Class 16 (Chp. 16) – Fluids, Electrolytes, & Acid-Base Balance
Assessment
 Factors affecting fluid, electrolyte, & acid-base balance
o Age
 Infants & elderly more
susceptible to fluid imbalances
 Infants have a higher metabolic
rate – creates more toxins, can’t
concentrate urine, water lost to
evaporation r/t high body
surface area








Elderly more prone to
hypokalemia r/t wasting
potassium with diuretics
Elderly generally don’t drink
enough water
Subcutaneous tissue loss in
elderly leads to increased
moisture loss
Gender
 Hormonal fluctuations in
 Men have a greater total body
women
water percentage
o Stress – increased fluid retention from aldosterone production, decreased renal excretion
o Weight – total body fluid disproportionate weight in people that are obese
o Surgery – pre-op NPO, blood loss, stress, fluid drainage, post-op vomiting
o Medical conditions – cardiac, hepatic, renal & respiratory
Vital signs
o Pay close attention to prolonged fever, tachycardia, changes in respirations, & alterations in BP
o Monitor q4
Weight
o I&O record isn’t always an accurate reflection of changes in fluid balance
o Daily weights are the more precise method
 Same gown/clothing, same scale, same time of day, before breakfast, after voiding
o A change of 1kg (2.2lb) = 1L (1000mL) of fluid
Skin turgor & mucous membranes
o Skin turgor can provide an indicator of fluid volume imbalance
o Deficit
 Skin remains pulled upright
 Furrows in the tongue (severe
(tented) after release
deficit)
 Mucous membranes are dry &
 Common to see dry, cracked lips
sticky
Neurologic assessment
o Deep tendon reflexes
o Confusion, agitation, coma
o Tremors
Cardiovascular assessment
o Irregular heart rate
o Blood pressure
o Palpitations
o Peripheral pulses
o Grading of pulses
o Presence of edema
 Significant & visible sign of fluid volume excess
 Usually found in dependent areas of the body
 Late indicator of fluid volume excess
 Pitting edema – characterized by a lasting indentation in the skin when pressure is applied
 Brawny edema – obvious swelling; tissue is too firm & hard to be indented
Respiratory assessment
o Abnormal lung sounds (crackles)
o Respiratory rate
o Diminished lung sounds
Musculoskeletal assessment
o Muscle strength
o


Class 16 (Chp. 16) – Fluids, Electrolytes, & Acid-Base Balance
 GI & GU assessment
o Intake (PO, IV fluids)
o Frequency & characteristics of stool –
constipation or diarrhea
o
o
Nausea & vomiting
Amount of urine output
Nursing Interventions
 Monitoring fluid balance
o The nurse should evaluate the impact of disease or effect of treatment on an ongoing basis
 Fluid replacement – pt may need to increase fluid intake to offset losses
 Electrolyte replacement
o 2 most commonly prescribed supplements are K+ and Ca+
 Intake & Output (I&Os)
o Oral intake includes all fluids & foods that become liquid at room temperature
 Ice chips, ice cream, popsicles/water ice, soup, jello
o Output consists of any body fluid that can be measured
o Nurse notes whether I&Os balance in a 24 hour period
 Nurse is responsible for confirming that ordered tests have been completed & results are communicated to the
HCP
o Labs often ordered to monitor fluid, electrolytes, & acid-base balance; also to assess effectiveness of
prescribed meds
 Restricting electrolyte intake
o Sodium restrictions are classified as mild, moderate, or severe
o Na+ restrictions
 Mild – 3000-4000 mg/day
 “no added salt”
 Moderate – 2000 mg/day
 “low sodium”
 Severe – 500 mg/day
o Instruct pt on the dietary restrictions & common foods to avoid
 Maintaining fluid & electrolyte balance
o Restricting fluid intake – use 50% of the
o Amount of fluid is divided further into
fluid amount during the day when the
fluid with meals, between meals, & with
pt is most active & consumes two meals
med admin
 Restricting electrolyte intake
 Education
o Buy fresh or frozen, not canned
o Salt substitutes & herbs are okay
o No cured meats allowed
o Some OTC meds have high sodium
contents
Mechanisms
 Body fluid is either intracellular (ICF) or extracellular (ECF)
o Majority of fluid is ICF – within the cell
o Extracellular fluid – fluid outside of the cell
 Interstitial, intravascular, or transcellular
 Extracellular fluid imbalances
o Correct the underlying cause & replace water & electrolytes – orally, with blood products, or through
balanced IV solutions
 Osmotic pressure
Class 16 (Chp. 16) – Fluids, Electrolytes, & Acid-Base Balance
o Amount of pressure required to stop
o Determined by the concentration of
osmotic flow of water
solutes in solution
 Hypovolemia & BP decrease stimulate the release of renin by the kidneys
o Converts angiotensinogen to
o Angiotensin II – vasoconstriction
angiotensin I
through body to increase BP,
o ACE (angiotensin converting enzyme)
reabsorption of water, stimulate adrenal
cortex to produce aldosterone, secrete
form the lungs kidneys changes
angiotensin I to angiotensin II
ADH, stimulates thirst mechanism
 Homeostasis – maintenance of fluid balance
o Monitored by the kidneys through
balance through vasoconstriction &
excretion or reabsorption of Na+
changes in blood pressure
o
ADH
(released by the pituitary gland) –
o Renin-angiotensin-aldosterone
maintain serum osmolality by
mechanism
o Controlled by several mechanisms:
controlling the amount of water
secreted in the urine
renin-angiotensin regulates BP & fluid
ECF & ICF
 ICF
o




