The Concept of Balance or Steady State in Nephro-physiology
The correct answer to the most appropriate time for follow-up visit after starting the low salt diet and diuretic treatment is two weeks. This is the time at which the patient will enter and stay in the new lower volume status. Upon evaluation at this time we can take the appropriate decision regarding the diuretic dose according to the current volume status achieved by this dose. If we find the patient at an optimal volume then will keep the current dose, otherwise will adjust up or down as needed. Interestingly, from ethical point of view many doctors offer a free or 50% discount charge for the follow-up visit within two weeks of the first visit. 64% answered this correctly. The next most popular answer was follow-up in two days with a score of 31%, however, this choice is not correct because it is too early to see a meaningful effect of the diuretic and how it will stabilizes at the end.
The correct answer of the second question is f- None of the above with a low score of 20%. Frequently we use this option to hide the correct answer when it is easy to guess and to test the reasoning of the exam taker. The correct answer should be to evaluate the volume status at the follow-up visit and keep or modify the dose accordingly. The most popular choice was a- no change in diuretic dose with a score of 49%. This option will be true if the patient status is found to be as intended, but if he is on somewhat still hyper or he developed hypovolemic state the dose should certainly be adjusted. As the most diuretic dose is the first one which may cause at the beginning severe polyuria, but gradually the polyuria decrease till he reaches the new steady state after 10–14 days and hence his urine output will return to normal matching of intake the patient may think that the diuretic is no more effective but in fact it is mandatory to keep it on-board to maintain the achieved volume status.
The potassium balance is disturbed by diuretics because of excessive urinary loss which usually stabilizes in two weeks and remains constant indefinitely after that if all the other factors affecting potassium regulation remains unchanged. Hence, the correct answer is b- two weeks and was most popular with a score 39%, followed by a- one week with a score of 25% and obviously it is still early at this time to know how potassium will settle at the end.
The correct answer of the above question is a- only once and the score was low of only 14%. The hint in the question which was not addressed by the exam takers that all other factors affecting potassium regulation are assumed to be unchanged, however, the most popular response was d- every three months with a score of 66% and this is reasonable and understandable in clinical practice because it is impossible to keep all the factors regulating the potassium constant for ever and we have to check the potassium level every 3–6 months.
Hypokalemia is a common side effect of diuretics particularly due to increase of the urine flow and sodium delivery to the distal tubules which will greatly increase the urinary potassium excretion. As high sodium diet will increase the delivery of sodium to the distal tubules hence the potassium excretion will greatly increases. The urinary sodium and osmolality is highly variable and difficult to interpret while patients are taking diuretics. Hence, the correct answer is b- hypokalemia with a score of 18%, while the most popular was d- urine sodium of 100 with a score of 23% and obviously this is wrong because if the patient was really in a steady state and the urine sample collected appropriately it will indicate compliance and adherence with the low salt diet contrary to choice e- 200 mmol which may indicate then noncompliance.
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