Fluid Imbalance, Electrolyte, and Acid-Base Disorders

Question 1

Fluid and Electrolyte Balance

Answer 1

• The volume and composition of fluids in the body must be maintained within narrow limits
• Excess fluid retention can lead to hypertension (HTN). heart failure, or peripheral edema
• Depletion leads to dehydration
• Body fluid must contain specific amounts of essential ions or electrolytes and main specific pH

Question 2

Principles of Fluid Balance

Answer 2

• Body fluids are exchanged between intracellular and extracellular compartments separated by semipermeable membranes
  
  • Control of water balance is essential to homeostasis
    
    • Water is 60% total body weight in adults, 80% newborn and 40% older adult
• Water is found in three different fluid compartments:
  
  • Intracellular fluid (ICF) - INSIDE CELL - 40% TBW
  • Extracellular fluid (ECF) Interstitial fluid (ISF) - OUTSIDE CELL - 20% TBW
• There is a continuous exchange, turnover, and mixing of fluids between compartments

Question 3

Osmosis

Answer 3

• Only the solvent molecules (water molecules) pass through a semipermeable membrane from an area or less concentrated to a more concentrated one, equalizing each side of membrane

Question 4

Diffusion

Answer 4

• Both solvent and solute particles move passively from areas pf high to low concentration area until equilibrium is reached.

Question 5

Hydrostatic vs. Osmotic Pressure

Answer 5

The pressures that drive fluid into and out of blood vessels

• Capillaries with their permeable membranes are specifically designed to allow for nutrients, gases, wastes, and fluid between the blood and the tissues
  
  • Edema - fluid outside the blood vessels
• Hydrostatic pressure - drives fluid movement OUT of the blood
  
  • Outward pressure drives fluid out of blood vessels. ICF to ECF.
  • Exerts outward force that pushes water through the capillary membrane pores into the ISF & ICF compartments.
• Osmotic pressure - through osmosis water always flows toward regions that have a higher concentration of solute particles
  
  • In the bloodstream, osmotic pressure is exerted by electrolytes, mainly sodium ions and plasma proteins.
  • The force that pulls water into bloodstream from ICF and ISF.
  • A solution with greater number of particles has higher osmotic pressure.
  • Osmotic pressure opposes hydrostatic pressure.

Major solutes - albumin, sodium (Na+), potassium (K+), phosphate (Po4-), magnesium (Mg++), calcium (Ca++), bicarbonate (HCO3-), and glucose.

Question 6

Oncotic pressure (colloidal oncotic pressure)

Answer 6

• Refers to force exerted specifically by albumin (protein) in blood.
• Total albumin in blood is indicative of the protein nutritional status of the body.
• Normal serum albumin level is 3.1 to 4.3g/dL
• Protein starvation leads to hypoalbuminemia due to low colloid oncotic pressure. Colloid oncotic pressure < hydrostatic pressure lead to edema

Question 7

Osmolality vs Osmolarity

Answer 7

Way to describe a solution: osmoles are used to measure solute concentrations

• Osmolality - number of solute particles per weight of solvent in kilograms
• Osmolarity - number of solute particles per volume of solution in liters
  
  • The unit that measures both Osmolality and Osmolarity is Osmoles or Osm
• Major solutes - albumin, sodium (Na+), potassium (K+), phosphate (Po4-), magnesium (Mg++), calcium (Ca++), bicarbonate (HCO3-), and glucose.
• sodium greatest contributor due to its abundance in most fluids

Osmotic Pressure – the pressure exerted by solutes in solution.

• In the bloodstream, osmotic pressure is exerted by electrolytes, mainly sodium ions and plasma proteins.
• Osmotic pressure is a force that pulls water into bloodstream from ICF and ISF.
• A solution with greater number of particles has higher osmotic pressure.
• Osmotic pressure opposes hydrostatic pressure.

Question 8

Tonicity

Answer 8

Tonicity - Used to describe how 2 solutions separated by a membrane are relative to one another

• Cells have a permeable membrane and are within a solution (blood, interstitial fluid).
• Use tonicity to describe the solution inside of cells and the solution outside of the cell
  
  • Hypo - lower concentration of solute
  • Isotonic - equal parts solute and solvent
  • Hyper - higher concentration of solute

Question 9

Intravenous Solutions

Answer 9

IV Tonicity - the amount of solutes in solution compared with the amount in the blood.

