Effect of hematocrit on exhaled carbon monoxide in healthy newborn infants

OBJECTIVE

We tested the hypothesis that, the red blood cell (RBC) mass, estimated by hematocrit (HCT) or hemoglobin (Hb) level, influences the carbon monoxide (CO) production rate.

STUDY DESIGN

The relationship between end tidal CO corrected for ambient carbon monoxide level (ETCOc) and the RBC mass have been studied in 58 full-term infants at the mean age 4.9 hours.

RESULTS

Mean ETCOc was 1.88 ppm (1.3 to 3.4 ppm). ETCOc correlated significantly with HCT (R 2=10.1%, p=0.015) and with Hb (R 2=11%, p=0.011). Infants with a capillary HCT >65% had significantly higher ETCOc (mean 1.99+/-0.49 ppm) than infants with a capillary HCT <65% (1.74+/-0.39 ppm), p=0.035. When CO production was corrected for HCT (ETCOc/HCT), this difference did not longer exist.

CONCLUSIONS

In newborn infants ETCOc significantly correlates with RBC mass. Comparing different infant's CO generation rate one should take into consideration their initial RBC level. In order to adjust for the existing differences in RBC, we suggest the use of the ETCOc/HCT index.

Negative results and impact factor: a lesson from neonatology

OBJECTIVE

To test the hypothesis that articles with negative results are more likely than articles with positive results to be published in journals with lower impact factor.

DESIGN AND SETTING

We selected all of the randomized, placebo-controlled trials conducted during the neonatal period between October 1, 1998, and October 1, 2003. Trials were classified as having positive results or negative results (significant or no significant difference, respectively). Only studies dealing with primary outcomes (efficacy) were included.

MAIN OUTCOME MEASURES

The impact factor of each journal was determined, and the sample size for each study was noted.

RESULTS

There were 233 articles that fulfilled the inclusion criteria. There was a significant difference between the 2 groups in terms of impact factor (P = .03) but not sample size (P = .30). Impact factor correlated with both sample size and the type of study results (positive results vs negative results; P<.05).

CONCLUSION

Articles with negative results are more likely than articles with positive results to be published in journals with lower impact factor.

Posttransfusion equilibration of hematocrit in hemodynamically stable neonates

OBJECTIVE

To determine whether hematocrit obtained 15 mins after blood transfusion in hemodynamically stable neonates is significantly different from that obtained after 6 hrs. We hypothesized that the hematocrit stabilizes within the first 15 mins that follow a 3-hr blood transfusion in preterm infants.

DESIGN

We prospectively studied 24 consecutive infants who received blood transfusion. Hematocrit was measured immediately before the transfusion and 15 mins and 6 hrs after the transfusion of 10 mL/kg body weight of sedimented red blood cells administered over 3 hrs. Hematocrit was measured by centrifugation of a capillary.

RESULTS

There was a significant increase in hematocrit from pretransfusion values both at 15 mins and 6 hrs. The increase in hematocrit from the pretransfusion value was identical (11%) at both 15 mins and 6 hrs.

CONCLUSION

The hematocrit obtained 15 mins after the end of a 3-hr blood transfusion in hemodynamically stable, anemic infants is indistinguishable from that obtained after 6 hrs in the same infants. Thus, if the increase of hematocrit is deemed insufficient at 15 mins after the transfusion, it is possible to complete the transfusion without exposing the patient to an additional donor.

The effect of prolonged rupture of membranes on circulating neonatal nucleated red blood cells

OBJECTIVES

To test the hypothesis that absolute nucleated red blood cells (ANRBC) counts are higher at birth in infants who were born after prolonged rupture of membranes (PROM, >24 hours).

STUDY DESIGN

Retrospective study of 31 infants admitted to the neonatal intensive care unit who were born after PROM, and pair matched for gestational age and Apgar scores with 31 no PROM controls. Venous ANRBC counts were obtained within 1 hour of life.

