Truncus arteriosus is a congenital cardiovascular anomaly characterized by a single arterial vessel (truncus) with one valve arising from the heart. The truncus overrides a large perimembranous ventricular septal defect and receives mixed blood from both ventricles and supplies blood to the pulmonary, systemic, and coronary circulation, the ratio of the bloodflow vary according to the different vascular resistances. The anomaly is divided into four types according to Collett and Edwards classification on the basis of the origin of the pulmonary arteries from the truncal artery. In truncus, the goal is to balance the circulation to obtain QP:QS = 1 to maintain reasonable oxygen saturation as well as adequate organ perfusion. Careful titration of anesthetic agents and careful monitoring of their hemodynamic effects and appropriate measures to adjust pulmonary (PVR) and systemic vascular (SVR) resistances and cardiac performance are probably more important than the selection of a particular anesthetic agent. Postoperatively, low cardiac output can be expected because of high PVR and right ventricular failure. High PVR, both sustained and paroxysmal, should be anticipated. Pulmonary hypertensive crisis presents as low cardiac output and right ventricular failure. Avoidance of these potentially fatal events is essential to decrease the mortality and morbidity associated with repair. Events that trigger a hypertensive crisis, such as hypoxia, hypercapnia, acidosis, pain, airway stimulation, and left ventricular failure, must be avoided.
Intraoperative Doppler tissue imaging with pulsed wave Doppler is a rapid method to determine the direction, timing, and velocity of regional longitudinal myocardial motion and quantify systolic and diastolic function. Although DTI provides regional measurements, sampling from different sites will help compensate for any differences, facilitating the evaluation of global EF and diastolic function and the calculation of filling pressures. Repeated DTI observations in the same patient enable the detection of regional ischemia, and the appearance or detection of postsystolic shortening is a sensitive index of ischemic but viable myocardium. DTI has also been used to detect subclinical ventricular dysfunction in asymptomatic patients with valvular disease and differentiate physiologic from pathologic hypertrophy and distinguish constrictive pericarditis from cardiomyopathy.
Measures to minimize myocardial damage have been an important target of research; therefore, a better understanding of the role of anesthetics in the prevention of myocardial injury may provide anesthesiologists with strategies to improve outcome. Myocardial ischemia initiates a range of cellular events, which are initially mild and become progressively damaging with increasing duration of ischemia. Perioperative myocardial ischemia is a serious adverse event that can increase morbidity and mortality after cardiac and noncardiac surgery. Several treatment approaches that prevent or lessen myocardial ischemia during and after surgery have been proposed. The use of particular anesthetics for the induction and maintenance of general anesthesia is one approach to protect against the adverse effects of ischemia. Experimental data indicate that some anesthetics, such as volatile general anesthetics, exert protective effects against ischemia–reperfusion injury that are independent of their hemodynamic effects. To approach this subject, several points should be well understood, such as myocardial metabolism, the pathophysiology of myocardial ischemia, myocardial stunning and hibernation, the effects of ischemia on myocardial metabolism, reperfusion injury, preconditioning, myocardial protection, temperature control, cardioplegia, ischemic and anesthetic preconditioning, and pharmacotherapy.
Dexmedetomidine, a centrally acting α2-adrenoceptor agonist, has been used as an adjunct to anesthesia and in sedation because of its efficient sympatholytic, analgesic, and anxiolytic properties. Recently, several studies have focused on the potential neuroprotective and renoprotective effects of dexmedetomidine in patients undergoing different surgical procedures.
Coronary artery bypass grafting (CABG) with cardiopulmonary bypass is associated with a high incidence of perioperative renal dysfunction that is believed to be caused partly by the increased sympathetic nervous system activity leading to compromised hemodynamics and attenuated renal function.
To test the hypothesis that dexmedetomidine would exert a renal protective effect and prevent the development of acute kidney injury in patients with mild to moderate renal dysfunction undergoing elective CABG during the early postoperative days.
A double-blind randomized placebo-controlled study was carried out. Eighty adult patients with mild to moderate renal impairment (serum creatinine between 1.5–2 mg/dl) and scheduled for elective CABG with cardiopulmonary bypass were randomly allocated to either dexmedetomidine infusion or placebo infusion groups. Infusion was started after induction of anesthesia and continued until the end of surgery. The primary outcome variables measured for assessment of renal functions included serum creatinine, creatinine clearance, and urinary output in the 72 h postoperatively.
No significant difference was detected for any indicators of renal function between both groups, except for an increase in urinary output in the dexmedetomidine infusion group in the first 24 h after surgery (P=0.007).
The use of dexmedetomidine infusion did not alter renal function in terms of serum creatinine or creatinine clearance but was associated with an increase in urinary output in the first 24 h.