The Child with Gastrointestinal Dysfunction



The Child with Gastrointestinal Dysfunction


Debi S. Lammert, Kristina D. Wilson and David Wilson



image


evolve.elsevier.com/wong/essentials





Distribution of Body Fluids


The distribution of body fluids, or total body water (TBW), involves the presence of intracellular fluid (ICF) and extracellular fluid (ECF). Water is the major constituent of body tissues, and the TBW in an individual ranges from 45% (in late adolescence) to as much as 75% in term newborns or 90% in extremely preterm infants of total body weight.


Whereas the ICF refers to the fluid contained within the cells, the ECF is the fluid outside the cells. The ECF is further broken down into several components: intravascular (contained within the blood vessels), interstitial (surrounding the cell; the location of most ECF), and transcellular (contained within specialized body cavities such as cerebrospinal, synovial, and pleural fluid). Whereas in a newborn about 50% of the body fluid is contained within the ECF, 30% of a toddler’s body fluid is contained within the ECF.


Maintenance water requirement is the volume of water needed to replace obligatory fluid loss such as that from insensible water loss (through the skin and respiratory tract), evaporative water loss, and losses through urine and stool formation. The amount and type of these losses may be altered by disease states such as fever (with increased sweating), diarrhea, gastric suction, and pooling of body fluids in a body space.


Nurses should be alert for altered fluid requirements in various conditions:


Increased requirements:



Decreased requirements:



Basal maintenance calculations for required body water are based on the body’s requirements for water in a normometabolic state at rest; estimated fluid requirements are then increased or decreased from these parameters based on increased or decreased water losses, such as with elevated body temperature (increased) or heart failure (decreased). Daily maintenance fluid requirements for infants, toddlers, and older children are listed in Table 24-1.These requirements are not appropriate for neonates.



Maintenance fluids contain both water and electrolytes and can be estimated from the child’s age, body weight, degree of activity, and body temperature. Basal metabolic rate (BMR) is derived from standard tables and adjusted for the child’s activity, temperature, and disease state. For example, for afebrile patients at rest, the maintenance water requirement is approximately 100 ml for each 100 kcal expended. Children with fluid losses or other alterations require adjustment of these basic needs to accommodate abnormal losses of both water and electrolytes as a result of a disease state. For example, insensible losses increase when basal expenditure increases by fever or hypermetabolic states. Hypometabolic states, such as hypothyroidism and hypothermia, decrease the BMR.


The percentage of TBW varies among individuals and in adults and older children is related primarily to the amount of body fat. Consequently, females, who have more body fat than males, and obese persons tend to have less water content in relation to weight.



Changes in Fluid Volume Related to Growth


The fetus is composed primarily of water with little tissue substance. As the organism grows and develops, a progressive decrease occurs in TBW with the fastest rate of decline taking place during fetal life. The changes in water content and distribution that occur with age reflect the changes that take place in the relative amounts of bone, muscle, and fat making up the body. At maturity, the percentage of TBW is somewhat higher in the male than in the female and is probably a result of the differences in body composition, particularly fat and muscle content.


Another important aspect of growth change as it corresponds to water distribution is related to the ICF and ECF compartments. In the fetus and prematurely born infants, the largest proportion of body water is contained in the ECF compartment. As growth and development proceed, the proportion within this fluid compartment decreases as the ICF and cell solids increase. The ECF diminishes rapidly from approximately 40% of body weight at birth to less than 30% at 1 year of age. The different effects on boys and girls become apparent at puberty.



Water Balance in Infants


Compared with older children and adults, infants and young children have a greater need for water and are more vulnerable to alterations in fluid and electrolyte balance. Infants have a greater fluid intake and output relative to size. Water and electrolyte disturbances occur more frequently and more rapidly, and infants and children adjust less promptly to these alterations.


