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Fluids & Electrolytes
In this case study report of an infant with metabolic alkalosis, the healthcare team worked to discover the cause of the illness. They found that well-meaning parents had diluted their newborn's powdered formula with electrolyte-enhanced water. Electrolyte balance in the newborn is reviewed in this article, along with information about enhanced waters. It is essential that nurses working with new families be aware that heavily advertised enhanced waters could be used unknowingly by parents for their newborns, and that the consequences could be dire.
This is the story of parents who wanted to do the right thing for their infant, but unknowingly were influenced by advertising, and wound up with a sick baby.
The World Health Organization recommends exclusive breastfeeding for the first 6 months of life, a recommendation generally supported by other health advisory groups (Venter & Dean, 2008). Breast milk is composed of over 300 components, while commercially prepared formula contains approximately 75 components (Venter & Dean, 2008). Human milk is specific to the infant, and is unlike any marketed feeding preparation (Gartner & Eidelman, 2005). Breast milk evolves as the infant grows, changing to provide the most appropriate nutrition for the child at their stage of development (Wagner, Graham, & Hope, 2006). Breast milk also conveys significant benefits to the infant, including a decrease in the incidence or severity of a wide range of infectious diseases such as respiratory tract infection, necrotizing enterocolitis, and otitis media, a decreased risk for sudden infant death syndrome, type 1 and type 2 diabetes, and some forms of cancer (Gartner & Eidelman, 2005). Additionally, research suggests that breastfeeding is associated with enhanced cognitive development (Gartner & Eidelman, 2005).
Spatz (2006) identifies several important steps in encouraging the new mother to breastfeed, including a focus on provision of milk, rather than breastfeeding, as some mothers may choose to bottle-feed breast milk. Nurses must also focus on providing information to the mother and family on the benefits of human milk, and establishing and maintaining an adequate milk supply. We know as nurses, however, that some mothers may not desire to breastfeed, or may be unable to breastfeed, and may instead use formula. This case study concerns a woman who chose to feed her infant with prepared formula, had the baby's best interests at heart, but unknowingly chose an unconventional, and eventually a detrimental way to dilute the formula. The components of formula are meant to closely mimic breast milk. In both breast milk and infant formula, over half of the calories come from fat. Carbohydrates may be in the form of lactose (as in cow's milk formulas) or sucrose or cornstarch in soy-based formulas. Vitamins and minerals, usually in amounts specified by the FDA, are also added to infant formula.
A twenty-day-old female "Mary" was brought to the pediatrician's office for a worsening cough and respiratory distress. After being evaluated by the physician, she was admitted to the pediatric unit of the local hospital for hypoxemia, poor oral intake, respiratory distress, and respiratory syncytial virus bronchiolitis. Prior to this episode, Mary had an uncomplicated prenatal and neonatal course.
During the course of her hospitalization the parents mentioned that they had been diluting Mary's brand name powdered formula with an electrolyte-enhanced water. Electrolyte waters are being marketed aggressively in the United States, and the manufacturer of this particular product advertises it as "vapor distilled" and as (water in) "its purest original state." The packaging does state that the water contains calcium chloride, magnesium chloride, and potassium bicarbonate, but it became clear to us in the course of working with this family that merely labeling the water meant nothing to the new parents. They had no understanding at all that it could be dangerous to their child to use this enhanced water to dilute formula. For many new parents, the idea of water in "its purest original state" may be appealing, and may lead them to believe that this is a "healthier" alternative to tap or bottled water for their infant. In this case, the parents told us that they thought this was merely another form of distilled water, which was appropriate to use to dilute the child's formula.
Mary's electrolytes upon admission showed a hyperkalemic metabolic alkalosis with an elevated calcium. Her sodium was 138, potassium was 5.8, chloride was 100, and carbon dioxide (CO2) was 33. Her blood urea nitrogen was 6, creatinine was 0.3, glucose was 83, her calcium was elevated to 10.4, and her magnesium was 2.2. Table 1 shows arterial blood gas values and variances in newborns.
