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Clinical Pathology > Lecture 24 - Hydration and Osmolality > Flashcards

Lecture 24 - Hydration and Osmolality Flashcards

1
Q

Osmolality = [solute] per ______ of ______ (mOsm/kg)
- Aqueous solution with an osmolality of 1.0:
1 osmole of solute is added to 1 __ (1__) of water

A

Osmolality = [solute] per kilogram of SOLVENT (mOsm/kg)
- Aqueous solution with an osmolality of 1.0:
1 osmole of solute is added to 1 kg (1 L) of water

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2
Q

Osmolarity = [solute] per _____ of ______ (mOsm/L)
Aqueous solution with an osmolarity of 1.0:
1 osmole of a solute is placed in a beaker, and H2O is added to make ?

A

Osmolarity = [solute] per liter of SOLUTION (mOsm/L)
Aqueous solution with an osmolarity of 1.0:
1 osmole of a solute is placed in a beaker, and H 2 O is added to make 1 L

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3
Q

Technically, osmolality ___osmolarity; biologically they are ___________. For clinical purposes, we use the term __________.

A

Technically, osmolality ≠ osmolarity; biologically they are interchangeable
For clinical purposes, we use the term OSMOLALITY

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4
Q

Osmolality is measured by ?

A

Osmolality is measured by freezing-point depression osmometry

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5
Q

Osmolality measures ____ the osmoles in ______.

A

Osmolality measures all the osmoles in plasma

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6
Q

Normal plasma osmolality:
Dog: ______-____ mOsm/kg
Cat: _____-_____ mOsm/kg
Horse & Cow: _____-____ mOsm/kg

A

Normal plasma osmolality:
Dog: 210 -310 mOsm/kg
Cat: 290 -300 mOsm/kg
Horse & Cow: 270 -300 mOsm/kg

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7
Q

Estimate the plasma osmolality using an equation

A
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8
Q

Diuresis occurs when urine flow is ______ than normal.

Dogs and Cats: > ___-___ mL/kg/h

A

Diuresis occurs when urine flow is greater than normal.

Dogs and Cats: >1-2 mL/kg/h

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9
Q

When does osmotic diuresis occur?

Osmotic diuresis occurs when there is __________ urine flow caused by _______ amounts of ________ solutes within the renal tubules ( Example: 3?)
Urine osmolality approaches ______ osmolality
Example: diabetes mellitus (_________)

A

Osmotic diuresis occurs when there is increased urine flow caused by excessive amounts of impermeant solutes within the renal tubules ( Example: Na, Glucose, mannitol) Urine osmolality approaches plasma osmolality
Example: diabetes mellitus (glucosuria)

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10
Q

When does water diuresis occur?

Water diuresis occurs when there is _______ urine flow caused by decreased ________ of _____ water.
Urine osmolality may drop ______ plasma osmolality
Example: diabetes _______

A

Water diuresis occurs when there is increased urine flow caused by decreased reabsorption of free water.
Urine osmolality may drop below plasma osmolality
Example: diabetes insipidus

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11
Q

What is specific gravity?

Specific Gravity is the ratio of weight of a volume of ____ to the weight of an equal volume of _________ ________.

A

Specific Gravity is the ratio of weight of a volume of liquid to the weight of an equal volume of distilled water.

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12
Q

Specific gravity is dependent upon?

A

Dependent upon:
1. The number of particles present
2. The molecular weight of those particles

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13
Q

Urine Specific Gravity is an estimate of _________; there is a _______ relationship between them

A

Urine Specific Gravity is an estimate of osmolality; there is a linear relationship between them

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14
Q

How is Blood Volume and Body Fluid Tonicity maintained?

A
  • Both are maintained within a narrow range
  • 2 methods:
    1. Water balance … ADH/Vasopressin
    2. Sodium (Na) regulation … Aldosterone
  • Water balance controls
    • osmolality and Na concentration
  • Extracellular Fluid Volume (ECF) is determined by Na content
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15
Q

What does water balance depend on?

  • Depends on:
  • Adequate _____
  • _____ and ____ function
  • Losses in ______ and ________
  • ______ control

–> Requires a Functional Kidney
1. Adequate delivery of tubular ______
* Normal renal ______ flow
* Normal ________
* ________ resorption of ___ and ____ from the proximal tubules
2. Normal functioning ascending?
3. Collecting ducts remain ____________ to H2O

A
  • Depends on:
  • Adequate intake
  • Renal and GI function
  • Losses in sweat and respiration
  • Neural control

–> Requires a Functional Kidney
1. Adequate delivery of tubular fluid
* Normal renal plasma flow
* Normal glomerular filtration rate
* Isoosmotic resorption of Na and H2O from the proximal tubules
2. Normal functioning ascending Loop of Henle
3. Collecting ducts remain impermeable to H2O

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16
Q

Physical sensors: Osmoreceptors in the ____________

A

Physical sensors: Osmoreceptors in the hypothalamus

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17
Q

Hyperosmolality —> they ___ —> stimulates ____ release –> This increases water __________ via the kidney, Stimulates ____ response (?)