Prevalent cation is K+
o
Prevalent anion is PO43-
ECF
o Prevalent cation is Na+
o Prevalent anion is ClHypovolemia (ECF volume deficit) – abnormal loss of normal body fluids, inadequate intake, or plasma to
interstitial fluid shift
o Clinical manifestations r/t loss of vascular volume as well as CNS effects
o Treatment: replace water & electrolytes with balanced IV solution
o Use of hypotonic IV fluids
o Diagnoses used
 Deficient fluid imbalance
 Acute confusion
 Electrolyte imbalance
 Imbalanced nutrition: less than
 Decreased cardiac output
body requirements
o Hypovolemic shock is a potential complication
o Nursing diagnoses – deficient fluid imbalance, electrolyte imbalance, decreased cardiac output, acute
confusion, imbalanced nutrition
Dehydration – loss of water without corresponding loss of sodium
o Assessment
 Chvostek’s sign, Trousseau’s sign, deep tendon reflexes, tremors, confusion, agitation, coma,
jugular vein distension, ECG waveforms, pulses, BP, crackles, diminished lung sounds, respiratory
rate, frequency & characteristics of stool, N/V, amt of urine output
Hypervolemia (ECF volume excess)
o Excess intake of fluids, abnormal retention of fluids, or interstitial to plasma fluid shift
o Clinical manifestations r/t excess volume
 Weight gain is the most common
o Edema (see assessment)
o Care
 Remove fluid without changing electrolyte composition or osmolality of ECF
 Diuretics, fluid restriction, restriction of sodium intake, removal of fluid to treat ascites
or pleural effusion
o Nursing diagnoses – excess fluid volume, electrolyte imbalance, impaired gas exchange, impaired tissue
integrity, activity intolerance
Document continues below
Class 16 (Chp. 16) – Fluids, Electrolytes, & Acid-Base Balance
Fluid Tonicity
 Isotonic, hypotonic, hypertonic
 Effects of water on RBCs
Hypotonic – water excess; solutes less
o Hypertonic – water deficit; solutes more
concentrated than in cells
concentrated than in cells
 Results in cellular swelling
 Results in cellular shrinking
o Isotonic – normal water level
Regulation of water balance
o Renal regulation
 Primary organs for regulating fluid & electrolyte balance
 Adjusting urine volume
 Selective reabsorption of water & electrolytes
 Renal tubules are site of action of ADH & aldosterone
Hydrostatic pressure
o Force of fluid in a compartment
o BP generated by heart’s contraction
Oncotic pressure
o Colloid osmotic pressure
o Osmotic pressure caused by plasma
proteins
Fluid movement in capillaries – amount & direction of movement determined by
o





