Volatile Alkanes and Increased Concentrations of Isoprene in Exhaled Air during Hemodialysis

Abstract

In this study we examined breath volatile hydrocarbon concentrations in exhaled air of hemodialysis patients. We assessed both C₂–C₅ alkanes – among them ethane and pentane the production of which in man is essentially due to the action free radicals exert on polyunsaturated fatty acids – and isoprene, an unsaturated hydrocarbon the biosynthesis and biological effects of which are the subject of controversy and mounting interest. Twenty patients were studied. Evaluation was performed intrapatient in the breath of patients with chronic renal failure, before and after dialysis (20 patients) and, in the same cases, during hemodialytic treatment (10 patients). Breath concentrations of these volatile hydrocarbons, determined before dialysis, were not different from those of normal subjects. Dialysis did not modify the levels of the C₂–C₅ saturated hydrocarbons ethane, propane, butane and pentane. Instead, there was a marked increase in isoprene in all patients (basal values rose by a mean of 270%). Since isoprene was not present in the fluids or filters used for dialysis and there were only traces in the ambient air, the isoprene must have been produced endogenously during hemodialysis. As no situation has previously been reported to increase endogenous production of isoprene in humans, patients in hemodialysis offer a unique opportunity to investigate in depth the medical, biological and toxicological aspects of isoprene.

Onset, Time Course, and Persistence of Increased Haemodialysis-Induced Breath Isoprene Emission

“…Breath collection and gas chromatography analysis of volatile hydrocarbons were carried out as described elsewhere [10]. Briefly, a predetermined quantity of breath, collected in Tedlar ® bags (SKC, Eighty Four, Pa., USA), was adsorbed in tubes filled with pretreated charcoal.…”

“…In a previous study performed to evaluate breath hydrocarbon concentrations in different clinical and experimental settings, we have recently observed a marked increase in endogenous isoprene exhalation in all haemodialyzed patients [10]. …”

Acute Exercise May Exacerbate Oxidative Stress Response in Hemodialysis Patients

“…A profound imbalance between oxidants and antioxidants has been suggested in uremic patients on maintenance [4, 5] while several studies implicate ROS and/or reduced antioxidant capacity in the development of complications associated with chronic kidney disease [4, 5]. It has been well documented that even a single session of exercise significantly increases lipid peroxides and decreases antioxidants [6, 7]. Oxidative stress development in HD patients has been attributed mainly to neutrophil activation during dialysis as a result of interaction of blood with the dialysis membrane and endotoxin-contaminated dialysate, iron overload, alterations in erythrocyte pentose-phosphate shunt activity, abundance of advanced glycation end products, high homocysteine levels, intradialytic cytokine activation, a pro-oxidant effect from the uremic condition, and reduced antioxidant capacity [8, 9].…”

Gases as Uremic Toxins: Is There Something in the Air?

“…34 In human beings, current data indicate an increase of isoprene in the breath during a hemodialysis session. 35,36 Thus, it remains elusive whether the increase of isoprene in the rat model is a consequence of the injury of the ischemic renal tissue or if it indeed reflects the retention of uremic toxins. Accordingly, it remains unclear whether the increased concentration of isoprene may underlie the increase of hydroxyacetone in the exhaled breath of subjects with renal failure.…”