Electrolytes

The only physiological active form of calcium is

Ionized calcium

Electrolytes are

Ions capable of carrying an electric charge. Classified as anions and cations based on the charge they carry

Major cation in intracellular fluid

K+ Potassium

Potassium levels are maintained by the ____ it is also absorbed in ____ ______ and filtered at the ______

Kidney Absorbed in small intestine Filtered at the glomerulus

Bicarbonate concentration is regulated by

Kidneys through increased it decreased tubular reabsorption

By product of anaerobic metabolism, not regulated like K or Ca

Lactate or lactic acid

Decreased anion group

Large doses of antibiotics ( such as penicillin) Decreased in anions such as IgG or albumin Increased in serum magnesium calcium Lithium therapy Hemodilution

Hypokalemia

Low potassium <3.5 mmol/L

Use hemolyzed serum or plasma Method of choice : atomic absorption Also : titan yellow , 8- hydroxyquinoline and calcein

Magnesium

Second most abundant ICF 31% is found intracellular and 67% in bone 1-2% in serum

Magnesium 1.5 - 2.5 meq/L

Hepomagnesemia can be caused by

Malabsorption, diarrhea , alcoholism , diuretic therapy Excessive aldosterone production

Determination of osmolality

May be measured in serum or urine

Osmolality

Measure of dissolved particles in solution, major contributors are Na+ and Cl- ( major free particles in ECF ) other contributors are glucose and BUN

Osmol gap

Measured - calculated osmolality

Aldosterone

Mineralocorticoid hormone secreted by adrenal cortex that is important in maintaining electrolyte balance

Hyperphosphatemia is caused by

Most commonly in renal insufficiency Hypoparathyroidism and vitamin D toxicity

Magnesium plays a major role in

Muscle concentration

Major cation in extracellular fluid

Na+ Sodium

In the absence of aldosterone ___ is excreted in urine and ____ is retained. Aldosterone secretion is regulated by the ________

Na+ is excreted K+ and H+ is retained Aldosterone secretion is regulated by the renin-angiotensin system

Anion gap calculation

Na- ( Cl + HCO3 ) n= 8-16 mmol/L ( Na + K ) - ( Cl + HCO3 ) n= 12-20 mmol/L

Anions have ______ charge and and move toward ______

Negative charge Anode

AVP acts on _________ to increase reabsorption of water

Nephron in kidney

Sweat chloride

Nl sweat Cl is <40 mmol/L In cystic fibrosis patients with Cl is 60 - 160 mmol/L >70 is diagnostic Induce patient to sweat by applying current

Phosphorus acts as the principle buffer of

Of the urinary system and factilitates the excretion of H+

Vitamin D deficiency in adults

Osteomalacia

Disease in which bone mass is reduced to level below that required to maintain mechanical support. Rate of bone resorption > bone formation

Osteoporosis

Osteitis deformans, bone disorder characterized by excessive bone resorption due to increased osteoclastic activity. New bone is haphazard and irregular

Paget's disease

Calcium and phosphorus metabolism is regulated by ______. They secrete ______

Parathyroid gland Secrete parathyroid hormone

Metabolism of phosphate is regulated by

Parathyroid glands

Abundant in the body as both intracellular and extracellular ions Intracellularly PO4 exists as organic phosphate in combo with lipids and proteins

Phosphate

Most methods are modifications of fiske and subborrow Principal based on formation of phosphate ions with molybdate Hemolyzed samples are unacceptable

Phosphorus

Cations have a ______ charge and move towards ______

Positive charge Cathode

Osmol gap >10 indicates

Presence of ethanol , methanol , isopropanol, ethylene glycol , or triglycerides or protein in increased concentrations

Chloride shift

The mechanism the body uses for maintenance of normal anion - cation balance as it exchanges with HCO3- bicarbonate

Corrected calcium calculation

Total Ca mg/dL - Alb g/dL + 4.0 1 gram of albumin binds to 0.8 mg Ca

Gastric or diuretic loss

Urine Cl <10 mmol/L

K ISE

Valinomycin membrane , eliminates Na and other ions

Ingestion of too many anti acids or vitamin D Symptoms : weakness , anorexia , nausea , CND involvement , renal stones

Vitamin D toxicity

Less in women than in men due to higher percentage of body fat

Water

Increased anion gap

Ingestion of methanol , ethylene glycol , salicylate Lactic acidosis ( most common ) ketoacidosis Decreased in serum magnesium calcium

