Hypernatremia due to Hypovolemia ("Dehydration") in Dementia

Author: V. Dimov, M.D., Assistant Professor of Medicine and Pediatrics, University of Chicago
Reviewer: S. Randhawa, M.D., Allergist/Immunologist, Internist, Fort Lauderdale, FL

An 86-year-old African American female (AAF) was admitted to the hospital after she had a seizure while waiting for a swallow evaluation as an outpatient. Her family members report that the patient has baseline advanced dementia, which has been worsening over the last year. She is not verbal (she can conduct a meaningful verbal communication).

Past medical history (PMH)

Dementia, hypertension (HTN), constipation.

Medications

Iron supplements, ferrous sulfate (FeSO4) 325 mg po bid, asprin (ASA) 81 mg po daily, Colace (docusate) 300 mg po qhs.

Social history (SH)

The patient is a nursing home (NH) resident, and she is totally dependent in terms of activities of daily living (ADLs) and instrumental activities of daily living (IADLs).

Physical examination

Vital signs (VS) showed a normal temperature of 36.5 C, heart rate of 94 bpm, respirations 12 per minute, blood pressure 120/87 mm Hg (36.5-94-14-120/87).

The examination of Head, Eyes, Ears, Nose, and Throat (HEENT) showed that she the head was normocephalic, atraumatic (NC/AT), and she had dry mucosal membranes (MM).

The chest was clear to auscultation bilaterally (CTA (B)).

The cardiovascular system (CVS) examination showed that she had clear heart sounds (clear S1S2) but she was tachycardic. There were no murmurs, rubs or gallops (m/r/g).

The examination of the extremities showed no clubbing, cyanosis and edema (c/c/e). She had a decreased skin turgor.

The neurological examination showed that she was somnolent, but without focal findings of neurological deficit.

What is the most likely diagnosis?

In her case, the seizure can be due to hypernatremia, or less likely, to an intracranial process.

Why does the patient have hypernatremia?

Poor oral (PO) intake is often seen in advanced dementia, and can lead to hypotonic hypovolemia and hypernatremia.

What laboratory tests would you suggest?

Complete blood count with differential (CBCD), basic metabolic panel (BMP) to confirm the presence and the quantify the degree of hypernatremia, and to look for other metabolic abnormalities and signs of infection.

Electrocardiogram (ECG or EKG) to exclude an acute cardiac process.

A CT head without contrast is indicated to exclude an intracranuial process such as hematoma, tumor or stroke.

What happened?

The BMP showed hypernatremia with a sodium level (Na) of 155 mEg/L. Hypotonic intravenous fluid (IVF) was started, D5W.


Hypernatremia (click to enlarge the image).


Resolution of hypernatremia with D5W (click to enlarge the image).

The CT of the head revealed no changes since previous exam one year ago. The radiologist report was as follows: There is no acute parenchymal hemorrhage or extra axial fluid collection. There is severe, extensive parenchymal volume loss with ex vacuo dilatation of the lateral, third, and fourth ventricles. There are confluent areas of low attenuation in the white matter diffusely, consistent with extensive chronic small vessel ischemic changes. calcifications. There is no mass, mass effect, or midline shift. There are no bony lesions are fractures.

Impression: No change. Extensive parenchymal volume loss. Extensive chronic small vessel ischemic changes.

What type of fluid would you recommend in this patient? What is the infusion rate?

Calculate the water deficit first, by using the standard formula available from Adrogue, HJ; and Madias, NE. Primary Care: Hypernatremia. New England Journal of Medicine 2000; 342(20):1493-1499.

Change in serum Na+ = (infusate Na+ + infusate K+) - serum Na+/total body water + 1

Infusate Na+ (mmol/L): 3% NaCl - 513, 0.9% NaCl (NS) - 154, Lactate Ringer's - 130, 0.45% NaCl (½ NS) - 77, 0.2% NaCl (¼ NS) - 34, 5% Dextrose in water (D5W) - 0.

Total Body Water (in liters): Children, 0.6 x weight, Women, 0.5 x weight, Men, 0.6 x weight, Elderly Women, 0.45 x weight, Elderly Men, 0.5 x weight.

Insensible water losses is in the range of 500 to 1500 ml per day. Fever increases insensible water losses by 10% per degree Celsius above 38°, or 100-150 ml per day increase per degree Celsius above 37°.

Divide the calculated water deficit in half. Add one liter to the number. This is the amount of free water that should be given over the next 24 hours. Do not correct the water deficit completely during the first 24 hours. Only half of it should be replaced.

Remember that the calculated amount is free water, i.e. D5W (not normal saline (NS) = 0.9% NaCl).

The only clinical situation when normal saline (NS) is the preferred treatment of hypernatremia is when the patient is hypotensive.

In the majority of cases, the water deficit is replaced with hypotonic fluid: D5W or 1/2 NS.

D5W is the preferred fluid because less volume is needed replace the free water. With 1/2 NS, the calculated infusion rate could be as high as 400 ml per hour. Most of the patients with hypernatremia are elderly, with a variable ejection fraction, and administering large amount of intravenous fluids (IVF) can place them at risk for fluid overload and pulmonary edema.

What happened with the patient?

The water deficit was replaced with D5W at 125 ml per hour, with a gradual decrease in the sodium level to normal. The patient became more alert, but continued to refuse food.

What is the next step?

A swallow evaluation was ordered, which indicated that the patient may need alternative means of nutrition.

The family was called and the options were discussed - hospice or percutaneous endoscopic gastrostomy (PEG) tube placement. The risks of PEG placement were explained, along with the fact that according to most studies, PEG tubes do not prolong life in demented patients.

What happened next?

The family decided to proceed with PEG tube placement. A gastroenterology (GI) consult was called, CBC, PTT/PT were normal, and a PEG tube was placed with no complications. The patient was discharged to a nursing home.

Final diagnosis

Hypernatremia due to hypovolemia ("dehydration") in a demented patient.

What did we learn from this case?

Hypovolemia is a common cause of hypernatremia in elderly demented patient. Hypernatremia can present with seizures.

The free water deficit needs to be calculated for correct replacement. The best fluid to replace the deficit is D5W.

It is very important to suggest to the elderly patients their families and to formulate an advance directive, detailing the measures that they would like implemented in case they become incapacitated, and cannot speak for themselves. This can help to avoid unnecessary, and sometimes futile, interventions in the future.

References

MedCalc Formulas: Hyponatremia & Hypernatremia.
Free Water Deficit in Hypernatremia. MDCalc.
Hypernatremia in Emergency Medicine. eMedicine, Medscape, 2009.Adrogue, HJ; and Madias, NE. Primary Care: Hypernatremia. New England Journal of Medicine 2000; 342(20):1493-1499.
Adrogue, HJ; and Madias, NE. Primary Care: Hyponatremia. New England Journal of Medicine 2000; 342(21):1581-1589.
Recurrent Aspiration Pneumonia. NEJM Images in Clinical Medicine, 11/2008.

Related reading


Ethical Dilemmas: Artificial Feeding. Shrujal Baxi MD, Ethics Section Editor, and Joseph Lowy MD, Medical Director, Palliative Care Service at NYU Hospital.
Hypovolemia versus Dehydration. Renal Fellow Network, 2009.
Bioethics Degree

Published: 3/20/2005
Updated: 01/26/2012

1 comment:

  1. I was very impressed with the way this case study was explained. I clearly understood better the reasons and treatments of dehydration. I will go to this site more often for answers as a nurse. Good job.

    ReplyDelete