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S&P - Water and Electrolytes > Potassium and pH > Flashcards

Potassium and pH Flashcards

1
Q

Role of potassium

A

key determinant of resting membrane potential

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2
Q

ENaC/ROMK channel function

A

Na+ comes in and K+ goes out
So it is important in regulating K+ elimination
Aldosterone activates these channels and inserts them into the membrane

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3
Q

K+ excretion is dependent on:

A

Plasma K+ concentration

Aldosterone

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4
Q

What is Na+/K+ pump is responsible for?

A

Maintaining the difference in electrolyte concentration between the ICF and ECF

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5
Q

What can Na+/K+ pump activity be influenced by?

A

beta adrenergic stimuli and thyroxine

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6
Q

Adrenaline effect on potassium

A

Adrenaline lowers plasma K+

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7
Q

Main causes of low K+:

A

Reduced intake (unlikely)
Renal losses
Intracellular shift

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8
Q

Causes of IC shift of low K+

A

Glucose load
Adrenaline
Alkalosis

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9
Q

Renal losses can cause low K+:

A

Mineralocorticoid excess (e.g. Conn’s syndrome)
Renal tubular disorder
Diuretics

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10
Q

What happens after glucose is ingested and enters the blood?

A

Stimulates a release of insulin, which drives K+ into cells

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11
Q

Most common cause of low K+

A

Diarrhoea + Vomiting

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12
Q

Overview of causes of high plasma K+:

A

Increased intake (unlikely)
Renal retention
Intracellular shift

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13
Q

Causes of renal retention of K+

A

Mineralocorticoid deficiency (Addison’s disease)
ACE inhibitors
Renal failure
Potassium sparing diuretics (e.g. spironolactone)

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14
Q

Causes of IC shift of high K+

A

Insulin deficiency
Acidosis
Exercise
Cell lysis

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15
Q

How does acidosis cause high K+?

A

When you’re acidotic, the H+ ions compete with the K+ ions so when you are acidotic you don’t get as good activity of that pump leading to high plasma K+

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16
Q

Main issue with high K+

A

Abnormal ECG

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17
Q

ECG abnormalities with hyperkalaemia:

A

Tented T waves
Loss of P waves
Broad QRS
BRADYCARDIA

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18
Q

Treatment of Hyperkalaemia

A 
Calcium Chloride (IV) 
50% Glucose 
Sodium Bicarbonate (NaHCO3)
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19
Q

Calcium Chloride as hyperkalaemia treatment mechanism of action

A

NO EFFECT on plasma potassium but it does reduce the effect of potassium on cardiac excitability and limits the ECG changes
It fixes the bradycardia
In other words, it makes your heart resistant to the effects of hyperkalaemia

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20
Q

50% glucose as hyperkalaemia treatment mechanism of action

A

As that glucose is taken up by cells, there is a shift of potassium from the ECF to the ICF
It will lower plasma K+ within half an hour and it will last for about 4-6 hours - the K+ will eventually leak back out again but it does buy you time

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21
Q

Sodium bicarbonate as hyperkalaemia treatment mechanism of action

A

This works if your patient is not fluid overloaded

This also affects the movement of potassium between ECF and ICF

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22
Q

Consequences of changes in pH:

A 
Impaired ventricular function 
Arrhythmias, lower fibrillation threshold 
Vasodilation, catecholamine release 
Impaired oxygen delivery  
Bronchoconstriction  
Reduced hepatic/renal blood flow  
Impaired consciousness 
Respiratory muscle fatigue  
Protein catabolism 
Insulin resistance
23
Q

What is HCO3- controlled by?

A

Kidneys

24
Q

What is total CO2 controlled by?

A

Lungs

25
Q

What occurs if you breathe faster

A

pCO2 decreases –> respiratory alkalosis

26
Q

What occurs if you breathe slower

A

pCO2 increases –> respiratory acidosis

27
Q

What happens if someone has lobar pneumonia?

A

The blood that goes to the bit that has pneumonia will NOT become fully saturated
The blood that goes to the normal parts of the lungs will be fully saturated
Lowers the oxygen content of the blood

28
Q

What happens to blood going to damaged part of lung in lobar pneumonia

A

Blood going to the damaged region will not have its CO2 removed so the blood coming away from this part of the lung will have a higher CO2 concentration

29
Q

What happens to blood going to healthy parts of lung in lobar pneumonia

A

The good regions of the lung will have abnormally LOW CO2 because you’re breathing a bit faster and removing more CO2

30
Q

Oxygen and CO2 levels in focal lung disorders

A

With FOCAL lung disorders, the oxygen will go down BUT the CO2 will not increase

31
Q

What causes type 1 respiratory failure

A

caused by FOCAL lung disorders
Pneumonia
Pulmonary embolism

32
Q

Blood gases in Type 1 respiratory failure

A 
Oxygen = LOW (< 8 kPa) 
CO2 = NORMAL or LOW
33
Q

What can also cause Respiratory alkalosis?1.

A

hyperventilation

34
Q

Why is there an abnormality of BOTH oxygen and CO2 in Type 2 respiratory failure?

A

Because the whole lung is not functioning properly

35
Q

CAUSES of Type 2 Respiratory Failure:

A 
Airways disease (mainly COPD) 
Pulmonary fibrosis
36
Q

Blood gases in Type 2 respiratory failure?

A 
pO2 = LOW  
pCO2 = HIGH
37
Q

Common causes of metabolic acidosis

A

Renal failure
Mineralocorticoid deficiency
Diarrhoea
These causes are also associated with a HIGH CHLORIDE

38
Q

Changes in other acids that cause metabolic acidosis

A

Lactic Acid

Ketoacids

39
Q

What is the anion gap?

A

When the amount of Na+ (cation) should equal the amount of the total anions (Cl- and HCO3-) but there are some protein based anions that are not measured so there is always a little bit of a gap

40
Q

Anion gap range

A

12 +/- 4

41
Q

Anions that aren’t measured:

A

Phosphate
Proteins
Specific metabolic acid

42
Q

Common causes of metabolic alkalosis:

A

Diuretics
Mineralocorticoid excess
Vomiting

43
Q

Things that cause high K+ tend to cause which acidosis/alkalosis?

A

Metabolic acidosis

44
Q

Things that case low K+ tend to cause which acidosis/alkalosis?

A

Metabolic alkalosis

45
Q

Diarrhoea - more likely to cause acidosis/alkalosis?

A

Acidosis

46
Q

Vomiting - more likely to cause acidosis/alkalosis?

A

Alkalosis

47
Q

Unusual disorders that cause metabolic acidosis that are associated with a low K

A

Renal tubular disease

Urinary diversion

48
Q

Conditions that cause acidosis but do NOT alter plasma K+

A

Ketones
Lactate
Poisons

49
Q

Causes of Ketoacidosis

A

Diabetic Ketoacidosis (most common)
Starvation
Alcoholics

50
Q

Causes of Lactic Acidosis

A

Occurs mainly when there is a lack of tissue perfusion (tissue hypoxia causes anaerobic respiration)
Shock
Liver failure
Short bowel

51
Q

Low pH leads to:

A

Breathlessness

Causes strong respiratory drive

52
Q

High pH leads to:

A

Cramps/tetany

Because pH affects calcium ionisation and that affects muscle excitability

53
Q

Compensation for metabolic acidosis

A

Breathing faster - this lowers CO2 and restores the pH - this change occurs FAST

54
Q

Compensation for respiratory acidosis

A

Develop a metabolic alkalosis to compensate - changing bicarbonate reabsorption release - this change occurs SLOWLY

S&P - Water and Electrolytes (3 decks)

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