Chapter 8
important stimulus for thirst
Angiotensin II -· Increases in response to low blood volume and low blood pressure · Renin-angiotensin mechanism contributes to nonosmotic thirst · This system is considered a backup for system if all others fail · Elevated levels of angiotensin II may lead to thirst in conditions such as CKD and CHF in which renin levels may be elevated
When explaining how carbon dioxide combines with water to form carbonic acid as part of acid-base lecture, the faculty instructor emphasized that which enzyme is needed as a catalyst for this reaction?
Carbonic anhydrase; Although CO2 is a gas and not an acid, a small percentage of the gas combines with water to form H2CO3. The reaction that generates H2CO3 from CO2 and water is catalyzed by an enzyme called carbonic anhydrase.
Isotonic solution
Cells placed in isotonic solution, which has the same effective osmolality as the ICF neither shrink nor swell - Ex of isotonic solution: 0.9% NaCl
Chvostek's sign
Cheek, facial spasm when Cheek is tapped associates with hypocalcemia
A 55-year-old male client with a history of cardiovascular disease has been admitted to the intensive care unit after recovering from cardiogenic shock. In the hours since admission, the client's arterial blood gases indicate acidosis, most likely acute lactic acidosis. Which of the following signs, symptoms, and diagnostic findings might his care team anticipate before the acid-base balance is restored? Select all that apply.
Decreased pH Cardiac dysrhythmias Decreased alertness and cognition Nausea and vomiting
A patient arrives in the ED very hypovolemic related to excretion of "at least 3 gallon jugs of urine in the past 24 hours." He describes the urine as being clear-like water. The physician suspects diabetes insipidus. The nurse should be prepared to administer which of the following medications?
Desmopressin acetate (DDAVP)
A 77-year-old female diagnosed with chronic obstructive pulmonary disease (COPD) is experiencing impaired gas exchange and CO2 retention, despite a rapid respiratory rate. Which of the following pathophysiological principles would her health care team expect if her compensatory mechanisms are working?
Her kidneys will adapt with an increase in plasma HCO3- and her pH will decrease.
A 55-year-old woman has presented to the emergency department following a panic attack. Her blood pressure, respiratory rate, and heart rate are all highly elevated, while her temperature and oxygen saturation are within normal ranges. What is the woman's body most likely doing to address the changes in pH associated with her situation?
Her kidneys will limit the amount of bicarbonate that they reabsorb.
When trying to explain the role of potassium and hydrogen related to acid-base balance, which of the following statements is accurate?
Hypokalemia stimulates H+ secretion; Hypokalemia is a potent stimulus for H+ secretion and HCO3 reabsorption.
A patient who has just had her first postoperative dinner out to celebrate her recovery from an intestinal bypass is brought to the emergency room by her spouse. He reports that the patient seems disoriented and is slurring her words. The patient did not have any alcohol with her pasta dinner. Which of the following might be the cause of her symptoms?
Lactic acidosis
A hospital patient's arterial blood gases indicate normal levels of oxygen and increased carbon dioxide. The patient's respiratory rate is 12 breaths/minute (normal 14 to 20 breaths/minute) with all other vital signs within normal range. While not evident from assessment and diagnostics, the patient's kidneys are minimizing both H+ excretion and HCO3- reabsorption. What is this client's most likely diagnosis?
Metabolic alkalosis
An 81-year-old female has a long-standing diagnosis of hypocalcemia secondary to kidney disease. She will be moving into an assisted living facility shortly. Which of the following clinical manifestations would the nursing staff at the facility likely observe in this patient?
Muscular spasms and complaints of tingling in the hands/feet
In the neurotrauma unit, a teenager with a closed head injury related to an automobile accident is experiencing high intracranial pressure (ICP). He is intubated and is on a ventilator. One treatment for this is to allow him to progress into which acid-base imbalance in an attempt to lower ICP?
Respiratory alkalosis
Following several days in an acidotic state, a hospital patient has returned to desired pH. Which of the following processes could have contributed to the resolution of the patient's health problem?
The phosphate and ammonia buffer systems in the renal tubules
antidiuretic hormone (ADH)
influences the absorption of water by kidney tubules - Without ADH, luminal membranes of the collecting ducts are almost impermeable to water, but in the presence of ADH, pores (aquaporin's) are stimulated to move into the membrane making them permeable to water - The specific water channel that is controlled by ADH is aquaporin-2 o ADH levels are controlled by ECF volume and osmolality o Osmoreceptors in the hypothalamus are capable of detecting fluctuation in ECF osmolality and can stimulate the production and release of ADH; likewise, stretch receptors that are sensitive to CP changes aid in regulation of ADH release
Clinical manifestations of hyponatremia
o Depend on the rapidity of onset and severity o s/sx may be acute as in water intoxication or insidious as in chronic hyponatremia o fingerprint edema is a sign of excess intracellular water o muscle cramps, weakness, and fatigue o GI manifestations such as nausea, vomiting, abdominal cramps and diarrhea · Seizures can occur when levels are extremely low which is d/t brain swelling and may be irreversible
Calcium
o Enters the body through the GI tract and is absorbed from the intestine under the influence of vitamin D, stored in bone, and excreted by the kidney o Provides strength and stability for the skeletal system and serves as an exchangeable source to maintain extracellular calcium levels
Causes of SIADH
o May occur as a transient condition as in a stress situation, or as a chronic condition resulting from disorders such as lung or brain tumors - Tumors, particularly bronchogenic carcinomas and cancers of the lymphoid tissue, prostate, and pancreas are known to produce and release ADH independent of normal hypothalamic control mechanisms - Other intrathoracic conditions such as advanced TB, severe pneumonia, and positive pressure breathing, may also cause SIADH - Stimuli such as surgery, pain, stress, and temperature changes are capable of triggering ADH release through action of the CNS
Thirst and Antidiuretic hormone
o Mechanisms that contribute directly to the regulation of body water and indirectly to the regulation of sodium are thirst and ADH o Thirst is primarily a regulator of water intake and ADH a regulator of water output o Both are responsible to changes in extracellular osmolality and the resultant effective circulating volume
Sodium Balance
o Most abundant cation in the body o Normal is 135-145 o Resting cell membrane is relatively impermeable to sodium; sodium that enters the cell is transported out of the cell against a gradient by the Na/K ATPase membrane pump o Main function: regulating the ECF volume
Syndrome of Inappropriate Antidiuretic Hormone (SIADH)
o Results from a failure of the negative feedback system that regulates the release and inhibition of ADH o ADH secretion continues even when serum osmolality is decreased, causing marked water retention and dilutional hyponatremia
A male patient with a history of heavy alcohol use has been admitted to hospital for malnutrition and suspected pancreatitis. The patient's diagnostic workup suggests alcoholic ketoacidosis as a component of his current health problems. He is somewhat familiar with the effect that drinking has had on his nutrition and pancreas but is wholly unfamiliar with the significance of acid-base balance. How best could his care provider explain the concept to him?
