Cost-effectiveness analysis compared four treatments of end-stage renal disease in Brazil: continuous ambulatory peritoneal dialysis (CAPD), in-center hemodialysis (HD), cadaver donor transplantation (CD-Tx), and living related donor transplantation (LR-Tx). After 2 years, the costs per year of survival were CAPD, $12,134; HD, $10,065; CD-Tx, $6,978; and LR-Tx, $3,022. The HD cost was lower than CAPD partially because of the reuse of hemodialyzers in Brazil. Although less cost-effective, both dialysis treatments yielded more years of survival after 2 years. This analysis reveals a trade-off between cost per year of survival and years of survival.

During hemodialysis a decrease in pulmonary ventilation has been reported. The elimination of CO₂ across the dialyzer has been suggested as the cause of the pulmonary hypoventilation. Our purpose was to analyze the factors that could have influenced the pulmonary ventilation of 7 patients with chronic renal failure during hemodialysis, performed against an acetate dialysate with constant addition of CO₂, bubbling into the dialysis bath. In spite of the large volume of CO₂ mainly as bicarbonate, eliminated across the dialyzer there was no significant decrease of ventilation. The values of pH in the venous line were extremely low and the values of P_vCO₂ were artificially maintained around 35.0 mm Hg. Thus, the total CO₂ delivered to the lungs, but mainly the levels of pH and PCO₂ in the venous line play an important role in the control of pulmonary ventilation of these patients.

The elimination of CO₂ across the dialyzer has been reported as the cause of the pulmonary hypoventilation during hemodialysis. There are some evidences that the venous line blood composition could influence the central venous blood and this one the pulmonary ventilation. Our purpose was to analyze (1) the influence of the changes in composition of the venous line blood on the central venous blood and (2) the possible role of the central venous blood composition on the pulmonary ventilation of 10 chronic renal failure patients during hemodialysis performed twice in the same patients in two different conditions: acetate dialysate without (condition I) and with (condition II) constant addition of 100% CO₂ bubbling into the dialysis bath. During condition I the venous line blood pH was kept in a normal range, and the PCO₂ was low, whereas during condition II the pH was very low and the PCO₂ extremely high. The patients during condition I decreased their pulmonary ventilation and lost CO₂ across the dialyzer as the central venous blood pH and HCO^-₃ increased, and PCO₂ did not change. The same patients during condition II increased their pulmonary ventilation and absorbed CO₂ across the dialyser as the central venous blood pH decreased and PCO₂ increased. Thus, the venous line blood has influence on the central venous blood composition, and this plays a role on the control of pulmonary ventilation of these patients.

In order to analyze the effect of intermittent negative pressure ventilation (NPV) on renal function, we studied 20 healthy male volunteers (mean age 29 +/- 4.1 years). NPV was performed with an "Emerson Chest Respirator Pump", adjusted to a breathing frequency of 10 respirations per minute, with inspiratory time/total respiratory time ratio of 0.4 and negative pressure of 25 cmH2O. The experimental protocol was carried out in two phases of two hours each--spontaneous breathing and NPV breathing. At the end of each phase, urine volume of the whole period was collected as well as venous blood sample for biochemical determinations. During NPV there was significant increase (P < 0.05) in urine flow rate (1.43 +/- 0.81 to 2.76 +/- 1.95 ml/min) as well as in natriuresis (258 +/- 201 to 389 +/- 175 mcEq/min), kaliuresis (61 +/- 45 to 98 +/- 49 mcEq/min), fractional sodium excretion (1.38 +/- 0.88 to (1.96 +/- 0.98%), osmolar clearance (3.13 +/- 1.82 to 4.32 +/- 1.24 ml/min) and pH (7.37 +/- 0.04 to 7.41 +/- 0.07) with unchanged creatinine and free water clearances. We concluded that NPV increases urine flow rate, kaliuresis and natriuresis but the data we have do not allow us to explain the mechanisms underlying such a phenomenon.

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