Cardiovascular Journal of Africa: Vol 24 No 6 (July 2013) - page 22

CARDIOVASCULAR JOURNAL OF AFRICA • Vol 24, No 6, July 2013 216 AFRICA
and neurological complications, and decreases the duration of
ischaemia.
In the present study, we were not able to show that the
single-clamping technique was superior to the partial-clamping
technique during coronary artery bypass operations, in terms of
frequency of neurological damage. We found that the mortality
rate was the same in both groups.
The single-clamp technique may not be sufficient to minimise
neurological complications by itself. Sequential anastomosis
may be preferred in order to decrease the number of proximal
anastomoses in patients with plaques in the aorta. As the
sequential-anastomosis technique is not used routinely in our
clinic, this was not included among the parameters evaluated in
the present study. Also, replacement of the ascending aorta under
hypothermic circulatory arrest, which was recommended by
Kouchokos et al.17 for patients with severely calcific aortas, may
be considered as an alternative method. The authors reported a
mortality rate of 4.3%, without neurological complications.
Revascularisation with the ‘no-touch’ technique or ‘off-pump’
coronary bypass grafting, which were described by Mills et
al.,18 may be applied to patients, especially those who have
atherosclerotic plaques in their ascending aortas. Coronary
bypass surgery with the beating heart technique may be an
alternative method, if proximal anastomoses are used for a region
outside the ascending aorta. Intra-operative ultrasonographic
evaluation is recommended to detect the presence of plaques
in the ascending aorta.13 This may be the best method for
the prevention of neurological complications due to possible
embolisations from the aorta. However, in our hospital, we
could not use this method because of practical problems in the
operating rooms.
Advanced age, carotid artery disease, aortic atherosclerosis,
previous cerebrovascular disease, prolonged cardiopulmonary
bypass, and peri-operative hypotension are reported as risk factors
for stroke development after CABG.2,19 We detected prolonged
cross-clamp duration, diabetes, hypercholesterolaemia, left
ventricular dysfunction (EF < 40%), atrial fibrillation, peripheral
arterial disease, and peri-operative hypotension as risk factors
for stroke (Table 3). Partial clamping used during proximal
anastomosis was not found to be a risk factor. Our observation
of our patients was that the neurological damages seen after
coronary artery bypass surgery were due to multiple factors;
they cannot be decreased solely by means of the single-clamp
technique.
Neurological problems may also occur during placement
and replacement of total aortic cross clamp, aortic cannulation
or aortic ‘punch’ application, as well as partial clamp use.
Also, there are reports of embolidation even during manual
examination of the aorta.16,18,20 It is known that thrombus material
that was already present in the left atrium or ventricle may also
cause embolism. Each of these factors may cause neurological
problems.
At our clinic, we routinely created controlled hypotension for
a few seconds with ECC support before replacement of an aortic
clamp in patients undergoing CABG. During those few seconds,
the surgeon evaluated the aorta carefully. Different techniques
other than the routine could be used in patients in whom the
presence of aortic plaques was detected. However, patients
with aortic plaques were not included in the current study. It
is probably for this reason that we found non-superiority of the
single-clamping technique in comparison with partial clamping,
in terms of stroke development.
Grocott et al. 21 found that the S100β protein was a good
marker for showing cerebral damage and that the level of this
protein was highest during aortic cannulation in coronary bypass
surgery. These authors also detected that the serum levels of the
S100β protein were lower during aortic cross-clamp placement
or replacement. It was stressed in this study that cannulation was
more important in terms of post-operative stroke risk than clamp
placement on the aorta.
We believe that metabolic investigations such as protein C,
protein S, and anti-thrombin deficiency should be done, as well
as determining S100β protein levels for post-CABG stroke and
cerebral damage. We could not investigate these parameters,
given that the present study was retrospective. Also, the lack
of echocardiographic examination of the aorta and the lack of
a prospective design were limiting factors of the present study.
Conclusion
We believe that a surgical team may utilise either of the two
techniques studied here, after the surgeon has evaluated the aorta
at low aortic pressure and concluded that plaques are not present.
We feel that both methods may be used safely in routine coronary
artery bypass grafting.
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