Erythropoietin pharmacokinetic/pharmacodynamic analysis suggests higher doses in treating neonatal anemia

A Mechanism-Based Population Pharmacokinetics Model of Erythropoietin in Premature Infants and Healthy Adults Following Multiple Intravenous Doses

The objective of the current study was to develop a population pharmacokinetics (PK) model for erythropoietin (Epo) in premature infants and healthy adults to characterize the variation in PK, and to study the differences in Epo PK in these 2 populations. Thirteen very low-birth-weight premature infants (<1500 g at birth), and 10 healthy adults received up to 4 intravenous doses of Epo that ranged from 10 to 500 U/kg. The final model had a target-mediated saturable, nonlinear, elimination pathway that incorporated the mechanism of Epo binding to its receptors along with a parallel linear, central elimination pathway. Epo clearance was found to be significantly higher in preterm infants compared to adults. Epo clearance via the nonlinear pathway was found to be much higher in infants; they had an Epo receptor capacity of 133 pM vs 86.6 pM in adults, which is most likely due to the higher erythroid progenitor cell mass per kilogram of body weight in infants. The parallel linear elimination was found to be more dominant in adults, reaching 91% of the total clearance with a 500-U/kg dose compared to just 6.1% of the total clearance following the same dose in preterm infants. Thus, this mechanism-based population PK model revealed that receptor-based nonlinear elimination is the dominant Epo elimination pathway in premature infants, and parallel linear elimination is dominant in adults.

Erythropoietin attenuates motor neuron programmed cell death in a burn animal model

Burn-induced neuromuscular dysfunction may contribute to long-term morbidity; therefore, it is imperative to develop novel treatments. The present study investigated whether erythropoietin (EPO) administration attenuates burn-induced motor neuron apoptosis and neuroinflammatory response. To validate our hypothesis, a third-degree hind paw burn rat model was developed by bringing the paw into contact with a metal surface at 75°C for 10 s. A total of 24 male Sprague–Dawley rats were randomly assigned to four groups: Group A, sham-control; Group B, burn-induced; Group C, burn + single EPO dose (5000 IU/kg i.p. at D0); and Group D, burn + daily EPO dosage (3000 IU/kg/day i.p. at D0–D6). Two treatment regimens were used to evaluate single versus multiple doses treatment effects. Before sacrifice, blood samples were collected for hematological parameter examination. The histological analyses of microglia activation, iNOS, and COX-2 in the spinal cord ventral horn were performed at week 1 post-burn. In addition, we examined autophagy changes by biomarkers of LC3B and ATG5. The expression of BCL-2, BAX, cleaved caspase-3, phospho-AKT, and mTOR was assessed simultaneously through Western blotting. EPO administration after burn injury attenuated neuroinflammation through various mechanisms, including the reduction of microglia activity as well as iNOS and COX-2 expression in the spinal cord ventral horn. In addition, the expression of phospho-AKT, mTOR and apoptotic indicators, such as BAX, BCL-2, and cleaved caspase-3, was modulated. Furthermore, the activity of burn-induced autophagy in the spinal cord ventral horn characterized by the expression of autophagic biomarkers, LC3B and ATG5, was reduced after EPO administration. The present results indicate that EPO inhibits the AKT-mTOR pathway to attenuate burn-induced motor neuron programmed cell death and microglia activation. EPO can modulate neuroinflammation and programmed cell death and may be a therapeutic candidate for neuroprotection.

Why do four NICUs using identical RBC transfusion guidelines have different gestational age-adjusted RBC transfusion rates?

OBJECTIVE

To compare neonatal red blood cell (RBC) transfusion rates in four large Intermountain Healthcare NICUs, all of which adhere to the same RBC transfusion guidelines.

STUDY DESIGN

This retrospective analysis was part of a transfusion-management quality-improvement project. De-identified data included RBC transfusions, clinical and laboratory findings, the anemia-prevention strategies in place in each NICU, and specific costs and outcomes.

