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FFP SOB > Arterial blood gases > Flashcards

Arterial blood gases Flashcards

1
Q

When are ABGs done

A

diagnosis treatment and monitoring of respiratory and cardiac illnesses

Also used for intra-operative monitoring and in intensive care

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2
Q

Steps to interpret ABG

A

ph- academia or alkalaemia>
PCo2 and HCo3-= respiratory or metabolic?
Compensation-is there any

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3
Q

Respiratory compensatory mechanisms

A

Acidic Co2 excreted through hypervantilation or retained through hypoventilation

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4
Q

Metabolic compensatory mechanisms

A
  • Renal excretion of H+ in urine in respiratory acidosis

- Increase in HCo3- concentration in hypoventilation or respiratory acidosis

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5
Q

pH for acidaemia

A

pH <7.35

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6
Q

pH for alkalaemia

A

pH >7.45

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7
Q

High pCO2?

A

Respiratory acidosis

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8
Q

Low pCO2

A

Respiratory alkalosis

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9
Q

What is base excess

A

The theoretical amount of acid needed to bring a pt fully oxygenated blood to a normal pH at room temp

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10
Q

What does a high base excess mean

A

metabolic alkalosis

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11
Q

What does a low base excess mean

A

Metabolic acidosis

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12
Q

What is respiratory acidosis

-What is bicarbonate like

A
  • Decrease in gaseous exchange leading to retention of CO₂
  • High PCO₂ leads to renal retention of bicarbonate to buffer excess H⁺
  • Compensation by the kidneys results in an increase in secretion of H⁺ over 3-5 days leading to increase in plasma bicarbonate level
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13
Q

Central causes of respiratory acidosis

A

Drugs e.g morphine and sedatives
Stroke
Infection

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14
Q

Airway causes of respiratory acidosis

A

Asthma

COPD

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15
Q

Parenchymal emphysema causes of respiratory acidosis

A

Pneumoconiosis
Bronchitis
Acute respiratory distress syndrome

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16
Q

Neuromuscular causes of respiratory acidosis

A

Poliomyelitis
Kyphoscoliosis
Myasthenia gravis
Muscular dystrophies

17
Q

Miscellaneous causes of respiratory acidosis

A

Obesity

hypoventilation

18
Q

What is respiratory alkalosis

  • hat is co2 like and ammonium like
  • What is bicarbonate like
A
  • Alveolar hyperventilation leads to excess exhalation of CO₂, resulting in low PCO₂
  • Compensation by the kidneys results from decreased ammonium (NH₄⁻) excretion, leading to a fall in bicarbonate
19
Q

CNS causes of respiratory alkalosis

A 
Pain, anxiety, psychosis
Fever
Cerebrovascular accident/stroke
Meningitis/encephalitis
Trauma
20
Q

Hyperaemia or tissue hypoxia causes of respiratory alkalosis

A 
High altitude
Pneumonia
Pulmonary oedema
Aspiration
Severe anaemia
21
Q

Drugs or hormonal causes of respiratory alkalosis

A

pregnancy, progesterone, salicylates

22
Q

Stimulation of thoracic neural receptors causes of respiratory alkalosis

A

haemothorax, flail chest
Cardiac failure
Pulmonary embolism

23
Q

Miscellaneous causes of respiratory alkalosis

A

septicaemia
Mechanical hyperventilation
Hepatic failure
Heat exposure

24
Q

What is metabolic acidosis

  • What is Bicarbonate like
  • What do the lungs do
A

-Results from the body producing too much acid or the kidneys failing to excrete enough (H⁺)
-Initially this creates a decrease in bicarbonate as carbonic acid is produced to buffer the H⁺
The lungs compensate by hyperventilation and blowing off the CO₂

25
Q

What can be used to differentiate the causes of metabolic acidosis

A

Anion gap. If the gap is normal, bicarbonate is being lost either by GI loss e.g. diarrhoea or renal disease allowing loss

High anion gap results from increased production of acids e.g. lactic acid, rate or diabetic ketoacidodis or large amounts of acid e.g. aspirin overdose

26
Q

High anion gap causes of metabolic acidosis

A

Lactic acidosis
Ketoacidosis: e.g. diabetic, alcohol abuse, starvation
Renal failure: acute and chronic
Toxins e.g. methanol, salicylates

27
Q

Bicarbonate loss from GI tract (Normal anion gap) causes of metabolic acidosis

A

Diarrhoea
Extra-renal pancreatic or small bowel drainage
Drugs e.g. CaCl2, magnesium sulphate

28
Q

Renal acidosis (normal anion gap) causes of metabolic acidosis

A

Proximal renal tubular acidosis

Distal renal tubular acidosis

29
Q

Drug induced causes of metabolic acidosis (normal anion gap)

A

K+ sparing diuretics, spironolactone, trimethoprim, ACEi, NSAIDs

30
Q

Other causes of metabolic acidosis

A

Rapid saline infusion

31
Q

What is metabolic alkalosis
What is bicarbonate like
What is compensatory mechanism

A
  • Results from increased bicarbonate due to either decreased H⁺ concentration (e.g. due to vomiting) or a direct increase in bicarbonate
  • Bicarbonate shift can occur from retention, an intracellular shift in H⁺ or by ingestion of large amounts of alkali (e.g. antacids).
  • The lungs compensate by slower breathing to retain more CO₂
32
Q

GI causes of metabolic alkalosis

A

Vomiting
NG suction
Villous adenoma

33
Q

Renal diuretic causes of metabolic alkalosis

A

Hypercalcaemia

Recovery from lactic acidosis or ketoacidosis

34
Q

Effective extracellular volume expansion of metabolic alkalosis

A 
High renin: renal artery stenosis 
Accelerated hypertension
Aldosteronism 
Cushing's 
Steroids
35
Q

How to assess respiratory failure

A

IS PaO2 <8?

no: pt is not in resp failure
yes: pt is in rest failure

Is PaCO2 <6?
Yes: pt is in T1RF (type 1 respiratory failure)
NO: pt is in T2RF

FFP SOB (8 decks)

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