126 J . M . Fenske et al .: J Extra Corpor Technol 2024 , 56 , 125 – 127
for anticoagulation monitoring . Baseline activated clotting time ( ACT ) was notably normal , at 117 s . Institution protocols call for 100 mg / kg of the antifibrinolytic tranexamic acid ( maximum dose of 750 mg ) in the cardiopulmonary bypass prime , and 100 mg / kg of tranexamic acid ( maximum dose of 750 mg ) given intravascularly by anesthesia upon bypass initiation , however , after a preoperative team discussion neither of the antifibrinolytic doses were administered to further inhibit post-operative fibrinolysis in the patient .
Sternotomy was made , and upon the surgeon ’ s request , a loading dose of 2100 units of heparin ( 300 u / kg per protocol ) was administered intravenously by anesthesia . An additional dose of 2000 units of heparin was administered in the cardiopulmonary bypass prime , per institution protocol , as well as the standard dosing of albumin , sodium bicarbonate , solumedrol , mannitol , and cefazolin . Packed red blood cells ( 125 mL ) were also added to the prime to reduce hemodilution upon bypass initiation . Bypass was initiated once the ACT was confirmed to be elevated from baseline and above the target of 400 s , and the bypass run of 65 min was uneventful . Heparin metabolism throughout the pump run was as expected , with ACT results declining from 819 s to 522 s , without additional heparin administration . Heparin was reversed with 24 milligrams of protamine post-bypass ( a ratio of 0.59 mg protamine : 100 mg total heparin ). Post-protamine ACT was 120 s . Results of the ACT throughout the case are displayed in Figure 1 .
Hematocrit trend , lactate trend , and blood gas results throughout the bypass run were unremarkable . The patient was transferred to the CTICU uneventfully . There were no notable postoperative events .
Comment
Safe implementation of cardiopulmonary bypass is dependent on the ability to monitor , and therefore ensure appropriate anticoagulation . Factor XII deficiency compromises this monitoring as it is one of the contact factors that respond to the activator present in most ACT tests : Celite and / or kaolin . Celite and kaolin are both widely accepted and used in anticoagulation monitoring , however , kaolin is more reliable for anticoagulation monitoring in patients on the serine protease inhibitor aprotinin [ 13 ].
The Hemochron Signature Elite is used to monitor anticoagulation at Children ’ s Hospital Los Angeles ; the Hemochron ACT + cartridges use a mixture of silica , kaolin , and phospholipids as activators ( Hemochron manual ). With this variety of activators , ACT results are not prolonged as they are with standard Celite or kaolin-only activation . As suggested by the intraoperative ACT results , the Hemochron Signature Elite and ACT + cartridges provided reliable ACT values that were expected before heparin , after heparin , during bypass , and after protamine administration . At the time of writing , the authors have only been able to find one other publication of successful anticoagulation monitoring within factor XII deficiency , using the Hemochron Jr . device and ACT + cartridges [ 11 ].
There have been other methods suggested for management of the factor XII deficient patients . One such method is to monitor the anti-Xa concentration of the patient ’ s blood .
Figure 1 . Trend of intraoperative activated clotting time results as provided by the Hemochron .
Unfortunately , the time required to complete this test is impractical for the application of cardiopulmonary bypass . Monitoring of heparin concentration , as opposed to ACT , has also been suggested using a device such as the Medtronic HMS [ 14 ]. However , it must be stated that adequate heparin concentration does not always ensure adequate anticoagulation , such as in the case of antithrombin III deficiency or heparin resistance . Another publication relied on speculation after observing a prolonged ( though unreliable ) ACT after heparin administration [ 13 , 14 ]. A more involved method could be to increase factor XII levels through the administration of fresh frozen plasma to increase the factor XII content in the patient . This was discussed as an alternative method if the Hemochron did not prove to be reliable . Gerhardt et al . published a case report demonstrating the titration curve of fresh frozen plasma necessary for increasing factor XII and resulting ACTs within expected ranges . However , it is demonstrated that the subsequent increase in factor XII after FFP administration is short-term [ 3 , 15 ].
Further , it is critical to consider the use of antifibrinolytics in cardiac surgery with factor XII deficient patients . Factor XII deficiency impairs fibrinolysis , as activated factor XII usually activates pre-kallikrein to kallikrein furthering fibrinolysis . Without the normal degree of fibrinolysis , dosing an antifibrinolytic should be reconsidered [ 4 ]. If available , viscoelastic testing such as thromboelastography ( TEG ) or rotational thromboelastometry ( ROTEM ) should be considered for the factor XII deficient patient , as these tests provide timely insight into clot initiation , clot formation , and fibrinolysis . A 2022 publication by Stelmach et al . found factor XII deficient patients ( n = 20 ) to have markedly higher coagulation times and clot formation times , though no marked difference in maximum clot formation or maximum lysis [ 16 ] At the time of this case , there was no access to viscoelastic technology for patient blood sample analysis .
With adequate preparation and knowledge , anticoagulation can be managed adequately for cardiopulmonary bypass to be reliably performed . There have been suggestions within the literature regarding strategies to monitor anticoagulation in factor XII deficient patients , however , the authors find that the safest and most reliable method is the use of an array of