Myocardial, erythropoietic, and metabolic adaptations to anemia of prematurity

Regional tissue oxygenation and conventional indicators of red blood cell transfusion in anaemic preterm infants

BACKGROUND

It is unresolved whether low haemoglobin (Hb) and symptoms of anaemia reflect oxygen delivery-consumption imbalances (fractional tissue oxygen extraction [FTOE]). Here, we test whether pre-transfusion Hb and symptoms of anaemia correlate with pre-transfusion cerebral and splanchnic FTOE.

METHODS

This prospective cohort study was carried out between Sept 1, 2014 and Nov 30, 2016 at Nepean Hospital, Sydney, Australia. The study enroled haemodynamically stable preterm infants: gestation <32 weeks; birth weight <1500 gs; postmenstrual age <37weeks, who received 15 mL/kg packed red blood cell transfusion (PRBCT) based on low Hb and symptoms of anaemia. FTOE was determined using simultaneous monitoring of near-infrared spectroscopy and pulse oximetry for 4 h before PRBCT.

FINDINGS

The study enroled 29 infants born with a median gestation of 26.4 weeks (IQR 25.4-28.1), birth weight 922 g (655-1064), at postmenstrual age 33.6 weeks (31.7-34.9), and weight 1487 g (1110-1785). There was no significant correlation between Hb (median 97 g/L, IQR 87-100) and cerebral FTOE (r=-0.12, 95% CI -0.47 to 0.27; p = 0.54, n = 29) as well as splanchnic FTOE (r=-0.09, 95% CI -0.45 to 0.29; p = 0.64, n = 29). Median cerebral FTOE (p = 0.67) and splanchnic FTOE (p = 0.53) did not differ between symptomatic and asymptomatic groups.

INTERPRETATION

Our preliminary findings suggest that pre-transfusion Hb and symptoms of anaemia might not accurately reflect oxygen delivery-consumption imbalances in both the brain and the gut. A lack of correlation with cerebral FTOE might be presumed to be due to the brain-sparing effect. However, the lack of correlation with splanchnic FTOE is more concerning. Hence, these results warrant larger studies incorporating FTOE along with the conventional criteria in the transfusion algorithm.

FUNDING

The study was funded (for the purchase of NIRS sensors) by the Australian Women and Children's Research Foundation.

Assessment of fetal right ventricular myocardial performance index changes following intrauterine transfusion

INTRODUCTION

Severe fetal anemia may cause cardiac ischemia, reduced contractility, and dysfunction. The purpose of our study is to evaluate right ventricular myocardial performance index (MPI) before and after intrauterine transfusion (IUT) in patients who underwent this procedure because of fetal anemia due to Rh-D alloimmunization.

MATERIALS AND METHODS

This prospective cohort study was conducted between January 2018 and June 2019 at Kanuni Sultan Suleyman Research and Training Hospital, Istanbul, Turkey. The pregnant women who were applied IUT because of fetal anemia due to Rh-D alloimmunization in our perinatology clinic were included in the study. Fetal right ventricular MPI before and 24 h after IUT were evaluated.

RESULTS

A total of 28 IUTs were performed in 17 pregnant women during the study period. The isovolumetric contraction time (ICT) and isovolumetric relaxation time (IRT) values measured before IUT, were found to be significantly longer compared to the ICT and IRT values measured after IUT. The MPI values measured after transfusion was found to be higher than before transfusion.

CONCLUSIONS

The fetal right ventricular MPI increases 24 h after IUT. This increase in the right ventricular MPI might be used as a marker for predicting adverse fetal outcomes following IUT.

Effects of red cell transfusion on cardiac output and perfusion index in preterm infants

OBJECTIVE/AIM

The present investigation was designed to study the effect of blood transfusion on cardiac output and perfusion index. The aim was to demonstrate a relationship between hematocrit, lactate, cardiac output and perfusion index in anemic preterm infants and to investigate significant changes in these parameters induced by RBC transfusion.

METHODS

Anemic infants who were under 35 weeks of gestational age (GA) and were in a stable clinical condition without respiratory or cardiac problems, signs of sepsis, or renal disease at the time of investigation were enrolled in the study. Enrolled infants received 15 ml/kg pure red blood cells over 4 h. Hematocrit and lactate levels were studied before and after transfusion. Cardiac output was measured by an ultrasound device (USCOM 1A) and perfusion index was monitored by pulse oximeter (MasimoRad7).

RESULTS

Cardiac output decreased by 9% (p < 0.05), due to decrease in heart rate by 10% (p < 0.05) and stroke volume significantly by 5% (p < 0.05) both in left and right sided cardiac measurements. Perfusion index significantly increased and lactate levels significantly decreased after transfusion (p < 0.05). Htc was inversely correlated with lactate levels, HR, CI and CO (r = -0.33, p = 0.01; r = -0.53, p = 0; r = -0.37, p = 0.004, r = -0.28, p = 0.03). PI was not significantly correlated with Htc levels before and after transfusion (r = 0.07, p = 0.7 and r = 0.007, p =0.97).

CONCLUSION

Our data support that heart rate, CO and CI and lactate levels increased as a response to anemia in preterm infants and RBC transfusion improved perfusion index suggesting better tissue oxygenation.

Necrotizing enterocolitis and the role of anemia of prematurity

Necrotizing enterocolitis (NEC) is one of the most common surgical diseases of preterm infants, with significant short- and long-term morbidity and mortality. Although the etiology of NEC remains elusive, multiple factors adversely affecting the intestinal mucosal integrity of preterm infants are known to be associated with NEC. Anemia and red blood cell (RBC) transfusion-related gut injury have been shown to have strong correlation with NEC. Anemia potentially compromises mucosal integrity with subsequent poor healing, and this injury may be augmented by yet unknown factors associated with RBC transfusions. Although convincing evidence is lacking, there is a need for guidelines to keep the hematocrit within clinically and physiologically relevant limits by appropriate interventions. Further investigations need to focus on assessing the interplay between anemia, chronically hypoxemic/hypoperfused intestines, and early iron therapy or other pharmacologic approaches for prevention/treatment of anemia and RBC transfusions.

