SODIUM AND POTASSIUM Flashcards
are essential components of all living matter
Electrolytes
Include major electrolytes:
Na+, K+, Ca+2, Mg+2, Cl-, HCO3-,
HPO4-2, SO4-2, Proteins, Lactate, Trace metals
The major electrolytes occur primarily as (?) whose properties are unaffected by other ions or molecules.
free ions
The trace metals occur primarily in combination with
proteins
- Maintenance of osmotic pressure & water distribution in the various body fluid compartments (?)
Na+, K+, Cl-
- Maintenance of the proper pH/acid-base balance (?)
HCO3- , K+, Cl-
- Regulation of the proper function of the heart and other muscles (?)
K+, Ca+2, Mg+2
- Involved in
oxidation-reduction reactions or electron transfer reaction
- Participation in catalysis as cofactors for enzymes (?)
Mg+2, Ca+2, Zn+2
- Some electrolytes are even involved in
blood coagulation
is the major cation of ECF
Sodium
It represents about 90% of extracellular cations
Sodium
plays a central role in maintaining the normal H2O distribution and the osmolality of plasma.
Sodium
Na Reference range:
136 – 145 mmol/L
Sodium can be excreted in urine when the renal serum threshold
of sodium exceeds
110–130 mmol/L
This is the major intracellular cation
Potassium
Only 2% is found in the plasma
K
is 20x greater inside of the cell
K conc
Tissue cells (?)
average of 150mmol/L
RBC (?)
105 mmo/L
Sodium is initially filtered by the
glomeruli
About (?)of sodium filtered is reabsorbed in the proximal convoluted tubules along with bicarbonate and water.
60 to 70%
About (?) is reabsorbed in the loop of Henle with chloride and more water.
25-30%
While reabsorption in the distal convoluted tubules is controlled
by (?), a hormone that conserves sodium.
aldosterone
“Coupled System with the Sodium-Potassium Sodium-Hydrogen Exchange”
Sodium
Like sodium, (?) is also the most important organ in the regulation and handling of potassium.
kidney
Potassium once filtered by the glomerulus if almost completely reabsorbed in the (?).
proximal convoluted tubules
Under the influence of aldosterone, potassium is secreted in the (?) hence the distal nephron is the principal determinant of urinary potassium excretion.
distal tubules and collecting duct
The renal threshold of sodium is between (?)
110–130 mmol/L
are the ultimate regulators of the amount of Na+ or K+ in the body
kidneys
The following are the normal value for sodium:
o Serum/Plasma :
o Urine (24 hr) :(varies w/ diet)
o CSF :
136 – 145 mmol/L
40 – 220 mmol/L
136 – 150 mmol/L
The following are the normal value for K:
Serum of adults:
Plasma:
Newborn:
CSF:
Urine: (varies w/ dietary intake)
3.5 – 5.0 mmol/L
3.5 – 4.5 mmol/L
3.7 – 5.9 mmol/L
~70% of values in serum
25 – 125 mmol/L
IMPORTANCE OF WATER
(?) for all processes
Transport (?) to the cells
Determines (?)
Removes (?) (by way of urine)
Serves as a (?) (by way of sweating/perspiration)
(?)
(?)
Solvent
nutrients
cell volume
waste products
coolant
Active Transport
Diffusion
Accounts for 2/3 of total body water
INTRACELLULAR FLUID
aka PLASMA
Intravascular ECF
Normal Plasma
93%
Remaining are
H2O
lipids and proteins
Fluid that surround the cells in tissues
Interstitial fluid
Requires energy from atp
Active Transport
Maintenance of electrolyte balance
Active Transport
Passive movement of ion across membrane
Diffusion
Size, and charge of ions
Diffusion
SODIUM
intake of H2O (polydipsia)
plasma osmolality
Arginine vasopressin (AVP/ADH) (thirst are suppressed)
↑
↓
↓
in the absence of (?), water is not reabsorbed causing large volume of
diluted urine to be excreted
AVP
(affected by AVP release)
Excretion of H2O
, which affects Na+ excretion
Blood volume status
water = plasma osmolality (Both AVP & thirst are activated)
↓ ↑
AVP contributes by minimizing renal water loss although thirst is major defense against
hyper osmolality and hypernatremia
is important to maintain pressure and ensure good perfusion to all tissues and organs.
Adequate blood volume
RAAS responds primarily to a
decreased blood volume
Renin is secreted in response to
decrease blood flow
(?) converts (?) to (?) w/c will become angiotensin II that causes vasoconstriction which (?)
