Chp 4 fluid and electrolyte - feel free to add if you are in NURS 125 at MC
Shock can occur when the volume of fluid lost exceeds
25% of the intravascular volume, or when fluid loss is rapid.
Average daily I/O is
2600/2600
Normal ranges of Hematocrit
42% - 52% for males 35% - 47% for women
Urine sodium values
75 to 200 mEq/24hrs
Risk Factors for Hypovolemia -
Additional risk factors include diabetes insipidus, adrenal insufficiency, osmotic diuresis, hemorrhage, and coma. Third-space fluid shifts, or the movement of fluid from the vascular system to other body spaces (e.g., with edema formation in burns, ascites with liver dysfunction), also cause FVD.
Pathophysiology of Hyponatremia -
Plasma sodium concentration represents the ratio of total body sodium to total body water. A decrease in this ratio can occur because of salt loss that is greater than water loss (e.g., diarrhea, diuretics, NG tube suctioning), or there is an excess of water relative to total body sodium (e.g., congestive heart failure, cirrhosis of the liver, excessive water intake without salt, syndrome of inappropriate secretion of antidiuretic hormone [SIADH]). Therefore, a hyponatremic state can be superimposed on an existing FVD or FVE.
Serum electrolyte changes may also exist in Hypovolemia -
Potassium and sodium levels can be reduced (hypokalemia, hyponatremia) or elevated (hyperkalemia, hypernatremia): • Hypokalemia occurs with GI and renal losses. • Hyperkalemia occurs with adrenal insufficiency. • Hyponatremia occurs with increased thirst and ADH release. • Hypernatremia results from increased insensible losses and diabetes insipidus.
Sodium Imbalances
Sodium is the most abundant electrolyte in the ECF; its concentration ranges from 135 to 145 mEq/L (135 to 145 mmol/L). Consequently, sodium is the primary determinant of ECF osmolality. Sodium plays a major role in controlling water distribution throughout the body because it does not easily cross the cell membrane and because of its abundance and high concentration in the body. Sodium also functions in establishing the electrochemical state necessary for muscle contraction and the transmission of nerve impulses. Sodium is regulated by ADH, thirst, and the renin- angiotensin-aldosterone system. A loss or gain of sodium is usually accompanied by a loss or gain of water. The two most common sodium imbalances are sodium deficit and sodium excess.
Sodium may be lost by -
Sodium may be lost by way of vomiting, diarrhea, fistulas, or sweating, or it may be lost as the result of the use of diuretics, particularly in combination with a low-salt diet. A deficiency of aldosterone, as occurs in adrenal insufficiency, also predisposes to sodium deficiency. In dilutional hyponatremia (water intoxication), the patient's serum sodium level is diluted by an increase in the ratio of water to sodium. Dilutional hyponatremia, therefore, results from an increased ECF volume and a normal or increased total body sodium. Predisposing conditions for this type of hyponatremia include cirrhotic ascites; SIADH; hyperglycemia, which causes increased water to be drawn into the IVS; and increased water intake through the administration of electrolyte-poor parenteral fluids, the use of tap-water enemas, or the irrigation of nasogastric tubes with water instead of normal saline solution. Water may be gained abnormally by the excessive parenteral administration of hypotonic solutions such as dextrose and water solutions, particularly during periods of stress. It may also be gained by compulsive water drinking (psychogenic polydipsia).
Chief so lutes in sweat are
Sodium, chloride, and potassium
Correcting Fluid Volume Deficit
When administering oral fluids, consideration is given to the patient's likes and dislikes. The type of fluid the patient has lost is also considered, and attempts are made to select fluids most likely to replace the lost electrolytes. If the patient is reluctant to drink because of oral discomfort, the nurse assists with frequent mouth care and provides nonirritating fluids. If nausea is present, antiemetics may be ordered and administered before oral fluid replacement is initiated. If the patient cannot eat and drink, fluid may need to be administered by an alternative route (enteral or parenteral) until adequate circulating blood volume and renal perfusion are achieved. Isotonic fluids are prescribed to increase ECF volume.