Functional echocardiographic assessment of myocardial performance in anemic premature infants: a pilot study

This prospective observational study conducted in a neonatal intensive care unit aimed to evaluate echocardiographic changes provoked by anemia and transfusion of packed red blood cells (pRBCs) in premature infants. In this study, 32 anemic premature infants had serial echocardiographic assessment of left ventricular (LV) systolic performance, LV preload, and afterload immediately before, within 48 h, and up to 120 h after the transfusion of pRBCs. Pretransfusional evaluations also were compared with similar assessments of 71 nonanemic inpatient premature infants analogous for sex, gestational age at birth, and postnatal age. Left ventricular systolic performance was estimated from fractional shortening, LV output, and LV myocardial performance index (LVMPI). The LV preload was estimated from the LV end-diastolic dimension and the ratio of left atrium-to-aortic root dimension (LA/Ao ratio). The LV afterload was estimated from end-systolic wall stress. The LVMPI was found to decrease with increasing corrected gestational age in both the nonanemic (R = 0.173; p = 0.03) and anemic (R = 0.460; p = 0.007) infants. The LVMPI was the only index that changed after transfusion of pRBCs, decreasing in the younger anemic infants (p = 0.011) and increasing in the older anemic infants (p = 0.012). Finally, a significant inverse relationship between pre- and posttransfusional LVMPI values (R = 0.730; p < 0.001) was noted. The LVMPI may allow for identification of preterm infants more likely to be helped by transfusion of pRBCs.

Low versus high haemoglobin concentration threshold for blood transfusion for preventing morbidity and mortality in very low birth weight infants

BACKGROUND

Infants of very low birth weight often receive multiple transfusions of red blood cells, usually in response to predetermined haemoglobin or haematocrit thresholds. In the absence of better indices, haemoglobin levels are imperfect but necessary guides to the need for transfusion. Chronic anaemia in premature infants may, if severe, cause apnoea, poor neurodevelopmental outcomes or poor weight gain.On the other hand, red blood cell transfusion may result in transmission of infections, circulatory or iron overload, or dysfunctional oxygen carriage and delivery.

OBJECTIVES

To determine if erythrocyte transfusion administered to maintain low as compared to high haemoglobin thresholds reduces mortality or morbidity in very low birth weight infants enrolled within three days of birth.

SEARCH METHODS

Two review authors independently searched the Cochrane Central Register of Controlled Trials (The Cochrane Library) , MEDLINE,EMBASE, and conference proceedings through June 2010.

SELECTION CRITERIA

We selected randomised controlled trials (RCTs) comparing the effects of early versus late, or restrictive versus liberal erythrocyte transfusion regimes in low birth weight infants applied within three days of birth, with mortality or major morbidity as outcomes.

Acute physiological effects of packed red blood cell transfusion in preterm infants with different degrees of anaemia

OBJECTIVE

The safe lower limit of haematocrit or haemoglobin that should trigger a red blood cell (RBC) transfusion has not been defined. The objective of this study was to examine the physiological effects of anaemia and compare the acute responses to transfusion in preterm infants who were transfused at higher or lower haematocrit thresholds.

METHODS

The authors studied 41 preterm infants with birth weights 500-1300 g, who were enrolled in a clinical trial comparing high ('liberal') and low ('restrictive') haematocrit thresholds for transfusion. Measurements were performed before and after a packed RBC transfusion of 15 ml/kg, which was administered because the infant's haematocrit had fallen below the threshold defined by study protocol. Haemoglobin, haematocrit, RBC count, reticulocyte count, lactic acid and erythropoietin were measured before and after transfusion using standard methods. Cardiac output was measured by echocardiography. Oxygen consumption was determined using indirect calorimetry. Systemic oxygen transport and fractional oxygen extraction were calculated.

RESULTS

Systemic oxygen transport rose in both groups following transfusion. Lactic acid was lower after transfusion in both groups. Oxygen consumption did not change significantly in either group. Cardiac output and fractional oxygen extraction fell after transfusion in the low haematocrit group only.

CONCLUSIONS

These study's results demonstrate no acute physiological benefit of transfusion in the high haematocrit group. The fall in cardiac output with transfusion in the low haematocrit group shows that these infants had increased their cardiac output to maintain adequate tissue oxygen delivery in response to anaemia and, therefore, may have benefitted from transfusion.

Effect of transfusion on the venous blood lactate level in very low-birthweight infants

BACKGROUND

In recent years the blood lactate level can be easily and quickly measured with a small amount of blood, and the availability of an arterial blood lactate level has been reported as an indicator of oxygen deficit in adults. To determine whether venous blood lactate level can serve as such a marker for determining the indications for transfusion, blood lactate and hemoglobin level were monitored before and after transfusion.

METHODS

The study subjects consisted of 12 very low-birthweight infants admitted to the neonatal intensive care unit and who had transfusion between June 2005 and June 2007. The data on the blood lactate and hemoglobin were collected retrospectively by referring to the clinical records.

RESULTS

A total of 18 transfusions was performed. There was no significant relationship between venous blood lactate and hemoglobin concentration before transfusion. The subjects were classified into two groups according to the lactate level before transfusion: > or =3.3 mmol/L and <3.3 mmol/L. In the high-lactate group the lactate decreased significantly after transfusion (P < 0.01) and it continued to decrease thereafter. In the low-lactate group, however, the lactate remained unchanged.

CONCLUSIONS

Venous blood lactate measurements may offer some additional information regarding the optimal time for performing a transfusion. To the authors' knowledge this is the first report to study the changes in lactate levels using venous blood sampling in red blood cell transfusion in very low-birthweight infants.

Anemia in the preterm infant: erythropoietin versus erythrocyte transfusion--it's not that simple

Since the late 1980s recombinant human erythropoietin (r-EPO) has been studied as an alternative to packed red blood cell (RBC) transfusion for the treatment of anemia of prematurity in very low birth weight infants. Initial trials and reports focused on r-EPO's ability to prevent or treat anemia of prematurity with the goal of eliminating RBC transfusion but achieved limited success. New concerns about the safety of r-EPO administration have emerged. Past cost-benefit analyses of r-EPO administration versus transfusion for the treatment of anemia of prematurity have been nearly balanced. Autologous transfusion, blood-sparing technologies, changes in RBC transfusion technique and safety, and further elucidation of the risk-benefit ratio of r-EPO therapy may change the cost-benefit analysis.

