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PEDIATRICS Vol. 108 No. 1 July 2001, pp. 25-30
From * Rockefeller University Hospital, New York, New York; and
Objectives. Severe neonatal jaundice
is a common clinical manifestation of glucose-6-phosphate dehydrogenase
(G-6-PD) deficiency and the most difficult to manage; kernicterus is
not an uncommon outcome. We assessed in healthy, direct Coombs
test-negative Greek newborns of Methods. The studies were conducted at Metera Maternity
Hospital in Athens, Greece. Enrolled newborns had the plasma bilirubin
concentration (PBC) determined in cord blood and daily thereafter until
a declining level was obtained and the case was closed. Intervention
with phototherapy was dictated at exact, age-specific PBC levels. In our initial study, we enrolled consecutive mature healthy
G-6-PD-deficient newborns as well as a threefold excess of
G-6-PD-normal neonates born at approximately the same time (control
group). For the SnMP trial, G-6-PD-deficient neonates were administered
SnMP as a single intramuscular dose of 6 µmol/kg birth weight within
24 ± 12 hours of age.
Results. SnMP was administered at 26.7 ± 6.1 hours
of age to 172 G-6-PD-deficient newborns (group A); 168 G-6-PD-normal
(group B) and 58 G-6-PD-deficient (group C) newborns who were enrolled
earlier provided the comparison groups. Except for the expected excess of males in the G-6-PD-deficient groups (A and C), there were no
differences in the demographic characteristics among the 3 groups. The
incremental changes in PBC from cord blood to 24 hours of age also were
similar (group A: 4.13 ± 1.32 mg/dL; group B: 4.05 ± 1.34 mg/dL; group C: 4.39 ± 1.07 mg/dL), but there were significant
differences in the next period, 24 to 48 hours of age (group A:
0.63 ± 1.44 mg/dL; group B: 1.69 ± 1.5 mg/dL; group C:
2.45 ± 1.72 mg/dL). Peak PBC was significantly different (group A: 7.81 ± 3.04 mg/dL; group B: 8.68 ± 3.1 mg/dL; group C:
11.24 ± 3.76 mg/dL) as was the age at which peak PBC was recorded
(group A: 56 ± 29 hours of age; group B: 69 ± 26 hours of
age; group C: 83 ± 29 hours of age). These differences in favor
of group A were observed despite the fact that phototherapy was used in 15% of the newborns in group B and 31% of those in group C, whereas none of those treated with SnMP required phototherapy. Finally, in one
female, who was heterozygous for G-6-PD deficiency, in group C
phototherapy failed and 2 exchange transfusions were performed.
Conclusions. In comparison with normal neonates,
G-6-PD-deficient neonates experienced a twofold increase in the
prevalence of significant hyperbilirubinemia requiring phototherapy. A
single dose of SnMP administered in the 1st day of life to the
G-6-PD-deficient newborns shifted the peak PBC distribution to the left
(lower values) even in relation to normal neonates and entirely
eliminated the need for phototherapy. Interdiction of bilirubin
production by use of a heme oxygenase inhibitor such as SnMP represents
a simple and highly effective means for the preventive management of
jaundice in G-6-PD-deficient newborns.
Metera Maternity Hospital, Athens, Greece, and New England Medical
Center, Boston, Massachusetts.
ABSTRACT
Top
Abstract
Methods
Results
Discussion
References
38 weeks' gestational age 1) the
current burden of G-6-PD deficiency-associated severe jaundice, and 2)
the efficacy of preventive use of Sn-mesoporphyrin (SnMP), a potent
inhibitor of heme oxygenase activity and thus of bilirubin production,
in ameliorating jaundice in G-6-PD-deficient neonates.
In the past 40 years, severe neonatal jaundice and
kernicterus have emerged as the most important clinical manifestations of glucose-6-phosphate dehydrogenase (G-6-PD)
deficiency1-5 and have been responsible for significant
neonatal morbidity and mortality in populations of the Mediterranean
littoral, the Middle East, the Arabian peninsula, Southeast Asia, and
Africa.6 However, immigration and intermarriage allowed
the spread of G-6-PD deficiency mutants to geographic areas distant
from its place of origin and thus transformed severe neonatal jaundice
associated with G-6-PD deficiency into a global
problem.6-8 Typically, whereas in all other age groups of
G-6-PD-deficient individuals hemolytic anemia is triggered by exposure
to an exogenous agent, in neonates such an exposure is not necessary
and jaundice rather than anemia predominates in the clinical
presentation.6,8 During the past few decades, the
introduction of exchange transfusion (ET) and later of phototherapy
greatly improved the outcome in the various etiologic groups of severe
neonatal jaundice. However, the relative importance of G-6-PD
deficiency in the cause of kernicterus has increased in many
populations as a result of the unpredictable course of bilirubinemia in
G6PD deficiency.6,7,9,10 Thus, a new approach that could
simplify the clinical management of G-6-PD-deficient neonates would be
beneficial for infants, parents, and physicians alike.
