The document discusses the composition and regulation of body fluids and electrolytes. It covers the following key points: - Approximately 60% of body weight is fluid located in two main compartments - intracellular and extracellular space. - Major electrolytes include sodium, potassium, calcium, magnesium, chloride, bicarbonate, and phosphate which are critical for cellular function and fluid balance. - The kidneys, lungs, skin, and gastrointestinal tract are responsible for regulating fluid and electrolyte balance through processes like filtration, sweating, and urine production. - Laboratory tests like osmolality, creatinine, and hematocrit are used to evaluate fluid status and renal function in maintaining homeostasis.

2. Amount &
Composition of body
fluids
Fundamental Concepts

3. Body Fluids
 Approximately 60% of the
weight of a typical adult
consists of fluid (water and
electrolytes).
 Factors that influence the
amount of body fluid are age,
gender, and body fat.
 People who are obese have less
fluid than those who are thin.
 Muscle, skin, and blood have
the highest amount of water.

4. Fluid
Compartments
2 fluid compartments:
 intracellular space (fluid in the cells)
 extracellular space (fluid outside the cells).
Intracellular
Extracellular

5. Fluid
Compartments
Fluid
Compartments
ECF
Intravascular
Interstitial
Transcellular
ICF

7. Intravascular
Space  Approximately 3 Lof the average 6 L of blood
volume is made up of plasma.
 The remaining 3 Lis made up of erythrocytes,
leukocytes, and thrombocytes.

8. Interstitial
Space
 The interstitial space contains the fluid that
surrounds the cell and totals about 11 to
12 Lin an adult.
 Lymph is an interstitial fluid.

9. Transcellular
space
 smallest division of the ECF compartment
 contains approximately 1 L
 include cerebrospinal, pericardial, synovial,
intraocular, and pleural fluids; sweat; and digestive
secretions.
 ECF transports electrolytes; it also carries other
substances, such as enzymes and hormones.

10. Third-Space
FluidShift
 Loss of ECF into a space that does not contribute to
equilibrium

11. Electrolytes
Fundamental Concepts

12. Electrolytes
 electrically charged molecules or ions that are found
inside and outside the cells of the body
 These ions contribute to the concentration of body
solutions and move between the intracellular and
extracellular environments.
 electrolyte concentration in the body is expressed in
terms of milliequivalents
(mEq)per liter, a measure of chemical
activity

13. Electrolytes
major cations
• Sodium
• Potassium
• Calcium
• Magnesium
• hydrogen ions
major anions
• Chloride
• Bicarbonate
• Phosphate
• Sulfate
• proteinate ions

15. Electrolytes
sodium (Na+)
 The major cation in extracellular fluid
 plays a major role in fluid regulation.
 As sodium is absorbed, water usually follows by osmosis.
potassium (K+)
 plays a critical role by influencing the resting membrane potential, which strongly affects cells that
are electrically excitable, such as nerve and muscle cells.
 Increased or decreased levels of K+ can cause depolarization or hyperpolarization of cells, resulting
in hyperactivity or inactivity of tissues such as muscles

16. Electrolytes
 Normal movement of fluids through the capillary wall
into the tissues depends on
hydrostatic
pressure(the pressure exerted by
the fluid on the walls of the blood vessel) and the
osmotic pressure exerted by the protein of plasma.
 The direction of fluid movement depends on the
differences in these two opposing forces (hydrostatic
versus osmotic pressure).

17. Regulationof body
Fluidcompartments
Fluid & Electrolytes

18. MethodsofFluid&ElectrolyteMovement
Diffusion
Osmosis
Active Transport
Filtration
Facilitated Diffusion

19. Osmosisand
Osmolality
Osmosis - water movement
across a membrane from an area of
low concentration to an area of high
concentration

20. Osmosisand
Osmolality
 The magnitude of this force depends on the number of
particles dissolved in the solutions, not on their weights.
 The number of dissolved particles contained in a unit of fluid
determines the osmolality of a solution, which influences the
movement of fluid between the fluid compartments
 Three other terms are associated with osmosis:
osmotic pressure,
oncotic pressure, and
osmotic diuresis.