"The chemical processes that take place throughout your body are thrown off very easily when your body is too acidic or not acidic enough.
A nurse in a medical unit has noted that a client's potassium level is elevated at 6.1 mEq/L. The nurse has notified the physician, removed the banana from the client's lunch tray, and is performing a focused assessment. When questioned by the client for the rationale for these actions, which of the following explanations is most appropriate?
"Your potassium level is high, and so I need you let me know if you feel numbness, tingling, or weakness."
Manifestations of hypokalemia
- Alterations in renal, gastrointestinal, cardiovascular, and neuromuscular function - s/sx associated with GI function including anorexia, N/V - most serious are those affecting cardiovascular function · postural hypotension is common · ECG changes including PR prolongation, ST segment depression, flattening of the T wave, and appearance of a prominent U wave - Complaints of weakness, fatigue, muscle cramps (particularly during exercise) - Muscle paralysis with life threatening respiratory insufficiency can occur
Lab findings in SIADH
- Are those of dilutional hyponatremia - Urine osmolality is high and serum osmolality is low - Urine output decreases despite adequate or increased fluid intake - Hematocrit and the plasma sodium and BUN levels are all decreased because of the expansion of the ECF volume
Causes of hypernatremia
- Excessive water losses o Watery diarrhea, excessive sweating, increased respirations because of conditions such as tracheobronchitis, hypertonic tube feedings, diabetes insipidus - Decreased water intake - Lack of access, oral trauma or inability to swallow, impaired thirst sensation, withholding water for therapeutic reasons, unconsciousness or inability to express thirst - Excessive sodium intake - Rapid or excessive administration of sodium containing parenteral solutions, near drowning in salt water
The ICU nurse is concerned with her patient's arterial blood gas (ABG) results—especially the pH 7.30; and PCO2 49 mm Hg. The nurse interprets these ABG results to mean respiratory acidosis. The nurse knows which of the following are clinical manifestations of respiratory acidosis? Select all that apply.
- Headache with complaints of blurred vision - Muscle twitching
Causes of Hypocalcemia
- Impaired ability to mobilize Ca+ from bone stores - Hypoparathyroidism, Resistance to the actions of PTH, Hypomagnesaemia o Decreased intake or absorption - Malabsorption, Vitamin D deficiency, Failure to activate, Liver disease, Kidney disease, Medications that impair activation of vitamin D (phenytoin) o Abnormal losses of Ca+ from kidney - Renal failure and Hyperphosphatemia - Increased protein binding or chelation such that grater proportions of Ca+ are in non-ionized form - Increased pH, Increased fatty acids, Rapid transfusion of citrated blood - Soft tissue sequestration - Acute pancreatitis
Management of Diabetes Insipidus
- Maintain balance on permitting ingestion of water - Preferred drug- desmopressin acetate (DDAVP); oral anti-diabetic agent-chlorpropramide may be used to stimulate ADH release - Both neurogenic and nephrogenic DI respond partially to the thiazide diuretics
osmosis
- Movement of water across a semipermeable membrane (one that is permeable to water but impermeable to most solutes) - Water crosses the cell membrane by osmosis using special protein channels called aquaporin's - As with particles, water diffuses down its concentration gradient, moving from the side of the membrane with the lesser number of particles and greater concentration of water to the side with the greater number of particles and lesser concentration of water - As water moves across the semipermeable membrane, it generates a pressure called the osmotic pressure—the magnitude of the osmotic pressure represents the hydrostatic pressure needed to oppose the movement of water across the membrane
Manifestations of Hypocalcemia
- Neuromuscular (increased excitability) - Parasthesias, especially numbness and tingling, Skeletal muscle cramps, Abdominal spasms and cramps, Hyperactive reflexes, Carpopedal spasm, Tetany, Laryngeal spasm, Positive chvostek and trousseau signs - Cardiovascular - Hypotension, s/sx of cardiac insufficiency, failure to respond to drugs that act by calcium mediated mechanisms, prolonged QT - Skeletal (chronic deficiency) - Osteomalacia, bone pain, deformities, fracture
Gains and Losses of potassium
- Normally derived from dietary sources - Kidneys are main source of potassium loss - Approximately 90-95% of potassium losses occur in the urine with the remainder being lost in feces or sweat
Neurogenic (central) DI
- Occurs because of a defect in the synthesis or release of ADH - loss of 80%-90% of ADH secreting neurons necessary before polyuria becomes evident - temporary neurogenic DI may follow head injury or surgery - acquired neurogenic DI- caused by drugs such as lithium, potassium depletion, or chronic hypercalcemia
tonicity
- Refers to the tension or effect that the effective osmotic pressure of a solution with impermeable solutes exerts on cell size because of water movement across the cell membrane - A change in water content causes cells to shrink or swell o When ECF levels of urea are elevated, ICG levels are also elevated - Urea is therefore considered to be an ineffective osmole - Solutions to which body cells are exposed can be classified as isotonic, hypotonic or hypertonic depending on whether they cause cells to swell or shrink
Extracellular fluid compartments
- Remaining one third of body water - Contains all the fluids outside the cells, including those in the interstitial or tissue spaces and blood vessels - Includes blood plasma and interstitial fluids, contains large amounts of sodium and chloride and moderate amounts of bicarbonate but only small quantities of potassium, magnesium, calcium, and phosphorus - Contains blood, which is essential to the transport of substances such as electrolytes, gases, nutrients, and waste products throughout the body
