Renal Case: 39-year-old Woman with Type 2 DM

00:01 All right, let's turn to a clinical case and test our knowledge.

00:05 So if we have a 39-year-old woman with a history of Type II diabetes mellitus, and she's admitted with a blood sugar of 700 mg/dL.

00:14 Her exam is remarkable for a blood pressure of 115/70, pulse rate normal at 78 beats per minute, and she's breathing normally at 22 breaths per minute.

00:23 Her jugular venous pressure is normal, and she has no peripheral edema.

00:27 Her serum sodium is 125 mEql/L, and her serum osmolality is 315 mOsmol/kg.

00:37 So, which statement is true regarding this patient's hyponatremia? There is inappropriate ADH release.

00:48 There is nonosmotic stimulation of ADH due to a low effective circulating blood volume.

00:53 This is pseudohyponatremia due to a laboratory artifact.

00:57 or there is presence of an effective osmole in the extracellular fluid that forces water movement from the intracellular fluid compartment to the ECF.

01:07 Now, before we actually go through those answers, let's look at our clinical case and see if there are some clues that can help us out.

01:13 Remember what we said when we have a patient with hyponatremia.

01:17 The first step in diagnosing anything is to determine the plasma osmolality.

01:22 And look at this, her plasma osmolality is elevated.

01:26 It's 315 mOsmol/kg.

01:29 So this means she has hypertonic hyponatremia.

01:33 Now, step two, once we have hypertonic hyponatremia we want to look for the presence of an effective osmole that's exerting a tonic effect on water.

01:42 Here we have it.

01:43 Look at her blood glucose 700 mg/dL.

01:46 So let's go through our answers.

01:48 Letter A, there's an appropriate ADH release.

01:52 That's incorrect.

01:53 Inappropriate ADH, or SIADH occurs in hypotonic euvolemic hyponatremia due to the presence of ADH despite normal volume status and low osmolar state.

02:04 This patient remember is hypertonic.

02:08 How about letter B, there's a nonosmotic stimulation of ADH due to a low effective circulating blood volume.

02:14 Again, that's incorrect.

02:16 The patient is euvolemic on exam.

02:18 She has no signs of volume depletion that would invoke ADH stimulation here.

02:24 Letter C, this is pseudohyponatremia due to a laboratory artifact.

02:28 Also incorrect.

02:29 This is typically going to occur remember with isotonic hyponatremia that should have a normal plasma osmolality.

02:37 And the patient should also have a history of either hyperlipidemia or dysproteinemia.

02:44 Now finally, letter D, there's a presence of an effective osmole in the extracellular fluid that forces water movement from the intracellular fluid compartment to the ECF.

02:54 That is correct.

02:55 This patient is hyperglycemic.

02:57 She has an elevated plasma osmolality and that glucose in the ECF.

03:01 Remember, as an effective osmole, it cannot freely move to the intracellular compartment.

03:06 Therefore, it's exerting a tonic effect causing water movement from the ICF to that extracellular fluid volume.

03:13 There is no primary water gain, just translocation from the ICF to the extracellular fluid compartment.

03:20 So letter D is correct.