In general, neonatal jaundice is the result of a transient imbalance
between the rates of bilirubin production and bilirubin elimination.
This imbalance can be modified favorably by inhibiting heme oxygenase
(HO), the rate-limiting enzyme in the production of bilirubin. The
development and clinical application of HO inhibitors such as
Sn-mesoporphyrin (SnMP) now provide the effective, clinical tools
required to achieve this goal.11-20 Inhibitors of HO have
been used by our group in a series of randomized, controlled, clinical
trials to interdict the development of significant bilirubinemia
(preventive use) in direct Coombs test-positive ABO
incompatibility16 and in preterm neonates17 and to control already existing hyperbilirubinemia (therapeutic use) in
term and near-term neonates with nonspecific
hyperbilirubinemia.18,19 The effectiveness of HO
inhibitors has been demonstrated by a markedly diminished or entirely
eliminated need for phototherapy and by a shortened length of required
clinical observation in treated newborns. Finally, in a randomized
trial, we compared the effectiveness of the preventive versus the
therapeutic use of SnMP in G-6-PD-deficient newborns.20
After the preventive use of SnMP proved the superior arm, enrollment
continued with the preventive administration of SnMP and this article
details the experience of the total group of G-6-PD-deficient newborns of Study Group and Design
The enrolled neonates were born at Metera Maternity Hospital in
Athens, Greece. The routine care at Metera included 2 important practices that facilitated our studies: 1) collection from all live
births of cord blood for the determination of blood groups, direct
Coombs test, and G-6-PD activity, and 2) a post partum hospital stay of
at least 4 days. The present article includes results from 2 separate
studies. The first study was undertaken to determine whether the
current burden in the Greek population of spontaneous severe neonatal
jaundice associated with G-6-PD deficiency was onerous enough to
justify a clinical trial with SnMP. This study was conducted in January
and May of 1994. It was approved by the Metera Institutional Review
Board, and informed parental consent was obtained. Enrolled were
healthy, direct Coombs test-negative neonates of 38 weeks' gestational age (GA) who received preventive SnMP.
METHODS
Top
Abstract
Methods
Results
Discussion
References
38 weeks' GA as
determined by the best obstetric criteria. The study group included
consecutively born G-6-PD-deficient neonates of either gender. For each
G-6-PD-deficient infant an approximately threefold excess of
G-6-PD-normal neonates born close to the time of birth of the
G-6-PD-deficient neonate were recruited as controls. Phototherapy was
conducted according to long-standing criteria in use at Metera (Fig
1, Line A). It was concluded from this
study that a trial of SnMP in G-6-PD-deficient newborns was fully
justified, and critical points of the subsequent protocol were based on
data from the first study.
View larger version (64K):
[in a new window]
Fig. 1.
Plasma bilirubin concentration chart with age-specific threshold levels
for management decisions. A, threshold for initiation of phototherapy
to neonates enrolled in the first study and for administration of SnMP
to neonates randomized to the therapeutic arm of the SnMP trial. B,
threshold for crossover to phototherapy for neonates randomized to
either preventive or therapeutic SnMP. C, threshold for crossover to
exchange transfusion after phototherapy failure.
The SnMP trial protocol was approved by the Institutional Review Boards
of Rockefeller University, Tufts-New England Medical Center Hospital,
and Metera. The use of SnMP as an investigational new drug in newborns
was approved by the US Food and Drug Administration (IND 29 462) and
the Greek National Drug Administration. A written parental consent was
obtained. Eligible for enrollment were healthy, direct Coombs
test-negative, G-6-PD-deficient neonates of 210 days GA, 1.5 kg
birth weight (BW), and 24 ± 12 hours of age. The design of the
SnMP trial (January 1996 to December 1997) included an initial
randomized, sequentially analyzed trial comparing preventive to
therapeutic use of SnMP (Phase I, N = 86), which has
been described previously.20 Once the superior arm of the
trial was demonstrated, the protocol dictated that enrollment to the
inferior arm close and the trial continue as a single arm "impact"
clinical trial. An additional 163 G-6-PD-deficient newborns were
enrolled. SnMP was administered as a single intramuscular injection at
a dose of 6 µmol/kg BW from single-dose vials prepared as previously described.17 A volume of 0.25 mL/kg BW was administered. The SnMP solution was stored in the dark at 4°C.
