Article
The Healthy Newborn Hydration Model: A New Model for Understanding Newborn Hydration Immediately After Birth
Biological Research for Nursing 2015, Vol. 17(1) 94-99 ª The Author(s) 2014 Reprints and permission: sagepub.com/journalsPermissions.nav DOI: 10.1177/1099800414529362 brn.sagepub.com
Pamela J. Mulder, PhD, RN1, and Sue E. Gardner, PhD, RN, FAAN1
Abstract The normal small volume of breast milk produced in the first 2 days following birth may raise concerns about adequate hydration in breast-fed newborns. These concerns are further magnified when breast-fed infants lose ≥ 7% of their birth weight within 2 days postnatally. Weight loss following birth is presumably mostly water loss that could result in hypohydration and subsequent hypernatremic dehydration. However, excess fluid loss immediately following birth is a normal and necessary process. Furthermore, newborns exposed to excess fluid intake during labor may need to lose ≥ 7% of birth weight in the first 2 days following birth in order to achieve euhydration. Normal newborn fluid loss following birth confounds the use of weight loss as the sole measure of newborn hydration. We thus propose the healthy newborn hydration model that highlights the normalcy of newborn weight loss immediately following birth and the healthy newborn’s compensatory mechanisms for preserving adequate hydration. We also recommend the use of serum sodium to measure intravascular osmolarity in addition to monitoring weight loss to obtain a more comprehensive newborn hydration assessment. Research is necessary in healthy newborns to identify relationships among fluids received in utero, newborn weight loss, and hydration, as evaluated with laboratory measures, in the first 2 days following birth. This information will guide clinicians in correctly identifying newborns with inadequate hydration who are in need of supplementary fluids versus newborns with adequate hydration for whom exclusive breast-feeding can be supported and encouraged. Keywords newborn, hydration, weight loss, breast-feeding
Promoting breast-feeding and preventing dehydration in the newborn are important, but often considered competing, health objectives (Fawke, Whitehouse, & Kudumula, 2008). Exclusive breast-feeding for 6 months, a national health priority, is known to decrease infectious diseases and sudden infant death syndrome in infants, type 1 diabetes and leukemia in children, and obesity and type 2 diabetes in adulthood (Ip et al., 2007; U.S. Department of Health and Human Services, 2011, n.d.). Yet, only 13% of infants in the United States exclusively breast-feed for 6 months (Centers for Disease Control and Prevention, 2007). If 90% of infants in the United States were exclusively breast-fed, US$13 billion per year would be saved and over 900 deaths would be prevented (Bartick & Reinhold, 2010). Exclusive breast-feeding ends for more than half a million infants each year because they are supplemented with formula in the hospital following birth in spite of evidence showing that formula supplementation significantly increases the risk of breast-feeding cessation (Dabritz, Hinton, & Babb, 2010; Declercq, Labbok, Sakala, & O’Hara, 2009; Forde & Miller, 2010; Martin et al., 2012; Semenic, Loiselle, & Gottlieb, 2008; U.S. Department of Health and Human Services, 2007). Formula supplementation is a common practice when newborn weight loss is 7% because this threshold is accepted
as a strong indicator of a water deficit (hypohydration) due to inadequate breast milk intake in the newborn (Academy of Breastfeeding Medicine Protocol Committee, 2009; American Academy of Pediatrics, 2005; Shirreffs, 2003). Hypohydration is associated with acute renal failure, brain edema, seizures, and death (Unal, Arhan, Kara, Uncu, & Aliefendioglu, 2008). Therefore, clinicians tend to aggressively diagnose and treat hypohydration, leading to formula supplementation and the demise of breast-feeding for a substantial number of infants. A goal of Healthy People 2020 is to decrease formula supplementation in the ‘‘first 2 days of life’’ by 10% (U.S. Department of Health and Human Services, n.d.). This goal is consistent with the fact that most of the evidence linking excessive weight loss (EWL; i.e., 7%) with hypernatremic dehydration (serum sodium 150 mEq/L) was derived from newborns 3 days old (Koklu et al., 2007; Moritz, Manole, 1
College of Nursing, University of Iowa, Iowa City, IA, USA
Corresponding Author: Pamela J. Mulder, PhD, RN, College of Nursing, University of Iowa, Iowa City, IA 52242, USA. Email: [email protected]
Downloaded from brn.sagepub.com at FRESNO PACIFIC UNIV on December 25, 2014
Mulder and Gardner
95
Healthy Newborn Hydration Model Pregnancy
Labor
Birth
Maternal Fluids Oxytocin Fetal AVP Fetal fluid shift from intravascular to interstitial Output Fetal Hyperhydration Serum Na, ECF
0–24 Hours Colostrum Infant Formula Newborn AVP Newborn fluid shift from interstitial to intravascular Output
Newborn Hyperhydration Serum Na, ECF
24–60 Hours
Weight Loss
Newborn Euhydration Normal Serum Na, Normal ECF
Figure 1. Healthy newborn hydration model. A pictorial model describing the influences of maternal, fetal, and newborn variables on newborn hydration from pregnancy to 60 hr following birth. AVP ¼ arginine vasopressin; ECF ¼ extracellular fluid; Na ¼ sodium.
