Acid Base. Large Group 2 -Barnes

Question 1

What is the difference between acidemia and acidosis?

Answer 1

acidemia=pH in the blood shows that it is acidic

acidosis=PROCESS of becoming acidic. can be acidotic and alkaline

Question 2

How do you calculate anion gap? What is a normal anion gap?

Answer 2

AG=(Na+) - (CL- + HCO3-)

normal=12 +/-2

Question 3

What is your expected anion gap? How can this be calculated?

Answer 3

albumin x 3=expected anion gap

Question 4

What happens when you have an anion gap metabolic acidosis?

Answer 4

increasing anions in the system will cause a decrease in bicarbonate–> acidosis

Question 5

What are the causes of anion gap metabolic acidosis?

Answer 5

MUD PILES

Methanol 
Uremia*
DKA*
Polyethylene glycol
Iron 
Lactic acidosis*
Ethanol, ethylene glycol 
Salicylates* 

*=most common

Question 6

What is a Delta Gap? Why do we check it?

Answer 6

Measured AG-Expected AG then add to measured HCO3-

24=concomitant metabolic alkalosis

we check this to see if there is another metabolic process along with the Anion gap metabolic acidosis

Question 7

What equation do we use to check for compensation in metabolic acidosis?

Answer 7

winters formula

expected pCO2=1.5 x [HCO3-] +8 +/-2

Question 8

What equation do we use to check for compensation in metabolic alkalosis?

Answer 8

Expected pCO2 = 0.7 [HCO3-] + 20 mmHg (range: +/- 5)

Question 9

What can initiate metabolic alkalosis? (3)

Answer 9

1. net loss of H+
2. Net addition of HCO3-
3. external loss of fluid containing Cl-

Question 10

What is necessary to maintain a state of metabolic alkalosis? What are some examples? (4)

Answer 10

maintenance: something in the kidneys causing a retention of HCO3-:
1. Cl- depletion
2. K+ depletion
3. Hypercapnea
4. Rarely; primary disorders of specific ion channels

Question 11

How can we tell if a pt is Chloride Responsive? What type of pts do we check for this in?

Answer 11

Chloride responsive: give Cl- and the condition resolves.
-if the urine Cl- is low (<15-20) suspect that the Cl- in the blood is also low and that the pt is chloride responsive

check for this in metabolic alkalosis pts (high HCO3- in the urine can be from low Cl- in the urine)

Question 12

If a pt has Chloride Non-responsive Metabolic Alkalosis, what is the likely diagnosis?

Answer 12

Urine Chloride >20

most common= primary hyperaldosteronism (excess mineralocorticoid) (pt will have HTN) (also presents the same as licorice abuse)

-Urine K+ laxative abuse or severe K+ depletion

can also be impairment of Cl-linked Na+ transporters (Bartter Syndrome or Gitelman syndrome)

Question 13

What is Barnes’ shortcut for compensation?

Answer 13

Bicarb and PCO2 should be 13-15 away from each other is PCO2 is what you expect

Question 14

When do we evaluate a urinary anion gap? What is Urinary Anion Gap?

What does a negative vs positive UAG indicate?

Answer 14

NAGMA pts!!!

UAG=(Na + K+) -Cl-

negative UAG: extra-renal origin of the metabolic acidosis (negative value=large amount of unmeasured extra NH4+ in the urine (Cl- increases with increasing NH4+) –> kidneys are responding appropriately)

Positive UAG: renal origin of metabolic acidosis –> RTA

Question 15

What is Bicarb Reclamation? Where does this primarily take place?

Answer 15

90% in the Proximal Tubule

requires a Na+ dependent secretion of H+ into the lumen where it will combine with filtered bicarb.

with CA in the lumen==> becomes H2O and CO2 which is taken back up into the cells

reacts with CA in cell–> breaks down into H+ (back into lumen) and HCO3- (reabsorbed in the basolateral membrane)

Question 16

What is Bicarbonate Regeneration? Where does it take place?

Answer 16

throughout the renal tubule but the CCD is the final site of urinary acidification

H+ secreted into the urine and combines with NH3 or phosphate as buffers –> excreted

creates “new” bicarb

Question 17

What affect will chronic metabolic acidosis have on total ammonia excretion?

Answer 17

chronic metabolic excretion==> much greater total ammonia excretion

Question 18

What happens to a normal kidney in response to acidosis? What effect will this have on UAG?

Answer 18

increased excretion of NH4+ which will cause an increase in Cl- ions in the urine

this causes an negative value in the UAG because NH4+ is not measured in UAG–> only Cl- is

Question 19

Where is the problem in Type II RTA?

Answer 19

Proximal tubules

the apical membrane Na+/H+ exchanger

Question 20

Where is the problem in Type I RTA? What will result?

Answer 20

Distal tubule

CCD -alpha intercalated cells (problem with K+/H+ ATPase?)

get a build up of intracellular H+ ions –> NAGMA

Question 21

A patient with NAGMA, a positive UAG, urine pH of 7.3, and K+ =3.2 most likely has:
A. Distal RTA
B. Proximal RTA
C. Type IV RTA
D. RTA of Renal Failure

Answer 21

A. Distal RTA

Question 22

What labs can be used to distinguish distal vs proximal RTA? Why?

Answer 22

urinary pH (both will have low K+)

proximal=lower urinary pH because distal tubule can compensate

distal RTA=higher urinary pH because nothing to acidify the urine after it

Question 23

What will Type IV RTA present with?

Answer 23

hyperkalemia
urine pH 15

aldosterone deficiency

associated with DM