The fluid compartments in infants vary significantly from those in adults, primarily because of an expanded extracellular compartment. The extracellular fluid (ECF) compartment constitutes more than half the TBW at birth and has a greater relative content of extracellular sodium and chloride. Infants lose a large amount of fluid at birth and maintain a larger amount of ECF than adults until about 2 years of age. This contributes to greater and more rapid water loss during this age period.


Fluid losses create compartment deficits that are reflected throughout the duration of dehydration. In general, approximately 60% of fluid is lost from the ECF, and the remaining 40% comes from the intracellular fluid (ICF). The amount of fluid lost from the ECF increases with acute illness and decreases with chronic loss.


Fluid losses vary with age and are divided into insensible, urinary, and fecal losses. Approximately two thirds of insensible losses occur through the skin; the remaining third is lost through the respiratory tract. Heat and humidity, body temperature, and respiratory rate influence insensible fluid loss. Infants and children have a greater tendency to become highly febrile than do adults. Fever increases insensible water loss approximately 7 ml/kg/24 hr for each degree rise in temperature above 37.2° C (99° F). Fever and increased surface area relative to volume are factors that contribute to greater insensible fluid losses in young patients.







Disturbances of Fluid and Electrolyte Balance


image Disturbances of fluids and their solute concentration are closely interrelated. Alterations in fluid volume affect the electrolyte component, and changes in electrolyte concentration influence fluid movement. Because intracellular water and electrolytes move to and from the ECF compartment, any imbalance in the ICF is reflected by an imbalance in the ECF. Disturbances in the ECF involve either an excess or a deficit of fluid or electrolytes. Of these, fluid loss occurs more frequently.


image Nursing Care Plan—The Child with Fluid and Electrolyte Disturbances


Depletion of ECF, usually caused by gastroenteritis, is one of the most common problems encountered in infants and children. Until modern techniques for fluid replacement were perfected, gastroenteritis was one of the chief causes of infant mortality. Fluid and electrolyte problems related to specific diseases and their management are discussed throughout the book where appropriate. The major fluid disturbances, their usual causes, and clinical manifestations are listed in Table 24-2. Problems of fluid and electrolyte disturbance always involve both water and electrolytes; therefore, replacement includes administration of both calculated on the basis of ongoing processes and laboratory serum electrolyte values.



TABLE 24-2


DISTURBANCES OF SELECT FLUID AND ELECTROLYTE BALANCE













































MECHANISMS AND SITUATIONS MANIFESTATIONS MANAGEMENT AND NURSING CARE
Water Depletion



Water Excess



Sodium Depletion (Hyponatremia)



Sodium Excess (Hypernatremia)



Potassium Depletion (Hypokalemia)



Potassium Excess (Hyperkalemia)





image


image


ADH, Antidiuretic hormone; BMR, basal metabolic rate; BUN, blood urea nitrogen; CNS, central nervous system; DKA, diabetic ketoacidosis; ECG, electrocardiogram; IV, intravenous.



Water Intoxication


Water intoxication, or fluid volume excess, is observed less often than dehydration. However, it is important that nurses and others who care for children be alert to this possibility in certain situations. Children who ingest excessive amounts of electrolyte-free water develop a concurrent decrease in serum sodium accompanied by central nervous system (CNS) symptoms. There is a large urinary output, and because water moves into the brain more rapidly than sodium moves out, the child may also exhibit irritability, somnolence, headache, vomiting, diarrhea, or generalized seizures. The affected child usually appears well hydrated but may be edematous or even dehydrated.


Fluid intoxication can occur during acute intravenous (IV) fluid replacement, too rapid dialysis, tap water enemas, feeding of incorrectly mixed formula, or excess water ingestion or with too rapid reduction of glucose levels in diabetic ketoacidosis. Patients with CNS infections occasionally retain excessive amounts of water. Administration of inappropriate hypotonic solutions (e.g., 0.45% sodium chloride) may cause a rapid reduction in sodium and result in symptoms of water excess or overload.