RESULTS

Groups did not differ in birthweight, gestational age, Apgar scores, and platelets counts. The ANRBC counts and hematocrit were significantly higher in infants who were born after PROM than in controls.

CONCLUSIONS

Infants born after PROM have higher ANRBC counts at birth than control infants. We suggest that increased fetal erythropoiesis exists in infants who are delivered after PROM. If correct, our interpretation supports the theory that fetal hypoxia and/or ischemia may result from PROM.

Nucleated red blood cells in preterm infants with retinopathy of prematurity

OBJECTIVE

The aim of this retrospective study was to examine hematologic indices of potential intrauterine hypoxia, including circulating nucleated red blood cells, lymphocytes, and platelets in preterm infants who developed retinopathy of prematurity (ROP) compared with suitable controls. We hypothesized that higher neonatal absolute nucleated red blood cell (ANRBC) and lymphocyte counts and lower platelets would be found in infants who developed ROP, compared with control infants.

METHODS

Each of 23 infants with ROP was pair matched for gestational age and Apgar scores with a control without ROP. Criteria for exclusion in both groups included factors that may influence the ANRBCs at birth. Venous ANRBC counts were obtained within 1 hour of life. Statistical analyses used paired t tests, a paired Wilcoxon test, and backward stepwise-regression analysis.

RESULTS

Groups did not differ in birth weight, gestational age, Apgar scores, or hematocrit, white blood cell, or platelets counts. The ANRBC counts at birth were significantly higher in infants who developed ROP than in controls.

CONCLUSIONS

Infants who develop ROP have higher ANRBC counts at birth than matched controls. We suggest that increased fetal erythropoiesis exists in preterm infants who later on will develop ROP. If correct, our interpretation supports the theory that long-lasting fetal hypoxia and/or ischemia may play a role in the pathogenesis of ROP.

Fat and energy contents of expressed human breast milk in prolonged lactation

OBJECTIVE

To estimate fat and energy contents of human milk during prolonged lactation.

METHODS

Thirty-four mothers, of term, healthy, growing children, who had been lactating for >1 year (12-39 months) were recruited. Control subjects were 27 mothers, of term infants, who had been lactating for 2 to 6 months. Fat contents of the milk samples were estimated as creamatocrit (CMT) levels. Energy contents of the milk were measured with a bomb calorimeter.

RESULTS

The groups did not differ in terms of maternal height and diet, infant birth weight, gestational age, or breastfeeding frequency. They differed significantly in terms of maternal age, maternal weight, and BMI. The mean CMT levels were 7.36 +/- 2.65% in the short-duration group and 10.65 +/- 5.07% in the long-lactation group. The mean energy contents were 3103.7 +/- 863.2 kJ/L in the short-duration group and 3683.2 +/- 1032.2 kJ/L in the long-duration group. The mean CMT levels and mean energy contents were correlated significantly with the duration of lactation (R2 = 0.22 and R2 = 0.23, respectively). In multivariate regression analysis, CMT levels (or energy contents) were not influenced by maternal age, diet, BMI, or number of daily feedings but remained significantly influenced by the duration of lactation.

CONCLUSIONS

Human milk expressed by mothers who have been lactating for >1 year has significantly increased fat and energy contents, compared with milk expressed by women who have been lactating for shorter periods. During prolonged lactation, the fat energy contribution of breast milk to the infant diet might be significant.

Bone ultrasound velocity of infants born small for gestational age

BACKGROUND

Quantitative ultrasound is increasingly used to assess bone status. Bone speed of sound (SOS), a biophysical property of bone, has been used to predict bone breakability. While decreased bone mineral content and delayed epiphyseal growth have been reported in small for gestational age (SGA) infants, there are no data on bone SOS in this group of infants.

OBJECTIVE

To test the hypothesis that SGA infants have lower bone SOS than appropriate for gestational age (AGA) infants.