Bogen, & Ayus, 2005; Pelleboer et al., 2009; Unal et al., 2008; Wang et al., 2007). Unfortunately, the threshold of 7% has been extrapolated to infants in the first 2 days of life, leading to earlier formula supplementation. One possible approach to achieving the Healthy People goal is to reexamine the practice of relying solely on this weight loss threshold to drive formula supplementation in the first 2 days of life (Chantry, Nommsen-Rivers, Peerson, Cohen, & Dewey, 2011; Mulder, Johnson, & Baker, 2010; Noel-Weiss, Courant, & Woodend, 2008). The purpose of this article is to propose a new model for examining and evaluating hydration status in the healthy newborn in the first 24–60 hr following birth and to recommend using laboratory measures of hydration in addition to monitoring weight loss in this evaluation. We suggest that the use of weight loss in the first 24–60 hr following birth as a sign of hypohydration is confounded by the natural process of newborn diuresis, resulting in a large number of false-positive diagnoses of hypohydration. We also delineate further research necessary to examine the diagnostic validity of any weight loss threshold, and the utility of laboratory measures of hydration is also delineated.
Weight Loss Immediately Following Birth Weight loss in the first 2–3 days following birth is a normal, physiologic, and necessary event during the newborn’s transition to extrauterine life (Blackburn, 2007; Tender et al., 2009). Therefore, large weight losses at this time may be a normal physiologic reaction to receiving a large fluid load during labor and may not be associated with hypohydration, inadequate breast milk production, or illness (Chantry et al., 2011; Mulder et al., 2010; Okumus et al., 2011). The relationships among newborn hydration, breast milk intake, urine output, and weight loss in the first 24–60 hr following birth are not fully understood (Dollberg, Lahav, & Mimouni, 2001). Little is known about the physiology of the lactating breast, and the normal trajectory of breast milk production has not been established (Hartmann, 2007). Further, there is not adequate research to differentiate between a physiologic or pathologic weight loss in breast-fed newborns or to identify the morbidity or mortality associated with newborn weight loss (Noel-Weiss
et al., 2008; Oddie, Richmond, & Coulthard, 2001; Unal et al., 2008; Wright & Parkinson, 2004). Breast-fed newborns are expected to lose 4–7% of their birth weight, start gaining weight at 3 days, and return to birth weight at 7–10 days (Macdonald, Ross, Grant, & Young, 2003; Wright & Parkinson, 2004). At the age of 3 days, most breast-fed newborns reach their weight loss nadir and begin gaining weight, concurrent with mothers experiencing lactogenesis II, a dramatic increase in breast milk production (Wright & Parkinson, 2004). Delayed (>72 hr following birth) or absent lactogenesis II is associated with EWL and hypernatremic dehydration (Dewey, Nommsen-Rivers, Heinig, & Cohen, 2003). Before 3 days of age, however, breast-fed newborns consume minimal breast milk (Santoro, Martinez, Ricco, & Jorge, 2010). Dommelen, Wouwe, Breuning-Boers, Buuren, and Verkerk (2007) theorized that ‘‘it takes some time before insufficient breast feeding leads to weight loss’’ (p. 492). We suggest that even EWLs (7%) in the first 24–60 hr following birth could be physiologic and healthy when no other signs of illness are present because newborns are hyperhydrated at birth (Blackburn, 2007; Modi, 2003). The loss of fluid is necessary to restore euhydration and achieve cardiopulmonary adaptation to the extrauterine environment (Modi, 2003). This proposition is based on the following model.
