Acid Base balance & arterial blood gas Flashcards

1
Q

pH< 7.35
pH > 7.45
pH between 7.35 nd 7.45?

A

1) acidosis
2) alkalosis
3) this is either normal or has a mixed acid base balance.

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2
Q

what are the buffer for acid base balance?

A
  • proteins
  • haemoglobin
  • carbonic acid/bicarbonate
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3
Q

where will acid/ alkali be excreted from?

A

lungs
kidneys

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4
Q

what are the normal values of ABG?
pH
pO2
pCO2
bicarbonate

A

pH= 7.35-7.45

pO2= 12-13 kPa

pCO2 = 4.5- 5.6 kPa

bicarbonate = 22-26 mol/l

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5
Q

when will acid base disturbances occur?

A

when…

  • there is a problem with ventilation
  • there is a problem with renal function
  • overwhelming acid or base load the body can’t handle.
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6
Q

step 1 interpretation of ABG results

A

assess the oxygenation (look at pO2)

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7
Q

if someone is hypoxic and has a very low RR, what is most likely going on?

A

this would suggest that they have chronic cyanosis which means the body has become used to this increased firing.

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8
Q

what are the different ways to measure oxygenation?

A

pulse oximetry

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9
Q

what if there if a low pO2, what may there be a problem with?

A

There may be a problem with:
- getting oxygen into the lungs
- oxygen getting into the blood
- oxygenation of tissues.

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10
Q

high pO2, what can this cause?

A
  • retinal damage
  • mucus membrane damage
  • alveoli collapse
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11
Q

what are the adverse effects of high oxygen levels?

A
  • increased risk of hypercapnic respiratory failure in acute exacerbations of COPD
  • increased mortality survivors of cardiac arrest
  • increased mortality in intensive care patients
  • increased mortality in acute severe asthma.
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12
Q

why are high oxygen levels bad?

A
  • generate free radicles
  • collapse of alveoli due to atelectasis
  • irritation to mucus membranes
    …. leads to ocular toxicity, myocardial damage, neuro damage etc …
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13
Q

what is the British thoracic society guidelines?

A
  • oxygen is a treatment for hypoxia not dyspnoea alone.
  • in an unstable medical emergency give high conc of oxygen then titrate to target once stable.
  • target 94-96% normally
  • 88-92% for type 2 respiratory failure.
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14
Q

step 2 interpretation of ABG results?

A

assess the PH

pH< 7.35 is acidosis
ph> 7.45 is alkalosis

pH between 7.35 and 7.45 = normal or mixed acid base abnormality

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15
Q

acidosis ?

alkalosis?

A

acidosis= too much pco2 and you cannot get rid of it.

alkalosis= too little pCO2.

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16
Q

step 3 interoperation of ABG?

A

what appears to be the cause for the acidosis/ alkalosis?

17
Q

if the ph is low:

what would a respiratory cause for the acidosis look like in the ABG?

what might a metabolic cause for this acidosis look like in the ABG?

A
18
Q

step 4 in interoperation of ABG?

A

is there compensation seeming to occur?

remember we said that the body will always try to maintain pH between 7.35-7.45. Compensation is altering of function of the respiratory or renal system in an attempt to correct an acid - base imbalance

19
Q

if the pH is low because of a respiratory cause, how might the body compensate?

if the pH is high because of a respiratory cause, how might the body compensate?

if the pH is low because of a metabolic cause, how might the body compensate?

A
20
Q

how do you know if compensation is occurring?

A

if pCO2 and HCO3- is moving in the same direction, compensation is possibly occurring.

  • if both values move in opposite directions, more than 1 pathology must be present.
21
Q

in a patient with COPD, why would you expect them to have a high pCO2?

A

because they have an obstructive disease, they can’t actually respire enough to release the CO2.

22
Q

what drug is given to reverse opioid overdose?

A

naloxone

23
Q

what happens in chronic respiratory alkalosis?

A

in chronic respiratory acidosis, the kidneys compensate by retaining bicarbonate. this takes a few days to reach its maximal value.

24
Q

what would the values for acute and chronic respiratory acidosis?

A

acute:

pH= 7.20
pO2= 28.7kPa
pCO2= 11 kPa
HCO3- = 25 mmol/l

chronic:
pH = 7.32
pO2= 6.0 kPa
pCO2= 10.6 kPa
HCO3- = 37 mmol/l

25
Q

what are causes of hyperventilation?

A
  • acute severe asthma
  • pulmonary embolism
  • pulmonary oedema
  • anxiety attack
26
Q

what things cause an abnormal level of central respiratory drive?

A
  • hypoxia
  • direct stimulation of respiratory centre
  • psychogenic
26
Q

chronic respiratory alkalosis- high altitude?

what happens?
is there compensation?

A
  • hyperaemia Is induced, hyperventilation is prominent.
  • compensation occurs by renal excretion of bicarbonate.
27
Q

kussmal breathing?

A

rapid deep breathing at a consistent pace.

28
Q

diabetic ketoacidosis?

A

hyperventilation to blow out increased CO2.

29
Q

WHAT DOES IT SHOW IF THERES A LOW BICARBONATE?

A

compensation for the increased CO2.