HIT and CABG

For the praticing anesthesia providers ...

I'm wondering if any of you have had experience with HIT patients having a CABG. Mainly, what else you may have used instead of heparin for the pump. I've heard of using Hirudin or abciximab but haven't actually seen any cases. Would love to hear from experienced CRNAs!

Well - no experienced CRNAs have responded to this great question (they're all busy debating the whole MD/CRNA issue or whether a CRNA with a doctorate should call themselves doctor). I hope you're willing to settle for an experienced AA instead....

At our institution the HIT protocol used to be Heparin and Aggrastat together. We now use bivalirudin in these patients with reasonable success. They clearly bleed more until it wears off so you have to be ready for that.

For the praticing anesthesia providers ...

I'm wondering if any of you have had experience with HIT patients having a CABG. Mainly, what else you may have used instead of heparin for the pump. I've heard of using Hirudin or abciximab but haven't actually seen any cases. Would love to hear from experienced CRNAs!

I am not a CRNA either but TICU Nurse and our protocol is bivalirudin as well, though some will also use argatroban.

There are several options for performing CABG in the setting of HIT. Heparin can be used if the case is elective and sufficient time has passed to significantly reduce the level of circulating antibodies (usually >2-3 months). The level of antibody response to heparin including a heparin induced platelet aggregation study and a platelet factor 4 assay should be used to confirm before re-exposure to heparin. Obviously the heparin exposure in this setting should be kept to a minimum. This is the least favorable option in this setting. Direct thrombin inhibitors (DTI's) are probably the best option. Clinical trials are ongoing using DTI's (eg. bivalirudin) in CABG (although not specifically in the setting of CABG & HIT). Once these studies are finished, better data about the efficacy, safety, and dosing of DTI's for CABG will be known. While there is anecdotal evidence and case reports supporting the use of glycoprotein IIb/IIIa inhibitors in this setting with and without concommitant heparin, direct thrombin inhibitors are still a better option. Important caveats include 1) making sure there are dosing adjustments for renal or liver dysfunction - depending on the elimination/clearance of the particular DTI 2) the lack of utility of ACT or PTT with bivalirudin and 3) the increased likelihood of bleeding with these agents and 4) lack of a specific reversal agent like there is with heparin (ie. protamine). If the case is elective, then regardless of what agent is used, it is still reasonable to delay the surgery although not completely necessary. Before using any of these options, both the anesthesiologist/CRNA and surgeon need to be familiar with all of the issues, and it can be very helpful to discuss these issues with people who have already used these agents.

Well - no experienced CRNAs have responded to this great question (they're all busy debating the whole MD/CRNA issue or whether a CRNA with a doctorate should call themselves doctor). I hope you're willing to settle for an experienced AA instead....

At our institution the HIT protocol used to be Heparin and Aggrastat together. We now use bivalirudin in these patients with reasonable success. They clearly bleed more until it wears off so you have to be ready for that.

Thanks for your response georgia. And yes, I agree, the same debates over and over repeating the same points (or non-points) gets a bit old. I appreciate anyones experienced observations and opinions.

- Kat

There are several options for performing CABG in the setting of HIT. Heparin can be used if the case is elective and sufficient time has passed to significantly reduce the level of circulating antibodies (usually >2-3 months). The level of antibody response to heparin including a heparin induced platelet aggregation study and a platelet factor 4 assay should be used to confirm before re-exposure to heparin. Obviously the heparin exposure in this setting should be kept to a minimum. This is the least favorable option in this setting. Direct thrombin inhibitors (DTI's) are probably the best option. Clinical trials are ongoing using DTI's (eg. bivalirudin) in CABG (although not specifically in the setting of CABG & HIT). Once these studies are finished, better data about the efficacy, safety, and dosing of DTI's for CABG will be known. While there is anecdotal evidence and case reports supporting the use of glycoprotein IIb/IIIa inhibitors in this setting with and without concommitant heparin, direct thrombin inhibitors are still a better option. Important caveats include 1) making sure there are dosing adjustments for renal or liver dysfunction - depending on the elimination/clearance of the particular DTI 2) the lack of utility of ACT or PTT with bivalirudin and 3) the increased likelihood of bleeding with these agents and 4) lack of a specific reversal agent like there is with heparin (ie. protamine). If the case is elective, then regardless of what agent is used, it is still reasonable to delay the surgery although not completely necessary. Before using any of these options, both the anesthesiologist/CRNA and surgeon need to be familiar with all of the issues, and it can be very helpful to discuss these issues with people who have already used these agents.

In your opinion/experience, does the treatment differ if the patient is diagnosed with HIT type I or II? Also, (for those patients with low-levels of heparin antibodies) if they receive heparin on pump, have you seen any significant difference with post-op drainage/take back for bleeding/blood product transfusion need?

Thanks for your post - it was very informative.

- Kat

Type I HIT is often called heparin associated thrombocytopenia. It is not immune mediated, happens more commonly than Type II HIT, and is thought to be due to platelet clumping or sequestration. It does not have the thrombotic sequelae of Type II HIT and does not need treatment.

The concern for Type II HIT is more thrombotic risk rather than increased bleeding. We have seen some cases where pts had HIT undiagnosed at the time of CABG but found afterwards when the thrombocytopenia manifested. Some of these pts presented with recurrent ischemia and were found to have thrombosed off all of their grafts.

Hope this helps.

Hope this helps.

Yes - it does. Thanks for the insight.