Objectives: To determine whether the tissue plasminogen activator, alteplase, is more effective than heparin in preventing blood clots developing in children's haemodialysis central lines between dialysis sessions.
Design: A prospective double-blind, within-patient multiperiod cross-over controlled trial of instilling a "lock" of either heparin 5000 U/ml or alteplase 1 mg/ml into the central lines of two children haemodialysed twice weekly, and seven dialysed thrice weekly, over 10 weeks.
Setting: A UK paediatric nephrology unit.
Main outcome measures: Weight of blood clot aspirated from the line at the start of the next dialysis session.
Results: The odds of a clot forming was 2.4 times greater with heparin than alteplase (95% CI 1.4 to 4.0; p = 0.001), and when present they were 1.9 times heavier (31 vs 15 mg; 95% CI 1.5 to 2.4; p<0.0005). There was no effect of inter-dialytic interval. One child required an alteplase infusion to clear a blocked line following a heparin lock. We subsequently changed our routine locks from heparin to alteplase. Comparing the year before and after that change, the incidence of blocked lines requiring an alteplase or urokinase infusion fell from 2.7 to 1.2 per child (p<0.03), and the need for surgical replacements from 0.7 to nil (p<0.02).
Conclusion: Alteplase is significantly more effective than heparin in preventing clot formation in central haemodialysis lines. This reduces morbidity and improves preservation of central venous access. It is more expensive, though relatively economic if packaged into syringes and stored frozen until needed, but reduces the costs of unblocking or replacing clotted lines.