MedEd ABG Flashcards

1
Q

what controls CO2

A

lungs

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2
Q

what controls HCO3-

A

kidneys

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3
Q

what are causes of respiratory acidosis

A

retaining CO2 (hypoventilation)

pulmonary disorders (COPD, asthma)
respiratory depression (opiods)
impaired neuromuscular transmission or muscular weakness
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4
Q

what causes respiratory alkalosis

A

losing CO2 (hyperventilation)

CNS (stroke, anxiety)
hypermetabolic (thyrotoxicosis)
drugs (aspirin overdose)

PE

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5
Q

what are the major functions of the kidneys with regards to acid-base balance

A

1 reabsorption of HCO3-

2 excretion of fixed acids (H+)

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6
Q

what are causes of metabolic acidosis

A
increased intake (methanol)
increased production (DKA)
increased retention (renal failure)
loss of alkali (T2 Renal Tubule Acidosis)
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7
Q

what is the normal anion gap

A

8-16

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8
Q

what are causes with a low or normal anion gap

A

loss of alkali is cause

  • proximal renal tubular acidosis
  • GI loss (diarrhoea)
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9
Q

what are causes with a high anion gap

A

increased acid

  • renal failure
  • DKA
  • lactic acidosis
  • ingestion of methanol, ethanol
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10
Q

what are causes of metabolic alkalosis

A
acid loss
-vomiting (gastric acid)
alkali administration
-gaviscon
intracellular shift of H+
-hypokalaemia
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11
Q

14 yr old male patient brought to A&E by mother. The patient seems to be passing in and out of consciousness and vomited upon arrival. The patient appears short of breath and is clutching his abdomen in pain. The A&E registrar performed an Arterial Blood Gas, the results of which are:

pH: 7.12 (7.35-7.45)
pO2: 11.5 (10–14)
pCO2: 3.2 (4.5–6.0)
HCO3: 9 (22-26)
BE: -17 (-2 to +2)

a) Respiratory Acidosis with partial compensation
b) Metabolic Acidosis with partial compensation
c) Respiratory Alkalosis no compensation
d) Respiratory Alkalosis with partial compensation
e) None of the above

A

b) Metabolic Acidosis with partial compensation

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12
Q

if the pH is low and the pCO2 is high, what is indicated

A

resp acidosis

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13
Q

if the pH is low and the pCO2 is low, what is indicated

A

metabolic acidosis

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14
Q

if the pH is high and the pCO2 is high, what is indicated

A

metabolic alkalaosis

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15
Q

if the pH is high and the pCO2 is NOT high, what is indicated

A

resp alkalosis

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16
Q

what is the base excess

A

the amount of acid needed to neutralise ph

  • if acidosis - negative, acid not needed
  • if alkalosis - positive, acid needed
17
Q

A 16 year-old girl with no previous medical history collapses at school and is brought to A&E. On examination she appears thin and has lanugo hair.

pH: 7.56 (7.35-7.45)
pO2: 10.7 (10–14)
pCO2: 6.0 (4.5–6.0)
HCO3: 31 (22-26)
BE: +5 (-2 to +2)

a) Respiratory Acidosis with partial compensation
b) Metabolic Acidosis with partial compensation
c) Respiratory Alkalosis no compensation
d) Metabolic Alkalosis with partial compensation
e) None of the above

A

d) Metabolic Alkalosis with partial compensation

18
Q

A 32 year-old man presents to the emergency department having been found collapsed. He looks unkempt and is malodorous.

pH: 7.25 (7.35-7.45)
pO2: 11.1 (10–14)
pCO2: 3.2 (4.5–6.0)
HCO3: 11 (22-26)
BE: -15 (-2 to +2)
Potassium: 4.5
Sodium: 135
Chloride: 100
A

metabolic acidosis

19
Q

how is the anion gap calculated

A

cations (Na, K) - Anions (HCO3, Cl)

20
Q

what is a mneumonic for causes of raised anion gap

A

MUD PILES

Methanol/Meformin
Uraemia
DKA
Propylene glycol
Isoniazid
Lactate
Ethylene glycol
Salicylates
21
Q

You are called to see a 54 year old lady on the ward. She is three days post-cholecystectomy and has been complaining of shortness of breath. Her ABG is as follows:

pH: 7.49 (7.35-7.45)
pO2: 7.5 (10–14)
pCO2: 3.9 (4.5–6.0)
HCO3:  22 (22-26)
BE: -1 (-2 to +2) 

a) Respiratory Acidosis with partial compensation
b) Metabolic Acidosis with partial compensation
c) Respiratory Alkalosis no compensation
d) Respiratory Alkalosis with partial compensation
e) None of the above

A

None - T1RF

22
Q

what are features of T1RF

A

low pO2

low/normal pCO2

23
Q

A 64 year old gentleman with a history of COPD presents with worsening shortness of breath and increased sputum production. His oxygen saturations are now 89%.

pH: 7.21 (7.35-7.45)
pO2: 7.2 (10–14)
pCO2: 8.5 (4.5–6.0)
HCO3: 29 (22-26)
BE: +4 (-2 to +2)

a) Respiratory Acidosis with partial compensation
b) Metabolic Acidosis with partial compensation
c) Respiratory Acidosis with no compensation
d) Respiratory Alkalosis with partial compensation
e) None of the above

A

None - T2RF

24
Q

what are features of T2RF

A

low PO2

high PCO2