Laboratory measurements:
Blood was collected four times in both groups for measurement, using an
retrograde cardioplegia cannula -
1. Immediately after entering the cardiopulmonary bypass,
2. 20 min after cross-clampplacement,
3. Immediately before cross-clamp removal, and
4. 20 min after removal of the cross-clamp. Blood samples were stored at
-80°C.
Measurement of Serum adenosine deaminase activity: Serum
adenosine deaminase activity (ADA) was determined using the
spectrophotometric method described byGiuisti, which relies on the
indirect calculation of ammonia formation resulting when adenosine
deaminase acts in excess of adenosine (5). Results were expressed as
units per liter (U/L).
Thiol/disulfide homeostasis tests: Thiol/disulfide homeostasis
was measured with the commercially available novel automatic and
spectrophotometric technique developed by Erel and Neselioglu (6) (Rel
Assay Diagnostics, Turkey).Using this technique, dynamic and reducible
disulfide bonds in the samples were reduced to free functional thiol
groups by means of sodium borohydride. In order to avoid unused reduced
sodium borohydride being reduced to dithionite-2 nitrobenzoic (DTNB),
NaBH4 was removed with formaldehyde. Values for native thiol (NT) and
total thiol (TT) were calculated following reaction with DTNB. Disulfide
(DS) levels were calculated ashalf the difference of the result obtained
by subtracting the native thiol value from the total thiol content.
Measurement of paraoxonase activity: The fully automated method
developed by Rel Assay Diagnostics (Mega Tıp, Gaziantep, Turkey) was
employed to examine serum paraoxonase 1 (PON) activity. This technique
involvesparaoxonase activity beingcalculated in medium without NaCl
(basal paraoxonase activity) and with NaCl (salt-stimulated paraoxonase
activity). Hydrolysis of the paraoxone (diethyl-p-nitrophenylphosphate)
is monitored by observing the increase in absorbance at 37-C and 412 nm.
The quantity of p-nitrophenolproduced by the hydrolysis is calculated
using the molar absorption coefficient 17,000 Mj1cmj1 (at pH 8). Net
values with enzymatic activity are obtained by subtracting the basal
activity value from the salt-stimulated activity value. The results are
expressed as unit per liter, equivalent to the hydrolysis of 1 micromole
substrate in one minute and one liter.
Measurement of arylesterase activity: The fully automated method
developed by Rel Assay Diagnostics (Mega Tıp, Gaziantep, Turkey) was
employed to measure paraoxonasearylesterase form as a result ofrase
activity in the serum samples. This technique involves the use of phenyl
acetate as a substrate for calculatingarylesterase activity. Phenol and
acetic acidphenyl acetate hydrolysis. The phenol that forms thenbinds to
4- aminoantipyrine and potassium ferricyanide, and is measured using the
colorimetric method. Arylesterase enzyme activity is calculated from
4000 Mj1cmj1, representing the molar absorption coefficient of the
colored complex that forms. The results are expressed as unit per liter,
equivalent to the hydrolysis of 1 micromole phenyl acetate in one minute
and one liter.
Measurement of xanthineoxidase (XOD): XOD measurement was
performed using a microELISA kit and aRel Assay DiagnosticsReader device
and washer. This was operated manually, with specimens being
automatically washed and read.
Measurement of superoxide dismutase (SOD): SOD was measured
automatically on a Selectra (The Netherlands) biochemistry autoanalyzer,
using aRel Assay Diagnostics automatic biochemistry kit.
Measurement of Creatine kinase-MB (CK-MB): CK-MB was measured
automatically using a Rochechemiluminescence method device and a
Rochechemiluminescence kit.
Measurement of Troponın I: Troponin I was measured
automatically using a Roche chemiluminescence method device and a Roche
chemiluminescence kit.
CPB and cross-clamp times, and lengths of stay in the intensive care
unit were recorded. Inotropic support or intra-aortic balloon pump
device (for weaning the CPB or in the first 24 hours postoperatively)
requirements were also noted.