Fluid and Electrolyte Balance

Question 1

Briefly define acid-base balance and explain how it is normally measured.

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Answer 1

All body fluids, tissues and the bones contain chemical buffers to maintain equilibrium between acids and bases. Basically, an acid is a substance that gives up a hydrogen ion, and a base is one that accepts these hydrogen ions. Extracellularly the primary buffering system is bicarbonate-carbonic acid. On the other hand, there are a number of intracellular buffers. Acid-base balance is measured by examining the arterial blood gasses (ABGs). The four common measurements of the ABGs include:
· pH, which quantifies the hydrogen ion H + concentration.
· Partial pressure of carbon dioxide or CO2 in the arteries or PaCO2.
· Bicarbonate HCO3 concentration.
· Partial pressure of oxygen or PaO2 in the arteries.

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Question 2

Define and characterize metabolic acidosis.

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Answer 2

When the presence of metabolic acids is greater than the concentration of bicarbonate, a low pH (below 7.35) and metabolic acidosis exists. The most common causes of metabolic acidosis are diarrhea or renal excretion, with concomitant loss of bicarbonate, or increased production or ingestion of acids. This imbalance has a number of common cardiopulmonary symptoms, most notably deep and rapid respirations, a decrease in blood pressure, and dilation of the blood vessels. Low arterial pH levels can be life threatening which means sodium bicarbonate and potassium should be administered intravenously. Other diagnostic tools include low bicarbonate level, acidic urine, or elevated serum potassium levels.

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Question 3

Explain the causes and treatment of respiratory acidosis.

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Answer 3

A state in which a patient cannot get rid of as much carbon dioxide as is being produced in the lungs is known as respiratory acidosis. Typically, the patient is usually unable to control the rate and depth of their respirations because they have been sedated, they have cerebral injury following cardiac shutdown, or they have some sort of respiratory disease. An acidic serum pH plus a PaCO2 level greater than 42 mm Hg provides a diagnosis. In addition, symptoms are usually related to effects on the central nervous system or indicators of increased cardiac output. Treatments targeting reduction of carbon dioxide include oxygen administration, inserting a tube into the windpipe, mechanical breathing assistance, bronchodilators, and sometimes antibiotics. Respiratory acidosis can be a chronic condition resulting from emphysema, cystic fibrosis, or asthma.

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Question 4

Discuss metabolic alkalosis, and its possible causes, symptoms and treatment.

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Answer 4

<b>Metabolic alkalosis</b>

<b>Patho-physiology</b> Kidneys excrete more bicarbonate, so pH increases, and hypoventilation occurs to retain carbon dioxide and acid. Decreased strong acid or increased base, with compensatory CO2 retention by lungs

<b> Laboratory </b>Increased serum pH. PCO2 normal if uncompensated and increased if compensated. Increased HCO3 Urine pH > 6 if compensated.

<b>Causes </b>Excessive vomiting, gastric suctioning, diuretics, potassium deficit, excessive mineralocorticoids and NaHCO3 intake.

<b>Symptoms </b> Neuro/ muscular: dizziness, confusion, nervousness, anxiety, tremors, muscle cramping, tetany, tingling, seizures. Cardiac: Tachycardia and arrhythmias. GI: Nausea, vomiting, anorexia. Respiratory: Compensatory hypoventilation.

<b>Treatment </b>Patient may respond to IV 0.9% saline (50 to 100 mL/ hr.) but underlying cause must be identified and treated. Some patients may require hemodialysis.

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Question 5

Explain the effects of long-term diuretic therapy.

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Answer 5

If a patient is given prolonged diuretic therapy with thiazides or furosemide, they can lose hydrogen ions or excrete bicarbonate. This can result in a condition called chronic metabolic alkalosis. The patient’s pH will be high, greater than 7.45. The bicarbonate level in the arteries may be high, other electrolytes such as sodium, phosphorus, or potassium may be low, and the heart rate may be elevated. Common treatments include saline for volume expansion, oral or IV potassium chloride, or use of the type of diuretics that spare potassium (acetazolamide or Diamox).

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Question 6

Discuss respiratory alkalosis, and its possible causes, symptoms and treatment.

