Respiratory - Acid & Base Flashcards Preview

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Flashcards in Respiratory - Acid & Base Deck (19)
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1
Q

Which two organs are mostly involved in acid base regulation?

A

Lungs and kidneys

2
Q

What does reduced ventilation cause?

A

Respiratory acidosis

Increased retention of CO2 in blood causes a shift of equilibrium in the below equation right causing an increase in proton concentration.

3
Q

What are the causes of respiratory acidosis?

A

Impair CNS respiratory drive

e.g. Opioid overdose

Impair neuromuscular transmission/muscular weakness

e.g. Obesity e.g. Guillain-Barre

Pulmonary disorders

Obstructive, restrictive, and parenchymal

e.g. COPD

4
Q

What does increased ventilation cause?

A

Respiratory alkalosis

CO2 is blown off, so equilibrium shifts to the left

5
Q

Causes of respiratory alkalosis?

A

Stimulation to Over breathe

  • CNS (Stroke, Anxiety “Medical student”)
  • Hypermetabolic (Thyrotoxicosis)
  • Drugs (Aspirin overdose)
  • Iatrogenic (sometimes on purpose)

Response to Hypoxaemia

  • Asthma
  • PE
  • Altitude

Compensation to Metabolic Acidosis

6
Q

What are the kidney’s two main responsibilites in acid base regulation?

A

1) Reabsorption of filtered bicarbonate
2) Excretion of the fixed acids (acid anion and associated H+)

7
Q

What are the caues of metabolic acidosis?

A

Increased acid intake

Increased acid production
(e.g. ketoacidosis)

Increased acid retention
(e.g. renal failure)

Loss of alkali
(e.g. Renal Tubular Acidosis)

(e.g. methanol)

8
Q

What are the two types of metabolic acidosis?

A

Low anion gap met. ac.

High anion gap met. ac.

9
Q

What is the cause of low anion gap?

A
  • Loss of alkali/HCO3- is cause
  • E.g. proximal renal tubular acidosis
  • E.g. GI loss HCO3-
10
Q

What are the causes of high anion gap?

A
  • Production of additional acid is cause
  • E.g. diabetic ketoacidosis, lactic acidosis, methanol poisoning, ethylene glycol poisoning

Methanol / Metformin

Uraemia

Diabetic ketoacidosis (and alcoholic/starvation ketoacidosis)

Propylene glycol

Isoniazid

Lactate

Ethylene glycol

Salicylates

11
Q

Caues of metabolic alkalosis?

A

Acid loss

e.g. Gastric acid loss due to vomiting

Alkali administration

e.g. Taking 4 bottles of Gaviscon

Intracellular shift of hydrogen ion
e.g. H+ in hypokalemia

Kidney associated

12
Q

What acid base abnormality does Hypokalaemia cause?

A

Metabolic alkalosis

K+ moves out of cells to compensate for low K in blood. H+ in turn moves inside cells causing the alkalosis

13
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

pH is low - acidosis

BE is low - acidotic picture, acid comes from metabolism

CO2 is NOT high - it’s low to compensate metabolic acidosis

14
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

15
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

With raised anion gap

16
Q

A 23 year-old lady with asthma presents to A&E with difficulty in breathing. Her initial ABG on 15 litre of oxygen shows:

  • pH: 7.54 (7.35-7.45)
  • pO2: 10.0 (10–14)
  • pCO2: 3.2 (4.5–6.0)
  • HCO3: 24 (22-26)
  • BE: +0 (-2 to +2)
  • Other values within normal range

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

c) Respiratory Alkalosis no compensation

17
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

c) Respiratory Alkalosis no compensation

Type 1 Respiratory Failure

Low PO2

Normal/Low PCO2

Ventilation-perfusion mismatch

E.g. Pulmonary Embolism

18
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

a) Respiratory Acidosis with partial compensation

Type 2 Respiratory Failure

Low PO2

High PCO2

Impaired gas exchange

E.g. COPD exacerbation

19
Q

71 year-old Man

History of diabetes mellitus and a long smoking history (45 pack-years)

Presents to the emergency department with worsening shortness of breath

On auscultation of the chest there are wide spread crackles and you notice moderate ankle oedema.

  • pH: 7.20(7.35-7.45)
  • pO2: 8.9 (10–14)
  • pCO2: 6.3 (4.5–6.0)
  • HCO3: 17 (22-26)
  • BE: -8 (-2 to +2)
  • Other values within normal range
A

Mixed respiratory and metabolic acidosis