Chem lect 19: Electrolytes Acid/Base Flashcards

1
Q

Hyperkalemia

Hypokalemia

A
  • Hyperkalemia
    • can cause cardiac arrest
  • Hypokalemia
    • can cause respiratory arrest
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2
Q

Total body water

A
  • 60% body weight
  • 2/3 in cells
  • 1/3 extracellular
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3
Q

Increase in fluids

Decrease in fluids

A
  • Increase
    • GI (water/food)
    • Renal (resorb water)
  • Decrease
    • Renal (polyuria)
    • GI (vomit & diarrhea)
    • Cooling (fever & sweat)
    • Drainage of effusions
    • chylous/thoracic effusions
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4
Q

Abnormal Body Water Volume

A
  • Dehydration => whole body water depletion
    • chronic renal failure cat
  • Hypovolemia => intravascular fluid depletion
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5
Q

Lidocaine MOA

A
  • Sodium channel blocker
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6
Q

Main intracellular ion

A

Potassium

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7
Q

Electrolyte that controls nerve conductions

heart, etc

A

Ionized calcium

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8
Q

Hypernatremia

A
  • Can cause cellular dehydration and CNS signs
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9
Q

Osmolality

A
  • Regulation of body water movement
  • Osmotic pressure caused by small solutes
    • sodium, chloride, potassium, glucose, urea
  • Proteins contribute miniscule amount (only present in small numbers)
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10
Q

Colloid osmotic pressure

(oncotic pressure)

A
  • primary force holding fluids intravascularly
  • due to plasma proteins
    • more so ablumins >>> globulins
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11
Q

Renin-antiotensin-aldosterone system

A
  • regulation of body water volume
    • sodium determines BP
  • sodium is primary osmotically active particle in ECF
    • water follows sodium
  • Water volume regulated on sodium balance
    • 97 % of sodium always resorbed by kidney
    • 3 % of sodium subject to hormonal regulation
      • activley resorbed if aldosterone is present
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12
Q

DCM

A
  • DCM
    • enlarged and weakened left ventricle
    • decreases hearts ability to pump blood
    • Dobies and big breeds
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13
Q

HCM

A
  • ventricles become abnormally thick
  • Most commonly diagnosed cardiac disease in cats
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14
Q

raas schematic

A

Liver => Angiotensinogen => Kidney => Renin => angiotensin I => ACE => Angiotensin II => Aldosterone

Kidney makes aldosterone

Aldosterone makes kidney increase sodium and decrease potassium

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15
Q

Body volume fluid

Physical

Laboratory

A
  • Physical
    • Hydration parameters
      • skin turgor
      • mm moisture
      • body weight
    • Intravascular Volume and Perfusion parameters
      • MM color & CRT
      • Heart rate and Pulse Quality
      • Blood pressure
      • Central venous pressure
  • Laboratory
    • Hydration parameters
      • PCV/TS
      • Urine specific gravity
    • Intravascular volume and perfusion parameters
      • BUN/Creatinine
      • Lactate
        • will be high in hypovolemia
      • *interpret in light of concurrent disease
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16
Q

Pre-renal azotemia

A
  • High BUN/Creatinine
  • High USG
  • High PCV/TS

*NOT RENAL FAILURE

*This is a patient not urinating

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17
Q

Low BP plus hypovolemia

A

Will eventually cause renal failure

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18
Q

Osmolality short equation

Long equation

A

Na X 2

2 (Na + K) + (Glucose / 18) + (BUN / 2.8)

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19
Q

Testing osmolality

A
  • Not very common
  • usefull for
    • suspected ethylene glycol intoxication
    • suspected pseudohyponatremia
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20
Q

Hyperosmolality

A
  • Increased solute
    • hypernatremia
    • hyperglycemia (severe)
    • Ethylene glycol intoxication
    • mannitol administration
    • increased urea
  • Decreased water
    • hypotonic fluid loss
      • to rumen, for example
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21
Q

Hypoosmolality

A
  • Hyponatremia
    • not all hyponatremics are hypoosmol
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22
Q

Hyperosmolality

Clinical signs

A
  • CNS with hypoosmolality hemolysis
    • due to cellular dehydration or overhydration
    • depends on
      • occurance of fluid shifts (e.g. urea)
      • Severity of change in osmolality
      • Rate of development-physiologic compensation
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23
Q

Colloid Osmotic Pressure (COP)

A
  • Major force holding fluid intravascularly (mm Hg)
  • Regulated by liver synthesis of albumin
  • Globulins are minor contributer
  • Often inferred from plasma protein conc.
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24
Q