For both the first study and the SnMP trial, the plasma bilirubin concentration (PBC) was measured in the cord blood and in samples collected by heel stick (2 microhematocrit tubes) at the time of enrollment and daily thereafter up to the time that a declining PBC was established and the case was closed. With few exceptions, mothers breastfed their infants; however, a night formula feeding was given throughout hospitalization, and supplemental formula was used routinely in the first 2 to 3 days of life until adequate lactation was established. All neonates received 1 mg of vitamin K (Konakion; Roche Laboratories, Nutley, NJ) intramuscularly at birth.
Laboratory Methods
Total PBC was determined with the Automated Digital
UB Analyzer (Arrows Company, Osaka, Japan). Red cell G-6-PD activity
expressed as units/gram of hemoglobin was determined with the use of
the Sigma Diagnostics (St Louis, MO) reagent kit and procedure. In cord
blood, the critical level for diagnosing G-6-PD deficiency was 
6.0
U/g of hemoglobin and 8.0 U/g of hemoglobin in male and female
neonates, respectively.
Data Collection and Statistical Analysis
All pertinent family, maternal, and neonatal clinical and laboratory information was entered into a computerized database. In the statistical analyses for continuous variables, the unpaired two-tailed t test was used, and for categorical variables, the Fisher's exact test was used. For practical reasons and to avoid the effect of circadian variation in PBC, the "daily" blood samples were drawn in the morning. Thus, the exact age at sampling varied depending on the time of delivery. Age is an important determinant of PBC at least for the first 2 to 3 days during the phase of rapid bilirubin accumulation. To reduce the age-related variability, using the actual PBC levels and the respective exact age, we calculated the rate of PBC change per 24 hours from cord blood to first blood sample (enrollment) and from first to second blood sample.
Follow-Up
The participants in the SnMP trial had a comprehensive follow-up examination at 18 months of age. The examination included interim medical history, detailed medical and neurologic examination, and neurodevelopmental assessment with the use of the Bailey Scales of Infant Development.21 In addition, a 5-year surveillance by structured telephone interviews is in progress.
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RESULTS |
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Top
Abstract
Methods
Results
Discussion
References
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There were 10 508 (5464 males) live births during the period of
the SnMP trial; of those, 270 (179 males) were G-6-PD deficient (2.57%). Consent was refused for 12 (4.4%) of the neonates, and 9 neonates met the exclusion criteria.20 Thus, a total of
249 neonates were enrolled in the SnMP trial. None of these neonates
fulfilled the PBC criteria (Fig 1) for crossover to phototherapy or ET.
Overall, preventive SnMP was administered at 26.7 ± 6.1 hours of
age to 205 neonates, of whom 172 were of 38 weeks' GA. To illuminate
both the characteristics of bilirubinemia in G-6-PD-deficient neonates
and the quantitative and qualitative effects of preventive SnMP, we
used the data of the first study for comparisons. Furthermore, to
remove a GA bias, 33 G-6-PD-deficient neonates of <38 weeks' GA and
who received preventive SnMP were not included in the comparisons (none
required phototherapy). The composition and the derivation of the 3 groups
A, B, and Cused in the comparisons are described in Fig
2.
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In Table 1, the main demographic data are presented. As expected, there was a male preponderance among the G-6-PD-deficient neonates; otherwise, the 3 groups were identical. There were no significant differences among the groups in the rate of PBC increase at baseline cord blood to 24 hours of age. In the next period, 24 to 48 hours of age, however, the difference between the groups in the rate of PBC change was highly significant. A direct comparison of the two G-6-PD-deficient groups (0.63 and 2.45 mg/dL in groups A and C, respectively; P < .0001, a 74% difference) demonstrates the effect of SnMP in diminishing the rate of increase in PBC in the 24 hours after its administration. The 33% difference between the 2 groups of the first study (1.64 mg/dL and 2.45 mg/dL for groups B and C, respectively) highlights the pattern of severe bilirubinemia in G-6-PD-deficient neonates. A similar pattern was observed for peak PBC and age on reaching it in the group order A < B < C (Table 1).
