Introduction of a switch that can reverse blood flow direction on-line during hemodialysis.

In several circumstances in hemodialysis, the regular direction of blood flow has to be reversed or changed, such as in access dysfunction or insufficient blood flow being obtained through the arterial port, as well as to measure actual access blood flow in fistulas or grafts by using the formula Qa = Qb((1-R)/R), where R represents recirculation in the reversed line configuration. We invented a disposable switch device made from standard blood line tubing that can be introduced into the dialysis circuit and allows for on-line reversal of lines, without needing to manually disconnect and reconnect tubing or interrupt the hemodialysis procedure. Over a period of eight months, 16 patients (8 arteriovenous fistula, 8 PTFE) underwent 193 hemodialysis sessions with the switch in place. Circuit pressures, pump, and actual blood flows measured with ultrasound dilution were monitored before and after reversing the lines. Switching was accomplished within 1-2 seconds. Arterial circuit (r = 0.99), venous circuit pressures (r = 0.6), and actual pump flow (364 +/- 56 vs. 350 +/- 57 ml/min; r = 0.73) correlated very well preswitching and postswitching (p < 0.0001). Dialysis circuit flow measured with an ultrasound dilution technique decreased from 364 +/- 56 (230-480) ml/min preswitching to 350 +/- 57 (220-490) ml/min postswitching (p < 0.001). No difficulties or complications were observed. This switch device is a useful addition to the technology of hemodialysis in that it greatly facilitates the procedure of reversing the lines in an extracorporeal circuit while not significantly interfering with circuit pressures and connections.

Abnormal electrical stimulus of an intra-aortic balloon pump with concurrent support with continuous veno-venous hemodialysis.

Malfunction of electronic medical support apparatus utilized in the ICU usually causes system failure. We report several occurrences of a potentially dangerous interaction between a continuous veno-venous hemodialysis (CVVHD) system and an intra-aortic balloon pump (IABP) counterpulsation device in four patients requiring both systems. The patients had acute renal failure in the face of multi-organ failure and were dependent upon the balloon pump for pressure support. Electrical interference created by the roller pump action of the CVVHD system was identified by the balloon pump as cardiac in origin, and it responded by inflation and deflation. As the blood pump rate was reduced, the interference reduced to the point of complete cessation when the blood pump was shut down. Whereas one patient transiently had a significant drop of mean arterial pressure (from 70 +/- 4 to 40 +/- 2 mm Hg) the other observed occurrences had no clinically significant sequelae. Electrocardiogram (ECG) tracings identified the abnormal stimulus and systematic review identified as potential sources for the creation of this interference static electricity buildup, piezoelectric properties of the polyvinyl chloride tubing, and, possibly but less likely, radiofrequency interference. A newer generation ECG cable and advanced cardiac rhythm recognition software (CardioSync) have been introduced with the Datascope System 98, and the ECG interference, although still occasionally present, does not cause erratic inflation and deflation of the intra-aortic balloon pump. Interference between different electrical support systems may occur, and we suggest that the systems be tested for compatibility before combined use and that older equipment be more rigorously tested for potential clinically significant interference.

Ultrafiltration method for measuring vascular access flow rates during hemodialysis.

BACKGROUND: The vascular access blood flow rate (QA) has been shown to be an important predictor of vascular access failure; therefore, the routine measurement of QA may prove to be a useful clinical method of vascular access assessment. METHODS: We have developed a new ultrafiltration (UF) method for determining QA during HD from changes in arterial hematocrit (H) after abrupt changes in the UF rate with the dialysis blood lines in the normal (DeltaHn) and reverse (DeltaHr) configurations. This method accounts for cardiopulmonary recirculation and requires neither intravenous saline injections nor accurate knowledge of the dialyzer blood flow rate. Clinical studies were conducted in 65 chronic HD patients from three different dialysis programs to compare QA determined by the UF method with that determined by saline dilution using an ultrasound flow sensor. RESULTS: Arterial H increased (P<0.0001) after abrupt increases in the UF rate when the lines were in the normal and reverse configurations. An increase in the UF rate from the minimum setting to 1.8 liter/hr resulted in a DeltaHn of 0.3+/-0.2 (mean +/- SD) H units and a DeltaHr of 1.6+/-1.0 H units. Q(A) values determined by the UF method (1050+/-460 ml/min) were 16+/-25% higher (P<0.001) than those determined by saline dilution (950+/-440 ml/min); the calculated QA values by the UF and saline dilution methods correlated highly with each other (R = 0.92, P<0.0001). The average coefficient of variation for duplicate measurements of QA determined by the UF method in a subset of these patients (N = 21) was approximately 10% when assessed in either the same dialysis session or consecutive sessions. CONCLUSIONS: The results from this study show that changes in arterial H after abrupt changes in the UF rate can be used to assess Q(A).

The use of iron in patients on chronic dialysis: mistake and misconceptions.

Anemia is the most common hematologic abnormality in patients with chronic renal failure. The reasons for anemia in chronic renal failure are many and include erythropoietin and iron deficiencies, inflammation, infection, aluminum toxicity, and hyperparathyroidism. Iron deficiency alone affects more than 50% of patients on dialysis, and the estimated iron loss for these patients is 1.5 to 3 grams per year. The use of erythropoietin has also uncovered iron deficiency in a multitude of patients. Iron and erythropoietin supplementation has often restored normal or near-normal levels of hematocrit in these patients and has therefore improved some of the symptoms classically connected with chronic renal failure, such as fatigue, cold intolerance, and mental sluggishness, among others. Resistance to erythropoietin is frequently observed in the maintenance care for dialysis patients, and the most common reason is iron deficiency. It is important to understand the physiology of renal anemia, erythropoiesis and iron metabolism in order to avoid mistakes and misconceptions in the management of iron in chronic dialysis patients. In this article, we review several mistakes, misconceptions, practices, and guidelines in iron supplementation therapy. We also review the physiology of anemia in renal disease and the importance of erythropoietin and iron in causing anemia and discuss recent Dialysis Outcomes Quality Initiative (DOQI) guidelines on the topic.