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RUSVM Clinical Pathology > Water Balance and Electrolytes > Flashcards

Water Balance and Electrolytes Flashcards

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1
Q

For clinical purposes, do we use osmolaity or osmolarity?

A

Osmolality

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2
Q

What is osmolality?

A

[solute] per kg of Solvent (mOsm/kg)

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3
Q

How are osmoles measured in plasma?

A

Freezing-point depression osometry

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4
Q

What is tonicity?

A

AKA effective osmolaity

Ability of a solution to initiate water movement

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5
Q

What type of solute is distributed equal through the total body water, causing no H20 movement

A

Permeant solute

Eg BUN

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6
Q

What type of solute does NOT readily distribute across cell membranes and will cause H20 movment

A

Impermeant solute

Eg Na, Glu, Mannitol

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7
Q

_____________ dieresis occurs when there is increased urine flow caused by excessive amounts of impermeant solutes within the renal tubules

A

Osmotic

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8
Q

What is the normal urine flow rate in dogs and cats?

A

> 1-2mL/kg/hr

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9
Q

__________ dieresis occurs when there is increased urine flow caused by decreased reabsorption of free water

A

Water

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10
Q

What is specific gravity?

A

Ratio of weight of a volume of liquid to the weight of an equal volume of distilled water

-estimate of osmolality

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11
Q

What is urine specific gravity dependent on?

A

Number of particles present

Molecular weight of those particles

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12
Q

________ regulates water balance and ___________ regulates sodium

A

ADH/vasopressin

Aldosterone

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13
Q

How do the osmoreeptors in the hypothalamus maintain water balance?

A

Hyperosmolality -> shrink -> ADH release -> H20 reabsorption in kidney and thirst response

Hypoosmolality -> swell -> inhibit ADH release -> increased water excretion

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14
Q

ADH responds to

A

Small increases in osmolality

Large decreases in plasma volume

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15
Q

ADH acts on which part of the nephron by increasing expression of ______

A

Collecting ducts; aquaporins

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16
Q

What electrolyte is the primary regulator of blood volume

A

Sodium

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17
Q

Blood volume regulated by sensing of??

A 
Atrial stretch (ANP)
Renal perfusion pressure (RAAS)
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18
Q

What effect does aldosterone have on sodium

A

Converse sodium (and water)

Secrete potassium

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19
Q

What is hypertonic dehydration?

A

Water loss > Na loss

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20
Q

What is isotonic dehydration?

A

Water loss = Na loss

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21
Q

What is hypotonic dehydration?

A

Water loss < Na loss

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22
Q

You have confirmed dehydration, Na is increased.

Type of dehydration?

A

Hypertonic

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23
Q

Dehydration confirmed, Na is normal.

Type of dehydration?

