Critical haemoglobin thresholds in premature infants

Bone biology in postnatal Wistar rats following hypoxia-reoxygenation

Hypoxia response pathways have a central role in normal and abnormal bone biology but the effect of systemic hypoxia-reoxygenation on bone is not clear. Following hypoxic exposure, aberrant synthesis, folding and trafficking of proteins has been reported to occur, which can result in endoplasmic reticulum (ER) stress and may finally cause cell death. This study aimed to examine the effect of systemic hypoxia-reoxygenation injury on bone biology in postnatal rats. Immunoexpression of HIF-1α and VEGF was upregulated in femurs of newborn Wistar rats in response to systemic hypoxia-reoxygenation. Along with that, increased apoptosis of osteoblast precursors, osteoblasts, osteocytes and endothelial cells was observed in comparison to femurs of control animals by transmission electron microscopy, TUNEL staining and immunoexpression of cleaved caspase-3. The viability of osteoclasts was not affected. After hypoxia-reoxygenation, ER stress was observed in the osteoblasts and osteocytes as indicated by dilatation of the ER and enhanced immunoexpression of the ER stress marker GRP78. Localisation of collagen α1 immunoreaction was widespread in the bone matrix of control femurs but was confined to the osteoblasts and osteocytes in response to hypoxia-reoxygenation. In support of these findings, in vitro work showed reduced viability of osteoblast-like SaOs-2 cells and upregulation of GRP78 protein expression in them by western blotting following exposure to hypoxia. This suggests that systemic hypoxia-reoxygenation may disturb bone biology in postnatal Wistar rats by inducing ER stress and apoptosis in osteoblasts and osteocytes, without affecting the viability of osteoclasts. More in-depth research is needed to confirm causality between ER stress and apoptosis of osteoblasts and osteocytes.

Myocardial assessment using tissue doppler imaging in preterm very low-birth weight infants before and after red blood cell transfusion

OBJECTIVE

To investigate myocardial velocities in anemic very low-birth weight (VLBW) preterm infants, pre and post red blood cells transfusion using tissue Doppler imaging echocardiography.

STUDY DESIGN

Forty-eight VLBW preterm infants34 weeks and>2 weeks old were prospectively divided: Transfused symptomatic infants (Hematocrit (Hct)<0.30 (n=32)) and non transfused asymptomatic controls (control 1, Hct >0.30 (n=9) and control 2, Hct <0.30 (n=7)). Echocardiography was performed before and 3-5 days after transfusion in the transfused, and the controls were studied at similar intervals. Non parametric tests were used for statistical analysis.

RESULT

Left ventricular (LV) systolic velocity increased (transfused (4.6±0.70 vs 6.0±0.65, P<0.01)) as did LV diastolic velocities (P<0.01) without significant difference over time in each control. The percentage change in LV velocity following transfusion correlated negatively (ρ=0.36) with pre transfusion Hct.

CONCLUSION

There is a significant increase in myocardial performance following transfusion, which is related to the severity of the anemia.

Vascular endothelial growth factor as marker for tissue hypoxia and transfusion need in anemic infants: a prospective clinical study

OBJECTIVE

Oxygen-carrying capacity of blood is reduced in anemic infants because of low hemoglobin levels. Red blood cell transfusions become necessary if low hematocrit causes tissue hypoxia. No reliable parameters exist for detecting chronic tissue hypoxia. Vascular endothelial growth factor is upregulated by hypoxia; hence, elevated vascular endothelial growth factor levels may be a marker for tissue hypoxia and may indicate the need for red blood cell transfusions.

METHODS

In a prospective study, plasma vascular endothelial growth factor levels were measured in 3 groups of infants suspected of requiring red blood cell transfusions to find a vascular endothelial growth factor cutoff value indicative of tissue hypoxia. The 3 groups were acute anemic (an episode of acute bleeding [hematocrit drop > 5%] per day); chronic anemic (hematocrit drop < 5% per day); and nontransfused (hematocrit drop < 5% per day) but not meeting clinical criteria for a transfusion. Blood was sampled before transfusion and again 48 hours after transfusion if required. Plasma vascular endothelial growth factor and erythropoietin concentrations were measured.