A

Hyperosmolality —> they shrink —> stimulates ADH release
ADH increases water reabsorption via
the kidney Stimulates thirst response
(drink water)

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18
Q

Hypoosmolality —> osmoreceptors ______ —>
__________ ADH release ,Increases renal
water ________

A

Hypoosmolality —> osmoreceptors swell —>
inhibits ADH release Increases renal
water excretion

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19
Q

Low body water and/or high plasma osmolality leads to:
* ↑ _____
* ↑ renal water __________

A

Low body water and/or high plasma osmolality leads to:
* ↑ thirst
* ↑ renal water reabsorption

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20
Q

Excess body water and/or low plasma osmolality leads to:
* ↑ renal water ________

A

Excess body water and/or low plasma osmolality leads to:
* ↑ renal water excretion

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21
Q

Water regulation affects plasma _________
It also affects the ______ concentration
_________ water, decreases [_____]
________ water, increases [____]

A

Water regulation affects plasma osmolality
It also affects the sodium (Na) concentration
Increase water, decreases [Na]
Decrease water, increases [Na]

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22
Q

__________ is the primary regulator of blood volume

A

Sodium is the primary regulator of blood volume

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23
Q

Regulation of Blood Volume
* It is regulated by sensing of:

A
  • Atrial stretch
  • Renal perfusion pressure
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24
Q

Regulation of Blood Volume
Hormones involved:?