A New Model In the healthy newborn hydration model (see Figure 1), the healthy, full-term mother and fetus are presumed hyperhydrated at admission to labor and delivery, per existing evidence about maternal and fetal hydration. Although maternal physiologic changes in pregnancy include both sodium and water retention, increases in fluid volume (6–8 L of water) outweigh sodium retention, so that levels of serum sodium and plasma osmolarity are decreased (Blackburn, 2007). Larsson, Palm, Hansson, and Axelsson (2008) reported a downward shift in the reference range for serum sodium prior to delivery (124.0–140.4 mmol/L), as compared to healthy, fertile, nonpregnant women (136.7–144.8 mmol/L). These changes contribute to dilutional hyperhydration. The fetus is also hyperhydrated because the
Downloaded from brn.sagepub.com at FRESNO PACIFIC UNIV on December 25, 2014
96
Biological Research for Nursing 17(1)
fetus remains in fluid and electrolyte balance with the mother (Blackburn, 2007). The onset of labor further favors fetal hyperhydration because the fetus vastly increases the production of arginine vasopressin (AVP; Blackburn, 2007; Leung et al., 1980; Tsukahara et al., 2002). AVP increases water retention by the fetal kidneys (Ranadive & Rosenthal, 2011) up to the fetus’ maximum urine-concentrating ability (Blackburn, 2007). During labor, fetal capillary permeability increases, prompting a shift of intravascular fluid to the interstitial compartment. Evidence supports the proposition that a significant proportion of newborns are mildly hyponatremic at birth due to dilutional fetal hyperhydration. Hyponatremia has been defined as a serum sodium level that is less than 133–135 mEq/L (Marcialis, Dessi, Pintus, Marinelli, & Fanos, 2012). Martinerie and colleagues (2009) reported a mean serum sodium concentration of 132.6 mmol/L among 48 healthy, vaginally delivered, fullterm newborns whose mothers did not receive any intravenous fluid before delivery. Describing differences between newborns with and without birth asphyxia, Basu, Som, Das, and Choudhuri (2010) reported that control infants had a mean serum sodium concentration of 138.8 mEq/L (standard deviation [SD] ¼ 2.7). Assuming serum sodium was normally distributed, these results indicate that almost half of the healthy infants had serum sodium values ranging from 130.7 to 138.8 (mean + 3 SD). Basu and colleagues did not describe whether mothers received intravenous fluid in labor or how much they might have received. Moen, Brudin, Rundgren, and Irestedt (2009) reported that 26% of mothers who received more than 2,500 ml of fluid in labor had hyponatremia (plasma sodium 130 mmol/L) immediately following birth, and their newborns were significantly more likely to have EWL. Numerous case studies have also described mothers in labor with excessive fluid intake (3–4 L/day) resulting in newborns with clinically significant hyponatremia (
The Healthy Newborn Hydration Model: A New Model for Understanding Newborn Hydration Immediately After Birth
Biological Research for Nursing 2015, Vol. 17(1) 94-99 ª The Author(s) 2014 Reprints and permission: sagepub.com/journalsPermissions.nav DOI: 10.1177/1099800414529362 brn.sagepub.com
Pamela J. Mulder, PhD, RN1, and Sue E. Gardner, PhD, RN, FAAN1
Abstract The normal small volume of breast milk produced in the first 2 days following birth may raise concerns about adequate hydration in breast-fed newborns. These concerns are further magnified when breast-fed infants lose ≥ 7% of their birth weight within 2 days postnatally. Weight loss following birth is presumably mostly water loss that could result in hypohydration and subsequent hypernatremic dehydration. However, excess fluid loss immediately following birth is a normal and necessary process. Furthermore, newborns exposed to excess fluid intake during labor may need to lose ≥ 7% of birth weight in the first 2 days following birth in order to achieve euhydration. Normal newborn fluid loss following birth confounds the use of weight loss as the sole measure of newborn hydration. We thus propose the healthy newborn hydration model that highlights the normalcy of newborn weight loss immediately following birth and the healthy newborn’s compensatory mechanisms for preserving adequate hydration. We also recommend the use of serum sodium to measure intravascular osmolarity in addition to monitoring weight loss to obtain a more comprehensive newborn hydration assessment. Research is necessary in healthy newborns to identify relationships among fluids received in utero, newborn weight loss, and hydration, as evaluated with laboratory measures, in the first 2 days following birth. This information will guide clinicians in correctly identifying newborns with inadequate hydration who are in need of supplementary fluids versus newborns with adequate hydration for whom exclusive breast-feeding can be supported and encouraged. Keywords newborn, hydration, weight loss, breast-feeding
