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My Own Renal Biochem > Acid Base Biochemistry > Flashcards

Acid Base Biochemistry Flashcards

1
Q

Acid base balance seeks to?

A

Maintain normal hydrogen ion balance in the body.

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2
Q

Acid base balance achieves this by?

A

Buffers in ecf and icf
Respiratory mechanisms- removal of CO2
Renal mechanisms- reabsorb bicarbonate, secrete H+ ions

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3
Q

Normal range of arterial ph?

A

7.35-7.45

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4
Q

Ph range compatible with life.

A

6.8-8.0

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5
Q

Which mechanisms of blance occur rapidly?

A

Buffering

Respiratory

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6
Q

Which mechanism of balance occur slowly?

A

Renal

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7
Q

CO2 mechanism.

A
  • CO2 end product of aerobic metabolism
  • Found in venous blood
  • RBC in venous blood react CO2 +H2O—H2CO3—>H+ +HCO3–>lungs. In lungs reverse reactions occur and CO2 expelled.
  • H+ generated must be buffered.
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8
Q

Fixed acids

A

•Proteins within body end up producing acid.
• phospholipids-phosphoric acid
•proteins containing sulfur-sulphiric acid.
• When the above are in excess, they tend to accumulat since they are not volatile., hence fixed acids.
• They need to be buffered by intracellular protein buffers till they are excreted by kidney.
I.e phosphate buffers locates in bone.

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9
Q

Acid base balance is disrupted by?

A 
Vomiting
Diarrhoea
Respiratory failuire
Kidny failuire
Infections
Ingestions
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10
Q

What ratio determines blood pH?

A

[HCO3]/Pa(CO2)

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11
Q

What mechanisms alter [hco3]

A

Metabolic acid base disorders(kidneys)

Secondary metabolic compensation.-increased excretion of h+

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12
Q

What mechanisms alter Pa(CO2)

A

Respiratory acid base disorders

Secondary respiratory compensation

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13
Q

Why does acid base balance need to be in a certain range?

A
  • Acid base pairs which buffer the system will become unbalanced under subtle changea in ph.
  • affects drug delivery and enzymatic action
  • Proteins function within a certain optimum ph
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14
Q

What is acidemia?

A

Serum pH <7.36

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15
Q

What is alkalemia?

A

Serum pH > 7.44

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16
Q

Acidosis.

A

Pathologic process that lowers [HCO3] or increases PaCO2

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17
Q

Alkalosis

A

Pathologic process that raises [HCO3] or lowers PaCO2

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18
Q

How does pulmonary compensation work?

A

•peripheral chemoreceptors in carotid body and central chemoreceptors in medulla change minute ventilation upon decreased ph.

Decreased ph—>increased minute ventilation —> decreased PaCO2
As it is increasingly being expelled.

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19
Q

What is anion gap?

A

Estimates unmeasured anions in plasma.
•Usually hco3 accounts for measured anions
• Proteins end up not measured.
• increased proteins,(acid anions) from metabolic acidosis ie phosphates will release h+ released which reacta with hco3 reducing anions accounted for and increasing acid anions and hence the anion gap.

20
Q

Formula for anion gap.

A

AG= Na-(hco3+cl)

21
Q

Causes of respiratory acidosis.

A

Anything thay reduces minute ventilation.
•Airway obstruction
•Aspiration
•drug induced cns depression
•Neuromascular dx ie MG,guillian barre
• Pulmonary dx ie pneumonia edema emphysema
• Thoracic cage damage ie pneumothorax, flail chest

22
Q

What are the respiratory acidosis compensations?

A

Acute- increased hco3 production from intracellular proteins to combine with h+ produced. Inc by 1meq/l for every 10mmhg rise of PaCO2

Chronic- renal retention of hco3. Increases by 3.5 meq/l for every 10mmhg rise in paCO2

23
Q

How to manage respiratory acidosis?

