Something to think: hyponatremia

Case 1

A 70-year-old man with non-small-cell lung cancer presents to the clinic with fatigue and dizziness for 1 month. He also complains of weight loss (5-10 pounds) and anorexia. His wife states that he seems forgetful. His blood pressure is 95/47 without orthostasis or tachycardia. He does not have peripheral edema, and the remainder of the exam is unremarkable.

Laboratory Analyses

Electrolyte panel: Sodium 115 mmol/L; potassium 6.1 mmol/L; chloride 83 mmol/L; bicarbonate 20 mmol/L; blood urea 9.9 mmol/l; creatinine 123umol/L; glucose 3.96mmol/L.

Serum osm 243 mOsm/kg; urine osm 343 mOsm/kg

The Problem

Speculate on the cause of hyponatremia and support your speculation in several ways.
(solution)

Case 2

A 58-year-old schizophrenic man was brought to the hospital because of strange behavior. He was disoriented and provided no history.

On the basis of the lab results presented here, your task is to identify the acid-base disturbance and postulate a cause for it.

Metabolic profile:

Sodium 139 mmol/L

Potassium 4.7 mmol/L

Chloride 90 mmol/L

Bicarbonate 14 mmol/L

Blood urea 6.42mmol/L

Creatinine 88.4 umol/L

Glucose 5.6 mmol/L

Arterial blood gas:

pH 7.49

pCO2 15

pO2 169 (2 L nasal O2)

HCO3 (calculated) 11

The Problem

What is the acid-base disturbance?

What is a reasonable cause of the disturbance?
(solution)