Decreased COP

Signs

A
  • Due to loss of fluid from vasculature
  • Depends on how severe and rapid
  • effusions, edema, signs of hypovolemia

Causes

  • Hypoalbuminemia: PLE, PLN, Hepatic failure, others
  • Vascular leak (SIRS): vasculitis, sepsis, pancreatitis, others
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25
Q

Job of aldosterone

A
  • Absorb Na
  • Dump K
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26
Q

Electrolye concentrations

A
  • Sodium
  • Potassium
  • Chloride
  • Bicarbonate

Sodium : Potassium ratio

  • to see if has addisons (no aldosterone)
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27
Q

Electrolytes

Sample Collection

test question

A
  • Fasted serum sample separated from clot ASAP
    • red top tube, no anticoagulant
    • decreases artifacts due to
      • postprandial lipemia (calcium) - falsly decreases electrolytes
      • leakage of intracellular components (potassium)
  • Heparinized plasma may be used
    • gree top, lithium heparin
  • Do not use anticoagulants that chelate
    • ​purple top (potassium EDTA)
    • blue top (sodium citrate)
28
Q
  1. Really high potassium in a blood sample

w/o high calcium or magnesium

  1. High K level incompatible with life, Ca and Mg too low for life…

test question

A
  1. Possibly got too much of potassium supplemented fluids in blood sample from catheter line
  2. Blood was taken from a purple top and put into tiger top
29
Q

Effect of catheters on vasculature

A
  • Can activate clotting cascade
  • you are hypercoagulable anytime you have a clot
30
Q

Electrolyte artifacts due to K-EDTA

(purple top)

test question

A
  • K is four times what it should be
  • Ca and Mg decreased and incompatible with life
    • EDTA chelates divalent cations
  • Bicarbonate (TCO2) decreased
    • looks like acidosis
    • EDTA = ethylene diaminetraacetic ACID
31
Q

Electrolyte Artifacts due to Na-Citrate

(light blue top….?)

A
  • Sodium increased
    • Na in the anticoagulant
  • Divalent cations (Ca2+, Mg2+) decreased
    • citrate chelates divalent cations
  • Bicarbonate (TCO2) decreased
    • looks like acidosis
    • Citrate = Citric acid
  • Chloride decreased
    • dilution due to excess anticoagulant
32
Q

Sodium

Function

Regulation

Measurement

A
  • Functions
    • major extracellular fluid electrolytes
    • major determinant of osmolality
    • essential for control of hydration (RAAS)
  • Concentration regulated by
    • Adequate intake (herbivores)
    • Intestinal absorption
    • Renal tubular resorption (RAAS)
  • Measurement
    • Reflects body sodium content (extracellular electrolyte)
    • Interpret in light of hydration status
33
Q

Sodium Abnormal Concentration

Hypernatremia

Hyponatremia

A
  • Hypernatremia
    • inc Na
    • dec water
  • Hyponatremia
    • dec Na
    • inc water

Sodium and water can be lost together

  • Na and Cl almost always travel together
    • disorders affecting Na almost always affect Cl
  • Water follows salt
  • sodium concentration may be normal, animal will appear dehydrated
34
Q

Hypernatremia

Decreased water

Increased sodium

A
  • Decreased water
    • inadequate intake
    • loss of sodium poor fluid
      • renal
      • GI
      • Insensible
    • third space sequestration
      • effusion
      • rumen
  • Increased sodium
    • Salt poisoning
    • Sea water ingestion
    • Iatrogenic (fluids)

*mild hypernatremia common with dehydration

*severe hypernatremia uncommon

35
Q

Hypernatremia

Clinical signs

dz examples

A
  • Due to hyperosmolality
    • depression
    • dementia
    • seizures
    • coma
  • Depend upon severity and rate of development
    • compensation (idiogenic osmoles) may occur
  • Dz examples
    • lack of ADH secretion = central diabetes insipidus
      • renal loss of pure water
    • hypotonic diarrhea
      • GI loss of sodium poor fluid
36
Q

Hyponatremia (common)

Decreased sodium

A
  • Loss of sodium
    • GI V/D
    • Renal
      • Diuresis (primary renal dz, osmotic)
      • Hypoadreocorticism
        • addisons (body not making aldosterone)
  • Third spacing sequestration
    • chylothorax w/ repeated drainage
    • uroabdomen
  • Deficient intake (herbivores)
37
Q

Hyponatremia (common)

Increased water

A
  • Hyperosmolal NOT from inc Na
  • Edema
  • Psychogenic polydipsia
  • near drowning in fresh water
  • iatrogenic (fuid admin)
  • Inappropriate ADH secretion
38
Q

