chapter 13
Creatinine
0.7-1.4. Best indicator of renal function. End product of metabolism of muscle. Serum creatine levels will increase when renal function decreases.
Urine Specific Gravity
1.010 - 1.025 measures the kidneys ability to excrete or conserve water. Less reliable indicator of concentration. Larger the amount of urine, the smaller the specific gravity. increased glucose or protein in urine can cause a falsely elevated specific gravity.
BUN(blood urea nitrogen)
10-20 mg/dL. BUN is made up of urea, an end product of the metabolism of protein by the liver. Amino acid breakdown produces large amounts of ammonia molecules, which are absorbed into the bloodstream. Ammonia molecules are converted to urea and excreted in the urine. The normal BUN is 10 to 20 mg/dL (3.6 to 7.2 mmol/L). The BUN level varies with urine output. Factors that increase BUN include decreased renal function, GI bleeding, dehydration, increased protein intake, fever, and sepsis. Those that decrease BUN include end-stage liver disease, a low-protein diet, starvation, and any condition that results in expanded fluid volume (e.g., pregnancy).
Urine osmolality
200-800 mOsm/kg
Serum Osmolality
275-290 mOsm/kg. Serum osmolality primarily reflects the concentration of sodium, although blood urea nitrogen (BUN) and glucose also play a major role in determining serum osmolality.
Which of the following is the most common cause of symptomatic hypomagnesemia in the United States?
Alcoholism is currently the most common cause of symptomatic hypomagnesemia in the United States. Any disruption in small bowel function, as in intestinal resection or inflammatory bowel disease, can lead to hypomagnesemia.
Urine sodium values
As sodium intake increases, excretion increases; as the circulating fluid volume decreases, sodium is conserved. Normal urine sodium levels range from 75 to 200 mEq/24 hours (75 to 200 mmol/24 hours). A random specimen usually contains more than 40 mEq/L of sodium. Urine sodium levels are used to assess volume status and are useful in the diagnosis of hyponatremia and acute kidney injury.
causes of fluid shifts
Changes in osmolality of blood: More or less concentrated - causes osmotic pressure changes Capillary leak: the escape of blood plasma through capillary walls to surrounding tissues, muscle compartments, organs or body cavities Third-Spacing: abnormal accumulation of fluid into extracellular and extravascular spaces
Factors that contribute to dehydration in elderly
Dehydration in the elderly is common as a result of decreased kidney mass, decreased glomerular filtration rate, decreased renal blood flow, decreased ability to concentrate urine, inability to conserve sodium, decreased excretion of potassium, and a decrease of total body water
Anion Gap
Difference between the concentrations of serum cations and anions: determined by measuring the concentrations of sodium cations and chloride and bicarbonate anions.
early evidence of third spacing
Early evidence is a decrease in urine output despite adequate fluid intake
A client is diagnosed with syndrome of inappropriate antidiuretic hormone (SIADH). Laboratory results reveal serum sodium level 130 mEq/L and urine specific gravity 1.030. Which nursing intervention helps prevent complications associated with SIADH?
Excessive release of antidiuretic hormone (ADH) disturbs fluid and electrolyte balance in SIADH. The excessive ADH causes an inability to excrete dilute urine, retention of free water, expansion of extracellular fluid volume, and hyponatremia. Symptomatic treatment begins with restricting fluids to 800 ml/day. Vasopressin is administered to clients with diabetes insipidus a condition in which circulating ADH is deficient. Elevating the head of the bed decreases vascular return and decreases atrial-filling pressure, which increases ADH secretion, thus worsening the client's condition. The client's sodium is low and, therefore, shouldn't be restricted.
The nurse is caring for a patient in metabolic alkalosis. The patient has an NG tube to low intermittent suction for a diagnosis of bowel obstruction. What drug would the nurse expect to find on the medication orders?