Infants are especially vulnerable to fluid volume excess. Their thirst mechanism is not well developed; therefore, they are unable to “turn off” fluid intake appropriately. A decreased glomerular filtration rate does not allow for repeated excretion of a water excess, and antidiuretic hormone (ADH) levels may not be maximally reduced. Consequently, infants are unable to excrete a water excess effectively.


Administration of inappropriately prepared formula is one of the more common causes of water intoxication in infants. Families who cannot afford to buy enough formula may dilute the formula to increase the volume or even substitute water for the formula. A family may run out of formula and dilute the remaining amount to make it last until they are able to purchase more. In addition, water is sometimes used for pacification when the infant is crying or fussy. Water intoxication can also occur in infants who receive overly vigorous hydration during a febrile illness.


A number of clinicians have reported water intoxication in children after swimming lessons. Although they hold their breath, some children apparently swallow a large amount of water during repeated submersion. Anticipatory guidance to parents should include a discussion of swimming instruction and advice to stop a lesson if the child swallows unusual amounts of water or exhibits any symptoms of hyponatremia (see Table 24-2).



Dehydration


Dehydration is a common body fluid disturbance in infants and children and occurs whenever the total output of fluid exceeds the total intake, regardless of the cause. Dehydration may result from a number of diseases that cause insensible fluid losses through the skin and respiratory tract, through increased renal excretion, and through the GI tract. Although dehydration can result from impaired oral intake, it is often a result of abnormal losses, such as those that occur in vomiting or diarrhea, when oral intake only partially compensates for the abnormal losses. Other significant causes of dehydration include diabetic ketoacidosis and burns.



Types of Dehydration

image The pathophysiology of dehydration is understood by recognizing that the distribution of water between the ECF and ICF spaces depends on active transport of potassium into and sodium out of cells by energy-requiring processes. Sodium is the chief solute in ECF and is the primary determinant of ECF volume. Sodium is considered a unique electrolyte in that water balance determines sodium concentration; when water is lost and sodium concentration becomes elevated compensatory mechanisms in the kidney stop ADH secretion so water is retained. The thirst mechanism (not fully functional in infants) is also stimulated so water is replaced, thus increasing the total body water content and returning sodium to a normal level (Greenbaum, 2011). Potassium is primarily found inside the cell (intracellular) but small amounts are also found in extracellular fluid. Sodium depletion in diarrhea occurs in two ways: out of the body in stool and into the ICF compartment to replace potassium to maintain electrical equilibrium.


image Case Study—Dehydration and Diarrhea


Dehydration is classified into three categories on the basis of osmolality and depends primarily on the serum sodium concentration: (1) isotonic, (2) hypotonic, and (3) hypertonic.


Isotonic (isosmotic or isonatremic) dehydration, the primary form of dehydration in children, occurs in conditions in which electrolyte and water deficits are present in approximately balanced proportions. Water and sodium are lost in approximately equal amounts. The observable fluid losses are not necessarily isotonic because losses from other avenues make adjustments so that the sum of all losses, or the net loss, is isotonic. There is no osmotic force between the ICF and the ECF, so the major loss is sustained from the ECF compartment. This significantly reduces the plasma volume and the circulating blood volume, which affects the skin, muscles, and kidneys. Shock is the greatest threat to life, and children with isotonic dehydration display symptoms characteristic of hypovolemic shock. Plasma sodium remains within normal limits, between 130 and 150 mEq/L.


Hypotonic (hyposmotic or hyponatremic) dehydration occurs when the electrolyte deficit exceeds the water deficit, leaving the serum hypotonic. Because ICF is more concentrated than ECF in hypotonic dehydration, water moves from the ECF to the ICF to establish osmotic equilibrium. This movement further increases the ECF volume loss, and shock is a frequent finding. Because there is a greater proportional loss of ECF in hypotonic dehydration, the physical signs tend to be more severe with smaller fluid losses than with isotonic or hypertonic dehydration. Serum sodium concentration is less than 130 mEq/L.


