Converting hemodialysis patients from intravenous paricalcitol to intravenous doxercalciferol - a dose equivalency and titration study.

AIMS: Doxercalciferol and paricalcitol are used to treat hyperparathyroidism in chronic kidney disease. This study was conducted to define equivalent dose requirements to convert patients from intravenous paricalcitol to intravenous doxercalciferol. METHODS: Following a 4-week baseline period using a fixed dose of paricalcitol, 42 adult hemodialysis subjects were assigned to receive a fixed dose of doxercalciferol for 4 weeks using a conversion factor of either 50 or 65% of the prior paricalcitol dose. During a 12-week titration period the doxercalciferol dose was adjusted to optimize iPTH levels into the range of 150 - 300 pg/ml. Annual costs to achieve equivalent iPTH control were calculated for both vitamin D analogs. RESULTS: During the doxercalciferol fixed-dose period, the average dose of doxercalciferol was 2.1 +/- 1.3 microg and 3.1 +/- 1.8 microg in the 50 and 65% dose conversion groups, respectively. During this period mean iPTH in the 50% dose conversion group increased by 24 pg/ml (p = 0.017). During the dose titration period, doxercalciferol was increased to bring iPTH within the target range. Calcium control was maintained with both conversion factors, while slightly better phosphorus control was seen in the 65% dose conversion group. Annualized treatment cost for doxercalciferol was 28% less expensive per patient than paricalcitol. CONCLUSION: Patients can be managed safely and effectively with conversion and dose titration from paricalcitol to doxercalciferol. Both conversion strategies maintained iPTH at clinically satisfactory levels. Furthermore, doxercalciferol therapy resulted in drug acquisition cost-savings.

Simplified measurement of intra-access pressure.

The measurement of intra-access pressure (P[IA]) normalized by mean arterial BP (MAP) helps detect venous outlet stenosis and correlates with access blood flow. However, general use of P(IA)/MAP is limited by time and special equipment costs. Bernoulli's equation relates differences between P(IA) (recorded by an external transducer as PT) and the venous drip chamber pressure, PDC; at zero flow, the difference in height (deltaH) between the measuring sites and fluid density determines the pressure deltaPH = P(IA) - P(DC) Therefore, P(DC) and PT measurements were correlated at six different dialysis units, each using one of three different dialysis delivery systems machines. Both dynamic (i.e., with blood flow) and static pressures were measured. Changes in mean BP, zero calibration errors, and hydrostatic height between the transducer and drip chamber accounted for 90% of the variance in P(DC), with deltaPH = -1.6 + 0.74 deltaH (r = 0.88, P < 0.001). The major determinants of static P(IA)/MAP were access type and venous outflow abnormalities. In grafts, flow averaged 555 +/- 45 ml/min for P(IA)/MAP > 0.5 and 1229 +/- 112 ml/min for P(IA)/MAP < 0.5. DeltaPH varied from 9.4 to 17.4 mmHg among the six centers and was related to deltaH between the drip chamber and the armrest of the dialysis chair. Concordance between values of P(IA)/MAP calculated from PT and from P(DC) + deltaPH was excellent. It is concluded that static P(DC) measurements corrected by an appropriate deltaPH can be used to prospectively monitor hemodialysis access grafts for stenosis.

Simplified measurement of intra-access pressure.

Normalized intra-access pressure (PIA), expressed as the access pressure/systemic blood pressure, detects venous outlet stenosis and correlates with access blood flow. General use of (PIA) is limited by time, special equipment needs, and cost. We therefore correlated pressure measurements from the venous drip chamber (PDC of Fresenius H-machines and from an external transducer, P tau, for blood flows (BFR) of 0 to 400-500 ml/min. Measurements were conducted 2-3 weeks apart in a cohort of 33 patients. PDC = -21 + 1.28 P tau; PDC = P tau = 75 mmHg at BFR = 146 ml/min. The major determinant of P tau at BFR = 0 was access type and venous outflow problems. The difference between P tau and PDC (delta = offset) was 17 +/- 1 mmHg (range, 2-43); delta correlated with the height difference between the two sites. Differences in systemic blood pressure, zero calibration, and hydrostatic pressure accounted for 90% of the variance between replicate measurements of PDC. Detection of outlet stenosis was compared by using PIA calculated from P tau and from PDC + 17. Only three of 66 measurements using the latter produced misclassification, and never on replicate measurements. P tau and PDC measurements in 62 additional patients showed a persistent offset of 17 mmHg. The authors conclude that PDC at BFR = 0 can be used to monitor prospectively prosthetic bridge grafts for stenosis as long as the offset for a particular dialysis machine is determined.