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.

Acid Base Biochemistry Flashcards by Mavis Mawuena

Acid base balance seeks to?

Maintain normal hydrogen ion balance in the body.

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Acid base balance achieves this by?

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

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Normal range of arterial ph?

7.35-7.45

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Ph range compatible with life.

6.8-8.0

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Which mechanisms of blance occur rapidly?

Buffering

Respiratory

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Which mechanism of balance occur slowly?

Renal

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CO2 mechanism.

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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Fixed acids

•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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Acid base balance is disrupted by?

Vomiting
Diarrhoea
Respiratory failuire
Kidny failuire
Infections
Ingestions

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What ratio determines blood pH?

[HCO3]/Pa(CO2)

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What mechanisms alter [hco3]

Metabolic acid base disorders(kidneys)

Secondary metabolic compensation.-increased excretion of h+

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What mechanisms alter Pa(CO2)

Respiratory acid base disorders

Secondary respiratory compensation

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

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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What is acidemia?

Serum pH <7.36

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What is alkalemia?

Serum pH > 7.44

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Acidosis.

Pathologic process that lowers [HCO3] or increases PaCO2

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Alkalosis

Pathologic process that raises [HCO3] or lowers PaCO2

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How does pulmonary compensation work?

•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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What is anion gap?

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.

Formula for anion gap.

AG= Na-(hco3+cl)

Causes of respiratory acidosis.

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

What are the respiratory acidosis compensations?

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

How to manage respiratory acidosis?

Manage airway problem to increase minute ventilation.

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

Normal bicarbonate level?

23-29mmol/l

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

Yes. | H+ +hco3 —-> h2co3—>co2 +h2o

How do you know it is an acute respiratory acidosis?

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

What causes respiratory alkalosis?

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

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

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

Hco3 level in acute r. Alkalosis?

Normal

Hco3 level in chronic r alkalosis?

Reduced.

Acute R. Alkalosis compensation ?

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

Chronic r alkalosis compensation?

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

What is metabolic acidosis?

Increased h+ conc | Or decreased hco3 conc

Conditions that cause anion gap metabolic acidosis?

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

Non anion gap metabolic acidosis causes?

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

Compensation for metabolic acidosis?

Winters formula | 1.5*[HCO3-]+6 or 10

Treatment for metabolic acidosis

Treat underlying condition

What is metabolic alkalosis?

Decrease in h+ Increase in hco3 Compensated for by hypo ventilation

Causes of metabolic alkalosis

• Reduced volume Due to vomiting Or diuretics (increased urination) •Normal /increased volume Due to cusions syndrome Hyperaldosteronism Severe pottasium depletion.

Treatment of metabolic alkalosis

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

Compensation for metabolic alkalosis?

Paco2= 0.9*[HCO3]+15

Mixed disorders can exist. Possible mixed disorders include?

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

When to consider mixed disorder?

Ph = normal | Paco2 and or hco3 conc is abnormal

What is the delta ratio?

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

Delta ratio formula?

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.