Acid base balance

Question 1

what artery is usually used for a blood test

Answer 1

radial artery

Question 2

Why is acid base important

Answer 2

Physiologically threat

• Enzyme function eg coagulation
• Electrolyte regulation - hydrogen and potassium ions
• Drug ionization eg local anaesthetics

Diagnotic guide
- Establish diagnosis and to monitor during therapy

Acid base balance composed of acid production and acid elimination

Question 3

what are the 2 ways acid is produced

Answer 3

respiratory - carbonic from CO2

metabolic - organic such as lactate or amino and inrognaic like sulphuric and phosphorus

Question 4

acidic and alkaline secretions are produced in normal GI physiology from where

Answer 4

gastric - hydrogen ion

pancreatic - bicarbonate

Question 5

how is acid removed from the body

Answer 5

respiratory - ventilation removes CO2

metabolic - inorganic excreted via the kidneys unchanged

organic undergo liver metabolism before being excreted

Question 6

formular for pH

Answer 6

-log to the base 10 multiplied by the hydrogen conc

Question 7

what is plasma pH

Answer 7

7.4

Question 8

what is stomach pH

Answer 8

2

Question 9

the acid base homeostasis aims to keep pH constant - what are the 3 main systems for regulation of this

how quick are all these processes

Answer 9

1. Buffers - immediate seconds to minutes
2. Respiratory - rapid minutes to hours
3. Renal ( metabolic) - slow hours to days - plus minor from liver contribution

Respiratory and/or metabolic dominant under normal conditions - other systems provide compensation

Question 10

what is the most important extracellular buffer for maintaing acid-base balance in the blood

Answer 10

carbonic acid-bicarbonate buffer - dissolved Co2 and bicarbonate ion are at eq

other mentions are protein albumin ( histidine - donor of positive charges in case of alkalosis and and negative charges in acidosis) and phosphates

Question 11

the Henderson hasselbalch equation can be written as

Answer 11

pH = pKa + Log [HCO3-] / [H2CO3]

because or rapid reaction resulting from carbonic anhydrase, PCO2 can be substituted for [H2CO3]

Question 12

how does the respiratory system regulate acid-base homeostasis

Answer 12

central chemoreceptors detect rise or fall in Pco2 which is kept between 5.1-5.5 kPa
acts on medulla via the CSF pH to stimulate ventilation to increase to get rid of CO2

Question 13

what is hyperventilation

Answer 13

Hyperventilation is rapid or deep breathing, usually caused by anxiety or panic. This overbreathing, as it is sometimes called, may actually leave you feeling breathless. When you breathe, you inhale oxygen and exhale carbon dioxide.

high volume but low PaCO2

Question 14

how does the renal system monitor acid base homeostasis

Answer 14

The kidneys have two main ways to maintain acid-base balance - their cells reabsorb bicarbonate HCO3− from the urine back to the blood and they secrete hydrogen H+ ions into the urine. By adjusting the amounts reabsorbed and secreted, they balance the bloodstream’s pH.

Question 15

what is respiratory acidosis indicated by

Answer 15

raised carbon dioxide

Question 16

what is metabolic acidosis indicated by

Answer 16

dropped bicarbonate

Question 17

what is respiratory alkalosis indicated by

Answer 17

dropped carbon dioxide due to hyperventilation

Question 18

what is metabolic alkalosis indicated by

Answer 18

raised bicarbonate and severe vomiting

compensation and respiratory failure should be looked for with all

Question 19

final urien acidity is determined by what cells in the DCT

Answer 19

intercalated cells

Question 20

what other ion via contransport - transports bicarbonate into the blood in PCT

Answer 20

sodium

Bicarbonate is the marker of metabolic disturbance but not the cause
So if excess acid is made - conc of bicarbonate is going to full to restore eq
Fall is marker not cause

Question 21

what is the anion gap

Answer 21

A measure to help identify the cause of metabolic acidosis as benign a disturbance of
Organic acid raised anion gap
Or inorganic acid which is normal anion gap

AG = [Na + K] - [Cl + HCO3 ]

total cations must equal anions
the anion gap is usually albumin

this gap increased with metabolic acidosis due to ketoacids

Question 22

how does the body compensate during acidosis

Answer 22

respiratory compensation : primary metabolic acidosis increase hydrogen concentration this acts on peripheral chemoreceptors (aortic and carotid bodies) conducted to the medulla to increase Vmin

opposite changes are seen in compensation fro alkalosis

metabolic compensation : primary respiratory acidosis ( increase CO2) leads to kidney retaining additional bicarbonate and excreting more protons

Question 23

3 rules fro determine acid-base anylsis

Answer 23

Acidosis or alkalosis - pH value
Respiratory or metabolic - biacroabte- metabolic or co2- repsiroatyr
Compensated or not

Compensation attempts to return Ph to normal with change in the box opposite to primary abnormality
Egh primary problem of respiratory acidosis - so CO2 high - compensation comes from increasing bicarbonate

Question 24

How does acetazolamide help

Answer 24

Acetazolamide belongs to a class of drugs known as carbonic anhydrase inhibitors. It works by decreasing the production of fluid inside the eye. It is also used to decrease a buildup of body fluids (edema) caused by heart failure or certain medications.

hydrogen ion retention so less bicarbonate produced