RESULT

Of 2389 NICU RBC transfusions given during the 4-year period studied, 98.9 ± 2.1% (mean ± S.D.) were compliant with our transfusion guidelines, with no difference in compliance between any of the four NICUs. However, RBC transfusion rates varied widely between the four, with averages ranging from 4.6 transfusions/1000 NICU days to 21.7/1000 NICU days (P < 0.00001). Gestational age-adjusted transfusion rates were correspondingly discordant (P < 0.00001). The lower-transfusing NICUs had written anemia-preventing guidelines, such as umbilical cord milking at very low birth weight delivery, use of cord blood for admission laboratory studies, and darbepoetin dosing for selected neonates. Rates of Bell stage ⩾ 2 necrotizing enterocolitis and grade ⩾ 3 intraventricular hemorrhage were lowest in the two lower-transfusing NICUs (P < 0.0002 and P < 0.0016). Average pharmacy costs for darbepoetin were $84/dose, with an average pharmacy cost of $269 per transfusion averted. With a cost of $900/RBC transfusion, the anemia-preventing strategies resulted in an estimated cost savings to Intermountain Healthcare of about $6970 per 1000 NICU days, or about $282,300 annually.

CONCLUSION

Using transfusion guidelines has been shown previously to reduce practice variability, lower transfusion rates and diminish transfusion costs. Based on our present findings, we maintain that even when transfusion guidelines are in place and adhered to rigorously, RBC transfusion rates are reduced further if anemia-preventing strategies are also in place.

Using umbilical cord blood for the initial blood tests of VLBW neonates results in higher hemoglobin and fewer RBC transfusions

OBJECTIVE

We previously described a method for reducing early phlebotomy losses from very low birth weight (VLBW) neonates by obtaining the initial blood tests from otherwise discarded fetal blood from the placenta. In the present study we sought to; (1) measure the feasibility of performing this method in actual practice, (2) test the hypothesis that this method would result in higher hemoglobin concentrations and lower erythrocyte transfusion rates in the first week after birth.

METHODS

We conducted two studies in three Intermountain Healthcare NICUs. The first was a feasibility analysis involving 96 VLBW neonates, measuring the success of obtaining the NICU admission laboratory blood tests this way. The second study used case-control methodology to test the hypothesis that this method would result in a higher blood hemoglobin 12 to 24 h after birth, and a lower proportion receiving an erythrocyte transfusion in the first week.

RESULT

In 91 of 96 VLBW neonates (95%) the initial blood tests were successfully obtained with this method. The success rate was not diminished by delayed cord clamping or cord milking, as it was successful in 35 of 36 (97%) such instances. Cases and controls were well matched on demographic and level of illness comparisons. Among cases the hemoglobin generally increased between birth and 12 to 24 h later, but among controls the hemoglobin generally decreased (P<0.05). In the week following birth fewer cases received vasopressors (P<0.01) and erythrocyte transfusions (P<0.001).

CONCLUSION

We judge that it is feasible to collect the initial blood tests of VLBW neonates using otherwise discarded umbilical cord/placental blood, in that this can be accomplished in about 95% of VLBW deliveries. This method, which can be used in addition to either delayed clamping of the umbilical cord or cord milking, results in higher hemoglobin concentrations, less vasopressor use and fewer transfusions in the first week.

Pharmacodynamic analysis of stress erythropoiesis: change in erythropoietin receptor pool size following double phlebotomies in sheep

A feedback receptor regulation model was incorporated into a pharmacodynamic model to describe the stimulation of hemoglobin (Hb) production by endogenous erythropoietin (EPO). The model considers the dynamic changes that take place in the EPO receptor (EPOR) pool under phlebotomy-induced anemia. Using a (125)I-rhEPO tracer the EPO clearance changes are evaluated longitudinally prior to and following phlebotomy-induced anemia indirectly to evaluate changes in the EPOR pool size, which has been shown to be linearly related to the clearance. The proposed model simultaneously captures the general behavior of temporal changes in Hb relative to EPO plasma clearance in five lambs (r = 0.95), while accounting for the confounding variables of phlebotomy and changes in the blood volume in the growing animals. The results indicate that under anemia the EPOR pool size is up-regulated by a factor of nearly two over baseline and that the lowest and highest EPOR pool sizes differ by a factor of approximately four. The kinetic model developed and the data-driven mechanism proposed serves as a starting point for developing an optimal EPO dosing algorithm for the treatment of neonatal anemia.