• Hypotonic IV Solution - fewer solutes than blood
  
  • Fluid shifts from ECF to ICF
    
    • Dehydration treatment
    • Avoid with cerebral edema as fluid will shift into cells - ICF
• Isotonic IV Solution - equal parts solutes and blo
  
  • No fluid shift
• Hypertonic IV Solution - higher solutes than blood
  
  • Fluid shifts from ICF to ECF
    
    • Decreased swelling, especially cerebral edema

Question 10

Electrolytes

Answer 10

Electrolytes are involved in many essential processes such as conducting nervous impulses, contracting muscles, and regulating body’s pH levels and hydration.

Particles that carry a positive or negative electric charge are used in metabolic processes.

• Major electrolytes found in your body include:
  
  • Sodium
  • Potassium
  • Chloride
  • Calcium
  • Magnesium
  • Phosphate

Question 11

Sodium - Potassium Pump

Answer 11

• Requires ATP - Active Trasport
  
  • Transfers sodium (Na+) outside the cells (high concentration)
  • Transfer potassium (K+) the cells (high concentration)
• Causing an electrochemical gradient
  
  • More potassium ions inside cells and more sodium ions outside

Both sodium and potassium require cell sodium-potassium ATPase pump to maintain Na+ as extracellular ion and K+ as intracellular ion.

Question 12

Third Space Fluid Accumulation

Answer 12

• With illness, fluid shifts into body cavities such as pericardial sac, peritoneal cavity, and pleural space.
• These third space accumulation of fluids in body cavities are called effusion (pericardial, peritoneal or pleural effusion).

Question 13

Pitting edema

Answer 13

• Occurs when pressure is applied to small area and an indentation persists for some time after the release of the pressure.
• Depends on severity, may be +1, +2, +3 pitting edema.

Question 14

Syndrome of Inappropriate Antidiuretic Hormone (SIADH)

Answer 14

• Antidiuretic hormone (ADH) is a hormone that is produced by the hypothalamus and released by the pituitary gland to control how the body releases and conserves water.
• SIADH - when ADH (also called vasopressin) is produced in excess
• Makes it harder for your body to release water causing fluid buildup.
• Causes levels of electrolytes, like sodium, to fall as a result of water retention.
  
  • A low sodium level or hyponatremia is a major complication of SIADH
• Early symptoms may be mild and include cramping, nausea, and vomiting. In severe cases, SIADH can cause confusion, seizures, and coma.
• Treatment: The first line of treatment is to limit fluid intake to avoid further buildup. Medications may include those that can reduce fluid retention, such as furosemide (Lasix), and those that can inhibit ADH, like demeclocycline.

Question 15

Oliguria

Answer 15

• Urine output below normal
  
  • < 400 mL/day or 20-30 mL/hour.
• Can offer information on whether the kidneys function normally, in terms of blood filtration and excretion of waste products through urine.
• Total urine output for an adult, during 24h is of 800 to 2000 mL, this is equivalent to around 1 mL/kg/hr. In an adult weighing 60 kg, this means 60 mL/hr
• Assessment of Fluid Status - daily weights and 24-hour intake and output (I/O).

Question 16

Orthostatic hypotension

Answer 16

• Also called postural hypotension — form of low blood pressure that happens when standing after sitting or lying down.
• Causes dizziness or lightheadedness and possibly fainting.
• Usually caused by something obvious, such as dehydration or lengthy bed rest. The condition is easily treated. Chronic orthostatic hypotension is usually a sign of another health problem

Question 17

Managing Fluid Imbalances

Answer 17

Failure to maintain adequate intake or output can lead to fluid imbalance disorders.

• Deficit - dehydration, shock
  
  • Treatment - Administer oral (PO) or IV fluids
• Excess - edema
  
  • Treatment - diuretics

Question 18

Fluid Volume Deficit

Answer 18

May result in shock, dehydration, or electrolyte loss.