Adrenocortical insufficiency due to destruction of adrenal tissue. Is most commonly an autoimmune disease

Addison's disease

Renal excretion thought to be controlled by

Aldosterone

Actions of PTH

- Activates osteoclasts cells of bone , causing resorption with release of calcium and phosphorus to ECF - enhances reabsorption of Ca, in distal tubules , increases serum Ca and decreases urine Ca - inhibits reabsorption of phos by renal tubules , decreased serum phos, increased urine phos

Metabolic bone diseases

- Paget's disease - osteoporosis

Hypophosphatemia can be caused by

- increased renal excretion- primary and secondary hyperparathyroidism - diabetic ketoacidosis recovery phase - vitamin D deficiency - CNS involvement can occur , irritability, seizures , coma - long term may result in rickets and osteomalacia

Calcitonin

- is a peptide hormone secreted form C cells of thyroid gland - acts on bones and kidneys to inhibit osteoclastic bone resorption and tubular reabsorption of Ca - it enhances renal excretion of Ca - decreases serum Ca

Clinical significance of osmolality

- osmolality is the parameter to which hypothalamus responds - regulation of osmolality affects plasma sodium concentration - regulation of sodium and water controls blood volume

Water functions

- transports nutrients to cells - determines cell volume by its transport into and out of cells - removes waste products by way of urine - acts of body's coolant by way of sweating

Electrolytes are an essential component in many processes

- volume and osmotic regulation - myocardial rhythm and contractility - cofactors in enzyme activation - blood coagulation

Increased Ca inhibits _____ Decreased Ca stimulates ______

Inhibits PTH production Stimulates PTH production

Formulas for osmolality in serum

1.86 (Na) + glucose /18 + BUN/ 2.8 + 9 Or 2 (Na) + glucose /20 + BUN / 3

Normal sodium Na+

135 - 148 mmol/L or meq/L

Normal range phosphorus

2.8- 4.0 mg/dL

Osmolality normal serum

275 - 290 osm/ kg

Normal range of potassium

3.5 - 5.3 mmol/L

What is ______ % of human body weight

40 - 75 %

3 forms of calcium

46% protein bound 7% complexed with citrate, phosphate , lactate , or sulfure 47% free or ionized

Albumin accounts for _____ of protein binding, globulins are the other ______

80% 20%

Renal loss

> 10 mmol/L

Water is located in

Intracellular and extracellular fluid

Is a major determinant of renal water excretion and increases water permeability of collecting ducts

Argenine vasopressin hormone AVP or ADH

The posterior pituitary secretes _______ formally called _______ upon stimulation by hypothalamus

Arginine vasopressin hormone ( AVP ) Anti - diuretic hormone ( ADH )

Ion selective electrode ISE

Based on potentiometry, voltage change between reference and indicator electrode proportional to activity of ion being measured

Second largest anion in ECF Major component of TCO2 in plasma

Bicarbonate 22-28 mmol/L

Anion gap

Body exists in electro neutrality where cations = anions Anion gap represents unmeasured anions , proteins , sulfate , etc

Hyperkalemia can be caused by

Breakdown of tissue ( trauma or crushing ) Acidosis ( H moves into cells , increases pH, K moves out ) Acute renal failure - kidneys only way out Hypoaldosteronism Insulin dificiency

Sodium also maintains acid - base balance by

By Na and H exchange at nephron in kidney

Another hormone that helps regulate calcium and phosphorus metabolism is

Calcitonin

An increased serum Ca stimulates release of the _____ A decreased serum Ca inhibits ____

Calcitonin Release

Reference method is atomic absorption Direct spectrophotometric method : metal complexing dye - CPC which forms red complex with calcium in alkaline solutions

Calcium

Most abundant electrolyte in the body 99% is bound in skeleton Calcium is divalent predominantly extracellular ion Only 0.03% is found in plasma

Calcium 8.5 - 10.5 mg/dL

How can hypernatermia occur

From water loss or Na gain, most commonly from vomiting or sweating ( water loss exceeds Na ) Deficiency of AVP secretion

Bicarbonate functions

Functions as a major component of bicarbonate- carbonic acid buffer system , acts as buffering system for changes in blood pH CO2 produced form metabolic processes in tissues and delivered to lungs for exhalation