o Capillary hydrostatic pressure
o Plasma oncotic pressure
Fluid spacing
o First spacing – normal distribution
o Second spacing – abnormal
accumulation of interstitial fluid
(edema)
o
o
Interstitial hydrostatic pressure
Interstitial oncotic pressure
o
Third spacing – fluid is trapped where
it’s difficult or impossible for it to move
back into cells or blood vessels
Class 16 (Chp. 16) – Fluids, Electrolytes, & Acid-Base Balance
Regulation of Water Balance
 Hypothalamic-pituitary regulation
o Osmoreceptors in hypothalamus sense
fluid deficit or increase
o Deficit stimulates thirst & ADH release
 Renal regulation
o Primary organs for regulating fluid & electrolyte balance
o Adjusting urine volume
 Selective reabsorption of water
& electrolytes
 Adrenal corticol regulation
o Releases hormones to regulate water &
electrolytes
 Cardiac regulation
o Natriuretic peptides are antagonists to
the RAAS
o Hormones made by cardiomyocytes in
response to increased atrial pressure
 GI regulation
o Oral intake accounts for most water
o Small amounts of water are eliminated
by the GI tract in feces
IV Fluids & Electrolyte Replacement
 Purpose
o Maintenance – when oral intake isn’t
adequate
o Assess ability to obtain adequate fluid
independently, express thirst & swallow
efficiently
 Parenteral fluid & electrolyte replacements
o Blood transfusions (regarding volume)
o Central venous access devices (CVAD)
o Permit frequent, continuous, rapid, or
intermittent admin of fluids & meds
 Types of fluids categorized by tonicity

Hypotonic – lower osmolality than plasma
o Dilutes ECF
o
Decreased plasma osmolality (water
excess) suppressed ADH release

