1. Chapter 41: Fluid, Electrolyte, and Acid-Base Balance
Bonnie M. Wivell, MS, RN, CNS

2. Distribution of Body Fluids
Intracellular = inside the cell; 42% of body weight
Extracellular = outside the cell, 17% of body weight
Interstitial = contains lymph; fluid between cells and outside blood vessels
Intravascular = blood plasma found inside blood vessels
Transcellular = fluid that is separated by cellular barrier,
Transcellular fluids: CSF, pleural, GI, intraocular, peritoneal, and synovial
Loss of transcellular fluid can produce fluid and electrolyte disturbances

3. Body Fluid Compartments

4. Functions of Body Fluid
Major component of blood plasma
Solvent for nutrients and waste products
Necessary for hydrolysis of nutrients
Essential for metabolism
Lubricant in joints and GI tract
Cools the body through perspiration
Provides some mineral elements

5. Composition of Body Fluids
Body fluids contain Electrolytes
Anions – negative charge
Cl, HCO3, SO4
Cations – positive charge
Na, K, Ca
Electrolytes are measured in mEq
Minerals are ingested as compounds and are constituents of all body tissues and fluids
Minerals act as catalysts
Body fluids made up of electrolytes
Electrolyte is an element
Separates into ions – cations (positive, Na+, K+, Ca+) and anions (negative, Chloride, bicarbonate [HCO3}
Minerals (Example: Iron and Zinc)
Initiate nerve responses
Initiate muscle contractions
Metabolize nutrients in foods
Regulate electrolyte balance
Regulate hormone production
Strengthen bones
Too much or too little causes serious consequences

6. Electrolytes in Body Fluids
Normal Values
Sodium (Na+) – 145 mEq/L
Potassium (K+) – 5.0 mEq/L
Ionized Calcium (Ca++) – 5.5 mg/dL
Calcium (Ca++) – 10.5 mg/dL
Bicarbonate (HCO3) 24 – 30 mEq/L
Chloride (Cl--) – 105 mEq/L
Magnesium (Mg++) – 2.5 mEq/L
Phosphate (PO4---) – 4.5 mg/dL

7. Movement of Body Fluids
Osmosis = movement across a semi-permeable membrane from area of lesser concentration to are of higher concentration; high solute concentration has a high osmotic pressure and draws water toward itself
Osmotic pressure = drawing power of water (Osmolality)
Osmolarity = concentration of solution

8. Movement of Body Fluids
Colloid or Oncotic pressure = keeps fluid in the intravascular compartment by pulling water from the interstitial space back into the capillaries

10. Solutions Isotonic Solution Hypotonic Solution Hypertonic solution
The same concentration as blood plasma; expand fluid volume without causing fluid shift
Hypotonic Solution
Lower concentration than blood plasma; moves fluid into the cells causing them to enlarge
Hypertonic solution
Higher concentration than blood plasma; pulls fluid from cells causing them to shrink

11. Movement of Body Fluids Cont’d.
Diffusion = Molecules move from higher concentration to lower
Concentration gradient
Filtration = water and diffusible substances move together across a membrane; moving from higher pressure to lower pressure
Edema results from accumulation of excess fluid in the interstitial space
Hydrostatic pressure causes the movement of fluids from an area of higher pressure to area of lower pressure
Concentration gradient = the difference between the two concentrations (i.e. movement of oxygen and CO2 between the alveoli and blood vessels in the lungs

14. Active Transport
Requires metabolic activity and uses energy to move substances across cell membranes
Enables larger substances to move into cells
Molecules can also move to an area of higher concentration (Uphill)
Sodium-Potassium Pump
Potassium pumped in – higher concentration in ICF
Sodium pumped out – higher concentration in ECF

16. Regulation of Body Fluids
Homeostasis is maintained through
Fluid intake
Hormonal regulation
Fluid output regulation

17. Fluid Intake Hypovolemia occurs when excess fluid is lost
Thirst control center located in the hypothalamus
Osmoreceptors monitor the serum osmotic pressure
When osmolarity increases (blood becomes more concentrated), the hypothalamus is stimulated resulting in thirst sensation
Salt increases serum osmolarity
Hypovolemia occurs when excess fluid is lost

18. Fluid Intake Average adult intake
2200 – 2700 mL per day
Oral intake accounts for 1100 – 1400 mL per day
Solid foods about 800 – 1000 mL per day
Oxidative metabolism – 300 mL per day
Those unable to respond to the thirst mechanism are at risk for dehydration
Infants, patients with neuro or psych problems, and older adults