Mechanism of Syndrome of inappropriate antidiuretic hormone
- When caused by positive pressure ventilation it is due to activation of baroreceptors - Disease and injury to the CNS can cause direct pressure on or direct involvement of the hypothalamic-posterior pituitary structures · Ex: brain tumors, hydrocephalus, head injury, meningitis, and encephalitis · HIV is also an established cause
Hypotonic solution
- When cells are placed in hypotonic solution, which has a lower effective osmolality than the ICF, they swell as water moves into the cell - Ex: 5% dextrose in water
Renin
- a small protein enzyme that is released by the kidney in response to changes in arterial pressure, the GFR, and amount of sodium in the tubular fluid · most of the renin that is released leaves the kidney and enters the bloodstream, where it interacts enzymatically to convert a circulating plasma protein angiotensinogen to angiotensin I
Aldosterone
- acts at the level of the cortical collecting tubules of the kidneys to increase sodium reabsorption while increasing potassium elimination - Sodium retaining action of aldosterone can be inhibited with potassium-sparing diuretics
An ECG technician is performing an ECG on a hospital patient who has developed hypokalemia secondary to diuretic use. Which of the following manifestations of the client's health problem will the technician anticipate on the ECG?
A prominent U wave and a flattened T wave
Which of the following individuals are at risk of developing metabolic alkalosis? Select all that apply.
- A 70-year-old woman who has taken two tablespoons of baking soda to settle her "sour stomach" - A hospital patient who is on nasogastric suction following gastric surgery - A 20-year-old male who has been regularly inducing himself to vomit following binge eating
Treatment of Respiratory Alkalosis
- Because respiratory alkalosis is typically a compensatory state, it should not be treated directly - Thus, treatment should focus on measures to correct the underlying cause - Hypoxia may be corrected by administration of supplemental oxygen - Changing vent settings may be used to prevent or treat respiratory alkalosis in persons who are mechanically ventilated - People with hyperventilation may benefit from reassurance, rebreathing from a paper bag during symptomatic attacks, and attention to the psychological stress
Manifestations of Respiratory Acidosis
- Blood pH, CO2, HCO3- · pH decreased, pCO2 (primary) increased), HCO3 (compensatory) increased · Dilation of cerebral vessels and depression of neural function, headache, weakness, behavior changes- confusion, depression, paranoia, hallucinations, tremors, paralysis, stupor and coma · Warm and flushed skin - Signs of compensation · Acid urine
manifestations of respiratory alkalosis
- Blood pH, CO2, HCO3- · pH increased, pCO2 (primary) decreased, HCO3- (compensatory) decreased · Constriction of cerebral vessels and increased neuronal excitability, dizziness, panic, lightheadedness, tetany, numbness and tingling of fingers and toes, positive Chvostek and Trousseau signs, seizures -Cardiac arrhythmias
Manifestations of Metabolic Alkalosis
- Blood pH, HCO3-, CO2 · pH increased, HCO3- (Primary) increased, PCO2 (compensatory) increased · Confusion, hyperactive reflexes, tetany, convulsions · Hypotension, arrhythmias · Respiratory acidosis because of decreased respiratory rate - Signs of compensation · Decreased rate and depth of respiration, increased urine PH
diabetes insipidus (DI)
- Caused by a deficiency of or a decreased response to ADH - Inability to concentrate urine during periods of water restriction, and the excretion of large volumes of urine (3-20 L/day), depending on the degree of ADH deficiency - Usually accompanied by excessive thirst - As long as thirst mechanism is normal fluid is readily available, there is little to no alteration in the fluid levels of people with DI
Intracellular fluid compartments
- Consists of fluid contained within all the billions of cells in the body - Larger of the two compartments with approximately two thirds of the body water in health adults - Contains almost no calcium; small amounts of sodium, chloride, bicarbonate, and phosphorus; moderate amounts of magnesium; and large amounts of potassium - regulated by proteins and organic compounds within the body cells and by water and solutes that move between the ECF and ICF
Thirst
- Controlled by the thirst center in the hypothalamus - Two stimuli for true thirst based on water need - Cellular dehydration caused by an increase in ECF osmolality - Decrease in blood volume, which may or may not be associated with a decrease in serum osmolality - Sensory neurons, called osmoreceptors, respond to changes in ECF osmolality by swelling or shrinking - Thirst is one of the earliest symptoms of hemorrhage and is often present before other signs of blood loss appear
Causes of Respiratory Acidosis
- Depression of respiratory center · Drug overdose, head injury - Lung disease · Bronchial asthma, emphysema, chronic bronchitis, pneumonia, pulmonary edema, respiratory distress syndrome - Airway obstruction, Disorders of Chest Wall and Respiratory Muscles · Paralysis of respiratory muscles, chest injures, kyphoscoliosis, extreme obesity, treatment with paralytic drugs - Breathing Air with high CO2 content
treatment of metabolic alkalosis
- Directed toward correcting cause of the condition - Chloride deficit requires correction - Potassium chloride is the treatment of choice when there is an accompanying K+ deficit - When KCl is used as a therapy, the Cl- anion replaces the HCO3- anion and the K+ corrects the potassium deficit, allowing the kidneys to retain H+ while eliminating K+ - Fluid replacement with normal saline or one-half normal saline often is used in treatment of volume contraction alkalosis
