A 71 y/o recently widowed female is diagnosed correctly with community acquired pneumonia (CAP). She begs you not to admit her for the small patch of CAP on her chest X-ray. You reluctantly agree after she agrees to call you daily with follow-up and a status report. You prescribean appropriate antibiotic and t ell her to drink plenty of water so as not to become dehydrated.

The first day she calls stating her cough is subsiding and her fever has broken. She complains about feeling weak and tired but that's kind of normal given the pneumonia and the patient's age.

The second day the patient's neighbor calls stating the patient looks funny and she's talking but not making much sense. You tell the neighbor to call 911, thinking your patient is having a stroke. Upon evaluation in the ED, you find NO evidence of a stroke.

What could be causing these symptoms in this patient?

SELECT  here for discussion

** THANKS to Maj (Dr.) Chris Glanton for his help with this Pearl.**

**A recent case report**

This was hyponatremia from excessive water consumption and (probably) excessive ADH secretion. The report stated her labs showed a serum sodium of 106 mEq/L (normal 135-145 mEq/L) in this patient.  With diuresis (using loop diuretics), a normal saline (0.9% sodium chloride) infusion, and close monitoring the patient cleared and was discharged. In severe symptomatic cases, patients may need hypertonic (3%) saline along with loop diuretics (i.e. furosemide) to get the sodium up more quickly followed by free H20 restriction in the ICU. Since this patient has a presumed encephalopathy from her hyponatremia, some experts would use hypertonic (3%) saline up front in an attempt to increase the sodium by about 1-1.5 meq/Liter/hr for the first several hours until her symptoms clear and then back off on the rate with close (i.e. every 1-2 hrs) observation of electrolytes (to ensure you don't increase sodium by more than 12 meq/L in a 24 hour period). I'd suggest an ICU stay during the 3% saline administration to ensure close monitoring of the patient and their fluid balance status. If hypertonic saline is contemplated, consultation with Nephrology should be strongly considered. In any patient with severe hyponatremia, you should correct slowly (as stated above) to avoid central pontine myelinolysis (CPM). Too little extracellular sodium, especially an acute decrease, can cause osmotic shifting of free water into the cells, which in the CNS can cause CPM.

Sodium often receives bad press because excess amounts can cause hypertension and CHF. Sodium is critical is maintaining electrical potentials and maintaining the tonicity and osmolality of the body. Too little extracellular sodium, especially an acute decrease, can cause osmotic shifting of free water into the cells, which in the CNS can cause brain swelling as well as headache, confusion, even seizures and coma can occur.

In this patient, the pneumonia may have caused an excessive secretion of ADH and the patient consumed an excessive amount of water. She later told her physician she drank in excess of FOUR glasses per hour. Pneumonia or any process involving the lung can cause inappropriate secretion of ADH which limits the kidney's ability to excrete free H2O. This in addition with excessive free H2O intake causes hyponatremia.

Lessons learned - hydration is important but quantify a reasonable amount (ex. One eight ounce glass of water every hour). Pneumonia as well as some drugs can augment ADH secretion or it's action on the kidney, leading to impaired free H2O secretion and thus hyponatremia. Elderly patients may be especially sensitive to these changes.

This Pearl is meant for academic and educational purposes only. This Pearl is meant to raise important points regarding the safe and cost-effective pharmacotherapy of patients. It is not meant to be the definitive reference for the treatment or prophylaxis of various diseases. Although every effort is taken to ensure this Pearl is correct and factual, errors may occur. The US Air Force, the 59th Medical Wing (MDW), and 59th MDW Pharmacy assume no liability for incorrect information or harm that may occur from the use of the information included in this Pearl.