METHODS

Bone SOS was measured within the first 96 hours of life at the right tibial midshaft in 22 singleton SGA infants. We compared these data with data obtained in 73 AGA controls. We used the Omnisense instrument which measures axially transmitted SOS. Infants ranged in gestational age (GA) from 25 to 42 weeks and in birth weight (BW) from 500 to 2,585 g. Statistical analyses included paired t-tests between the actual value obtained in every child and the theoretical, computed average normal value for GA, BW, or knee-sole length (KSL) based on our curves for AGA singletons. A p value < 0.05 was considered significant.

RESULTS

Bone SOS measured in SGA infants was higher than the predicted computed average SOS of AGA singletons with significant differences in all of the parameters studied.

CONCLUSIONS

Contrary to our hypothesis, SGA infants have higher bone SOS than AGA controls. Since bone mineral density is reported to be low in these infants, we speculate that intrauterine growth restriction may affect bone mineral density and bone protein matrix in opposite directions.

Bupivacaine versus lidocaine analgesia for neonatal circumcision

Background

Analgesia for neonatal circumcision was recently advocated for every male infant, and its use is considered essential by the American Academy of Pediatrics. We compared the post-operative analgesic quality of bupivacaine to that of lidocaine for achieving dorsal penile nerve block (DPNB) when performing neonatal circumcision.

Methods

Data were obtained from 38 neonates following neonatal circumcision. The infants had received DPNB analgesia with either lidocaine or bupivacaine. The outcome variable was the administration by the parents of acetaminophen during the ensuing 24 hours.

Results

Seventeen infants received lidocaine and 19 received bupivacaine DPNB. Ten infants in the lidocaine group (59%) were given acetaminophen following circumcision compared to only 3 (16%) in the bupivacaine group (P < 0.01). Regression analysis showed that the only significant variable associated with the need for acetaminophen was the use of lidocaine (R² = 20.6; P = 0.006).

Conclusion

DPNB with bupivacaine for neonatal circumcision apparently confers better analgesia than lidocaine as judged by the requirement of acetaminophen over the ensuing 24-hour period.

Birth weight standards in the live-born population in Israel

BACKGROUND

Lacking curves of "intrauterine" growth, most birthing centers in Israel use United States or Canadian based curves as standards.

OBJECTIVE

To establish population-based standards of birth weight of live-born infants in Israel.

METHODS

Data on birth weight and gestational age were obtained from the registries of the Israel Ministry of Health and Ministry of the Interior, During the 9 year study period there were 1,074,122 infants delivered in Israel; 787,710 (73%) were included in this analysis.

RESULTS

In this study we provide data of birth weight by gestational age of live infants born in Israel between 1993 and 2001. Ranges of birth weight by gestational age are also depicted for singleton and multiple pregnancies. Fetuses in multiple pregnancies grow in a similar manner to singletons until 30 weeks of gestation, after which their growth slows down.

CONCLUSIONS

Use of these data as a standard for "intrauterine" growth better represents the Israeli neonatal population than the North American standards. In addition, curves of multiple pregnancies are significantly different from those of singleton pregnancies and might be more appropriate in these pregnancies.

Patent ductus arteriosus, indomethacin and necrotizing enterocolitis in very low birth weight infants: a population-based study

BACKGROUND

Patent ductus arteriosus is a risk factor for the development of necrotizing enterocolitis. The use of indomethacin to treat patent ductus arteriosus in preterm infants may either decrease the incidence of necrotizing enterocolitis by stabilizing or closing the ductus arteriosus or increase its incidence by a direct constricting effect on mesenteric blood vessels. The authors sought to evaluate the interrelationship between patent ductus arteriosus, treatment with indomethacin and the risk of necrotizing enterocolitis in very low birth weight infants.

METHOD

The Israel National database includes prospectively collected data on 99% of all very low birth weight infants in Israel. The study population comprised 6146 infants of 24-34 weeks' gestation born between 1995 and 2000. The effect of patent ductus arteriosus on necrotizing enterocolitis was assessed using multiple regression analysis.