Anemia in the preterm infant: erythropoietin versus erythrocyte transfusion--it's not that simple

Since the late 1980s recombinant human erythropoietin (r-EPO) has been studied as an alternative to packed red blood cell (RBC) transfusion for the treatment of anemia of prematurity in very low birth weight infants. Initial trials and reports focused on r-EPO's ability to prevent or treat anemia of prematurity with the goal of eliminating RBC transfusion but achieved limited success. New concerns about the safety of r-EPO administration have emerged. Past cost-benefit analyses of r-EPO administration versus transfusion for the treatment of anemia of prematurity have been nearly balanced. Autologous transfusion, blood-sparing technologies, changes in RBC transfusion technique and safety, and further elucidation of the risk-benefit ratio of r-EPO therapy may change the cost-benefit analysis.

Myocardial adaptation to anemia and red blood cell transfusion in premature infants requiring ventilation support in the 1st postnatal week

BACKGROUND

Although transfusion practice in very premature infants is becoming more restrictive, little is known about myocardial adaptation to anemia during the 1st postnatal week.

OBJECTIVES

To determine the central hemodynamic effects of anemia and red blood cell transfusion in very preterm infants undergoing intensive care.

METHODS

Twenty-nine neonates of less than 30 weeks gestational age were treated for respiratory distress syndrome, following a strict protocol. Echocardiographies were performed at the 4th and 6th postnatal days, which corresponded to, respectively, just before and 48 h after an erythrocyte transfusion of 15 ml/kg in the 12 anemic infants.

RESULTS

Anemic infants had increased stroke volume [2.1 (1.8-2.3) vs. 1.5 (1.3-1.6) ml/kg] and left ventricular (LV) output [312 (271-345) vs. 206 (177-240) ml/min/kg]. The relationship of the heart rate-corrected velocity of circumferential fiber shortening to LV end-systolic meridional wall stress indicated a higher contractile state in the anemic infants, with a higher y-intercept (p = 0.03) and a steeper slope (p = 0.05) of the regression line than in the nonanemic patients. Posttransfusion, the stroke volume, LV output, shortening fraction, and contractile state decreased to the values observed in the nonanemic infants.

CONCLUSIONS

Myocardial contractility was a major component of the circulatory adjustments in the anemic premature infants requiring ventilation support in the early neonatal period. Changes in LV performance associated with anemia were reversed by transfusion with no detrimental effect on right ventricular function, LV preload or the respiratory status of these patients.

Comparison of a Restricted Transfusion Schedule with Erythropoietin Therapy versus a Restricted Transfusion Schedule Alone in Very Low Birth Weight Premature Infants

OBJECTIVE

Erythropoietin (EPO) is commonly used in very low birth weight neonates to minimize blood transfusions during hospitalization. Data are limited comparing the use of EPO along with a restricted transfusion schedule versus a restricted transfusion schedule alone. We compared the effects of a restricted transfusion schedule with EPO versus a restricted transfusion schedule alone during two consecutive 6-month periods.

METHODS

In period I, infants born at <30 weeks gestational age (GA) or <1,500 g birth weight (BW) were treated prophylactically for six weeks with EPO 1,000 U/kg/wk in three divided doses and blood transfusions were given using a restricted transfusion schedule. This was the called the EPO Group. In period II, a restricted transfusion schedule was utilized, but EPO was not administered. This constituted the No EPO Group. No other changes in clinical practice were introduced in either period.

RESULTS

There were 30 neonates in the EPO Group and 20 in the No EPO Group. There were no significant differences in sex, race, mean birth weight (1,074 +/- 283 versus 965 +/- 330 g), mean gestational age (28.9 +/- 2.96 versus 27.8 +/- 2.86 wks), 5 minute Apgar score (7.8 +/- 1.2 versus 7.6 +/- 1.1), or mean hematocrit (48.2% +/- 6.05 versus 48.6% +/- 6.31) at admission. There were no significant differences in the total number of transfusions between the two periods. In the EPO Group, 8/30 patients received 27 transfusions. Six transfusions violated guidelines based on hematocrit level. EPO was discontinued in three infants secondary to treatment-related neutropenia. There were two deaths unassociated with EPO treatment. Excluding deaths, 6 patients received 16 transfusions. In the No EPO Group, 8/20 patients received 13 transfusions. Two transfusions violated guidelines based on hematocrit. There were three deaths and one patient transfer. Excluding these four patients, 6 infants received 11 transfusions (P < or = 1.) Among survivors, there were no significant differences in mean total length of stay (49.3 +/- 22.7 versus 53.2 +/- 26.4 d), mean discharge weight (2,144 +/- 405 versus 2,358 +/- 458 g), or average weight gain/d (20.7 +/- 5.44 versus 22.6 +/- 6.81 g), between the two groups respectively, nor were there significant differences when all babies were included in the analysis. There was a significant difference in mean hematocrit at discharge, respectively, (38.3% +/- 6.84 versus 31.4% +/- 6.26; P = 0.003) in survivors.

CONCLUSIONS

A restricted transfusion schedule without EPO use was associated with lower mean hematocrit at discharge, but not with an increased frequency of transfusions, nor significant differences in length of stay, discharge weight, or average daily weight gain. A restricted transfusion schedule alone avoided side effects and costs associated with EPO. Indications for transfusion and what constitutes appropriate levels of hemoglobin still require clinical investigation, including long-term clinical outcomes.

Erythropoietin and prematurity--where do we stand?