• Fluid depletion can be caused by:
  
  • Vomiting, diarrhea, chronic laxative use, GI suctioning
  • Excessive sweating
  • Severe burns
  • Hemorrhage
  • Excessive diuresis due to diuretic therapy or uncontrolled diabetic ketoacidosis
• To treat nonacute fluid depletion - drinking more liquids
• Acute depletion - IV fluid therapy
  
  • Must strive to restore normal levels of blood elements (erythrocytes, leukocytes, thrombocytes), electrolytes, and total fluid volume.
• If significant blood loss blood products may be indicated

Question 19

Crystalloids

Answer 19

• Replace depleted fluids
• IV solutions that closely resemble the composition of ECF
  
  • Contain electrolytes
• Diffuse across membranes
• Isotonic, hypotonic, and hypertonic solutions available
  
  • Sodium is the most common. Dextrose (glucose)
  • Ex. Normal saline, lactated ringers

Question 20

Isotonic crystalloids

Answer 20

Expand the circulating intravascular (plasma) fluid volume without causing fluid shifts

• Often used to treat fluid loss due to vomiting, diarrhea, surgery
• Treats hyponatremia (low sodium) as they contain sodium chroride
• Careful not to cause fluid overload
• Ex. D5W, 0.9% NS, LR (NaCl, KCL, CaCL Na Lactate)

Question 21

Hypertonic crystalloids

Answer 21

• Raise osmolality and expand volume of plasma
• Draw water away from cells (ICF to ECF)
• Increases ECF Volume, Decreases Edema
• Treats cellular edema, especially edema
• May cause fluid overload, hypernatremia (D5NS
• Ex. D5NS, D5LR, 3% NaCl, Dextrose 10%, TPN

Question 22

Dextrose D₅W

Answer 22

• 5% Dextrose in water
• The actual solution in the bag is isotonic
• Once you give D5W to patients the body metabolizes the glucose molecules that were once causing the solution to be isotonic.
• The solution is now missing solute, causing it to become a hypotonic solution.

Question 23

Hypotonic crystalloids

Answer 23

Lowers plasma osmolality

• Hydrates Cells - Shifts fluid from ECF to ICF/ISF
• Indicated in hypernatremia, cellular dehydration
• Careful not to deplete intravascular fluid causing a drop in BP or too much extracellular expansion leading to peripheral edema
• Promotes sodium diuresis, may cause hyponatremia

Patients with low BP and dehydration - NS

Patients with normal BP and dehydration - hypotonic crystalloids

• Ex. D5W, D5 1/2NS, 0.45% NS

Question 24

Plasma Volume Expanders

Answer 24

• Colloids - protein, starches or other large molecules
  
  • Plasma expanders
  • Too large to cross capillary membranes
  • Same effect as hypotonic solutions - ICF - ISF
    
    • Increase plasma osmolality
• Blood product colloids:
  
  • Advantage of natural colloids is that they provide protein, such as albumin; antibodies; critical clotting factors; and other plasma constituents.
    
    • Normal Serum Albumin - Keeps fluid in ECF
    • Plasma Protein Factor (PPF) - replaces clotting factors
    • Serum globulins
• Non-blood product colloids:
  
  • Dextran - Expands Volume, Shifts ICF - ISF into ECF
  • Hetastarch - Synthetic Colloid, Expands volume, Shifts ICF - ISF into ECF
• Administered to provide life-sustaining support following massive hemorrhage, shock, burns, acute liver failure and neonatal hemolytic disease

Question 25

Blood and Blood Products

Answer 25

• Whole Blood -
  
  • all blood components
  • Indications: rapid, massive blood loss
  • When safer agents are unavailable
• Packed RBCs -
  
  • Increases hemoglobin and hematocrit
  • treats acute anemia, monitor carefully
• Fresh frozen plasma (FFP)
  
  • Replace clotting factors
• Cryoprecipitate -
  
  • Concentrate prepared from FFP
  • Originally used from hemophilia
  • Treat bleeding, many clotting factors
• Immune Globulins -
  
