Cardiovascular Journal of Africa: Vol 30 No 6 (November/December 2019)

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CARDIOVASCULAR JOURNAL OF AFRICA • Volume 30, No 6, November/December 2019 AFRICA 337
three acceptable measurements were noted for the calculation.
Recommendations in the ATS/ERS guidelines were followed
for bronchodilator reversibility testing. The measurements were
performed before (baseline measurement) and 15 to 20 minutes
after the bronchodilator administration.
Patients were asked to inhale a dose of 100 μg salbutamol in
one breath to total lung capacity after an incomplete expiration,
to hold his/her breath for five to 10 seconds and then exhale.
A total dose of 400 μg salbutamol was administered in four
separate breaths via a metered-dose inhaler using a spacer.
If the FEV1 and/or FVC value changes were > 12% and 200
ml compared with baseline, it was identified as a significant
bronchodilatation.13 In such a case, the patient was accepted as
asthmatic and excluded.14
The MVS time was defined as the time elapsed from the
beginning of the postoperative period to the time of extubation.
Patients were followed with 8–10 ml/kg tidal volume and 2–3
cm H2O-positive end-expiratory pressure. Weaning from MVS
was planned according to the following standard extubation
criteria: the patient was expected to maintain stable gas exchange
(checked by blood gas analysis, no hypercapnia, no hypoxia, no
acidosis or alkalosis, partial pressure of oxygen > 150 mmHg
when inspiratory oxygen fraction ≤ 0.5), have stable neurological
and motor functions, and be in a stable haemodynamic status
(effective urine output, arterial blood pressure and heart rate
within expected values). If the patient could not be weaned from
MVS after 48 hours, it was accepted as PMV.
Patients who had a history of one pack or more of tobacco
product smoking in a day or tobacco smoke exposure were
accepted as smokers and were grouped into active and passive
smokers, respectively. Active smokers were patients who were
tobacco product smokers at the time of the operation, and
passive smokers were patients who had no history of tobacco
product consumption but were exposed to tobacco smoke.15,16
Patients who quitted smoking within a year before the CABG
surgery were identified as ex-smokers and included in the
passive-smoker group, as the benefits of smoking cessation have
been most evident in the first year in COPD patients.17
Surgery
All patients were sedated with intravenous midazolam 2 mg
prior to transport to the operating room. Invasive arterial blood
pressure monitoring via a radial artery catheter, and 12-lead
ECG, urinary output, pulse oximetry and capnography were
established. General anaesthesia was induced with fentanyl
10 μg/kg, midazolam 0.1 mg/kg and rocuronium 1 mg/kg.
Also, methylprednisolone 1 mg/kg and intravenous pheniramine
were administered in order to prevent possible reactions after
protamine administration.
In OPCAB surgery, after a median sternotomy, left internal
mammary artery and saphenous vein grafts were harvested
according to the number of target vessels. The bilateral internal
mammary arteries were not used in any cases. As a standard
protocol, 10 ml 15% magnesium sulfate and lidocaine 1 mg/kg
were administered as intravenous infusion while the left internal
mammary artery graft was being harvested to benefit the anti-
arrhythmic effects of magnesium and lidocaine. The level of
activated clotting time was maintained above 300 seconds with
heparin (100–200 IU/kg) administration.
Two pericardial stay sutures with atraumatic needles were
used to stabilise and elevate the heart. The heart was allowed
to lean into the right hemithorax by creating an opening in the
right pleura, and the patient’s position was set at 20 degrees
Trendelenburg if a circumflex artery bypass was necessary.
The tidal volume was maintained in the range of 350 to 400
ml with high-frequency respiration to keep the heart stabilised.
The patient’s body temperature was kept between 34 and 36°C,
mean arterial blood pressure was kept in the range of 60 to 90
mmHg and the heart rate was kept between 60 and 80 beats/
min with esmolol infusion if necessary. The protocol of esmolol
administration was 1 mg/kg initial bolus dose intravenous
infusion over 30 seconds, followed by 0.15–0.3 mg/kg/min
intravenous infusion, adjusted according to the heart rate.
After completion of all anastomoses, the heparin was
neutralised with 50–100 IU/kg protamine administration.
Low-molecular-weight heparin 1 × 0.6 cm3 was administered
to all patients four to six hours after admission to the intensive
care unit (ICU), except for those who underwent a revision for
postoperative haemorrhage. On the first postoperative day, 100
mg acetylsalicylic acid and 75 mg clopidogrel were ordered in
the ICU.
In ONBHCAB surgery, the activated clotting time was
maintained above 450 seconds. CPB was established after an
ascending aortic and two-stage right atrial venous cannulas were
placed. The patient’s body temperature was kept between 34
and 36°C and mean arterial blood pressure between 60 and 90
mmHg. The heart rate was kept in the range of 60 to 80 beats/
min with an esmolol infusion that was identical to the protocol
followed in OPCAB patients. The tidal volume was maintained
in the range of 350 to 400 ml with high-frequency respiration.
The first arterial blood gas measurement was performed while
the patient was breathing operating room air. The following
intra-operative arterial blood gas analyses were performed just
after the initiation of general anaesthesia and every 30 minutes
until the end of the operation. In the ICU, the first arterial
blood gas measurement was performed just after the patient
was admitted to the unit, and the following measurements were
done every hour until the patient was weaned from MVS, and
every six hours until the patient was transferred back to the
ward. The threshold levels of pH and partial pressure of carbon
dioxide were in the ranges of 7.35 to 7.45 and 38 to 42 mmHg,
respectively. The criteria for re-intubation were partial oxygen
pressure below 75 mmHg and oxygen saturation below 80% in
arterial blood, accompanied by haemodynamic instability.
Statistical analysis
Statistical analysis of the data was performed with the Statistical
Package for the Social Sciences (SPSS 16.0 Inc, Chicago, IL,
USA) software. Categorical data are reported as numbers and
percentages. Continuous data are reported as mean ± standard
Table 1. Global Initiative for Chronic Obstructive Lung Disease (GOLD)
study classification
GOLD class Severity of airflow limitation FEV1 value (%)
I Mild ≥ 80
II Moderate 50 ≤ FEV1 < 80
III Severe 30 ≤ FEV1 < 50
IV Very severe < 30