Electrolytes Part 2 (Magnesium & Bicarbonate) Flashcards
Intracellular cation
MAGNESIUM
2nd most abundant cation in the CELL
MAGNESIUM
What is the 1st abundant cation in the CELL
Potassium
4th most abundant cation
MAGNESIUM
Rank Na, K, Ca, and Mg based on their abundance as a cation
1st - ____
2nd - ___
3rd - ___
4th - ____
1st - Na+
2nd - Ca2+
3rd - K+
4th - Mg2+
How many magnesium are distributed in the bones?
53%
How many magnesium are distributed in the muscles?
46%
How many magnesium are distributed in the serum and RBC?
1%
What are the Functions of Magnesium
-Maintenance of DNA, RNA, and Ribosomes structures
-CHO, CHONs and Lipid synthesis
-Neuromuscular transmission
-Enzyme cofactor (Activator)
-Regulated movement of K+ across myocardium
Reference values of Magnesium
1.26-2.10 mg/dL
What are the three forms of magnesium
- Free Mg2+ (Ionized form)
- Protein-bound Mg2+
- Ion-complexed Mg2+
Free Mg2+ form
Ionized form
Free Mg2+ (Ionized form) %?
55%
physiologically active form of magnesium
Free Mg2+ (Ionized form)
Protein-bound Mg2+ %?
30%
Example of Protein-bound Mg2+
Albumin
Ion-complexed Mg2+ %?
15%
Example of Ion-complexed Mg2+
PO4- , citrate
Three regulators of Magnesium
- Kidneys
- Parathyroid Hormone
- Aldosterone and Thyroxine (T4)
principal regulator of magnesium
kidney
Renal Threshold in kidney (Mg)
0.60-0.85 mmol/L
reabsorbs 25-30% of filtered ionized Mg2+
PCT
PCT reabsorbs ___ of filtered ionized Mg2+
25-30%
reabsorbs 50-60% of filtered Mg2+
Ascending Loop of Henle
Ascending Loop of Henle reabsorbs ____ of filtered Mg2+
50-60%
reabsorbs 2-5% of filtered Mg2+
DCT
DCT reabsorbs ___ of filtered Mg2
2-5%
↑Mg2+ by increasing renal and intestinal reabsorption of Mg2+
Parathyroid Hormone
↓Mg2+ by increasing renal excretion of Mg2+
Aldosterone and Thyroxine (T4)
↓plasma Mg2+
HYPOMAGNESEMIA
Causes of hypomagnesemia
-Diarrhea and Pancreatitis
-Malabsorption
-Hyperparathyroidism
-Renal Loss
-Diabetes Mellitus
-Malnutrition
T/F: PTH causes excretion of Mg2+
T; PTH = ↑Ca2+ = causes excretion of Mg2+
↑plasma Mg2+
HYPERMAGNESEMIA
less frequent than hypomagnesemia
HYPERMAGNESEMIA
Causes of hypermagnesemia
Renal Failure
Antacids
Dehydration
Bone Cancer
Endocrine Disorder
Addison’s Disease
most common cause of HYPERMAGNESEMIA
Renal Failure
Specimen used in magnesium
Serum
Heparinized Plasma (Lithium heparin)
Urine
In magnesium, when using ____ as a specimen, it must be ____ with _____ to prevent ____ of Mg2+
Urine
acidified
Hydrochloric acid (HCl)
ppt
Variables in Mg
Hemolysis
Anticoagulants
T/F Hemolysis causes false decrease in Mg
F; false increase
Example of Anticoagulants that are considered variable in Mg
EDTA, oxalates, citrates
Why anticoagulants EDTA, oxalates, citrates considered as variables?
