Fluid, Electrolyte and Acid/Base Balance
 Scientific Knowledge Base: Distribution of Body Fluids
 Intracellular Fluids (ICF)
 Fluids within cells
 42% of total body weight
 Two thirds of total body water
 28 liters in males
 20 liters in females
 Extracellular Fluid (ECF)
 Fluid outside of cells
 Interstitial, intravascular, and transcellular
 Makes up 17% of total body weight
 Composition of Body Fluids
 Electrolyte:
 An element or compound that, when dissolved or dissociated in water or solvent, separates into ions
 Ions:
 Cations: positively charged
 Anions: negatively charged
 Movement of Body Fluids
 Osmosis:
 Movement of a solute from an area of lesser
to one of greater concentration
 Osmolality
 Osmolarity
 Hypertonic
 Isotonic
 Hypotonic
 Diffusion:
 Random movement of a solute through a
semipermeable membrane from higher to
lower concentration
 Filtration:
 Movement across a membrane, under
pressure, from higher to lower pressure
 Active transport:
 Movement of ions against osmotic pressure
to an area of higher pressure
 Fluid Intake
 Regulated by thirst
 Osmoreceptors monitor serum oncotic pressure; when osmolality increases, the hypothalamus stimulates
thirst
 Ex: eating salty chips increases oncotic pressure and stimulates thirst via the hypothalamus
 Ex: If excess fluid lost in excessive vomitting, diarrhea, or hemorrhage, hypovolemia occurs and the
hypothalamus stimulates thirst
 Average adult intake = 2500 ml (in food and drink)
 Thirst requires alert state; infants, elderly and those with neuro problems are at risk for dehydration
 Hormonal Regulation
 When blood osmolarity increases (increased concentration of salt or decreased fluids):
 Antidiuretic hormone (ADH) is released which works on kidneys to “save water”. Water is returned to
systemic circulation, diluting the blood and decreasing osmolarity. Urine output decreases.
 Renin responds to less blood reaching the kidney; produces angiotensin I which converts to angiotensin
II which causes vasoconstriction and thus increases blood flow to the kidneys (and stimulates release of
aldosterone)
 Aldosterone is released which acts on kidneys to “save salt” and “secrete potassium”. Sodium retention
then leads to water retention.
 Fluid Output Regulation
 Fluid output occurs via: kidneys, skin, lungs and GI tract
 Kidneys produce 1200-1500 ml urine/day
 The body loses about 500ml of fluid through the skin daily
 Sensible loss= perspiration; insensible loss is continuous and nonperceptual
 The lungs expire about 400-500ml/water daily (insensible loss)
 GI tract account for only 100-200 ml/fluid loss per day, but can become a major site of fluid loss
because 3-6 Liters of fluid is reabsorbed daily
 Therefore total fluid gains: 2200-2700 ml/day and total losses are 2200-2700 ml/day
 Major Electrolytes
 Cations:
 Sodium (Na+)
 Potassium (K+)
 Calcium (Ca2+)
 Magnesium (Mg2+)
 Anions:
 Chloride (Cl-)
 Bicarbonate (HCO3–)
 Phosphate (PO43-)
 Acid-Base Balance
 pH is a measure of acidity (lower the pH, the higher the acidity); normally 7.35-7.45
 Acidotic
normal blood pH
alkalotic
 <7.35
7.35 – 7.45
>7.45
 pH is a balance between an acid, carbon dioxide (CO2) which the lungs regulate, and a base, bicarbonate
(HCO3), which the kidneys regulate
 Regulation of Acid-Base Balance
 Chemical:
 Carbonic acid and
bicarbonate buffer system
 Biological:
 Occurs when hydrogen ions
are absorbed or released by
cells
 Physiological:
 Buffers are located in lungs
and kidneys
 Disturbances in Fluid, Electrolyte, and Acid-Base Balances
 Fluid:
 Isotonic
 FV Deficit
 FV Excess
 Osmolar
 Dehydration
 Water excess
 Electrolyte:
 Hyponatremia