RESULTS

Vascular endothelial growth factor concentrations were lower in acutely anemic compared with chronically anemic infants, whereas erythropoietin levels did not differ between these groups. The vascular endothelial growth factor concentration was <140 pg/mL in all acutely anemic infants, and this was deemed the threshold level indicating sufficient tissue oxygenation in subsequent analysis. We found that 30% of chronically anemic and 43% of nontransfused infants had vascular endothelial growth factor levels of >140 pg/mL. In transfused infants, with elevated vascular endothelial growth factor levels, red blood cell transfusion resulted in lowering of vascular endothelial growth factor concentrations.

CONCLUSIONS

Vascular endothelial growth factor concentrations of >140 pg/mL may indicate insufficient oxygen delivery to tissues and may serve as a marker of the need for transfusion or of tissue hypoxia in other diseases.

Predictive factors for survival for out-born infants born between 23 and 24 weeks of gestation in the post-surfactant era: fourteen years' experience in a single neonatal care unit, 1987-2000

BACKGROUND

The purpose of the present paper was to identify the predictive factors for survival for out-born infants born between 23 and 24 weeks of gestation.

METHODS

Ninety-two infants born between 23 and 24 weeks' gestation who were admitted to a level III neonatal intensive care unit from 1987 to 2000, were retrospectively studied. Survival was defined as discharge from the neonatal intensive care unit. Logistic regression was done to determine which clinical factors were most predictive of survival. The independent variables that were entered into the models were determined by preliminary univariate analysis.

RESULTS

Ninety-two infants were enrolled in the present study, 49 of whom survived in the surfactant era. The four variables that were found to be most predictive for survival on logistic regression were systolic blood pressure at 6 h (odds ratio [OR], 1.3; 95% confidence interval [CI]: 1.11-1.44 1 mmHg), ventilatory index < 0.047 (OR, 4.8; 95%CI: 1.07-21.65), initial hemoglobin value (OR, 1.6; 95%CI: 1.09-2.34/1 g/dL), and base excess at 6 h (OR, 2.1; 95%CI: 1.08-1.84/5 mEq/L).

CONCLUSIONS

A total of 53.2% of infants delivered between 23 and 24 weeks of gestation survived at discharge after introduction of surfactant replacement therapy. Early cardiopulmonary adaptation and initial hemoglobin value are key factors for survival in infants born at 23-24 weeks of gestation.

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.

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.

Functional versus fractional oxygen saturation readings: bias and agreement using simulated solutions and adult blood

The purpose of this study was to examine the bias and agreement between functional oxygen saturation (SO2) and fractional oxyhemoglobin (HbO2) using simulated quality control (QC) solutions and adult blood. Using a hemoximeter, 5 analysts performed at least 5 tests each on QC solutions with 3 different hemoglobin (Hb) levels and on adult blood samples of various oxygen saturation levels representing venous or arterial samples. Bias and the limits of agreement were determined using the technique of Bland and Altman. Using QC solutions with low, normal, and high Hb levels, the bias for SO2 against HbO2 was 20.82 +/- 0.50 (n = 66), 19.14 +/- 0.56 (n = 81), and 19.59 +/- 0.43 (n = 79), respectively, with SO2 reading consistently higher. The correlation between SO2 and HbO2 was -0.49, -0.69, and -0.68, respectively. Using adult blood, the bias for SO2 against HbO2 was 1.29 +/- 0.48 for venous samples (n = 62) and 1.9 +/- 0.19 for fully oxygenated samples (n = 36), and the correlation between SO2 and HbO2 was 1.0 and 0.68, respectively. These findings suggest that the consistency between the measurements of SO2 and HbO2 may be dependent on hemoglobin levels and oxygenation status. Thus, caution is warranted when assuming that the measurements of SO2 and HbO2 are interchangeable.