When hyponatremia is due primarily to sodium loss,
_____________________________________________________the urinary sodium content is less than 20 mEq/L (20 mmol/L), suggesting increased proximal reabsorption of sodium secondary to ECF volume depletion, and the specific gravity is low (1.002 to 1.004).
An example of a typical fluid challenge involves
administering 100 to 200 mL of normal saline solution over 15 minutes. The goal is to provide fluids rapidly enough to attain adequate tissue perfusion without compromising the cardiovascular system. The response by a patient with FVD but normal renal function is increased urine output and an increase in blood pressure and central venous pressure.
The skull limits the brain's ability to expand, which results in increased ICP, the precursor to brain damage. Neurologic changes include
altered mental status, headache, lethargy, seizures, and a progressively decreased level of consciousness eventuating in coma
Hyponatremia - The basic physiologic disturbances in SIADH are
are excessive ADH activity, with water retention and dilutional hyponatremia, and inappropriate urinary excretion of sodium in the presence of hyponatremia. SIADH can be the result of either sustained secretion of ADH by the hypothalamus or production of an ADH-like substance from a tumor (aberrant ADH production).
To assess for FVD, the nurse monitors and measures fluid I&O at least
at least every 8 hours, and sometimes hourly. As FVD develops, body fluid losses exceed fluid intake. This loss may be in the form of excessive urination (polyuria), diarrhea, vomiting, and so on.
The lungs
Eliminate caper vapor - insensible loss, at a rate of approach 400 mL every day
Creatinine
End product of muscle metabolism better indicator of renal function than BUN Serum creatine levels increase when renal function decreases
Factors that decrease BUN
End stage liver disease, a low protein diet, starvation, and any condition that involves expanded fluid volume , such as pregnancy
In SIADH, the administration of hypertonic saline solution alone cannot change the plasma sodium concentration.
Excess sodium would be excreted rapidly in a highly concentrated urine. With the addition of the diuretic furosemide (Lasix), urine is not concentrated, and isotonic urine is excreted to effect a change in water balance. In patients with SIADH, in whom water restriction is difficult, lithium or demeclocycline can antagonize the osmotic effect of ADH on the medullary collecting tubule.
S/S of Hypovolemia -
FVD can develop rapidly and can be mild, moderate, or severe, depending on the degree of fluid loss. Important signs include acute weight loss; decreased skin turgor; oliguria (urinary output <400 mL/Day); concentrated urine with a high specific gravity; postural hypotension (a 15 mm Hg decrease in systolic pressure or a 10 mm Hg decrease in diastolic pressure with position change); a weak, rapid heart rate; flattened neck veins; decreased central venous pressure; cool, clammy skin related to peripheral vasoconstriction; a smaller tongue with additional longitudinal furrows; dry oral mucous membranes; delayed capillary refill; altered sensorium; and thirst.
Pathophysiology Hypovolemia -
FVD results from loss of body fluids and occurs more rapidly when coupled with decreased fluid intake. FVD can develop from inadequate intake alone if the decreased intake is prolonged. Causes of FVD include abnormal fluid losses, such as those resulting from vomiting, diarrhea, GI suctioning, and sweating, and decreased intake, as in nausea or inability to gain access to fluids.
Filtration allows the kidneys to
Filter 180L of plasma per day
____________________________________________________________________________________________ are frequently used to treat the hypotensive patient with FVD because they expand plasma volume. ICS is essentially sodium free, thus for every liter of 0.9% sodium chloride administered, 1,000 mL will remain in the ECS, of which approximately 250 mL will remain in the IVS, re-expanding the plasma volume. Because this solution can expand the IVS, patients must be assessed for signs and symptoms of fluid volume excess (discussed shortly).
Isotonic electrolyte solutions (e.g., lactated Ringer's solution, 0.9% sodium chloride)
_____________ are prescribed to increase ECF volume.
Isotonic fluids
Hypovolemia occurs when -
It occurs when water and electrolytes are lost in the same proportion as they exist in normal body fluids, so that the ratio of serum electrolytes to water remains the same. FVD should not be confused with the term dehydration, which refers to loss of water alone, with increased serum sodium levels. FVD may occur alone or in combination with other imbalances. Unless other imbalances are present concurrently, serum electrolyte concentrations remain essentially unchanged.
