Chapter 8: Fluids and Electrolytes

Understanding fluid transport mechanisms is essential to clinical practice, as solutes and solvents move through the body via diffusion, osmosis, filtration, and active transport, each operating according to distinct concentration and pressure gradients. Plasma osmolality, normally maintained between 275 and 295 mOsm/kg, represents a critical physiological variable that influences cellular function and fluid shifts. The chapter then addresses fluid volume imbalances, distinguishing between dehydration and fluid overload while recognizing that infants and older adults face heightened vulnerability to these conditions. Assessment findings for volume deficit include tachycardia, hypotension, and poor skin turgor, whereas volume excess presents with bounding pulses, hypertension, pulmonary edema, and peripheral edema. The major portion of the chapter focuses on specific electrolyte imbalances with significant clinical implications. Potassium abnormalities pose particular danger due to effects on cardiac conduction, manifesting as characteristic electrocardiographic changes that guide clinical diagnosis and intervention. Sodium imbalances primarily affect neurological function and consciousness level. Calcium and phosphorus maintain an inverse relationship, and hypocalcemia produces specific clinical signs including muscle hyperexcitability. Magnesium imbalances alter neuromuscular and respiratory function, while hypermagnesemia responds to specific pharmacological reversal. The chapter emphasizes critical nursing responsibilities, including appropriate medication administration routes, careful assessment techniques, and recognition that certain patient populations require heightened monitoring. Clinical interventions focus on addressing underlying causes while restoring electrolyte and fluid balance through oral supplementation, intravenous therapy, dietary modification, and pharmacological management tailored to each specific imbalance.