NEW GUIDELINES FOR HYPONATREMIA

New guidelines on the diagnosis, classification, and treatment of true hypotonic hyponatremia have been published online in theEuropean Journal of Endocrinology. The guidelines focus on managing patients, rather than on treating absolute sodium levels, the authors emphasize.

"Hyponatremia, defined as a serum sodium concentration of less than 135 mmol/L, is the most common disorder of body fluid and electrolyte balance encountered in clinical practice," write Goce Spasovski, MD, PhD, from the State University Hospital Skopje, Macedonia, and colleagues from the Hyponatremia Guideline Development Group.

"It can lead to a wide spectrum of clinical symptoms, from subtle to severe or even life-threatening, and is associated with increased mortality, morbidity, and length of hospital stay in patients presenting with a range of conditions. Despite this, the management of patients remains problematic," they stress.

The guidelines recommend that any hospital-based clinician must be able to accurately diagnose, classify, and treat hyponatremia, which occurs in up to 30% of hospitalized patients.

The excess of body water compared with sodium and potassium results in cellular edema, particularly in the brain.

Because of the potential for brain damage, severe cases are medical emergencies. And complications of milder cases of hyponatremia may include impaired mobility and cognition, as well as osteoporosis and fracture.

A wide range of conditions can cause hyponatremia — including heart failure, nausea and vomiting, adrenal failure, and ectopic vasopressin secretion as part of a malignancy — and, as a result, it is managed by clinicians from a broad spectrum of backgrounds. This has resulted in a variety of approaches to its diagnosis and treatment, the authors say.

In an attempt to standardize management, the new recommendations have been developed jointly by the European Society of Intensive Care Medicine (ESICM), the European Society of Endocrinology (ESE) and the European Renal Association–European Dialysis and Transplant Association (ERA–EDTA), represented by European Renal Best Practice (ERBP).

"The scope of clinical situations in which one might encounter hyponatremia was recognized from the outset," guidelines coauthor Stephen Ball, FRCP, PhD, MBBS, a consultant endocrinologist at Newcastle Hospitals NHS Trust, United Kingdom, told Medscape Medical News. "This meant we needed to make sure the guidance was fit for the purposes of any doctor on a hospital ward or indeed in a community setting, [maintaining] a style that was user-friendly and gave practical advice throughout."

The guidelines specifically address the management of hyponatremia in adults only. They do not cover hyponatraemia in children because the guideline group judged that this represents "a specific area of expertise."

Treat Serious Hyponatremia First; Avoid Overcorrection

Dr. Ball believes the greatest impact on clinical practice will come from new advice to manage the patient, rather than simply looking at the sodium level.

"Highlighting a situation that requires urgent management independent of the underlying cause is a key point within the guidance. We think this should allow for more timely intervention and consequently save lives. Intervention is more important than investigation until the patient is stabilized," he stressed.

Another author, Bruno Allolio, MD, from the University of Würzburg, Germany, told Medscape Medical News that the first indication of hyponatremia often will come from a low serum sodium concentration performed as part of a routine laboratory assessment. "Mild" hyponatremia is defined as a serum sodium concentration between 130 and 135 mmol/L, "moderate" between 125 and 129 mmol/L, and "profound" hyponatremia as less than 125 mmol/L.

If hyponatremia is serious and symptomatic, it is "life-threatening" because it can cause brain edema, Dr. Allolio explained. In this instance, the first line of treatment will be prompt intravenous infusion of hypertonic saline, with a target increase of 6 mmol/L over 24 hours (and not exceeding 12 mmol/L) and an additional 8 mmol/L during every 24 hours thereafter until the serum sodium concentration reaches 130 mmol/L.

However, one difficulty is that treating serious hyponatremia entails walking a very fine line, said Dr. Allolio, because overcorrection represents a real danger too.

Overcorrection of hyponatremia can result in osmotic demyelination syndrome (ODS), which has "disastrous consequences for the brain that may persist for the rest of life," he cautioned. For this reason, the use of hypertonic saline to correct serious hyponatremia "must be performed on the ward with very close monitoring," he stressed.