Erythropoietin (EPO) treatment for anemia of prematurity is still controversial. Large multicentric trials demonstrate that administration of EPO+Fe cannot prevent early transfusions, particularly in very low birth weight newborns and in infants with severe neonatal diseases, but may have some beneficial effect to prevent late transfusions. Current treatment of anemia of prematurity should be multifactorial trying to minimize all causes that reduce erthrocytic mass (phlebotomies, use of noninvasive procedures) and promoting all factors that increase it (placental transfusion, adequate nutrition support). To evaluate the real impact of EPO treatment it is mandatory to follow similar transfusion protocols for preterm infants in all the studies. The aim of EPO+Fe administration should be to avoid new late transfusions in very low birth weight preterm infants or to prevent the first transfusion after the second week of life in less immature premature with the objective of reducing the number of donors rather than the number of transfusions. We have limited the use of EPO+Fe to infants <30 weeks gestational age and birth weight <or=1250 g as well as to infants weighing 1250-1500 g with initial severe disease. The comparison of outcomes before (28 months period with EPO+Fe treatment to all premature <or=32 weeks gestational age) and after 20 months of implementation of the new protocol showed a significant decrease in EPO+Fe treatment candidates (40.3% vs. 85.9%, P<0.001) without changes in the percentage of transfusions in both periods. Therefore if EPO treatment is to be given it should be limited to preterm infants with a birth weight <1000 g or those of 1000-1250 g associated with risk factors for blood transfusion. It should be started at 3-7 days of life at doses of 250 U/kg subcutaneously, three times a week, for 4-6 weeks depending on gestational age with oral iron 2-12 mg/kg/day to keep ferritin levels greater than 100 ng/mL.

Effects of transfusion in anemia of prematurity

The authors aimed to test the hypothesis that blood transfusions depress hematopoiesis in healthy infants with anemia of prematurity (AOP). They also set out to find markers that predict recovery from AOP. Thirty-nine premature babies underwent weekly and post-transfusion measurements of hemoglobin concentrations, reticulocyte counts (RCC), and erythropoietin levels (EPO). RCC and EPO dropped significantly 7 days after a blood transfusion but had normalized after 14 days. Elevated RCC or EPO levels were not predictive of an increase in hemoglobin. Postnatal HbFg/dL was higher in babies who had received transfusions. The authors conclude that blood transfusions depress erythropoiesis in infants with AOP and stimulate HbF synthesis but this effect is not sustained. Reticulocyte counts and erythropoietin levels are unhelpful in predicting recovery from AOP.

Randomized trial of liberal versus restrictive guidelines for red blood cell transfusion in preterm infants

OBJECTIVE

Although many centers have introduced more restrictive transfusion policies for preterm infants in recent years, the benefits and adverse consequences of allowing lower hematocrit levels have not been systematically evaluated. The objective of this study was to determine if restrictive guidelines for red blood cell (RBC) transfusions for preterm infants can reduce the number of transfusions without adverse consequences.

DESIGN, SETTING, AND PATIENTS

We enrolled 100 hospitalized preterm infants with birth weights of 500 to 1300 g into a randomized clinical trial comparing 2 levels of hematocrit threshold for RBC transfusion.

INTERVENTION

The infants were assigned randomly to either the liberal- or the restrictive-transfusion group. For each group, transfusions were given only when the hematocrit level fell below the assigned value. In each group, the transfusion threshold levels decreased with improving clinical status.

MAIN OUTCOME MEASURES

We recorded the number of transfusions, the number of donor exposures, and various clinical and physiologic outcomes.

RESULTS

Infants in the liberal-transfusion group received more RBC transfusions (5.2 +/- 4.5 [mean +/- SD] vs 3.3 +/- 2.9 in the restrictive-transfusion group). However, the number of donors to whom the infants were exposed was not significantly different (2.8 +/- 2.5 vs 2.2 +/- 2.0). There was no difference between the groups in the percentage of infants who avoided transfusions altogether (12% in the liberal-transfusion group versus 10% in the restrictive-transfusion group). Infants in the restrictive-transfusion group were more likely to have intraparenchymal brain hemorrhage or periventricular leukomalacia, and they had more frequent episodes of apnea, including both mild and severe episodes.

CONCLUSIONS

Although both transfusion programs were well tolerated, our finding of more frequent major adverse neurologic events in the restrictive RBC-transfusion group suggests that the practice of restrictive transfusions may be harmful to preterm infants.

Reduction in red blood cell transfusions using a bedside analyzer in extremely low birth weight infants

BACKGROUND

Preterm infants typically experience heavy phlebotomy losses from frequent laboratory testing in the first few weeks of life. This results in anemia, requiring red blood cell (RBC) transfusions. We recently introduced a bedside point-of-care (POC) blood gas analyzer (iSTAT, Princeton, NJ) that requires a smaller volume of blood to replace conventional Radiometer blood gas and electrolyte analysis used by our neonatal intensive care unit (NICU). The smaller volume of blood required for sampling (100 vs 300-500 microl), provided an opportunity to assess if a decrease in phlebotomy loss occurred and, if so, to determine if this resulted in decreased transfusions administered to extremely low birth weight (ELBW) infants.

OBJECTIVE

We hypothesized that the use of the POC iSTAT analyzer that measures pH, PCO(2), PO(2), hemoglobin, hematocrit, serum sodium, serum potassium and ionized calcium would result in a significant decrease in the number and volume of RBC transfusions in the first 2 weeks of life.

DESIGN/METHODS

A retrospective chart review was conducted of all inborn premature infants with birth weights less than 1000 g admitted to the NICU that survived for 2 weeks of age during two separate 1-year periods. Blood gas analysis was performed by conventional laboratory methods during the first period (designated Pre-POC testing) and by the iSTAT POC device during the second period (designated post-POC testing). Data collected for individual infants included the number of RBC transfusions, volume of RBCs transfused, and the number and kind of blood testing done. There was no effort to change either the RBC transfusion criteria applied or blood testing practices.

RESULTS

The mean (+/-SD) number of RBC transfusions administered in the first 2 weeks after birth was 5.7+/-3.74 (n=46) in the pre-POC testing period to 3.1+/-2.07 (n=34) in the post-POC testing period (p<0.001), a 46% reduction. The mean volume of RBC transfusions decreased by 43% with use of the POC analyzer, that is, from 78.4+/-51.6 ml/kg in the pre-POC testing group to 44.4+/-32.9 ml/kg in the Post-POC testing group (p<0.002). There was no difference between the two periods in the total number of laboratory blood tests done.

CONCLUSIONS

Use of a bedside blood gas analyzer is associated with clinically important reductions in RBC transfusions in the ELBW infant during the first two weeks of life.