H2 receptor antagonists, such as cimetidine (Tagamet), reduce the production of gastric HCl, thereby decreasing the metabolic alkalosis associated with gastric suction. Maalox is an oral simethicone used to break up gas in the GI system and would be of no benefit in treating a patient in metabolic alkalosis. KCl would only be given if the patient were hypokalemic, which is not stated in the scenario. Furosemide (Lasix) would only be given if the patient were fluid overloaded, which is not stated in the scenario.
A nurse is caring for a client in acute renal failure. The nurse should expect hypertonic glucose, insulin infusions, and sodium bicarbonate to be used to treat:
Hyperkalemia is a common complication of acute renal failure. It's life-threatening if immediate action isn't taken to reverse it. Administering glucose and regular insulin, with sodium bicarbonate if necessary, can temporarily prevent cardiac arrest by moving potassium into the cells and temporarily reducing serum potassium levels.
The nurse is caring for a client who has been admitted with a possible clotting disorder. The client is complaining of excessive bleeding and bruising without cause. The nurse knows to take extra care to check for signs of bruising or bleeding in what condition?
Hypocalcemia or low serum calcium levels can affect clotting. Therefore, in this condition, the nurse should take extra care to check for bruising or bleeding.
IV solutions contain dextrose or electrolytes mixed in various proportions with water. Pure, electrolyte- free water can never be administered by IV because it rapidly enters red blood cells and causes them to rupture.
IV solutions contain dextrose or electrolytes mixed in various proportions with water. Pure, electrolyte- free water can never be administered by IV because it rapidly enters red blood cells and causes them to rupture.
One day after a patient is admitted to the medical unit, you note that the patient is oliguric. You notify the acute-care nurse practitioner who orders a fluid challenge of 200 mL of normal saline solution over 15 minutes. This intervention will achieve which of the following?
If a patient is not excreting enough urine, the health care provider needs to determine whether the depressed renal function is the result of reduced renal blood flow, which is a fluid volume deficit (FVD or prerenal azotemia), or acute tubular necrosis that results in necrosis or cellular death from prolonged FVD. A typical example of a fluid challenge involves administering 100 to 200 mL of normal saline solution over 15 minutes. The response by a patient with FVD but with normal renal function is increased urine output and an increase in blood pressure. Laboratory examinations are needed to distinguish hyponatremia from hypernatremia.
You are caring for a patient with a secondary diagnosis of hypermagnesemia. What assessment finding would be most consistent with this diagnosis?
If hypermagnesemia is suspected, the nurse monitors the vital signs, noting hypotension and shallow respirations. The nurse also observes for decreased DTRs and changes in the level of consciousness. Kussmaul breathing is a deep and labored breathing pattern associated with severe metabolic acidosis, particularly diabetic ketoacidosis (DKA), but also renal failure. This type of patient is associated with decreased DTRs, not increased DTRs.
You are the nurse evaluating a newly admitted patients laboratory results, which include several values that are outside of reference ranges. Which of the following would cause the release of antidiuretic hormone (ADH)?
Increased serum sodium causes increased thirst and the release of ADH by the posterior pituitary gland. When serum osmolality decreases and thirst and ADH secretions are suppressed, the kidney excretes more water to restore normal osmolality. Levels of potassium, hemoglobin, and platelets do not directly affect ADH release.
Infiltration
Infiltration is the administration of nonvesicant solution or medication into the surrounding tissue. This can occur when the IV cannula dislodges or perforates the wall of the vein. Infiltration is characterized by edema around the insertion site, leakage of IV fluid from the insertion site, discomfort and coolness in the area of infiltration, and a significant decrease in the flow rate.
What is a interstitial fluid shift '' third spacing''
Loss of ECF fluid into a space that does not contribute to equilibrium between the ECF and ICF is
Clinical Manifestations of hypokalemia
Manifestations of hypokalemia include fatigue, anorexia, nausea, vomiting, muscle weakness, leg cramps, decreased bowel motility, paresthesias (numbness and tingling), and dysrhythmias. If prolonged, hypokalemia can lead to an inability of the kidneys to concentrate urine, causing dilute urine (resulting in polyuria, nocturia) and excessive thirst. Potassium depletion suppresses the release of insulin and results in glucose intolerance. Decreased muscle strength and DTRs can be found on physical assessment. You would expect decreased, not increased, muscle strength with hypokalemia. The patient would not have diarrhea following bowel surgery, and increased bowel motility is inconsistent with hypokalemia.
