NUR 2063 Essentials of Pathophysiology Final Exam Review – Modules 1,2 & 3

NUR 2063 Essentials of Pathophysiology Final Exam Review – Modules 1,2 & 3 What is osmosis? ANS: Net movement of water across a selectively permeable membrane. What is an extracellular fluid volume (ECV) deficit? ANS: A disorder in which there is too little extracellular fluid in the body. What causes an extracellular fluid volume (ECV) deficit? ANS: Removal of a sodium-containing fluid from the body. It is a decrease in saline (isotonic salt water) in the same concentration as the normal extracellular fluid, which is why the condition sometimes is termed saline deficit. In an uncomplicated ECV deficit, the serum sodium concentration is normal. The concentration of the extracellular fluid is normal; the amount of the extracellular fluid is abnormally decreased. Examples: emesis, diarrhea, adrenal insufficiency, extensive diuretic use, hemorrhage, third-space fluid accumulation, burns. What are the clinical manifestations of an extracellular fluid volume (ECV) deficit? ANS: Sudden weight loss (One liter of saline weighs 1 kg; therefore, a person who loses 1 kg in 24 hours has excreted 1 L of fluid or lost it through an abnormal route. It is not possible to lose a kilogram of fat overnight; a sudden weight loss of this magnitude results only from fluid loss, if the body weight is measured accurately), postural blood pressure decrease with concurrent increased heart rate, flat neck veins (or veins collapsing with inspiration) when a patient is supine, prolonged small-vein filling time, prolonged capillary refill time, lightheadedness, dizziness, syncope, and oliguria. An ECV deficit that develops slowly also may be manifested by decreased skin turgor (skin tenting when it is pinched up over the sternum), dryness of oral mucous membranes between cheek and gum, hard stools, soft sunken eyeballs, longitudinal furrows in the tongue, and absence of tears and sweat, hypovolemic shock. How is an extracellular fluid volume (ECV) deficit treated? ANS: Administration of sodium and water as needed to balance the body out. What is an extracellular fluid volume (ECV) excess? ANS: Essentially the opposite of an ECV deficit. It is the condition in which the amount of extracellular fluid is abnormally increased. Both the vascular and the interstitial areas have too much isotonic fluid. In an uncomplicated ECV excess, the concentration of the extracellular fluid is normal, but an excessive amount of that fluid is present. What is the pathophysiology of extracellular fluid volume (ECV) excess? ANS: ECV excess is caused by addition or retention of saline (salt water in the same concentration as normal plasma). For this reason, it sometimes is termed saline excess. As mentioned previously, the hormone aldosterone causes the kidneys to retain saline. ECV excess therefore may be caused by conditions that involve excessive aldosterone secretion. For example, increased aldosterone secretion is a compensatory mechanism that commonly accompanies chronic heart failure and eventually leads to ECV excess. What is hyponatremia? ANS: A serum sodium concentration below the lower limit of normal. The extracellular fluid contains relatively too much water for the amount of sodium ions present. What causes hyponatremia? ANS: Too much water, SIADH, retaining water, psychogenic polydipsia What are the manifestations of hyponatremia? ANS: Nonspecific manifestations of central nervous system dysfunction. They vary from malaise, anorexia, nausea, vomiting, and headache to confusion, lethargy, seizures, and coma. Profound hyponatremia causes fatal cerebral herniation. How is hyponatremia treated? ANS: Oral sodium replacement; nasogastric sodium replacement; IV sodium replacement—if due to water excess (dilutional hyponatremia), restriction of water intake and treatment of the underlying cause (ex. SIADH). What is hypernatremia? ANS: An elevated serum sodium that may occur with water loss or sodium gain. What causes hypernatremia? ANS: Usually caused by inadequate intake or excess water loss (dehydration). Other causes: Deficit of thirst Hypotonic fluid loss Urinary loss GI loss (vomiting, diarrhea) Insensible loss Burns Diuretics DI (Central and nephrogenic) What are the clinical manifestations of hypernatremia? ANS: Similar to those of hyponatremia in that they are nonspecific manifestations of central nervous system dysfunction. In hypernatremia, the increased osmolality of the extracellular fluid causes neurons and glial cells to shrivel because water moves from the cells to the interstitial fluid by osmosis. The dysfunction ranges from confusion and lethargy to seizures and coma. Thirst and oliguria (except for hypernatremia of renal origin) are common. Severe hypernatremia may cause death. How is hypernatremia treated? ANS: It is treated by cause. In water deficits, volume is replaced. In sodium excess, dilution is accomplished with sodium-free IV fluids. What is hypokalemia? ANS: A low serum potassium level.