Organs involved in homeostatis
Kidneys, lungs, heart, adrenal glands, parathyroid glands, and pituitary gland
BUN is
Made up of urea, the end product of metabolism of protein both muscle and dietary intake by the liver
in severe FVD
Mental function is eventually affected in severe FVD as a result of decreasing cerebral perfusion. Decreased peripheral perfusion can result in cold extremities. In patients with relatively normal cardiopulmonary function, a low central venous pressure is indicative of hypovolemia. Patients with acute cardiopulmonary decompensation require more extensive hemodynamic monitoring of pressures in both sides of the heart to determine if hypovolemia exists.
Factors that decrease hematocrit values
Over hydration and anemia
Active transport
Physiologic pump that moves fluid from an area of low concentration to one of higher concentration; active transport requires ATP for energy
With true salt loss
poor skin turgor, dry mucosa, headache, decreased saliva production, orthostatic fall in blood pressure, nausea, and abdominal cramping occur.
In a patient with normal or excess fluid volume, hyponatremia is treated by
restricting fluid to a total of 800 mL in 24 hours. This is far safer than sodium administration and is usually effective. However, if neurologic symptoms are present, it may be necessary to administer small volumes of a hypertonic sodium solution, such as 3% sodium chloride. Incorrect use of these fluids is extremely dangerous, because 1 L of 3% sodium chloride solution contains 513 mEq of sodium with a osmolality of 1,026. If edema exists alone, sodium is restricted; if edema and hyponatremia occur together, both sodium and water are restricted.
Treatment depends on the cause of the hyponatremia. . If the etiology is related to sodium and (to a lesser extent) water loss
sodium and water replacement is expected.
FVD - Skin turgor is a less valid assessment in the elderly patient because
the skin has lost some of its elasticity due to the decreased number of papillae and collagen fibers; therefore, other assessment measures (e.g., slowness in filling of veins of the hands and feet) become more useful in detecting FVD. In elderly patients, skin turgor is best tested over the forehead or the sternum, because alterations in skin elasticity are less marked in these areas.
Tongue turgor is not affected by age. In a normal person
the tongue has one longitudinal furrow.
, when hyponatremia is due to SIADH,
the urinary sodium content is greater than 20 mEq/L, and the urine specific gravity is usually greater than 1.012. Although the patient with SIADH retains water abnormally and therefore gains body weight, there is no peripheral edema; instead, fluid accumulates inside the cells. SIADH it may be as low as 100 mEq/L (100 mmol/L) or even less. Serum osmolality is also decreased, except in azotemia or ingestion of toxins.
Tongue turgor In the person with FVD
there are additional longitudinal furrows, and the tongue is smaller because of fluid loss. The degree of oral mucous membrane moisture is also assessed; a dry mouth may indicate either FVD or mouth breathing.
During a fluid challenge test,
volumes of fluid are administered at specific rates and intervals while the patient's hemodynamic response to this treatment is monitored (i.e., vital signs, breath sounds, sensorium, central venous pressure, pulmonary capillary wedge pressure values, and urine output).
With water gain in excess of sodium, clinical manifestations are associated
with FVE, such as edema, crackles, ascites, and JVD. Symptoms are primarily neurological. They are related to osmotic water shift as water from the relatively dilute ECF is pulled into the cell, leading to increased ICF volume, specifically brain cell swelling or cerebral edema
The usual daily sodium requirement in adults is approximately
100 mEq, provided no abnormal losses occur.
When the serum sodium level decreases to less than 115 mEq/L (115 mmol/L), signs of -
of increasing intracranial pressure, such as lethargy, confusion, muscle twitching, focal weakness, hemiparesis, papilledema, and seizures, may occur.
Clinical manifestations of hyponatremia depend on
on the cause, magnitude, and speed with which the deficit occurs. Patients can present with FVD, as euvolemic (SIADH), or with FVE.
Early evidence of third space fluid shifting is -
A decrease in urine output despite adequate fluid intake. Urine output decreases because fluid shifts out of the intravascular space; the kidneys then receive less blood and attempt to compensate by decreasing urine output.