Causes of Respiratory Alkalosis
- Excessive Ventilation · Anxiety and psychogenic hyperventilation, hypoxia and reflex stimulation of ventilation, lung disease that causes a reflex stimulation of ventilation, stimulation of respiratory center, elevated blood ammonia level, salicylic toxicity, encephalitis, fever, mechanical ventilation
Causes of metabolic alkalosis
- Excessive gain of bicarbonate or Alkali · Ingestion or administration of NaHCO3-, administration of hyperalimentaion solutions containing acetate, administration of parenteral solutions containing lactate, administration of citrate containing blood transfusions - Excessive loss of Hydrogen Ions · Vomiting, gastric suction, binge-purge syndrome, potassium deficit- diuretic therapy or hyperaldosteronism, milk-alkali syndrome - Increased Bicarbonate Retention · Loss of chloride with bicarbonate retention - Volume contraction · Loss of body fluids, diuretic therapy
polydipsia
- Excessive thirst - Symptomatic/true thirst o Inappropriate or false thirst that occurs despite normal levels in body - Compulsive water drinking
Vitamin D
- Functions as a hormone - Acts to sustain normal plasma levels of calcium and phosphorus by increasing their absorption from the intestine and is also necessary for normal bone formation - Evidence that vitamin D controls parathyroid gland growth and suppresses the synthesis and secretion of PTH - Low calcium levels lead to an increase in PTH, which then increases vitamin D activation - A lowering of plasma phosphate also augments vitamin D activation
Mechanisms that contribute to edema
- Increased capillary filtration pressure - Decrease capillary colloidal osmotic pressure - Increase capillary permeability - Obstruct lymphatic flow
Manifestations of hypophosphatemia
- Intention tremor, ataxia, Parasthesias, confusion, stupor, coma, seizures - Muscle weakness, joint stiffness, bone pain, osteomalacia · Blood disorders - Hemolytic anemia, platelet dysfunction with bleeding disorders, impaired WBC function
Hypernatremia
- Levels >145 mEq/L - Characterized by hypertonicity of ECF and almost always causes cellular dehydration
Parathyroid hormone
- Major regulator of plasma calcium and phosphorus and is secreted by the parathyroid glands - Secretion, synthesis, and action of PTH are also influenced by magnesium · Magnesium serves as a cofactor in the generation of cellular energy and is important in the function of second messenger systems, allows for nerve conduction, ion transport, and potassium and calcium channel activity · Magnesium blocks the outward movement of potassium in cardiac cells; when magnesium levels are low, the channel permits outward flow of potassium; acts on calcium channels to inhibit the movement of calcium into cells · Severe and prolonged hypomagnesaemia can markedly inhibit PTH levels - Main function: maintain the calcium concentration of the ECF · Performs this function by promoting the release of calcium from the bone, increasing the activation of vitamin D as a means of enhancing intestinal absorption of calcium, and stimulating calcium conservation by the kidney while increase phosphate excretion - Acts on the bone to accelerate the mobilization and transfer of calcium to the ECF - Actions of PTH require normal levels of both vitamin D and magnesium - Activation of vitamin D by the kidney is enhanced in the presence of PTH - Through activation of vitamin D, PTH increases intestinal absorption of calcium and phosphorus as well as acts on the kidney to increase tubular reabsorption of calcium and magnesium while increasing phosphorus elimination · the accompanying increase in phosphorus elimination ensures that the phosphorus released from bone does not produce Hyperphosphatemia and increases the risk of soft tissue deposition of calcium phosphate crystals
Treatment of inappropriate antidiuretic hormone
- Mild cases: fluid restriction · If this is not sufficient, diuretics such as mannitol and Lasix may promote diuresis · Medications to inhibit the action of ADH on the renal collecting ducts - Severe cases (water intoxication): hypertonic NaCl may be administered
Diffusion
- Movement of charged or uncharged particles along a concentration gradient - All molecules and ions, including water and dissolved molecules, are in constant random motion - It is the motion of these particles, each colliding with one another, that supplies the energy for diffusion - Particles move from an area of higher concentration to one of lower concentration
A patient who has had a prolonged period of nasogastric (NG) suctioning following colon surgery is experiencing electrolyte imbalances. The magnesium level is low (1.2 mg/dL). Knowing that magnesium deficiency occurs in conjunction with low calcium levels, the nurse should assess the patient for which of the following clinical manifestations of hypocalcaemia? Select all that apply.
- Personality changes - Hyperactive reflexes - Increase in ventricular arrhythmias
Regulation of Potassium
- Renal mechanisms that conserve or eliminate potassium · Major route for elimination is the kidney · Regulation of elimination is controlled by secretion from the blood into the tubular filtrate rather than reabsorption (different than other electrolytes) · Filtered in the glomerulis, reabsorbed along with sodium and water · Aldosterone plays essential role in regulation § Transcellular shift between the ICF and ECF compartments · Excess potassium is temporarily shifted into RBCs and other cells such as those of muscle, liver, and bone · Movement is controlled by the function of Na/K ATPase pump
A patient who overdosed on aspirin is brought to the emergency department. The nurse caring for this patient should anticipate which of the following clinical manifestations? Select all that apply.
- Respiratory rate of 40 - ABG report: pH 7.50, PCO2 31 mm Hg, and HCO3 level 19 mmol/L.