Hypertonic (hyperosmotic or hypernatremic) dehydration results from water loss in excess of electrolyte loss and is usually caused by a proportionately larger loss of water or a larger intake of electrolytes. This type of dehydration is the most dangerous and requires more specific fluid therapy. Hypertonic diarrhea may occur in infants who are given fluids by mouth that contain large amounts of solute, or in children who receive high-protein nasogastric (NG) tube feedings that place an excessive solute load on the kidneys. In hypertonic dehydration, fluid shifts from the lesser concentration of the ICF to the ECF. Plasma sodium concentration is greater than 150 mEq/L.


Because the ECF volume is proportionately larger, hypertonic dehydration consists of a greater degree of water loss for the same intensity of physical signs. Shock is less apparent. However, CNS disturbances, including alterations in consciousness, poor ability to focus attention, lethargy, increased muscle tone with hyperreflexia, and hyperirritability to stimuli, are more likely to occur. CNS changes are serious and may result in permanent damage.



Degree of Dehydration

Diagnosis of the type and degree of dehydration is necessary to develop an effective plan of therapy. The degree of dehydration has been described as a percentage of body weight dehydrated: mild—less than 3% in older children or less than 5% in infants; moderate—5% to 10% in infants and 3% to 6% in older children; and severe—more than 10% in infants and more than 6% in older children (Greenbaum, 2011). Water constitutes only 60% to 70% of an infant’s weight. However, adipose tissue contains little water and is highly variable in individual infants and children. A more accurate means of describing dehydration is to reflect acute loss (time frame of ≤48 hours) in milliliters per kilogram of body weight. For example, a loss of 50 ml/kg is considered to be a mild fluid loss, but a loss of 100 ml/kg produces severe dehydration. Weight is the most important determinant of the percent of total body fluid loss in infants and younger children. However, often the pre-illness weight is unknown. Other predictors of fluid loss include a changing level of consciousness (irritability to lethargy), altered response to stimuli, decreased skin elasticity and turgor, prolonged capillary refill (>2 sec), increased heart rate, and sunken eyes and fontanels.


Clinical signs provide clues to the extent of dehydration (Table 24-3). The earliest detectable sign is usually tachycardia followed by dry skin and mucous membranes, sunken fontanels, signs of circulatory failure (coolness and mottling of extremities), loss of skin elasticity, and prolonged capillary filling time (Table 24-4).




Compensatory mechanisms attempt to maintain fluid volume by adjusting to these losses. Interstitial fluid moves into the vascular compartment to maintain the blood volume in response to hemoconcentration and hypovolemia, and vasoconstriction of peripheral arterioles helps maintain pumping pressure. When fluid losses exceed the body’s ability to sustain blood volume and blood pressure, circulation is seriously compromised, and the blood pressure falls. This results in tissue hypoxia with accumulation of lactic acid, pyruvate, and other acid metabolites, which contribute to the development of metabolic acidosis.


Renal compensation is impaired by reduced blood flow through the kidneys, and little urine is formed. Increased serum osmolality stimulates the secretion of ADH to conserve fluid and initiates the renin–angiotensin mechanisms in the kidney, causing further vasoconstriction. Aldosterone is released to promote sodium retention and conserve water in the kidneys. If dehydration increases in severity, urine formation is greatly diminished, and metabolites and hydrogen ions that are normally excreted by this route are retained.


Shock, a common manifestation of severe depletion of ECF volume, is preceded by tachycardia and signs of poor perfusion and tissue oxygenation (by pulse oximeter readings). Peripheral circulation is poor as a result of reduced blood volume; therefore, the skin is cool and mottled, with decreased capillary filling after blanching. Impaired kidney circulation often leads to oliguria and azotemia. Although low blood pressure may accompany other symptoms of shock, in infants and young children, it is usually a late sign and may herald the onset of cardiovascular collapse.



Diagnostic Evaluation

image To initiate a therapeutic plan, several factors must be determined:



image Case Study—Dehydration


Initial and regular ongoing evaluations assess the patient’s progress toward equilibrium and the effectiveness of therapy.