A

Isotonic

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24
Q

Dehydration is confirmed, Na is decreased

Type of dehydration

A

Hypotonic

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25
What are your DDX for hypertonic dehydration?
Diabetes insipidus / mellitus Osmotic dieresis Osmotic diarrhea Water deprivation
26
What is the DDX for isotonic dehydration
Renal disease | Diarrhea
27
What is the DDX for hypotonic dehydration ?
Secretory diarrhea Vomiting 3rd space loss (effusions) Heat stress and sweating in horse
28
T/F: in a hypotonic dehydration fluid shifts from vasculature and into cells and osmoreceptors will stimulate ADH release
False Fluid into cells -> cell/osmoreceptor swelling -> ADH release is inhibited
29
Cerebral edema occurs when Na is < _________ mEq/L
115-120
30
When do we usually see overhydration?
Iatrogenic | Iv fluid admin with inappropriate elimination like heart failure, renal obstruction, or oliguria/anuria
31
Over hydration can cause ??
Cardiovascular overload Pulmonary edema Generalized edema
32
Will you see clinical signs if your plasma concentration of ineffective solutes is increased (eg uremia)
No Urea is freely diffusible across cell membranes-> osmotic changes are negligible
33
Wil you see clinical signs associated with an increased plasma concentration of effective solutes (eg hpernateremia or hyperglycemia )
Yes Cellular dehydration -> cerebral cellular volume and neurological changes (depression, stupor, coma)
34
Decreased plasma concentration of effective solutes will have what clinical manifestations (eg hyponatremia)
Cellular swelling --> cerebral edema and cell lysis Lethargy, weakness, altered mentation, obtundation, seizure, death
35
What is the normal plasma osmolality in dogs and cats?
Dog 300 mOsm/kg Cat 310 mOsm/kg
36
In a chemistry panel, how is osmolality determined?
Calculated 2[Na] + [Glu]/18 + [BUN]/3
37
What is the osmole gap and what does an increase in this gap mean?
OG= measured osmolality - calculated osmolaity Increase means there is an osmotically active molecule in blood that is not measured on the serum biochemical profile
38
Interpret: Measured osmolality - increased Calculated osmolality - increased Osmole gap < 30
Increase in an osmole reported on the chemical Eg Na, glu, or BUN Usually represents sodium
39
Interpret: Measured osmolality - decreased Calculated osmolality - decreased Osmol gap < 30
Hyponatremia | Even a marked decreased in BUN or GLU will only cause minor decreased in osmolality
40
Interpret: Measured osmolality - increased Calculated osmolality - normal Osmole gap > 30(increased)
Probable toxin (or drug) Eg ethylene glycol or mannitol
41
What is the major extracellular ion
Na
42
How is sodium regulated?
Adequate intake (esp herbivores) Aldosterone - renal absorption Intestinal absorption ADH- indirectly influence Na
43
What are the 3 major mechanisms that alter sodium?
Change in intake Redistribution Changes in excretion
44
If water shifts from ICF -> ECF, what effect will this have on sodium?
Hyponatremia
45
T/F: hyponatremia can result due to an effusion?
True Na shift from vasculature to the effusion - heart failure and liver fialure --> edematous states
46
What are sources of sodium loss that can result in a hyponatremia
Renal, GI, cutaneous
47
What 3rd space syndromes can result in a hyponaterima?
``` Peritonitis Ascities Uroabdomen Chylothorax GI sequestration ```
48
Hyperglycemia or mannitol administration can have what effect on sodium?
Hyponatremia -> redistribution Water pulled by Glu or mannitol --> decreased concentration of Na
49
What is the most common cause of hyponatremia?
Hypovolemia GI -vomiting, diarrhea, or saliva Renal - hypoadrenocorticism, ketonuria, glucosuria, prolonged dieresis Cutaneous - sweating, burns
50
What are the consequences of hyponatremia ?
Hyposmolality | Cellular and cerebral edema (cellular overhydration)
51
Hypernatremia can result form?
Increased intake of Na Decreased H2o intake H20 lost in excess of Na (GI, renal, insensible losses)
52
A diabetic patient is markedly hyperglycemia, what do you expect the sodium concentration to be?
Hyponatremia
53
A diabetic patient is markedly hyperglycemic. What is the mechanism that drives the change in Na+?
Water shifts from the ICF to the ECF
54
Is chloride a extracellular or intracellular ion?
Extracellular BFFs with sodium
55
If the change in Cl- and Na+ are proportional, what should be your top differential?
Abnormalities in Na | DDX for hyper or hypo-natremia
56
If the change in Cl- concentration are greater than Na+, what should be your top DDX?
Acid-base abnormalities
57
How is chloride regulated?
Controlled by electrochemical gradients Corresponds to active transport of sodium
58
What is the most common cause of selective chloride loss?
Hypochloremic metabolic alkalosis Gastric HCl are NOT resorbed by small intestine Monogastric- severe vomiting Ruminant- abomasal disorder and high GI obstruction
59
Selective chloride loss in horse is likely due to?
Sweating
60
What is paradoxical aciduria associated with hypochloremia?
Metabolic alkalosis -> excrete HCO3- in kidney Dehydration causes reabsorption Na and HCO3 (normally would be Cl- but we are lacking) --> exacerbated alkalosis
61
``` Glu H 545 BUN H 70 CREA H 7.1 ALB H 4.7 GLOB H 5.6 ``` Na L 130 (136-147) Cl L 47 (95-105) Interpret
Albumin and globulin high => dehydration Pre-renal azotemia CL = 47 x 141/130 = 51 -> still below reference => selective chloride loss
62
What acid base abnormality accompanies a selective chloride loss?
Metabolic alkalosis
63
Causes of hyperchloremia?
Parallels increases with Na+ Hyperchloremic metabolic acidosis (GI loss of HCO3) Alkalemia
64
How does an alkalemia cause a hyperchloremia?
HCO3- excreted in distal nephron Generate H+ Cl- follows H+ into plasma
65
Is potassium an intracellular or extracellular ion?
Intracellular
66
What are clinical signs associated with abnormal serum K+ concentrations?
Cardiac dysfunction - can be life threatening Skeletal muscle dysfunction -> change in posture
67
How is potassium regulated?
Intake Renal excretion -promoted by aldosterone (K exchanged for Na) GI loss Sweat
68
What is the most common cause of hyperkalemia?
Failure of renal excretion Eg oliguria/anuria/renal failure/obstruction
69
In what cases will you see hyperkalemia due to redistribution?
Inorganic acidosis Insulin deficiency Muscle trauma: rhabdomyolysis Massive hemolysis
70
What endocrine abnormality can cause a hyperkalemia?
Hypoadrenocorticism | Decreased aldosterone -> Na is not reabsorbed and not exchanged for K
71
Pharm throw back... | What diuretics could cause a hyperkalemia?
Potassium sparing diuretics Spirnolactone Amiloride
72
What are causes of a redistribution hyperkalemia ??
Inorganic acidosis Insulin deficiency Massive cellular lysis
73
How does acidemia contribute to hyperkalemia ?
Preserve vascular pH, H+ moves into the ICF To maintain electroneutrality, K+ will move into the ECF
74
How does an insulin deficiency cause hyperkalemia ?
Glucose pull water out of cells -> cell shrinks and increases K+ concentration --> K+ into the vasculature
75
What types of cellular lysis can lead to hyperkalemia?
Rhabdomyolysis Acute tumor lysis syndrome Severe hemolytic syndrome K+ is released from lysed cells into vasculature
76
What are causes of a pseudo hyperkalemia?
EDTA contamination Marked thrombocytosis Hemolysis
77
Which animals have high RBC K+ concentrations and you can see a pseudohyperkalemia is serum is not separated quickly
``` Horse Pig Cattle Mice, rat Monkey ``` Akitas some Japanese dog breeds
78
Clinical signs associated with hypokalemia
Weakness Neurologic signs EKG abnormalities: flattened T waves (K < 2.5mmol/L)
79
How does diarrhea contribute to hypokalemia?
Losss of K+ and HCO3- Bicarbonate lost via GI causes metabolic acidosis -> H+ is exchanged for K+ -> serum K may appear normal even but there is a total body K deficiency
80
Alkalemia causes a hypokalemia. But how?
Maintain vascular pH by moving H+ (titrates with HCO3-) into the ECF -> K+ moves into the cell to maintain electroneutrality
81
T/F: insulin can cause a hyperkalemia
False Hypokalemia because insulin up regulates Na/K ATPase --> K into cell

RUSVM Clinical Pathology (18 decks)

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