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Answer 6

Respiratory alkalosis results from hyperventilation, during which extra CO2 is excreted, causing a decrease in carbonic acid (H2CO3) concentration in the plasma. Respiratory alkalosis may be acute or chronic. Acute respiratory alkalosis is precipitated by anxiety attacks, hypoxemia, salicylate intoxication, bacteremia (Gram-negative), and incorrect ventilator settings. Chronic respiratory alkalosis may result from chronic hepatic insufficiency, cerebral tumors, and chronic hypocapnia.

Characteristics
· Decreased PaCO2.
· Normal or decreased serum bicarbonate (HCO3) as kidneys conserve hydrogen and excrete HCO3.
· Increased pH.

Symptoms
· Vasoconstriction with decreased cerebral blood flow resulting in lightheadedness, alterations in mentation, and/ or unconsciousness.
· Numbness and tingling.
· Tinnitus.
Tachycardia and dysrhythmias.

Treatment 
Identifying and treating underlying cause.  If respiratory alkalosis is related to anxiety, breathing in a paper bag may increase CO2 level.  Some people may require sedation. ABG values in respiratory acidosis:
 ·        pH > 7.45.
 ·        PaCO2 < 38 mm Hg.
 ·        Decreased H2CO3.

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Question 7

Discuss toxemia of pregnancy.

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Answer 7

Toxemia of pregnancy refers to a condition in pregnant women where they may be hypertensive and experience swelling or convulsions. They may also have protein in their urine. During pregnancy, fluid volume is generally enhanced, the acid-base equilibrium is typically altered, serum calcium can be depressed, and changes in renal function usually occur. A condition called respiratory alkalosis often results. Respiratory alkalosis is a result of excess elimination of carbon dioxide and concurrent hyperventilation. Magnesium sulfate is often given to pregnant women to prevent convulsions.

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Question 8

Indicate the importance of body fluids in body composition at various ages.

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Answer 8

Body fluids comprise approximately 80% of body weight in infants. By puberty, adult body weight is generally achieved, at which point fluids account for about 60% of the body weight. Body fluid is excreted in a number of forms including through the pores as sweat, by the kidneys as urine, as water vapor from the lungs, and as vomit and diarrhea from our intestinal tract. Females usually have a lower percentage of fluid weight due to increased storage of fat. Most people also tend to have an increased body fat content with aging and therefore a decrease in relative fluid content.

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Question 9

Describe the two major fluid compartments in the body.

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Answer 9

Body fluids are found as either intracellular fluid (ICF) or extracellular fluid (ECF). ICF is the fluid found inside the cells and, in an adult, it comprises the largest proportion of body weight, approximately two thirds. Any fluids outside of the cells are said to be extracellular. Sweat, gastrointestinal secretions, lymph, cerebrospinal fluid, and ocular, pleural, synovial and pericardial fluids are all examples of ECF. Extracellular fluid is further subdivided into two categories: interstitial fluid, which is fluid located between the cells, and intravascular fluid, which is fluid located within the vessels of the vascular system.

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Question 10

Define the term electrolyte, explain the two types, and give examples.

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Answer 10

An electrolyte is a substance that separates chemically in solution, giving it the ability to then conduct an electrical charge. Electrolytes are either negatively charged particles called anions or positively charged particles called cations. Both anions and cations are found in intracellular fluids (ICF) and extracellular fluids (ECF). In ICF, the principal cation is potassium plus some magnesium and a little sodium, while the primary anion found is phosphate with some sulfate, bicarbonate, and proteinate. In ECF, the most prevalent cation is sodium, while calcium, magnesium, and potassium are also found. The primary anion found in extracellular fluid is chloride, with phosphate, bicarbonate, sulfate, proteinate, and organic acids present in addition. There are also nonelectrolyte solutions in the body such as sugars, fats, and vitamins.

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Question 11

List the various glands and the corresponding hormones in the endocrine system that exert control over fluid and electrolyte balance.

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Answer 11

One endocrine gland, the pituitary gland secretes antidiuretic hormone (ADH) when it is stimulated by the hypothalamus in the brain. ADH regulates water excretion and conservation in the kidneys. There are two hormones controlling homeostasis that are secreted from the adrenal gland, aldosterone and cortisol. Both of these hormones facilitate potassium excretion and consequent restoration of fluid volume by building up sodium. The parathyroid gland produces parathyroid hormone. If levels of this hormone are high then so are calcium levels but conversely phosphate levels are lowered. The thyroid gland releases a compound called calcitonin, which acts in exactly the opposite way; if calcitonin is present in high concentrations, then calcium is actually decreased.

