Myoglobin clearance and removal during continuous venovenous hemofiltration

Myoglobin has a relatively high molecular weight of 17,000 Da and is poorly cleared by dialysis (diffusion). However, elimination of myoglobin might b e enhanced by an epuration modality based on convection for solute clearanc es. We present a single case of myoglobin-induced renal failure (peak creat ine kinase level: 313,500 IU/1) treated by continuous venovenous hemofiltra tion (CVVH). Our purpose was to evaluate the efficiency of such a modality using an ultrafiltration rate of 2 to 3 l/h for myoglobin removal and clear ance. The hemofilter was a 0.9 m(2) polyacrylonitrile (AN69) membrane Multi flow-100 (Hospal-Gambro, St-Leonard, Canada) and the blood now rate was mai ntained at 150 ml/min by an AK-10 pump (Hospal-Gambro, St-Leonard, Canada). The ultrafiltration bag was placed 60 cm below the hemofilter and was free of pump control or suction device. Serum myoglobin concentration was 92,00 0 mu g/l at CVVH initiation and dropped to 28,600 mu g/l after 18 h of the continuous modality. The mean sieving coefficient for myoglobin was 0.6 dur ing the first 9 h of therapy and this decreased to 0.4 during the following 7 h. Mean clearance of myoglobin was 22 ml/min, decreasing to 14 ml/min du ring corresponding periods, while the mean ultrafiltration rates were relat ively stable at 2,153 +/- 148 ml/h and 2,074 +/- 85 ml/h, respectively. In contrast to myoglobin, the sieving coefficeint for urea, creatinine, and ph osphorus remained stable at 1.0 during the first 16 h of CVVH. More than 70 0 mg of myoglobin were removed by CVVH during the entire treatment. In conc lusion, considerable amounts of myoglobin can be removed by an extracorpore al modality allowing important convective fluxes and middle molecule cleara nces, such as CVVH at a rate of 2 to 3 l/h using an AN69 hemofilter. If myo globin clearance had been maintained at 22 ml/min, 32 1 of serum would have been cleared per day. However, the sieving coefficient of myoglobin decrea sed over time, probably as a consequence of protein coating and/ or blood c lotting of the hemofilter. Whereas myoglobin can be removed by CVVH, it rem ains unknown at this point if such a modality, applied early, can alter or shorten the course of myoglobinuric acute renal failure.