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1	Hyponatremia Azra Bihorac, MD UF-CCM
2	Remember this! Serum [Na⁺] is a surrogate marker for serum osmolality Na⁺ concentration =
3	Regulation of serum osmolality
4	Regulation of ECF volume
5	Comparison of systems controlling effective circulating volume and osmolality
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8	Non-osmolar stimuli for ADH secretion
9	Hyponatremia
10	Hypoosmolal hyponatremia
11	Hypoosmolal hyponatremia
12	Case 1 A 70 yr old smoker presents with cough and hemoptysis. On exam he is euvolemic. CXR shows a solitary lung nodule. Na 114 K 4 Cl 88 HCO₃ 20 Glucose 110 BUN 9 Cr 0.8 TSH normal Urine osmolality 650 What is the likely cause of his hyponatremia?
13	Hypoosmolal hyponatremia
14	Case 1 Diagnosis: SIADH, probably from lung cancer.
15	Rx of hyponatremia Isotonic saline Water restriction Water restriction If U_Na+U_K<150: Isotonic saline Hypertonic saline/Na tablets Furosemide Demecocycline Hypovolemia Polydipsia SIADH Mild cases
16	What is the effect of this urine output on this patient’s serum Na⁺/osmolality?
17	What is the effect of this urine output on this patient’s serum Na⁺/osmolality?
18	What is the effect of this urine output on this patient’s serum Na+/osmolality?
19	What is the effect of this urine output on this patient’s serum Na+/osmolality?
20	What is the effect of this urine output on this patient’s serum Na+/osmolality?
21	What is the effect of this urine output on this patient’s serum Na+/osmolality?
22	Rx of hyponatremia Isotonic saline Water restriction Water restriction If U_Na+U_K<150: Isotonic saline Hypertonic saline/Na tablets Furosemide Demecocycline Hypovolemia Polydipsia SIADH Mild cases
23	Rate of correction of hyponatremia Acute (< 48 hr) or symptomatic 1-2 mEq/L per hour Chronic (> 48 hr) including SIADH and asymptomatic 0.5 mEq/L per hour Do not exceed Δ 12 mEq/L in 1^st day or correct to ~ 120-125 mEq/L.
24	Calculation of Na⁺ deficit Deficit in mmol = 0.5 x BW [120-Na] Hypertonic saline contains 513 mEq/L Na Volume of 3% saline required (in L) = Deficit/500 Volume of 3% saline required (in mL) = Deficit x 2 Quick check: Each Δ of 1 mEq/L requires ~ 70 ml hypertonic saline.
25	Case 1 continued Bodt weight 70 kg Serum Na 114 Urine lytes: Osmolality 650 Na 120 K 80 How would you manage his hyponatremia?
26	Case 1 continued Chronic asymptomatic hyponatremia First line Rx: Water restriction Second line RX (U_Na+U_K>150) Hypertonic saline/Na tablets and/or furosemide Correct slowly (<0.5 mEq/L/hr).
27	Case 1 continued Deficit = 0.6x70 [120-114] = 252 mmol Hypertonic saline required = 252/500 = 0.5 L Hypertonic saline required = 252x 2 =500 ml Quick check: To correct ΔNa of 6 requires roughly 6 x 70 ml = 420 ml hypertonic saline.
28	Case 1 continued Replace Na deficit over 12 hrs (0.5 mEq/L/hr) 0.5 L of 3% saline over 12 hrs = 40 ml/hr.