Cardiovascular Journal of Africa: Vol 26 No 4 (July/August 2015)

CARDIOVASCULAR JOURNAL OF AFRICA • Volume 26, No 4, July/August 2015

162

AFRICA

associated with systemic changes in leukocyte subtypes, such as

neutrophilia and lymphopaenia, and increased N:L ratios.

the postoperative period, increased N:L ratio not only assesses

the immune condition of the patient but also provides valuable

clues regarding morbidity and mortality. In addition, in clinical

practice its measurement is inexpensive and simple.

In our study patients, some morbidity markers such as

postoperative inotropic need [12 (40.0%) vs 11 (36.7%)

0.791],

postoperative IABCP need [6 (20.0%) vs 1 (3.3%)

0.103] and

postoperative myocardial infarction (MI) [2 (6.7%) vs 0 (0.0%)

0.492] were found more widely in the CPB group than in the

OPCAB group. This is compatable with the literature. Hospital

stay was also significantly longer in the CPB group (8.97

2.39

vs 5.90

2.07 days,

0.001).

Takahashi

et al

. demonstrated that lymphopenia represents

an immunodepression status leading to the development of

postoperative infection.

It was suggested that lymphopenia may

be caused by redistribution between peripheral blood and bone

marrow pools in addition to tissue sequestration of activated

lymphocyte subsets.

In another study designed by Yamanaka

et al.

, it was reported

that the immune system may have been inhibited by neutrophils.

Natural killer cells and lymphocytes may have been supressed,

and T cells could have been activated by neutrophils in the

co-culture of neutrophils and lymphocytes of normal healthy

donors. The number of neutrophils added directly affected the

degree of supression.

Although conventional CABG surgery with the use of CPB

is a safe and effective procedure, it is known to evoke many

side effects. It is unique because synthetic non-endothelial

surfaces, in which blood continuously recirculates, contribute

to the inflammatory response through ‘contact activation’ of

the immune system. Aortic cross-clamping causing ischaemia–

reperfusion injury to vital organs such as the kidney, brain,

myocardium and intestine plays a key role in the activation of a

stress–response cascade.

Multi-organ system dysfunction, such as respiratory failure,

coagulopathy, renal insufficiency, neurocognitive defects and

myocardial dysfunction, occur due to the hyperinflammatory

cascades.

Because of the cross relationship between multi-

organ dysfunction and the hyperinflammatory state, in our

study, patients with postoperative complications such as renal

insufficiency, postoperative infection and respiratory problems

were excluded from the study population.

Aggregation of WBCs in the capillaries of the lung and

degradation of complement proteins, resulting in an activated

inflammatory process, cause severe pulmonary dysfunction.

The hyperinflammatory state caused by CPB may play a key

role in the genesis of catastrophic complications, leading to

postperfusion syndrome, which involves decreased systemic

vascular resistance, fever and accumulation of fluid in the

interstitial space.

In the literature, there are many studies

related to attenuating negative outcomes of CPB by inhibiting

the inflammatory response during coronary surgery. Leukocyte

depletion,

aprotinin, corticosteroids

and heparin-coated

circuits

are noted as tools to attenuate the inflammatory

reactions mediated by CPB.

OPCAB techniques working on the beating heart without

extracorporeal circulation may be a more radical and effective

way of counteracting the effects of the inflammatory reaction

and oxidative stress. Despite great excitement among some

cardiac surgeons and patients, the real impact of OPCAB

in attenuation of systemic inflammation is still uncertain.

Many clinical comparative studies

and meta-analyses

have

demonstrated shortened length of hospital stay, reduced

neurological complications, and reduced hospital costs for

patients operated on with OPCAB techniques compared to

those undergoing conventional CABG with CPB.

Decreased

postoperative blood loss and need for transfusion, and shorter

ventilatory support and intensive care unit time have also been

reported with OPCAB operations.

Our study had similar follow-up results, showing increased

total leukocyte and neutrophil counts and N:L ratios, and

decreased lymphocyte counts in both groups of patients, but this

was more significant in the CPB group, indicating a more intense

inflammatory reaction. In our study, hospital length of stay was

longer in the CPB group than in the OPCAB group, which is

compatible with the literature.

The inflammatory response due to cardiac surgery is mainly

related to the cellular immune system.

During CPB, because of

haemodilution, leukocyte counts decrease, but after surgery they

increase dramatically.

The contact and complement systems

producing kallikrein and C5a strongly activate neutrophils

during cardiopulmonary bypass.

IL-6 and IL-8 mediating CPB

may partially inhibit apoptosis of neutrophils, and thereby the

period of neutrophil activity is prolonged.

Suppression of cellular immunity by the lymphocytes and

activation of the inflammatory response, characterised by

neutrophilia, are substituted by the N:L ratio. The N:L ratio

is increased when lymphopenia or neutrophilia develops. The

favourable pattern of changes in systemic leukocyte counts

could be defined as a lesser impairment of cellular immunity,

determined by lymphocyte counts, and lesser activation of

the inflammatory response, measured by neutrophil counts. A

favourable pattern of changes in systemic leukocyte counts is

indicated by a lesser value of the N:L ratio.

CABG surgery without CPB has been presented as an

alternative to minimise the deleterious effects of CPB. The

superiority of OPCAB is mostly seen in the clinical era,

but

when discussing new techniques, it is also important to clarify

the pathophysiology of the procedure. The risk of infection after

cardiac surgery is increased with CPB because of neutrophil

activation via the complement cascade,

and also because of

attenuation of lymphocyte activation.

From the results of our

study, we could conclude that a more favourable pattern of N:L

ratio was ensured in the early stages of the postoperative period

(on the first postoperative day of our study) but later (on the

fifth postoperative day), the advantage of the OPCAB technique

disappeared, determined by the difference between N:L ratios of

the two groups.

From the results of our study, we could infer that the change

in N:L ratios on the first postoperative day, compared with

pre-operative values, was more dependent on lymphocyte count

changes, being more remarkable in the CPB group. On the fifth

postoperative day, the change in all values were similar in both

groups, compared with pre-operative values.

Although OPCAB has been widely used, no studies have been

performed focusing on its effect on the N:L ratio in comparison

with CPB. In our study, the groups were similar in terms

of pre-operative total leukocyte, neutrophil and lymphocyte