Chapter 7

Chapter 7

Nursing Care of Clients with Alterations in Fluid, Electrolyte, or Acid-base Balance

Fluid Balance in the Body

Functions of fluid in the body– medium for transport and exchange of

nutrients– medium for metabolic reactions– regulates body temperature– form for body/cell structure and shock

absorber– provides insulation and lubrication

Fluid Compartments

Intracellular - fluid within the cells extracellular - fluid outside of the cells

– interstitial - in the spaces between the cells– intravascular - within the ateries and veins– transcellular - urine, digestive secretions

Third-spacing - trapped extracellular fluid Edema - accumulation in interstitial

spaces

ICF and ECF

ICF- fluid within the cells accounts for about 40% of total body weights. Electrolytes, glucose and oxygen.

Extracellular fluid- Fluid outside of the cells. About 20% of total body weight. Found in 3 compartments:

- Interstitial fluid- Spaces between most of the cells of the body

15% of total body weight.- Intravascular fluid or plasma- In the arteries, veins and

capillaries. About 5% of body weight.- Transcellular fluid- cerebrospinal fluid, urine, digestive

secretions, perspiration and small amounts of fluid found within organs and joints. Less than 1% of body weight.

- ECF- Transports oxygen and nutrients to cells and waste away.

Distribution

Electrolytes are found in both fluid compartments, although the concentration or amount of individual electrolytes in the ICF and ECF differs.

Na+, chloride (CL), and bicarbonate (HCO3) are plentiful in extracellular fluid.

Potassium (K+), magnesium (Mg+), and phosphate (PO4) are plentiful in the intracellular fluid. The cell membrane and capillary walls separate the body

fluid compartments. Water and solutes move across these membranes by the processes of osmosis, diffusion, filtration and active transport.

Membrane Transport Processes

Osmosis - water moves across a membrane that is permeable to water but not to solutes,

Osmosis

Osmosis is responsible for water movement between the ICF and ECF compartments.

Water moves toward a higher solute concentration!

Membrane Transport ProcessesDiffusion - when molecules move from an area of high concentration to an area of low concentration to become evenly distributed

Diffusion

Molecules move across a semipermeable membrane from an area of higher solute concentration to an area of lower concentration.

Filtration

Process in which water and solutes move across capillary membranes driven by fluid pressure. This pressure is created by the pumping action of the cardiac muscle and gravity.

A balance between filtration and osmosis regulates the movement of water between the intravascular and interstitial spaces in the capillary beds of the body.

Membranes are selectively permeable, they allow water and some solutes o2, co2, electrolytes and glucose to cross. Block proteins and large molecules.

Membrane Transport Processes

Active transport - molecules are moved, carried across a cell membrane, usually large water soluble molecules - glucose

Regulatory Mechanisms

Thirst - primary regulator of water intake, fluid balance prevent dehy.

Kidneys - Renin-Angiotensin-Aldosterone Mechanism– regulate fluid volume and electrolyte balance

Antidiuretic Hormone Mechanism (ADH)– secreted by pituitary, acts on kidney to

increase water absorption, decrease.

Regulatory Mechanisms

The kidneys, by selectively reabsorbing water and electrolytes maintain the volume and osmolality of body fluids.

Renin-Angiotensin-Aldosterone System-Maintains the intravascular fluid balance and blood pressure.

Antidiuretic Hormone- Regulates water excretion from the kidneys.

Renin-Angiotensin-Aldosterone System A fall in blood flow to the kidneys (decreased fluid

volume), stimulates receptors in the kidney to produce renin (an enzyme). Renin coverts angiotensinogen in the blood into angiotensin one.

The lungs then convert angiotension one to angiotension two by ACE.

Angiotension TWO constricts blood vessels which raises blood pressure, it also stimulates thirst, releases aldosterone from the adrenal cortex and acts directly on the kidneys, causing them to retain sodium and water, thus restoring blood volume.

Antidiuretic Hormone

Regulates water excretion from the kidneys. Receptors in the hypothalamus detect changes in

osmolality and blood volume stimulating ADH production and release as needed.

When ADH is present more water is reabsorbed in the kidney; urine output falls, blood volume is restored and serum osmolality drops as the water dilutes body fluids.

See disorders: diabetes insipidus, inappropriate ADH secretion (SIADH).

Thirst

The thirst center in the brain is stimulated when the blood volume drops because of water losses or when the solute content of body fluids increases.

The thirst mechanism declines with age, so older adults are more vulnerable to dehydration.

