Metabolic Acidosis

Question 1

Case: female. Hurts to urinate.

pH = 7.30 HCO3 = 14 pCO2 = 29 Anion gap = 16

What acid base problems are initially occuring?

Answer 1

pH low. bicarb also low. if it was properly compensated, bicarb would be high. bicarb down by 10, appropriatey resp compsneation for MAc is a 1:1 change. CO2 should be 30. Looks normal. therefore this is:

metabolic acidosis with no respiratory disorder

look at anion gap and bicarb to see if there is more than one metabolic disorder. AG is 16, which is up by 4, implying that we’ve been gaining acid. the appropriate change in bicarb should drop from 24 to 20. it’s actually 14. it’s dropped by 6 more if the only acid base problem was acid gain. therefore, there are multiple problems.

this is a high anion gap (acid gain) metabilic acidosis, and a normal anion gap (loss of buffer) metabolic acidosis.

Question 2

First task with HAGMA is to identify the acid: two broad causes

Answer 2

1. excess acid addition (metabolism or DKA, or toxic alcohol consumption)
2. decreased NH4 production and anion excretion (CRF/ARF)

Question 3

toxic alcohol panels aren’t usually done unless there is a biochemical clue that might indicate that being a cause of the metabolic HAGMA acidosis. What is this biochemical clue?

Answer 3

THE OSMOLAR GAP (2 salts and a sugar BUN)

Question 4

2 mechansims of L-Lactic acidosis (causes HAGMA)

Answer 4

type A; increased production due to tissue hypoxia; usually we go through the krebs cycle, but in the absence of O2, pyruvate turns to lactate– most common cause of lactic acidosis

type B; increased production in absence of tissue hypoxia reduced metabolism

Question 5

First task with NAGMA is to identify the source of __ __

Answer 5

First task with NAGMA is to identify the source of buffer loss

Question 6

two broad causes that can cause NAGMA

Answer 6

1. GI tract loss– would see a preserved NH4 production by looking at the urine net charge (Na + K)-Cl
2. renal loss

Question 7

Treatment of HAGMA involves turning off __ __

Answer 7

Treatment of HAGMA involves turning off acid production

• ex/ for lactic acidosis caused by tissue hypoxia, is to give sufficient volume to cause sufficeint blood flow, to promote sufficient oxygenation to the tissues, preventing hypoxia.

Question 8

should you give sodium bicarbonate in an incidence of metabolic acidosis due to tissue hypoxia?

Answer 8

ehh– if its due to tissue hypoxia, you sholud really try and address the root cause of hypoxia. if its dehydration or volume depletion, make sure you try and re-volumize the patient to get adequate blood flow to the tissues. bicarb might improve thing biochemically but won’t help her physical/clinical symptoms cause it’s stemming from something else.

bicarb might actually make it worse. if we give bicarb and deliver bicarb to ECF, you can see that the bicarb level will rise, causing the buffer to increse CO2, reducing the CO2 removal from the ICF because the diffusion gradient is limited. when CO2 rises in the ICF, it creates a respiratory acidosis. we might make things worse by giving bicarbonate.

Question 9

why might giving sodium bicarb be worse when trying to correct a metabolic acidosis?

Answer 9

bicarb might actually make it worse. if we give bicarb and deliver bicarb to ECF, you can see that the bicarb level will rise, causing the buffer to increse CO2, reducing the CO2 removal from the ICF because the diffusion gradient is limited. when CO2 rises in the ICF, it creates a respiratory acidosis. we might make things worse by giving bicarbonate.

Question 10

T/F; when dealing with endogenous HAGMA (DKA or ketosis) you sohuld give bicarb

Answer 10

false. unless they are having such severe acidosis that you need to correct it a bit.

Question 11

usually you shouldn’t give sodium bicarb to treat a metabolic acidosis. when should you give it?

Answer 11

use bicarb when there i EXOGENOUS HAGMA due to toxocity, to increase elimination. Ex, if ASA toxicity, giving bicarb will promote an ionized form which will cause alkalinity, and you pee out H+ and ASA-

OR if here is a NORMAL ANION GAP (caused by a loss of buffer) then you can give sodium bicaronate.

Question 12

5 points

• Anion gap identifies the mechanism(s) of metabolic acidosis– weather its due to acid gain or buffer loss.
• First task with HAGMA is to identify the acid and workout why its being produced
• First task with NAGMA is to identify the source of buffer loss– then you can correct with sodium bicarb
• Treatment of HAGMA involves turning off acid production– you don’t usually give sodium bicarb unless its due to exogenous acid toxicity
• Treatment of NAGMA involves stopping buffer loss and supplementing buffer