Diffusion
Movement of molecules from an area of higher concentration to an area of lower concentration. Energy is NOT needed
You are the nurse caring for a 77-year-old male patient who has been involved in a motor vehicle accident. You and your colleague note that the patients labs indicate minimally elevated serum creatinine levels, which your colleague dismisses. What can this increase in creatinine indicate in older adults?
Normal physiologic changes of aging, including reduced cardiac, renal, and respiratory function, and reserve and alterations in the ratio of body fluids to muscle mass, may alter the responses of elderly people to fluid and electrolyte changes and acidbase disturbances. Renal function declines with age, as do muscle mass and daily exogenous creatinine production. Therefore, high-normal and minimally elevated serum creatinine values may indicate substantially reduced renal function in older adults. Acute kidney injury is likely to cause a more significant increase in serum creatinine.
You are caring for a 65-year-old male patient admitted to your medical unit 72 hours ago with pyloric stenosis. A nasogastric tube placed upon admission has been on low intermittent suction ever since. Upon review of the mornings blood work, you notice that the patients potassium is below reference range. You should recognize that the patient may be at risk for what imbalance?
Probably the most common cause of metabolic alkalosis is vomiting or gastric suction with loss of hydrogen and chloride ions. The disorder also occurs in pyloric stenosis in which only gastric fluid is lost. Vomiting, gastric suction, and pyloric stenosis all remove potassium and can cause hypokalemia. This patient would not be at risk for hypercalcemia; hyperparathyroidism and cancer account for almost all cases of hypercalcemia. The nasogastric tube is removing stomach acid and will likely raise pH. Respiratory acidosis is unlikely since no change was reported in the patients respiratory status.
73-year-old man comes into the emergency department (ED) by ambulance after slipping on a small carpet in his home. The patient fell on his hip with a resultant fracture. He is alert and oriented; his pupils are equal and reactive to light and accommodation. His heart rate is elevated, he is anxious and thirsty, a Foley catheter is placed, and 40 mL of urine is present. What is the nurses most likely explanation for the low urine output
Renin is released by the juxtaglomerular cells of the kidneys in response to decreased renal perfusion. Angiotensin-converting enzyme converts angiotensin I to angiotensin II. Angiotensin II, with its vasoconstrictor properties, increases arterial perfusion pressure and stimulates thirst. As the sympathetic nervous system is stimulated, aldosterone is released in response to an increased release of renin, which decreases urine production. Based on the nursing assessment and mechanism of injury, this is the most likely causing the lower urine output. The man urinating prior to his arrival to the ED is unlikely; the fall and hip injury would make his ability to urinate difficult. No assessment information indicates he has a head injury or heart failure.
The nurse is caring for a client with severe diarrhea. The nurse recognizes that the client is at risk for developing which acid-base imbalance?
The client is at risk for developing metabolic acidosis. Metabolic acidosis is caused by diarrhea, lower intestinal fistulas, ureterostomies, and use of diuretics; early renal insufficiency; excessive administration of chloride; and the administration of parenteral nutrition without bicarbonate or bicarbonate-producing solutes (e.g., lactate).
An adult client is brought in to the clinic feeling thirsty with dry, sticky mucous membranes; decreased urine output; fever; a rough tongue; and lethargy. The nurse reconciles the client's medication list and notes that salt tablets had been prescribed. What would the nurse do next?
The client's symptoms of feeling thirsty with dry, sticky mucous membranes; decreased urine output; fever; a rough tongue; and lethargy suggest hypernatremia. The client needs to be evaluated with serum blood tests soon; a later appointment will delay treatment. It is necessary to restrict sodium intake. Salt tablets and a sodium chloride IV will only worsen this condition. A Lactated Ringer's IV is a hypertonic IV and is not used with hypernatremia. A hypotonic solution IV may be a part of the treatment, but not along with the salt tablets.