19. Hormonal Regulation ADH (Antidiuretic hormone)
Stored in the posterior pituitary and released in response to serum osmolarity
Pain, stress, circulating blood volume effect the release of ADH
Increase in ADH = Decrease in urine output = Body saves water
Makes renal tubules and ducts more permeable to water

20. Hormonal Regulation Cont’d.
Renin-angiotensin-aldosterone mechanism
Changes in renal perfusion initiates this mechanism
Renin responds to decrease in renal perfusion secondary to decrease in extracellular volume
Renin acts to produce angiotensin I which converts to angiotensin II which causes vasoconstriction, increasing renal perfusion
Angiotensin II stimulates the release of aldosterone when sodium concentration is low

21. Hormonal Regulation Cont’d.
Aldosterone
Released in response to increased plasma potassium levels or as part of the renin-angiotensin-aldosterone mechanism to counteract hypovolemia
Acts on the distal portion of the renal tubules to increase the reabsorption of sodium and the secretion and excretion of potassium and hydrogen
Water is retained because sodium is retained
Volume regulator resulting in restoration of blood volume

22. Hormonal Regulation Cont’d.
Atrial Natriuretic Peptide (ANP)
ANP is a hormone secreted from atrial cells of the heart in response to atrial stretching and an increase in circulating blood volume
ANP acts like a diuretic that causes sodium loss and inhibits the thirst mechanism
Monitored in CHF

23. Fluid Output Regulation
Organs of water loss
Kidneys
Lungs
Skin
GI tract

24. Fluid Output Regulation Cont’d.
Kidneys are major regulatory organ of fluid balance
Receive about 180 liters of plasma to filter daily
1200 – 1500 mL of urine produced daily
Urine volume changes related to variation in the amount and type of fluid ingested
Skin
Insensible Water Loss
Continuous and occurs through the skin and lungs
Can significantly increase with fever or burns
Sensible Water Loss occurs through excess perspiration
Can be sensible or insensible via diffusion or perspiration
500 – 600 mL of insensible and sensible fluid lost through skin each day

25. Fluid Output Regulation Cont’d.
Lungs
Expire approx 500 mL of water daily
Insensible water loss increases in response to changes in resp rate and depth and oxygen administration
GI Tract
3 – 6 liters of isotonic fluid moves into the GI tract and then returns to the ECF
200 mL of fluid is lost in the feces each day
Diarrhea can increase this loss significantly

26. Regulation of Electrolytes
Major Cations in body fluids
Sodium (Na+)
Potassium (K+)
Calcium (Ca++)
Magnesium (Mg++)

27. Sodium Regulation Most abundant cation in the extracellular fluid
Major contributor to maintaining water balance
Nerve transmission
Regulation of acid-base balance
Contributes to cellular chemical reactions
Sodium is taken in via food and balance is maintained through aldosterone

28. Potassium Regulation
Major electrolyte and principle cation in the extracellular fluid
Regulates metabolic activities
Required for glycogen deposits in the liver and skeletal muscle
Required for transmission of nerve impulses, normal cardiac conduction and normal smooth and skeletal muscle contraction
Regulated by dietary intake and renal excretion

29. Calcium Regulation Stored in the bone, plasma and body cells
99% of calcium is in the bones and teeth
1% is in ECF
50% of calcium in the ECF is bound to protein (albumin)
40% is free ionized calcium
Is necessary for
Bone and teeth formation
Blood clotting
Hormone secretion
Cell membrane integrity
Cardiac conduction
Transmission of nerve impulses
Muscle contraction

30. Magnesium Regulation Essential for enzyme activities
Neurochemical activities
Cardiac and skeletal muscle excitability
Regulation
Dietary
Renal mechanisms
Parathyroid hormone action
50 – 60% of magnesium contained in bones
1% in ECF
Minimal amount in cell

31. Anions Chloride (Cl-) Bicarbonate (HCO3-) Major anion in ECF
Follows sodium
Bicarbonate (HCO3-)
Is the major chemical base buffer
Is found in ECF and ICF
Regulated by kidneys

32. Anions Cont’d. Phosphate (PO4---) Buffer ion found in ICF
Assists in acid-base regulation
Helps to develop and maintain bones and teeth
Calcium and phosphate are inversely proportional
Promotes normal neuromuscular action and participates in carbohydrate metabolism
Absorbed through GI tract
Regulated by diet, renal excretion, intestinal absorption and PTH

33. Regulation of Acid-Base Balance
Lungs and kidneys are our buffering systems
A buffer is a substance that can absorb or release H+ to correct an acid-base imbalance
Arterial pH is an indirect measure of hydrogen ion concentration
Greater concentration of H+, more acidic, lower pH