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Question 12

Define homeostasis and give examples of the organs involved in achieving it for fluid and electrolyte balance.

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Answer 12

Homeostasis is the tendency to reach a state of equilibrium or balance. In the case of fluid and electrolyte balance, the primary regulator of fluid balance is the renal system, specifically the urine output from the kidneys. The cardiac system is directly involved here as well because heart and blood vessels circulate the blood through the kidneys, where urine is produced. In addition, a number of other systems facilitate homeostatic mechanisms to maintain water and electrolyte balance. These include the respiratory system in which lungs release water when we exhale and the endocrine system, which contains various glands that control chemical reactions.

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Question 13

List the effects of fluid volume levels and various electrolytes on the cardiac system.

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Answer 13

The heart and cardiac system ultimately push plasma through the kidneys for fluid elimination. Therefore, the pulse is related to fluid volume levels. If fluid volume is low, there is a weak, rapid pulse. Fluid overload will conversely lead to a slow but full pulse. Sodium affects changes in blood volume levels. Potassium stimulates nerve impulses as well as wave generation in the heart muscle. The heart’s ability to contract and relax is regulated by calcium. Another electrolyte, magnesium, produces dilation of the blood vessels, which can lead to unwanted effects such as a decrease in blood pressure and possible cardiac shutdown.

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Question 14

Briefly outline the types of parameters the nursing staff should assess of the patient regularly to determine fluid balance.

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Answer 14

To clinically assess the patient for signs of fluid imbalance, the nurse should first check for fluid ingestion versus excretion and other output. The nurse should confirm urine volume and its concentration. They should check the turgor of the skin and tongue. The health care professional should verify whether the patient is thirsty, tearing, or salivating. Body weight and its fluctuation can also be an indicator of fluid status. Other important measurements include checking for swelling, observing the appearance and temperature of the skin, checking vital signs and central venous pressure, verifying that the oral cavity is moist, and observing whether there are any neurological changes.

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Question 15

List the 4 most important vital signs that should be regularly checked and explain their relationships to fluid and electrolyte balance.

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Answer 15

4 vital signs should be regularly documented include temperature, pulse, respiratory rate, and blood pressure. · A high temperature can indicate a fluid volume deficit often caused by excessive sweating, but sometimes a low temperature can indicate a low volume as well.
· Pulse measures the heart rate. If there is a low fluid volume the heart rate needs to increase in order to maintain cardiac output. Electrolyte imbalances can affect the heart rate; the rate is increased with low potassium or magnesium or elevated sodium and vice versa. Potassium or magnesium deficiencies can also precipitate an irregular heartbeat.
· A fluid volume deficit or loss can cause an upsurge in the respiratory rate. Too much fluid, on the other hand, can be indicated by a shortness of breath or moist rales. If a patient has respiratory alkalosis or is compensating for metabolic acidosis, they may have deep, very fast respirations; conversely in respiratory acidosis or metabolic alkalosis compensation, their respirations are slow and shallow.
· Lastly, blood pressure is directly related to fluid volume levels.

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Question 16

Explain the importance of urine volume and urine concentration.

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Answer 16

Both urine volume and urine concentration indicate whether a patient is experiencing homeostasis, or a state of equilibrium. Both measurements are utilized to determine whether the renal and endocrine systems are operating correctly. · Urine volume is an indication of total fluid output for an individual, and it can tell the health care provider whether the patient has a total fluid volume excess or depletion. · The urine concentration can point to fluid imbalances as well, because if an individual has more concentrated urine, they usually have low fluid levels as well. On the other hand, when a person has more dilute urine, they probably have a fluid volume excess in addition.

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Question 17

Explain what the term turgor means, the sites where it is measured, and its significance.

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Answer 17

Turgor is a measurement of the rigidity of living cells. For human beings, tissue turgor is generally evaluated by pinching the skin and then observing the results after its release. In healthy individuals, the skin will very quickly resume its normal position, but if there is a fluid volume deficit then the skin will remain slightly elevated for a short period. In infants, skin turgor is usually observed in the abdominal area or on the thigh. On adults, the best sites to evaluate turgor are the forehead and the sternum, but the forearm or back of the hand are sometimes used as well. In older adults, turgor measurements may not be as useful because their skin is not very elastic. Tongue turgor is useful to observe as well because the presence of more than one longitudinal furrow can indicate fluid volume depletion and swelling and redness can point to sodium excess.

