Razionale

Acetate-Free Biofiltration (AFB) is known for its better hemodynamic stability than bicarbonate dialysis (BD). In the latter the small quantity of acetate in the bath can lead to cardiovascular unstability. The acetate is also the source of carbon dioxide (CO₂) amounting to 100 mmHg¹. Since high CO₂ dialysance, the blood out the filter has high pCO₂^2,3,4 that patient's lung must remove.  In the AFB, lacking the acetate, the only source of CO₂ is that derived by the bicarbonate itself.  Differences of overall CO₂ load between BD and AFB are unknown.

Casistica e Metodi

Gas analysis of blood withdrawn from venous line of extracorporeal circulation during BD and subsequently during AFB in 16 stable out-patients was performed. A two-tailed Student’s t test was used to compare set of data.

Risultati

The mean value of pCO₂ ±SD in AFB is lower than in BD (43.5±4.4 and 59.4±4.5 mmHg p<0.0001), with similar HCO₃ values (29.1±3.4 and 30.3±1.8 mmol/L, p=0.23). It is worth noting that pCO₂ difference exceeds 30%. Corollary of such evidence  is the lower pH in BD than in AFB (7.32±0.02 and 7.43±0.03; p<0,0001). As shown in figure, shifting from BD to AFB yields a decrease of pCO₂ in blood coming back to the patient.

Conclusioni

The reduced CO₂ load from the extracorporeal circulation could play some role on cardiovascular stability in AFB. The latter could be the elective technique in patients unable to remove CO₂ overload dialysis-induced.

References:

1) Golper TA et al: Hemodialysis: core curriculum 2014. Am J Kidney Dis 2014;63(1):153-163

2) Sombolos KI et al: pO2 and pCO2 increment in post-dialyzer blood: the role of dialysate. Artif Organs 2005;29:892-8

3)Symreng T et al: Ventilatory and metabolic changes during high efficiency hemodialysis. Kidney Int 1992;41:1064-9

4)Marano M: Gas analysis in bicarbonate dialysis. G Ital Nefrol. 2013 Sep-Oct;30(5)