In the examination of an infant or younger child, one of the most important determinants of the extent of dehydration is body weight because this can assist in determining the percentage of total body fluid lost; however, because the pre-illness weight is often unknown, clinical manifestations must be evaluated. Important clinical manifestations include changing sensorium (irritability to lethargy); decreased response to stimuli; integumentary changes (decreased elasticity and turgor); prolonged capillary refill; increased heart rate; sunken eyes; and, in infants, sunken fontanels. Using multiple predictors increases the sensitivity of assessing the fluid deficit, and early studies have shown a reasonably high degree of agreement between experienced observers in assessment of the level of dehydration. Objective signs of dehydration are present at a fluid deficit of less than 5%.


Laboratory data are said to be useful only when results are significantly abnormal (Emond, 2009). Urine specific gravity, urine ketones, and urinary output during rehydration are reportedly unreliable assessments for determining dehydration in children (Steiner, Nager, and Wang, 2007). Shock, tachycardia, and very low blood pressure are common features of severe depletion of ECF volume (see Shock, Chapter 25).



Therapeutic Management

Medical management is directed at correcting the fluid loss or deficit and treating the underlying cause. When the child is alert, awake, and not in danger, correction of dehydration may be attempted with oral fluid administration. Mild cases of dehydration can be managed at home by this method. Several commercial rehydration fluids are available for use (Table 24-5). Oral rehydration management consists of replacement of fluid loss over 4 to 6 hours, replacement of continuing losses, and provision for maintenance fluid requirements. In general, a mildly dehydrated child may be given 50 ml/kg of oral rehydration solution (ORS), and a child with moderate dehydration may be given 100 ml/kg of ORS. A child with fluid losses from diarrhea may be given 10 ml/kg for each stool. Amounts and rates are determined from body weight and the severity of dehydration and are increased if rehydration is incomplete or if excess losses continue until the child is well hydrated and the basic problem is under control.



The child may not be thirsty even though dehydrated and may refuse oral fluids initially for fear of continued emesis (if occurring) or because of decreased strength, oral stomatitis, or thrush. In such children, rehydration may proceed by administering 2 to 5 ml of ORS by a syringe or small medication cup every 2 to 3 minutes until the child is able to tolerate larger amounts; if the child has emesis, administering small amounts (5–10 ml) of ORS every 5 minutes or so may help overcome fluid deficit, and the emesis will often lessen over time. Oral administration of ondansetron (Zofran) to children with acute gastroenteritis and vomiting may reduce emesis and increase time to oral rehydration, thus preventing IV therapy. Oral rehydration therapy (ORT) is effective for treating mild or moderate dehydration in children, is less expensive, and involves fewer complications than parenteral therapy (American Academy of Pediatrics [AAP], Committee on Infectious Diseases and Pickering, 2009).




Parenteral Fluid Therapy.

Parenteral fluid therapy is initiated whenever the child is unable to ingest sufficient amounts of fluid and electrolytes to (1) meet ongoing daily physiologic losses, (2) replace previous deficits, and (3) replace ongoing abnormal losses. Patients who usually require IV fluids are those with severe dehydration, those with uncontrollable vomiting, those who are unable to drink for any reason (e.g., extreme fatigue, coma), and those with severe gastric distention.


Because dehydration constitutes a great threat to life, the first priority is the restoration of circulation by rapid expansion of the ECF volume to treat or prevent shock. IV administration of fluid begins immediately, although the exact nature of the dehydration and the serum electrolyte values may not initially be known. The solution selected is based on what is known regarding the probable type and cause of the dehydration. This usually involves an isotonic solution such as 0.9% sodium chloride or lactated Ringer solution, both of which are close to the body’s serum osmolality of 285 to 300 mOsm/kg and do not contain dextrose (which is contraindicated in the early treatment stages of diabetic ketoacidosis).


