Material and Methods
This was a observational longitudinal study and was conducted in
accordance with the principles of the Declaration of Helsinki. The study
was approved by the Ethics Committee for Clinical Research at local
hospital (11.01.2019, 29620911-929-67). Ninety consecutive adult
patients of the American Society of Anesthesiologists (ASA) Class II-III
who underwent elective cardiac surgery with CPB over a 2-months period
were included in this study. Patients undergoing emergency or re-do
surgery, off-pump surgeries, transplant surgeries, vascular surgery were
excluded from the study. Patients with insulin dependent diabetes
mellitus (IDDM), those with a history of ejection fraction under 40% or
pulmonary, renal or hepatic failure, those with hematologic disorder,
those under 18 years old or those using alcohol, or any medication
suppressing stress response as corticosteroids, vitamin C, or
n-acetylcysteine, were not included the study. Since IDDM has a
different pathogenesis, it was excluded from the study, considering that
it may interact more negatively with tissue perfusion parameters. NIDDM
patients discontinued their oral antidiabetic medications 24-hour before
surgery. So the aim of this study is to evaluate the degree of stress
response and related tissue oxygenation parameters in NIDDM patients
whose documented preoperative normoglycemia with oral antidiabetic drug
use and patients without DM.
Pulse oximetry, five channel electrocardiography, invasive blood
pressure monitoring, bispectral index monitoring (BIS™, Covidien, MN,
ABD) and invasive internally calibrated pulse wave analysis (ProAQT;
Pulsion Medical Systems, Feldkirchen, Germany;
PPVProAQT, COProAQT) were performed. As
baseline measurement, patients received an initial hemodynamic
assessment based on stroke volume, cardiac output (CO), and mean
arterial pressure. DO2 (CO x arterial content of
O2), VO2 (CO x [arterial-venous
content of O2]), and O2ER calculations
were performed with these calculated CO values by pulse wave analysis.
However, when the CPB was initiated, pump flow was used as CO value due
to inaccurate pulse wave analysis measurements during CPB.
Patients with no history of DM prior to surgery, may exhibit transient
elevation of blood glucose >180 mg/dL during cardaiac
surgery and cardiopulmonary bypass, they may have insulin resistance. We
treated with a single or intermittent dose of intravenous insulin to
maintain glucose ≤ 180 mg/dL at these patients. After a single dose
insulin push therapy, blood glucose levels were re-evaluated and
intravenous insulin regimen was started when necessary as recommended by
Duggan et al.12 An endocrinology consultation was
obtained in the postoperative period in case DM was detected in some of
these patients. In patients with NIDDM, the bolus dose calculated with
the formula (blood glucose value - 100/40) was applied when blood
glucose was above 180 mg/dl. Then blood glucose value/100 units/hour
infusion dose was started.12 Blood glucose levels were
monitored with half an hour intervals.
Following adequate activated clotting time (>480 sec),
cannulation were performed and CPB was initiated. CPB was performed in
moderate hypothermia (28-31°C). Hemoglobin concentrations were kept
above 7.5 g/dl during operation.
Blood samples were collected from the radial artery and internal jugular
vein. Although jugular venous (ScvO2) and mixed venous
oxygen saturation values differ slightly, it is acceptable to use
ScvO2 instead of mixed venous oxygen
saturation.13 Blood glucose and gas analysis were
performed at four time points: after the induction of anesthesia before
the surgery as baseline values (T1), at the 5-10thminute of CPB (T2), at the 30-40th minute of CPB (T3),
and while the sternum was closing (T4). At these four time points,
hemodynamic parameters, central
venous oxygen saturation (ScvO2), lactate level, oxygen
delivery (DO2), oxygen consumption
(VO2), oxygen extraction rate (O2ER),
mean arterial pressure (MAP) and urine output values were recorded.