Extracorporeal blood purification has made significant advances in veterinary patients over the recent years with a rising number of hospitals providing intermittent haemodialysis, continuous renal replacement therapy, or even apheresis. Novel advances in human ICUs have led to the development of novel extracorporeal blood purification techniques that may find application in veterinary emergency and critical care.

Extracorporeal Potassium Adsorption

Hyperkalaemia is a common problem in both veterinary and human acute care. Medical management (with insulin, dextrose, bicarbonate, beta agonists, and calcium) along with treatment of the underlying disease, whenever possible, is often sufficient to reduce plasma potassium concentrations below life-threatening levels. Unfortunately, a subset of patients are refractory to medical therapy alone and may require extracorporeal blood purification in the form of haemodialysis or continuous renal replacement therapy until hyperkalaemia resolution. Those therapies require a technical platform along with possible large volume of replacement fluids in addition to the need for trained personnel. Those limitations have stimulated interest in potassium adsorption technologies. While there is no commercially available product at the moment, research in swine has shown that circulation of ultrafiltrate through cartridges containing potassium adsorbing beads could control plasma potassium concentrations in both anephric and crush injury swine models without the need for replacement fluids. Those studies showed that the beads had no significant effect on other electrolytes, platelet counts, or resuscitation requirements. This intervention does not control concomitant uraemia and other disorders associated with acute kidney injury (other electrolyte imbalances, azotaemia, fluid overload). There is still a need to circulate the blood in an extracorporeal circuit but this circuit could be simpler to manage than that of haemodialysis or continuous renal replacement therapy.

Extracorporeal Membrane Adsorption

Sepsis is a serious condition, which is often associated with a high rate of morbidity and mortality in veterinary medicine. A subgroup of patients sometimes progresses to septic shock; these patients then suffer from severe hypotension despite adequate fluid resuscitation which requires the use of vasopressors. Despite these intensive resuscitation efforts, these patients still have a minimal survival rate. Novel cartridges have been developed to non-specifically adsorb cytokines and chemokines in a concentration-driven manner. Molecules ranging from 5 to 60 kDa are bound to the cartridge membrane.

The cartridges have also been used to remove myoglobin following severe rhabdomyolysis. The cartridge may also find application in cases of intoxication. Evidence is building in human ICU patients with a wide range of diseases.

Extracorporeal Membrane Oxygenation

In recent years there has been an increased interest in extracorporeal membrane oxygenation (ECMO) not only for intensive care patients but also for those presenting to the emergency room with highly compromised cardiovascular and/or pulmonary functions. There have also been reports of in-field initiation of ECMO, thus underlying the ability to implement this resource-intense intervention even in unfavourable conditions. ECMO has also been used in patients in cardiac arrest, an intervention termed extracorporeal cardiopulmonary resuscitation (ECPR).

Patients undergoing ECMO therapy are placed on a by-pass circuit where blood is circulated through a membrane acting as an artificial lung, which removes carbon dioxide and enriches the blood in oxygen. This requires a large, well-coordinated team along with costly materials at the moment. ECMO can be VA or VV, whereby blood is pumped from a large vein into a large artery or vein, respectively. VA ECMO supports both the lung and heart and VV ECMO is used in patients with respiratory failure but sufficient cardiovascular function.

References

1.  Hoareau GL, Beyer CA, Wilson C, Kashtan H, Wishy A, Grayson JK, Walker L, Ross JD, Stewart IJ. Extracorporeal potassium binding for the management of hyperkalemia in an anephric model of crush injury. J Trauma Acute Care Surg. 2019.

2.  Hoareau GL, Kashtan H, Walker L, Beyer C, Wishy A, Grayson JK, Ross JD, Stewart IJ. A novel perfusion system for damage control of hyperkalemia in swine. Shock.

3.  Schädler D, Porzelius C, Jörres A, Marx G, Meier-Hellmann A, Putensen C, Quintel M, Spies C, Engel C, Weiler N,Kuhlmann M. A multicenter randomized controlled study of an extracorporeal cytokine hemoadsorption device in septic patients. Crit Care. 2013;17(Suppl 2):62.

4.  Peng ZY, Carter MJ, Kellum JA. Effects of hemoadsorption on cytokine removal and short-term survival in septic rats. Crit Care Med. 2008;36(5):1573–1577.

5.  Kogelmann K, Jarczak D, Scheller M, Drüner M. Hemoadsorption by CytoSorb in septic patients: a case series. Crit Care. 2017;21:74.

6.  Lamhaut L, Hutin A, Puymirat E, Jouan J, Raphalen JH, Jouffroy R, Jaffry M, Dagron C, An K, Dumas F, Marijon E, Bougouin W, Tourtier JP, Baud F, Jouven X, Danchin N, Spaulding C, Carli P. A pre-hospital extracorporeal cardio pulmonary resuscitation (ECPR) strategy for treatment of refractory out hospital cardiac arrest: an observational study and propensity analysis. Resuscitation. 2017;117:109–117.

7.  Tonna JE, Selzman CH, Mallin MP, Smith BR, Youngquist ST, Koliopoulou A, Welt F, Stoddard KD, Nirula R, Barton R, Fair JF, Fang JC, McKellar S. Development and implementation of a comprehensive, multidisciplinary emergency department extracorporeal membrane oxygenation program. Ann Emerg Med. 2017;70(1):32–40.