Thursday, July 7, 2016

Blood Medicine, Part 4: Real advances in blood technology

The ABCs of emergency medicine are changing.
I’m sorry, but this is going to be a complex discussion. Anything having to do with emergency care of your body would have to be. I'll make it as clear as I can. Before we’re done, you may find yourself making a list to carry in your wallet: TXA, FastClot, Perftec, Perflubron, Hemopure.
Anyway, the ABCs… Emergency responders have always been taught: Airway, Breathing, Circulation, in that order. But the decade-long war in the Middle East, horrific as it was, resulted in enormous advances in emergency medicine. Medics have learned that circulation – keeping your blood inside your body – is just as important, if not more important, than keeping you breathing. Here’s how their thinking is changing:

  • 1. Tourniquets.
For nearly a century medics were taught to avoid tourniquets. A WWI British field surgeon, Major Blackwood, called the tourniquet an ‘instrument of the devil’ after so many soldiers lost limbs because of them.
Blackwood was dealing with soldiers whose limbs had in some cases been tied off for days before further treatment. In most parts of the world today, treatment is only hours - or even minutes - away. Today’s medics know that a tourniquet can be safely left in place for up to 2 hours.
It isn’t about the tourniquet redesign; it’s the change in priorities. If a person has a large gash in their leg, for example, and they're not breathing right, previous thinking has been to FIRST get them breathing, then turn attention to the gash in the leg. But the medics in Afghanistan learned that during the several minutes it takes to get someone breathing properly they could bleed out.
“Tourniquets rapidly placed by the provider immediately, saved lives. The provider can then turn their attention to airway management, interventions to improve breathing… as well as IV placement and fluid administration.”
  • 2. Coagulants
Battlefield medics for the past 10 years have carried products like QuikClot, a finely ground mineral powder that helps wounds stop bleeding. More recent products feature gauze bandages impregnated with the mineral. While not too many EMTs carry this product yet, as more medics come back from the war with experience using QuikClot, its use in emergencies is growing. More recently, another coagulant bandage has hit the market. Called FastClot, this new invention is made by spinning dextran into fine threads like cotton candy, then attaching the body’s own clotting tool, fibrinogen, to the mesh.
The medic quoted above says:
“These specialized products have not been required often. However, these agents can be lifesaving, particularly in difficult-to-manage wounds, such as those of the groin or axilla (armpit). They provide effective hemorrhage control for wounds that aren’t amenable to other methods of hemorrhage control and which might otherwise be fatal.”
  • 3. Tranexamic acid (TXA)
In a previous column we mentioned TXA being used for a woman whose uterus wouldn't stop bleeding after delivery. In two recent studies – one of them in combat – TXA was shown to significantly improve the chances of survival of one out of seven patients. In some ERs it has become part of the routine to give TXA to all severely bleeding patients, or those with potential internal bleeding, if possible within 3 hours after injury.

Surgeons have begun administering TXA in many of their bloodiest operations – some heart surgeons even reportedly pouring it randomly into the chest cavity before closing. Hospitals in some third world countries have likewise emptied a syringe of the stuff onto a gauze bandage and used it to stop otherwise unstoppable bleeding.

An Australian study in 2014 saw paramedics being equipped with TXA to be administered to accident victims.

  • 4. Permissive hypotension
In WWII, doctor Henry K. Beecher proposed that a relatively low systolic blood pressure of 85 was sufficient for a patient awaiting surgery. During the Vietnam era, with the ready availability of volume expanders medics began pumping their patients with bags of fluids to get blood pressure back up to acceptable numbers.
But it turns out Beecher was right. What the Vietnam medics were inadvertently doing was disturbing the process of clot formation.

Back to the battlefield medic:
“The body’s natural response after trauma is to minimize hemorrhage by forming a fragile clot on the bleeding vessel. Excessive IV fluid administration can actually result in increased bleeding from the injured vessel… In a patient with penetrating trauma who is maintaining a systolic blood pressure at or above the 80–90 range or who has a radial pulse, IV access should be obtained with a saline lock but no IV fluid administered.”
He suggests that if the systolic BP falls below 80–90, or if the patient loses the radial pulse, then fluid should be given, just a quarter to a half unit at a time, and then the patient be reassessed.

  • 5. Artificial blood
As we saw in Part 2 of this series, blood is a marvelous creation. Coming up with a fluid that picks up oxygen from the lungs, releases it in the tissues, and doesn’t poison the body in the process, is a very tricky task.

PBOCs. Most research into alternative oxygen carriers has focused on PFCs (perfluorocarbon), such as the defunct product Fluosol. Initially approved by the FDA, its approval was removed when studies showed significant side effects, including fatalities. Current research into PFC-based blood substitutes is focusing on deleting the side effects. Some PFC-based oxygen carrier products in clinical trials, or already approved for human use (but not necessarily as a blood substitute) include Perftoran (also known as Perftec), Oxycyte, Perflubron, Liquivent, and others.
HBOC (hemoglobin based oxygen carrier) describes another direction research is taking. It generally involves starting with a bovine-derived, modified hemoglobin molecule, attaching it to a fluid and using that as a human oxygen carrier. so far, few of these products has passed clinical trials. Sanguinate has been used in a few emergency trials and saved some lives without major side effects. Hemopure and Polyheme have been approved for human use in some places but are still being reviewed in the U.S. Some HBOCs have been given guarded approval for use in a few extreme situations by Jehovah’s Witness patients, so far with mostly positive results.

 Hemerythrin is neither a PFC nor an HBOC. It is a protein that transports oxygen in sea worms. Several companies are working with this protein to develop a blood substitute. One, Hemarina, has developed a product for keeping graft tissues and organs oxygenated for longer periods of time between harvesting and implantation.
This page has a fairly up-to-date list of the status of several blood substitutes.

Why all this work to change the transfusion landscape? Even though donated blood is “free,” it’s expensive to test, handle, store, and refrigerate; It has a short shelf life, even refrigerated; After storage it is an unreliable oxygen carrier; It carries antigens unique to the donor that can kill the recipient; It transmits disease; And study after study has shown that blood transfusion recipients, assuming they live, invariably leave the hospital with additional heart, respiratory, immune and other complications.

And that’s in a country where blood is given freely by well-meaning donors. In many parts of the globe, people don’t line up to give blood out of the goodness of their heart. They must be paid – or forced – to give blood. There are critical shortages, and the blood thus collected is even more problematic than in Europe and America. This is why countries like China and Thailand are throwing their financial resources into finding an acceptable blood substitute.
I’ve managed to get through four columns about blood with barely a mention of the Bible. Does the Bible have anything to do with blood? That will be the subject of the next part of this series. 

Someone actually asked me about contributing to my Paypal account to help fund my writing. You don’t need to do that, just buy one of my books!

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