A
  • Renin-angiotensin-aldosterone system
  • Sympathetic nervous system
  • Atrial natriuretic peptide (ANP)
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25
What are the major outcomes of blood volume regulation?
urine Na retention or excretion
26
** TBW is ~____% of body weight in healthy animals with a normal BCS
** TBW is ~60% of body weight in healthy animals with a normal BCS
27
TBW divided into sub-compartments: 1. Intracellular fluid (ICF) (___) 2. Extracellular fluid (ECF) (____) - Intravascular (“-volemia”) used to describe changes in blood _______ (____% of ECF) - Intercellular fluid - Transcellular/”Third spaces” – ________, ________, ________ - _____ tract
TBW divided into sub-compartments: * Intracellular fluid (ICF) (2/3) * Extracellular fluid (ECF) (1/3) * Intravascular (“-volemia”) used to describe changes in blood volume (25% of ECF) * Intercellular fluid * Transcellular/”Third spaces” – pleural, peritoneal, pericardial * GI tract
28
TBW volume determines hydration status * Controlled by water _____ (____) and renal ______
TBW volume determines hydration status * Controlled by water intake (thirst) and renal output
29
__________ are present in all intracellular and extracellular body fluids
Electrolytes are present in all intracellular and extracellular body fluids
30
Electrolytes are most commonly measured in _______
Electrolytes are most commonly measured in serum
31
_______ electrolyte concentrations may not completely reflect balance of electrolytes in the body (especially for _______ electrolytes).
Serum electrolyte concentrations may not completely reflect balance of electrolytes in the body (especially for intracellular electrolytes)
32
Maintaining appropriate concentrations of electrolytes within a ______ range is essential to maintain health and is achieved mainly by: ?
Maintaining appropriate concentrations of electrolytes within a narrow range is essential to maintain health and is achieved mainly by: GI tract & Kidneys
33
HIGHEST IN THE INTRACELLULAR FLUID (ICF)?
Paisley, Caroline, Meagan, and Parascandola * Potassium * Calcium * Phosphorus * Magnesium
34
HIGHEST IN THE EXTRACELLULAR FLUID (ECF)
* Sodium * Chloride Sodium (Na+) ◦ Primary cation in the ECF ◦ Most important cation for renal conservation of water ◦ Acquired through the diet ◦ Excreted through feces, urine, and sweat Chloride (Cl-) ◦ Primary anion in the ECF ◦ Important component of secretory fluids (gastric, sweat, and saliva) ◦ Typically moves in the same direction as sodium (electroneutrality) ◦ Typically moves in the opposite direction of bicarbonate Potassium (K+) Most is in the ICF K+ can be exchanged between ECF and ICF in acid-base imbalances
35
Osmolality = concentration of osmotically active particles (solutes) per ___ of ______ (_____ or _____) (expressed in mOsm/kg) * Solutes: electrolytes (mainly ____ and ___), _____, _____, ______ * Changes in ____ osmolality influence ______ water shifts between ECF and ICF
Osmolality = concentration of osmotically active particles (solutes) per kg of solvent (plasma or serum) (expressed in mOsm/kg) * Solutes: electrolytes (mainly Na+ and K+), proteins, glucose, urea * Changes in ECF osmolality influence passive water shifts between ECF and ICF
36
How is osmolality of the ECF measured? - Measured osmolality finds all the ______ in the blood. - Calculated osmolality only represents osmoles reported in the __________ _____. - Serum osmolality can be estimated based on the most numerous osmoles: ___________, ________, and ________.
Can be measured or calculated * Measured on an osmometer based on vapor pressure or freezing point depression * Calculated: Na + and K + units = mmol/L Glucose units = mg/dL BUN units = mg/dL - Measured osmolality finds all the osmoles in the blood. - Calculated osmolality only represents osmoles reported in the chemistry panel. - Serum osmolality can be es8mated based on the most numerous osmoles: electrolytes, glucose, and urea.
37
Normal serum osmolality ~ _______-______ mOsm/kg
300-310
38
Changes in plasma osmolality causes water shifts between ____ and ____ compartments
Changes in plasma osmolality causes water shifts between ICF and ECF compartments
39
Changes in plasma osmolality are usually associated with?
* Hypernatremia * Hyperglycemia * Ketoacidosis * Uremia * Presence of exogenous toxins (ie, ethylene glycol)
40
Plasma osmolality * Clinical signs depend on weather or not?
fluid shifts occur
41
Plasma hyperosmolality without fluid shifts * Increased plasma concentration of __________ solutes: intracellular osmolality ____ extracellular osmolality * Example: ______ * ____ clinical signs Urea is______ diffusible across cell membranes. Osmotic effects are __________
Plasma hyperosmolality without fluid shifts * Increased plasma concentration of ineffective solutes: intracellular osmolality = extracellular osmolality * Example: Uremia * No clinical signs Urea is freely diffusible across cell membranes Osmotic effects are negligible
42
Plasma hyperosmolality with fluid shifts * Increased plasma concentration of _______ solutes: intracellular osmolality is _____ than extracellular osmolality * Examples: ? * Leads to cellular _______ * Clinical signs: are those manifested of ______ cellular volume * _______ changes secondary to cellular ______ * Depression --> stupor --> Coma * Other neurologic changes: CNS deficits, Seizures
Plasma hyperosmolality with fluid shifts * Increased plasma concentration of effective solutes: intracellular osmolality is less than extracellular osmolality * Examples: Hypernatremia, Severe hyperglycemia (diabetes) * Leads to cellular dehydration * Clinical signs: are those manifested of cerebral cellular volume * Neurologic changes secondary to cellular dehydration * Depressionà stupor à Coma * Other neurologic changes: CNS deficits, Seizures