21. Osmosis
 Osmotic pressure is the amount of hydrostatic
pressure needed to stop the flow of water by osmosis.
It is primarily determined by the concentration of
solutes.
 Oncotic pressure is the osmotic pressure exerted by
proteins (eg, albumin).
 Osmotic diuresis is the increase in urine output
caused by the excretion of substances such as glucose,
mannitol, or contrast agents in the urine

22. Tonicity
 the ability of all the solutes to cause an osmotic
driving force that promotes water movement from one
compartment to another.
 The control of tonicity determines the normal state of
cellular hydration and cell size
 ISOTONIC, HYPOTONIC, HYPERTONIC

23. Isotonic
Solution
 ISO - means alike
 Means that solutions on both sides of selectively permeable
membrane have established equilibrium
 Any solution put into body with the same osmolality as blood
plasma - 0.9% sodium chloride or 5% glucose

24. Hypotonic
Solution
 Solution of lower osmotic pressure
 Less salt or more water than isotonic
 If infused into blood, RBCs draw water into
cells ( can swell & burst )
 Solutions move into cells causing them to
enlarge

25. Hypertonic
Solution
 Solution of higher osmotic pressure
 3% sodium chloride is example
 If infused into blood, water moves out of cells &
into solution (cells wrinkle or shrivel)
 Solutions pull fluid from cells

26. Diffusion
 is the natural tendency of a substance to move from an area of higher concentration to one of lower
concentration
 It occurs through the random movement of ions and molecules
 Ex. exchange of oxygen and carbon dioxide between the pulmonary capillaries and alveoli and the
tendency

28. Facilitated
Diffusion
 Involves carrier system that moves substance across a
membrane faster than it would with simple diffusion
 Substance can only move from area of higher
concentration to one of lower concentration
 Ex. movement of glucose with assistance of insulin
across cell membrane into cell

30. Filtration
Hydrostatic pressure in the capillaries tends to filter fluid
out of the intravascular compartment into the interstitial
fluid.
Movement of water and solutes occurs from an area of high
hydrostatic pressure to an area of low hydrostatic pressure.
Ex. The kidneys filter approximately 180 L of plasma per
day.
Ex. passage of water and electrolytes from the arterial
capillary bed to the interstitial fluid; in this instance, the
hydrostatic pressure results from the pumping action of the

32. Active
Transport
Moves molecules or ions uphill
against concentration & osmotic
pressure
Hydrolysis of adenosine
triphosphate (ATP) provides
energy needed
Requires specific “carrier”
molecule as well as specific
enzyme (ATPase)
Eg. Sodium-Potassium Pump

33. Systemicroutesof
gainsand losses
Fluid and Electrolyte Balance

36. Kidneys
 The usual daily urine volume in the adult is 1 to 2 L.
 general rule: output is approximately 1 mL of urine
per kilogram of body weight per hour (1 mL/kg/h) in
all age groups.

37. Skin
 Sensible perspiration refers to visible water and
electrolyte loss through the skin (sweating).
 The chief solutes in sweat are sodium, chloride, and
potassium.
 Actual sweat losses can vary from 0 to 1000 mL or
more every hour, depending on factors such as the
environmental temperature.
 Continuous water loss by evaporation (approximately
600 mL/day) occurs through the skin as insensible
perspiration, a nonvisible form of water loss. Fever
greatly increases insensible water loss through the
lungs and the skin, as does loss of the natural skin
barrier (eg, through major burns).

38. Lungs
normally eliminate water
vapor (insensible loss) at a
rate of approximately 300 mL
every day.
The loss is much greater with
increased respiratory rate or
depth, or in a dry climate.