Hyperphosphatemia
- Serum level >4.5mg/dL in adults and >5.4mg/dL in children
Gains and losses of sodium
- Sodium normally enters through the GI tract and is eliminated by the kidneys or lost from GI tract or skin - Intake is normally derived from dietary sources - Most losses occur through the kidneys which are extremely efficient in regulating sodium output when sodium intake is limited or conservation is needed - kidneys are able to reabsorb almost all of the sodium that has been filtered by the glomerulis—this results in essentially sodium-free urine - sodium leaves the skin through sweat glands
Effective circulating volume
- Vascular bed that perfuses the body - A low effective circulating volume activates feedback mechanisms that produce an increase in renal sodium and water retention, and a high effective circulating volume triggers feedback mechanisms that decrease sodium and water retention - Monitored by a number of sensors that are located in both the vascular system and the kidney - Baroreceptors: respond to pressure-induced stretch of the vessel walls
metabolic acidosis
- a reduction of pH because of a decrease in HCO3- - Most common acid-base disorder - Body compensates for the decrease in pH by increasing the respiratory rate in an effort to decrease PCO2 and H2CO3 levels
three forms of carbon dioxide transport
- as a dissolved gas (dissolved in the plasma) - as bicarbonate - as carbaminohemoglobin
Hypotonic (dilutional) hyponatremia
- caused by water retention; most common o Classified as hypovolemic, euvolemic, or hypervolemic based on accompanying ECF fluid volumes - Diuretic therapy can cause either hypovolemic or euvolemic hyponatremia
Respiratory acidosis:
- characterized by a decrease in pH reflecting a decrease in ventilation and an increase in PCO2
Respiratory disorders
- disorders involve an alteration in PCO2 reflecting an increase or decrease in alveolar ventilation
Ionized Calcium
- free to leave the vascular compartment and participate in cellular functions - total plasma calcium level fluctuates with changes in plasma albumin and pH - serves a number of functions · participates in many enzyme reactions · exerts an important effect on membrane potentials and neuronal excitability · necessary for contraction in skeletal, cardiac, and smooth muscle · participates in the release of hormones, neurotransmitters, and other chemical messengers · influences cardiac contractility and automaticity through the slow calcium channels · essential for blood clotting
Causes of hypercalcemia
- hyperparathyroidism o increased intestinal absorption: excessive vitamin D, excessive calcium in diet - increased bone reabsorption - increased levels of PTH - malignant neoplasms - prolonged immobilization - decreased elimination - thiazide diuretics - lithium therapy
Hyponatremia
- most common electrolyte disorder seen particularly in older adults - May be d/t: decrease in renal function, limitations in sodium conservation - can present as hypotonic or hypertonic state because of the effects of osmotically active particles such as glucose
Hypovolemic hypotonic hyponatremia
- occurs when water is lost along with sodium resulting in low plasma level, but to a lesser extent; may be caused by excessive sweating in hot weather, loss of sodium from GI tract; common complication of adrenal insufficiency and is attributed to a decrease in aldosterone levels
Hypertonic hyponatremia
- results from an osmotic shift of water from the ICF to the ECF compartment such that occurs in hyperglycemia - Sodium in the ECF becomes diluted as water moves out of cells in response to osmotic effects of hyperglycemia
Hypervolemic hypotonic hyponatremia
- retention of water with dilution of sodium while maintaining the ECF volume within a normal range; usually a result of SIADH; risk increased during post-op period
Which of the following individuals would be considered to be at risk for the development of edema? Select all that apply.
-An 81-year-old man with right-sided heart failure and hypothyroidism - A 34-year-old industrial worker who has suffered extensive burns in a job-related accident - A 22-year-old female with hypoalbuminemia secondary to malnutrition and anorexia nervosa
Clinical manifestations of hypocalcemia
-Increased neuromuscular excitability (Paresthesias, muscle twitching/cramping, tetany, hyperactive reflexes, trousseau/chvostek signs) -Cardiac arrhythmias, personality changes, increase in ventricular rhythms
Manifestations of hyperphosphatemia
-Parasthesias, tetany - Hypotension, cardiac arrhythmias
The nurse is providing teaching to a student nurse about how antidiuretic hormone (ADH) plays a central role in the reabsorption of water by the kidneys. The nursing student is correct to place the following components of the homeostatic action of ADH in the correct sequence. Use all the options.
1- ADH is synthesized by cells in the supraoptic and paraventricular nuclei of the hypothalamus. 2- ADH is transported along a neural pathway to the posterior pituitary gland. 3- Serum osmolality increases. 4- Stored ADH is released into circulation. 5- Aquaporins are inserted into tubular cell membranes.
Place the following stages of the hydrogen ion elimination and bicarbonate conservation in the proximal tubules of the nephrons in the ascending chronological order. Use all the options.
1- H+ is secreting into the tubular fluid. 2- H+ combines with filtered HCO3-. 3- Carbonic acid is produced. 4- CO2 and H2O are produced.
Vitamin D is integral to the regulation of calcium and phosphate levels. Put the following steps in the action of vitamin D into the correct sequence. Use all the options.
1- Vitamin D is present in the skin or intestine. 2- Vitamin D is concentrated in the liver. 3- Vitamin D is transported to the kidneys. 4- Calcitriol is produced. 5- Absorption of calcium from the intestine increases.
Treatment of Metabolic Acidosis
1. treat underlying cause 2. bicarb or lactate or acetate can be admin (lactate and acetate are bicarb precursors) -- ONLY DO IF ACIDOSIS IS DUE TO BICARB LOSS
During a period of extreme excess fluid volume, a renal dialysis patient may be administered which type of IV solution to shrink the swollen cells by pulling water out of the cell?
3% sodium chloride
The nurse is caring for the following group of clients. Select the most likely to be diagnosed with respiratory alkalosis
A 26-year-old female with anxiety who has been hyperventilating
A nurse suspect that a client with a plasma magnesium level of 1.2 may have which condition in their history?