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We computed the frequency distribution of peak PBC for the 3 groups
(Fig 3). In all 3 groups, a unimodal
distribution was found with a tail in the higher PBC levels region in
the 2 G-6-PD-deficient groups (groups A and C). The effect of SnMP
administered in the first day of life to all of the neonates in group A
was to shift the distribution of the peak PBC to the left (ie, to lower
values) in relation to groups B and C. This shift is even more
impressive when we consider that phototherapy was used in 15% and 31%
of the newborns of groups B and C, respectively (P = .0109), and thus the differences in peak PBC among the 3 groups were
dampened. Moreover, in group C, it was common for the intended threshold for initiation of phototherapy to be exceededmainly because
of the pattern of secondary accelerationand for the PBC to continue
to rise after the initiation of phototherapy (data not shown). This is
obvious from the extension of peak PBC values in the region 16 mg/dL
(Fig 3) in group C and the need for ET in one female heterozygous
G-6-PD-deficient neonate (PBC: 26.7 mg/dL at 55 hours of age after
intensive phototherapy, which began at 30 hours of age, when the PBC
was 11.7 mg/dL). It is worth noting that a G-6-PD-deficient male, 1 of
the 21 neonates not enrolled in the trial, also required ET (PBC: 29.5 mg/dL at 56 hours of age). In both cases, a meticulous search for
exposure to an exogenous agent was negative.
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As a result of the shift to the left of the frequency distribution of the peak PBC in group A, differences in important clinical characteristics of bilirubinemia emerged (Fig 4). The proportion of neonates whose peak PBC was <8.0 mg/dL was significantly higher in group A than in the other 2 groups. Thus, the preventive use of SnMP in G-6-PD-deficient neonates resulted in more than half (56%) having no degree of jaundice that warranted clinical attention. In the opposite direction, a significantly lower proportion of newborns in group A (11%) than in group B (17%) and in group C (40%) reached a peak PBC of >11.9 mg/dL, a level often used to define clinically significant hyperbilirubinemia (Fig 4). Finally, peak PBC was reached in <72 hours in 72%, 59%, and 41% in groups A, B, and C, respectively.
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We examined the individual PBC curves for evidence of an unusual pattern, such as a PBC curve with secondary acceleration (ie, when the initial phase of decelerating rate of PBC increase was followed by a second phase of accelerating PBC increase that exceeded by at least 1 mg/dL the level predicted from the rate in the previous 24 hours; "rebound" after terminating phototherapy was excluded). The incidence of such cases was significantly (P = .0005) higher (19%) in group C than in group B (3.6%) newborns. In those G-6-PD-deficient neonates who received preventive SnMP (group A), the incidence was reduced to 7.6% (P = .023 in comparison to group C).
There were no systemic or local reactions to the injection of SnMP, and all of the neonates had a benign postpartum course. Ninety percent of the enrolled neonates attended the 18-month follow-up. As was the case with our previous trials, there was no evidence of untoward effects in physical, neuromotor, and mental development; and in general health. A 5-year surveillance is in progress, after which a full report on the follow-up will be completed.
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DISCUSSION |
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Top
Abstract
Methods
Results
Discussion
References
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The initial epidemiologic study highlighted the qualitative and quantitative aspects of bilirubinemia in normal (group B) and G-6-PD-deficient (group C) Greek newborns. The peak PBC frequency distribution in group C showed a marked shift to the right in comparison to group B and a pronounced tail in the high values region (Fig 3) despite the extensive use of phototherapy (15% and 31% in groups B and C, respectively). In the initial period (cord to 24 hours), the rate of PBC increase was similar in both groups, but in the next period (24-48 hours), the rate in group C was twice as high as that in group B. The period of bilirubin accumulation lasted longer in group C, as indicated by the greater age at peak PBC (Table 1) and the higher proportion of neonates whose peak PBC was reached after 72 hours of age. A substantial proportion (19%) of neonates in group C exhibited a second phase of increasing bilirubin accumulation. The frequency and the intensity of this second phase highlight the unpredictability of the course of jaundice in G-6-PD-deficient neonates.