bec they bind Mg2+ causing false decrease
3 lab methods under Mg
Colorimetric Method
Dye-Lake Method
Atomic Absorption Spectrophotometry
4 examples of colorimetric method in Mg
Calmagite Method
Formazan Dye Method
Methylthymol Blue Method
O-cresolphthalein complexone
(+) reddish-violet complex (532 nm)
Calmagite Method
Calmagite Method forms what complex and measured at what wavelength
(+) reddish-violet complex
532 nm)
(+) blue-colored complex
Formazan Dye Method
formazan Dye Method complex and wavelegth
(+) blue-colored complex (660 nm)
(+) colored complex
Methylthymol Blue Method
Methylthymol Blue Method complex and wavelength
(+) colored complex (600 nm)
also used for calcium measurement
O-cresolphthalein complexone
O-cresolphthalein complexone measured at what wavelength
570 nm
Uses Titan Yellow Dye
Dye-Lake Method
Dye-Lake Method aka
Clayton Yellow or Thiazole Yellow
Dye-Lake Method: end product and wavelength
Yellow-colored complex
(570-590 nm)
2nd most abundant anion in the ECF or plasma
BICARBONATE
Function of Bicarbonate
-major component of blood buffering system (Bicarbonate-Carbonic Acid Buffer)
-90% of total CO2 in the blood at physiologic pH
-Buffers excess hydrogen ion by combining with acid
BICARBONATE FUNX
____ of total CO2 in the blood at physiologic pH
90%
When bicarbonate reach the ___ it will be split into ___ and ___ and will be eliminated by ____
LUNGS
H,O
CO2
EXHALING
Reference Values of bicarbonate
23-29 mmol/L (venous serum/plasma)
REGULATIONS:
Kidney
____: 85% HCO3- ____
DCT: _____ HCO3- _____
PCT; reabsorbed
15%; reabsorbed
REGULATIONS:
Kidney
PCT: ____ HCO3- reabsorbed
DCT: ____ HCO3- reabsorbed
85%
15%
Both PCT and DCT reabsorbs bicarbonate as ____
CO2
pH imbalance
Metabolic Acidosis
Metabolic Alkalosis
decreased plasma bicarbonate
Metabolic Acidosis:
HCO3- combines with H+ in the kidneys to produce CO2 which is exhaled by the lungs
Metabolic Acidosis:
increased plasma bicarbonate
Metabolic Alkalosis:
Usually seen in vomiting (loss of chloride from stomach)
Metabolic Alkalosis:
Specimen used in bicarbonate
Serum
Heparinized plasma
T/F: Specimen should be collected aerobically
F; anaerobically
The sample in Mg must always be capped. To prevent _____
CO2 escape
If sample is left uncapped = ______ in the bicarbonate
6 mmol/L per hour decrease
laboratory methods under bicarbonate
Enzymatic Method
Ion Selective Electrode
T/F The Enzymatic Method in bicarbonate is coupled enzyme
T
2enzymes under enzymatic method in bicarbonate
Phosphoenolpyruvate carboxylase
Malate dehydrogenase
membrane specific to ISE method in bicarbonate
Severinghaus electrode
Formula that doctors use to measure the difference between unmeasured cations and unmeasured anions
ANION GAP (AG)
Calculated by the concentration difference of measured cations (Na+, K+) and measured anions (Cl- , HCO3- )
ANION GAP (AG)
ANION GAP (AG) is Calculated by the concentration difference of measured cations (___, __) and measured anions (___ , ____ )
(Na+, K+)
(Cl- , HCO3- )
Measures increase in one or more unmeasured anions
ANION GAP (AG)
ANION GAP (AG) Measures increase in ___ or ____ unmeasured ___
one
more
anions
Used as quality control measure for analyzer
ANION GAP (AG)
Ref. range when using this formula
AG = Na – (Cl + HCO,)
7-16 mmol/L
Ref. range when using this formula
AG = (Na + K) – (Cl + HCO,)
10-20 mmol/L
What is the formula used if the reference range is
7-16 mmol/L
AG = Na – (Cl + HCO,)
What is the formula used if the reference range is
10-20 mmol/L
AG = (Na + K) – (Cl + HCO,)