34. Regulation of Acid-Base Balance
Lower concentration of H+, more alkaline, higher pH
The pH is also a reflection of the balance between CO2 (regulated by lungs) and bicarb (regulated by kidneys)
Normal H+ level is necessary to
Maintain cell membrane integrity
Maintain speed of cellular enzymatic actions

35. Chemical Regulation
Carbonic acid-bicarbonate buffer system is the first to react to change in the pH of ECF
H+ and CO2 concentrations are directly related
ECF becomes more acidic, the pH decreases, producing acidosis
ECF receives more base substances, the pH rises, producing alkalosis
Lungs primarily control excretion of CO2 resulting from metabolism
Kidneys control excretion of hydrogen and bicarb

36. Biological Regulation
Buffer actions that occur
Exchange of K+ and H+
Carbon dioxide goes into RBCcarbonic acid (HCO3-)
HCO3 ready to exchange with Cl-
Chloride shift within RBC H+ H+ K+ K+ K+
Hydrogen ion has positive charge and must be exchanged by another positively charged ion – usually K+
Excessive acid – H+ enter cell and K+ leaves it’s house into extracellular fluid (ECF), resulting in elevated K+
Carbon dioxide shifts into RBC’s ---- produce carbonic acid ----disassociates into H+ and bicarbonate ions
H+ attach to Hgb and bicarbonate (HCO3-) becomes ready to exchange for chloride (Cl-)
Chloride shift within RBCs
Normally Chloride travels from the Hgb to plasma during inspiration and plasma to Hgb on expiration
Bicarb diffuses in and out of the cells H+ H+ H+

37. Acidosis vs Alkalosis Acidosis Alkalosis
Acids have high H+ ions in solution
Alkalosis
Bases have low H+ ion concentration
Acidity or Alkalinity of a solution measured by pH
Higher H+ ions the more acidic and the lower the pH
Water has a pH of 7 and is neutral
Death at each end of spectrum
Urine pH is (check)

38. Physiological Regulators
Lungs
Regulate by altering H+ ions
Metabolic acidosis
Metabolic alkalosis
Kidneys
Regulate by altering HCO3 and H+ ions H+ H+
HCO3
HCO3
Lungs –
Regulate H+ ions
Alter rate, depth of respirations to correct
Metabolic acidosis [high H+] Respirations increase to exhale more CO2 [which is a potential acid, carbonic acid – H2CO3]---carbonic acid level falls which results in homeostatis or becoming less acidic
Happens quickly
Metabolic alkalosis (bicarbonate levels are high) --respirations reduced, CO2 retained causing carbonic levels to raise
Kidneys – take longer to regulate (few hours to days)
Regulate bicarbonate production
Acidosis – excessive H+, kidneys reabsorb HCO3 (bicarbonate) and excrete H+ ions
Alkalosis – Low H+ ions – kidneys excrete HCO3 and retain H+ ions
HCO3
HCO3

39. Causes of Electrolyte Imbalances
Excessive sweating
Fluid loss leading to dehydration
Excessive vomiting
Diuretics like Lasix (K+ depletion)
Massive blood loss
Dehydration may go unnoticed in hot, dry climates
Renal failure
Treatments will be directed at eliminating the cause

40. Sodium Most abundant in extracellular space
Moves among three fluid compartments
Found in most body secretions Na Na
Sodium
Problem is because Na is found is most body fluids
Loss of sodium without loss of body fluids, sodium becomes diluted in ECF
Vomiting, suctioning, diarrhea, burn, diuretics, SIADH Na Na Na

41. Hyponatremia – Low Sodium
Seizures
Personality changes
Nausea/vomiting
Tachycardia
Convulsion
Normal Na ( )
Most common cause is over-hydration with D5W
Post-op fluid replacement
Heart failure
Cirrhosis

42. Hypernatremia Excessive Na in ECF Loss of water Gain of Sodium
Diarrhea
Insensible water loss
Water deprivation
Gain of Sodium
Diabetes insipidus
Heat stroke
1. Fluid moves outside cell – cells dehydrated
Signs and symptoms
Dry skin
Dry mucus membranes, tongue
Low BP
Fever
CNS - Agitated
Restless
Lab values – Na high, Urine – high Specific gravity
Thirst
Causes
Diabetic ketoacidosis -
Diabetes Insipidus - caused by a lack of response to ADH. 
commonly called pituitary DI.   It is also known as central or neurogenic DI. 
posterior pituitary can be destroyed by - tumors, infections, head injuries, infiltrations, and various inheritable defects