Osmotic diuresis
Is an increase in urine output caused by the excretion of substances such as glucose, mannitol, or contrast agents in the urine, which exert an osmotic pull on water.
Diffusion
Is the movement from a higher concentration to one of lower concentration
Normal range for specific gravity is
1.010 to 1.025
Treatment depends on the cause of the hyponatremia. if the etiology is related to water intoxication,
, restriction of fluid intake and diuretics are anticipated.
Usual daily urine volume in the adult is
1.5 L
Normal BUN
10-20 mg/dl 3.6 to 7.2 umol /L
Hematocrit measures
The volume percentage if RBC erythrocytes in whole blood
Third-spacing
Aka interstitial fluid shift Loss of ECF , extracellular space, fluid outside the cell, into a space that does not contribute to equilibrium between the ICF and the ECF.
Describe the role of the adrenal glands in homeostasis -
Aldosterone, a mineralocorticoid secreted by the zona glomerulosa (outer zone) of the adrenal cortex, has a profound effect on fluid balance. Increased secretion of aldosterone causes sodium retention (and thus water retention) and potassium loss. Conversely, decreased secretion of aldosterone causes sodium and water loss and potassium retention. Cortisol, another adrenocortical hormone, has only a fraction of the mineralocorticoid potency of aldosterone. However, when secreted in large quantities (or administered as corticosteroid therapy), it can also produce sodium and fluid retention.
HYPERVOLEMIA -
An isotonic expansion of the ECF caused by the abnormal retention of water and sodium in approximately the same proportions in which they normally exist in the ECF.
The general rule for urine output per day in all age groups is
Approx .5 to 1 mL of urine per kg of body weight per hour .5 to 1 mL/kg/hour
Normal serum creatine
Approx 0.7 to 1.4 mg/dL Or 63 to 124 umol\L
Third spacing occurs in-
Ascites, burns, peritonitis, bowl obstruction, and massive bleeding into a joint or body cavity.
Example of osmotic diuresis
Because glucose is an osmotic agent , capable of affecting water movement, when glucose is present or "spilled" in the urine, it will bring water with it, causing polyuria and FVD.
Diagnostic test for Hypovolemia -
Diagnostic testing includes BUN and its relation to serum creatinine concentration. A volume-depleted patient has a BUN elevated out of proportion to the serum creatinine (ratio >20:1). The BUN can also be elevated because of decreased renal perfusion and function. The cause of abnormal laboratory findings may be determined through the health history and physical findings. The hematocrit level is greater than normal in dehydration because the RBC become suspended in a decreased plasma volume, which is also known as hemoconcentration. Urine specific gravity is increased in relation to the kidneys' attempt to conserve water and decreased with diabetes insipidus. Urine osmolality is greater than 450 mOsm/kg because the kidneys try to compensate by conserving water.
Factors that increase BUN
Decreased renal function GI bleeding Dehydration Increased protein intake Fever Sepsis
Factors that increase hematocrit values
Dehydration and polycythemia
Osmolarity
Describes the concentration of so lutes or dissolved particles
Factors increasing serum urine osmolality
Fluid volume deficit SIADH Congestive heart failure Acidosis
Factors decreasing urine osmolality
Fluid volume excess Diabetes insipidus Hyponatremia Aldosteronism Pyelonephritis
Factors decreasing serum osmolality
Fluid volume excess Syndrome of inappropriate anti diuretic hormone SIADH Renal failure Diuretic use Adrenal insufficiency Hyponatremia Over hydration Paraneoplastic syndrome associated with lung cancer
Other S/S of third spacing that indicate an intravascular fluid volume deficit , FVD, include
Heart rate, decreased BP, decreased central venous pressure , edema, increased body weight, and imbalances in I&O
Filtration
Hydrostatic pressure in the capillaries tends to filter fluid out of the intravascular compartment into the interstitial fluid. Occurs from high to low.
a fluid challenge test.