 Hypernatremia
 Hypocalcemia
 Hypercalcemia
 Hypomagnesemia
 Hypermagnesemia
 Hypochloremia
 Hyperchloremia
 Acid-Base:
 Respiratory acidosis
 Respiratory alkalosis
 Metabolic acidosis
 Metabolic alkalosis
 Disturbances in Fluids
 Fluid Volume Deficit (FVD)
 Body loses BOTH water and electrolytes from ECF in similar proportions (isotonic so serum sodium
remains normal)
 = HYPOVOLEMIA (since initially lost from intravascular compartment)
 Causes: bleeding, vomitting, diarrhea, fever, use of diuretics, excessive perspiration, decreased oral
intake
 Symptoms: Decreased BP, tachycardia and weak pulse, dry mucous membranes, poor skin turgor,
decreased urine output, confusion
 Labs: increased: urine specific gravity, HCT, BUN
 Treatment: IV Therapy (isotonic fluids)
 Fluid Volume Excess (FVE)
 Body retains both water and sodium in similar proportions in ECF (so serum sodium remains normal)
 = HYPERVOLEMIA
 Causes:
 Excessive intake of sodium in diet or meds
 Too rapid sodium-containing IVs
 Diseases that alter regulatory mech: CHF, RF, cirrhosis of liver
 Symptoms:
 Weight gain (>2lbs/24hrs), edema, increased BP, crackles in lungs, dyspnea, bounding pulses, distended
jugular vein
 Labs: decreased HCT and BUN (hemodilution)
 Treatment: fluid and sodium restriction, diuretics
 Osmolar Imbalances
 Dehydration
 Loss of Water
 Causes: Diabetes, Administration of hypertonic fluids, loss of thrist drive
 Symptoms: Dry mucous membranes and skin, thirst, irritability, coma
 Labs: increased sodium and serum osmolality
 Water Excess
 Excess of Water
 Causes: Excess water intake
 Symptoms: decreased LOC, coma
 Labs: decreased sodium and decreased serum osmolality
 Disturbances in Electrolytes
 Sodium, Potassium, and Calcium
 Sodium (Na+): 135-145 mEq/L
 Major influence on maintaining water balance; located in ECF
 Hyponatremia: lower than normal sodium concentration
 Hypernatremia: higher than normal sodium concentration; usually due to excess water loss; common
symptom dry sticky mucous membranes
 Potassium (K+): 3.5-5 mEq/L
 Predominant electrolyte in ICF
 Body does not conserve it well, so an increase in fluid output results in hypokalemia. (Therefore
potassium supplementation is important with diuretics)
 Hyperkalemia can occur in kidney failure or with potassium sparing diuretics
 Any potassium imbalance can result in cardiac abnormalities
 Calcium (Ca2+): 4.5 – 5.5mg/dl
 Hypocalcemia: low calcium; may cause cramping, numbness, tingling
 Hypercalcemia: high calcium; may cause N/V, weakness, low LOC, cardiac arrest
 Magnesium and Chloride
 Magnesium (Mg 2++) 1.5 – 2.5 mEq/L
 Hypomagnesium: occurs with malnutrtion and/or malabsorption
 Hypermagnesium: decreases muscle and nerve function
 Chloride (Cl-) 95-105 mEq/L
 Hypochloremia: occurs with sodium loss or loss of HCL acid
 Hyperchloremia: occurs with decrease in bicarbonate or increase in sodium
 Both common with acid base imbalance
 Disturbances in Acid Base
 Arterial Blood Gases
 Arterial Blood Gases (ABGs) is best way to evaluate acid-base balance
 Major components:
 pH (7.35-7.45): acidotic if less and alklotic if more (see diagram at end of PPT)
 PaCO2 (35-45): pressure of carbon dioxide (an acid)
 If hyperventilating (thus “blowing off CO2): less than 35 (respiratory alkalosis)
 If hypoventilating (thus retaining CO2): greater than 45 (respiratory acidosis)
 PaO2: (80-100): oxygen pressure in blood
 SaO2: (95-100%): oxygen saturation
 HCO3: (22-26): bicarbonate (a base); kidneys excrete or produce it to maintain a normal balance
 Metabolic acidosis: less than 22
 Metabolic alkalosis: greater than 26
 ROME
 You can also remember the acronym ROME.