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Question 18

Explain why it is very important to document weight loss or gain in a patient.

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Answer 18

When an individual gains or losses one kilogram of body weight, they have gained or lost one liter of fluid. Weight loss in a patient, while it could be an indication of tissue loss due to malnutrition or receiving supplements, is more likely to be associated with fluid loss. Rapid loss of 8% or more of body weight is generally a severe fluid volume deficiency. Sometimes, the patient may still have a fluid volume deficiency even if they do not lose weight if the fluid is retained in some other body cavity. Rapid weight gain can represent an increase in fluid volume, which can indicate retention in a variety of fluid compartments. The health care worker should measure the patient’s weight every day, preferably in the morning after they void and before they eat.

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Question 19

Explain the importance of documenting neurological indicators.

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Answer 19

Acid-base or electrolyte imbalances can affect neurologicalparameters. For example, electrolyte imbalances such as calcium or magnesium deficiencies can result in increased neuromuscular excitability. The excessive presence of base or metabolic alkalosis can present as tingling in the fingers or toes or dizziness. This alkalosis causes a decrease in the level of calcium ionization. Some other tests of neurological function include the Chvostek’s sign where the facial nerve is pounded slightly in front of the ear to see whether the facial and eyelid muscles contract together, and the Trousseau’s sign where a blood pressure cuff is inflated above the systolic pressure to see whether there the hand twitches are due to a decreased blood supply.

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Question 20

Define osmolality and explain the two types commonly measured in patients.

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Answer 20

Osmolality is a measurement of the concentration of substances in a solvent, which is normally a liquid. In humans, the solvents we consider are either the serum or urine. Serum osmolality is often determined by the sodium content. It is an important measurement because if a patient is dehydrated, hyperglycemic, or has high blood urine nitrogen, they commonly have increased serum osmolality as well; conversely, with fluid volume excess, the serum osmolality is depressed. A similar concentration measurement is the urine osmolality, which is usually measured along with the serum osmolality to give a more accurate indication of the ability of the kidney to concentrate solutions. Urine specific gravity is a related test that might be also be used.

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Question 21

Give an explanation of the hematocrit test, its normal range, and its role in determining fluid balance.

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Answer 21

The hematocrit test measures the proportion of a plasma sample that is actually comprised of red blood cells (RBCs). This is accomplished by centrifuging the sample. Males generally have 44% to 52% RBCs while females may have a slightly lower percentage, from 39% to 47%. If there is a fluid volume increase, it may be reflected in the hematocrit test with a lower percentage of red blood cells. Conversely, if a patient is dehydrated, they will have an increased hematocrit level because less fluid is present.

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Question 22

Define BUN and the importance of this test.

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Answer 22

BUN is an abbreviation for blood urea nitrogen, which is basically the amount of urea present in the serum. Urea is the terminal product of the metabolism of protein. It is produced in the liver, then transferred to the circulating blood, and ultimately it is excreted by the kidneys. If a patient is overhydrated or does not ingest enough protein, they can have a low BUN. Dehydration or excessive protein intake can elevate the BUN level, which can also occur with any conditions that deplete fluids. A normal adult BUN level is between 10 and 20 mg/ dL.

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Question 23

State the most vulnerable age groups to fluid or electrolyte imbalances and explain the reasons.

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Answer 23

The most vulnerable age groups that might experience fluid or electrolyte imbalances are infants and the elderly. Infants do not have a fully developed kidney function, and they generally excrete more than they take in. Therefore, they may experience too low fluid levels. The elderly are at increased risk for a fluid depletion. They often have an inadequate renal function and the respiratory system often cannot maintain a normal pH. It is hard for the health care provider to determine their fluid status because their skin lacks elasticity. The elderly are often confused, they do not feel thirsty enough to drink, or they often are taking diuretics or laxatives, all of which can lead to a net fluid deficit.

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Question 24

Explain how medications the patient may be taking can potentially cause fluid or electrolyte imbalances.