RESULTS

Necrotizing enterocolitis occurred in 5.5% (n = 343) of all infants, in 9.4% of infants with patent ductus arteriosus and in 8.9% of infants who received indomethacin. The occurrence of necrotizing enterocolitis was independently associated with the presence of patent ductus arteriosus among infants not treated with indomethacin (odds ratio, 1.85) and those who received indomethacin therapy (odds ratio, 1.53). Indomethacin therapy in absence of patent ductus arteriosus was not associated with an increased risk of necrotizing enterocolitis (odds ratio, 0.72).

CONCLUSIONS

Patent ductus arteriosus is an independent risk factor for the development of necrotizing enterocolitis in very low birth weight infants. Therapy with indomethacin did not have a significant effect on the risk for necrotizing enterocolitis.

The effect of positioning on energy expenditure in preterm infants: a feasibility study

The aim of this study was to determine the feasibility of a study of the effect of positioning on energy expenditure in preterm infants. We performed a prospective, randomized, clinical cross-over pilot study of eight healthy, appropriate weight for gestational age, gavage-fed, clinically stable preterm infants at the postmenstrual age of 30 weeks. Prior to the study and in accord with our feeding protocol, infants uniformly received either their own mother's milk or a preterm formula. Each infant was studied in four different positions after randomization to eight different sequences. Infants were studied asleep, 90 minutes after feeding, after 20 minutes of being nursed in a given position. They were cared for in a servo-controlled convective incubator during the metabolic measurements, which were performed by indirect calorimetry. Energy expenditure was not significantly affected by the body position in which the infant was studied. The difference between the highest and the lowest mean energy expenditure was 3.7% of the highest one. We conclude that attempts to minimize energy expenditure by modifying infant positioning are likely to be insignificant, from a practical standpoint, because of the nonsignificant or minimal differences in energy expenditure.

Nucleated red blood cells in concordant, appropriate-for-gestational age twins

OBJECTIVES

The purpose of this study was to test the hypothesis that neonatal nucleated red blood cell (RBC) counts are elevated in nondiscordant twins compared with singletons.

STUDY DESIGN

We compared absolute nucleated RBC counts taken after birth in 2 groups of term, appropriate-for-gestational age infants; 74 concordant twins, and 29 singleton control infants. We excluded infants with factors associated with a potential increase in absolute nucleated RBC counts.

RESULTS

Birth weight and gestational age were significantly lower in twins than in singletons (P < .01). Hematocrit, absolute nucleated RBC count, and corrected lymphocyte counts were significantly higher in twins (P < .01). In multiple regression, the significantly higher absolute nucleated RBC count in twins remained significantly higher even after taking into account gestational age and Apgar scores.

CONCLUSION

Concordant, appropriate-for-gestational age twins have increased nucleated RBCs at birth compared with singleton control infants.

Neonatal nucleated red blood cells in discordant twins

The objective of this study was to test the hypothesis that in discordant twins, the smaller infant has higher absolute nucleated red blood cell (RBC) count than the larger sibling. We compared absolute nucleated RBC counts, hematocrits, absolute leukocyte counts, absolute granulocyte counts, absolute lymphocyte counts, RBC counts and platelet counts obtained in the first 12 hours of life in 30 discordant twin sets. The smaller infant had a higher absolute nucleated red blood cell count and lower platelet counts than its larger sibling. Platelet counts correlated inversely with absolute nucleated RBC counts ( R(2) = 24.5%; p < 0.001) and absolute nucleated RBCs correlated directly with percent intertwin weight differences ( R(2) = 17.8%; p = 0.02). In discordant twins, the smaller infant has higher absolute nucleated RBC count and lower platelet counts than the larger sibling. We speculate that the hematologic alterations in the smaller fetus are linked to relative fetal hypoxia.