Body fluids contain acids made of positively charged hydrogen ions (H+) and anions, or negatively charged ions (Clancy & McVicar, 2007). The measure of a solution's acidity or alkalinity is the pH. Clancy and McVicar state that "the neutral point (pH of pure water) relates to a situation in which acid ions (hydrogen [H+]) and alkali ions (hydroxyl [OH-]) are equal" (p. 1017). A solution with a pH of less than 7 is considered acid, while a solution with a pH of greater than 7 is considered alkaline, often called "base" (Clancy & McVicar). The arterial blood pH shows the balance between CO2, an acid, and bicarbonate (HCO3), a base. The buffer system of the body acts to regulate the acid-base balance; if there are excess hydrogen ions in the body fluid, the body will release acid buffers, while if the body fluid is deficient in hydrogen ions, the buffer system will cause the release of alkaline buffers, chemicals which release hydrogen ions (Clancy & McVicar). Further compensation may be either metabolic or respiratory. In a case of respiratory acidosis, for example, the kidneys will attempt to compensate by reabsorbing HCO3- and excreting hydrogen ions, while with respiratory alkalosis, the kidneys will secrete HCO3- and reabsorb hydrogen ions (Roman, Thimothee, & Vidal, 2008).
The body's acid-base balance is controlled by the renal and respiratory systems. The kidneys maintain the composition of the extracellular and intracellular fluid and regulate acid-base balance by secreting hydrogen ions, reabsorbing sodium and bicarbonate ions, acidifying phosphate salts, and producing ammonia (Pathophysiology Made Incredibly Easy, 1998). The respiratory system helps to modify the acid-base balance of the body by increasing respiration in acidosis (to excrete excess CO2) or decreasing respirations in alkalosis.
To evaluate an arterial blood gas reading, it is necessary to discover whether the pH is normal (7.35-7.45), elevated, or decreased. If the pH is >7.45, the patient is alkalotic, and if it is <7.35, the patient is acidotic. The second step is to evaluate the PaCO2 to determine if the imbalance is respiratory or metabolic. If the pH and the PaCO2 move in opposite directions (i.e., the pH is decreased and the PaCO2 is elevated), then the problem is respiratory (Roman et al., 2008). The third step is to assess the HCO3; if the problem is metabolic the pH and HCO3 will move in the same direction (i.e., both will be elevated or decreased) (Roman et al.). The body strives to maintain homeostasis by normalizing the pH. In cases of compensated acid-base abnormalities, the patient will have a normal pH but an increased or decreased CO2 or HCO3 (Roman et al.). In Mary's case, her arterial blood gas demonstrated a metabolic alkalosis (evidenced by an elevated bicarbonate) with respiratory compensation (evidenced by her elevated PCO2).
This acid-base disturbance is caused by an elevation in plasma bicarbonate concentration (Huang & Priestley, 2008). It is often classified as chloride-responsive (indicated by a urine chloride level of less than 10 mEq/L) or chloride-resistant (indicated by a urine chloride level of more than 20 mEq/L) (Huang & Priestley). Metabolic alkalosis is most often caused by a loss of hydrochloric acid through the GI tract, as from vomiting (Huang & Priestley). Potential sequelae associated with metabolic alkalosis in the infant include hypoxemia, respiratory arrest, life-threatening cardiac arrhythmias, and seizures (Huang & Priestley).
This is an acid-base disturbance typically caused by an underlying hypoxia, metabolic acidosis, or stimulation of respiration by the central nervous system (Mancini & Deshpande, 2006). Sequelae from respiratory alkalosis may include altered mentation, seizures, and very rarely, dysrhythmias in patients with underlying cardiac disease (Mancini & Deshpande).
This acid-base disturbance is characterized by a decreased serum pH resulting from a decrease in plasma bicarbonate concentration or an increase in hydrogen ion concentration (Priestley, 2006). Causes may include undiagnosed diabetes mellitus and diabetic ketoacidosis, toxin ingestion (including salicylates or ethanol), or sepsis. Clinical findings may include lethargy, coma, seizures, hyperventilation or Kussmaul's respirations, and signs of dehydration or low cardiac output (Priestley).
This acid-base disturbance is characterized by an increased PCO2 resulting from an imbalance between carbon dioxide production by the body and excretion from the lungs (Priestley & Litman, 2009). Clinical manifestations may include depressed consciousness and a hyperdynamic cardiovascular state characterized by tachycardia, high cardiac output, and decreased systemic vascular resistance (Priestley & Litman).
