Calcium and coagulation.
I read through the full-text of the Biotime "Plasma-like substance" patents (http://www.patents.ibm.com ; enter "biotime" in the search field, look at the scanned images of the patents). The patents were very well prepared and were very readable. The specification part of the patent described the function of the added electrolytes (K+, Ca++, magnesium) to the plasma expander.
Though well-writen, I'm not convinced of the importance of Ca++ addition to hetastarch. I believe that electrolytes and pH are monitored during trauma and massive volume replacement. I had found a description of electrolyte theraphy during volume replacement a few months ago (on my website, and at med.virginia.edu, and it seemed the medical community was aware of these possible issues.
Today, I found a "how-to" on massive blood volume replacement that discussed the potential hypocalcaemia due to dilution (http://www.trauma.org/polytrauma/massive.html). They don't seem to think that hypocalcaemia causes a coagulation problem:
Hypocalcaemia
Each unit of blood contains approximately 3g citrate, which binds ionized calcium. The healthy adult liver will metabolise 3g citrate every 5 minutes. Transfusion at rates higher than one unit every five minutes or impaired liver function may thus lead to citrate toxicity and hypocalcaemia. Hypocalcaemia does not have a clinically apparent effect on coagulation, but patients may exhibit transient tetany and hypotension. Calcium should only be given if there is biochemical, clinical or electrocardiographic evidence of hypocalcaemia.
So, the calcium issue doesn't seem to have been overlooked all these years. Calcium and other electrolytes seem to be monitored during massive volume replacement, and are added if necessary (remember the calcium therapy in the Phase III trial protocols, and the Biotime patents discuss a commercially available K+ injection Synkavite®). Most importantly, hypocalcaemia doesn't seem to cause a coagulation problem.
Steve
btim.dyn.ml.org
I'm hoping that BTIM goes up. |