Promoting breast-feeding and preventing dehydration in the newborn are important, but often considered competing, health objectives (Fawke, Whitehouse, & Kudumula, 2008). Exclusive breast-feeding for 6 months, a national health priority, is known to decrease infectious diseases and sudden infant death syndrome in infants, type 1 diabetes and leukemia in children, and obesity and type 2 diabetes in adulthood (Ip et al., 2007; U.S. Department of Health and Human Services, 2011, n.d.). Yet, only 13% of infants in the United States exclusively breast-feed for 6 months (Centers for Disease Control and Prevention, 2007). If 90% of infants in the United States were exclusively breast-fed, US$13 billion per year would be saved and over 900 deaths would be prevented (Bartick & Reinhold, 2010). Exclusive breast-feeding ends for more than half a million infants each year because they are supplemented with formula in the hospital following birth in spite of evidence showing that formula supplementation significantly increases the risk of breast-feeding cessation (Dabritz, Hinton, & Babb, 2010; Declercq, Labbok, Sakala, & O’Hara, 2009; Forde & Miller, 2010; Martin et al., 2012; Semenic, Loiselle, & Gottlieb, 2008; U.S. Department of Health and Human Services, 2007). Formula supplementation is a common practice when newborn weight loss is 7% because this threshold is accepted
as a strong indicator of a water deficit (hypohydration) due to inadequate breast milk intake in the newborn (Academy of Breastfeeding Medicine Protocol Committee, 2009; American Academy of Pediatrics, 2005; Shirreffs, 2003). Hypohydration is associated with acute renal failure, brain edema, seizures, and death (Unal, Arhan, Kara, Uncu, & Aliefendioglu, 2008). Therefore, clinicians tend to aggressively diagnose and treat hypohydration, leading to formula supplementation and the demise of breast-feeding for a substantial number of infants. A goal of Healthy People 2020 is to decrease formula supplementation in the ‘‘first 2 days of life’’ by 10% (U.S. Department of Health and Human Services, n.d.). This goal is consistent with the fact that most of the evidence linking excessive weight loss (EWL; i.e., 7%) with hypernatremic dehydration (serum sodium 150 mEq/L) was derived from newborns 3 days old (Koklu et al., 2007; Moritz, Manole, 1
College of Nursing, University of Iowa, Iowa City, IA, USA
Corresponding Author: Pamela J. Mulder, PhD, RN, College of Nursing, University of Iowa, Iowa City, IA 52242, USA. Email: [email protected]
Downloaded from brn.sagepub.com at FRESNO PACIFIC UNIV on December 25, 2014
Mulder and Gardner
95
Healthy Newborn Hydration Model Pregnancy
Labor
Birth
Maternal Fluids Oxytocin Fetal AVP Fetal fluid shift from intravascular to interstitial Output Fetal Hyperhydration Serum Na, ECF
0–24 Hours Colostrum Infant Formula Newborn AVP Newborn fluid shift from interstitial to intravascular Output
Newborn Hyperhydration Serum Na, ECF
24–60 Hours
Weight Loss
Newborn Euhydration Normal Serum Na, Normal ECF
Figure 1. Healthy newborn hydration model. A pictorial model describing the influences of maternal, fetal, and newborn variables on newborn hydration from pregnancy to 60 hr following birth. AVP ¼ arginine vasopressin; ECF ¼ extracellular fluid; Na ¼ sodium.
Bogen, & Ayus, 2005; Pelleboer et al., 2009; Unal et al., 2008; Wang et al., 2007). Unfortunately, the threshold of 7% has been extrapolated to infants in the first 2 days of life, leading to earlier formula supplementation. One possible approach to achieving the Healthy People goal is to reexamine the practice of relying solely on this weight loss threshold to drive formula supplementation in the first 2 days of life (Chantry, Nommsen-Rivers, Peerson, Cohen, & Dewey, 2011; Mulder, Johnson, & Baker, 2010; Noel-Weiss, Courant, & Woodend, 2008). The purpose of this article is to propose a new model for examining and evaluating hydration status in the healthy newborn in the first 24–60 hr following birth and to recommend using laboratory measures of hydration in addition to monitoring weight loss in this evaluation. We suggest that the use of weight loss in the first 24–60 hr following birth as a sign of hypohydration is confounded by the natural process of newborn diuresis, resulting in a large number of false-positive diagnoses of hypohydration. We also delineate further research necessary to examine the diagnostic validity of any weight loss threshold, and the utility of laboratory measures of hydration is also delineated.
