X-Message-Number: 14482
Date: Fri, 15 Sep 2000 20:56:10 -0400
From: mgdarwin <>
Subject: New Cannulation Procedure

Linda Chamberlain writes in part:

>Up until now, we have had no choice but to cannulate the heart in order to
>perfuse the brain through both carotids and vertebrals.  This was the case
>because cannulating the vertebrals seemed impossible (they run through the
>vertebra, thus their name).  Due to (1) the surgical skills of Dr.
>Kanshepolsky, retired neurosurgeon on Alcor's team, and (2) the need to
>produce a more efficient surgical route for the new vitirification
>procedures coming on line (we hope within months) for neuro patients,
Alcor
>has pioneered a new surgical procedure that allows highly skilled surgeons
>to do a four-point cannulation (both carotids and both vertebrals) that
>promises (if the results of the cryoprotection seen with FM-2030 are any
>indication) to give far superior cryoprotection of the brain than we have
>been able to deliver before.  

I feel I should respond to this post for several reasons. First, Jerry Leaf
introduced the median sternotomy approach for neuro as well as whole body
patients for the reasons Linda stated. However, this approach does *not* 
involve cannulating the heart for neuro patients (the left ventricle is a
dead end space which a reaservir for clots!), but rather the aortic arch
(the heart is isolated by a cross-clamp in neuros). Purse string sutures
are required, which some find technically challenging, and unarguably it
takes many patients  to do sternotomies with confidence. The technique used
by Alcor was (I presume, as it is not described) to cannulate the carotids
and the innominate arteries or the basilar arteries, and drain via the
internal jugular veins (or simply allow open drainage of the isolated head
into a pan or reservoir). This requires every bit as much technical
challenge (indeed more) than the sternotomy approach. It also has a serious
drawback: in many people the internal carotids (feeding trhe brain) 
branches from external carotids (feeding the scalp and face) *below the
level of the clavicle.* Or, in other words, in the chest. 

This means the facial tissues will not be well perfused if at all. While
this not a tremendous concern in and of itself since the brain is the
target organfor preservation, it does provide a place for ice to form which
can serve a major source of nucleation if vitrification is used. Ideally,
ice blockers or not, you don't want ice anywhere. Cannulating the external
carotids and interfacing these vessels to the circuit is time consuming
too....

A much better approach which is applicable to almost all patients is to use
the femoral route for cryoprotective perfusion. This may sound very
counterintuitive and wrong. However, when time is of the essence, it is
ideal. Over the past decade there have been  major advances in cannulae
technology which allow long, easily placed (at the time of washout, or
later as applicable)  venous and arterial cannula to be advanced to the
level of the right heart. In neuro patients the arms and legs are simply
tourinqueted off using metal hose clamps and an electric drill. Perfusion
of the visera can be eliminated by inflation of a balloon at the desired
level. If the patient whole body, you simply leave things as they are and
proceed with cryoprotective perfusion. The nice thing about these cannula
are that they are incredibly easy to place compared to the old round-tipped
Bard or Sarns cannula. Because they are extremely thin walled and
completely re-inforced with flatwire they are virtually kink-proof and give
excellent venous drainage even in large patients.

Even with glycerol, which is very viscous, drainge through the Biomedicus
flatwire cannulae is superbt all the wayup  to 7.5M glycerol (as high a
concentration as I've used them) with central venous pressure never
exceeding 5 to 12 mmHg.

The advantage of this approach is that it requires no additional delay or
surgery once the patient arrives *providing* s/he has been cannulated and
washed out in the field. It has cut many hours off of preparation time in
my experience, which includes not only the surgery and cannulation, but
also the prep time required to prepare the patient and the OR for the added
surgery. In patients well stabilized in the field it means incredibly rapid
start of CPA perfusion. Indeed,  I began to *start* CPA loading in the
field during blood washout on local cases(where I was confident of my
arrival time at the facility). This greatly improved blood cleanance and
decreased dehydration from the cryoprotectant (= more cryoprotectant
*inside* the cells, where you want it)..

In cases where there has been no field washout or stabilization, the median
sternotomy approach is still likely to be the best. This is so because it
allows fine-bore baloon tipped angiography cannulae to be advanced up the
carotids as high as possible, the balloons are inflated, and the large
vessels perfused retrograde with drainage out of both the open right heart
(or superior vena cava) and the aortic arch. This maneuver is invaluable
since it clears the large vessels of the vasculature of clots and
aggregates of red blood cells (due to cold agglutination). Perfusion can
then be started on the arterial side with the right heart left open and any
remaining clots disloged by perfusate flow, or,  removed with long curved
forceps by reach up into the superior vena cava.  After a short period of
such low flow, low pressure perfusion when  the venous effluent becomes
clear, it then possible to REVERSE the direction of flow and wash-out clots
and RBC aggregates from the arterial circulation by actively perfusing the
*venous vessels.* You never get it all, but you get a lot of it.
Streptokinase is also active at 0 to 10 Celsius and should be used during
these manuevers in patients who have extensive postmortem clotting.

Once the arterial drainage has cleared, you can then proceed to perfuse as
usual usiing the arterial (aortic) side to introduce perfusate and the
venous side to drain. The important lesson here is that you need to
back-flush debris filled vessels by getting as proximal to the brain as
possible. Before I left active work in cryonics, I found that in relevant
animal models that by extending the burr holes to a cranial window and
opening the superior saggital sinus for drainage (which sits midline along
the brain) resulted in even better drainage and much less debris (clots,
etc.) being forced into and occluding the smaller veins which branch off
this large venous reservoir and ultimately drain into the jugular veins and
superior vena cava.   

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