The administration of a single dose (6 µmol/kg BW) of SnMP at
26.7 ± 6.1 hours after birth suppressed completely the
development of hyperbilirubinemia requiring intervention with
phototherapy in G-6-PD-deficient neonates of 38 weeks' GA. The
frequency distribution of peak PBC was shifted to the left (lower
values) in treated infants (group A) even in relation to G-6-PD-normal
controls (group B; Fig 3), and the need for phototherapy was
eliminated. The incremental change of PBC in the period 24 to 48 hours
of age was decreased by 74% in relation to the untreated
G-6-PD-deficient neonates (group C); the peak PBC and the age on
reaching it were similarly reduced (group A < B < C), and a
secondary phase of accelerated bilirubin accumulation was reduced in
both prevalence and intensity, resulting in attenuation of the tail in
the region of high PBC values (Fig 3).
In populations with a high enough prevalence of G-6-PD deficiency and associated severe neonatal jaundice to justify cord blood testing, the preventive use of SnMP would offer the advantages of simplicity and high efficacy in interdicting the development of severe bilirubinemia. Our results raise the possibility that after the preventive use of SnMP, there may not even be a need to monitor the great majority of G-6-PD-deficient neonates for the occurrence of clinically significant bilirubinemia, and early postnatal discharge would be safe. A cautious approach to this issue is warranted, however, and a larger "impact" type of study is needed to demonstrate that additional interventions would not be necessary except in a rare case. In populations in which G-6-PD deficiency is uncommon, testing cord blood from all live births is not justified. Selective testing on the basis of parental ethnic background is an option,22 and in any case, testing for G-6-PD deficiency should be part of the work-up in unexplained severe neonatal jaundice. If G-6-PD deficiency is discovered in such a setting, SnMP can be administered immediately to interdict the further progression of hyperbilirubinemia.
With the present article, we conclude our studies of the efficacy of SnMP in moderating the course of bilirubinemia in all diagnostic groups of unconjugated neonatal jaundice. This HO inhibitor was used previously to moderate the development of severe jaundice in neonates with a predictable high incidence of potentially dangerous hyperbilirubinemia, as in ABO incompatibility,16 preterm delivery,17 and G-6-PD deficiency20 and was used therapeutically after the development of significant jaundice in near-term and term neonates with nonspecific hyperbilirubinemia18,19 and in G-6-PD-deficient newborns.20 In all of these groups, jaundice is a self-resolving condition, and current methods of management aim to gain time, while preserving neurologic integrity, until the problem subsides. We showed in the present study that preventive administration of a single dose of SnMP in G-6-PD-deficient newborns interdicts the development of severe hyperbilirubinemia, thus simplifying in an effective manner the clinical treatment of these high-risk newborns.
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ACKNOWLEDGMENTS |
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This research was supported by a contract (NO1-HD-5-3234) awarded to Dr Kappas, Rockefeller University Hospital, by the National Institute of Child Health and Human Development, and by gifts from the Renfield and Ablon Foundations.
We thank the medical and nursing staff of the Metera Maternity Hospital for their essential and generous help in carrying out the studies; Athena Koltsidopoulos, RN, for her valuable technical assistance and the coordination of the follow-up examinations, C. I. Henschke, MD, PhD, (Cornell University Medical College, New York, NY) for her advice on statistical analysis; Yong Joong Kim for data management; and Lisa Meyer, Rockefeller University, for secretarial assistance.
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FOOTNOTES |
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Received for publication Sep 19, 2000; accepted Nov 9, 2000.
Reprint requests to (A.K.) Rockefeller University Hospital, 1230 York Ave, New York, NY 10021-6399.
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ABBREVIATIONS |
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G-6-PD, glucose-6-phosphate dehydrogenase; ET, exchange transfusion; HO, heme oxygenase; SnMP, Sn-mesoporphyrin; GA, gestational age; BW, birth weight; PBC, plasma bilirubin concentration.
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REFERENCES |
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Results
Discussion
References
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This article has been cited by other articles:
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  N. G. Abraham and A. Kappas Pharmacological and Clinical Aspects of Heme Oxygenase Pharmacol. Rev., March 1, 2008; 60(1): 79 - 127. [Abstract] [Full Text] [PDF]
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; N = 172): preventive SnMP in G-6-PD-deficient neonates; group B (
;
N = 168): therapeutic phototherapy in G-6-PD-normal
neonates; group C (
; N = 58): therapeutic
phototherapy in G-6-PD-deficient neonates.