Sodium and water lost together

A
  • Hyponatremia
  • Calf diarrhea
  • measured Na concentration may be normal
    • whole body Na can be depleted tho
    • animal will appear dehydrated +/- hypovolemic
39
Q

Pseudohyponatremia (uncommon)

A
  • Can happen when looking at a lipemic sample as artifact
    • ion-specific electrodes don’t know how to measure lipemic samples
    • point of care blood gas machines NOT AFFECTED (ICU)
      • ​dry chem analysis, doesn’t need water to measure
40
Q

Potassium

Functions

Concentration affected by

Measurement

A
  • Function
    • major intracellular fluid electrolyte
    • essential for cardiac and skeletal muscle function
  • Concentration affected by
    • external potassium balance
      • GI, Renal, Sweat
    • Internal potassium balance
      • shifts between intracellular and extracellular fluids
    • Combination of both internal and external
  • Measurement
    • poor reflection of body potassium content
    • interpret in light of acid base status
41
Q

Internal Potassium Balance

A

Metabolic acidosis excess hydrogen ions (H+)

  • Some H+ are excreted by the kidneys
  • Some H+ shift intracellularly in exchange for potassium

*Most of K inside the cell

*If lots of H+ outside the cell

  • ie DKA
  • H+ exchanged for K
  • fixing acidosis => K goes into cell => animal become hypokalemic

*serum biochem measures extracellular K

42
Q

Internal Potassium Balance

Acid base

A
  • Potassium shifted extracellularly due to acidosis
    • leads to whole body cellular depletion of potassium
    • K+ is excreted by the kidneys when function is normal
      • concurrent metabolic acidosis and hypokalemia = K depletion
43
Q

Internal Potassium Balance

Insulin

A
  • Insulin-dependant potassium glucose symporter
    • presence of glucose stimulates insulin secretion

*First step for hyperkalemic animal

  • Give calcium gluconate
    • stabilizes cardiac myocytes

*Step 2 for hyperkalemic animal

  • Hook up to ECG

*Step 3 for hyperkalemic animal

  • give glucose then insulin
    • drives K into the cell
44
Q

Hyperkalemia will cause

A
  • bradycardia => arrhythmias => cardiac arrest => death
45
Q

Internal Potassium Balance

and diabetes

A
  • Can’t trust chem values in diabetic animals
  • Diabetics may be
    • hyperkalemic
    • normokalemic
    • hypokalemic

​​*With diabetics will measure electrolytes every couple of hours

46
Q

Insulin deficiency

or

peripheral tissue resistance

A
  • Glucose spills into urine when renal threshold exceeded
  • K+ removed from blood by kidneys if function is normal
    • a diabetic may be normokalemic
47
Q

Insulin

A
  • drives potassium and glucose into cells
    • Potassium needs glucose to go inside the cell
    • Won’t work if you’re insulin resistant
  • treatment of life-threatening hyperkalemia
    • insulin and dextrose
48
Q

Potassium abnormal concentration

Hyperkalemia

A
  • Altered external balance
    • failure to exrete
  • Altered internal balance
    • leakage from damaged cells
    • shift form ICF to ECF
  • Spurious
49
Q

Potassium abnormal concentration

Hypokalemia

A
  • Altered external balance
    • inc loss (GI, renal)
    • dec intake
  • Altered internal balance
    • shift from ECF to ICF
  • Spurious
50
Q

Hyperkalemia (Common)

Altered external balance

A
  • Altered external balance
    • failure of renal exretion
      • ​oliguric/anuric renal failure
      • urinary tract rupture
      • urethral obstruction
    • ​Hypoadrenocorticism (addison’s)
    • Chylothorax w/repeated drainage
    • Iatrogenic
      • excessive IF fluid potassium
      • drugs that dec renal excretion
51
Q

Hyperkalemia (Common)

Altered internal balance

A
  • cell membrane damage
    • muscle necrosis
    • acute tumor lysis
  • Inorganic metabolic acidosis (rare cause)
    • organic acidosis (common)
      • K+ shifts out of cells but kidneys excrete
  • Diabetes mellitus
    • insulin deficiency or tissue resistance
52
Q

Spurious Potassium Measurement

Sample issues

A
  • Sample issues
    • Hemolysis w/K+-rich RBCs or traumatic blood draw
      • Japanese dog breeds
      • horses
      • pigs
      • primates
    • Thrombocytosis (>1 million/microL)
      • with cushings (macs don’t eat old platelets)
      • Potassium released during clotting
      • Use heparinized plasma sample to avoid clot
    • Contamination with potassium containing IV fluid
    • Dry method with severe hypernatremia
53
Q

