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Clinical Chemistry > Calcium, Magnesium, Phosphorus > Flashcards

Calcium, Magnesium, Phosphorus Flashcards

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1
Q

Magnesium general (Mg2+)

A

1.26-2.10 mEq/L
intracellular cation : most in bone or tissue
61% is in free form; the rest is bound to protein or complexed to phophate ion etc

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2
Q

Magnesium functions

A

cofactor for >300 enzymes
involved with DNA & RNA mechanisms
important clinically for cardiovascular, metabolic & neuromuscular disorders

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3
Q

Magnesium Regulation

A

GI aborbs 20-65% of diet Mg2+
Mg bound to protein is filtered by kidney & mostly reaborbed in the loop of Henle
hormones like PTH, Aldosterone, & T4

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4
Q

PTH on Mg2+

A

parathyroid hormone has effect on calcium metabolism & will increase absorption of Mg in the GI & Kidneys

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5
Q

Aldosterone on Mg2+

A

aldosterone focuses on conserving Na+ > Mg2+ & will cause a decrease in absorption

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6
Q

Thyroxine on Mg 2+

A

T4 thyroid hormone is active in metabolism and will require elements like iron etc > Mg & cause a decrease in Mg 2+ absorption

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7
Q

Hypomagnesemia

A 
decrease in Mg2+
malabsorption/malnutrition
renal diseases: excess excretion of Mg2+
drugs: diuretics, gentamycin, cisplastin, cyclosporine etc
lactation
endocrine disorders
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8
Q

Hypermagnesemia

A

increase Mg2+
endocrine disorders: hypothyroidism, hypoaldosterone, hypopituitarism
excessive intake
dehydration
renal failure: chronic/acute renal failure: Mg decreased excretion
cardiovascular symptoms

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9
Q

Magnesium analyzer methods: specimen

A

specimen: non-hemolyzed (Mg is intracellular)

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10
Q

Magnesium analyzer -non clinical methods

A

limitations of Assay: protein binding of 25% of Mg & serum may not reflect intracellular concentrations of Mg
Atomic Absorption: reference method, not clinical
hollow cathode lamp - analyte will absorb light & detector detects difference
Lanthanium-HCl diluent: separate analyte of interest away from its bound protein

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11
Q

Magnesium analyzer clinical methods

A

Colorimetric : dyes include calmagite (!), formazen dye, methylthymol blue, & magon
polyvinylpyrrolidine & p-only-phenol are added to remove protein interferences
KOH to make solution alkaline

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12
Q

Calmagite

A

uses EGTA & Cyanide to bind Ca2+ & other metals

Calcium is an interference in colorimetric analyzer method for Magnesium

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13
Q

Calcium general

A 
8.4-10.2 mg/dL
bone calcium- 99%
ionic calcium is the active form: 
neuromuscular- troponin & Ca2+ involved in muscle contraction
blood coagulation
activates some enzymes
cAMP needs Ca2+
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14
Q

Calcium in serum (2 groups)

A

non-diffusible, protein bound calcium - 40% of blood calcium

diffusible, free calcium (ionic)- ionized free calcium & complexes with phophates, bicarbonate, sulfates etc

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15
Q

PTH on Calcium Regulation

A

parathyroid hormone affects bone calcium to enter circulation
increases GI absorption of calcium
makes kidney conserve Ca2+

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16
Q

Vitamin D on calcium regulation

A

Vit D to 25-OH-cholecalciferol in liver is then converted to 1, 25-Dihydroxy-cholecalciferol by kidney enzyme
this then enhances Ca2+ reabsorption from the GI

17
Q

Calcitonin on calcium regulation

A

comes from the C cells of the thyroid
inhibits PTH & Vit D
puts calcium back into the bones

18
Q

Hypocalemia

A

decreased ca2+
hypoparathyroidism (vv ionized ca2+)
hypomagnesium, hypoalbuminemia, pancreatitis, renal disease, etc etc etc
most of these are protein issues & the protein bound Ca would be significantly decreased

19
Q

Hypercalemia

A

increased Ca
hyperparathyroidism
cancers
hyperthyroidism
drugs:
thiazides, diuretics- increase Ca reabsorption from kidney
biphosphanates- lower ca in blood & put it back into bones (menopausal women)

20
Q

Calcium analyzer methods: specimen

A

serum, plasma in lithium heparin ( EDTA binds Ca!)
ionized Ca collected anaerobically
urines-24 hr preserved in 6M HCl

21
Q

Calcium analyzer methods (3)

A

colorimetric: o-cresolphthalein method & Arsenazo III (binds to Ca & read spectro)
atomic absorption- reference method
ion selective electrodes

22
Q

O-cresolphthalein method for calcium analysis

A

dilute HCl, 8-hydroxy quinolone binds to Mg (!), cresolphthalein complex, diethylamin
read at 578 nm

23
Q

Arsenazo III method for calcium analysis

A

pH: 6
[Na+] acts as positive influence to bind Ca to slide
used on slide chemistry methods (Vitros)

24
Q

Phosphorus functions

A

energy source when in ATP, phosphorylates glucose, phospholipids of membranes
> 80% is stored in the bone <1% is in serum

25
Q

Most significant regulator of phosphorus

A

PTH - parathyroid hormone

26
Q

Hypophosphatemia

A

decrease in phosphorus
occurs in 60-80% of ICU patients w/ sepsis
vit D deficiency, Antacids, Hyperparathryoidism

27
Q

Hyperphosphatemia

A 
acute/chronic renal failure
neonates lacking PTH full development
increased cell breakdown- infections, exercise, intra hemolysis
hypoPTH
acromegaly
lymphoblastic leukemia
28
Q

Specimen for Phosphorus testing

A

serum or lithium heparin
avoid hemolysis
FASTING
urine should be 24 hr

29
Q

Fiske Barrow Method for Phosphorus

A

ammonium molybdate reagent - read at 340nm
or
reduce phosphomolybdate complex w/ reducing agents & measure product (blue) at 660mn

30
Q

Parathyroid hormone effect on Ca2+,Mg2+, Phophorus

A

increases calcium & magnesium

decreases phophorus

31
Q

Calcitonin effect on Ca2+ & phosphorus

A

decreases both Ca2+ & phosphorus in serum

32
Q

Vitamin D effect on Ca, phosphorus

A

enhances Ca & Phos absorption & retention

leads to increase

33
Q

Lactate

A

byproduct of anaerobic metabolism
liver processes lactate into glucose via gluconeogenesis
measure clinically in critically ill patients: type A & type B

34
Q

lactate clinical measurements Type A

A

hypoxic conditions like shock, MI, severe CHF, pulmonary edema or severe blood loss

35
Q

lactate clinical measurements Type B

A

metabolic in origin

see in DM, severe infections, leukemia, liver or kidney disease, toxins

36
Q

Lactate specimen

A

NO TOURNIQUET
keep specimen on ice
use heparin

37
Q

Lactate enzymatic method

A

substrate: lactate
enzymes: lactate oxidase, peroxidase
read: colored product

Clinical Chemistry (23 decks)

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