Clients with impaired consciousness or who are unable to respond to thirst also are at risk

Osmosis and fluid volume

Isotonic solutions such as normal saline 0.9% sodium chloride solution have the same concentration of solutes as blood plasma. Cells placed in an isotonic solution do not gain or lose water.

Hypertonic solutions such as 3% sodium chloride solution have a greater concentration of solutes than plasma. A cell placed in a hypertonic solution shrinks as water is drawn out of it into the solution.

Hypotonic solutions such as 0.45% sodium chloride have a lower solute concentration than plasma. A cell placed in a hypotonic solution swells as water moves.

Dehydration - Fluid Volume Deficit

The Client With Fluid Volume Deficit Patho - excessive fluid losses, insufficient

fluid intake or a combination of both; vomiting, diarrhea or GI suction.

Multisystem effects– Neurological– Integumentary– Cardiovascular

• hypotension

– Urinary– Musculosketel

Fluid Volume Deficit Interdisciplinary Care

– Fluid Challenge• obtain base line vs, give fluid bolus, re-eval vs

– IV solutions• isotonic - .9% n.s. or Ringer’s Lactate tx

hypotension

• hypotonic - .45% n.s. - maintenance solutions

Nursing Care: Fluid Volume Deficit Assessment of factors contributing to

abnormal fluid loss Assess intake and output, daily wt Assess vital signs

– hypotension and tachycardia Assess for dehydration Adm. po and IV fluids Assess labs: LOC, Urine output

Fluid Volume Excess

Fluid volume excess– overhydration - excess intake– excessive sodium intake– disease process; CHF, liver cirrhosis

• Kidney failure, drugs Na retention, high Na foods, Na containing fluids

Clinical Manifestations– Tachycardia, bounding pulse,tachypnea,crackles in

lungs – Of edema fluid into sub Q tissue- eyes,dep.

Clinical Manifestations Respiratory

– cough– SOB, crackles and wheezes, orthopnea– pleural effusion

Cardiovascular– elevated B/P, full and bounding pulses

Abdominal– ascities

Neurological- Fatigue, altered LOC

Pulmonary edema

What has happened here?

Nursing Care: Fluid Volume Excess Assessment - I & O, V.S. heart sound S3

(gallop), daily wt Administer fluids cautiously Client teaching

– sodium and fluid restriction- Na retention.– meds and side effects– signs of fluid retention– symptoms to report

Electrolytes

Electrolyte Disorders -SodiumNa+ 136 - 148 normal range Hyponatremia - sodium level; Acid Base

<136mEq/L. Maintains ECF volume, bal Causes

– burns, excessive sweating, G.I. losses– diuretics, Addison’s disease, renal disease

Treatment– .9% N.S. 3%N.S– loop diuretics– fluid restriction

Electrolyte Imbalances

Hypernatremia - > Na+ 148mEq/L Causes

– too much Na+ in excess water– loose too much water and not enough sodium

Treatment - correct slowly over 2 days– D5W or .45% N.S. hypotonic soln to correct

water deficit– low Na+ diet

K+ packs a punchprimary intracellular cation. Vital

Electrolyte Disorders - Potassium

K+ 3.5 to 5.0 mEq/L normal range vital intercellular cation - helps determine cell

contractility nerve and muscle cells, must be replaced

Every day! Hypokalemia - K+ <3.5

– Causes• urinary loss

• G.I. loss

Potassium imbalance

The kidneys eliminate potassium very efficiently; even when potassium intake is stopped, the kidneys continue to excrete potassium.

Thus potassium must be replaced every day!!!All foods contain K+, some more plentiful than others. Which ones?

Electrolyte Disorders: hypokalemia

– Clinical Manifestations• neuro- decrease in reflexes

• cardio - dysrhythmias, cardiac arrest

• G.I. - n/v, anorexia, diarrhea

• musculosketel - weakness, leg cramps

– Treatment• K+ replacement

– oral - need to dilute– parental - DILUTE ALWAYS, pain at site, pump dilute

in IV fluids Is a must; or death!!!!!!!!!!!!!!

Electyrolyte Disorders: Hyperkalemia K+ >5mEq/L Causes

– inadequate excretion of K+ - Renal disease– Excessive intake of K+ - K+ sparing

diuretics, salt substitutes Clinical Manifestations

– Neuromuscular activity - tremors, twitching– Cardiac - dysrhythmias

Electrolyte Imbalance: hyperkalemia Treatment

– potassium loosing diuretics - lasix– Insulin - D50 - sodium bicarb

• causes K+ to shift back into the cells

– Kayexalate - exchange resin (Na+ and Ca+)

• oral, NGT, enema

– Sorbitol - promote bowel elimination

Fluid Balance, Lets Review

What are the causes of “Fluid Volume Deficit?”