43. Hypokalemia – Low Potassium
Severe leg cramps
Flaccid muscles
Fatigue
Irregular pulse
Chest discomfort
EKG changes
T wave flattens
Normal Potassium-3.5-5
Note - hypokalemia [aLKalosis associated with Low K]
Potassium
Acquired in the diet
Excreted in urine
Must be replaced daily
Function
Maintains acid-base balance
Participates in metabolism
Causes
Poor intake – patient is not eating
Renal loss (diuretics)
GI loss (diarrhea, vomiting)
Signs and symptoms
Tachycardia
Low BP
Flaccid muscles
EKG – Flattened T wave
Treatment
Oral replacement if preferable, could be IV
Low K+ could lead to digoxin toxicity due to low circulating volume

44. Hyperkalemia CNS Peripheral Nervous System Heart Nausea and vomiting
Tremors, twitching
Heart
Bradycardia, peaked T wave
Too much Potassium – less common than hypokalemia and More dangerous
Common Causes
Renal failure (Rarely occurs in person with normal renal function)
Signs and symptoms
Bradycardia (high K+ suppresses SA node)
Tremors, twitching
N/V
EKG changes – Peaked T, PVC’s, arrhythmias
Treat
Kayexalate
Insulin – pushes K+ back into the little house
Dialysis

45. Hypocalcemia – Low Calcium
Tingling of fingers
Tetany
Muscle cramps
Positive Trousseau’s
Carpal spasm
Positive Chvostek’s
Contraction of facial muscle when facial nerve tapped
1. Calcium
1. Neuromuscular activity
2. Cardiac activity
3. Blood coagulation
Etiology – how does this happen
Surgical hypothyroidism
Pancratitis
Renal failure
Vit. D deficiency
3. Signs and Symptoms
1. Hyperactive reflexes
2. Hypotension
3. Positive Trousseaus
4. Positive Chevostek’s
5. Prolonged QT interval
Trousseau’s Sign - a test for latent tetany in which carpal spasm is induced by inflating a sphygmomanometer cuff on the upper arm to a pressure exceeding systolic blood pressure for 3 minutes. A positive test may be seen in hypocalcemia and hypomagnesemia.
Treatment
Oral route is safer
IV: calcium gluconate over 5-10 minutes
Monitor EKG

46. Hypercalcemia Causes Signs/symptoms Prolonged immobility Osteoporosis
Thiazide diuretics
Acidosis
Signs/symptoms
N/V, weakness
Hypoactive reflexes
Cardiac arrest
Etiology
Ca is stored in the bones
Essential for neuromuscular activity, cardiac activity, blood coagulation
Cause of hypercalcemia
Hyperparathyriodism (parathyroids control Ca levels by production of calcitonin
Paget’s disease (bone metabolism disease)
Excessive Vit. D intake
Prolonged immobility
Paget's disease is a metabolic bone disease that involves bone destruction and re-growth, which results in deformity.
Signs and symptoms
Anorexia, N/V
Coma
Flaccid muscles
Arrhythmias and cardiac arrest
Treatment
Fluids
IV aredia, pamidronate

47. Hypomagnesemia Causes Signs/symptoms Malnutrition Alcoholism Polyuria
Pre-ecclampsia
Signs/symptoms
Muscle tremor
Hyperactive deep reflexes
Chvostek’s/Trousseau’s
Difficulty breathing
Magnesium
Intracellular reactions and utilization of ATP
CNS transmissions
Cardiovascular tone
Etiology
Pancreatitis
Cirrhosis
GI losses
Alcoholism
Calcium gluconate administration
Treatment of Diabetic ketoacidosis
S/S
Increased deep tendon reflexes
Chvostek’s/Trousseaus signs pos
EKG changes
Pre-ecclampsia
Condition that is not fully understood
Occurs in about 8% of pregnancies
Symptoms are: high BP, edema in extremities, protein in urine, aches, blurred vision and possible seizures
Treat – with Magnesium sulphate IV – acts as vasodialator (causes flushing and hypotension)

48. Hypermagnesemia Causes Signs/symptoms Renal failure Excessive intake
Low BP
Muscle weakness
Absent reflexes
Bradycardia
Etiology (not common)
Renal disease
Hypercalcemia
Adrenal insufficiency
Signs and symptoms
Flushing
Low BP, slow pulse
Respiratory depression
Hypoactive reflexes
Increase in Mg depresses skeletal muscles and nerve function
Most common cause is renal failure
Bradycardia due to depression of acetylcholine
Decreased respirations,coma, ECG changes