In order to better understand what was going on with Mary, we contacted the company which manufactured the particular electrolyte water the parents had used to dilute the powdered formula, and they told us that there are 10mg per liter of calcium chloride, 10mg per liter of magnesium, and 15mg per liter of potassium bicarbonate. Mary's electrolytes revealed an underlying metabolic alkalosis with respiratory compensation, as her pH was 7.43, PCO2 49.6, and her bicarbonate was 32.2 with a base excess of 6.5. Bicarbonate levels were monitored throughout the course of her admission, and this value actually increased to 34.8 approximately 24 hours into her hospitalization, although her potassium decreased to 5.4 and her calcium decreased to 10.1.
During her hospitalization, Mary's cardiopulmonary status and oxygen saturations were closely monitored. She received oxygen initially to maintain a saturation of 92%, although later in the course of the hospitalization this goal was changed to 88%. She was fed breast milk and Pedialyte ad lib, and her intake, output, and daily weights were closely monitored. Saline wash and suctioning were ordered as needed, and acetaminophen was given every 4 hours as needed for fever or irritability. A chest X-ray was obtained which demonstrated a mild degree of atelectasis or infiltrate. A pediatric cardiology consult was obtained for a grade 2/6 heart murmur and an isolated elevated blood pressure. The murmur was identified as a pulmonary outflow murmur with no treatment required, and the elevated blood pressure was most likely an erroneous reading. An echocardiogram revealed a structurally normal heart with normal function. She did not receive intravenous fluids or medications, and her acid-base imbalance was monitored closely and resolved on its own.
Mary was hospitalized for 4 days. At the time of discharge, Mary's electrolytes had normalized and her elevated bicarbonate had resolved. The last electrolyte panel showed a sodium of 137, a potassium of 6.9 (but with a hemolyzed specimen), a chloride of 99, a CO2 of 27.7, a BUN of 8, a creatinine of 0.2, a glucose of 91, and a normal AST and ALT. Her albumin was 3.8, protein was 6.5, calcium was 10.6, bilirubin was 0.3, and alkaline phosphatase was normal at 234. The oxygen was weaned to one-thirty-second liter per minute via nasal cannula; however, she did at times require O2 of up to one-quarter of a liter and so was discharged home with home O2 and pulse oximetry.
Mary's case was interesting and frightening for us, for she had demonstrated a marked metabolic alkalosis, and it was important that everyone understand why this had happened. With the diagnosis of respiratory syncytial virus bronchiolitis one would expect the child to be acidotic, which may suggest that without the concurrent infection this child would have demonstrated a more severe alkalosis. While it is possible that this child's tachypnea would lead to an alkalotic state, it was clear to us that Mary had a metabolic, not a respiratory, alkalosis.
An extensive literature review revealed no publications addressing the issue of giving formula mixed with electrolyte-enhanced waters to infants. One Web site "Ask Dr. Sears" had a few sentences advising parents not to dilute formula with these waters (http://www.askdrsears.com/faq/fo3.asp).
This case makes it abundantly clear that parent education needs to include appropriate education about feeding with powdered formula:
1. Enhanced vitamin waters should not be used to dilute infant formula.
2. If using a ready to feed formula, do not dilute further with water or any other liquid.
3. If using a concentrated infant formula, mix exactly according to directions on the package.
4. Tap water used to reconstitute infant formula should be boiled for 1 to 2 minutes to eliminate bacterial contamination. It must then be allowed to cool fully before diluting formula.
5. Unused, diluted formula should be refrigerated immediately.
The importance of parent education before and after birth cannot be overstated. It is imperative that nurses continuously assess parental knowledge and educational needs, especially as it relates to proper feeding methods and signs and symptoms of feeding problems. Additionally, familiarity with normal infant blood gas values and potential sequelae associated with acid-base disturbances allows the nurse to remain vigilant for potential complications.
This case study highlights the need for continuing and increased pre- and postnatal education about the nutritional needs of infants and the proper procedures for diluting formula. As the product involved in this case and other enhanced waters become ever more popular among Americans, the need for parental education will grow. Discussion of the potential hazards of the use of electrolyte-enhanced water to dilute formula may prevent infant morbidity such as the marked metabolic alkalosis experienced by the infant in this case study.
The author thanks Dr. Michael Garver for his assistance with this project.
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