A

Manage airway problem to increase minute ventilation.

•bronchodilators, antibiotics, clear airway, re expand lung, correction of cns dx

24
Q

Normal bicarbonate level?

A

23-29mmol/l

25
Q

Would you expect conc of hco3 to increase with increasing Paco3?

A

Yes.

H+ +hco3 —-> h2co3—>co2 +h2o

26
Q

How do you know it is an acute respiratory acidosis?

A

Hco3 remains unchanged. If it ila chronic it goes up.

27
Q

What causes respiratory alkalosis?

A

Anything that increases minute ventilation.
•hypoxia mediated hyperventilation. Ie high altitude, severe anemia,ventilation perfusion mismatch
• cns mediated ie psychogenic(anxiety, nervousness, etc: cva, increased intracranial pressure .
•pharmacologic ie salicylates, caffeine, vasoprssors,thyroxine
Pulmonary ie pneumonia , pulmonary edema, atelectasis
Hepatic encephalopathy ie damage to brain bc liver didnt remove toxins

28
Q

Would you expect hco3 to decrease or increase with decreases paco2?

A

Decrease.
Eqn : co2+h2o—>h2co3–>h+hco3
The relationship between hco3 and paco2 is directly proportional.

29
Q

Hco3 level in acute r. Alkalosis?

A

Normal

30
Q

Hco3 level in chronic r alkalosis?

A

Reduced.

31
Q

Acute R. Alkalosis compensation ?

A

Plasma hco3 lowered by 2meq/l for every 10mmhg of decreases paco2

32
Q

Chronic r alkalosis compensation?

A

Decrease of 5meq/l of hco3 for every 10mmhg decrease in paco2

33
Q

What is metabolic acidosis?

A

Increased h+ conc

Or decreased hco3 conc

34
Q

Conditions that cause anion gap metabolic acidosis?

A 
M-Methanol
U-ureamia
D-DKA
P-propylene glycol, paraldehyde
I-infection, iron, isoniazid
L- lactic acidosis
E-Ethylene glycol,ethanol
S- salicylates
35
Q

Non anion gap metabolic acidosis causes?

A 
•GI losses of hco3.
Diarrhea, ileostomy, colostomy
•renal losses of hco3
Hyperparathyroidism
Renal tubular acidosis
• ingestion
Acetaxolamide, cacl,mgso4
36
Q

Compensation for metabolic acidosis?

A

Winters formula

1.5*[HCO3-]+6 or 10

37
Q

Treatment for metabolic acidosis

A

Treat underlying condition

38
Q

What is metabolic alkalosis?

A

Decrease in h+
Increase in hco3

Compensated for by hypo ventilation

39
Q

Causes of metabolic alkalosis

A

• Reduced volume
Due to vomiting
Or diuretics (increased urination)

•Normal /increased volume
Due to cusions syndrome
Hyperaldosteronism
Severe pottasium depletion.

40
Q

Treatment of metabolic alkalosis

A

Treat underlying disorder
Correct pottasium levels
Give fluids if urine cl is less than 10 meq/l
Acetazolamide if edematous to increase hco3 secretion.

41
Q

Compensation for metabolic alkalosis?

A

Paco2= 0.9*[HCO3]+15

42
Q

Mixed disorders can exist. Possible mixed disorders include?

A

Metabolic* respiratory processes
Metabolic acidosis and alkalosis
Respiratory acidosis and alkalosis cannot coexist

43
Q

When to consider mixed disorder?

A

Ph = normal

Paco2 and or hco3 conc is abnormal

44
Q

What is the delta ratio?

A

Used when high anion gap has been detected to check if a mixed disorder is present.

45
Q

Delta ratio formula?

A

Change in AG/change in hco3 =(AG-12)/(24-HcO3)

Value less than 2/1 suggests hco3 disnt fall as would be expected of metabolic acidosis. Hence a metabolic alkalosis.

My Own Renal Biochem (7 decks)

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