Effect of Two-Hour Daily Hemodialysis and Sham Dialysis on Breath Isoprene Exhalation

Background

Isoprene, a volatile hydrocarbon produced by the human organism, is currently being extensively investigated because the mechanisms underlying its endogenous origin are unknown and because experiments suggest it is toxic and cancerogenous. Previous reports of increases in breath isoprene concentrations during 4-hour, thrice-weekly hemodialysis, but not during continuous ambulatorial peritoneal dialysis, prompted us to assess the behavior of isoprene in another dialytic modality, i.e., short daily hemodialysis (short DHD). Furthermore, in order to determine whether removal of solutes and/or contact of blood with the dialytic membrane influenced the metabolism of isoprene, we performed a sham short hemodialysis session in a subgroup of 8 patients (sham short HD), i.e., with blood flowing through a dialyzer but without dialysate and ultrafiltration.

Methods

The present study evaluates the effects of a two-hour short DHD and a two-hour session of sham HD on isoprene breath levels, as determined by gas chromatography before, during and after sessions. Parallel analyses of ambient air and monitoring of blood pressure and heart rate were performed.

Results

Both short DHD and sham DHD induced an increase in breath isoprene exhalation in all patients without being associated with significant hemodynamic variations.

Conclusion

These findings suggest that the increase in breath isoprene after a session of hemodialysis is neither a reaction to mevalonate depletion nor to metabolic variations induced by the depurative effect, because these changes do not occur during sham HD. It is not related to hemodynamic changes because none were observed in this experimental model. The isoprene increase seems to be of metabolic origin and appears to be connected in some way with the extracorporeal circuit. These interesting findings provide a further impulse to study the biosynthetic pathways involved and to investigate the medical and biological significance of isoprene in humans. (Int J Artif Organs 2007; 30: 583–8)

Onset, time course, and persistence of increased haemodialysis-induced breath isoprene emission

Recent findings of increased isoprene emission in the exhaled breath of patients undergoing haemodialysis and experimental evidence of the potential toxic and cancerogenic effects of isoprene hydrocarbon led us to assess how long haemodialysis patients are exposed to how much isoprene after a single haemodialysis session. Patients with end-stage renal failure on regular 4-hour (from 08.00 to 12.00 h) maintenance haemodialysis three times weekly were monitored. The breath isoprene content was analyzed by gas chromatography. Intrapatient evaluations were performed by collecting samples before, during, and immediately after the haemodialysis session, during the following hours, and on the following nondialysis day. The breath isoprene content increased in all patients. Isoprene overproduction showing a biphasic pattern was first detected soon after the dialysis session ended. These data show that haemodialyzed patients seem to be consistently exposed to high endogenous isoprene concentrations. The mechanisms and implications of this endogenous isoprene overproduction need to be elucidated with regard to the mevalonic pathway and in the physiopathological setting of the uraemia-dialysis syndrome.