50. Respiratory alkalosis pH ↑ PaCO2 ↓ HCO3 ↑ Metabolic acidosis PaCO2
Respiratory acidosis
pH ↓
PaCO2 ↑
HCO3 ↓
Respiratory alkalosis
pH ↑
PaCO2 ↓
HCO3 ↑
Metabolic acidosis
PaCO2
Metabolic alkalosis
1. Respiratory acidosis [more CO2 indicates acidosis]
pH - <7.35
PaCO2 – excess CO2
HCO3- low carbonic acid [HCO3 levels are lower than normal indicates acidosis
2. Respiratory alkalosis [more CO2 being exhaled than normal results in alkalosis]
pH - > 7.45
PaCO2 – low CO2
HCO3 - high carbonic acid
3. Metabolic acidosis
PaCO2 - normal
HCO3 – low bicarbonate
4. Metabolic alkalosis
HCO3- high bicarbonate

51. Cheat Sheet Increase pH – alkalosis Decrease pH – acidosis
Respiratory – CO2
Metabolic (kidneys)– HCO3
CO2 has an inverse relationship with pH
When pH goes down, CO2 goes up
HCO3 follows pH. If pH goes up so does HCO3
CO2 increases, pH decreases – resp. acidosis
CO2 decreases, pH increases – resp. alkalosis
HCO3 increases, pH increases – metabolic alkalosis
HCO3 decreases, pH decreases – metabolic acidosis

52. Question
An older client comes to the emergency department experiencing chest pain and shortness of breath. An arterial blood gas is ordered. Which of the following ABG results indicates respiratory acidosis?
1. pH , PaCO2 – 28, HCO3 – 22
2. pH – 7.32, PaCO2 – 46, HCO3 – 24
3. pH – 7.31, PaCO2 – 35, HCO3 – 20
4. pH – 7.5, PaCO2 – 37, HCO3 - 28
#2 – Because of the retention of CO2, the clinical profile of respiratory acidosis includes decreased pH < 7.35, PaCO# - > 42 with varying levels of HCO3 related to hypoventilation
Option #1 is respiratory alkalosis which occur because of blowing off CO2 resulting in decreased level of acid and retention or production of HCO3 resulting in pH > 7.45
Option #3 is Metabolic acidosis because of high H+ or loss of HCO3 often caused by diarrhea, or retention related to kidney failure
Option #4 – metabolic alkalosis caused by increased HCO3, or loss of H+, related to vomiting, gastric suction or loss of upper GI secretions

53. Review Acid/Base Imbalance Tutorial
How do we assess for acid-base balance?

54. Assessment Nursing history Prior Medical History Cancer CVD
Age
Prior Medical History
Acute illness
Surgery
Burns increase fluid loss
Resp. disorder predisposes to resp. acidosis
Head Injury can alter ADH secretion
Chronic illness
Cancer
CVD
Renal disorders
GI disturbances

55. Assessment Cont’d.
Environmental factors affecting fluid/electrolyte alterations
Diet
Lifestyle – smoking, ETOH
Medications
Physical Assessment
Daily weights
I&O
Vital signs
Laboratory Studies
How do we assess for acid-base balance?
Focus on skin, mouth, eyes, cardiovascular system, respiratory system, neurologic, muscular
Laboratory tests
Serum electrolytes
CBC – HCT measures volume of blood that is composed of RBC, affected by changes in volume
HCT increases with dehydration – increases with over hydration
Serum osmolarity – measures amount of Na, glucose, urea or BUN in blood – increase indicates fluid volume deficit, decrease reflects fluid volume excess
Urine pH – acidosis - urine pH should decrease as kidneys secrete H+ ions –
metabolic alkalosis pH would increase as kidney retains H+ ions
Urine sodium and chloride excretion – indicate renal perfusion
Arterial Blood Gases

56. Nursing Diagnosis Decreased cardiac output Acute confusion
Deficient fluid volume
Excess fluid volume
Impaired gas exchange
Risk for injury
Deficient knowledge regarding disease management
Impaired oral mucous membrane
Impaired skin integrity
Ineffective tissue perfusion

57. Planning Determine goals and outcomes Set priorities
Collaborative care MD
Dietician
Pharmacy

58. Implementation Health promotion Acute care Education
Enteral replacement of fluids
Restriction of fluids
Parenteral replacement of fluids and electrolytes
TPN
IV fluids and electrolyte therapy (crystalloids)
Blood and blood components (colloids)
Blood groups and types
Autologous transfusion
Transfusion reactions
ABGs

59. Restorative Care Home IV therapy Nutritional support Medication safety
Pt. education

60. Evaluation Have goals been met? Have changes in assessment occurred?
Progress determines need to continue or revise plan of care