  • Antibody preparations
  • boost immune response
• Platelets
  
  • Used to prevent bleeding in thrombocytopenia (low platelet count)

Question 26

Administering Blood Products

Answer 26

• Supply of blood products depends on human donors
• Requires careful cross-matching
• Complications of whole blood transfusion include
  
  • Febrile nonhemolytic and chil-rigor reactions
  • Circulatory Overload, Bacteremia
• Serious adverse effects inclued
  
  • Acute hemolytic transfusion reaction, allergic reactiction
  • anaphylaxis, acute hemolytic reactions

Question 27

Hyponatremia

Answer 27

Low sodium blood levels

• Less than 135 milliequivalents per liter (mEq/L)
• Causes:
  
  • Can occur in low blood volume
  • Diuretics
  • SSRI use
  • Dilutional hyponatremia (water intoxication)
    
    • When a person consumes too much water without an adequate intake of electrolytes
• S/S include :
  
  • HA
  • lethargy
  • apathy
  • Confusion
  • N/V/D - nausea,vomiting, diarrhea
  • muscle cramps and spasms
• Severe hyponatremia (fewer than 125 mEq/L) has a high mortality rate (seizures, coma, death)
• In instances when the serum sodium level is fewer than 105 mEq/L, the mortality is over 50%
• Rx with LR, NS, Fluid Restrictions, correct slowly
  
  • Too-rapid correction of sodium can cause osmotic demyelination syndrome (ODS), a form of brain damage

In patients with severe symptomatic hyponatremia, the rate of sodium correction should be 6 to 12 mEq per L in the first 24 hours and 18 mEq per L or less in 48 hours.

Question 28

Hypernatremia

Answer 28

• Too much sodium in blood
• Greater than 145 mg/dL
• Most common cause:
  
  • Not enough fluid intake or too much loss of fluids, leading to insufficient liquid in the blood
  • Causes cellular dehydration
• Elderly and infants at highest risk
• Early symptoms may include thirst, weakness, nausea, and loss of appetite. Severe symptoms include
  
  • AMS (Acute Mountain Sickenes) - dizziness, headache, muscle aches, nausea
• Overcorrection dangerous, may lead to cerebral edema
• Rx with IVF, increase oral fluid intake
• Hypernatremia with Water Retention - If hypernatremia causes water retention, then the picture is one of an edematous state with weight gain, HTN. If severe, AMS changes and pulmonary edema occur.
• Hypernatremia with Water Loss - If the hypernatremia causes sodium retention and water loss can result in dehydration, thirst, irritability, tachycardia, flushed skin, dry mucous membranes, oliguria

Question 29

Hypernatremia

Answer 29

• Too much sodium in blood
• Greater than 145 mg/dL
• Most common cause:
  
  • Not enough fluid intake or too much loss of fluids, leading to insufficient liquid in the blood
  • Causes cellular dehydration
• Elderly and infants at highest risk
• Early symptoms may include thirst, weakness, nausea, and loss of appetite. Severe symptoms include
  
  • AMS (Acute Mountain Sickenes) - dizziness, headache, muscle aches, nausea
• Overcorrection dangerous, may lead to cerebral edema
• Rx with IVF, increase oral fluid intake
• Hypernatremia with Water Retention - If hypernatremia causes water retention, then the picture is one of an edematous state with weight gain, HTN. If severe, AMS changes and pulmonary edema occur.
• Hypernatremia with Water Loss - If the hypernatremia causes sodium retention and water loss can result in dehydration, thirst, irritability, tachycardia, flushed skin, dry mucous membranes, oliguria

Question 30

Diuretics

Answer 30

• Sometimes called water pills, help rid your body of salt (sodium) and water.
  
  • Most of these medicines help your kidneys release more sodium into your urine.
  • The sodium helps remove water from your blood, decreasing the amount of fluid flowing through your veins and arteries. This reduces blood pressure.
• There are three types of diuretics:

1. Thiazide and Thiazide-Like
2. Loop
3. Potassium sparing

• Each type of diuretic affects a different part of your kidneys. Some pills combine more than one type of diuretic or combine a diuretic with another blood pressure medication.

