Critical Care At The Edge - How I Quack And What Is The Evidence For My Quackery?

According to Wikipedia, “Quackery” is the promotion of unproven or fraudulent medical practices. In equine critical care, unfortunately we have to use ‘unproven’ therapies all the time, as the level of evidence we have supporting any treatment is minimal to nonexistent. Indeed, if we were to use only ‘proven’ treatments in our critically-ill patients with a multi-center randomized clinical trial is the level of proof required, we could treat them only for orthopedic pain, gastric ulcers and intestinal parasites and give lidocaine for ileus and sedate horses with colic. If we were to require properly powered randomized clinical trials, then we could no longer use lidocaine or sedate horses with colic. So we are left with unproven treatments. We base these treatments on our understanding of physiology, pathophysiology and pharmacology, but also largely on previous experience. This dependence on previous experience is essential, but also introduces a dangerous “last three case” bias – if the last three cases went well, the treatment works….! And so we all enter the world of “Quackery”. In this lecture, I will give insights into a couple of the less mainstream treatments I use, where I got them from, and what evidence there is to back up their use.

Cold foals

In 2002, there were two papers published in the New England Journal of Medicine showing much better neurological outcomes when adult human patients were cooled after CPR (1, 2) . This led to exploration whether therapeutic hypothermia might be beneficial in other circumstances, including perinatal asphyxia syndrome(3) . There is now a good body of evidence showing that therapeutic hypothermia is beneficial in human infants with perinatal asphyxia(4) . In addition to improving overall outcome and neurological function, therapeutic hypothermia has been shown to reduce myocardial damage and reduce acute kidney injury in human neonates with perinatal asphyxia. Based on this growing and large body of evidence in human infants, we and others(5, 6)  have been exploring therapeutic hypothermia in foals.

The first step we made was not actively heating foals that present with perinatal asphyxia. This is obviously technically easy to achieve (although it does sometimes require restraint of the well-meaning nurses with their duvets and hot water bottles for the poor cold foals). We have then tried to achieve some degree of whole body or localized cooling. Whole body cooling to the 32-34°C that was described in the original papers is very hard to achieve in a busy veterinary hospital with limited budgets.

In these studies, they gave the cooled patients neuromuscular blockers to stop shivering and mechanically ventilated them. There are also a number of complications of hypothermia including thrombocytopenia, sinus bradycardia, hypokalemia, hypomagnesemia, hypophosphatemia, hyperglycemia(4) , and changes in drug pharmacokinetics.

We have tried a degree of active cooling with ice and have been somewhat successful in lowering the core body temperature (as measured by esophageal thermometer). However, it is hard to get the temperature as low as 34°C. Our current policy is to not actively rewarm any foals with a suspected diagnosis of perinatal asphyxia syndrome. We try to actively cool the most severely affected foals with ice, hot water bottles filled with cold water and intravenous fluids from the fridge. A new paper offers low cost two methods of cooling (gel packs or phase changing materials) that were successful in human infants(7) , which I will try next foal season. The only foals that we actively warm are premature foals and foals undergoing or recovering from anesthesia.

Low molecular weight heparin

This is probably the least “quack” of treatments I am going to discuss. Heparin is a mix of different size molecules. In horses, the larger size fragments are responsible for erythrocyte agglutination. Removing the high molecular weight component results in increased anti-Xa activity, reduced anti-thrombin activity and no erythrocyte agglutination(8) . There are several different low-molecular weight heparins available. For two of these, there is pharmacological data in horses (8-10) and foals(11) .

There is also some efficacy data in horses. A trial in horses with colic showed a lower incidence of thrombophlebitis with dalteparin than with unfractionated heparin(12) . [...]