Weight Loss Immediately Following Birth Weight loss in the first 2–3 days following birth is a normal, physiologic, and necessary event during the newborn’s transition to extrauterine life (Blackburn, 2007; Tender et al., 2009). Therefore, large weight losses at this time may be a normal physiologic reaction to receiving a large fluid load during labor and may not be associated with hypohydration, inadequate breast milk production, or illness (Chantry et al., 2011; Mulder et al., 2010; Okumus et al., 2011). The relationships among newborn hydration, breast milk intake, urine output, and weight loss in the first 24–60 hr following birth are not fully understood (Dollberg, Lahav, & Mimouni, 2001). Little is known about the physiology of the lactating breast, and the normal trajectory of breast milk production has not been established (Hartmann, 2007). Further, there is not adequate research to differentiate between a physiologic or pathologic weight loss in breast-fed newborns or to identify the morbidity or mortality associated with newborn weight loss (Noel-Weiss
et al., 2008; Oddie, Richmond, & Coulthard, 2001; Unal et al., 2008; Wright & Parkinson, 2004). Breast-fed newborns are expected to lose 4–7% of their birth weight, start gaining weight at 3 days, and return to birth weight at 7–10 days (Macdonald, Ross, Grant, & Young, 2003; Wright & Parkinson, 2004). At the age of 3 days, most breast-fed newborns reach their weight loss nadir and begin gaining weight, concurrent with mothers experiencing lactogenesis II, a dramatic increase in breast milk production (Wright & Parkinson, 2004). Delayed (>72 hr following birth) or absent lactogenesis II is associated with EWL and hypernatremic dehydration (Dewey, Nommsen-Rivers, Heinig, & Cohen, 2003). Before 3 days of age, however, breast-fed newborns consume minimal breast milk (Santoro, Martinez, Ricco, & Jorge, 2010). Dommelen, Wouwe, Breuning-Boers, Buuren, and Verkerk (2007) theorized that ‘‘it takes some time before insufficient breast feeding leads to weight loss’’ (p. 492). We suggest that even EWLs (7%) in the first 24–60 hr following birth could be physiologic and healthy when no other signs of illness are present because newborns are hyperhydrated at birth (Blackburn, 2007; Modi, 2003). The loss of fluid is necessary to restore euhydration and achieve cardiopulmonary adaptation to the extrauterine environment (Modi, 2003). This proposition is based on the following model.
A New Model In the healthy newborn hydration model (see Figure 1), the healthy, full-term mother and fetus are presumed hyperhydrated at admission to labor and delivery, per existing evidence about maternal and fetal hydration. Although maternal physiologic changes in pregnancy include both sodium and water retention, increases in fluid volume (6–8 L of water) outweigh sodium retention, so that levels of serum sodium and plasma osmolarity are decreased (Blackburn, 2007). Larsson, Palm, Hansson, and Axelsson (2008) reported a downward shift in the reference range for serum sodium prior to delivery (124.0–140.4 mmol/L), as compared to healthy, fertile, nonpregnant women (136.7–144.8 mmol/L). These changes contribute to dilutional hyperhydration. The fetus is also hyperhydrated because the
Downloaded from brn.sagepub.com at FRESNO PACIFIC UNIV on December 25, 2014
96
Biological Research for Nursing 17(1)
fetus remains in fluid and electrolyte balance with the mother (Blackburn, 2007). The onset of labor further favors fetal hyperhydration because the fetus vastly increases the production of arginine vasopressin (AVP; Blackburn, 2007; Leung et al., 1980; Tsukahara et al., 2002). AVP increases water retention by the fetal kidneys (Ranadive & Rosenthal, 2011) up to the fetus’ maximum urine-concentrating ability (Blackburn, 2007). During labor, fetal capillary permeability increases, prompting a shift of intravascular fluid to the interstitial compartment. Evidence supports the proposition that a significant proportion of newborns are mildly hyponatremic at birth due to dilutional fetal hyperhydration. Hyponatremia has been defined as a serum sodium level that is less than 133–135 mEq/L (Marcialis, Dessi, Pintus, Marinelli, & Fanos, 2012). Martinerie and colleagues (2009) reported a mean serum sodium concentration of 132.6 mmol/L among 48 healthy, vaginally delivered, fullterm newborns whose mothers did not receive any intravenous fluid before delivery. Describing differences between newborns with and without birth asphyxia, Basu, Som, Das, and Choudhuri (2010) reported that control infants had a mean serum sodium concentration of 138.8 mEq/L (standard deviation [SD] ¼ 2.7). Assuming serum sodium was normally distributed, these results indicate that almost half of the healthy infants had serum sodium values ranging from 130.7 to 138.8 (mean + 3 SD). Basu and colleagues did not describe whether mothers received intravenous fluid in labor or how much they might have received. Moen, Brudin, Rundgren, and Irestedt (2009) reported that 26% of mothers who received more than 2,500 ml of fluid in labor had hyponatremia (plasma sodium 130 mmol/L) immediately following birth, and their newborns were significantly more likely to have EWL. Numerous case studies have also described mothers in labor with excessive fluid intake (3–4 L/day) resulting in newborns with clinically significant hyponatremia (
