lecture 9: acid and base

Question 1

what is PO2

Answer 1

– the partial pressure of oxygen: How much oxygen is dissolved in the arterial blood

Question 2

What is PCO2

Answer 2

– the partial pressure of carbon dioxide: How much CO2 is dissolved in the arterial blood

Question 3

What is pH

Answer 3

the ‘power of hydrogen’: Describes the [H+] of the blood

Question 4

what is HCO3

Answer 4

• plasma bicarbonate: Describes how much bicarbonate is dissolved in the arterial blood.

Question 5

what is BE

Answer 5

: Describes the concentration of bases compared to the ‘expected concentration’. An exact match is zero

Question 6

what is alkalaemia?

Answer 6

refers to raised PH of blood

Question 7

what is acidaemia?

Answer 7

refers to lowered PH of blood

Question 8

what is alkalosis?

Answer 8

describes circumstances that decrease H and increase PH

Question 9

what is acidosis?

Answer 9

describes circumstances that increase H and decrease PH

Question 10

what are acids ?

Answer 10

proton donors acid can dissociate into H+ and A-

Question 11

how did pitts and swan discover the buffering effect of the blood?

Answer 11

♣ they injected 14 molar acids into a dog and found its blood pH barely changed at all. the blood can buffer acids immediately

Question 12

**** what is the henderson hasselbalch equation?

Answer 12

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Question 13

what is the sorensen equation?

Answer 13

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Question 14

what is the henderson equation?

Answer 14

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Question 15

what is the henderson hasselbalch equation?

Answer 15

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Question 16

****practise questions on acid base ?

Answer 16

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Question 17

reference values I need to know? for PO2

Answer 17

>10kPa is normal 8-10 kPa is mild hypoxaemia 6-8 kPa is moderate hypoxaemia <6 kPa is severe hypoxaemia

Question 18

what are the compensatory measures?

Answer 18

• Changes in ventilation stimulate a RAPID compensatory response to change CO2 elimination and therefore alter pH. - Changes in HCO3- and H+ retention/secretion in the kidneys can stimulate a SLOW compensatory response to increase/decrease pH

Question 19

what does acidosis need to correct it?

Answer 19

needs alkalosis

Question 20

what does alkalosis need to correct it?

Answer 20

needs acidosis

Question 21

****what are the normal ABG values?

Answer 21

**** insert

Question 22

what is base excess?

Answer 22

1. The ABG analyser calculates hypothetical [HCO3-] based on PCO2 and assumes no metabolic or renal disturbance. 2. The machine then ELIMINATES the changes in [HCO3-] due to PCO2 so that any change in [HCO3-] is due to metabolic acid base disturbance or a change in renal excretion of acid.

Question 23

what is a rise in base excess due to?

Answer 23

is due to an increase in renal excretion of acid, ingestion/administration of a base or loss of acid from vomiting. The result is a metabolic alkalosis.

Question 24

what is a fall in base excess due to?

Answer 24

excess is due to the overproduction of metabolic acids, the ingestion of acid, a reduction/failure of acid excretion by the kidney or excessive loss of alkali from intestines with diarrhoea. The result is a metabolic acidosis

Question 25

***what chart is used to work out the acid base status of the patient

Answer 25

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