Clinical Manifestations?– Neuro? Integ? Cardiovascular?– Urinary? Muscular/skeletal?

Fluid Volume Excess What are the causes of “Fluid Volume

Excess?” What are the clinical manifestations?

– Respiratory? – Cardiovascular?– Abdominal?– Neurological?

Nursing Care - Fluid Volume Excess

What should you assess for? What might you find?

What should you teach and why?

Electrolyte Disorders

Hypokalemia K+ < 3.5 What are some of the causes? Clinical Manifestations?

– Neuro? Cardio? G.I.? Musculo/skel? Treatment?


Calium Disorders Ca+ 8.8 - 10.0mg/dL normal range

– hyper and hypocalcemia– secondary to other disease processes – Hypercalcemia

• hyperparathyriodism - thyroid tumor, bone CA

– Hypocalcemia• hypoparathyriodism, parathyroid surgery


Phosphorus PO4 2.5 - 4.5mg/dL

– Hypophosphatemia• TPN, high concentrated glucose soln• GI loss, ETOH withdrawal

– Hyperphosphatemia• Renal failure - builds up in blood stream


Magnesium Mg+ 1.3 - 2.1mEq/L– Hypomagnesium

• ETOH abuse• GI disorders -impaired absorption-diarrhea • Diuretics

– Hypermagnesemia• Renal Disease

Acid base balance

Acid-Base Balance

For optimal cell function acid base balance must remain within the normal pH range of 7.35-7.45. 7 is neutral.

Thus this would imply that the ratio of bicarbonate to carbonic acid is about 20:1.

The hydrogen ion concentration of a solution is measured as its pH.

As hydrogen ion concentration increases the pH falls, and the solution becomes more acidic.

As hydrogen ion concentration falls, the pH rises, and the solution becomes more alkaline or basic.

Acid Base

Acids are continually produced by metabolic processes in the body.

Two types of acids 1. Volatile – Which can be eliminated as a gas. Co2 2. Nonvolatile- Must be metabolized or excreted from the body

in fluid. Hydrochloric acid, lactic acid, phosphoric acid. Three systems in the body work together to maintain a normal

pH despite continuous acid production: Buffers system, respiratory system, and renal system.

Normal pH systems

Buffer- Chemicals that prevent major changes in pH by attaching to or releasing hydrogen ion. (hemoglobin, plasma proteins, inorganic phosphates)

Respiratory system- Regulates carbonic acid in the body by eliminating or retaining carbon dioxide. Acute increases in either carbon dioxide or hydrogen ions in the blood stimulate the respiratory center in the brain to increase the rate and depth of respirations. This eliminates carbon dioxide from the body; carbonic acid levels fall and the pH goes to a normal range. Occurs within minutes; becomes less effective over time.

Alkalosis (pH above 7.45) depresses the respiratory center, the rate and depth of respirations decrease and co2 is retained

Patients with chronic lung dx may have high co2 levels in blood

Normal pH systems

Renal system- responds slowly(hrs to days). Longe term regulation of acid-base balance.

The kidneys regulate bicarbonate levels in the ECF and can either excrete or retain hydrogen ion as needed.

When excess hydrogen ions are present and the pH falls, the kidneys excrete hydrogen ions and retain bicarbonate.

When bicarbonate levels are high(pH incr) the kidneys retain hydrogen ion and excrete bicarbonate to restore acid-base balance.

Assessment of Acid Base

Acid-base balance is evaluated by measuring arterial blood gas. ABG’s Elements Measured: PaCO2, PaO2, bicarbonate and the pH. Arterial blood is used because it reflects acid-base balance

throughout the body and allows evaluation of oxygenation. Pressure for at least 5 minutes after lab draw. RN, respiratory

therapist or lab tech with specialized training. Arteries are high pressure vessles.

ABG’s are analyzed to identify acid-base disorders and their probably cause, extent of the imbalance, monitor treatment.

