Renal Case: 52-year-old Man with Depression

00:01 Let's run through another case.

00:02 So a 52-year-old man with depression was recently started on a Selective Serotonin Reuptake Inhibitor for his depressed mood.

00:10 Although, he has experienced an improvement in his mood, which is great.

00:14 He also has been feeling a little bit nauseated and slightly confused.

00:18 He's taken to the emergency department and on evaluation his serum sodium is noted to be 122 mEq/L.

00:26 He is normotensive on exam and he's noted to have a normal jugular venous pressure.

00:31 His serum osmolality is 260 mOsm/kg.

00:36 His urine osmolality is high at 600 mOsm/kg, and his urine sodium is 42 mEq/L.

00:45 So which statement is true regarding this gentleman's hyponatremia? Letter A.

00:50 There is appropriate ADH release due to a hypovolemic state.

00:55 Letter B.

00:55 This is due to translocational hyponatremia.

00:59 His total body water stores are unchanged, but there is a tonic effect from his SSRI that moves water from the intracellular to the extracellular compartment.

01:08 Letter C.

01:09 There is appropriate ADH release due to a low circulating arterial blood volume despite his hypervolemia.

01:15 Or letter D.

01:16 There is inappropriate ADH secretion or SIADH.

01:21 Let's go through our history and see if we can get some clinical clues.

01:24 So once again, remember our steps that we want to do.

01:27 Step one, we're determining the plasma osmolality.

01:30 Here we can see he actually is hypoosmolar.

01:33 His plasma osmolality is 260 mOsm/kg.

01:37 He is hypotonic.

01:38 So the next thing we want to do when we have a true hypotonic hyponatremia is determine the volume status.

01:45 And look at his exam.

01:46 He has normal neck veins.

01:48 He is normotensive.

01:49 So he is euvolemic on exam.

01:52 The third step is we want to evaluate the presence or absence of ADH.

01:56 The way we do that is by looking at the urine osmolality.

01:59 Here you can see, he has a very concentrated urine or a high urine osmolality.

02:03 It's higher than a serum osmolality.

02:05 That means that ADH is present.

02:08 And step four, we want to evaluate if the Renin-Angio-Aldo-System is activated.

02:14 Here we see that as urine sodium is actually greater than 20 milliequivalents, so it's actually in the 40s, this means that RAAS is suppressed.

02:24 So let's go through our answers.

02:27 Letter A.

02:27 There is appropriate ADH release due to a hypovolemic state.

02:31 Incorrect.

02:32 This gentleman is euvolemic on exam and RAAS is suppressed based on his urine sodium.

02:38 So, letter B.

02:39 This is due to translocational hyponatremia.

02:41 His total body water stores are unchanged but there's a tonic effect from his SSRI that moves water from the intracellular to extracellular fluid compartment.

02:50 That's incorrect.

02:51 Translocational hyponatremia is hypertonic due to the presence of an effective osmole that exerts a tonic effect moving water from the intracellular to extracellular fluid compartment.

03:01 We're going to see that in cases of hyperglycemia or patients who received glycine as an irrigant, or potentially mannitol which is not osmotic diuretic.

03:11 What about letter C? There's an appropriate ADH release due to a low circulating arterial volume despite hypervolemia.

03:19 Also incorrect.

03:21 He is euvolemic on exam and if anything RAAS is suppressed based on his urine sodium.

03:27 So that leaves us with letter D.

03:29 There is inappropriate ADH secretion or SIADH.

03:32 And that answer is correct.

03:34 This is hypotonic euvolemic hyponatremia.

03:37 ADH is present again based on the fact that his urine Osm is greater than a serum Osm and RAAS is suppressed based on the fact that his urine sodium is high.

03:46 The cause in this situation is likely his SSRI.

03:53 So next question, how would we treat this patient? If his neurological status is stable, we can simply withdraw the offending drug so withdrawing the SSRI.

04:03 We want to free water restrict them anywhere between 0.8 to 1.2 liters.

04:08 And we want to ask him to increase his solute in his diet in order to increase water excretion through obligate osmolar excretion.