Cardiac arrest after hypertonic citrate anticoagulation for chronic hemodialysis. The use of regional citrate anticoagulation as an alternative to standard therapy in hemodialysis patients at risk for bleeding complications has been well described. Recently, a method using hypertonic citrate has been reported as being safe and efficacious, and having several advantages over the usual techniques. Two patients who suffered cardiac arrests after dialysis using hypertonic citrate are discussed. Both received anticoagulation as described in the literature, although the citrate infusion rate was lower than recommended. Electrocardiograms obtained during the first such session showed no change in the Q-Tc interval with initiation of the infusion in either patient. Both were noted to have cardiac arrest within 5 minutes of discontinuation of dialysis, without warning symptoms, following the second and fifteenth treatments, respectively. The initial rhythm of ventricular fibrillation did not respond to standard advanced cardiac life support therapy, and the patients were not successfully resuscitated until they received intravenous calcium. The authors postulate that the loss of positive calcium flux from the dialysate, in conjunction with circulating unmetabolized citrate, caused an electrolyte imbalance leading to the potentially fatal arrhythmia. Caution is recommended in using this method of regional anticoagulation. 