Renal tubules are sites of action
of ADH & aldosterone
o
o
Glucorticoids (cortisol)
Mineralcorticoids (aldosterone)
o
They suppress secretion of aldosterone,
renin, & ADH to decrease blood volume
and pressure
o
Diarrhea & vomiting can lead to
significant fluid & electrolyte loss
o
o
Assist those with physical limitations
Replacement – when losses have
occurred
o
Allow for giving drugs that are
potentially vesicants
Used to admin blood/blood products &
parenteral nutrition
o
Class 16 (Chp. 16) – Fluids, Electrolytes, & Acid-Base Balance
o Water moves from ECF to ICF by
osmosis
 Isotonic – osmolality similar to plasma
o Similar osmolality to ECF (only expands
ECF); no net loss or gain from ICF
 Hypertonic – higher osmolality when compared to plasma
o Draws water out of cells into ECF
o Requires frequent monitoring of BP,
lung sounds, & serum Na+ levels
 D5W (5% dextrose in water) – isotonic
o Dextrose metabolizes quickly, net result
of free water
o Provides 170kcal/L
 D5 ½ NS (5.5% dextrose in normal saline) – hypertonic
o Common maintenance fluid
o Replaces fluid loss
 D10W (10% dextrose in water) – hypertonic
o Provides 340 kcal/L
o Provides free water but no electrolytes
 NS (normal saline) – isotonic
o 0.9% saline, slightly more NaCl than ECF
o Used when both fluid & sodium is lost
 Lactated Ringer’s – isotonic
o Contains Na+, K+, Cl-, Ca2+, & lactate
o Expands ECF – treats burns & GI losses
 Colloids – stay in vascular space & increase oncotic pressure
o Human plasma products [albumin, FFP
(fresh frozen plasma), blood]
o
o
Usually maintenance fluids
Monitor for changes in mentation
o
o
Ideal to replace ECF volume deficit
Fluids: D5W, NS, LR
o
Fluids: D5 ½ NS
o
Used to replace water loss, prevents
ketosis
o
KCl added for maintenance or
replacement
o
Limits dextrose concentration that may
be infused peripherally
o
Only solution used with blood
o
Contraindicated with liver dysfunction,
hyperkalemia, & severe hypovolemia
o
Semisynthetics (dextran, starches,
Hespan)
Sodium (Na)
 Responsible for
o ECF volume & concentration
o
o Generating & transmitting nerve
o
impulses
 Imbalances typically associated with parallel changes in osmolality
Hypernatremia
Causes
Inadequate water intake, excessive
water loss, sodium gain
S/S
Thirst, AMS (drowsiness, restlessness,
confusion, lethargy), S/S fluid volume
deficit
Interventions
Seizures & coma possible
- treat the underlying cause
- replace fluids orally or via IV with
isotonic fluids or hypotonic fluids
(water deficit)
- dilute with Na-free IV fluids & give
diuretics (excess sodium)
- monitor carefully
Muscle contractility
Regulating acid-base balance
Hyponatremia
Loss of sodium-containing fluids,
water excess
Headache, irritability, difficulty
concentrating
Severe – confusion, vomiting,
seizures, coma
- fluid restriction may be only
treatment (water excess)
- loop diuretics & demeclocycline
- small amounts of IV hypertonic
saline solution 3% NaCl (for seizures)
- fluid replacement with isotonic
sodium-containing solution
Class 16 (Chp. 16) – Fluids, Electrolytes, & Acid-Base Balance
-encourage oral intake (abnormal
fluid loss)
Potassium (K)
 Responsible for
o Resting membrane potential of nerve &
o Maintenance of cardiac rhythms
muscle cells
o Acid-base balance
o Cellular growth
 Dietary sources
o Protein-rich foods
o Salt substitutes
o Fruits & vegetables
o Potassium meds (PO or IV)
 Regulated by the kidneys
 Hypokalemia can enhance the effect of digitalis & lead to digitalis toxicity & subsequent cardiac arrest
 Always dilute IV KCl (potassium chloride)
 Never give KCl via IV push or as a bolus
 Major ICF cation
Hyperkalemia
Hypokalemia
Increase of K+ via the kidneys or GI
Causes
Impaired renal excretion, shift from
ICF to ECF, massive intake of K+, some tract, increased shift of K+ from ECF to
ICF, dietary K+ deficiency, renal losses
drugs, renal failure
from diuresis
Cardiac issues, skeletal muscle
S/S
Dysrhythmias, fatigue, confusion,
tetany, muscle cramps, weak or
weakness, weakness of respiratory
paralyzed skeletal muscles, ABD
muscles, decreased GI motility,
cramps
hyperglycemia
Interventions
- stop K+ intake
- KCl supplements PO or IV
- should not exceed 10 mEq/hr
- increase K+ excretion – diuretics,
dialysis, Veltessa, Kayexalate
- use an infusion pump
- force K+ from ECF to ICF by IV insulin
with dextrose (severe hyperkalemia)
Calcium (Ca)
 Responsible for
o Formation of teeth & bones
o Blood clotting
o Transmission of nerve imoulses
 Obtained from dietary intake; need vitamin D to absorb
 Present in bones & plasma
o Ionized Ca2+ is biologically active
 Changes in pH & serum albumin affects Ca2+ levels
 Balance controlled by
o Parathyroid hormone (PTH) – increases
bone resorption, GI absorption, 7 renal
tubule reabsorption of Ca2+
o
o
Myocardial contractions
Muscle contractions
o
Calcitonin – increases Ca2+ deposition
into bone, increases renal Ca2+
excretion, & decreases GI absorption
Class 16 (Chp. 16) – Fluids, Electrolytes, & Acid-Base Balance
Chvostek’s sign – contraction of face muscles

after light tap over the facial nerve in front of
the ear
Hypercalcemia
Causes
Hyperparathyroidism, cancer