Abuse of alcohol
The nurse is caring for a group of clients at risk for ketoacidosis. Which of these problems in the clients histories does the nurse recognize can trigger ketoacidosis? Select all that apply
Alcoholism, extreme carbohydrate restriction, starvation state, uncontrolled diabetes
Protein bound calcium
Approximately 40% of ECF Ca+ is bound to plasma proteins, mostly albumin and cannot diffuse or pass through the capillary wall to leave the vascular compartments
Manifestations of Metabolic acidosis
Blood pH, HCO3-, CO2 · pH decreased, HCO3- (primary) decreased, PCO2 (compensatory) decreased · Anorexia, nausea and vomiting, abdominal pain · Weakness, lethargy, general malaise, confusion, stupor, coma, depression of vital functions · Peripheral vasodilation, decreased HR, cardiac arrhythmias · Warm and flushed · Bone disease (chronic acidosis) - Signs of compensation · Increased rate and depth of respiration (Kussmaul breathing), hyperkalemia, acid urine, increased ammonia in urine
A nurse is reviewing problems of increased capillary permeability with a group of nursing students. The nurse knows that the students understand the concept when they indicate that which condition can increase capillary permeability and cause edema? Select all that apply
Burns, allergic reactions, inflammation
how do the kidneys regulate pH
By eliminating or replenishing H+ by altering plasma HCO3 (bicarb) concentrations
How do the lungs regulate pH?
By eliminating or replenishing H+ in the body by altering CO2 elimination
The nurse in labor and delivery unit is administering IV magnesium to a patient with preeclampsia. For which of the following complications does the nurse monitor the patient?
Cardiac arrhythmias
Respiratory Alkalosis
Caused by hyperventilation or respiratory rate in excess of that needed
A patient has been diagnosed with a brain tumor that cannot be removed surgically. During each office visit, the nurse will be assessing the patient for syndrome of inappropriate antidiuretic hormone (SIADH). Which of the following assessments would alert the clinic nurse that the patient may be developing this complication?
Complaints that his urine output is decreased, no edema noted in ankles, and increasing headache
The nurse caring for the client with respiratory alkalosis and renal compensation determines which of these diagnostic findings is consistent with this disorder?
Decreased PCO2 and HCO3, and increased pH
The nurse is caring for a client with diabetic ketoacidosis. Which assessment finding is characteristic of metabolic acidosis?
Deep and rapid respirations
The nurse is caring for a patient who Receives hemodialysis. The nurse knows that hemodialysis involves movement of charger and charge particles along a concentration gradient. Which of the following best describes this process?
Diffusion
Treatment of Respiratory Acidosis
Directed towards improving ventilation; in severe cases, mechanical ventilation may be necessary
The nurse is caring for a patient with the tumor obstructing the lymphatic system. For which of the following consequences does this nurse assess?
Fluid accumulating in the interstitial spaces distal to the tumor
A client is brought to the emergency department with complaints of shortness of breath. Assessment reveals a full, bounding pulse, severe edema, and audible crackles in lower lung fields bilaterally. What is the client's most likely diagnosis?
Fluid volume excess
A 14-year-old boy, appearing to be intoxicated, is brought to the emergency room by ambulance. The EMTs report that the boy has denied consuming anything out of the ordinary, but an open antifreeze container was found in the boy's room. Which of the following is likely to be used to treat the patient's symptoms?
Fomepizole
You are volunteering in the medical tent of a road race on a hot, humid day. A runner who has collapsed on the road is brought in with the following symptoms: sunken eyes, a body temperature of 100°F, and a complaint of dizziness while sitting to have his blood pressure taken (which subsides upon his lying down). These are signs of a fluid volume deficit. Which of the following treatments should be carried out first?
Give him an electrolyte solution by mouth.
The nurse is caring for a client who takes lithium for his bipolar disorder. The nurse carefully observes the client for which potential electrolyte imbalance?
Hypercalcemia; lithium has been shown to cause hyperparathyroidism and hypercalcemia
When caring for a patient with hypomagnesemia, the nurse evaluates electrolytes are commonly associated with which of the following conditions?
Hypocalcemia
The nurse is caring for a patient with ketoacidosis, who is complaining of increasing lethargy and occasional confusion following several weeks of rigid adherence to a carbohydrate-free diet. The nurse understands which of the following phenomena is most likely occurring?
In the absence of carbohydrate energy sources, her body is metabolizing fat and releasing ketoacids.
A client with poorly controlled diabetes mellitus presents to the emergency department with suspected ketoacidosis. Which of the following diagnostic results would most likely confirm this diagnosis?
Increased anion gap, base deficit
The Edema of venous thrombosis is related to which of the following?
Increased capillary pressure
How can someone with metabolic acidosis attempt to compensate?
Increased ventilations
A nurse is providing care for a client who has been diagnosed with metabolic alkalosis after several days of antacid use. Which of the following treatments should the nurse prepare to give?
Intravenous administration of KCl solution
The nurse is administering medications to a patient on the cardiac unit. Giving which of the following medications causes the nurse to be on alert for hypokalemia
Loop diuretic
A 31-year-old client with a diagnosis of end-stage liver failure has been admitted to the intensive care unit of a hospital. Arterial blood sampling indicates that the man has an acid-base imbalance. Which of the following situations is most likely to result in an inappropriate pH?
Low albumin and plasma globulin levels
When caring for a patient with diabetes insipidus, the nurse plans to evaluate which of the following laboratory studies?
Measurement of antidiuretic hormone and plasma and urine osmolality
The nurse is caring for a client with worsening respiratory acidosis. Which of these interventions does the nurse anticipate if the clients condition continues to deteriorate?
Mechanical ventilation
When caring for a group of clients, which of these individuals does the nurse recognize has an acid-based disturbance or compensation may result in decreased respiration?
Metabolic alkalosis
A 26-year-old male patient with a diagnosis of schizophrenia has been admitted with suspected hyponatremia after consuming copious quantities of tap water. Given this diagnosis, what clinical manifestations and lab results should the nurse anticipate the patient will exhibit?
Muscle weakness, lethargy, and headaches.
