Cystic fibrosis (CF) affects the eccrine and exocrine epithelial cells, causing pulmonary disorders, abnormally concentrated sweat, and pancreatic failure. The genetic alteration responsible for this disease is a mutation of the cystic fibrosis transmembrane conductance regulator (CFTR) protein, which acts as a chloride channel, controlling ion transport through the apical membrane.1 Hot weather, intense physical exercise, stress, fever, vomiting, diarrhea or overdressing2 can cause patients to present chloride, sodium and potassium depletion, due to a failure to replace loss of salts.3 Since survival of patients with this disease has increased in recent decades, CF is no longer an exclusively pediatric condition, so it is important to know that other non-respiratory complications exist that may present as a medical emergency.2

We report 3 cases of adults with CF, who, despite the usual recommendations, presented severe dehydration syndrome during the summer.

A 19-year-old man, transport driver, presented in the emergency room with a clinical picture of intense asthenia and some vomiting. He had been working under exposure to high temperatures for several hours. He presented in the emergency room with blood pressure 137/71mmHg, normal body temperature, mucocutaneous pallor, and sunken eyes.

A 25-year-old woman with CF, summer camp monitor, presented in the emergency room with a 24-h history of vomiting (about 20 episodes) and inability to take anything by mouth. She also reported reduced urine output. On arrival, she had arterial hypotension (85/52mmHg).

A 28-year-old man, employee in a mechanical workshop, presented in the emergency room with cramps, generalized muscle pain, and reduced urine output. The day before, he had been working in the sun for a long period.

The patients’ laboratory tests results on admission and discharge are shown in Table 1. All patients received serum replacement therapy, leading to improved biochemical parameters.

Under normal conditions, chloride and sodium are reabsorbed from sweat via the CFTR channel in the sweat glands. When CF patients sweat excessively, this reabsorption fails to occur, leading to excretion of large amounts of sodium chloride and decreased blood levels of these ions.3 This induces secondary hyperaldosteronism with metabolic alkalosis due to increased bicarbonate reabsorption and low blood potassium caused by potassium secretion from the collecting tubule.4 Moreover, the loss of extracellular fluid lowers the glomerular filtration rate and bicarbonate filtration.1 This condition is described as “pseudo-Bartter” syndrome, and is characterized by metabolic alkalosis, hyponatremia with hypochloremia, with no renal tubule involvement.1 It is more common in pediatric patients, and occurs only exceptionally in adolescents and adults; it is sometimes the presenting feature of a CF diagnosis.5 In view of the potential seriousness of these ion alterations, including the risk of arrhythmias with cardiac arrest, muscle paralysis with involvement of the respiratory muscles or laryngospasm, tetany, and metabolic alkalosis convulsions,1 it is important that certain recommendations are followed. Treatment is based on appropriate fluid replacement and correction of the electrolyte deficit, with high sodium, chloride and potassium supplements to correct alkalosis; appropriate prevention, with the addition of salt to the diet (1–4g/day, according to patient age); avoidance of situations leading to excess sweating; and the administration of appropriate supplements during strenuous physical activity.2