The human body truly is a wondrous thing. Molecules made from one organ, tissue or cell can have far reaching effects as the products take their journey throughout the body. As a medical student I remember well the many lectures on the kidney. How one organ could control elimination of waste, regulate salt and water metabolism, blood pressure and RBC counts was truly thought provoking. At the turn of the century (last one and not 1999 – 2000) Medical school was about a year in length and as the pool of knowledge grew was expanded into the three or four year program that now exists. Where will we be in another 100 years as new findings add to the ever growing volume of data that we need to process? A good example of the hidden duties of a molecule is erythropoetin (Epo) the same one responsible from stimulating red blood cell production.
Double Duty Molecule
In saying that I am simplifying it as there are likely many processes this one hormone influences in the body but I would like to focus on its potential role in neuroprotection. In 1999 Bernaudin Et al performed an animal study in mice to test this hypothesis. In this elegant study, strokes were induced in mice and the amount of Epo and Epo receptors measured in injured tissues. Levels of both increased in the following way “endothelial cells (1 day), microglia/macrophage-like cells (3 days), and reactive astrocytes (7 days after occlusion)”. To test the hypothesis that the tissues were trying to protect themselves the authors then administered recombinant human Epo (rhEpo) to mice prior to inducing stroke and the injury was clearly reduced. This established Epo as a potential neuroprotectant. Other animal studies then followed demonstrating similar findings.
A Human Trial
When you think about hypoxic ischemic encephalopathy (HIE) you can’t help but think of whole body cooling. The evidence is pretty clear at this point that cooling in this setting reduces the combined outcome of death or neurodevelopmental disability at 18 months with a number needed to treat of 7. The risk reduction is about 25% compared to not those not cooled so in other words there is room to improve. Roughly 30-40% of infants who are cooled with moderate to severe HIE will still have this outome which leaves room for improvement. This was the motivation behind a trial called High-Dose Erythropoietin and Hypothermia for Hypoxic-Ischemic Encephalopathy: A Phase II Trial. This was a small trial comparing 50 patients (24 treated with rhEpo and cooling to 26 given placebo) who were treated with 1000 U of rEpo on days 1,2,3,5 and 7. Primary outcome was neurodevelopment at 12 months assessed by the Alberta Infant Motor Scale (AIMS)and Warner Initial Developmental Evaluation. A significant improvement in a subset of mobility on the latter was found and a significant difference in the AIMS overall. An additional finding giving support for a difference was that blinded reviews of MRI scans demonstrated a singificant improvement in brain tissue in those who received rhEPO. One curious finding in this study was that the mean timing of administration of rhEPO was 16.5 hours of life. Knowing that the benefit of cooling is best when done before 6 hours of age one can only wonder what impact earlier administration of a neuroprotective agent might have. This suggests that the addition of rEPO to cooling has additional impact but of course being a small study further research is needed to corroborate these findings.
The Next Step
This past week Malla et al published an interesting paper to add to the pool of knowledge in this area; Erythropoietin monotherapy in perinatal asphyxia with moderate to severe encephalopathy: a randomized placebo-controlled trial. This study was done from the perspective of asking if rhEPO by itself in resource poor settings without access to cooling in and of itself could make a difference in outcome for patients with HIE. This was a larger study with 100 Hundred term neonates (37 weeks or greater) with moderate or severe HIE. Fifty were randomized by random permuted block algorithm to receive either rhEPO 500 U kg− 1 per dose IV on alternate days for a total of five doses with the first dose given by 6 h of age (treatment group) or 2 ml of normal saline (50 neonates) similarly for a total of five doses (placebo group) in a double-blind study. The primary outcome was combined end point of death or moderate or severe disability at mean age of 19 months and the results of this and other important outcomes are shown below.
|Death/disability (mod/severe HIE)||40%||70%||0.003|
|Death/disability (mod HIE only)||21%||61%||0.004|
|Seizures treatment at 19 months||19%||43%||0.03|
To say that these results are impressive is an understatement. The results are on par with those of cooling’s effect on reduction of injury and improvement in outcome. When looking at the primary outcome alone the result in dramatic when put in perspective of looking at number needed to treat which is 4! This is significant and I can’t help but wonder if the impact of this medication is at least in part related to starting the dosing within the same window of effectiveness of therapeutic hypothermia. Importantly there were no adverse effects noted in the study and given that rhEpo has been used to treat anemia of prematurity in many studies and not found to be associated with any significant side effects I would say this is a fairly safe therapy to use in this setting.
I find this puts us in a challenging position. The academic purists out there will call for larger and well designed studies to test the combination of rhEPO and cooling both initiated within 6 hours of age. While it takes years to get these results might we be missing an opportunity to enhance our outcomes with this combination that is right in front of us. The medication in question other than raising your RBC count has little if any side effects especially when given for such a short duration and by itself and possibly with cooling increases the rate of neuroprotection already. I don’t know about you but I at least will be bringing this forward as a question for my team. The fundamental question is “can we afford to wait?”