Fluid and Electrolyte Summary
Fluid Volume
Sodium
Potassium
Calcium
Magnesium

Oxygen Hemoglobin Dissociation Curve

 

Extracellular Fluid Volume Disturbances

1. What is the imbalance?

ECF Volume Disturbance B Excess (Overhydration)

ECF Volume Disturbance B Deficit (Dehydration)

2. What causes the imbalance?

 

Overloading body with sodium:

  • Excessive administration of IV fluids, especially hypertonic solutions

Altered homeostatic regulation of sodium and water:

  • Chronic renal failure
  • Congestive heart failure
  • Excessive corticosteroid therapy
  • Syndrome of inappropriate secretion of ADH (SIADH

Insufficient intake of water and electrolytes:

  • Impaired thirst mechanism
  • Inability to swallow fluids

Excessive fluid loss through secretions or excretions:

  • Potent diuretic therapy
  • Diabetes insipidus
  • Fluid losses from GI tract
  • Excessive sweating

 

3. What are the signs and symptoms?

 

Acute weight gain

Peripheral edema

Shortness of breath B rales in lungs

Changes in behavior B confusion, lethargy, weakness

Distended neck veins

Full, bounding pulse

Elevated BP

Slow-emptying peripheral veins

Effusions into “third spaces”

Acute weight loss

Decreased skin turgor, Dry mucous membranes, Rough, dry tongue (longitudinal furrows in tongue)

Changes in behavior B agitation, restlessness, weakness

Flat neck veins in supine position

Weak thready pulse

Orthostatic hypotension

Slow-filling peripheral veins

 

4. What is appropriate clinical nursing care?

 

Fluid restriction

Dietary Na+ restriction

Diuretic therapy

Since a fluid volume deficit decreases blood flow to kidneys, treatment must begin promptly to prevent damage to kidneys.

If fluids cannot be ingested, isotonic IV fluids (.9% NaCL and D5W) are given initially.  Electrolytes are added to IV solution if adequate renal function is present (Lactated Ringer=s solution)

Although a fluid volume deficit usually takes days to develop, a severe deficit may occur within hours and may lead to circulatory collapse (hypovolemic shock)



Electrolyte Imbalances

Sodium (Na+)

1. What is the normal?

 

Serum Na 135-145 MEq/L

Serum Na+ reflects the osmolality of the blood

 

2. What is the imbalance?

 

Hypernatremia B  Serum Na+ > 145 mEq/L

Serum osmolality > 295 mOsm/kg

Urine s.g. > 1.015

Hyponatremia B Serum Na+ < 135 mEq/L

 

3. What causes the imbalance?

 

Increased water loss:

  • Diabetes insipidus
  • Renal concentrating disorders
  • Watery diarrhea
  • Profuse diaphoresis without fluid replacement

Decreased water intake or increased Na+ intake:

  • Inability to respond to thirst mechanism
  • Difficulty swallowing fluids
  • Hypertonic tube feedings without adequate water supplements
  • Excessive administration of hypertonic NaCl or NaHCO3
  • Adrenal hyperfunction B Hyperaldosteronism

Increased water gain (dilutional hyponatremia):

  • Excessive administration of sodium-free IV fluids (D5W)
  • Excessive tap water enemas
  • Stimulation of antidiuretic hormone (ADH)
  • Psychogenic polydipsia

Increased loss of Na+:

  • Use of hypotonic irrigating solutions (distilled water)
  • Excessive use of thiazide or loop diuretics
  • Sodium-losing renal disease
  • Replacement of water, but not electrolytes lost in massive burns, diaphoresis, vomiting, diarrhea, NG suction
  • Adrenal insufficiency

 

4. What are the signs and symptoms?

 

Behavioral changes may include:

  • confusion, lethargy
  • stupor, coma

Extreme thirst

Muscle weakness

Dry, sticky mucous membranes

Behavioral changes may include:

  • confusion, lethargy
  • convulsions, coma

Muscle weakness

Nausea and abdominal cramps

Postural hypotension

 

5. What is appropriate clinical nursing care?

 

To prevent hypernatremia:

  • Administer water between hypertonic tube feedings
  • Teach elderly patients to drink fluids regularly, as thirst sensation often decreases with aging
  • Offer fluid frequently to patients at risk

To correct hypernatremia:

  • Monitor replacement of water loss as prescribed
  • Diuretics to remove excess Na+ may also be prescribed
  • Monitor specific gravity of urine

To prevent hyponatremia:

  • Use normal saline instead of distilled water for irrigations
  • Avoid tap water enemas in bowel management
  • Teach patients to replace body fluid losses with fruit juice or bouillon rather than water

To correct hyponatremia:

  • Help patient comply with prescribed fluid restriction
  • Administer hypertonic IV solutions when prescribed, with great caution

Potassium (K+)

