[HSF] Type I Dissection

Tea Acuff tacuff at swbell.net
Sat Feb 10 19:45:27 EST 2007 

Glad to have your input, Tom. Can't blame you for a sabbatical. 
tea


----- Original Message ----
From: "tdmartin2000 at aol.com" <tdmartin2000 at aol.com>
To: OpenHeart-L at lists.hsforum.com
Sent: Saturday, February 10, 2007 4:47:38 PM
Subject: Re: [HSF] Type I Dissection


I know I haven't been contribution to the forum much lately and I apologize. On the issue of what is the best way to do arch aneurysms I think one choice is not always best for all. We still use porfound hypothermia for most arch cases (18 degrees), even the hemiarch cases where the circ arrest times are typically short (less than 15 minutes). Certainly for complex cases we opt for 18. Antegrade perfusion certainly makes sense from a brain standpoint in most pts, however it is not a panacea as you are only perfusing the one side in most cses. We have learned from our stent graft experience that there are a significant number of pts that are dependent on the left vertebral for posterior circulation. We also know that even though you may not see catastrophic brain injury with shorter circ arrest at moderate hypothermia, the temporal lobe is very susceptible to ishemia and this may lead to subtle neuropsych problems including short term memory loss.
Without going into a long diatribe I can say we evaluate each patient and each of us in our group decides which therapy to use on an individual basis. I still favor 18 degrees and retrograde perfusion at 300 to 500cc in elephant trunks, dissections and redos, 21 to 24 degrees (preferably with electrocerebral silence) with hemiarches, and selective cerebral perfusion with balloon tipped cannulas in Jehovah Witness pts at 28 degrees.

Tom Martin
U of Florida
Gainesville


-----Original Message-----
From: anianyanwu at hotmail.com
To: OpenHeart-L at lists.hsforum.com
Sent: Sat, 10 Feb 2007 11:07 AM
Subject: Re: [HSF] Type I Dissection


Hal

I agree no one advocates 25 degrees for HCA - at my institution the standard is 
16 degrees. I think our practice is however based more on fear (of catastrophic 
neurological injury) rather than physiology.

>From a scientific viewpoint though there is no reason why depth of hypothermia 
should be uniform for all HCA cases. From the work of Griepp, at 25 C there is 
at least 15 minutes of safe arrest, and from animal studies, this may be as long 
as 25 minutes. So if one expects the anastomosis to be completed in 10 minutes, 
what is the rationale for cooling to 16 degrees for a bentall with open 
anastomosis, seeking a safe time of 30 to 40 minutes for a procedure likely to 
take 10 to 15 minutes? Hypothermia of course is not without risk, so why do we 
take additional risk for no benefit?

I have personally done two cases with HCA at 25 degrees, though neither were 
planned pre-operatively. For a simple repair where the surgeon feels he can 
accomplish repair in less than 15 minutes there is probably no need for deep 
hypothermia. Certainly for surgeons like Martin and Svensson who routinely 
accomplish anastomosis in under 10 minutes, there is no scientific rationale to 
cool below 25 degrees. However complex arch is another story and that is where 
DHCA or ACP has benefits. 

Considering though that you would already be at 25 degrees for your planned 
bentall hemiarch (with intention of ACP), there would be minimal value in 
complicating the process by adding ACP, as at that temperature, and for the 
expected short duration of HCA, there will be little or no benefit to adding ACP 
if you will be arrested for less than 15 minutes. ACP is not without risk (due 
to cannulation or perfusion of head vessels) and I do not think the (minimal, if 
any) benefit will justify such a risk in your case. ACP always remains a back up 
so if at 25 degrees and arrested the procedure seems more complicated than 
anticipated simply clamp the innominate, start axillary perfusion and insert LCA 
catheter and start perfusing left too. I see this as akin to intermittent 
fibrillatory arrest for CABG - provided you can do an anastomosis in less than 
15 minutes you will see not see permanent myocardial injury - if for some reason 
(eg endarterectomy) the procedure will be prolonged, you simply administer 
cardioplegia or blood in root or take of the clamp for a few minutes.

Ani
  ----- Original Message ----- 
  From: Hgrmd at aol.com<mailto:Hgrmd at aol.com> 
  To: OpenHeart-L at lists.hsforum.com<mailto:OpenHeart-L at lists.hsforum.com> 
  Sent: Friday, February 09, 2007 9:49 PM
  Subject: Re: [HSF] Type I Dissection


  Ani,
    I don't know of anyone, including your predecessor Dr. Griepp, who  
  advocates doing an open distal anastomosis at 25 C without some sort of  
selective 
  perfusion.  
  Hal
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