39. Gastrointestina
l Tract
 The usual loss through the GI tract is 100 to 200 mL
daily,

40. Laboratory tests for
evaluationfluidstatus
Fluid and Electrolyte Balance

41. LabTests
Osmolality
 the concentration of fluid that affects the movement of
water between fluid compartments by osmosis.
 measures the solute concentration per kilogram in
blood and urine.
 is also a measure of a solution’s ability to create
osmotic pressure and affect the movement of water.
 Urine osmolality is determined by urea, creatinine,
and uric acid.
 Osmolality is reported as milliosmoles per kilogram of
water (mOsm/kg)

42. Osmolality
 serum osmolality - 280 to 300 mOsm/kg
* Estimate: double the
sodium level or:
 urine osmolality - 200 to 800 mOsm/kg

44. Osmolarity
 another term that describes the concentration of
solutions
 measured in milliosmoles per liter (mOsm/L).
 osmolality is used more often in clinical practice.
 The calculated value usually is within 10 mOsm of the
measured osmolality.

45. Urinespecific
gravity
 measures the kidneys’ ability to excrete or conserve
water.
 normal range: 1.010 to
1.025.
 varies inversely with urine volume; normally, the
larger the volume of urine, the lower the specific
gravity is.
 a less reliable indicator of concentration than urine
osmolality
 increased glucose or protein in urine can cause a

46. BUN(Blood
UreaNitrogen)
 made up of urea, which is an end product of the metabolism
of protein (from both muscle and dietary intake) by the liver.
 Amino acid breakdown produces large amounts of ammonia
molecules, which are absorbed into the bloodstream.
 Ammonia molecules are converted to urea and excreted in
the urine.
 Normal range: 10 to 20 mg/dL
(3.6 to 7.2 mmol/L).

47. Creatinine
 end product of muscle metabolism
 a better indicator of renal function than BUN because
it does not vary with protein intake and metabolic
state.
 Normal range: approximately 0.7 to 1.4
mg/dL (62 to 124
mmol/L)
 concentration depends on lean body mass and varies
from person to person.
 Serum creatinine levels increase when renal function
decreases.

48. Hematocrit
 measures the volume percentage of red blood cells
(erythrocytes) in whole blood
 Normal range:
42% to 52%for males
35% to 47% for females
 Conditions that increase the hematocrit value :
dehydration and polycythemia
 decrease hematocrit : overhydration and anemia

49. UrineSodium
 As sodium intake increases, excretion increases; as the
circulating fluid volume decreases, sodium is conserved.
 Normal urine sodium levels range from 75 to
200 mEq/24 hours (75
to 200 mmol/24 hours).
 A random specimen usually contains more than 40 mEq/L of
sodium.
 Urine sodium levels are used to assess volume status and are
useful in the diagnosis of hyponatremia and acute renal
failure.

50. Homeostatic
mechanisms
Fluid and Electrolyte Balance

51. Kidney
Functions
 kidneys normally filter 180 Lof plasma
every day in the adult and excrete 1 to 2
Lof urine.
 They act both autonomously and in response to
bloodborne messengers, such as aldosterone and
antidiuretic hormone (ADH)

53. Kidneys
 Major functions in fluid balance:
 Regulation of ECF volume and osmolality by selective
retention and excretion of body fluids
 Regulation of normal electrolyte levels in the ECF by
selective electrolyte retention and excretion
 Regulation of pH of the ECF by retention of hydrogen
ions
 Excretion of metabolic wastes and toxic substances

54. Heartand
BloodVessel
Functions
 The pumping action of the heart circulates blood
through the kidneys under sufficient pressure to allow
for urine formation.
 Failure interferes with renal perfusion and thus with
water and electrolyte regulation.

55. LungFunctions
Through exhalation, the lungs remove
approximately 300 mL of water daily in the
normal adult.
Also play a major role in maintaining acid–base
balance.

