CC - Electrolytes & Osmolality

osmolality

measure of number of dissolved particles in solution; expressed as mOsm/kg

colligative properties

properties of sol’n that are influenced by number of molecules in solution affected by concentration

acidosis

<15 osmolal gap =

electroneutrality

define capability of fluid to contain equal number of cation & anions

sodium (Na+)

also natrium; major cation of ECF; principal osmotic particle outside cell

sodium (Na+)

plasma concentration depends on intake & excretion of water; all confirmed abnormalities are followed by urinalysis

1. aldosterone

2. atrial natriuretic factor

hormones affecting sodium (Na+):

aldosterone

promotes reabsorption of Na+; Na+ retention, K+ excretion

atrial natriuretic factor (ANF)

endogenous antihypertensive secreted from cardiac atria

atrial natriuretic factor (ANF)

blocks aldosterone and renin secretion; inhibits action of angiotensin II and vasopressin

hypernatremia

could lead to coma; usually from excessive water loss

thirst

major defense against hyperosmolality & hypernatremia

hyponatremia

most common electrolyte disorder; in renal failure

pseudohyponatremia

most common cause is in vitro hemolysis

bartter’s syndrome

defect in loop of henle NaCl transporter

potassium (K+)

aka kalium; cotransporter of Glu

potassium (K+)

major intracellular cation; single most important cation in terms of abnormality being immediately life threatening

potassium (K+)

cardiac ion that affects cardiac muscle contraction

reduced aldosterone

most common cause of chronic hyperkalemia

hyporeninemic hypoaldosteronism

most common cause of all aldosterone def states; most common cause of chronic hyperkalemia in dialysis px

hyperkalemia

low resting membrane potential (RMP); can cause lack of muscle excitability

hypokalemia

increases cell excitability by increasing RMP; results in arrhythmia and paralysis

chloride (Cl-)

major extracellular anion; maintenance of water balance & osmotic pressure

chloride (Cl-)

only anion to serve as enzyme activator (AMS); disorders same w/ Na

calcium

present almost exclusively in plasma; 50% is unbound/free

1,25-dihydroxycholecalciferol (1,25-(OH)2-D4)

activated vit D3

1,25-dihydroxycholecalciferol (1,25-(OH)2-D4)

increases intestinal and kidney reabsorption of Ca; increases Ca mobilization in bones

parathyroid hormone

conserves Ca; increases reabsorption in kidney; increases Ca mobilization, activates bone resoprtion

parathyroid hormone

suppresses urinary loss of Ca; stimulates conversion of Vit D3 form inactive to active in kidneys

calcitonin

TH; inhibits PTH and Vit D3; hypocalcemic hormone

calcitonin

inhibits bone resorption; promotes urinary excretion of Ca

inorganic phosphorous

omnipresent; 85% in bones, 15% in ECF

inorganic phosphorous

inversely related to Ca; maximally absorbed in jejunum

phosphate

essential for insulin-mediate entry of Glu into cells by phosphorylation of Glu & co-entry of K

PTH

decreases phosphate by renal excretion

growth hormone

increases phosphate renal absorption

magnesium (Mg+)

intracellular cation; 2nd in abundance to K+; 4th most abund

magnesium (Mg+)

vasodilator; cause decrease uterine hyperactivity in eclampsic states and increase uterine blood flow

PTH

increases renal & intestinal absorption of Mg

aldosterone & thyroxine

increases renal excretion of Mg

bicarbonate (HCO3-)

2nd most abundant anion in ECF; accounts for 90% of total CO2

bicarbonate (HCO3-)

major component of buffering system; diffuses out of cell in exchange for Cl

anion gap

difference b/w unmeasured cations and unmeasured anions; form of QC for electrolyte analyses

cystic fibrosis

inherited disorder of exocrine glands producing abnormally thick secretions of mucus, elevation of sweat electrolytes, increased organic & enzymatic constituent of saliva, over activity of autonomic NS

iron

for synthesis of Hgb; prooxidant, contributes to lipd peroxidation, atherosclerosis, DNA damage & carcinogens

ferritin

stored iron

total iron binding capacity (TIBC)

amount of iron that could be bound by saturating transferring

total iron binding capacity (TIBC)

direct measure of total # of functional ferrous ion-binding sites in transferrin

unsaturated iron binding capacity (UIBC)

measure of reserve iron binding capacity of transferrin

percent saturation

also transferrin saturation; index of iron storage

transferrin

principal iron transport protein

buffer system

system that resist change in pH

bicarbonate-carbonic acid buffer system

uses HCO3 and H2CO3 to minimize pH changes in plasma and RBC; major extracellular blood buffer

protein buffer system

uses plasma proteins to minimize pH changes in blood; buffering capacity through charges on surface

phosphate buffer system

uses HPO4 and H2PO4 to minimize pH changes in plasma and RBC

hemoglobin buffer system

uses Hgb to minimize pH changes in blood; most important intracellular buffer

partial pressure

amount of pressure contributed by each gas to total pressure exerted by mixture

acidemia

when arterial blood is <7.35

alkalemia

when art. blood is >7.45

hypercapnia

increased blood pCO2

hypocapnia

decreased blood pCO2

henderson-hasselbach equation

expresses acid-base relationship and relates pH of sol’n to dissociation properties of weak acid

henderson-hasselbach equation

indicates that pH depends on ratio of HCO3:pCO2

<35 mmHg

pCO2 for respiratory alkalosis

>45 mmHg

pCO2 for respiratory acidosis

pCO2

index of efficiency of gas exchange

metabolic acidosis

d/t bicarbonate def; electrolyte imbalance: hyperkalemia and hyperchloremia

metabolic alkalosis

caused by bicarbonate excess

respiratory acidosis

d/t excessive CO2 accumulation

respiratory alkalosis

d/t CO2 loss

mixed acid base disorders

refers to clinical condition in which 2 or more primary acid-base disorders coexist