Issues in transfusing preterm infants in the NICU

Decisions regarding whether or not to transfuse preterm infants in the neonatal intensive care unit are often difficult. Although numbers of red blood cell transfusions have decreased in recent years, transfusions are still a common occurrence. For each infant, the advantages of transfusion must be balanced against the consequences and potential risks. This article examines physiologic and iatrogenic causes of anemia in preterm infants, clinical consequences of anemia, the use of transfusions and their risks, and the role of erythropoietin therapy.

Transfusion in pediatrics

In reviewing the literature, the authors noted an important variation in stated and observed transfusion practice patterns among pediatric critical care practitioners, and in published guidelines on RBC transfusion. They also noted a paucity of clinical evidence with respect to RBC transfusion to critically ill children. There has been only one large randomized trial in adults, and the authors do not believe that the results from this trial should be generalized to critically ill children because of the many differences in children and their adaptive responses, and differences in disease processes. More research about anemia and RBC transfusion to critically ill children must be performed. The TRIPICU study is testing the safety of giving more or less RBC transfusion to stable critically ill children. Other studies must be done on the epidemiology and determinants of RBC transfusion in PICUs, on prevention of transfusion, and on alternatives to RBC transfusion (eg, erythropoietin).

Hemodynamic changes in anemic premature infants: are we allowing the hematocrits to fall too low?

OBJECTIVE

Currently, many nurseries allow hematocrits to fall to <21% in apparently "stable" premature infants before considering a blood transfusion. We evaluated clinical changes and hemodynamic changes by echocardiogram in "stable" anemic premature infants before, during, and after transfusion.

METHODS

"Stable" premature infants (< or =32 weeks' gestation) who were to receive transfusions (2 aliquots of 10 mL/kg packed red blood cells, 12 hours apart) were eligible for prospective enrollment. Cardiac function by echocardiography and vital signs were measured 4 times: 1 to 3 hours before and 2 to 4 hours after the initial aliquot and 4 to 7 hours and 27 to 34 hours after the second aliquot. Infants were grouped prospectively according to pretransfusion hematocrit ranges for analysis: < or =21% (low), 22% to 26% (mid), and > or =27% (high).

RESULTS

Thirty-two infants were enrolled. No differences were observed between the groups in sex, birth weight, postconceptional age, or postnatal weight at enrollment. Before transfusion, low- and mid-range groups had higher left ventricular end systolic and diastolic diameters, in comparison with high range. Low range had increased stroke volume in comparison with the high-range group. These changes persisted after transfusion. Mean diastolic blood pressure rose and peak velocity in the aorta fell in the low-range group after transfusion. Pretransfusion hematocrit was correlated with but poorly predictive of echocardiographic measurements. Infants with inappropriate weight gain had increased ventricular end diastolic diameters, consistent with congestive heart failure.

CONCLUSIONS

Apparently "stable" anemic premature infants may be in a clinically unrecognized high cardiac output state, and some echocardiographic measurements do not improve within 48 hours after transfusion. The benefits of transfusion practices guided by measures of cardiac function should be evaluated.

The effect of blood transfusion on the hemoglobin oxygen dissociation curve of very early preterm infants during the first week of life

A study was conducted during the first week of life to determine the changes in P50 (PO2 required to achieve a saturation of 50% at pH 7.4 and 37 degrees C) and the proportions of fetal hemoglobin (HbF) and adult hemoglobin (HbA) prior to and after transfusion in very early preterm infants. Eleven infants with a gestational age < or = 27 weeks have been included in study. The hemoglobin dissociation curve and the P50 was determined by Hemox-analyser. Liquid chromatography was also performed to determine the proportions of HbF and HbA. The mean gestational age of the 11 infants was 25.1 weeks (+/- 1 weeks) and their mean birth weight was 736 g (+/- 125 g). They received 26.9 mL/kg of packed red cells. The mean P50 prior and after transfusion was 18.5 +/- 0.8 and 21.0 +/- 1 mm Hg (P = .0003) while the mean percentage of HbF was 92.9 +/- 1.1 and 42.6 +/- 5.7%, respectively. The data of this study show a decrease of hemoglobin oxygen affinity as a result of blood transfusion in very early preterm infants prone to O2 toxicity. The shift in HbO2 curve after transfusion should be taken into consideration when oxygen therapy is being regulated for these infants.

Human recombinant erythropoietin in the prevention and treatment of anemia of prematurity

Human recombinant erythropoietin has been studied extensively as treatment for a variety of anemias. Since in vitro studies showed the primary etiology of the anemia of prematurity to be insufficient serum erythropoietin concentrations, clinical trials have evaluated the administration of human recombinant erythropoietin to preterm infants to treat this indication. These studies were followed by pharmacokinetic determinations in animal models and preterm infants, which revealed that preterm infants required greater doses of human recombinant erythropoietin because of a more rapid clearance and greater volume of distribution. Recent studies have focused on the administration of human recombinant erythropoietin in the first weeks of life to alleviate the anemia caused by excessive phlebotomy losses, and to prevent the anemia of prematurity. In addition, human recombinant erythropoietin has been tried clinically in a variety of neonatal populations in an attempt to decrease or eliminate transfusions. Although much information has been accumulated about the clinical use of human recombinant erythropoietin in preterm infants over the last 15 years, many questions remain unanswered. The evolution of clinical practice in the care of extremely low birthweight infants continues to affect the number of transfusions. It is likely that human recombinant erythropoietin administration in combination with instituting rigorous transfusion guidelines and decreasing phlebotomy losses will have the greatest impact in decreasing transfusion requirements in all preterm and term neonates, regardless of the etiology of their anemia.

A pilot randomised controlled trial of peripheral fractional oxygen extraction to guide blood transfusions in preterm infants

BACKGROUND

Peripheral fractional oxygen extraction (FOE) may be a better indicator of the need for transfusion than the haemoglobin concentration (Hb) because it is a measure of the adequacy of oxygen delivery to meet demand. A randomised controlled trial of the use of peripheral FOE to guide the need for blood transfusions in preterm infants was carried out to test this hypothesis.

