Potassium and pH Flashcards

(54 cards)

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?

24
Q

What is total CO2 controlled by?

25
What occurs if you breathe faster
pCO2 decreases --> respiratory alkalosis
26
What occurs if you breathe slower
pCO2 increases --> respiratory acidosis
27
What happens if someone has lobar pneumonia?
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
What happens to blood going to damaged part of lung in lobar pneumonia
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
What happens to blood going to healthy parts of lung in lobar pneumonia
The good regions of the lung will have abnormally LOW CO2 because you're breathing a bit faster and removing more CO2
30
Oxygen and CO2 levels in focal lung disorders
With FOCAL lung disorders, the oxygen will go down BUT the CO2 will not increase
31
What causes type 1 respiratory failure
caused by FOCAL lung disorders Pneumonia Pulmonary embolism
32
Blood gases in Type 1 respiratory failure
``` Oxygen = LOW (< 8 kPa) CO2 = NORMAL or LOW ```
33
What can also cause Respiratory alkalosis?1.
hyperventilation
34
Why is there an abnormality of BOTH oxygen and CO2 in Type 2 respiratory failure?
Because the whole lung is not functioning properly
35
CAUSES of Type 2 Respiratory Failure:
``` Airways disease (mainly COPD) Pulmonary fibrosis ```
36
Blood gases in Type 2 respiratory failure?
``` pO2 = LOW pCO2 = HIGH ```
37
Common causes of metabolic acidosis
Renal failure Mineralocorticoid deficiency Diarrhoea These causes are also associated with a HIGH CHLORIDE
38
Changes in other acids that cause metabolic acidosis
Lactic Acid | Ketoacids
39
What is the anion gap?
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
Anion gap range
12 +/- 4
41
Anions that aren't measured:
Phosphate Proteins Specific metabolic acid
42
Common causes of metabolic alkalosis:
Diuretics Mineralocorticoid excess Vomiting
43
Things that cause high K+ tend to cause which acidosis/alkalosis?
Metabolic acidosis
44
Things that case low K+ tend to cause which acidosis/alkalosis?
Metabolic alkalosis
45
Diarrhoea - more likely to cause acidosis/alkalosis?
Acidosis
46
Vomiting - more likely to cause acidosis/alkalosis?
Alkalosis
47
Unusual disorders that cause metabolic acidosis that are associated with a low K
Renal tubular disease | Urinary diversion
48
Conditions that cause acidosis but do NOT alter plasma K+
Ketones Lactate Poisons
49
Causes of Ketoacidosis
Diabetic Ketoacidosis (most common) Starvation Alcoholics
50
Causes of Lactic Acidosis
Occurs mainly when there is a lack of tissue perfusion (tissue hypoxia causes anaerobic respiration) Shock Liver failure Short bowel
51
Low pH leads to:
Breathlessness | Causes strong respiratory drive
52
High pH leads to:
Cramps/tetany | Because pH affects calcium ionisation and that affects muscle excitability
53
Compensation for metabolic acidosis
Breathing faster - this lowers CO2 and restores the pH - this change occurs FAST
54
Compensation for respiratory acidosis
Develop a metabolic alkalosis to compensate - changing bicarbonate reabsorption release - this change occurs SLOWLY