Acid -Base Definitions

Acid - a molecule that can contribute a hydrogen ion

Base - a molecule that can accept or remove a hydrogen ion

Buffer - substance that controls hydrogen ion concentration in a soln by absorbing H+ when acid is added or by releasing H+ when base is added

Acid- Base Disorders

Hydrogen Ion concentration pH 7.35 - 7.45

Classification of Acid-base Disorders– Acidosis - pH <7.35– Alkalosis - pH >7.45– metabolic - buffer system releasing bicarb– respiratory - control hydrogen ion

concentration by controlling resp rate

Metabolic Acidosis

Causes– severe diarrhea– renal disease– untreated diabetes– starvation

Treatment - fix underlying cause– bicarbonate - IV or PO– Resp increase rate and depth of respiration

Metabolic Alkalosis

Causes– Vomiting, loose acid.– diuretics– too much sodium bicarb

Treatment– fix the underlying cause– oral K+ supplements

Respiratory Acidosis

Causes: pH less than 7.35– any condition that impairs gas exchange,

pneumonia, COPD, chronic bronchitis• CO2 is retained, chest trauma

– rapid shallow breathing– hypoventilation -brain stem injury, drug OD

Treatment– Respiratory support - 02 - breathing tx -

ventilator

Respiratory Alkalosis Causes: pH greater than 7.45

– hyperventilation• asthma, high altitude• excessive mechanical ventilation; Hyperven.• anxiety attack

– CO2 deficiency secondary to hyperventilation

Treatment– breath into paper bag– re-breath CO2

Diagnostic Tests Acid Base Balance Sodium (Na)- 135-145 mEq/L Potassium (K+)- 3.5-5.3 mEq/L Calcium (Ca)- 4.5-5.5 mEq/L Magnesium (Mg+)- 1.5-2.5 mEq/L Chloride (CL-)- 95-105 mEq/L Bicarbonate (HCO3)- 24-28 mEq/L Phosphate/Phosphorus- 1.7-2.6 mEq/L Serum Osmolality- 280-300 mOsm/kg Urine Specific Gravity – 1.005-1.030

NCLEX

The primary electrolyte that controls the water balance in the body is:

A. Na B. K C. chloride D. magnesium

NCLEX

Mr. Smith has recently been diagnosed with a kidney dysfunction. He constantly complains of thirst. Which of the following statements to the client best indicates the nurse’s understanding of the thirst mechanism?

A. “Thirst is the primary regulator of water intake. When we are thirsty we drink.”

B. “Thirst is important in maintaining fluid balance and preventing dehydration.”

C. “Thirst mechanisms decline with age, making the older adult at risk for dehydration.”

D. “ A drop in blood volume stimulates the thirst center in the brain, which produces the sensation of thirst.”

NCLEX

The mechanism of action for the antidiuretic hormone (ADH) may be defined as:

A. kidneys reabsorb more water when the hormone is present B. kidneys cease urine production when the hormone is present C. blood osmolality increases as urine output decreases D. the hypothalamus detects increased osmolality of the blood

and stimulates the release of ADH.

NCLEX

Alice is a 2-year-old who has been suffering from vomiting and diarrhea for three days. Temperature is 102 f and she appears lethargic and exhausted. Her mother reports that Alice has not been able to keep anything down. Based on this information, Alice’s primary nursing diagnosis should be:

A. Activity intolerance B. Deficient fluid volume C. Altered nutrition: Less than body requirements D. Risk for diarrhea

NCLEX

Which electrolyte is most readily excreted by the kidneys and will be lost even when other electrolytes are conserved?

A. K+ B. sodium C. Magnesium D. Calcium

NCLEX

Which of the following statements is FALSE regarding the acid-base balance system?

A. Blood buffers react quickly but are limited B. The respiratory system adjusts the acid-base balance by

either slowing or increasing respirations C. The renal system is the slowest of the systems but is

responsible for long-term balance D. When hydrogen ions and the pH in the blood increase, the

result is acidosis

NCLEX

A client suffering from metabolic acidosis is most likely to:

A. experience an increase in the blood pH B. develop tachypnea C. recover slowly, due to the kidney’s role in acid-

base balance D. be diagnosed with acute pneumonia

NCLEX

Mr. Jacobs who was diagnosed with COPD 5 years ago has been using his oxygen at home via nasal cannula. The flow rate is set at 2L/minute. Mr. Jacobs respirations are 28/minute and her complains of SOB after minimal exertion. His wife is concerned that the amount of oxygen is “too low”. Your best response should be:

A. I can’t change the flow rate without an order. B. Okay, let’s increase the flow rate to 6L/minute and see how

he does. C. increasing his oxygen may actually block his respiratory

center in the brain. D. I will call the provider and let them know about your concerns

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Chapter 7