1. What is the normal?

 

Serum K+ 3.5 - 5.0 mEq/l

K+ is primarily intracellular (98%)

 

2. What is the imbalance?

 

Hyperkalemia B Serum K+ > 5.0 mEq/L

Hypokalemia B Serum K+ < 3.5 mEq/L

 

3. What causes the imbalance?

 

Increased K+ intake:

  • Rapid IV administration of K+
  • Administration of aged blood
  • Increased oral intake causes hyper­kalemia only if accompanied by decreased K+ excretion
  • Excessive use of salt substitutes (K+ClB)

Decreased renal excretion of K+:

  • Acute and chronic renal failure
  • Decreased production of Aldosterone
  • Adrenal insufficiency (Addison=s disease)
  • Excessive use of K+ conserving diuretics:  Spironolactone (Aldactone) and Amiloride (Moduretic)

Movement of K+ into ECF:

  • Tissue injury (burns, major surgery, or crush injury)
  • Acidosis B decreased pH with excess H+ in ECF (compensation causes K+ to shift from cells to ECF)
  • Insulin deficiency

Decreased K+ intake:

Anorexia nervosa

Gastrointestinal K+ loss:

  • Vomiting, gastric suction
  • Diarrhea, laxative abuse, recent ileostomy

Large sweat loss without K+ replacement

Increased renal excretion of K+:

  • Use of K+ losing diuretics without K+ replacement Ex.:  Furosemide (Lasix), Bumetanide (Bumex), and HCTZ
  • Hyperaldosteronism

Entry of K+ into cells:

  • Alkalosis B increased pH with decreased H+ in ECF (compensation causes K+ to shift from ECF to cells)
  • Hypersecretion of insulin

4. What are the signs and symptoms?

 

  • Mental confusion
  • GI hyperactivity (N&V, abdominal cramping and diarrhea)
  • Cardiotoxicity
  • EKG changes (K+ > 6 mEq/L: 
    • Peaked T waves and prolonged
    • PR interval, wide QRS complex
    • Cardiac arrhythmias B bradycardia and heart block
    • Cardiac arrest

 

  • Muscle weakness/paralysis, flaccid muscles (lack tone)
  • Decreased bowel motility (intestinal ileus, nausea and vomiting)
  • Polyuria
  • EKG changes (serum K+ < 3 mEq/L): 
    • ST segment depression, T wave flattening, prominent U waves
    • Cardiac arrhythmias B PACs or PVCs
    • Respiratory failure B K+ <1.5 mEq/L

5. What is appropriate clinical nursing care?

 

To prevent hyperkalemia:

  • Monitor IV infusions of K+ carefully
  • Evaluate renal function before administering K+ intravenously
  • Avoid use of salt substitutes for patients with renal problems
  • Teach patients, particularly those with renal failure, about foods/fluids which are high in K+

To correct hyperkalemia safely:

  • Give fluids to increase urinary output
  • IV NaHCO3 a base, shifts K+ into cells in exchange for H+.
  • Hypertonic glucose infusion stimulates release of insulin which promotes cellular uptake of K+ (5-15 units regular insulin with 50 ml of D50W or 250-500 ml of D10W).
  • Administer K+ depleting diuretics as ordered.
  • Administer Kayexalate (cation exchange resin), if ordered
  • Withhold drugs (e.g., K+ PCN-G) that contain large amounts of K+
  • Decrease dietary sources of K+

To prevent hypokalemia:

  • Teach patients which foods have high K+ content
  • Teach patients about their diuretics

 

 

To correct hypokalemia:

  • Watch for signs of digitalis toxicity in patients receiving digitalis preparations
  • Administer K+ supplements as ordered
  • Administer IV K+ (KCl) in diluted concentration. (Usual concentration 20-40 mEq/L/1000cc.  Maximum is 80mEq/1000cc.)
  • Never administer potassium solutions by IV push; doing so will very likely cause cardiac arrest

Calcium (Ca++)

1. What is the normal?

 

Serum Ca++ 8.5-11 mg/dL

Serum Ca++ and serum phosphate vary inversely

 

2. What is the imbalance?

 

Hypercalcemia B Serum Ca++ > 11 mg/dL

Hypocalcemia B Serum Ca++ < 8.5 mg/dL

 

3. What causes the imbalance?

 

Ca++ release from bone:

  • Hyperparathyroidism
  • Metastatic carcinoma
  • Multiple myeloma
  • Thyrotoxicosis
  • Prolonged immobilization

Increase GI absorption of Ca++

  • Excessive ingestion of Vitamin D

Decreased intake or decreased GI absorption of Ca++:

  • Vitamin D deficiency
  • Chronic insufficient dietary intake of Ca++
  • Acute pancreatitis
  • Overuse of antacids
  • Malabsorption Syndromes

