To overcome the hemorrhagic complications that may occur during extracorporeal circulatory support for post cardiotomy shock patients, a heparinized circuit was introduced into the percutaneous cardiopulmonary support system and decreased systemically administered heparin during bypass. Heparin coated percutaneous cardiopulmonary support with low dose systemic heparinization was instituted in 13 patients (6 men and 7 women, mean age 62.2 ± 8.5 years) who experienced circulatory collapse after cardiac surgery. Of the 13 patients, 9 could not be weaned from cardiopulmonary bypass and 4 had circulatory collapse in the operating room or in the intensive care unit. The duration of support ranged from 1 to 66 hr (mean 27.4 ± 26.7), and the flow rate ranged from 1 to 3 L/min (2.2 ± 0.5). An activated coagulation time of about 150 sec was maintained with or without minimal systematically administered heparin. Of the patients cannulated, 77% (10 of 13) were successfully weaned from percutaneous cardiopulmonary support and 39% (5 to 13) were long-term survivors. The causes of death were sepsis in three, progressive heart failure in three, lower leg ischemia in one, and vital infection in one. From the results of clinical or post mortem examinations, there was no massive bleeding or evidence of thromboembolism in the major organs. From observations made within 12 hr of initiation of percutaneous cardiopulmonary support, there was no significant decrease in the number of platelets, but platelet count had significantly decreased 24 hr after initiation. The authors' experience indicates that heparin coated percutaneous cardiopulmonary support with low dose systemic heparinization is beneficial for circulatory assist in circulatory collapse after cardiac surgery because of its simplicity and antithrombogenicity, which thus avoids the risk of bleeding complications.ASAIO Journal1994; 40:972-976.