CARDIOVASCULAR JOURNAL OF AFRICA • Volume 25, No 2, March/April 2014
AFRICA
71
starts. With activation of the complement system, C3 is diverted
to its subunits, C3a and C3b, and therefore the amount of C3 is
rapidly decreased. The decrease is expected to be more severe if
inflammation is severe.
6
In this regard, time-dependent changes
in C3 levels showed more inflammatory activity in group I. This
may indicate that topical cooling caused more inflammation and
therefore more injury to cardiac myocytes.
Similarly, time-dependent changes in TNF-
α
levels were
significant (
p
<
0.001). TNF-
α
, which is an early reactive
cytokine of the inflammatory response, is released during the
activation of the inflammatory period. During cardiac surgery,
this would occur with ACC.
7
In our study, TNF-
α
was rapidly
increased with ACC and decreased to almost baseline levels
in group I, whereas it showed quite a stable trend in group II
(Fig. 2). This result supports the hypothesis of Nikas
et al
., who
showed that local hypothermia caused more inflammation and
local injury.
4
Defibrillation requirement
Most authors accept that spontaneous restoration of sinus
rhythm after aortic declamping is an important indicator of
myocardial function.
8,9
Lichenstein
et al
. reported that the rate of
spontaneous restoration of sinus rhythm was higher in patients
without topical cooling.
9
In our study, this rate was significantly
higher in patients in group II than in those in group I (80 vs 32%,
p
<
0.01).
The need for defibrillation was as follows: in group I, eight
patients (32%) needed it once, seven patients (28%) needed it
twice, and two (8%) needed it three or more times, whereas in
group II, four patients (16%) needed it once and only one patient
needed it twice. Therefore, if the requirement for defibrillation
were an indicator for myocardial function, group I had poor
myocardial function at an early phase of aortic declamping. We
believe these results are related to topical cooling because this
was the only variable that differed between the groups.
Incidence of dysrhythmias
Atrial fibrillation (AF) is the most common type of arrhythmia
seen after cardiac surgery (32.3%).
10
The systemic inflammatory
response plays an important role in the pathogenesis of
these arrhythmias, and several risk factors such as older age,
pre-operative history of AF, chronic obstructive pulmonary
disease (COPD), long intubation time, long ACC time, renal
insufficiency, and high amounts of drainage and transfusion
were found to be responsible for postoperative AF.
10-14
In our study, there was a statistically significant difference
between the two groups for AF rates (six patients in group I vs
one patient in group II,
p
<
0.05). The patients were randomised
homogenously into the groups according to these risk factors.
Therefore, based on these results, we consider that there was
a direct relationship between topical cooling and postoperative
AF.
IABP requirement
In the literature, there are not many studies on the association
between IABP and topical myocardial cooling. In one study,
which compared the effects of cardiac hypothermic and
normothermic techniques, Calafiore
et al.
reported that there
was no statistically significant difference between the type of
technique used and the necessity for IABP.
15
In our study, IABP was required in four patients (16%) in
group I, while none of the patients required it in group II (
p
<
0.05). Although these results were statistically significant, we
are not certain of the relationship between these two factors
because indications for IABP are standardised worldwide in
daily practice. However, it is usually dependent on the surgeon’s
decision. We believe there was no definite association between
necessity for IABP treatment and topical myocardial cooling.
Diaphragm pathology
There was a statistically significant difference in diaphragm
paralysis between the groups in our study (
n
=
7, 28% vs
n
=
0,
0%,
p
<
0.01). We believe the main pathogenesis was phrenic
nerve injury. The phrenic nerve originates from the anterior
horn of C3–C6, runs down the posteromedial part of the internal
mammarian artery at the entrance of the thoracic cavity, spreads
to the lateral surface of the pericardium and then reaches the
diaphragm muscles.
The main artery of this nerve, which may be damaged during
LIMA harvesting due to its proximity to the internal mammarian
artery, is the pericardiophrenic artery.
16
This nerve can be
damaged during LIMA harvesting and/or partial pericardiotomy,
which is performed for tunnelling to the LIMA pedicle.
Furthermore the damage may occur because of cold application.
This type of injury primarily depends on nerve demyelisation
and is usually reversible in one year.
4
Phrenic nerve injury after
cardiac surgery is reported at 2–17%.
17
In another study, Nikas
et al
. compared diaphragm paralysis
in 505 patients undergoing cardiac surgery with and without
topical hypothermia, and they found similar result to those in
our study. In this study, 25% of patients with topical hypothermia
and 2% of those without topical hypothermia had diaphragm
paralysis (
p
<
0.0001).
4
In our study, the first intercostal artery was devascularised
with a haemostatic clip and without cauterisation for maximal
care of the phrenic nerve during LIMA harvesting. Partial
pericardiotomy was performed carefully on 11 patients in
group I and 13 patients in group II (
p
>
0.05). These patients
were compared in each group for an association between
possible phrenic nerve injury and partial pericardiotomy. There
were no correlations between pericardiotomy, LIMA harvesting
and phrenic nerve injury. Therefore cold injury seemed to
be responsible for phrenic nerve injury and thus diaphragm
paralysis.
Other parameters
There was no statistically significant difference for necessity of
positive inotrope, and drainage and transfusion amounts between
the groups. Abacilar
et al
. reported a positive correlation
between TNF-
α
level and postoperative mediastinal drainage
amount.
2
We found a similar relationship between these two
parameters in our study, although not statistically significant.
Robicsek
et al
. reported that cardiac myocyte dehydration due
to relative hyperosmolarity secondary to hypothermal iced saline
caused myocardial functional disorder, and with the progression