The nurse states, A patient in renal failure partially loses the ability to regulate changes in pH. What is the cause of this partial inability?
The kidneys regulate the bicarbonate level in the ECF; they can regenerate bicarbonate ions as well as reabsorb them from the renal tubular cells. In respiratory acidosis and most cases of metabolic acidosis, the kidneys excrete hydrogen ions and conserve bicarbonate ions to help restore balance. The lungs regulate and reabsorb carbonic acid to change and maintain pH. The kidneys do not buffer acids through electrolyte changes; buffering occurs in reaction to changes in pH. Carbonic acid works as the chemical medium to exchange O2 and CO2 in the lungs to maintain a stable pH whereas the kidneys use bicarbonate as the chemical medium to maintain a stable pH by moving and eliminating H+.
You are caring for a patient who is being treated on the oncology unit with a diagnosis of lung cancer with bone metastases. During your assessment, you note the patient complains of a new onset of weakness with abdominal pain. Further assessment suggests that the patient likely has a fluid volume deficit. You should recognize that this patient may be experiencing what electrolyte imbalance?
The most common causes of hypercalcemia are malignancies and hyperparathyroidism. Anorexia, nausea, vomiting, and constipation are common symptoms of hypercalcemia. Dehydration occurs with nausea, vomiting, anorexia, and calcium reabsorption at the proximal renal tubule. Abdominal and bone pain may also be present. Primary manifestations of hypernatremia are neurologic and would not include abdominal pain and dehydration. Tetany is the most characteristic manifestation of hypomagnesemia, and this scenario does not mention tetany. The patients presentation is inconsistent with hypophosphatemia.
Osmolality
The number of dissolved particles contained in fluid determines the osmolality of a solution, which influences the movement of fluid between the fluid compartments.
You are caring for a patient with a diagnosis of pancreatitis. The patient was admitted from a homeless shelter and is a vague historian. The patient appears malnourished and on day 3 of the patients admission total parenteral nutrition (TPN) has been started. Why would you know to start the infusion of TPN slowly?
The nurse identifies patients who are at risk for hypophosphatemia and monitors them. Because malnourished patients receiving parenteral nutrition are at risk when calories are introduced too aggressively, preventive measures involve gradually introducing the solution to avoid rapid shifts of phosphorus into the cells. Patients receiving TPN are not at risk for hypercalcemia or hypernatremia if calories or fluids are started to rapidly. Digestive enzymes are not a relevant consideration.
oncotic pressure
The osmotic pressure in the blood vessels due only to plasma proteins (primarily albumin) --> causes water to rush back into capillaries.Oncotic pressure is the "Pull" pulling water from the interstial fluid back into the intravascular space
1/3 of body fluid is
extracellular
The nurse is caring for a client being treated with isotonic IV fluid for hypernatremia. What complication of hypernatremia should the nurse continuously monitor for?
Treatment of hypernatremia consists of a gradual lowering of the serum sodium level by the infusion of a hypotonic electrolyte solution (e.g., 0.3% sodium chloride) or an isotonic nonsaline solution (e.g., dextrose 5% in water [D5W]). D5W is indicated when water needs to be replaced without sodium. Clinicians consider a hypotonic sodium solution to be safer than D5W because it allows a gradual reduction in the serum sodium level, thereby decreasing the risk of cerebral edema. It is the solution of choice in severe hyperglycemia with hypernatremia. A rapid reduction in the serum sodium level temporarily decreases the plasma osmolality below that of the fluid in the brain tissue, causing dangerous cerebral edema.
how is urine osmolality determined?
Urine osmolality is determined by urea, creatinine, and uric acid.
why give patients with DI vasopressin?