Hyperkalemia can result in

Cardiac arrest

Hypomagnesemia causes

Cardiac arrhythmias

Major anion in ECF

Chloride 100- 110 mmol/L

Anions include

Chloride Bicarbonate Phosphorus

Buffering system of the blood for acid base balance

Chloride shift HCO3 is pulled out of erythrocytes and Cl moves into erythrocytes , resulting in a decrease in serum Cl

Major extracellular anion

Cl- Chloride

Na ISE

Glass membrane , eliminates Na and other ion

ICF

Intracellular fluid, contained within the cells 66% of total body H2O

In the bone Ca and Phos form

Crystalline structure and hydroxyapatite

Water ______ with age and obesity

Declines

Decreased HCO3 vs increased HCO3

Decreased HCO3 - metabolic acidosis Increased HCO3 - metabolic alkalosis

Chronic renal failure

Decreased calcium , increased phosphorus, increased PTH. Renal disease associated with decreased synthesis of 1,25 (OH)2D3 which leads to hypocalcemia

Hypocalcemia

Decreased calcium in serum < 8.5 mg/dL

Hypophosphatemia

Decreased level of phosphorus < 2.4 mg/dL

Hypomagnesemia

Decreased magnesium

Hypoparathyroidism

Decreased serum calcium , increased phosphorus, decreased PTH, increased urine calcium, decreased urine phosphorus

Hypochloremia

Decreased serum chloride < 100 mmol/L

Vitamin D deficiency

Defective mineralization of bone. Bones become soft , bend easily , and are prone to deformities

Hypokalemia can be caused by

Excess insulin Primary aldosteronism ( CONNs syndrome) enhances renal excretion Diuretics enhances renal flow - most common cause Persistent vomiting, use of laxatives , increases diarrhea Licorice ( acts as aldosterone)

ECF

Extracellular fluid Interstitial fluid - immediately surrounds cells , separated from ICF by cell membrane. Around cells and tissues Intravascular fluid - capillary wall separates from interstitial fluid. Plasma

Chloride is very important in the maintenance of

Fluid balance and osmotic pressure

Important functions of calcium

Formation of bones Muscle contractions Clotting of blood - major involvement in coagulation cascade

Hyperkalemia

High potassium >5.0 mmol/L

High Na sodium

Hypernatremia > 145 mmol/L

90% Increased calcium , phosphorus decreased to normal , increased PTH

Hyperparathyroidism or malignancy

Low sodium

Hyponatremia < 136 mmol/L

If Na increases —-> _____ ——> ______

If Na increases —-> osmolality increases ——> plasma volume increases also

If Na is lost form plasma ——-> _______ ——-> ______ —>

If Na is lost form plasma —-> osmo decreases —-> water flows into cells —-> decreases plasma volume

Where is ADH / AVP synthesized

In the hypothalamus and stored in pituitary from where it is secreted

Urine > 20 mmol/L

Inability to conserve Na

Hypercalcemia

Increased calcium >10.5 mg/dL

Hypermagnesemia

Increased magnesium

Hyperphosphatemia

Increased phosphorus >4.7 mg/dL

Hypochloremia can be caused by

Prolonged vomiting ( loss of HCL ) nasogastric suctions Burns Renal loss : diuretic promotes excretion of Na and Cl metabolic alkalosis

Calcium and phosphorous relationship

Reciprocal relationship Increased calcium decreased phosphorus Decreased calcium increased phosphorus

Hypermagnesemia can be caused by

Renal failure is most common cause Ingesting large amounts of milk of magnesia or antacids that contain magnesium salt

Vitamin D deficiency in children

Rickets

A 1-2 % decrease in osmolality _____

Shuts off AVP production

Cl ISE

Silver chloride sulfide sensing element , chloridometer also uses silver electrode

Cations include

Sodium Potassium Calcium Magnesium

Predominant cation in ECF Function is maintaining normal water distribution and osmotic pressure of plasma

Sodium Na+

Chloride generally follows

Sodium so they will usually increase or decrease in the same conditions

Water is _____ for all processes in human body

Solvent

An increase in osmolality as little as 1% or 2% , stimulates

Stimulates osmo receptors of the hypothalamus which causes thirst and ingestion of water

Symptoms of hypocalcemia

Tetany Painful spasms Chvosteks sign is twitching of muscle of facial nerve

Osmolality lab measurement

The colligative properties of freezing point depression or vapor pressure are used

When using freezing point depression the decrease in the freezing point temperature is proportional to

The number of dissolved particles present

TCO2 ISE

pH change - measured by electrode ( pH electrode )