Electrolytes and Acid- Base Disorders

Question 1

what would indicate that a patient may have respiratory acidosis and not metabolic?

Answer 1

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-.

Question 2

what is the normal pH range for blood?

Answer 2

7.34 to 7.45

Question 3

normal PCO2 range

Answer 3

35 - 45 mmHg

Question 4

normal HCO3- range

Answer 4

22 - 29 mmol/L, or mEq/L

Question 5

pO2 normal range

Answer 5

85 - 105 mmol/L

Question 6

A patient has: high pH of 7.5, PCO2 of 40, HCO3- of 85…..what acid-base disorder matches?

Answer 6

metabolic alkalosis

Question 7

give reference range avgs for : Na, K, Cl, HCO3/CO2

Answer 7

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

Question 8

some causes of anion gap increase

Answer 8

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

Question 9

which major anion of the serum is the largest fraction?

Answer 9

chloride

Question 10

what of the 3 forms of calcium in serum is biologically active?

Answer 10

the free ionized form (versus protein or anion bound)

Question 11

what regulates serum calcium? 3 major controllers

Answer 11

parathyroid hormone, Vit D, and calcitonin

Question 12

what are the major effects of PTH in the two main organs it operates upon?

Answer 12

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

Question 13

describe in simple terms the path of vitamin D in 3 steps to its active form

Answer 13

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

Question 14

what role does vitamin D play in calcium absorption?

Answer 14

it enhances it in the intestines

Question 15

where is calcitonin made and what is its role

Answer 15

made in the thyroid parafollicular cells when serum calcium increases; it inhibits vitamin D and PTH to decrease serum Ca++

Question 16

how would hyperparathyroidism affect serum calcium levels?

Answer 16

It would cause hypercalcemia, too much in the blood;

Question 17

why would kidney disease affect bone health?

Answer 17

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

Question 18

what kind of anticoagulant is allowed for serum Ca?

Answer 18

SST or lithium heparin;

Question 19

Spectrophotometric analysis of Calcium uses what dye?

Answer 19

ortho-cresophthalein (or arsenazo III) –> forms violet color to read intensity

Question 20

how is serum phosphorus regulated?

Answer 20

by kidneys: PTH causes renal EXCRETION and vit D causes renal REABSORPTION as well as intestinal absorption

Question 21

specimen tube for phosphorus analysis?

Answer 21

serum separator or heparin (no EDTA, citrate or oxalate, just like calcium!)

Question 22

Like calcium, the free form of magnesium is the active form; how is the level regulated?

Answer 22

by the kidneys through reabsorption and excretion; PTH enhances reabsorption

Question 23

What is osmolality? what is the reference range of serum osmolality?

Answer 23

The measure of the number of dissolved particles in solution expressed as osmoles per kilo
275- 295 mOsm/Kg

Question 24

what gland regulates osmolality and how?

Answer 24

the hypothalamus, through signaling thirst and signaling posterpit to secrete ADH (causing renal reabsorption of water and Na)

Question 25

give the simplified formula for estimating osmolality

Answer 25

2(Na) + glucose/20 + BUN/3 = mOsm/Kg

Question 26

what should the osmolal gap be less than? Why would it be higher?

Answer 26

< 15; variety of reasons including excess BHB, toxin ingestion like ethylene glycol or too much alcohol

Question 27

what IS the osmolal gap?

Answer 27

the diff btw calculated and measured osmolality; should be equal in health

Question 28

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?

Answer 28

20:1

Having a high ratio of HCO3- gives the blood plenty of buffering capability to handle increases in acidity