A 34-year-old male client has diagnoses of liver failure, ascites, and hepatic encephalopathy secondary to alcohol abuse. The client's family is questioning the care team as to why his abdomen is so large even though he is undernourished and emaciated. Which of the following statements most accurately underlies the explanation that a member of the care team would provide the family?
Normally small transcellular fluid compartment, or third space, is becoming enlarged.
Recognizing the prevalence and incidence of dehydration among older adults, a care aide at a long-term care facility is in the habit of encouraging residents to drink even though they may not feel thirsty at the time. Which of the following facts underlies the care aide's advice?
Older adults often experience a decrease in the sensation of thirst, even when serum sodium levels are high.
The nurse is caring for a client with metabolic alkalosis. Which of these arterial blood gas results support this diagnosis?
PH of 7.50 and HCO3 of 45
A 52-year-old patient has just passed a kidney stone and has high levels of calcium in her urine. Blood tests show high levels of calcium in her blood as well. What subsequent lab results would be most likely to distinguish between primary hyperparathyroidism and hypercalcemia of malignancy?
Parathyroid hormone level
Hypokalemia
Potent stimulus for H+ secretion and HCO3 reabsorption
A renal failure patient with severe hyperkalemia (K+ level 7.2 mEq/L) has just been admitted to the nursing unit. Given the severity of this situation, the nurse should be prepared to administer which intravenous infusion stat?
Regular insulin infusion, rate dependent on lab values
Edema
Represents an increase in interstitial fluid volume
Hypophosphatemia
Serum level <2.5 mg/dL in adults and <4.0 mg/dL in children
A 77-year-old female hospital patient has contracted Clostridium difficile during her stay and is experiencing severe diarrhea. Which of the following statements best conveys a risk that this woman faces?
She is susceptible to isotonic fluid volume deficit.
When caring for patients with the storage of sodium balance, the nurse asked the provider which of the following findings are consistent with hypernatremia?
Sodium of 158 and serum osmolality of 320
A 56-year-old female hospital patient with a history of alcohol abuse is receiving intravenous (IV) phosphate replacement. Which of the following health problems will this IV therapy most likely resolve?
The client is acidotic and has impaired platelet function.
The nurse is explaining to a patient about his parathyroid disorder. Which of the following does the nurse relate to the client regarding the relationship between parathyroid hormone and calcium?
When plasma calcium is increased, parathyroid hormone is inhibited and calcium is deposited in the bones
Acidosis
addition of excess H+ ions
A patient with ESRD comes into the emergency department in severe acidosis. The nurse notes that the respiratory rate is 36 breaths/minute. The nurse understands the pathophysiology of this response and explains to the student nurse that the patient's
chemoreceptors in the carotid and aortic bodies have noticed the pH change and altered the ventilator rate.
Complexed (chelated) calcium
complexed with substances such as citrate, phosphate, and sulfate
Metabolic Alkalosis
elevation of pH because of increased HCO3- levels
renin-angiotensin-aldosterone system
exerts its action through angiotensin II and aldosterone
Management of Diabetes Insipidus
give meds-vasopressin, synthetic ADH. monitor fluid and electrolytes.
Trosseau's sign
hand spasm when bp cuff inflated
A community health nurse who is attending a marathon recognizes which of the following types of hypotonic hyponatremia is likely when a patient reports muscle weakness, cramping, and general fatigue in spite of adequate water hydration during the run?
hypovolemic
Respiratory alkalosis:
involves an increase in PH resulting from an increase in alveolar ventilation and a decrease in PCO2
Nephrogenic DI
kidneys don't respond properly to ADH
Tubular Buffer Systems
o Because an extremely acidic urine filtrate would be damaging to structures in the urinary tract, a minimum urine pH is about 4.5. Once the urine pH reaches this level of acidity, H+ secretion ceases. This limits the amount of unbuffered H+ that an be eliminated by the kidney o When the amount of free H+ secreted into the tubular fluid threatens to cause the pH of the urine to become too acidic, it must be carried in another form. This is accomplished by combining H+ ions with intratubular buffer systems: - phosphate buffer system - ammonia buffer system
transcellular H+/K+ exchange system
o Both H+ and K+ are positively charged and both ions move freely between the ICF and ECF o When excess H+ is present in the ECF, it moves into the ICF in exchange for K+ and when excess K+ is present in the ECF, it moves into the ICF for exchange for H+
Isotonic Fluid volume deficit
o Decrease in the ECF including circulating blood volume o Results when water and electrolytes are lost in isotonic proportions o Almost always caused by a loss of body fluids and accompanied by decrease in fluid intake o Can occur d/t loss of GI fluids, polyuria, or sweating because of fever or exercise o Fluid intake may be reduced d/t lack of access, impaired thirst, unconsciousness, oral trauma, impaired swallowing, or neuromuscular problems that prevent fluid access
Causes of metabolic acidosis
o Increased production of fixed metabolic acids or ingestion of fixed acids such as salicylic acid o Inability of the kidneys to excrete the fixed acids produced from normal metabolism o Excessive loss of bicarbonate through the kidneys or GI tract o Increased plasma Cl- concentration
Isotonic fluid volume excess
o Isotonic expansion of the ECF compartment with increases in interstitial and vascular volumes o Almost always results from an increase in total body sodium that is accompanied by a proportionate increase in body water o Common causes: disorders of renal function, heart failure, liver failure, and corticosteroid excess o Characterized by a weight gain over short period of time
Hydrogen ion elimination and bicarbonate conservation
o Kidneys regulate pH by excreting excess H+, reabsorbing HCO3 and producing new HCO3-. o Bicarbonate is freely filtered in the glomerulus and reabsorbed in the tubules
Phosphorus
