sparing diuretics

- glucose and insulin (cause K+ to enter cells)

- calcium gluconate or calcium chloride (K+ toxicity on heart)

- sodium bicarbonate (acidosis)

- polystyrene sulphonate (elimination of excess K+)

Hypokalemia

serum K+ < 3.5 mEq/L; muscle weakness, lethargy, anorexia, dysrhythmias, cardiac arrest

Causes of hypokalemia

- high doses of loop diuretics, ex. furosemide

- strenuous muscular activity, severe vomiting, diarrhea

Nursing implications - K+ replacement therapy

- monitor for hyperkalemia

- assess renal function, stop infusion if failure

- monitor ECG

- administer slowly so as not to overload heart and cause cardiac arrest

Potassium chloride

prototype potassium replacement drug; prevents hypokalemia + treats mild alkalosis

- can cause peptic ulcers > dilute

- administer slowly when IV

- assess kidney function

- monitor for hyperkalemia

Magnesium

- second most abundant intracellular cation

- neuromuscular function, metabolism (activates enzymes), cofactor

- most found in bone

- filtered and reabsorbed in loop of Henle

Magnesium sulphate

prototype magnesium replacement drug; treats hypomagnesemia

- CNS depressant > anticonvulsant

- restricted to clients with severe magnesium deficiency

Hypomagnesemia

few symptoms until serum level < 1 mEq/L

- general weakness, dysrhythmias, hypertension, loss of deep tendon reflexes, respiratory depression

Causes of hypomagnesemia

- kidney failure

- loop diuretics

- GI malabsorption disorders

- loss of body fluids

Hypermagnesemia

excess Mg2+ caused by advanced renal failure; CNS depression, respiratory depression, hypotension, dysrhythmias, bradycardia, complete heart block, coma

Treatment of hypermagnesemia

calcium salts, furosemide

pH of body fluids

7.35-7.45

Buffers

chemicals that help maintain normal body pH by neutralizing strong acids and bases

- bicarbonate ions

- phosphate ions

Acidosis

pH of plasma < 7.35

- lethargy, confusion, CNS depression, coma, seizures

- rapid RR to rid body of excess acid

Nursing implications - pharmacotherapy of acidosis

- assess arterial blood gases for pH, PCO2 levels, HCO3- levels, PO2, and SpO2

- assess for symptoms of acidosis

- assess for symptoms of alkalosis

Sodium bicarbonate

prototype drug for correcting acidosis; makes the urine more alkaline, aiding in the renal excretion of acidic drugs if OD

- risk of metabolic alkalosis; reversed with KCl or ammonium chloride

- should not be given with hypochloremia or hypocalcemia

Alkalosis

plasma pH > 7.45

- CNS stimulation (nervousness, hyperactive reflexes, convulsions), slow, shallow breathing (to retain acid and lower internal pH)

- treated with NaCl or ammonium chloride

Nursing implications - pharmacotherapy of alkalosis

- assess for metabolic acidosis and ammonium toxicity

- ammonium chloride only when life-threatening

- monitor renal status, I&O

- monitor IV site, infuse slowly

Ammonium chloride

Prototype drug for correcting severe alkalosis; acidifies urine, increases excretion of alkaline drugs and aids with UTIs

- contraindicated in liver disease

Ammonium toxicity S&S

pallor, sweating, irregular breathing, retching, bradycardia, twitching, convulsions