ABSTRACT
Background: Alpha 2-adrenergic agonists decrease sympathetic tone with ensuing attenuation of neuroendocrine and hemodynamic responses to anesthesia and surgery. Also, administration of beta -adrenergic antagonists contributes to prophylaxis against hypertension, tachycardia and myocardial ischemia and myocardial protection during cardiac surgery. The effects of dexmedetomidine (DEX), a highly specific alpha 2-adrenergic agonist, on these responses have not yet been fully reported in patients undergoing cardiac surgery. Esmolol (ESM) is a cardioselective, short-acting β -blocking agent. Previous studies have established the effectiveness of esmolol in the reduction of hemodynamic responses during anesthetic induction.
continued to decrease till it developed a significant drop to 74±9 mmHg poststernotomy around 65 min after the start of infusion and gradually increased insignificantly to 78±6 mmHg at the end of surgery while, SVRI did not show any significant changes. In ESM group, MAP was decreased significantly to 87±14 mmHg (P < 0.05) 3 min after the start of infusion and did not show any significant change till the end of surgery while, SVRI did not show significant changes during different studied time intervals. The CVP, PCWP, MPAP and PVRI did not show any statistically significant change at the study time intervals in both groups. DEX had less incidence of intraoperative bradycardia (2 vs. 4 patients), tachycardia (0 vs. 2 patients), hypertension (0 vs 2), hypotension (2 vs 4) and ST changes (1 vs5). DEX also decreased the requirements of fentanyl (26.3±4.3 vs 35.4±5.1 ug/kg)), propofol (810±43 vs 935±52 mg) and midazolam. The incidence of fentanyl-induced muscle rigidity (5 vs 12 patients) and postoperative shivering (4 vs 13 patients) were less in DEX group than ESM group.
Conclusion: Dexmedetomidine in patients undergoing beating heart surgery decreased intraoperative sympathetic tone, induced sedation, attenuated hyperdynamic responses to anesthesia and surgery and overall hemodynamic variability than esmolol. The need for anesthetics, muscle rigidity, perioperative myocardial ischemia and shivering were less also in DEX group.
Aim: The study of hemodynamic responses of dexmedetomidine and esmolol and their effects on the anesthetic requirements during anesthesia in beating heart surgery.
Methods: Forty patients scheduled for elective beating heart surgery received a dexmedetomidine 1 ug/kg over 10 min before anesthesia was induced and 0.5 ug/kg/h thereafter until the end of surgery in the DEX group and a loading dose of 0.5mg/kg esmolol IV was given over 5 min followed by a continuous infusion of 50 ug/kg/h until end of surgery in the ESM group. Total intravenous anesthesia using fentanyl, cisatracurium and propofol and oxygen air mixture (40%-60%) was used until the end of surgery. Hemodynamics measured included heart rate, mean arterial pressure, filling pressures, cardiac index, systemic and pulmonary vascular resistances. The incidence of hypotension, hypertension, tachycardia, bradycardia, dysrhythmias, ST segment changes, total anesthetics requirements, muscle rigidity and postoperative shivering were recorded.
Results: DEX significantly decreased HR and CI to after to 70±6 bpm and 2.2±0.1 l/min/m2 (p<0.05) 3 min then, increased HR and CI significantly to baseline recording to 77±9 bpm and 2.5±0.1 l/min/m2 (p<0.05) after 10 min from the start of infusion. In the postinduction period HR insignificantly decreased to 71±8 bpm after sternotomy about 65 min from the start of infusion. The postinduction period showed insignificant gradual increase in HR to 79±6 bpm while, CI continued to be below or at the baseline reading till it reached the baseline recording at the end of surgery. ESM dropped HR insignificantly at 3 min of infusion to 73±8 bpm and significantly dropped CI to 2.1±0.3 l/min/m2 (p<0.01). HR and CI continued to show insignificant changes till the end of surgery but HR exceeded the baseline readings and CI did not reach it. DEX significantly increased MAP and SVRI to 101±13 mmHg (p<0.05) and 3985±243 dyn.s.cm5.m-2 (p<0.01) at 3 min of infusion then significantly decreased to baseline reading to 89±10 mmHg and2428±276 dyn.s.cm-5.m-2 at 10 min time interval. MAP