Spurious potassium measurement

Methodology issues

A
  • Methodology issues
    • rarely occurs
    • similar to pseudohyponatremia
      • lipemia
      • severe hyperproteinemia
      • diluted sample method
54
Q

Hypokalemia (common)

Altered external balance

A
  • GI loss
    • vomiting
    • diarrhea
    • abomasal disorder
    • whipworm dz (pseudoaddisons)
  • Inc renal exretion
    • polyuric renal failure (~30% cats with CRF; 10% dogs with CRF)
    • Postobstructive diuresis
    • Diabetic ketoacidosis (DKA) = diabetes mellitus with ketoacidosis
  • Dec intake
    • usually exacerbates GI or renal loss
  • Iatrogenic
    • drugs that increase renal excretion (Furosemide)
    • K poor IV fluid

*Usually markred whole body cellular depletion

55
Q

Hypokalemia (Common)

Altered internal balance

A
  • Altered internal balance (potassium shifts intracellularly)
    • Metabolic alkalosis (uncommon)
    • Iatrogenic
      • bicarbonate administration
        • tx for acidosis/hyperkalemia
      • glucose + insulin therapy
        • tx for DKA; hyperkalemia
56
Q

Hypokalemia

Clinical Signs

Dz examples

A
  • depends on severity and rate of development
  • due to
    • medullary washout: PU/PD
    • abnormal membrane electrical potential
      • skeletal muscle weakness
      • respiratory arrest
      • cats:
        • neck ventroflexion
        • nephropathy
        • polymyopathy
      • ECG changes
      • arrhythmias
  • Dz examples
    • during tx of male cat urethral obstruction (diuresis)
    • during tx of DKA (shifts into cells)
57
Q

Sodium : Potassium ratio

A
  • < 27 suggestive of hypoadrenocorticism
    • < 19 highly suggestive
  • Other dz may have a low ratio
    • renal dz
    • severe diarrhea (salmonellosis, whipworms)
    • repeated chylothorax drainage
    • others
  • Test useful to help detect underlying Addison’s
    • try to exclue other dz based on other findings
    • confirm Addisons with ACTH stimulation test
58
Q

Chloride

Functions

Concentration affected by

Selective chloride changes

A
  • Functions
    • major extracellular fluid anion
    • component of many secretions
  • Concentration affected by
    • NaCl related changes
      • Cl moves with Na
  • Selective Cl changes
    • loss of chloride-rich, sodium poor secretions
      • gastric HCl
    • Cl conc varies inversly with bicarb con
      • to maintain electroneutrality
      • when bicarb is lost Cl increases
        • GI or renal
59
Q

Chloride

Measurement

test question

A
  • Measurement
    • reflects body chloride content
      • extracellular electrolyte
    • Interpret in light of hydration status
    • Other halides crossreact, and detected as chloride
      • ​Epileptics treated with KBr have spurious Cl inc
60
Q

Chloride abnormal concentration

Hyperchloremia

A

Hyperchloremia

  • Na related increases
  • Compensation for dec bicarbonate
  • Iatrogenic
  • Spurious
61
Q

Chloride abnormal concentration

Hypochloremia

A
  • Hypochloremia
    • Na related decreases
    • Loss of Cl rich secretions
    • Iatrogenic
    • Spurious
62
Q

Hypochloremia

Cl rich gastric secretions not resorbed

A
  • Most Chloride made in stomach….?
    • Chloride rich gastric secretions (HCl) not resorbed
      • Ruminants
        • abomasal dz
        • High GI obstruction
      • Monogastrics
        • severe vomiting
        • High GI obstruction
        • NG tube suctioning
63
Q

Hypochloremic metabolic alkalosis with paradoxical aciduria

TEST QUESTION

NAVLE

A
  • Upper GI dz (usually LDA)
    • dehydration (not drinking)
    • hypokalemia (not eating)
    • loss of HCl (Cl sequestered in stomach)
      • leads to metabolic alkalosis
  • The deydration leads to
    • RAAS activation => Cl resorption & K excretion
  • The loss of HCL leads to
    • metabolic alkalosis => alkaline urine

* sequestered Cl=> resorption of bicarb instead of Cl => paradoxical acid urine

*hypokalemia => can’t exrete K => H+ excretion which exacerbates whole sitiation

64
Q

Bicarbonate (TCO2)

A
  • Measurement
    • serum total CO2 about equal to bicarb conc
    • Conc also can be calculated by point of care blood gas machines
  • Conc affected by
    • Renal prod & conservation of HCO3
    • Acid base balance
65
Q

Bicarb to Carbonic acid

A

Maintain a 20 : 1 ratio

Bicarb: main metabolic base

Carbonic acid: main respiratory acid