Lecture 13 10/22/24

Question 1

What are the general principles of electrolytes and acid/base?

Answer 1

-blood pH should be maintained in a narrow range
-electrolytes are closely linked to acid/base balance
-electroneutrality must always be maintained

Question 2

What are the categories of acid/base disturbances?

Answer 2

-metabolic acidosis/ low HCO3-
-metabolic alkalosis/ high HCO3-
-respiratory acidosis/ high pCO2
-respiratory alkalosis/ low pCO2

Question 3

What is a primary acid/base disturbance?

Answer 3

pathophysiologic state causing alkalosis or acidosis

Question 4

What is a compensatory acid/base disturbance?

Answer 4

-body’s response to a primary acid/base disturbance
-goal is to keep pH as close to normal as possible
-usually the opposite of the primary disturbance

Question 5

What is a mixed acid/base disturbance?

Answer 5

more than one primary disturbance at the same time

Question 6

What are the compensatory mechanisms for each acid/base disturbance?

Answer 6

-metabolic acidosis <-> respiratory alkalosis
-metabolic alkalosis <-> respiratory acidosis

Question 7

What are the characteristics of respiratory compensation?

Answer 7

-in response to primary metabolic disturbance
-change in resp. rate or volume results in change in pCO2
-starts within minutes

Question 8

What are the characteristics of metabolic compensation?

Answer 8

-in response to primary respiratory disturbance
-kidney adjusts H+ and HCO3- secretion/resorption
-may take several days

Question 9

What are the key points about compensation?

Answer 9

-does not bring pH back to completely normal
-aims to return blood pH as close to normal as possible during mixed disturbances

Question 10

What are the cations of importance?

Answer 10

-sodium
-potassium

Question 11

What are the anions of importance?

Answer 11

chloride
-bicarb.

Question 12

What are the characteristics of neutrality?

Answer 12

-cations must equal anions
-gain of a cation requires either gain of an anion or loss of a different cation

Question 13

Which hormones impact sodium conc.?

Answer 13

-ADH
-aldosterone

Question 14

What are the effects of aldosterone?

Answer 14

-resorption of 3Na+ and 1Cl- in exchange for the secretion of 2K+
-overall increase in Na+ concentration

Question 15

What are the effects of ADH?

Answer 15

-resorption of water
-overall decrease in Na+ conc. due to dilution

Question 16

How are changes in sodium conc. interpreted?

Answer 16

in conjunction with body water

Question 17

What can lead to hypernatremia?

Answer 17

-decreased water intake (dehydration)
-loss of water that is greater than loss of sodium (ADH issue)

Question 18

What can lead to hyponatremia?

Answer 18

-increased total body water (edema)
-loss of sodium that is greater than loss of water (hypoadrenocorticism)

Question 19

What are the characteristics of Cl- changes in response to Na+ changes?

Answer 19

-Cl- moves with Na+ to maintain neutrality
-change in Cl- is proportional to Na+

Question 20

What are the characteristics of Cl- changes in response to acid-base status?

Answer 20

-Cl- can exchange for HCO3- to maintain electroneutrality
-change in Cl- is NOT proportional to Na+

Question 21

What are the causes of hyperchloremia?

Answer 21

-processes that lead to increased Na+ (inc. Cl- and Na+)
-metabolic acidosis (inc. Cl-, dec. HCO3-)

Question 22

What are the causes of hypochloremia?

Answer 22

-processes that lead to decreased Na+ (dec. Cl- and Na+)
-metabolic alkalosis (inc. HCO3-, dec. Cl-)

Question 23

What are the factors affecting blood levels of K+?

Answer 23

-degree of renal excretion
-translocation
-GI losses
-intake

Question 24

What can cause hyperkalemia?

Answer 24

-decreased renal excretion
–dec. urine production
–hypoadrenocorticism
-ICF to ECF
–metabolic acidosis
-artifact in large animals

Question 25

What can cause hypokalemia?

Answer 25

-increased renal loss --polyuria -ECF to ICF --metabolic alkalosis -increased GI loss --diarrhea -decreased intake

Question 26

What are the characteristics of bicarbonate?

Answer 26

-major body buffer -produced by cells with carbonic anhydrase -total CO2 is about equal to HCO3- conc.

Question 27

What is the equation for bicarb. formation?

Answer 27

H2O + CO2 <> H2CO3 <> H+ + HCO3-

Question 28

What are the unmeasured cations included in anion gap?

Answer 28

-H+ -calcium -magnesium -immunoglobulins

Question 29

What are the unmeasured anions included in anion gap?

Answer 29

-albumin -lactate -phosphates and sulfates -ketones -ethylene glycol metabolites

Question 30

What are the two equations for anion gap?

Answer 30

-AG = UA - UC: how AG is interpreted -AG = (Na+ + K+) - (Cl- + HCO3-): how AG is calculated

Question 31

What causes increased anion gap?

Answer 31

-increased unmeasured anions -decreased unmeasured cations

Question 32

What causes decreased anion gap?

Answer 32

-decreased unmeasured anions -increased unmeasured cations

Question 33

What is the most common cause of an abnormal anion gap?

Answer 33

increased unmeasured anions

Question 34

What are the differentials for increased unmeasured anions and thus increased anion gap?

Answer 34

-lactic acidosis -renal acidosis -ketoacidosis -ethylene glycol toxicosis

Question 35

What are the analytes for blood gas analysis?

Answer 35

-blood pH -pCO2 -HCO3- -base excess -pO2

Question 36

What are the characteristics of blood gas sample collection?

Answer 36

-stringent -need special heparinized syringe -protect sample from air -analyze promptly

Question 37

What are the characteristics of pH?

Answer 37

-tightly regulated -buffer systems include carbonic anhydrase and hemoglobin

Question 38

What are the characteristics of acidemia?

Answer 38

-blood pH below ref. interval -at least one primary acidosis is present -every acidosis in the patient is primary

Question 39

What is acidosis?

Answer 39

process promoting acidemia

Question 40

What are the characteristics of alkalemia?

Answer 40

-blood pH above ref. interval -at least one primary alkalosis is present -every alkalosis in the patient is primary

Question 41

What is alkalosis?

Answer 41

process promoting alkalemia

Question 42

What are the characteristics of pCO2?

Answer 42

-proportional to dissolved CO2 in blood -acts as a respiratory acid -measurement on blood gas is the only way we can evaluate the resp. component of acid/base