If the patient with severe FVD is not excreting enough urine and is therefore oliguric, the health care provider needs to determine whether the depressed renal function is caused by reduced renal blood flow secondary to FVD (prerenal azotemia or increased nitrogen levels in the blood) or, more seriously, by acute tubular necrosis from prolonged FVD. The test used in this situation is referred to as
HYPONATREMIA -
NA+ <135 mEq/L
HYPOVOLEMIA -
Occurs when loss of ECF volume exceeds the intake of fluid.
Urine sodium levels are used to assess -
Volume status and is useful to diagnose hyponatremia and acute renal failure
Renal function in the elderly
Renal function declines with advanced age, as do muscles, and daily exogenous creatine production. Therefore, high-normal and minimally elevated serum creatine values may indicate substantially reduced renal function in the elderly.
Normal serum osmolality
Serum 275-300 mOsm/kg water
Factors increasing serum osmolality
Severe dehydration Free water loss Diabetes insipidus Hypernatremis Hyperglycemia Stroke or head injury Renal tubular necrosis Consumption of methanol or ethylene glycol, antifreeze
Tonicity
The ability of all the solutes to cause an osmotic driving force that promotes water movement from one compartment to another.
Pituitary glands role in homeostasis -
The hypothalamus manufactures ADH, which is stored in the posterior pituitary gland and released as needed. ADH is sometimes called the water-conserving hormone because it causes the body to retain water. Functions of ADH include maintaining the osmotic pressure of the cells by controlling the retention or excretion of water by the kidneys and by regulating blood volume
Urine specific gravity measures
The kidneys ability to excrete or conserve water
Describe the role of the lungs in the bodies fluid compustian and volume
The lungs are also vital in maintaining homeostasis. Through exhalation, the lungs remove approximately 400 mL of water daily in the normal adult. Abnormal conditions, such as hyperpnea (abnormally deep respiration) or continuous coughing, increase this loss; mechanical ventilation with excessive moisture decreases it. The lungs also play a major role in maintaining acid-base balance. Normal aging results in decreased respiratory function, causing increased difficulty in pH regulation in older adults with major illness or trauma. The lungs normally eliminate water vapor (insensible loss) at a rate of approximately 400 mL every day. The loss is much greater with increased respiratory rate or depth, or in a dry climate.
Osmolality
The number if osmoles , the standard unit of osmotic pressure, per kg of solution, expressed as mOsm/kg; used more often in clinical practice than the term osmolarity to evaluate serum and urine; in addition to urea and glucose, sodium contributes the largest number of particles to osmolality
FVD - Vital signs are closely monitored.
The nurse observes for a weak, rapid pulse and postural hypotension (i.e., a decrease in systolic pressure exceeding 15 mm Hg when the patient moves from a lying to a sitting position).
Parathyroid glands role in homeostasis -
The parathyroid glands, embedded in the thyroid gland, regulate calcium and phosphate balance by means of parathyroid hormone (PTH). PTH influences bone resorption (movement of calcium out of bone to the blood), calcium absorption from the intestines, and calcium reabsorption from the renal tubules.
Hydrostatic pressure-
The pressure exerted by the fluid on the walls of the blood vessel by the heart. Normal movement of fluids through the capillary walk into the tissue depends on hydrostatic pressure.
Osmosis
The process by which fluid moves across a semipermeable membrane from an area of low solute concentration to an area of high solute concentration ; the process continues until the solute concentrations are equil on both sides of the membrane.
Describe the role of the heart in the bodies fluid compustian and volume.
The pumping action of the heart circulates blood through the kidneys under sufficient pressure to allow for urine formation. Failure of this pumping action interferes with renal perfusion and thus with water and electrolyte regulation.
Preventing Fluid Volume Deficit
To prevent FVD, the nurse identifies patients at risk and takes measures to minimize fluid losses. For example, if the patient has diarrhea, diarrhea control measures should be implemented and replacement fluids administered. These measures may include administering antidiarrheal medications and small volumes of oral fluids at frequent intervals.