Decrease in physiologically available Ca++:

  • Hypoparathyroidism
  • Overuse of phosphate-containing laxatives and enemas (Ex.: Fleet Phospho-soda)

Increased urinary excretion of Ca++:

  • Chronic renal failure

 

4. What are the signs and symptoms?

 

Nausea and vomiting

Constipation

Muscle weakness/flaccidity

Depressed deep tendon reflexes

Confusion, lethargy, CNS depression (coma)

Polyuria

Pathological fractures (chronic)

Renal calculi

EKG changes:

Shortened QT interval

Cardiac arrest

Muscle cramps

Confusion, irritability, anxiety

Tetany

Paresthesias of fingers and circumoral region

Neuromuscular irritability:

Positive Chvostek=s sign B muscle spasm at cheek and corner of mouth in response to tap over facial nerve in front of ear.

Positive Trousseau=s sign B carpal spasms after occlusion of blood flow to hand with BP cuff for three minutes.

Hyperactive deep tendon reflexes

Convulsions

EKG changes:  Prolonged QT interval

Cardiac arrest

 

5. What is appropriate clinical nursing care?

 

To prevent hypercalcemia:

  • Increase client mobility
  • Teach patient to avoid massive Vitamin D supplementation

To correct hypercalcemia:

  • Administer loop diuretics (Lasix) as ordered
  • Administer IV normal saline (isotonic) as ordered

To prevent complications while correcting hypercalcemia:

  • Ensure adequate hydration to decrease possibility of renal calculi formation
  • Maintain an acid urine
  • Handle patient gently when transferring or repositioning to prevent pathological fractures

To prevent hypocalcemia:

  • Teach patients careful management of antacids and laxatives
  • Teach patients dietary sources of calcium and vitamin D

To prevent complications of hypocalcemia:

  • Administer oral Ca++ supplements as ordered
  • Keep 10 ml of 10% IV calcium gluconate available for emergency use after thyroid surgery. Administer slowly, not exceeding 2 ml/min.

Magnesium (Mg++)

 

1. What is the normal?

 

Serum Mg++ 1.5-2.5 mEq/L

Mg++ is absorbed primarily through the small intestine

 

2. What is the imbalance?

 

Hypermagnesemia B Serum Mg++ >2.5 mEq/L

Hypomagnesemia B Serum Mg++ < 1.5 mEq/L

 

3. What causes the imbalance?

 

Excessive intake or absorption of Mg++:

Overuse of antacids containing Mg++ (Maalox, Gelusil, Riopan)

Overuse of laxatives containing Mg++ (Milk of Magnesia)

Impaired Mg++ excretion:

Advanced renal failure

Adrenal insufficiency (Addison=s disease)

Decreased Mg++ intake or absorption:

Chronic diarrhea

Chronic malnutrition

Malabsorption syndrome B Steatorrhea

Small bowel resection

Chronic alcoholism

Prolonged IV administration without Mg++ supplementation

Gastrointestinal Mg++ loss:

Prolonged diarrhea or nasogastric suction

Intestinal fistulas

Increased urinary excretion of Mg++:

Prolonged excessive diuretic therapy

 

4. What are the signs and symptoms?

 

Hypoactive deep tendon reflexes

Drowsiness, lethargy

Mild hypotension

Nausea and vomiting

Respiratory depression (serum Mg++ > 15 mEq/L)

Cardiac arrhythmias (bradycardia, heart block)

Cardiac arrest (serum Mg++ > 25 mEq/L)

Hyperactive deep tendon reflexes

Coarse tremors

Tetany

Positive Chvostek=s and Trousseau=s sign

Intense confusion

Cardiac arrhythmias (PVC, SVT)

Convulsions

Coma

 

5. What is appropriate clinical nursing care?

 

To prevent hypermagnesemia:

Teach patients careful management of Mg++ containing antacids and laxatives

Teach patients with renal problems to avoid preparations containing Mg++

To prevent complications and correct hypermagnesemia safely:

Give fluids to increase urinary output - patients with impaired renal function will require dialysis

Withhold preparations containing large amounts of Mg++

Keep 10% calcium gluconate, a magnesium antagonist, available for emergency use

To prevent hypomagnesemia:

Provide diet counseling for patients at risk

To correct hypomagnesemia safely:

Administer IM or IV MgSO4 as ordered (20 gms/2ml)

Evaluate renal function before administering Mg++ replacement


Oxyhemoglobin Dissociation Curve

The oxyhemoglobin dissociation curve explains why a PaO2 of greater than 70 mm Hg at rest still allows for an acceptable hemoglobin saturation. Anything less than 70 is not compatible with life. These values are to be used when the patient=s temperature and acid/base balance are near normal.

On this graph identify the PaO2 for a pulse oximetry reading of

95%

85 %

70%

What action would you take for each of these readings?