Hemolysis Risk

Hemolysis Risk Detection

Detection of Hemolysis Risk during Hemodialysis Using the Transonic HDO1 Flow-QC Monitor

Transonic Technical Staff, 2nd edition

I. Introduction

Partial obstructions in the dialysis blood line circuit can cause hemolysis^1-6. The Transonic Flow-QC Hemodialysis Monitor (HD01/HD01Plus) identifies such reductions in flow and thus provides early warning of conditions that could lead to hemolysis. A Transonic clip-on ultrasonic sensor measures actual flow in the dialysis tubing. If an obstruction reduces flow, the Transonic Flow-QC device tracks the actual flow. On the other hand, a dialyzer pump setting sets the revolutions-per-minute ("RPM") of the pump, or the flow that the pump is trying to generate. Comparison of the Transonic flow measurement with the pump setting provides a sensitive indication of tubing obstructions. Whenever flow is restricted, actual flow drops substantially below the pump setting.

As the first observation made after a patient is connected to the Flow-QC monitor, this pump flow check is one component of Transonic Systems' Flow-QC Hemodialysis Adequacy and Access Patency Protocols. When any significant discrepancy between the Transonic Flow-QC measurement and the pump setting exists, a flow restriction in the dialysis circuit should be suspect. If a flow restriction is suspected or identified in one patient, we strongly recommend that all dialysis stations be checked for flow restriction using the following Hemodialysis Pump Flow-Check Protocol. In one to two minutes per patient, a nurse can check that all dialysis pumps deliver the flow for which they are set. This provides an early warning of adverse conditions that can cause hemolysis and under-delivery of dialysis.

II. Hemodialysis Pump Flow-Check Protocol

A. Setting up the HD01/HD01Plus Flow-QC Monitor

Turn on the HD01/HD01Plus Monitor. The laptop computer is not needed for this protocol; it may be left turned off and detached from the monitor. Verify that the HDO1/HD01Plus Monitor is set for the correct tubing set and manufacturer. If an incorrect tubing manufacturer set is selected, a flow error of up to 15% may be introduced. The error could be 5% if the right manufacturer is selected but with the wrong tubing set.

B. Perform the dialysis pump Flow-Check

Apply a small amount of Vaseline® to the tubing and clip the arterial and the venous flow/dilution sensors onto their respective sites.

Turn off ultrafiltration. After a 10-second settling period, verify that the flow indicated on the front panel flow window of the HD01/HD01Plus corresponds to the dialysis pump setting.

C. Consider whether the pump flow reading is acceptable

· It is normal for the pump to over-estimate blood flow somewhat. Pump brand, pump calibration and tubing type all affect the pump RPM-to-flow conversion factor. The hemodialysis Pump Flow-Check Protocol scans for gross deviations. With practice, a trained Flow-QC technician can judge a normal deviation from an abnormal one. Initially, we suggest the following guidelines:

20% discrepancy, immediate attention demanded: If the Transonic flow measurement is _ 20% below the pump's setting (i.e., Flow-QC measurement, < 280 ml/min; pump setting, 350 ml/min), immediately proceed with the Flow Restriction Investigation Steps under III. because of the potentially serious consequences of hemolysis.

10 - 20% discrepancy, moderate concern needed: The Transonic flow measurement is 10% - 20% less than the pump (i.e., Flow-QC measurement, 280-315 ml/min; pump setting, 350 ml/min). Such a drop in flow can result from a moderate flow resistance in the dialysis circuit, a small needle diameter, incorrect needle placement, minor kink in the dialysis tubing or an access flow restriction. The patient may become uremic if the condition persists for several dialysis sessions. The cause of the low flow should be identified and corrected using the complete Hemodialysis Adequacy Flow Study ⁷ or the "Error Analysis Algorithm" of DOQI Guideline 12 of the Clinical Practice Guidelines for Dialysis Adequacy⁸.

