Survey of Practice Pattern in Patients With Heparin-Induced Thrombocytopenia Requiring Cardiopulmonary Bypass.

BACKGROUND: Heparin-induced thrombocytopenia (HIT) is an immune-mediated adverse reaction to heparin. Patients undergoing cardiac surgery with cardiopulmonary bypass (CPB) are routinely anticoagulated with heparin before the initiation of bypass. Heparin is contraindicated, however, in patients with acute HIT, and alternatives to routine practice are often used. While guidelines have recently been published addressing this topic 10, there remains variance between institutions in how these cases are treated. Our goal was to better delineate practice trends in the diagnosis and management of HIT patients requiring CPB. METHODS: We surveyed members of the Society of Cardiovascular Anesthesiologists (SCA) and the American Society for Extracorporeal Technology (AmSECT) using an online survey tool. RESULTS: We received 304 completed surveys (5.8% response rate), 75% completed by an anesthesiologist, and 24% by a perfusionist. The majority of respondents used clinical history and/or antibody testing (71% and 63%, respectively) to diagnose HIT. Seventy-five percent of respondents reported using an institutional protocol for HIT-CPB cases. Most respondents (89%) reported having at least 1 case in the last 3 years, with a total case experience of at least 785 cases (785 = the minimum number of cases in each case volume category × the number of respondents choosing that category). The strategy recommended in published guidelines, bivalirudin, was the most commonly reported alternative anticoagulation strategy (75%) used by respondents in HIT cases, with most (83%) using the activated clotting time (ACT) to monitor anticoagulation. CONCLUSIONS: Most responding SCA and AmSECT members reported that their institution used a protocol or guideline for HIT/CPB cases, and most guidelines directed the use of bivalirudin as an alternative anticoagulant. Various other methods such as plasmapheresis are also being used with success in this patient population. Further research, including comparison studies of alternative anticoagulant strategies, is required to elucidate the best approach to these difficult cases.

Implementing a Statistical Model for Protamine Titration: Effects on Coagulation in Cardiac Surgical Patients.

OBJECTIVES: To implement a statistical model for protamine titration. DESIGN: Prospective randomized trial. SETTING: University hospital. PARTICIPANTS: Sixty (n = 30+30) patients scheduled for elective coronary artery bypass surgery were randomly assigned to 2 groups. INTERVENTIONS: Protamine dose calculated according to an algorithm established from a statistical model or to a fixed protamine-heparin dose ratio (1:1). MEASUREMENTS AND MAIN RESULTS: Both groups demonstrated comparable patient demographics and intraoperative data. Coagulation effects were evaluated using rotational thromboelastometry. Using the statistical model reduced (p<0.01) the protamine dose from 426±43 mg to 251±66 mg, followed by significantly (p<0.01) shorter intrinsic clotting time (208±29 seconds versus 244±52 seconds) and stronger clot firmness (p = 0.01), and effects on indices of extrinsic or fibrinogen coagulation pathways were insignificant. Test of residual heparin was negative in all patients after protamine administration, aligned with insignificant (p = 0.27) intergroup heparinase-verified clotting time differences. CONCLUSIONS: The statistical model for protamine titration is clinically feasible and protects the patient from exposure to excessive doses of protamine, with advantageous effects on coagulation as measured using rotational thromboelastometry. Significance regarding clinical outcome is yet to be defined.

Change in heparin potency and effects on the activated clotting time in children undergoing cardiopulmonary bypass.

BACKGROUND: Heparin is the anticoagulant most commonly used for cardiopulmonary bypass (CPB), and the activated clotting time (ACT) is its primary monitor. In October 2009, the Food and Drug Administration changed the United States Pharmacopeia (USP) monograph for unfractionated heparin to incorporate new quality tests and a new potency assay and reference standard. This latter change was anticipated by in vitro tests to reduce heparin potency by 10% in each USP unit dose. After integration of the "new" heparin into our practice, we subjectively noticed less prolongation of the ACT with our routine heparin bolus before the initiation of CPB. We performed this investigation to provide objective evidence of a reduction in the level of anticoagulation achieved with use of the new heparin as assessed by ACT values and to document the occurrence of having an ACT below our institutional threshold before the initiation of CPB. METHODS: A retrospective chart review was performed on all children who underwent CPB at Children's Healthcare of Atlanta between July 1, 2008, and June 30, 2009, before the release of the new heparin ("old heparin" [OH] group) and between June 1, 2010, and May 31, 2011, after complete integration of the new heparin ("new heparin" [NH] group). Baseline ACTs and ACTs after the administration of 400 U/kg of heparin were recorded for both the OH and NH groups. We determined the number of patients in each group having an ACT <480 seconds after the initial heparin bolus but before the initiation of CPB. Additionally, patients were divided into 3 age groups (<1 month, 1 to 12 months, and >1 year) to analyze similar ACT changes. RESULTS: Postheparin ACTs were significantly lower in the NH group than in the OH group. There were significantly more patients having an ACT <480 seconds after the initial heparin bolus in the NH group (OH: 68 of 557 [12.2%] versus NH: 140 of 491 patients [28.5%]; P < 0.0001). The change remained significant when assessed across the age groups. CONCLUSIONS: In this investigation we provide objective evidence that the level of anticoagulation after the initial pre-CPB heparin bolus as assessed by the ACT is significantly less with use of the new heparin. This reduction remained consistent across 3 age groups and was associated with a more frequent occurrence of ACTs below our institutional threshold for the initiation of CPB. Consideration should be given to increasing the initial weight-based heparin dose administered before CPB.