Electrolytes and Acid- Base Disorders Flashcards
what would indicate that a patient may have respiratory acidosis and not metabolic?
The pH is low and the PCO2 is high; but bicarb is normal. In metabolic, the low pH would be met with an also lower HCO3-.
what is the normal pH range for blood?
7.34 to 7.45
normal PCO2 range
35 - 45 mmHg
normal HCO3- range
22 - 29 mmol/L, or mEq/L
pO2 normal range
85 - 105 mmol/L
A patient has: high pH of 7.5, PCO2 of 40, HCO3- of 85…..what acid-base disorder matches?
metabolic alkalosis
give reference range avgs for : Na, K, Cl, HCO3/CO2
Na+: 135-145 mmol/L
K+: 3.5 - 5 mmol/L
Cl-: 95 to 105 mmol/L
HCO3-: (measured as total CO2 bc it’s more practical) 22 to 29 mmol/L
some causes of anion gap increase
DKA, lactic acidosis, hypernatremia, uremia (when kidney is failing and nitrogenous products are accumulating and causing symptoms such as depression, hypothermia and anorexia)
toxins: methanol, ethylene glycol, salicylate
which major anion of the serum is the largest fraction?
chloride
what of the 3 forms of calcium in serum is biologically active?
the free ionized form (versus protein or anion bound)
what regulates serum calcium? 3 major controllers
parathyroid hormone, Vit D, and calcitonin
what are the major effects of PTH in the two main organs it operates upon?
In bone, it activates osteoclasts to release needed calcium; in kidneys it increases tubular reabsorption of Ca and stimulates vit D to its active form
describe in simple terms the path of vitamin D in 3 steps to its active form
It is obtained through either diet or sunlight; It first goes to the liver and is hydroxylated; this form is then sent to the kidneys where it is converted to the active 1,25-dihydroxycholecalciferol
what role does vitamin D play in calcium absorption?
it enhances it in the intestines
where is calcitonin made and what is its role
made in the thyroid parafollicular cells when serum calcium increases; it inhibits vitamin D and PTH to decrease serum Ca++
how would hyperparathyroidism affect serum calcium levels?
It would cause hypercalcemia, too much in the blood;
why would kidney disease affect bone health?
because this is where the active form of vitamin D is formed and also where PTH causes increased reabsorption of calcium when it is needed
what kind of anticoagulant is allowed for serum Ca?
SST or lithium heparin;
Spectrophotometric analysis of Calcium uses what dye?
ortho-cresophthalein (or arsenazo III) –> forms violet color to read intensity
how is serum phosphorus regulated?
by kidneys: PTH causes renal EXCRETION and vit D causes renal REABSORPTION as well as intestinal absorption
specimen tube for phosphorus analysis?
serum separator or heparin (no EDTA, citrate or oxalate, just like calcium!)
Like calcium, the free form of magnesium is the active form; how is the level regulated?
by the kidneys through reabsorption and excretion; PTH enhances reabsorption
What is osmolality? what is the reference range of serum osmolality?
The measure of the number of dissolved particles in solution expressed as osmoles per kilo
275- 295 mOsm/Kg
what gland regulates osmolality and how?
the hypothalamus, through signaling thirst and signaling posterpit to secrete ADH (causing renal reabsorption of water and Na)
give the simplified formula for estimating osmolality
2(Na) + glucose/20 + BUN/3 = mOsm/Kg
what should the osmolal gap be less than? Why would it be higher?
< 15; variety of reasons including excess BHB, toxin ingestion like ethylene glycol or too much alcohol
what IS the osmolal gap?
the diff btw calculated and measured osmolality; should be equal in health
what is the avg normal ratio of HCO3 to dissolved carbon dioxide in the blood (also seen expressed as the carbonic acid portion); Why is this important?
20:1
Having a high ratio of HCO3- gives the blood plenty of buffering capability to handle increases in acidity
