Potassium pathology

Question 1

Describe the distribution of potassium in the body

Answer 1

140 mmol/l - IC
4mmol/l-EC
Total= 3976mmol

Question 2

What are the 3 steps that potassium is regulated by?

Answer 2

Intake, Cellular distribution and Renal Excretion

Question 3

How much of potassium is filtered a day in a kidney?

Answer 3

576mmol

Question 4

What are the components that cellular distribution depends on?

Answer 4

-insulin- this is the IN hormone, moves K+, glucose INSIDE the cell

-catecholamines
-ph- decrease in PH -> increase in K+
-osmolarity- hypertonicity causes water out of cell and brings K+ with it
-cell turnover(construction/destruction) K+ leaves the cell if there is trauma, lysis, haemolysis and hypothermia of the cell
treating megaloblastic anemia K+ in

Question 5

Where is the filtered potassium reabsorbed in the kidney?

Answer 5

Loop of Henle and proximal tubule

Question 6

Where is the potassium in excreted urine secreted from in the kidney?

Answer 6

cortical collecting ducts

Question 7

What cells are present in the cortical collecting duct?And which cell is a/w K+ excretion

Answer 7

Principal cells a/w K+ excretion

and also intercalated cells ( H+ excretion)

Question 8

Explain how K+ is excreted

Answer 8

Sodium passes down cortical collecting duct to which it enters the principal cell via ENAC flowing down a chemical gradient and also causes negative charge on interior of collecting duct lumen. This is followed by potassium secretion where increased NAK+ATPase decreases intracellular sodium

Question 9

What is the principal determinant for potassium secretion by the kidney ?
How is it affected?

Answer 9

negative charge on interior of cortical collecting duct

disrupted by chloride resorption

Question 10

What two processes regulate potassium handling

Answer 10

tubular flow

aldosterone - which increases number and activity of NaKATPase, ENaC, K channel

Question 11

When do potassium disorders occur?

Answer 11

When both aldosterone and distal tubular flow are affected

hypokalaemia: aldosterone and tubular flow increased
hyperkalaemia: decreased aldosterone and tubular flow

Question 12

Define hypokalemia

normal, moderate, severe

Answer 12

<3.0mmol/L
moderate hypokalemia is a serum level of <3.0mmol/L
severe hypokalemia <2.5mmol/L

Question 13

List the causes of hypokalemia

Answer 13

decreased intake
intracellular shift
increased excretion -> primary and sec hyperaldosteronism and potassium wasting nephropathies

Question 14

What are some potassium wasting nephropathies?

Answer 14

hypomagnesemia, drug toxicity, RTA, polyuria ,unresorbable anions

Question 15

What is a/w secondary hyperaldosteronism

Answer 15

diuretics, salt wasting nephropathies and vomiting

Question 16

What are causes of intracellular shift?

Answer 16

Beta agonist for asthma and COPD, refeeding syndrome, cell growth, periodic paralysis, tocolytics for preterm labor

Question 17

Consequences of hypokalemia

Answer 17

hypertension and stroke (due to high aldosterone)
ECG changes and arrythmia
muscle weakness/paralysis
urinary concentrating deficits

Question 18

Treatment of hypokalemia

Answer 18

give preferably oral potassium

Question 19

Why shouldnt IV potassium be given?

Answer 19

conc IV potassium can cause phlebitis
IV potassium in dextrose can cause a release of insulin lowering plasma potassium
IV potassium in saline- volume overload

Question 20

Define HYPERkalaemia

Answer 20

K+ >5.4mmol/L

Question 21

Causes of hyperkaleamia

Answer 21

increased intake, extracellular shift and decreased renal excretion

Question 22

What are the components of increased potassium intake?

Answer 22

salt substitutes, TPN, enteral supplements, penicillin, high potassium foods , blood transfusions, dialysate

Question 23

What causes extracellular shift?

Answer 23

hyperosmolality 
-DKA and hypergylcaemia
Cell destruction 
-rhabdomyolysis
-tumor lysis syndrome
Drugs
-Beta blockers
-Digoxin
-Succinylcholine 
Acidemia

Aaron Has Da Cell(phone)

Question 24

What causes decreased renal K+ excretion?

Answer 24

Renal failure, hypoaldosteronism, Drugs- ARBS ACEI, NSAIDS, spironolactone, trimethoprim , triamterene, amiloride, RTA1 and 4, Gordon’s syndrome

Question 25

What causes a loss of GFR by decreasing delivery of NA to distal nephron thus preventing potassium excretion

Answer 25

kidney failure, NSAIDs, Gordon’s syndrome

Question 26

What drugs block eNAc channel

Answer 26

amiloride, triamterene, trimethoprim

Question 27

What diseases cause blockade of eNaC channel

Answer 27

Type 1 RTA

Pseudohypoaldosteronism type 1

Question 28

What does hypoaldosteronism do?

Answer 28

Reduce number and activity of eNAC, K channel and NAKATPAse

Question 29

Explain causes of hypoaldosteronism

Answer 29

congenital, adrenal insufficiency (Addisons disease) , diabetes (hyporenin-hypoaldosterone)
Drugs : ACEi/ARB/Renin inhibitors, heparin, ketoconazole, spironolacotone

Question 30

Consequences of hyperkaelmia

Answer 30

muscle weakness

ECG changes and arrythmia

Question 31

Treatment for hyperkalemia

Answer 31

reduce intake(stop K+ products i.e PTN, enteral , blood transfusion, products high in K+) , induce intracellular shift (IV insulin, inhaled beta agonists) and increase renal excretion - diuretics, fludrocortisone, dialysis, bolysterene resins

Question 32

What is the goal of tx for hyperkalaemia

Answer 32

prevent arrythmias

Question 33

What can be given to stabilize cardiac membranes

Answer 33

calcium