Bioimpedance Spectroscopy Could Effectively Replace Physical Examination for Hyponatremia

Bioimpedance spectroscopy (BIS) could replace physical examination for estimating body fluid status, as it appears to correspond better with clinical diagnosis in hyponatremia patients according to a study published in Yonsei Medical Journal.

Researchers in Korea assessed body fluid volume in 30 patients with hyponatremia using simultaneous physical examinations and BIS. Physical examination was determined by gross edema (edema or non-edema), pretibial pitting edema (pitting or non-pitting), and skin turgor (intact or decreased). The researchers also performed a clinical diagnosis to determine the likely cause of hyponatremia, which stemmed from heart and renal failure, liver cirrhosis, hypothyroidism, adrenal insufficiency, drug induced or tumor-related syndrome of inappropriate antidiuretic hormone (SIADH) secretion, thiazide, or severe dietary deficiency.

According to the authors, physical examination, BIS, and clinical diagnosis showed 9, 10, and 9 patients, respectively, were hypervolemic, meaning they had either gross or pretibial pitting edema. The results of the 3 methods used to estimate body fluid volume also indicated 13, 15, and 16 patients, respectively, were euvolemic, meaning they had neither gross nor pretibial pitting edema, but had intact skin turgor; additionally, 8, 5, and 5 patients, respectively, were hypovolemic, or had neither gross nor pretibial pitting edema, yet had decreased skin turgor. There was significant correlation between physical examination and BIS results, and BIS showed a higher level of agreement with clinical diagnoses than physical examinations.

“In hyponatremia with an uncertain cause, estimating body fluid status could be useful to diagnose the main cause,” the authors concluded. “In addition, the estimation of body fluid status is important to determine the best treatment method for hyponatremia, since therapy for hyponatremia aims at not only achieving an optimal concentration of sodium, but also optimal body fluid status.”

Although BIS studies have shown mixed results in the past, the researchers noted the systems have improved, so BIS could soon be an acceptable method for estimations.

“We suggest that BIS could replace physical examination for estimating body fluid status in hyponatremia,” they wrote. “In addition, we found that the kappa coefficient between BIS and clinical body fluid estimation was higher than that between physical examination and clinical body fluid estimation. Therefore, it is believed that BIS corresponds well with clinical diagnosis compared with physical examination in hyponatremia.”