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Answer 24

Several types of medications or intravenous solutions (IV) can create fluid or electrolyte imbalances. If a patient is taking diuretics, fluids and electrolytes are often depleted. Depending on the diuretic used, sometimes there can actually be high electrolyte levels. If the individual is taking laxatives, they may have low potassium levels. Administration of corticosteroids often causes fluid and electrolyte accumulation, reduced potassium levels, or abnormally high pH in the respiratory and metabolic systems. Certain IV solutions can lead to fluid or electrolyte imbalances as well. The most common examples would be excessive administration of sodium-containing solutions, which could result in fluid volume excess or increased sodium levels, or use of electrolyte-free solutions, which could deplete electrolytes.

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Question 25

List possible causes of fluid volume deficit.

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Answer 25

Fluid volume deficit, or hypovolemia, can be caused by either excessive fluid loss or a diminished fluid intake.
· Abnormal fluid loss most commonly occurs through the gastrointestinal tract, such as when vomiting or diarrhea occurs. Fluid can also be lost through the skin, either as a means of dispelling heat when the patient’s temperature is elevated, as a result of breaks in the skin, or simply as a way to control body temperature. If a hemorrhage has occurred, fluid volume can decrease in the intravascular space. Fluid can drift to areas where it cannot be utilized, such as can occur with ascites production, internal bleeding, or fluid being trapped in the bowel or other spaces.
· Hypovolemia can also occur if fluid intake is decreased because of inadequate intravenous solutions, lack of thirst, or inability to obtain proper fluids.

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Question 26

Define hypervolemia and list some of its causes.

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Answer 26

Hypervolemia is too much fluid in the extracellular compartments. Possible causes include the following:
· One of the chief causes of hypervolemia is the intake of a surplus of sodium and subsequent water retention. This excess sodium may come from sodium-containing intravenous solutions, sodium-rich foods or oral or IV medications that have sodium in them.
· Hypervolemia may also be caused by water or sodium retention due to antidiuretic hormone (ADH) or aldosterone production after surgery, or the product of other diseases, renin production, or use of corticosteroids. Fluid may be moved from the interstitial to the vascular space during burn treatment or use of certain IV solutions or medications with high osmolarity.
· There are instances as well where individuals cannot void properly such as in renal disease, which can lead to hypervolemia.

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Question 27

Define edema and explain its causes.

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Answer 27

Edema is a buildup of fluid in the spaces between groups of organs or between cells, commonly called the interstitial space. Edema can occur as a consequence of inflammation. Generalized edema can also result when the patient experiences excessive sodium and water retention, or when the dynamics of exchange in their capillaries have been altered. Edema is often observed in the feet and ankles, but it can also be common in the back and buttocks if the patient has been bedridden. Severity of the edema can be assessed by measuring the area with a tape measure every day.

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Question 28

Explain the difference between the 2 forms of diabetes.

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Answer 28

Diabetes is a disorder that causes the body to excrete excess urine.
· One form, diabetes insipidus, is primarily related to a water imbalance. This water imbalance is a result of a lack of antidiuretic hormone (ADH) being produced by the hypothalamus or the failure of the renal system to respond to this ADH. This condition can also be caused by head injury or metastases.
· Diabetes mellitus, on the other hand, results when enough insulin is not secreted or utilized. The patient typically becomes hyperglycemic with elevated blood or urine glucose levels and has ketoacidosis. They can also have depressed serum carbon dioxide levels, hypovolemia, or low potassium levels.

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Question 29

Illustrate the process of restoring fluid and electrolyte balance after burns.

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Answer 29

Fluid and electrolytes escape through the injured skin areas after an individual is burned. For about the first day, water, electrolytes and even proteins in the blood vessels are lost via the damaged capillaries and cells and edema results. Then the capillary walls begin to close back up. Several days after the burn incident, the fluid in the swollen areas begins to move into the blood vessels and consequently the blood volume increases. As a result, there is an increase in the urinary output at that point as well. Typically, intravenous fluids are also administered to burn patients to replace fluids and electrolytes.

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Question 30

Explain the importance of the electrolyte sodium.

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Answer 30

Sodium is the major electrolyte in the extracellular fluid (ECF). It is available as a positively charged cation. Sodium levels control water distribution in the body and the volume of ECF. In the neuromuscular system, sodium increases the responsiveness of the nerve and muscle tissue and actually transmits nerve impulses. Sodium also helps to equilibrate the acid-base balance in the body. The normal range for sodium is 135-145 mEq sodium per liter.

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Question 31

Define hyponatremia, explain how it can occur, and list its symptoms and effects.

