Essential Physiologic Concerns Chapter 41 ■ Fluids and Electrolytes

Fluid and electrolyte disorders are very common in critically ill patients. There are some circumstances in which a patient is placed in intensive care for the management of a specific electrolyte disturbance such as hyponatremia or hyperkalemia. The development of electrolyte disturbances among critically ill patients is also common due to breakdown of homeostatic mechanisms that prevent the development of electrolyte disturbances. These impairments in homeostatic function are numerous such as renal failure, use of diuretics, and nonosmotic release of antidiuretic hormone (ADH) due to nausea, pain, or other stimuli. In this chapter the pathophysiology of electrolyte disturbances will be addressed with a focus on presentations common among intensive care unit (ICU) patients. Disorders of water balance (hyponatremia and hypernatremia) will be addressed in more detail due to the importance of these disorders as a cause of morbidity and mortality and the prevalence of impaired water balance in ICU patients.