Indomethacin-induced early patent ductus arteriosus closure cannot be predicted by a decrease in pulse pressure

Wide pulse pressure is considered to be a sign of patent ductus arteriosus (PDA). We tested the hypothesis that, following indomethacin therapy, PDA closure is associated with a significant decrease in pulse pressure. Thirty-two ventilated preterm infants were echocardiographically diagnosed within the first 24 hours of life with PDA. Systolic, diastolic, and mean arterial blood pressures were measured prior to indomethacin treatment and after echocardiographically confirmed PDA closure. Following PDA closure, systolic and diastolic blood pressures and mean arterial pressure increased significantly without a significant change of pulse pressure (17 +/- 7 to 20 +/- 12 torr). We conclude that in preterm infants with PDA, systolic, diastolic, and mean arterial blood pressures increase significantly within first few days of life. Pulse pressure does not appear to be affected by early PDA closure. We speculate that high pulmonary resistance in the first days of life prevents significant diastolic aortic runoff and leaves pulse pressure unaffected by PDA, as well as by its closure.

Bone ultrasound velocity of appropriately grown for gestational age concordant twins

In neonates, quantitative ultrasound has been shown to be predictive of bone breakability and an index of biophysical property of bone. There are no data on bone speed of sound (SOS) in appropriate for gestational age (AGA) twins. The purpose of this study was to test the hypothesis that AGA twins who had normal intrauterine growth have bone SOS similar to that of AGA singletons. We measured tibial midshaft bone SOS within the first 96 hours of life in 25 pairs of AGA twins, 27 to 40 weeks gestation, and compared them with our data of 73 singletons. There were no significant differences in bone SOS between twin and singleton infants in any of the parameters studied. We found no significant difference in bone SOS between twins of the same pair. AGA twins have bone SOS very similar to that of AGA singletons. We suggest that intrauterine weight sparing occurs also in terms of biophysical properties of bone.

Energy expenditure in infants weaned from a convective incubator

Small preterm infants usually require a heated environment to survive. After weaning, some infants become hypothermic, and eventually require external thermal support for an additional period. We hypothesized that preterm infants respond to weaning from an incubator by increasing their resting metabolic rate. Thermally stable infants were studied when they had reached a weight of at least 1600 g. Resting energy expenditure was measured 2 hours before weaning and at 6, 23, 30, and 53 hours after weaning. Two-way analysis of variance for repeated measures was used for analysis. Sixteen infants with mean birthweight of 1270 +/- 375 g and gestational age 31 +/- 2.3 weeks were studied. After weaning, there was a significant increase in energy expenditure from 95.0 +/- 21.9 kcal/d in the incubator, to a 30-hours peak of 111.9 +/- 10.5 kcal/d after weaning. Weaning from a convective incubator results in an increase in metabolic rate in very low birth weight infants. We speculate that the infants' ability to increase metabolic rate might influence weaning success.

Effect of bicarbonate on neonatal serum ionized magnesium in vitro

Sodium bicarbonate is used to treat metabolic acidosis, or to induce metabolic alkalosis in sick neonates. The aim of this study was to quantify the decrease in serum concentration of ionized magnesium ([Mg2+]) when sodium bicarbonate is added to neonatal serum in vitro. Sodium bicarbonate was added to 30 cord serum samples of term infants to reach incremental concentrations of 0 to 2.0 mEq/L and [Mg2+] was measured. Serum [Mg2+] decreased significantly with the addition of sodium bicarbonate. At incremental sodium bicarbonate concentrations of 1.0 to 2.0 mEq/L, which is within the range of the desired aim in the treatment of metabolic acidosis, the magnitude of the decrease in serum [Mg2+] was approximately 0.084 to 0.158 mmol/L (18% to 34%) from the average baseline value. The addition of sodium bicarbonate causes a significant decrease in [Mg2+]. From this in vitro study we speculate that fast infusion of sodium bicarbonate in human neonates may potentially cause a clinically significant decrease in serum [Mg2+].

Nucleated red blood cells in preterm infants who have necrotizing enterocolitis

Absolute nucleated red blood cell counts for 23 preterm newborn infants who subsequently had development of necrotizing enterocolitis were significantly higher than for 23 control infants. These infants may have been exposed to relative intrauterine hypoxemia, a possible risk factor for the development of necrotizing enterocolitis.