Question 31

Potassium (K)

Answer 31

Most important electrolyte

• Main electrolyte of the ICF
• Adults require 40-60 mEq/L/day
• Causes:
  
  • Severe diarrhea can result in loss of 40 to 60 mEq/L/day.
  • Excessive alcohol use
  • CKD
  • Diuretics
  • Excessive laxative use
• Fluid shifts between ICF and ECF can alter K+ level
• severe muscle weakness, paralysis, respiratory failure
• When H+ is high in bloodstream, H+ excretion takes precedence over K+ excretion at kidney

Question 32

Hypokalemia

Answer 32

• Low blood potassium
• Potassium below 3.5 mEq/L
• Diuretic therapy is the most common cause of hypokalemia (loop and thiazide diuretics)
• Signs and Symptoms
  
  • Anorexia, N/V
    
    • Sluggish bowel
    • Cardiac arrhythmias
    • Postural hypotension
    • Muscle fatigue, Weakness, Leg cramps
    • Decreased deep tension reflexes ( DTRs)
• Hypokalemia on ECG - Prolonged PR interval, flattened T wave, prominent U wave.
• Potassium levels below 3.0 mmol/l cause significant Q-T interval prolongation with subsequent risk of torsade des pointes, ventricular fibrillation and sudden cardiac death.

Question 33

Hypokalemia and HF (Heart Failure)

Answer 33

• Monitor K+ and Digitalis Levels in HF
  
  • Digitalis - increases intracellular sodium levels
• Diuretics and digitalis often prescribed together in HF. Diuretics commonly cause hypokalemia.
• Hypokalemia Increases Digitalis toxicity - potentiates action of Digoxin.
• Hypokalemia causes increased binding of digitalis in the heart, which increases susceptibility of digitalis toxicity.
• This may result in cardiac dysrhythmias.

Question 34

Treatment Hypokalemia

Answer 34

• Rapid administration of K+ can cause cardiac arrest
• IV potassium must always be diluted
• NEVER give as an IV bolus
• Excoriating to skin and blood vessels in large doses
• Administer 20-40mEq in 1 liter of IV fluid
• Potassium Rich foods - OJ, Bananas, Meat

Question 35

Hyperkalemia

Answer 35

• High blood potassium
• Blood K+ level greater than 5.2 mEq/dL
• Symptoms of Hyperkalemia
  
  • Numbness or tingling of the extremities
  • Muscle cramping
  • Diarrhea
  • Apathy
  • Mental confusion
  • Dysrhythmias similar to hypokalemia
• In Hyperkalemia, ECG will show wide QRS complexes; tall, peaked T waves; and, ultimately, cardiac arrest

Question 36

Treatment Hyperkalemia

Answer 36

• For severe hyperkalemia (greater than 7.0 mEq/L), rapid treatment is needed to move K+ from ECF to ICF.
• Caused by excess intake or renal pathology
• Continuous ECG monitoring is necessary
• Rx:
  
  • IV 50% dextrose, 10 units of regular insulin, and 75 mEq of sodium bicarbonate
    Furosemide (Lasix)
  • Calcium chloride or calcium gluconate (Kalcinate)
    
    • They start working in minutes by shifting potassium out of the blood and into cells
• Sodium polystyrene sulfonate (Kayexalate) excretion via feces
• If patient in renal failure, dialysis can reduce K+
  
  • People with very high blood potassium levels may also need dialysis, which uses a special machine to filter the potassium from your blood.

Medications lower potassium slowly, including:

• Water pills (diuretics), which rid the body of extra fluids and remove potassium through urine
• Sodium bicarbonate, which temporarily shifts potassium into body cells
• Albuterol, raises blood insulin levels and shifts potassium into body cells
• Sodium polystyrene sulfonate (Kayexalate), removes potassium through your intestines before it’s absorbed
• Patiromer (Veltassa), which binds to potassium in the intestines
• Sodium zirconium cyclosilicate (Lokelma), which binds to potassium in the intestines

Question 37

Hypocalcemia

Answer 37

• Low blood calcium level
• Blood calcium level lower than 8.7 mg/dL in adults.
• S/S include:
  