METHOD

Infants less than 1500 g birth weight who were stable and less than 2 weeks old were randomised to receive transfusions guided by either a conventional protocol based on Hb (conventional group) or a protocol based on measurements of peripheral FOE made by near infrared spectroscopy (NIRS group). Measurements of Hb and FOE were made on all infants from randomisation until discharge. The primary outcome measures were number of transfusions received, rate of weight gain, and postmenstrual age at discharge.

RESULTS

Thirty seven infants were randomised to each group. Birth weight (median, range) (1200, 1004-1373 v 1136, 1009-1285 g) and Hb (median, range) at randomisation (160, 149-179 v 155, 145-181 g/l) did not differ between the two groups. The total number of transfusions given to the NIRS group was 56 and to the conventional group 84. The median number of transfusions per infant, the median volume of blood transfused to each group, and the total number of donors to which infants were exposed were similar in the two groups. Infants transfused according to the conventional protocol were more likely to be transfused earlier and at a higher Hb than those transfused in the NIRS group. Infants in the conventional group spent a significantly shorter period than those in the NIRS group with Hb < 100 g/l. Of the 56 transfusions given to the NIRS group, 33 (59%) were given because of clinical concerns rather than because of high FOE. There was no difference in the rate of weight gain, rate of linear growth, postmenstrual age at discharge, or the incidence of chronic lung disease or retinopathy of prematurity.

CONCLUSIONS

FOE measurements failed to identify many infants felt by clinicians to require blood transfusion. This may have been because clinicians relied on conventional indicators of transfusion that are vague and non-specific, or a peripheral FOE of 0.47 alone may not be a sensitive enough predictor of the need for transfusion. This requires further study.

Anaemia of prematurity: treatment with erythropoietin

Anemia of prematurity is a hyporegenerative anemia usually appearing after the second week, reaching highest intensity in the second month of life. It's normocytic and normochromic with low reticulocyte count. It has been attributed to EPO deficiency. The low EPO levels detected in premature infants and the proper response to synthetic erythropoietin suggested that EPO administration in premature of < or =32 weeks gestational age could be of benefit trying to maintain or increase the hematocrit levels. Protocols of EPO administration to premature babies should always be considered as EPO+Fe, keeping ferritin levels over 100 ng/ml. Failures to EPO+Fe treatment in very small premature babies, measured as no decrease in the need of blood transfusions, may be due to the amount of blood looses that should be restricted.

Anemia of prematurity

Physiologic anemia is a common and normal finding in newborn infants. In preterm infants, anemia of prematurity is the result of this normal physiologic process compounded by the morbidity of prematurity. Premature infants reach their nadir hematocrit sooner and at a lower level than term. This article reviews the physiology of stem cell differentiation and the structure and function of the red blood cell, as well as examining red blood cell indices. It also addresses the etiology, symptomatology, diagnostic workups and treatment/prevention modalities of anemia of prematurity. Treatment for and prevention of anemia of prematurity remain controversial, and specific criteria are lacking.

Peripheral fractional oxygen extraction and other measures of tissue oxygenation to guide blood transfusions in preterm infants

The physiological effects of anemia in the preterm infant are complex and the indications for transfusions in preterm infants are controversial. A measure of the adequacy of tissue oxygenation may be a better guide to the need for transfusions than currently used criteria. This article considers 2 measures of tissue oxygenation of preterm infants: 1) The whole blood lactate concentration, and 2) Peripheral fractional oxygen extraction (FOE) by using near infrared spectroscopy. Several studies have shown falls in blood lactate concentration after blood transfusion, but it has been difficult to establish a convincing link between raised lactate concentrations and significant anemia because even anemic infants have lactate concentrations that are within or close to the normal range. Lactate concentrations may be affected by the haematocrit of the blood sample. Peripheral FOE can be measured by using near infrared spectroscopy with partial venous occlusion and has been studied in preterm infants with symptomatic and asymptomatic anaemia. Mean (SD) FOE was significantly higher in symptomatic [0.425 (0.06)] (P< .01) but not asymptomatic [0.334 (0.05)] compared to controls [0.352 (0.06)], (P = .22). After transfusion there was a significant fall in FOE in symptomatic infants to 0.367 (0.06) (P = .001) but there was no change in infants who were asymptomatic. FOE correlated with other measures known to reflect the adequacy of oxygen availability during anemia. These results suggest that peripheral FOE may be suitable as a guide to the need for blood transfusions. A pilot randomized controlled trial is currently being undertaken to test this hypothesis.

The use of erythropoietin in neonates

Although much information has been accumulated about the clinical use of Epo in preterm infants, many questions remain unanswered. The evolution of clinical practice in the care of extremely ill, preterm infants continues to affect the number of transfusions required during hospitalization. Decreasing phlebotomy losses and instituting standardized transfusion guidelines have both been shown significantly to decrease the transfusion requirements of preterm infants. The administration of Epo likely decreases transfusion need even further; however, the direct impact of each of these actions has not been studied prospectively. It is likely that the combination of instituting rigorous and standardized transfusion guidelines, decreasing phlebotomy losses, and the appropriate use of Epo will have the greatest impact in decreasing transfusion requirements in all preterm and term neonates, regardless of the cause of their anemia.

Adaptive responses during anemia and its correction in lambs

There is limited information available on which to base decisions regarding red blood cell (RBC) transfusion treatment in anemic newborn infants. Using a conscious newborn lamb model of progressive anemia, we sought to identify accessible metabolic and cardiovascular measures of hypoxia that might provide guidance in the management of anemic infants. We hypothesized that severe phlebotomy-induced isovolemic anemia and its reversal after RBC transfusion result in a defined pattern of adaptive responses. Anemia was produced over 2 days by serial phlebotomy (with plasma replacement) to Hb levels of 30-40 g/l. During the ensuing 2 days, Hb was restored to pretransfusion baseline levels by repeated RBC transfusion. Area-under-the-curve methodology was utilized for defining the Hb level at which individual study variables demonstrated significant change. Significant reciprocal changes (P < 0.05) of equivalent magnitude were observed during the phlebotomy and transfusion phases for cardiac output, plasma erythropoietin (Epo) concentration, oxygen extraction ratio, oxygen delivery, venous oxygen saturation, and blood lactate concentration. No significant change was observed in resting oxygen consumption. Cardiac output and plasma Epo concentration increased at Hb levels <75 g/l, oxygen delivery and oxygen extraction ratio decreased at Hb levels <60 g/l, and venous oxygen saturation decreased and blood lactate concentration increased at Hb levels <55 g/l. We speculate that plasma Epo and blood lactate concentrations may be useful measures of clinically significant anemia in infants and may indicate when an infant might benefit from a RBC transfusion.