S/S
Interventions
Trousseau’s sign – carpal spasm induced by
inflating a BP cuff above the systolic pressure for
a few minutes
Hypocalcemia
Decreased production of PTH,
multiple blood trnasfusions, alkalosis,
increased Ca2+ loss
Fatigue, lethargy, weakness,
Positive Trousseau’s or Chvostek’s
confusion, hallucinations, seizures,
sign, laryngeal stridor, dysphagia,
coma, dysrhythmias, bone pain,
numbness & tingling around the
fractures, nephrolithiasis, polyuria,
mouth or in the extremities,
dehydration
dysrhythmias
- low Ca2+ diet
- treat the cause
- Ca2+ & vitamin D supplements
- increased weight-bearing activity
- increase fluid intake
- IV Ca2+ gluconate
- rebreathe into paper bag
- hydration with isotonic saline
infusion
- treat pain & anxiety to prevent
- calcitonin
hyperventilation-induced alkalosis
Phosphate (P)
 Responsible for
o
o Function of muscle
o RBCs
 Primary anion in ICF
 Involved in acid-base balance buffering system,
ATP production, cellular uptake of glucose, &
metabolism of macros (carbs, proteins, fats)
Causes
S/S
Interventions
o
Nervous system
Serum levels controlled by parathyroid hormone
(PTH)
 Maintenance requires adequate renal
functioning
 Reciprocal relationship with Ca2+
Hyperphosphatemia
Hypophosphatemia
Malnourishment/malabsorption,
AKI, chronic kidney disease, excess
intake of phosphate or vitamin D,
diarrhea, use of phosphate-binding
hypoparathydroidism
agents, inadequate replacement
during parenteral nutrition
Tetany, muscle cramps, paresthesia,
CNS depression, muscle weakness &
hypotension, dysrhythmias, seizures
pain, respiratory failure, HF, rickets,
(hypocalcemia)
osteomalacia
- ID & treat underlying cause
- oral supplements

Class 16 (Chp. 16) – Fluids, Electrolytes, & Acid-Base Balance
- restrict food/fluids containing
phosphorus
- hemodialysis
- volume expansion & forced diuresis
- correct any hypocalcemia
- ingestion of high phosphorus foods
IV admin Na+ or K+ phosphate
Magnesium (Mg)

 Cofactor in enzyme for metabolism of carbs
 Required for DNA & protein synthesis
 Responsible for
o Blood glucose control
o Needed for ATP production
o BP regulation
 Acts directly on myoneural junction
 50-60% contained in bone
 Important for normal cardiac function
 Absorbed in GI tract, excreted by kidneys
Hypermagnesia
Hypomagnesia
Prolonged fasting, chronic
Causes
Increased intake of products
containing Mg, renal insufficiency,
alcoholism, fluid loss from GI tract,
excess IV Mg admin
prolonged parenteral nutrition
without supplementation, diuretics,
PPI drugs, hyperglycemia osmotic
diuresis
S/S
Hypotension, facial flushing, lethargy, Resembles hypocalcemia**
N/V, impaired deep tendon reflexes,
muscle paralysis, respiratory &
Muscle crampls, tremors, hyperactive
cardiac arrest
deep tendon reflexes, Chvostek’s &
Trousseau’s signs, confusion, vertigo,
seizures
- treat underlying cause
Interventions
- prevention first!!
IV CaCl or calcium gluconate if
- oral supplements
symptomatic
- increase dietary intake
Fluids & IV furosemide to promote
- parenteral IV or IM MG when severe
urinary excretion
- dialysis
Acid-Base Regulation
 pH level – measure of H+ (hydrogen) ion concentration
o Normal range – 7.35 to 7.45
o Acidosis - < 7.35
 Increased H+ concentration
o Alkalosis - > 7.45
 Decreased H+ concentration
o Death results in a pH level under 6.8 or over 7.8
 3 mechanisms to regulate acid-base balance
o Respiratory regulation