Parenteral rehydration therapy has three phases. The initial therapy is used to expand ECF volume quickly and to improve circulatory and renal function. During initial therapy, an isotonic solution is used at a rate of 20 ml/kg, given as an IV bolus over 20 minutes, and repeated as necessary after assessment of the child’s response to therapy (Ford, 2009; Friedman, 2010). Subsequent therapy is used to replace deficits, meet maintenance water and electrolyte requirements, and catch up with ongoing losses. Water and sodium requirements for the deficit, maintenance, and ongoing losses are calculated at 8-hour intervals, taking into consideration the amount of fluids given with the initial boluses and the amount administered during the first 24-hour period. With improved circulation during this phase, water and electrolyte deficits can be evaluated, and acid–base status can be corrected either directly through the administration of fluids or indirectly through improved renal function. Potassium is withheld until kidney function is restored and assessed and circulation has improved (see Evidence-Based Practice box).



Evidence-Based Practice


Normal Saline or Heparinized Saline Flush Solution in Pediatric Intravenous Lines






Critically Analyze the Evidence




• In trials of HS administration versus NS, placebo, or no treatment in neonates, no strong evidence regarding the effectiveness and safety of heparin in prolonging catheter life was found (Shah, Ng, and Sinha, 2005).


• No significant statistical difference was found between HS and NS flushes for maintaining catheter patency in children (Hanrahan, Kleiber, and Berends, 2000; Hanrahan, Kleiber, and Fagan, 1994; Heilskov, Kleiber, Johnson, and others, 1998; Kotter, 1996; Mok, Kwong, and Chan, 2007; Schultz, Drew, and Hewitt, 2002).


• Increased incidence of pain or erythema was associated with HS flushing of infusion devices (Hanrahan, Kleiber, and Fagan, 1994; McMullen, Fioravanti, Pollack, and others, 1993; Nelson and Graves, 1998; Robertson, 1994).


• Increased patency or longer dwell times were found with HS solutions versus NS in 24-gauge catheters (Beecroft, Bossert, Chung, and others, 1997; Danek and Noris, 1992; Gyr, Burroughs, Smith, and others, 1995; Hanrahan, Kleiber, and Berends, 2000; Mudge, Forcier, and Slattery, 1998; Tripathi, Kaushik, and Singh, 2008).


• Younger children and preterm neonates with lower gestational ages were associated with shorter patency of IV catheters (McMullen, Fioravanti, Pollack, and others, 1993; Paisley, Stamper, Brown, and others, 1997; Robertson, 1994; Tripathi, Kaushik, and Singh, 2008).


• Infusion devices flushed with NS lasted longer than those flushed with HS (Goldberg, Sankaran, Givelichian, and others, 1999; Le Duc, 1997; Nelson and Graves, 1998).


• When measured and reported, the length of time between flushing peripheral devices affected dwell time (Crews, Gnann, Rice, and others, 1997; Gyr, Burroughs, Smith, and others, 1995).


• Preterm neonates are at higher risk for development of clotting problems as a result of heparin; none of the studies cited anticoagulation-associated complications with HS (Klenner, Fusch, Rakow, and others, 2003).


• 0.9% sodium chloride injection is safe for maintaining patency of peripheral locks in adults and children older than age 12 years (American Society of Hospital Pharmacists, 2006).


• Either preservative-free heparin or preservative-free 0.9% sodium chloride may be used to flush a peripheral IV; however, catheter patency may be maintained by flushing with saline when converting from continuous to intermittent use (Infusion Nurses Society, 2006).


• After each catheter use, peripheral catheters should be locked with preservative-free 0.9% sodium chloride (Infusion Nurses Society, 2011).


• No recommendation is made for use of preservative-free 0.9% sodium chloride versus heparin for locking peripheral catheters (Infusion Nurses Society, 2011).

Jan 16, 2017 | Posted by in NURSING | Comments Off on The Child with Gastrointestinal Dysfunction
Premium Wordpress Themes by UFO Themes