10%, normal flow range: The HDO1 indication is within 10% of the pump setting (i.e., Flow-QC measurement, _315 ml/min; pump setting, 350 ml/min). Such differences may well lie within the measurement tolerances of the two methods.

D. Go to the next patient and repeat step B and C, above.

III. Flow Restriction Investigation

Flow-QC indications are complemented by other immediate observations. Because of the serious consequences of hemolysis, we recommend the following:

a) Check pressure readings for any unusual signs. An unusual arterial pressure reading indicates a source of obstruction located between the arterial patient connection and the pump inlet. An unusual venous pressure reading indicates an obstruction after the dialysis filter and the venous patient return. When both pressure readings are normal, the obstruction may be located in the part of the dialysis circuit located between the two pressure chambers.

b) Visually check for kinking of the tubing between arterial drip chamber and pump. The tubing may have collapsed at the point where it enters the pump.

c) Check for ballooning of the tubing between pump, dialyzer and venous drip chamber either visually or by compressing the tubing manually. Because flow will pulsate sharply with the release of each pump roller, an obstruction between pump and dialyzer may create a "hammering" flow sound.

d) Immediately reduce the dialyzer pump setting to a level where pump setting and Flow-QC measurement agree to within 10%. Discontinue dialysis with current equipment if the two readings cannot be brought within 10%.

e) Alert the nephrologist to determine whether to proceed with the dialysis time extended to offset the lower pump flow setting, or to examine further the dialysis configuration to diagnose the cause(s) of flow obstruction.

f) Take a blood sample to screen for hemolysis.

III. References

On Flow Restrictions and Hemolysis

Manufacturing defects in the tubing may occur1 but are rare. Kinking of the arterial line can occur with any tubing. Such kinking causes hemolysis^2,3,4,5,6. Multiple hemolytic reactions may occur before the kink was detected^3,6, and the location of the kink may not cause a pressure alarm6. These reports suggest that the flow restriction may easily go unrecognized. The incidence of hemolysis related to flow restriction could be higher than is clinically recognized.

^1. http://www.fda.gov/medwatch/safety/1998/cobe.htm, "URGENT RECALL: COBE CENTRYSYSTEM 3 BLOOD TUBING SETS."

^2. Seukeran, D., Fletcher, S. Sellars, L., Vestey, J.P. "Sudden deepening of pigmentation during haemodialysis due to severe haemolysis," Br. J. Dermatol. 1997 Dec;137(6):997-999.

^3. Sweet, S.J., McCarthy, S., Steingart, R., Callahan, T., "Hemolytic reactions mechanically induced by kinked hemodialysis lines," Am J. Kidney. Dis., 1996 Feb;27(2):262-266.

^4. Rambausek, M., Wallmeier, K., Schwarzbeck, A., Ritz E., "Abdominal emergency in a dialysis patient: haemolysis from kinking of dialysis tubing," 1995 Nov; 10(11):2141-2143.

^5. Daul, A.E., Schafers, R.F., Wenzel, R.R., Loew, H., Windeck, R., Philipp, T., "Acute hemolysis with subsequent life-threatening pancreatitis in hemodialysis. A complication which is not preventable with current dialysis equipment," 1994 Sep; 23;119(38):1263-1269.

^6. Gault, M.H., Duffet, S., Purchase L., Murphy J., "Hemodialysis intravascular hemolysis and kinked blood lines."

On Pump Flow Monitoring using the Transonic Flow-QC Device

^7. Depner, T.A., Rizwan, S., Stasi, T.A., "Pressure Effects on Roller Pump Blood Flow During Hemodialysis," ASAIO J, Vol. 36, p. M456-459, 1990.

^8. Sands, J., Glidden, D., Jacavage, W., Jones, B., "Difference Between Delivered and Prescribed Blood Flow (Qb) in Hemodialysis," ASAIO J 1996 Sep;42(5):M717-M719.

^9. Shapiro, W., Gurevich, L.,"The Effect of Arterial Needle Size on Dialyzer Blood Flow as Measured by Ultrasound Dilution," 1996 ASN abstract.