Gastric residual in growing preterm infants: effect of body position

Studies of the effect of body position during and after bolus feeding upon gastric emptying or gastric residual have not had consistent results. We tested the hypotheses that right lateral decubitus leads to less gastric residual than left lateral decubitus and that the prone position leads to less gastric residual than the supine position. A prospective randomized clinical trial with triple crossover of healthy growing, appropriate for gestational age preterm infants. Each infant was successively studied while fed in the four different positions. Gastric residuals were measured at 1 and 3 hours after initiation of feeding and returned. Thirty-one patients were studied. At 1 hour, right lateral decubitus led to less significant residuals than the left lateral decubitus and the prone position led to less residual than the left lateral decubitus. The amount of gastric residuals 1 hour after a meal appears to be in the following decreasing order: left, supine, prone, right.

Nosocomial cutaneous abscesses in septic infants

OBJECTIVE

To retrospectively study the epidemiology of nosocomial cutaneous abscesses in 46 consecutive septic infants.

RESULTS

Ten infants had one abscess or more. Surviving infants with abscesses had a longer duration of bacteraemia, which disappeared within 24 hours of drainage.

CONCLUSION

Infants with persistent bacteraemia should be examined regularly for the presence of abscesses.

Increased serum potassium and intraventricular hemorrhage revisited

BACKGROUND

Increased serum potassium and intraventricular hemorrhage occur frequently in preterm infants.

OBJECTIVE

To retrospectively analyze data obtained on infants with severe IVH in relation to blood K+ concentrations.

METHODS

We identified all patients with severe IVH bom between July 1997 and July 2000. Each patient was pair-matched with a control infant of the same gestational age (+/- 1 week) without IVH in terms of head ultrasound findings on day 5 and whole blood K+ on days 3-5.

RESULTS

There were 24 infants in each group. The IVH group had significantly lower 1 minute Apgar scores and pH and higher blood K+ than the control group. Blood pH and K+ were inversely correlated. Stepwise regression analysis, taking into account blood pH and 1 minute Apgar score, showed a correlation only between blood K+ and IVH status.

CONCLUSIONS

Severe IVH is significantly associated with higher blood K+ concentrations. A causal relationship cannot be ascertained at this point.

[Prevention and pain management in term and preterm infants]

Pain in the neonatal period is frequently experienced by 6-10% of newly born infants, preterm and term, who require neonatal intensive care. Repetitive painful procedures without adequate analgesia provided by the medical staff may bear long-term or even life-long adverse consequences. The use of pharmacological and non-pharmacological modalities in the management of pain may change this undesirable situation. The use of opioid analgesia for very painful procedures and the use of non-opioid medications in combination with opioids are essential. A change in the sensory environment of the sick infant is an important additional analgesic effect. In addition to pain management in the neonatal intensive care units, neonatal circumcision is the most frequent surgical procedure performed in males, and is frequently conducted without appropriate analgesia. The simple available methods of analgesia for neonatal circumcision are discussed and should be employed in order to avoid painful circumcision. Many pediatric medical associations in the developed world consider failure to provide proper routine analgesia for neonatal circumcision to be an unethical and sub-optimal medical practice.

Decreased bone ultrasound velocity in large-for-gestational-age infants

BACKGROUND

Bone speed of sound is a measure of bone breakability. There are few reports on bone mineral content in large for gestational age infants; most of them in infants of diabetic mothers. There are no data on bone speed of sound in large for gestational age infants of nondiabetic mothers.

OBJECTIVE

To test the hypothesis that large for gestational age infants of nondiabetic mothers have lower bone speed of sound than appropriate for gestational age infants.

DESIGN/METHODS

Bone speed of sound was measured within the first 96 hours of life at the right tibial midshaft in 25 singleton large for gestational age infants of non diabetic mothers and compared to appropriate for gestational age controls.

RESULTS

Bone speed of sound measured in large for gestational age infants of nondiabetic mothers was lower than in controls.

CONCLUSIONS

Large for gestational age infants of nondiabetic mothers have lower bone speed of sound than controls.