Blood banking issues pertaining to neonatal red blood cell transfusions

Many preterm infants are given multiple red blood cell transfusions during the early weeks of life. Because firm standards for neonatal transfusions do not exist, it is important to consider the pathophysiology of the anemia of prematurity, the goals of transfusion therapy and blood banking practices that best provide safe and effective neonatal transfusions. There is increasing agreement that efforts continue to minimize phlebotomy blood losses, to transfuse per conservative indications and to limit donor exposure by transfusing stored red blood cells from a single unit reserved for an infant--rather than insisting on fresh blood.

Effects of blood transfusion on left ventricular output in premature babies

OBJECTIVE

To investigate the acute effects of red blood cell transfusion on haemodynamics in preterm babies.

SETTING

A neonatal unit in a University Hospital.

PATIENTS

Preterm babies whose postnatal age was less than four weeks and who required red blood cell transfusion.

MEASUREMENT

Cardiac output and left ventricular systolic function was determined using Doppler echocardiography before, one hour and 24 h after red blood cell transfusion. Blood pressure and haematocrit were also recorded at the same time. Mixed-effects regression model was used to analyse the effect of blood transfusion on left ventricular function and cardiac output.

RESULTS

57 preterm babies were recruited. Univariate analysis showed that cardiac index decreased significantly 24 h after transfusion (P<0.05). Systemic red cell transport increased by an average of 11.1% 24 h after transfusion (P<0.05). Multivariate analysis showed that the cardiac index was negatively associated with haematocrit and the index was higher in male babies.

CONCLUSION

There was a significant drop in cardiac index and an increase in systemic red cell transport 24 h after transfusion in premature babies.

Myocardial, erythropoietic, and metabolic adaptations to anemia of prematurity in infants with bronchopulmonary dysplasia

OBJECTIVES

The effects of anemia of prematurity during bronchopulmonary dysplasia (BPD) as well as on the metabolic and erythropoietic functions were determined before and after a transfusion. Fourteen anemic (Hb range: 65-88 gm/L), oxygen dependent (fraction of inspired oxygen < or = 35%), nonventilated, preterm infants with BPD were studied at a postnatal age of 6 +/- 2 weeks.

STUDY DESIGN

Cardiac output, heart rate, mean velocity of circumferential fiber shortening, shortening fraction (SF), and stroke volume were assessed by pulsed and continuous wave Doppler echocardiography. Values for resting oxygen consumption, carbon dioxide production, and energy expenditure were obtained by indirect calorimetry. The affinity of oxygenated hemoglobin was determined by a blood oxygen dissociation analyzer.

RESULTS

An increased hemoglobin level resulted in a suppression of erythropoietin secretion (p < 0.001), whereas heart rate, cardiac output, stroke volume, and SF decreased (p < 0.05). Weight gain before and after transfusion were similar. Plasma lactate levels decreased from 1.6 +/- 0.3 to 1.2 +/- 0.3. Oxygen consumption, carbon dioxide production, and energy expenditure were not affected.

CONCLUSIONS

Anemia of prematurity and BPD increase heart rate, cardiac output, stroke volume, and SF. These hemodynamic compensatory responses are normalized by transfusion.

Erythrocyte incorporation and absorption of 58Fe in premature infants treated with erythropoietin

We hypothesized that treatment of very low birth weight premature infants with r-HuEPO would increase erythrocyte incorporation and gastrointestinal absorption of iron. Infants with birth weights < or = 1.25 kg and gestational ages < 31 wk were randomized to receive 6 wk of 500 U of r-HuEPO/kg/wk (epo group, n = 7) or placebo (placebo group, n = 7). All infants received daily enteral supplementation with 6 mg of elemental iron per kg. An enteral test dose of a stable iron isotope, 58Fe, was administered after the 1st ("early dosing") and 4th ("late dosing") wk of treatment. Mean (+/-SD) erythrocyte incorporation of the dose of 58Fe administered determined 2 wk after early dosing was significantly greater in the epo group compared with the placebo group (4.4% +/- 1.6 versus 2.0 +/- 1.4%, p = 0.013). In contrast, after late 58Fe dosing, there was no difference between groups in incorporation (3.8 +/- 1.6% versus 5.5 +/- 2.7%). Within the epo group, percentage erythrocyte incorporation of 58Fe did not differ between early and late dosing, whereas in the placebo group it increased 3-fold (p < 0.01). Percentage absorption of 58Fe was not different between the epo and placebo groups after both early dosing (30 +/- 22% versus 34 +/- 8%) and late dosing (32 +/- 9% versus 31 +/- 6%). Absorption of nonlabeled elemental iron and 58Fe were significantly correlated with one another. The percentage of the absorbed 58Fe dose incorporated into Hb was not different between groups. We conclude that, although erythropoietin treatment stimulates erythrocyte iron incorporation in premature infants, it has no effect on iron absorption at the r-HuEPO dose studied.

Red blood cell transfusions for preterm infants: the role of evidence-based medicine

Increasingly clinicians attempt to base decisions regarding patient management on the results of clinical studies in addition to expert opinion and their own practical experience. In this article, the author reviews the published studies available to assist clinicians to make evidence-based decisions in three topics related to small volume red blood cell (RBC) transfusions for preterm infants; namely, studies examining the effects of RBC transfusions on possible symptoms of anemia such as tachypnea, apnea or other cardiorespiratory irregularities, studies investigating the collection and transfusion of umbilical cord blood and finally studies addressing the duration of storage and use of additive solutions for RBCs for transfusion to neonates. Based on the review of these studies, guidelines for small volume RBC transfusions in preterm infants are suggested.