43
Plasma HYPO-osmolality with fluid shifts * Increased plasma concentration of _____ solutes: intracellular osmolality ___ extracellular osmolality * Examples: _________ * Leads to cellular _____: Cerebral ____ & Cell ___ * Clinical Manifestations of Cerebral Edema & Cell Lysis: * _______ changes secondary to cellular _______: Lethargy, weakness, Altered mentation, obtundation, seizures, death
Plasma HYPO-osmolality with fluid shifts * Increased plasma concentration of effective solutes: intracellular osmolality > extracellular osmolality * Examples: Hyponatremia * Leads to cellular swelling: Cerebral Edema & Cell Lysis * Clinical Manifestations of Cerebral Edema & Cell Lysis * Neurologic changes secondary to cellular dehydration: Lethargy, weakness, Altered mentation, obtundation, seizures, death
44
IMPORTANT: How do you calculate the Osmolar gap? Osmolar substances NOT included in osmolality calculation?
Osmolar gap = measured osmolality – calculated osmolality these are usually TOXINS or (some) therapeutics
45
Normal osmolar gap ~ ___ mOsm/kg
10
46
Osmolar gap is typically calculated to?
Typically calculated to differentiate between causes of increased serum osmolality
47
If the osmolar gap is >10 mOsm/kg, indicates the presence of osmolar substances _____ included in osmolality calculation: ?
If the osmolar gap is >10 mOsm/kg, indicates the presence of osmolar substances NOT included in osmolality calculation: * Ethylene glycol * Mannitol * Ethanol and methanol * Radiographic contrast media
48
Hydration: estimates?
TBW status
49
DEHYDRATION = _________ TBW 1. ________ body weight 2. Physical exam findings: * ________ skin tent * __________ capillary refill time * ______ mucous membranes * _________ eyes 3. Clinicopathologic parameters: * _________ * ___________ (?) * ____________ * _____________ * +/- ?
DEHYDRATION = DECREASED TBW 1. Decreased body weight 2. Physical exam findings: * Increased skin tent * Increased capillary refill time * Tacky mucous membranes * Retracted eyes 3. Clinicopathologic parameters: * Erythrocytosis * Azotemia (pre-renal) * Hyperproteinemia * Hypersthenuria * +/- Electrolyte abnormalities
50
OVERHYDRATION = ___________ TBW * __________ body weight * Accumulated fluid in _______ or _______ spaces * PatIents can be ________ with _______ TBW: * _______ or in ____ tract (rumen)
OVERHYDRATION = INCREASED TBW * Increased body weight * Accumulated fluid in extracellular or third spaces * PaIents can be hypovolemic with increased TBW: * Effusions or in GI tract (rumen)
51
Classification of dehydration 1. Type of fluid ______ from the body 2. Remaining ________ of body fluids
1. Type of fluid loss from the body 2. Remaining tonicity of body fluids
52
A. Hypertonic dehydration: water loss ____Na loss Na is _________
water loss > Na loss Na is increased
53
Isotonic dehydration: water loss __ Na loss Na is ________
water loss = Na loss Na is normal
54
Hypotonic dehydration: water loss ___ Na loss Na is ________
water loss < Na loss Na is decreased
55
Hypertonic dehydration: Plasma [Na] is _____
Plasma [Na] is INCreased
56
Water loss in excess of electrolyte loss * Differentials ? Water shifts from ___ to ____ to maintain ____ volume
Water loss in excess of electrolyte loss * Differentials: * Diabetes insipidus * Diabetes mellitus * Osmotic diuresis * Osmotic diarrhea * Water Deprivation Water shifts from ICF to ECF to maintain ECF volume
57
Isotonic dehydration: Plasma [Na] is _______
Normal
58
In Isotonic dehydration: Proportional loss of ? ◦ No change in _____ osmolality ◦ ____ and ___ concentrations do not change* Differentials: * _____ disease * ________ ◦ Water does not shift between ___ and _____ --> ___ volume decreases
In Isotonic dehydration: Proportional loss of Na+, Cl-, and water ◦ No change in ECF osmolality ◦ Na+ and Cl- concentrations do not change* Differentials: * Renal disease * Diarrhea ◦ Water does not shift between ICF and ECF --> ECF volume decreases
59
Hypotonic dehydration Plasma [Na] is ________
DECreased
60
In a case of Hypotonic dehydration: NaCl loss ____ water loss ◦ ECF osmolality _________ (________) ◦ Na+ and Cl- ________ ◦ Water shifts from ___ to ___ --> volume _______ --> Differentials:?
In a case of Hypotonic dehydration: NaCl loss > water loss ◦ ECF osmolality decreases (hypotonic) ◦ Na+ and Cl- decrease ◦ Water shifts from ECF to ICF --> volume depletion --> Differentials: * Secretory diarrhea * Vomiting * 3rd space loss * Heat stress & sweating in horses: Often Cl- losses are greater than Na+ losses
61
Hypotonic dehydration Problems 1. Fluid shifts from _________ into cells * Vascular volume _______ further, and cells _____ * Cerebral ______: * Occurs when Na+ < _____-_____ mEq/L * Especially with _______ change 2. Osmoreceptors _____ stimulated, ____ not released 3. May or may not have renal medullary _______
1. Fluid shifts from vasculature into cells * Vascular volume decreases further, and cells swell * Cerebral edema: * Occurs when Na+ < 115-120 mEq/L * Especially with rapid change 2. Osmoreceptors not stimulated, ADH not released 3. May or may not have renal medullary washout
62
**Overhydration * For example: Iatrogenic fluid overload * IV fluid administration with __________ elimination * Heart _______, _______ obstruction, _____/____ (RF) * May cause: * __________ overload * Pulmonary _______ * Generalized ______
**Overhydration * For example: Iatrogenic fluid overload * IV fluid administration with inappropriate elimination * Heart failure, renal obstruction, oliguria/anuria (RF) * May cause: * Cardiovascular overload * Pulmonary edema * Generalized edema

Clinical Pathology (31 decks)

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