An unsuspected cause of excessive ultrafiltration during maintenance hemodialysis.

Undetected excessive ultrafiltration occurred in a patient on maintenance hemodialysis using a Gambro AK-10 monitor and Ergo 120 A-G blood lines. In spite of alarms present on the hemodialysis monitor, the dialysis staff were not alerted of the failure. The patient had nausea, vomiting, abdominal cramps and hypotension. The monitor was withdrawn from service and subjected to careful technical checks, but no failure could be detected. Thorough investigation of the hemodialysis 'set-up' at the time of the incident revealed a partial obstruction (kinking) to have occurred in the extracorporeal blood circuit where the flexible tubing joined the venous chamber. This had created a very high positive pressure within the dialyzer compartment and excessive ultrafiltration, which the blood circuit pressure monitoring transducer was unable to detect. To prevent kinking of the blood lines, dialysis staff and patients should be instructed to ensure that blood lines lie in smooth curves.