Effects of increased red cell mass on subclinical tissue acidosis in hyaline membrane disease

AIM

To determine whether there are subclinical deficits in oxygen delivery in ventilated premature neonates.

METHOD

Ventilated premature neonates weighing less than 1500 g, who were transfused for anaemia or who were given colloids for clotting abnormalities (or oedema), were haemodynamically monitored during the first week of life. Calf muscle surface pH (pH) was measured in conjunction with peripheral limb blood flow by occlusion plethysmography.

RESULTS

Packed red blood cell transfusions corrected a subclinical regional tissue acidosis (low tpH) without affecting arterial pH or limb blood flow. This observation also correlated with an increase in regional oxygen delivery. The data were also suggestive of a pattern of pathological, supply dependent, oxygen delivery and are similar to other observations made in adults with adult respiratory distress syndrome.

CONCLUSIONS

Packed red blood cells increase regional oxygen delivery and tissue surface pH. In contrast, colloid infusion provided no substantial cardiovascular or metabolic benefit to these patients and should be avoided when oxygen delivery is at issue and when there may be leaky pulmonary capillaries.

Do cardiac output and serum lactate levels indicate blood transfusion requirements in anemia of prematurity?

BACKGROUND

Whether and when to transfuse in anemia of prematurity is highly controversial. Some authors suggest transfusions simply if the hemoglobin (Hb) level is below a defined normal range. Others propose the use of clinical or laboratory parameters in anemic patients to decide whether to transfuse or not.

HYPOTHESIS

A decreasing amount of circulating Hb should cause a compensatory increase in cardiac output (CO) and an increase in arterial serum lactate.

MATERIALS AND METHODS

In 56 anemic preterm infants (not in respiratory or hemodynamic failure) we analyzed CO after the first week of life using a Doppler sonographic method. At the same time serum lactate levels, Hb levels and oxygen saturation were registered. Nineteen of these patients were given transfusion when they demonstrated clinical signs of anemia by tachycardia > 180/min, tachypnea, retractions, apneas and centralization (group 2). The remaining 37 patients were not transfused (group 1). Serum lactate, CO, heart rate (HR), oxygen delivery, respiratory rate, capillary refill and Hb were analyzed in both groups and in group 2 before and 12-24 h after transfusion. Data between groups 1 and 2 and in group 2 before and after transfusion were compared.

RESULTS

In the 56 patients studied no linear correlation between Hb and CO or between Hb and serum lactate was found. Nor could any correlation be demonstrated between the other variables studied. Examining the subgroups separately, a negative linear correlation was demonstrated between serum lactate and oxygen delivery in group 2. No other significant correlations were detected. However, when the pre- and post-transfusion data were compared in group 2 (increase of Hb from 9.45 (SD 3.44) to 12.5 (SD 3.8) g/100 ml), the CO decreased from 281.3 (SD 162.6) to 224 (SD 95.7) ml/kg per min (p < 0.01) and serum lactate decreased significantly from 3.23 mmol/l (SD 2.07) before to 1.71 (SD 0.83) after transfusion. Oxygen delivery was 35.8 (+/- 0.19) ml/kg per min group 1, 27.8 (+/- 0.05) pre- and 43.4 (+/- 0.07) post-transfusion in group 2 (p < 0.01).

CONCLUSIONS

CO measurements and serum lactate levels add little information to the decision-making process for blood transfusions, as neither CO nor serum lactate levels correlate with HB levels in an otherwise asymptomatic population of preterm infants. In infants where the indication for blood transfusion is made based on traditionally accepted clinical criteria, serum lactate is an additional laboratory indicator of impaired oxygenation, as it correlates significantly with oxygen delivery. A significant lower oxygen delivery in patients in whom blood transfusion is indicated and an increase in oxygen induced by transfusion demonstrate the value of these criteria in identifying preterm infants who benefit from transfusion.

Erythropoietin (Epo), protein and iron supplementation and the prevention of anaemia of prematurity: effects on serum immunoreactive Epo, growth and protein and iron metabolism

The effect of recombinant human (r-Hu) erythropoietin (Epo) (300 IU/Kg per week for 4 weeks) was studied in healthy preterm infants (n = 14) fed human milk with additional milk protein and high doses of iron. The controls (n = 15) were in themselves a study group and were used to follow the natural course of anaemia of prematurity on such nutrition. Serum immunoreactive Epo (SiEpo) increased significantly 24 h after r-HuEpo injections (range 36 to > 128 mU/ml) and remained at these levels throughout the treatment period. r-HuEpo in such moderate doses kept haemoglobin above 11 g/dl. Bodyweight gain, protein and iron parameters indicated adequacy of dietary protein and iron. In controls, siEpo increased during the first weeks after nutritional supplementation, with a concommitant rise in reticulocyte count. At age 3 weeks, despite low siEpo levels, reticulocyte counts indicated active erythropoiesis. Following further moderate increases in siEpo, the reticulocyte count increased to high levels (7%). The reticulocyte response suggests that erythropoiesis in preterm infants is less dependent upon Epo levels than in adults.

Haemodynamic effects of differing blood transfusion rates in infants less than 1500 g

OBJECTIVE

To investigate whether the haemodynamic effects of the standard 2-3 h blood transfusion increases the risk for intraventricular haemorrhage (IVH) and patent ductus arteriosus (PDA) in very low birthweight infants.

METHODOLOGY

In a randomized controlled study, haemodynamic changes using slow and rapid transfusion were compared. Twenty-seven very low birthweight infants were divided between 12h (n = 14) and 3h (n = 13) transfusion groups. Blood pressure, ejection fraction (EF), anterior cerebral artery pulsatility index (PI), blood gases, serum electrolytes and haematocrit were measured pre- and post-transfusion. Infectious status was also monitored.

RESULTS

Blood pressure (48.1/25.5 vs 55.7/30.2 mmHg) and EF (0.68 vs 0.73) increased significantly during rapid transfusion (P<0.01) but remained stable with slow transfusion. Serum potassium, base excess and incidence of infection did not increase in either group.

CONCLUSIONS

Slow transfusion causes less haemodynamic disturbance than rapid transfusion, thereby preventing the potential risk for IVH and PDA.