Medical-Surgical Nursing: An Integrated Approach, 2E Chapter 10 FLUID, ELECTROLYTE, & ACID-BASE BALANCE

Homeostasis The maintenance of the body’s internal environment within a narrow range of normal values. It is an ongoing process, with changes constantly occurring in the body. Maintaining homeostasis is essential to life.

Chemical Organization Basic chemical and physical principles, shown below, are necessary to understand the higher levels of organization. Elements. Atoms. Molecules and Compounds. Ions.

Water Water constitutes approximately 60% of the total body weight of an adult. It is involved in many of the physical and physiological process of the body. Fluctuations in the amount of water in the body can have harmful and even fatal consequences.

Gases Two important gases in the body are oxygen and carbon dioxide.

Acids, Bases, Salts, and pH Acids, bases, salts, and Ph are important for life. When blood pH falls below 7.35, acidosis occurs. When blood pH increases about 7.45, alkalosis occurs.

Buffers Substances that attempt to maintain pH range or H + ion concentration, in the presence of added acids or bases.

Buffer Systems Bicarbonate buffer system (works to regulate pH in both intracellular and extracellular fluids). Phosphate buffer system (works to regulate the pH of intracellular fluid and fluid in kidney tubules). Protein buffer system (works to regulate pH inside cells, especially red blood cells).

Substance Movement Substances must be able to both enter and leave cells. The ability of a membrane to permit substances to pass through it is called permeability. Substances move by passive or active transport.

Types of Passive Transport Diffusion. Osmosis. Filtration.

Diffusion The tendency of molecules to move from a region of higher molecular concentration to a region of lower molecular concentration until an equilibrium is reached.

Osmosis The diffusion of water through a semi- permeable membrane from a region of higher water concentration to a region of lower water concentration.

Filtration Fluids and the substances dissolved in them are forced through cell membranes by hydrostatic pressure. Hydrostatic pressure is the pressure that the fluid exerts against the membrane.

Active Transport Accomplished by means of carrier molecules, which can latch onto specific molecules and transport them in or out of the cell. Examples of important ions transported b this process are calcium, sodium, potassium, and magnesium.

Fluid & Electrolyte Balance Human life is suspended in a saline solution having a salt concentration of 0.9%. For life to continue and cells to properly function, body fluids must remain fairly constant with regard to amount of water and specific electrolytes of which they are composed.

Body Fluids Intracellular fluid (All of the water and ions inside the cells). Extracellular fluid (fluid outside the cells).

Edema When the amount of interstitial fluid (fluid in tissue spaces around each cell) returned to the circulatory system lessens and the fluid accumulates in the tissue spaces, the tissues become swollen. This condition is called edema.

Dehydration When more water is lost from the body than is replaced. Caused by water deprivation, excessive urine production, profuse sweating, diarrhea, and extended periods of vomiting.

Sources of Fluid Loss Skin (loss of 300 to 400ml. per day by diffusion and perspiration). Lungs (300 to 400ml. per day with expired air, saturated with water vapor). Gastrointestinal Tract (200ml. per day in feces). Kidneys (1,200 to 1,500ml. per day).

Disturbances in Electrolyte Balance Sodium. Potassium. Calcium. Magnesium. Phosphate. Chloride. Around these primary areas:

Sodium Hyponatremia (subnormal serum sodium value). Hypernatremia (above normal serum sodium value).

Potassium Hypokalemia (subnormal serum potassium value). Hyperkalemia (above normal serum potassium value).

Calcium Hypocalcemia (subnormal serum calcium value). Hypercalcemia (above normal serum calcium value).

Magnesium Hypomagnesemia (subnormal serum magnesium value). Hypermagnesemia (above normal serum magnesium value).

Phosphate Hypophosphatemia (subnormal serum phosphate value). Hyperphosphatemia (above normal serum phosphate value).

Chloride Hypochloremia (subnormal serum chloride value). Hyperchloremia (above normal serum chloride value).

Acid-Base Balance Buffer systems. Respiratory Regulation of Acid-Base Balance. Renal Control of Hydrogen Ion Concentration. The body has three main control systems that regulate acid-base balance to counter acidosis or alkalosis:

Diagnostic and Laboratory Data The biochemical indicators of acid-base balance are assessed by measuring the arterial blood gases (ABGs).

Acid-Base Imbalances Metabolic Alkalosis Excess HCO 3 Can be caused by diarrhea and steroid or diuretic therapy. Respiratory Alkalosis Deficit H 2 CO 3 Caused by hyperventilation Metabolic Acidosis Deficit HCO 3 Most common in cases of kidney disease and diabetes Respiratory Acidosis Excess H 2 CO 3 Caused by hypoventilation

Assessment and Fluid Balance Health History. Diagnostic and Laboratory Data. Physical Examination Daily Weight, Vital Signs, Intake and Output, Thirst, Skin, Buccal (Oral) Cavity, Eyes, Jugular and Hand Veins, Neuromuscular System.

Diagnostic and Laboratory Data Hemoglobin and Hematocrit Indices. Urine pH. Serum Albumin. Osmolality (a measurement of the total concentration of dissolved particles per kilogram of water). Serum Osmolality. Urine Osmolality.

Fluid Balance & Nursing Diagnosis Fluid volume excess. Fluid volume deficit. Fluid volume deficit, risk for. Gas exchange, impaired. Cardiac output, decreased. Knowledge deficit. Breathing pattern, ineffective. Anxiety. Thought processes, altered. Injury, risk for. Oral mucous membrane, altered. Diagnoses relevant to fluid imbalances may include:

Fluid Balance & Implementation Monitoring daily weight. Measuring vital signs. Measuring intake and output. Providing oral hygiene. Initiating oral fluid therapy. Maintaining tube feeding. Monitoring intravenous therapy. Common interventions include:

IV Therapy Intravenous therapy is the administration of fluids, electrolytes, nutrients, or medications by the venous route. Clients receiving IV therapy require constant monitoring for complications.