o Majority is contained in the bone o Regulated by the kidneys, which eliminate or conserve phosphate as serum levels change o Serum levels of calcium and phosphate are reciprocally regulated to prevent the damaging deposition of calcium phosphate crystals in the soft tissues of the body o Many of the manifestations of Hyperphosphatemia reflect a decrease in serum calcium levels o Exists in two forms- organic and inorganic o Plays major role in bone formation, essential to certain metabolic processes including the formation of ATB and enzymes needed for metabolism of glucose, fat, and protein o Necessary component of several vital parts of the cell, being incorporated into nucleic acids of DNA and RNA o Serves as an acid base buffer
Respiratory Acidosis
o Occurs in conditions that impair alveolar ventilation and cause an increase in plasma PCO2, also known as hypercapnia along with a decrease in pH o Impaired ventilation can occur as the result of decreased respiratory drive, lung disease, or disorders of chest wall and respiratory muscles
Manifestations of hypercalcemia
o Polyuria, polydipsia, flank pain, s/sx of acute and chronic renal insufficiency, signs of kidney stones o Anorexia, N/V, constipation o Muscle weakness and atrophy, ataxia, loss of muscle tone o Osteopenia, osteoporosis o Lethargy, personality and behavioral changes, stupor and coma o Hypertension, shortening of the QT interval o AV blocks
Metabolic Alkalosis
o Systemic disorder caused by an increase in plasma pH because of a primary excess in HCO3 o Can be caused by factors that generate a loss of fixed acids or gain of bicarbonate and those that maintain the alkalosis by interfering the excretion of the excess bicarbonate
bicarbonate buffer system
o Uses H2CO3 as its weak acid and a bicarbonate salt such as sodium bicarbonate as its weak base o Particularly efficient system because its components can be readily added or removed from the body o Metabolism provides an ample supply of CO2 which can replace any H2CO3 that is lost when excess base is added, and CO2 can be readily eliminated when excess acid is added
A terminally ill cancer patient with metastasis to the bone has been admitted with elevated calcium levels (hypercalcemic crisis). The patient is very lethargic and exhibiting muscle flaccidity. The nurse should be prepared to administer (Select all that apply.)
pamidronate, a bisphosphonate., gallium nitrate, a gallium salt of nitric acid, prednisone, a corticosteroid.
subdivisions of ECF
plasma compartment, interstitial fluid compartment, transceullular compartment
Angiotensin II
powerful regulator of aldosterone, a hormone secreted by the adrenal cortex
Metabolic disorders
produce an alteration in the plasma HCO3- concentration and result form the addition to or loss from the ECF of nonvolatile acid or alkali
Angiotensin I
rapidly converted to angiotensin II in the small blood vessels of the lung · Acts directly on the renal tubules to increase sodium reabsorption · Constricts renal blood vessels, thereby decreasing the GFR and slowing renal blood flow so that less sodium is filtered and more is absorbed
Atrial natriuretic peptide (ANP)
released from cells in the atria of the heart; released in response to atrial stretch and overfilling, increases sodium excretion by the kidney, which in turn pulls out more water
Alkalosis
removal of excess H+ ions from body fluids (usually compensatory)
Sympathetic nervous system:
responds to changes in arterial pressure and blood volume by adjusting the GFR and thus the rate at which sodium is filtered from the blood
Euvolemic or normovolemic hypotonic hyponatremia
retention of water with dilution of sodium while maintaining the ECF volume within a normal range; usually a result of SIADH; risk increased during post-op period
Aquaporins
water channel proteins
Hypercalcemia
· >10.5 mg/dL · results when calcium movement into the circulation overwhelms the calcium regulatory hormones or the ability of the kidney to remove excess ions
causes of hyperphosphatemia
· Acute phosphate overload o Laxatives and enemas containing phosphorus, IV phosphate supplementation · Intracellular to extracellular shift o Massive trauma, heat stroke, seizures, rhabdomyolosis, tumor lysis syndrome, potassium deficiency · Impaired elimination o Kidney failure, hypoparathyroidism
Hypodipsia
· Decreased ability to sense thirst- commonly associated with hypothalamic lesions
Causes of hypophosphatemia
· Decreased intestinal absorption o Antacids, severe diarrhea, lack of vitamin D · Increased renal elimination o Alkalosis, hyperparathyroidism, DKA, renal tubular absorption defects · Malnutrition and intracellular shifts o Alcoholism, total parenteral hyperalimentaion, recovery from malnutrition, administration of insulin during recovery from DKA
Manifestations of hyperkalemia
· GI: N/V/D, cramps - Neuromuscular: Parasthesias, weakness, dizziness, muscle cramps, twitching, fatigue, dyspnea · Cardiovascular: changes in ECG · Risk of cardiac arrest with severe hyperkalemia
Trancelleular compartment
· Includes the CSF, fluid contained in various body spaces such as peritoneal, pleural, and pericardial cavities; the joint spaces; and GI tract · This amount can increase considerably in conditions such as ascites, in which large amounts of fluid are sequestered in the peritoneal cavity · When the Trancelleular fluid compartment becomes considerably enlarged, it is referred to as a third space because this fluid is not readily available for exchange with the rest of the ECF
The 3 major buffer systems that protect the pH of body fluids are
· The bicarbonate buffer system - proteins -· The Transcellular H+/K+ exchange system
Manifestations of hypernatremia
· Thirst and signs of increased ADH levels o Polydipsia, oliguria or anuria, high urine specific gravity · Intracellular dehydration o Dry skin and mucous membranes, decreased tissue turgor, tongue rough and fissured, decreased salivation and lacrimation · Signs related to hyperosmolality of ECFs and movement of water out of brain cells o Headache, agitation and restlessness, decreased reflexes, seizures and coma · Extracellular dehydration and decreased vascular volume o Tachycardia, weak and thread pulse, decreased blood pressure, vascular collapse
Causes of hyperkalemia
· decreased renal elimination · excessively rapid administration · movement of potassium from the ICF to the ECF compartment