 The lungs control the amount of
carbonic acid available by
retaining or exhaling CO2
 CO2 + H2O > H2CO3 > H+ + HCO3-

Respiratory center in the
medulla controls breathing
Class 16 (Chp. 16) – Fluids, Electrolytes, & Acid-Base Balance
 Increased respirations lead to
decreased CO2 in blood
increased CO2 elimination &
o Renal regulation
 The kidneys neutralize acid & base by excreting or retaining H+ ions & excreting or forming
bicarbonate ions
 Conserves bicarbonate & excretes acid
 3 mechanisms for acid elimination
 Excrete weak acids
 Secrete free H+
 Combine H+ with
ammonia (NH3)
o Buffer system
 Shifts H+ in & out of the cell
 Act chemically to change strong
acids to weak acids or bind
 Primary regulator of acidthem
balance
 Carbonic acid – bicarbonate,
phosphate, protein, hemoglobin
buffers
CVAD (central venous access devices)
 Catheters placed in large blood vessels
o Subclavian, jugular
 3 main types
o Centrally inserted catheters (central
lines)







Peripherally inserted central catheters
(PICC line)
o Implanted ports
Useful for patients with limited peripheral
vascular access or need for long-term vascular
access
Hemodynamic monitoring
Venous blood samples
Injection of radiopaque contract media
o
Permits frequent, continuous, rapid, or

intermittent admin of fluids & meds
Allows for giving drugs that are potentially
vesicants

Used to admin blood or blood products &

parenteral nutrition

Advantages
o Immediate access
o
o Reduced venipunctures
Disadvantages
o Increased risk of systemic infection
o
o Invasive procedure
o
o Clamped or kinked catheter
o
o Tip against wall of vessel
o
o Thrombosis
o
Interventions
o Inspect catheter & insertion site
o
o Change dressing & clear according to policy
 Transparent semipermeable dressing or gauze dressing
 Chlorhexidine preferred cleansing agent
o Change injection caps
o
Centrally inserted catheter
o Inserted into a vein in the chest or ABD
o
wall with the tip resting in the distal end
o
of superior vena cava
Decreased risk of extravasation
Precipitate buildup in lumen
Embolism
Risk of infection
Pneumothorax
Catheter migration
Assess for pain
Flushing is IMPORTANT!
Non-tunneled or tunneled
Dacron cuff anchors catheter &
decreases incidence of infection
Class 16 (Chp. 16) – Fluids, Electrolytes, & Acid-Base Balance
o Single, double, or triple lumen
o Examples of long-term tunneled catheters
 Hickman
 Broviac
 Groshong
 PICC lines
o Central venous catheter inserted into a
o For patients who need vascular access
vein in arm
for 1 week to 6 months
o Single or multi lumen, non-tunneled
o Can’t use arm for BP or blood draws
o Advantages
 Lower infection rate
 Decreased cost
 Fewer insertion-related
complications
o Disadvantages
 Deep vein thrombosis (DVT)
 Phlebitis
 Implanted port
o Central venous catheter connect to an implanted, single or double subcutaneous injection port
o Port is titanium or plastic with self-sealing silicone septum
o Drugs are injected through skin into port
o Advantages
 Good for long-term therapy
 Cosmetic discretion
 Low risk of infection
 Midline catheters
o Peripheral catheters
 3-8” long
 Single or double lumen
o Use & care similar to PICC lines
o May stay in place up to 4 weeks
Vocabulary
 Diffusion – movement of molecules across a permeable membrane from high to low concentration
o Facilitated diffusion – uses carrier to help move molecules
 Active transport – process in which molecules move against concentration gradient
o External energy is needed for this process
o Sodium-potassium pump – as Na+ diffuses into the cell & K+ diffuses out of the cell, the active transport
system supplied with energy delivers Na + back to ECF & K+ back to ICF
 Osmosis – movement of water down a concentration gradient from low solute concentration to high solute
concentration, across a semi-permeable membrane