  • Paresthesia around mouth, hands, feet
  • Muscle spasms of face - Chvostek’s sign
  • Larnygeal spasm
  • Carpal spasms - Trousseau’s sign, seizures, hypotension, dysrhythmias
  • Chronic hypocalcemia causes bone pain and fragility, dry skin and hair, cataracts, depression, and dementia.
• Rx - Ca++, Vitamin D
  
  • Calcium and phosphorus are major mineral contents of bone.
  • Vitamin D facilitates absorption of calcium from gastrointestinal tract into bloodstream.
• When plasma calcium low, PTH stimulated; when plasma calcium level high, PTH is inhibited.
• Calcitonin, hormone produced by thyroid, acts at bone and kidneys to remove calcium from circulation.
• Calcium-Phosphate Relationship - reciprocal relationship between calcium and phosphate - increase in calcium in blood, leads to decrease in phosphate—and vice versa.
• Trousseau’s sign -
  
  • Involuntary contraction of the muscles in the hand and wrist seen when the upper arm is compressed with a blood pressure cuff (inflated to a pressure greater than the patient’s systolic pressure for 2 to 3 minutes)
• Calcium and Albumin - half calcium in body is bound to albumin.
  Hypoalbuminemia can cause appearance of low calcium levels called pseudohypocalcemia.

Question 38

Hypercalcemia

Answer 38

• High blood calcium level
• Calcium level greater than 10 mg/dL.
• Common causes:
  
  • hyperparathyroidism, cancer
• Signs/Symptoms -
  
  • Muscle flaccidity
  • Lower extremity (LE) muscle weakness
  • bone tenderness
  • Decreased neuromuscular bowel activity - constipation
  • High calcium concentration in urine with HR renal calculi
  • Ventricular arrhythmias
  • Dulled consciousness, Depression
  • Anorexia
  • Nausea
  • Vomiting
  • Ulcers
  • Hyperreflexia
  • Tongue fasciculations
• Rx - increase fluids and loop diuretics, dialysis

Question 39

Phosphorus

Answer 39

• Essential component of bone, red blood cells (RBCs), enzymatic processes, formation of adenosine triphosphate (ATP), acid-base balance, and cellular building blocks.
  
  • Found in bone and circulates in blood as phosphate (Po4-).
• Phosphates incorporated into nucleic acids of DNA and RNA and phospholipids of cell membrane.
• Major anion found in intracellular fluid.
• Phosphorus is essential mineral never found as free element…found in body in combination with oxygen (Po4)

Question 40

Hypophosphatemia

Answer 40

Blood level phosphate < 2.5 mg/dL

• Symptoms include:
  
  • Tremors
  • Paresthesias
  • Hyporeflexia
  • Anorexia
  • Dysphagia
  • Muscle weakness
  • joint stiffness
  • Bone pain and osteomalacia (bone softening)
• Rx - phosphorus replacement

Question 41

Hyperphosphatemia

Answer 41

Low blood phosphatre

• Po4- level > 4.5 mg/dL.
• Most common cause kidney failure.
• Hyperphosphatemia - usually r/t hypocalcemia, many of symptoms are related to low calcium levels.

Rx - phosphate binders

Question 42

Hypomagnesemia

Answer 42

Low blood magnesium

• Fewer than 1.5 mEq/L
  
  • Mg++ stored in bone
• Causes include:
  
  • Prolonged diarrhea
  • Laxative abuse
  • Increased renal excretion of Mg++
  • Sepsis
  • Burns
  • Wounds requiring debridement
• Signs/Symptoms:
  
  • Neuromuscular such as tetany
  • Chvostek’s sign
    
    • Twitching of the facial muscles in response to tapping over the area of the facial nerve
  • Trousseau’s sign
    
    • Carpopedal spasm caused by inflating the blood-pressure cuff to a level above systolic pressure for 3 minutes.
  • Cardiac arrhythmias
  • ECG changes similar to hypokalemia (U wave)
  • More serious manifestations: respiratory muscle paralysis, complete heart block, and coma
• Rx - Mg++ replacement MgOx, Mg++ bolus