DISCUSSION
In our study, we found that DEX infusion has a predictable
cardiovascular effect, which was observed during the impregnation of the
infusion, a 20% drop in blood pressure is reported in the literature
and a 10-20% drop in heart rate over baseline parameters is also
expected. We also observed a reduction in narcotic consumption by the
DEX group.
The results obtained with the use of DEX, hemodynamic stability during
coronary anastomosis was beneficial, and also facilitated the technique
on a beating heart in patients undergoing off-pump CABG
(3 )(16 ).
The hemodynamic data was collected at four different times: baseline, at
the time of sternotomy, coronary anastomosis, and placement of the
sternal closure. These off-pump CABG surgical times were chosen because
they are reasonably considered the most significant painful stimuli
during sternotomy and the placement of sternal closure at the time of
coronary grafting (17 )(18 )(25 ).
Tachycardia is poorly tolerated in patients with heart failure, as this
may predispose the patient to cardiac arrhythmias during the
transoperative period. Consequently, atrial fibrillation and subsequent
myocardial ischemia may occur, thus leading to fatal complications in
some cases (19 )(26 ).
The use of DEX, due to its pharmacological property, can be used to
prevent tachycardia and attenuate the hemodynamic response during
cardiac surgery.
Studies suggest that the perioperative use of DEX may result in a
decreased risk of adverse cardiac events, including myocardial ischemia.
Stimulation of α-adrenergic receptors can modulate coronary blood flow
during myocardial ischemia, by preventing the redistribution of blood
flow, which leads to improvement of coronary perfusion. (27-28 )
This specific effect, along with hemodynamic stability andreduced surgical stimulus-response, make DEX an ideal adjuvant
anesthetic, particularly in patients undergoing coronary bypass
grafting.
Hemodynamic monitoring should be applied within the context of
therapeutic interventions, which have proven effective in the reversal
of the disease process (20 )(21 ).
The risk of adverse events in off-pump CABG, increases in patients with
specific comorbidities, such as recent myocardial infarction, left
ventricular ejection fraction (LVEF <40%), a history of lung
disease or renal dysfunction. The impact of comorbidities on
postoperative morbidity and the outcome have also been studied in
cardiac surgery where the use of hemodynamic therapy in the
perioperative period has been associated with a decrease in the
incidence of overall complications or length of postoperative stay in
cardiac surgery. Several interventions in the ICU after cardiac surgery
have been investigated, but the results have yet to significantly change
clinical practice (22 ).
Currently, these critically ill patients are hemodynamically optimized
with ”early goal-directed therapy” (EDGT), which in high-risk surgery
has been associated with a reduction in postoperative morbidity and
mortality along with a decrease in cardiac complications, particularly
in the case of arrhythmias (12 )(29 ).
Clinical studies that have been performed individually for cardiac
surgery, with a hemodynamic approach aimed at the goal of therapy during
the perioperative period, the hemodynamic objectives have been to
maintain: MAP 60–100 (mmHg); heart rate ≤90 (bpm); Hb ≥8 (g/dl);
SVO2 ≥60(%), CVP 6-8 (mmHg), Stroke Volume Variation
(SVV) 10 (%); stroke volume index (SVI) 30–65 ml; SVRI 1500–2500
(dyne x sec x cm-5 x m-2); Oxygen
delivery (DO2) 450–600 (ml/ min/ m2);
Hct ≥30(%); pH 7.35–7.45; PO2 100mm Hg;
PCO2 35–45 mm Hg; SpO2 ≥95%, Lactate
≤2 (mmol/l) after 8 h from the postoperative period
(23 )(24 ).