Vasopressin is administered to clients with diabetes insipidus a condition in which circulating ADH is deficient
newly graduated nurse is admitting a patient with a long history of emphysema. The new nurses preceptor is going over the patients past lab reports with the new nurse. The nurse takes note that the patients PaCO2 has been between 56 and 64 mm Hg for several months. The preceptor asks the new nurse why they will be cautious administering oxygen. What is the new nurses best response?
When PaCO2 chronically exceeds 50 mm Hg, it creates insensitivity to CO2 in the respiratory medulla, and the use of oxygen may result in the patient developing carbon dioxide narcosis and hypoxemia.
Both hypomagnesemia and hypocalcemia may be tested using the Chvosteks sign
You can induce Chvosteks sign by tapping the patients facial nerve adjacent to the ear. A brief contraction of the upper lip, nose, or side of the face indicates Chvosteks sign. .
pituitary gland function:
after hypothalamus makes ADH, posterior pituitary gland stores it; released when needed to conserve water.
The major anions(-) are
chloride, bicarbonate, phosphate, sulfate, and proteinate ions. Sodium is the most abundant in ECF
Normal movement of fluids through the capillary wall into the tissues depends on
hydrostatic pressure (the pressure exerted by the fluid on the walls of the blood vessel) at both the arterial and the venous ends of the vessel and the osmotic pressure exerted by the protein of plasma. The direction of fluid movement depends on the differences in these two opposing forces (hydrostatic vs. osmotic pressure).
Tetany is the most characteristic manifestation of
hypocalcemia and hypomagnesemia. Sensations of tingling may occur in the tips of the fingers, around the mouth, and, less commonly, in the feet. Hypophosphatemia creates central nervous dysfunction, resulting in seizures and coma. Hypermagnesemia creates hypoactive reflexes and somnolence. Signs of hyperkalemia include paresthesias and anxiety.
adrenal gland function
increased secretion of aldosterone, which is produced in the outer layer of the adrenal cortex aka zona glomerusa, causes sodium and water retention, and potassium loss. Vice versa
2/3 of body fluids are _______
intracellular
ECF compartment is further divided into the intravascular, interstitial, and transcellular fluid spaces:
intravascular space (the fluid within the blood vessels) contains plasma, the effective circulating volume. Approximately 3 L/6 L of blood volume in adults is made up of plasma. The remaining 3 L is made up of erythrocytes, leukocytes, and thrombocytes. The interstitial space contains the fluid that surrounds the cell and totals about 11 to 12 L in an adult. Lymph is an interstitial fluid. The transcellular space is the smallest division of the ECF compartment and contains approximately 1 L. Examples of transcellular fluids include cerebrospinal, pericardial, synovial, intraocular, and pleural fluids, sweat, and digestive secretions.
hydrostatic pressure
is in the capillaries it is the "Push" filtering fluid out of the intravascular space and into the interstitial spaces
Organs involved in homeostasis:
kidneys, lungs, heart, adrenal glands, parathyroid glands, and pituitary gland
Hematocrit levels
males 42%-52%; females 37%-47%. percentage of blood volume occupied by red blood cells. Conditions that increase the hematocrit value are dehydration and polycythemia, and those that decrease hematocrit are overhydration and anemia.
Baroceptors
monitor changes in pressure in the walls of the blood vessels, the digestive tract, urinary tract, and reproductive tract. Sympathetic stimulation constricts renal arterioles; this decreases glomerular filtration, increases the release of aldosterone, and increases sodium and water reabsorption.
Chief solutes in sweat
sodium, chloride, potassium
The major cations(+) in body fluid are
sodium, potassium, calcium, magnesium, and hydrogen ions. Potassium is most abundant in ICF
Low specific gravity suggests
that urine is too diluted
High urine specific gravity can indicate
that you have extra substances in your urine, patient is dehydrated.
Tonicity
the ability of a solution to cause a cell to gain or lose water
osmotic pressure
the external pressure that must be applied to stop osmosis
parathyroid glands function
these glands are embedded in the thyroid. They regulate calcium absorption from intestines and calcium reabsorption from the renal tubules, and bone reabsorption.