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Answer 31

Hyponatremia is a low level of sodium in the bodily fluids, below 135 mEq/ L. It can be caused by too much fluid intake, either because of administration of dextrose-containing solutions, psychiatric issues, or a syndrome called SIADH. SIADH stands for syndrome of inappropriate antidiuretic hormone, where ADH is secreted unnecessarily and water retention occurs as a result. Adrenal insufficiency can also stimulate ADH. If diuretics are used or excessive sweating occurs particularly in cystic fibrosis patients, sometimes there is too much sodium loss. Symptoms include a decrease in plasma osmolality, neuromuscular effects, gastrointestinal issues, weight gain, edema, hypotension and dizziness.

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Question 32

Define hypernatremia, explain how it can occur, and list its symptoms and effects.

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Answer 32

Hypernatremia is an excess of sodium in the bodily fluids, measured as a serum level of greater than 145 mEq/ L. It can occur because of the presence of excess sodium or an increased loss of water. Intravenous therapy with sodium-containing solutions or medications is a typical cause of hypernatremia, but there is also a disease called primary aldosteronism, where sodium is not properly excreted. Water loss can precipitate hypernatremia as well. This loss can occur as a result of burns, sweating, impaired thirst, vapor loss from the lungs, an abnormally large urine output, or a condition called diabetes insipidus in which there is no suitable antidiuretic hormone. A patient with nervous system disorders or in a coma may have hypernatremia. They may be thirsty, have dry or sticky mucous membranes, not much saliva or tears, a rough, difficulty speaking, high temperature, or flushed skin. They can also have a low central venous pressure because of the fluid loss.

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Question 33

Explain the most common ways to treat sodium imbalances in a patient.

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Answer 33

Administration of oral or intravenous fluids is often used to treat sodium imbalances in a patient. If that patient is hyponatremic, hypertonic sodium chloride solutions are typically administered, but if the patient is hypernatremic solutions with low osmolality or containing 5% dextrose in water should be given. Diuretics are sometimes utilized for both conditions. In hyponatremia where there is generally a fluid excess, the diuretics help the patient to excrete this excess fluid. In patients with diabetes insipidus, they already have an increased water loss, but diuretics may still be used to lower

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Question 34

Describe the main role and mechanism of action of the cation potassium in maintaining fluid and electrolyte balance.

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Answer 34

Potassium is the major positively charged electrolyte found intracellularly. Very little is found in the extracellular space, and the equilibrium between the two spaces is provided primarily through a pumping mechanism called the sodium-potassium pump. The kidneys regulate potassium levels by inducing increased excretion of potassium in the urine when serum levels are high. If potassium levels are high, more aldosterone is produced which leads to greater water and sodium retention and subsequent potassium elimination. Potassium also regulates the intracellular osmotic pressure and helps to normalize acid-base balance. The normal range for potassium is 3.5-5.0 mEq/ L.

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Question 35

Define hypokalemia and briefly explain its causes and symptoms.

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Answer 35

Hypokalemia is defined as a depressed serum potassium levels, below 3.5 mEq/ L. It can be caused by potassium loss, inadequate potassium consumption, stress, or movement of the cation into the cells. The primary cause of potassium loss is the use of diuretics and thiazides. If an individual is under stress, they may produce more aldosterone and epinephrine, which cause potassium to be either excreted or driven intracellularly. Besides common symptoms of the neuromuscular system, the most important possible symptoms of hypokalemia are related to a change in cardiac function reflected as an abnormal ECG. Blood gases usually show the patient to have a high pH, indicating they are in metabolic alkalosis.

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Question 36

Define hyperkalemia and explain what disease it is often associated with. Give causes and symptoms.

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Answer 36

Hyperkalemia is an overly high amount of potassium in the serum above 5.0 mEq/ L. The state is often associated with the presence of renal disease, either an acute attack or chronic. Besides increased consumption or poor potassium excretion, this condition can also be caused by the movement of potassium from inside the cells to the extracellular space by mechanisms related to metabolic acidosis and hyperglycemia. Symptoms of hyperkalemia typically involve the nerves and muscles including those of the heart. They include increased neuromuscular responses, weakness in the body and arms, and possible atrial or ventricular fibrillation and blocking of the heart. Arterial blood gases may show metabolic acidosis, and ECGs show patterns of approaching cardiac shutdown.

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Question 37

Explain how potassium imbalances are treated.