 R=Respiratory O=Opposite (meaning that if your PACO2 and pH are of opposite values, you have a
resp problem) M=Metabolic E=Equal (meaning that if your values are equal, both inc or both dec, then
you have metabolic prob).
 Ex. Respiratory Acidosis pH
PACO2
HCO3 Ex. Metabolic Alkalosis pH
PACO2
HCO3 Types of Acid-Base Imbalances
 Respiratory acidosis: increased acid level resulting in decreased pH due to excess CO2 retained
 Ex: patient with COPD retaining CO2
 Respiratory alkalosis: decrease in acid level resulting in increased pH due to CO2 being “blown off”
 Ex: patient anxious and hyperventilating
 Metabolic acidosis: increased acid level resulting in decreased pH due to loss of HCO3 (Ex: starvation,
excessive exercise, DKA, renal failure)
 Metabolic alkalosis: decreased acid level resulting in increased pH and increased HCO3 (common
cause: vomitting and NG suctioning)
 The Nursing Process
 Focused Nursing Assessments
 History: consider who is at risk for imbalance
 Age (infants, elderly); chronic disease (CHF, RF); recent surgery, trauma or burns; temp extremes; diet
history; vigorous exercise; meds (espec. Diuretics)
 Daily weights (>2lbs/24hrs significant)
 Vital signs (espec. BP, pulses)
 24 hour Intake and Output
 Input: measure ice chips, foods that become liquid @ room temp, IV meds, tube feedings
 Output: include urinary output, vomitus, liquid feces, tube drainage, wound drainage; consider
insensible losses with diaphoresis and hyperventilation
 Labs: urine specific gravity, HCT, BUN, electrolytes, ABGs
 Other focused assessments
 Urine amount and appearance
 Skin turgor or edema
 Mucous membranes
 Lung sounds
 Mental status, confusion
 Common Nursing Diagnoses
 Excess fluid volume
 Deficient fluid volume
 Risk for imbalanced fluid volume
 Therapeutic Nursing Interventions
 Facilitate fluid intake when needed (FVD)
 ID fluids the client likes; avoid caffeine because of diuretic effect; help select foods that are liquid @
room temp
 Teach family members to offer fluids regularly to clients who cannot meet their own needs
 Help restrict intake when needed (FVE)
 Educate that ice chips, gelatin, ice cream are considered fluids;
 Allow half total volume on day shift
 Place fluids in small containers so looks “full”
 Offer ice chips instead of water
 Avoid salty or sweet foods because cause thirst
 Require frequent mouth care
 Restrict dietary sodium if ordered
 Provide IV fluids as ordered
 Isotonic fluids commonly used for FVD (Ex: D5W, 0.9NS)
 Potential problems with IV therapy
 Infiltration (fluid escapes into subq tissue)
 Signs: swelling, pallor, coldness, pain at site, decrease in flow rate
 Tx: Discontinue IV and restart at different site
 Phlebitis (inflammation of vein)
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 Signs: localized tenderness, redness, warmth and mild edema of vein above insertion site
 Tx: Discontinue IV and restart at different site. Apply warm moist compresses
Infection
 Signs: fever, chills, malaise, pain, swelling, inflammation or pus at IV site
 Tx: Discontinue IV, notify MD
 Prevention: Maintain sterile technique; change tubing q24hrs if agency policy permits
Speed shock (infusing IV too rapidly)
 Signs: pounding headache, rapid pulse, chills, back pain, dyspnea
 Tx: Discontinue IV, notify MD, monitor VS
Fluid Overload (too large of volume infused)
 Signs: dyspnea, engorged neck veins, increased BP
 Tx: slow infusion rate, notify MD, monitor VS
Embolus (thrombus or air enters vein)
 Signs: depends on location of infarction (e.g., cerebral, pulmonary): dyspnea, sudden pain
 Tx: Report any sudden pain or dyspnea immediately
 Evaluation
 It is possible for patient’s condition to change rapidly, so monitor closely
 In acute alterations monitor:
 Mucus membranes, skin turgor, BP, I/O trend, daily lab results
 In chronic situations, monitor patient’s ability to follow diet and fluid restrictions and med schedules
 Routinely review if you have met patient’s expectations for care: “Tell me if I have helped you feel
more comfortable.”