Renin (liver), angiotensinogen (kidney), angiotensin I (lungs); increased blood pressure and secretion of aldosterone
increases Na and H2O retention)
aldosterone
peptide released form the myocardial atria in response to volume expansion, promotes Na excretion in the kidney
Atrial natriuretic peptide
most common electrolyte disorders (esp on hospitalized px) which happen when plasma sodium levels go down to < 135 mmol/L
Hyponatremia
Hyponatremia
INCREASED NA+ LOSS
Diuretic use, prolonged vomiting and diarrhea, severe burns
INCREASED H2O RETENTION
Renal failure (dilution of water)
Congestive Heart Failure
H2O imbalance: excess water intake (polydipsia)
absolute losses of total body sodium
DEPLETIONAL
DEPLETIONAL
Renal losses
Non-renal losses
Salt losing enteropathies
Excessive sweating
due to an increase in water volume
DILUTIONAL
DILUTIONAL
SIADH
Generalized edema
Generalized edema
CHF
Cirrhosis
nephrotic syndrome
Hyperglycemia
excessive water retention (hence dilution of salt will occur)
syndrome of inappropriate ADH production
Renal losses
diminished tubular reabsorption (PCT, DCT, sodium)
renal tubular acidosis (tubular transport of electrolytes)
Non-renal losses
GIT loss through diarrhea and vomiting
due to analytical errors
ARTIFACTUAL / pseudo hyponatremia
occur when sodium is measured using ion selective electrodes in patients who have hyperproteinemia and hyperlipidemia
ARTIFACTUAL / pseudo hyponatremia
less common abnormality
Hypernatremia
Excess water loss
D. Insipidus
Profuse Sweating
Increased Na+ Intake Or Retention
Hyperaldosteronism
Excess Dialysis Fluid
True among Infants, Older Persons, Mental Impairment
Decreased water intake
– AVP response/production impairment
D. Insipidus
– impaired AVP secretion; water not reabsorbed
Central DI
– impaired kidney function
Nephrogenic DI
: 60 - 75% Mortality
160 mmol/L
due to a lesion/trauma in the brain; w/o the feeling of thirst
Adypsia
Water loss
Gastrointestinal losses: vomiting, diarrhea
Excessive sweating: fever, exercise
Diabetes insipidus: hypothalamic (central) & nephrogenic
Sodium gain
Ingestion / Infusion of salt
Hyperaldosteronism
Primary (Conn’s disease)
SPECIMEN for Na+:
Serum, heparinized plasma, sweat, 24-hour urine, liquid feces or GIT fluids (timed collection – 24 hrs)
For delayed Na analysis:
serum, plasma or urine stored at ref T or frozen
Specimen for Potassium
Serum & plasma
Plasma K+ < serum
Plasma - specimen of choice
Whole blood samples
K Increased levels
Plasma or serum is not promptly separated from cells
Whole blood is chilled prior to separation
Extreme thrombocytosis or Leucocytosis
Muscle activity (10-20%)
Ion selective electrode
Sodium uses
glass ion exchange membrane
Na Spectrophotometric
Enzyme:
Substrate:
Product:
B-galactosidase
O-nitrophenyl-B-d- galactopyranoside (ONGP)
O-nitrophenol
Enzyme activation (kinetic)
Spectrophotometric method
K Spectrophotometric method
Enzyme:
tryptophanase
Ion selective electrode
Potassium used
liquid ion exchange membrane with valinomycin
most routinely used method which makes use of reference electrodes and measuring electrodes
Ion selective electrode
2 TYPES OF ISE MEASUREMENT
- Direct - undiluted sample; more accurate
- Indirect - a diluted sample
ERRORS IN ISE
- Lack of selectivity
- “electrolyte exclusion effect”
– caused by protein build- up on membrane
Lack of selectivity
– applies to indirect method
“electrolyte exclusion effect”
Decreased amount of potassium
Hypokalemia
Increased Cellular uptake
- Alkalosis and Alkalemia
- Insulin overdose
promotes intracellular loss of H (H inside the cell is being released outside); both K and Na enters cell to promote electronutrality.
Alkalemia
increase promotes cellular uptake of K
Insulin
Renal losses
- Diuretics
- Nephritis
- Renal Tubular Acidosis
- Hyperaldosteronism
- Cushing’s Syndrome
- Hypomagnesemia
- Acute Leukemia
may lead to tubular excretion of H (tubules lacks H that makes it acidic)
RTA
aldosterone promotes retention of Na and loss of K
Hyperaldosteronism
excess of cortisol, which may bind to Na-K ATPase pump and acts like aldosterone
Cushing’s Syndrome
– may diminish the activity of Na-K ATPase pump and enhance secretion of aldosterone
Hypomagnesemia
Acute Leukemia - Renal K loss also occur in
acute myelogenous leukemia and acute lymphocytic leukemia
Excessive GIT losses
- Vomiting
- Diarrhea
- Gastric suction
- Intestinal tumor
- Malabsorption
- Cancer therapy
- Large doses of laxatives
Elevated concentration of potassium
Hyperkalemia
Increased intake
K replacement therapy
The most common cause of hyperkalemia is due to (?) and the risk is greatest with IV K replacement seen in dialysis patient
therapeutic K administration
Cellular shift
- Acidosis
- Muscle/cellular injury
- Chemotherapy; Leukemia
- Hemolysis
Decreased renal excretion
- Acute or chronic renal failure
- Hypoaldosteronism; Addison’s
- Diuretics
Artifactual causes
- Sample hemolysis
- Thrombocytosis
- Prolonged tourniquet use or excessive fist clenching