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Answer 37

If a patient is experiencing a potassium deficit, or hypokalemia, they may be instructed to institute dietary changes or given supplements if the case is mild. However, if levels of potassium are very low, some form intravenous potassium is usually administered. Sometimes initially the patient may be given other IV solutions just to ensure adequate hydration and kidney function. The treatments for hyperkalemia are quite different. These include treatment with cation exchange resins, IV administration of high osmolality glucose and insulin solutions, administration of sodium bicarbonate or calcium gluconate, or dialysis. Dialysis of the blood or peritoneal fluid is used to get rid of too much potassium in extreme cases.

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Question 38

Give an overview of the importance of calcium and the ways in which it is regulated.

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Answer 38

Calcium is a positively charged electrolyte that is involved in the formation of bones and teeth, neuromuscular performance, and the clotting cascade. Calcium has an inverse relationship to phosphorus. Its production is controlled by the parathyroid hormone and calcitonin; its elimination can occur via the gastrointestinal or urinary tracts and skin as well as by bone deposition. The normal range for serum concentration of calcium is between 8.9 and 10.3 mg/ dL, of which approximately 50% is in the ionized form and most of the rest is tied to other molecules. Only a minute percentage of the total calcium is located in the extracellular fluid.

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Question 39

Give examples of the possible etiologies and symptoms of hypocalcemia versus hypercalcemia.

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Answer 39

Since calcium concentration is regulated by the parathyroid, if this gland’s regulatory functions are altered because of surgical intervention, injury, or malignancy, imbalances can occur. Hypocalcemia, defined as a serum level of less than 4.6mEq/ L( 8.9 mg/ dL) usually occurs because the intestines cannot adequately absorb the calcium or because it is lost through use of diuretics or disease or if the parathyroid glands are injured. Most symptoms of this condition are related to neuromuscular activity or respiratory effects. Hypercalcemia, defined as a serum level above 5. l mEq/ L (10.3 mg/ dL), can be caused by increased ingestion or decreased excretion of calcium but it also can originate as a result of calcium loss from the bone itself. The latter is usually related either to hyperparathyroidism, metastatic bone disease, long periods of immobilization, or multiple fractures.

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Question 40

Explain the importance of magnesium in the body.

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Answer 40

Magnesium is a cation found mostly in the bones or muscles, and only minimally in the extracellular fluid. Magnesium plays a number of important roles in the body. These functions include activation of enzymes and regulation of protein and carbohydrate metabolism and neuromuscular regulation. In addition, magnesium can dilate blood vessels, which can affect blood pressure and cardiac output. The normal range for serum level of magnesium is 1.3 to 2.1 mEq/ L. Low levels are associated with a variety of muscle, nerve (including mental), and cardiac abnormalities, and high levels can depress the heart rate leading to possible cardiac arrest.

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Question 41

Describe how phosphate affects fluid and electrolyte balance and renal disease.

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Answer 41

Phosphate is the primary anion found in the intracellular fluid and it is also present in the extracellular compartment. The metabolism and equilibrium concentrations of phosphate and calcium are reversely related and both are regulated by the parathyroid gland. Phosphate is important in the metabolism of protein, fats and carbohydrates, energy transfer, the promotion of acid-base balance, and the stimulation of muscle and nerve activity. In renal disease, it is important to look for hyperphosphatemia, or phosphate excess, because the kidney’s ability to excrete phosphate is diminished. The normal range for serum phosphate is 2.5-4.5 mg/ dL.

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Question 42

Explain the role chloride ions play in maintaining bodily functions and its relationship to other ions.

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Answer 42

Chloride is the main negatively charged electrolyte found in the extracellular fluid and its level is directly related to the levels of both sodium and potassium cations. It has a reverse relationship to the amount of bicarbonate present. Chloride helps to regulate water movement. The cation also helps maintain acid-base equilibrium and the reabsorption of sodium. When IV solutions with potassium or sodium are given continuously or too much or during metabolic acidosis as an adjunct to dehydration or bicarbonate loss, excess chloride or hyperchloremia, can also result. The normal range for chloride values are 97 to 100 mEq/ L.

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Question 43

Define tonicity and the three types of solutions based on this parameter.