56. Pituitary
Functions
 Functions of ADH include:
 maintaining the osmotic pressure of the cells by
controlling the retention or excretion of water by the
kidneys
 regulating blood volume

57. Adrenal
Functions
Aldosterone
 mineralocorticoid
 Increased secretion causes sodium retention (and thus water
retention) and potassium loss.
 decreased secretion causes sodium and water loss and
potassium retention.
Cortisol
 adrenocortical hormone
 has less mineralocorticoid action
 when secreted in large quantities (or administered as
corticosteroid therapy), can produce sodium and fluid
retention.

58. Parathyroid
Functions
 regulate calcium and phosphate balance by means of
parathyroid hormone (PTH).
 PTH influences bone resorption, calcium absorption
from the intestines, and calcium reabsorption from the
renal tubules.

59. Other
Mechanisms
Baroreceptors
 located in the left atrium and the carotid and aortic
arches.
 As arterial pressure decreases, baroreceptors transmit
fewer impulses from the carotid and the aortic arches
to the vasomotor center.

60. Baroreceptors
decrease in impulse
stimulates the
sympathetic nervous
system
increase in cardiac
rate, conduction, and
contractility
increase in circulating
blood volume.
inhibits the
parasympathetic
nervous system.

61. Baroreceptors
Sympathetic
stimulation
Constriction of renal
arterioles
increases the release
of aldosterone
decreases glomerular
filtration and
increases sodium and
water reabsorption.

62. Other
Mechanisms
Antidiuretic Hormone and Thirst
Oral intake is controlled by
the thirst center located in the
hypothalamus
The presence or absence of
ADH is the most significant
factor in determining whether
the urine that is excreted is
concentrated or dilute.

63. serum concentration
or osmolality
increases and blood
volume decreases
neurons in the
hypothalamus are
stimulated by
intracellular
dehydration
thirst occurs
person increases his
or her intake of oral
fluids.

64. Other
Mechanisms
Osmoreceptors
 Located on the surface of the hypothalamus,
osmoreceptors sense changes in sodium concentration.

65. Osmoreceptors
osmotic pressure
increases
neurons become
dehydrated
quickly release
impulses to the
posterior pituitary
Increases the release
of ADH
ADH travels in the
blood to kidneys
ADH alters
permeability to
water
causing increased
reabsorption of
water and decreased
urine output.

66. Other
Mechanisms
Atrial Natriuretic
Peptide
 also called atrial natriuretic factor
 a peptide synthesized, stored, and released by muscle cells of
the atria of the heart in response to several factors.
 These factors include:
 increased atrial pressure
 angiotensin II stimulation
 endothelin (a powerful vasoconstrictor of vascular smooth
muscle peptide released from damaged endothelial cells in
the kidneys or other tissues)
 sympathetic stimulation

67. Atrial
Natriuretic
Peptide
any condition that results in
volume expansion, hypoxia, or
increased cardiac filling
pressures increases the release of
ANP.
 The action of ANP is the direct
opposite of the renin-
angiotensin–aldosterone system;
ANP decreases blood pressure
and volume

69. Calculations

70. Rate = Volume (cc) x gtt factor (gtts/cc)
Duration (hrs) x 60 min/hr
Duration = Volume (cc) x gtt factor (cc)
Rate (gtt/min) x 60 min/hr
If ml/hr is known: ml/hr X drop factor
60 min
Calculate the flow rate using standard formula
Standard Formula:

71.  The physician’s order reads “Administer D5LR 3L for
24 hrs”
a. To how many gtts/min will you regulate the IVF?
b. How many mls/hr will be infused?

72. Order: 1000 ml of D5NSS to infuse over 12 hours
Available: macrodrip set with 10 gtts/ml
a. gtts/min?

73. 100 cc/hr gtts/min? (Baxter/macroset)

74. PNSS 1L @ 120 gtts/min (Abbott)
Hours to run?

75.  A liter of IV fluid was started @ 9 AM and was to
infuse for 8 hours. The IV set delivers 10 gtt/ml. Four
hours later only 400 ml were absorbed.
a. How much IV fluid was left?
b. Recalculate the flow rate for the remaining IV
fluids.