Membrane‐based therapeutic plasma exchange in dogs: Prescription, anticoagulation, and metabolic response

Background Therapeutic plasma exchange (TPE) is used increasingly in small animals to remove circulating large molecular products such as antibodies, pathogenic proteins, and protein‐bound toxins. Specific, efficient, and safe protocols need to be developed. Hypothesis/Objectives To describe the technique of membrane‐based TPE, the resulting physiological and metabolic changes, and to define an adequate regional citrate anticoagulation protocol. Animals Thirty‐four dogs treated with TPE (2011‐2017). Methods Retrospective review of all TPE treatments performed at the Vetsuisse Faculty, University of Bern, identified through a search of the institutional database for extracorporeal treatments. Results Sixty‐four treatments were performed, resulting in 1.0 plasma volume exchange (range, 0.4‐1.1). Replacement fluids included fresh frozen plasma (12%‐100% volume), colloids (0%‐52%), human albumin (0%‐41%), and saline (0%‐70%). Anticoagulation was performed with regional citrate (n = 24), systemic heparinization (n = 2), or combined (n = 38). Main relevant laboratory changes included a 24.7% decrease in total proteins (interquartile range, 16.7‐31.4; P  < .001), 53% in fibrinogen (−30 to 63; P = .009), 36% in bilirubin (13‐43, P = .02), 9.0% in urea (0.7‐15.7; P  < .001), and 4.5% in creatinine (−6.6 to 10.6; P = .006). Citrate accumulation was evidenced in all dogs, more pronounced in those with renal but not with hepatic impairment. Maximal tolerable citrate rates were estimated as 5.5 and 9.0 μmol/kg/min for treatments in dogs with and without renal impairment, respectively. Complications were observed in 22 treatments (34%) and were fatal in 2 dogs. Conclusions and Clinical Importance Therapeutic plasma exchange causes metabolic and biochemical alterations. Understanding these effects makes possible to anticipate most complications and to improve safety of the procedure.