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Answer 43

Tonicity is a ongoing energetic process whereby particles or molecules move from one compartment to another in the body. While small molecules can easily shift between compartments, larger ones cannot move as easily. The molecule size combined with the permeability of the membrane determines the rate of movement of fluids and electrolytes between compartments. Solutions can be hypotonic, isotonic or hypertonic:
· A hypotonic solution has a solute concentration lower than that generally found in bodily fluids, defined as less than 240 mOsm/ kg.
Isotonic solutions have an osmolality similar to plasma with a range of 240 to 340 mOsm/ kg.
· Hypertonic solutions have a higher osmolality, above 340 mOsm/ kg.

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Question 44

Explain why one would choose to administer solutions with different tonicities.

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Answer 44

When a hypotonic solution is administered, the fluid is drawn intracellularly. This type of solution, for example 0.45% sodium chloride, is sometimes used to treat situations where there is an electrolyte excess. Isotonic solutions, which include 0.9% saline, 5% dextrose in water, and Lactated Ringer’s, are often given to rapidly increase the extravascular volume. This is because water by itself will not generally move from one space to another. Hypertonic solutions add high solute concentrations, which result in greater fluid pressure. Therefore, they pull fluid out of cells and cause them to shrink, a trait making them useful to decrease intracellular fluid or for volume expansion. Hypertonic solutions include 3% or 5% sodium chloride or 50% dextrose in water.

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Question 45

List the main reasons dextrose solutions might be given to a patient.

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Answer 45

Dextrose in water is either administered as an isotonic solution (5%) or at higher hypertonic concentrations. Since these fluids do not contain electrolytes, their main functions are to hydrate and to provide calories to the patient. Particularly in the very concentrated hypertonic solutions, 20% dextrose and above, administration is done to provide calories. Amino acids may be included as well to enhance total nutrition. 50% dextrose in water is usually utilized to counteract low blood sugar levels related to hypoglycemia. Dextrose may also be administered in solution with various hypertonic concentrations of sodium chloride. These combinations not only provide calories but can also provide needed electrolytes and provide fluid volume expansion.

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Question 46

List the contents of Ringer’s solution and its variants and explain the indications for each variant.

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Answer 46

Ringer’s solution or injection by itself is an isotonic solution that mimics the electrolyte composition of plasma. It contains sodium, potassium, calcium and chloride. If lactate is added as a buffer, the solution is called Lactated Ringer’s injection or Hartmann’s solution. The added lactate will metabolize to produce bicarbonate, which is normally present in the extracellular fluid. Both of these variations provide fluid and electrolytes, but no calorie requirements when used alone. Furthermore, the lactated version should not be used in hepatic disorders or lactic acidosis. 5% dextrose is commonly added to both types of Ringer’s solutions to provide calorie intake, but in doing so the solution becomes hypertonic. Therefore, when administering the dextrose-containing injections, one must watch for fluid volume excess or complications from diabetes mellitus.

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Question 47

Explain the reasons to administer plasma expanders and list examples of these agents.

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Answer 47

Plasma expanders are colloidal solutions given in order to expand the intravascular compartments, usually administered in emergency situations. They can include blood components, the innate plasma protein albumin, or synthetic colloids. The commonly given synthetic colloids are dextran, mannitol, and hetastarch (Hespan). Dextran solutions can contain either high or low molecular weight dextran commonly diluted into either 5% dextrose or 0.9% saline. In either case, the main use for dextran solutions is restoration of vascular volume that has been depressed due to some traumatic event. The health care provider must watch for possible hypersensitivity to dextran and subsequent anaphylactic reactions. Mannitol is a sugar alcohol, found commercially in solutions from 5% to 25%; it is primarily used to stimulate loss of fluid thereby decreasing pressure. Hespan, found in 6% concentration in 0.9% saline, is similar in use and complications to dextran. Albumin is normally administered during shock to promote volume expansion.

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Question 48

List and explain the mechanisms involved for some unique solutions administered to maintain fluid and electrolyte balance.

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Answer 48

Solutions with a high or alkaline pH, most commonly 5% sodium bicarbonate, might be given to a patient in order to normalize excess acids. This is accomplished by dissociation of the compound to generate bicarbonate anion, which is the major buffer in the extracellular fluid. A hypertonic alcohol solution, typically 5% ethyl alcohol in 5% dextrose might be administered as a substitute for water with the addition of calories. The mechanism here is metabolism of the ethyl alcohol in the liver into acetaldehyde or acetate. There are also a variety of premixed IV solutions available that can be beneficial because they either include medications or provide the appropriate buffering capacity or pH.

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