Applied nutritional investigation Sodium depletion and hemoconcentration: overlooked complications in patients with anorexia nervosa? Lorenza Caregaro, M.D. a, *, Lorenza Di Pascoli, M.D. a , Angela Favaro, M.D. b , Mariateresa Nardi, M.D. a , Paolo Santonastaso, M.D. b a Department of Clinical and Experimental Medicine, University of Padua, Padua, Italy b Department of Neurosciences, Center for Eating Disorders, University of Padua, Padua, Italy Manuscript received June 11, 2004; accepted August 14, 2004. Abstract Objective: This study evaluated sodium and fluid balance disturbances in anorexia nervosa. Methods: Serum urea, creatinine, urea nitrogen/creatinine ratio, protein concentration, osmolality, electrolytes, hemoglobin, and hematocrit were evaluated on admission, after intravenous fluid supplementation, and at discharge in 14 patients who had anorexia nervosa and were admitted to a medical unit for severe malnutrition and/or medical complications. Diet history and physical signs of salt and water depletion were also evaluated on admission. The diagnosis of plasma volume depletion was considered confirmed if serum urea nitrogen/creatinine ratio was higher than 25. Results: Mean body mass indexes were 12.9  2.4 kg/m 2 on admission and 14.2  2.0 kg/m 2 at discharge. Mean duration of hospitalization was 24.2  11.9 d. Plasma volume depletion was found on admission in nine patients (64%), and hyponatremia was associated with hypovolemia (hypo- volemic hyponatremia) in three of them. Most of the commonly used indexes of hemoconcentration (hematocrit, hemoglobin, serum urea, and creatinine) were normal on admission but decreased significantly after intravenous fluid supplementation and were maintained at lower levels at dis- charge (P  0.001, P  0.0004, P  0.009, and P  0.001, respectively, compared with admission values). Hemoconcentration masked an underlying anemia (hemoglobin  12 g/dL) in six patients. Only two of the nine patients with plasma volume depletion had a history of diuretic abuse, and the other seven patients reported long-term sodium restriction as a method to control body weight. Conclusions: Plasma volume depletion and hypovolemic hyponatremia are common in the most severely malnourished patients with anorexia nervosa. Clinicians should be aware that, because of malnutrition, the common indexes of hemoconcentration may be within normal range and that hemoconcentration may mask anemia. Further studies are needed to assess the role of neglected behaviors such as sodium and fluid restriction. © 2005 Elsevier Inc. All rights reserved. Keywords: Anorexia nervosa; Hemoconcentration; Hyponatremia; Sodium restriction; Sodium and water depletion; Plasma volume depletion; Hypovolemia; Prerenal azotemia; Dehydration Introduction Anorexia nervosa (AN) is the most life-threatening of all psychiatric disorders. The mortality rate associated with AN is more than 12 times as high as the mortality rate among young women in the general population [1,2]. Medical com- plications due to malnutrition and/or purging behaviors rep- resent the main cause of mortality in these patients. Hospi- talization in a general medicine unit is often required because of extremely low body weight, fluid and electrolyte imbalance, cardiac disturbances and other medical compli- cations. The guidelines for management of eating disorders indicate that recognizing and correcting electrolyte and fluid disturbances is mandatory before starting a refeeding pro- gram [3]. However, sodium and water balance alterations have been poorly investigated in AN. Water intoxication This work was supported by grants from the Ministero dell’Università e della Ricerca Scientifica e Tecnologica. * Corresponding author. Tel.: +39-049-821-2345; fax: +39-049-821- 1374. E-mail address: lorenza.caregaro@unipd.it (L. Caregaro). Nutrition 21 (2005) 438 – 445 www.elsevier.com/locate/nut 0899-9007/05/$ – see front matter © 2005 Elsevier Inc. All rights reserved. doi:10.1016/j.nut.2004.08.022