Sensible perspiration refers to
Visible water and electrolyte loss through the skin, sweating
Describe the role of the kidneys in regulating the body's fluid compustian and volume
Vital to the regulation of fluid and electrolyte balance, the kidneys normally filter 170 L of plasma every day in the adult, while excreting only 1.5 L of urine. They act both autonomously and in response to bloodborne messengers, such as aldosterone and antidiuretic hormone (ADH) (Porth & Matfin, 2009). Major functions of the kidneys in maintaining normal fluid balance include the following: • Regulation of ECF volume and osmolality by selective retention and excretion of body fluids • Regulation of electrolyte levels in the ECF by selective retention of needed substances and excretion of unneeded substances • Regulation of pH of the ECF by retention of hydrogen ions and/or bicarbonate (HCO3) • Excretion of metabolic wastes and toxic substances Given these functions, it is readily apparent that renal failure results in multiple fluid and electrolyte abnormalities. Renal function declines with advanced age, as do muscle mass and daily exogenous creatinine production. Therefore, high-normal and minimally elevated serum creatinine values may indicate substantially reduced renal function in the elderly.
Hypovolemia As soon as the patient becomes normotensive (normalization of their blood pressure),
a hypotonic electrolyte solution (e.g., 0.45% sodium chloride) is often used to provide both electrolytes and water for renal excretion of metabolic wastes.
When fluid balance is critical, all routes of gain and all routes of loss must
be recorded and all volumes compared. Organs of fluid loss include the kidneys, skin, lungs, and GI tract.
Serum sodium must not be increased by more than
by more than 12 mEq/L in 24 hours, to avoid neurologic damage due to osmotic demyelination. This condition may occur when the serum sodium concentration is overcorrected (exceeding 140 mEq/L) too rapidly, causing a relatively hypotonic ICS compared to the ECS. This causes water to flow from the ICS to the ECS, causing cell volume collapse. Osmotic demyelination presents as flaccid paralysis, dysarthria (speech that is slurred, slow, and difficult to produce), dysphagia (difficulty in swallowing), and quadriparesis.
Later, after FVD fully develops, the kidneys attempt to
conserve needed body fluids, leading to a urine output of less than 30 mL/h in an adult. Urine in this instance is concentrated and represents a healthy renal response. Daily body weights are monitored; an acute loss of 0.5 kg (1 lb) represents a fluid loss of approximately 500 mL. (One liter of fluid weighs approximately 1 kg, or 2.2 lb.)
hypervolemia - Nursing care
daily weights and assessment of edema
treatment of hypervolemia includes
diuresis and fluid and sodium restriction
HYPERvolemia S/S -
edema, distended neck veins, crackles, tachycardia; increased BP
Hypovolemia - Accurate and frequent assessment of -
of I&O, weight, vital signs, central venous pressure, level of consciousness, breath sounds, and skin color should be performed to determine when therapy should be slowed to avoid volume overload. The rate of fluid administration is based on the severity of loss and the patient's hemodynamic response to volume replacement.
FVD - Skin and tongue turgor
is monitored on a regular basis. In a healthy person, pinched skin immediately returns to its normal position when released. This elastic property, referred to as turgor, is partially dependent on interstitial fluid volume. In a person with FVD, the skin flattens more slowly after the pinch is released. In a person with severe FVD, the skin may remain elevated for many seconds. Skin turgor is best measured by pinching the skin over the sternum, inner aspects of the thighs, or forehead.
Sodium Replacement For those who cannot consume sodium,
lactated Ringer's solution or isotonic saline (0.9% sodium chloride) solution may be prescribed.
In general, patients with an acute decrease in serum sodium levels have more cerebral edema and higher mortality rates than do those with more slowly developing hyponatremia. Acute decreases in sodium, developing in less than 48 hours,
may be associated with brain herniation and compression of midbrain structures.
FVD - Urine concentration is monitored by
measuring the urine specific gravity. In a volume-depleted patient, the urine specific gravity should be greater than 1.020, indicating healthy renal conservation of fluid.
Conditions associated with SIADH include
oat-cell lung tumors, head injuries, endocrine and pulmonary disorders, physical or psychological stress, and a variety of medications (e.g., vincristine, phenothiazines, tricyclic antidepressants, and thiazide diuretics). SIADH is discussed in more detail in