The Effects of Esmolol and Dexmedetomidine on Myocardial Oxygen Consumption During Sympathetic Stimulation in Dogs

Comparison of the Effects of Dexmedetomidine and Propofol on Hemodynamics and Oxygen Balance in Children with Complex Congenital Heart Disease Undergoing Cardiac Surgery

OBJECTIVE

The aim of this study was to compare the effects of anesthesia by dexmedetomidine and propofol on the hemodynamics and oxygen balance in children with complex congenital heart disease who were undergoing cardiac surgery.

METHODS

Fifty-seven children were randomized to receive either a continuous infusion of propofol (6-8 mg/kg/h) or dexmedetomidine (0.5-0.7 μg/kg/h) after anesthesia induction. Hemodynamic data were recorded. Oxygen balance parameters were assessed at baseline after midazolam sedation, before and immediately after skin incisions were made, after sternotomy, 5 minutes after protamine administration, and at the end of surgery.

RESULTS

Compared with the dexmedetomidine group, the propofol group exhibited decreases in blood pressure, cardiac output, and cardiac index before skin incision (P < .05) and increases in blood pressure, heart rate, cardiac output, and cardiac index after sternotomy (P < .01). However, very similar trends in oxygen dynamics were obtained in both groups (P > .05), and the cardiac index was not correlated with total oxygen consumption (r = -0.109, P = .066) or the oxygen extraction ratio (r = -0.107, P = .072).

CONCLUSIONS

Dexmedetomidine infusion may be superior to propofol anesthesia in children with complex congenital heart disease who are undergoing cardiopulmonary bypass because dexmedetomidine was associated with less variability in heart rate or blood pressure during surgery. However, the oxygen balance was similar when either agent was used.

Evaluation of a ketamine-propofol drug combination with or without dexmedetomidine for intravenous anesthesia in cats undergoing ovariectomy

OBJECTIVE

To evaluate the use of a ketamine-propofol combination, with or without dexmedetomidine, in cats undergoing ovariectomy and to assess Heinz body formation following administration of these drugs.

DESIGN

Randomized clinical trial.

ANIMALS

15 client-owned female cats.

PROCEDURES

Anesthesia was induced with a ketamine (2.0 mg/kg [0.91 mg/lb])-propofol (2.0 mg/kg) combination with (n = 7) or without (8) dexmedetomidine (0.003 mg/kg [0.0013 mg/lb]) and was maintained via continuous IV infusion of a 1:1 ketamine-propofol combination (administration rate for each drug, 10.0 mg/kg/h [4.54 mg/lb/h]). Cats underwent ovariectomy; duration of infusion was 25 minutes. Physiologic variables were measured at predetermined time points. Heinz bodies were quantified via examination of blood smears. Numeric scales were used to assess quality of recovery, degree of sedation, and signs of pain after surgery.

RESULTS

The ketamine-propofol group had a significantly higher mean heart rate at several time points during drug infusion, a significantly shorter time from the end of infusion to extubation (7 vs 29 minutes), and significantly lower sedation scores for the first hour after surgery than did the ketamine-propofol-dexmedetomidine group. Other variables were similar between groups; recovery was smooth, and anesthesia and postoperative analgesia were deemed adequate for all cats. The number of RBCs with Heinz bodies was not increased after surgery, compared with values immediately after anesthetic induction.

CONCLUSIONS AND CLINICAL RELEVANCE

Total IV anesthesia with a ketamine-propofol combination, with or without dexmedetomidine, appeared to be effective in healthy cats. These short-term infusions produced smooth recovery and adequate analgesia during the postoperative period.

The cardioprotective effect of dexmedetomidine on global ischaemia in isolated rat hearts

AIM

Dexmedetomidine is a highly specific and selective alpha-2 adrenergic agonist that is now widely used in the intensive care setting. Many intensive care unit (ICU) patients are at risk of respiratory or cardiac arrest. This study was conducted to determine whether dexmedetomidine exhibits a cardioprotective effect on global ischaemia and subsequent myocardial infarction.

METHODS

Isolated rat hearts were subjected to 30 min of global ischaemia followed by 120 min reperfusion, with administration of 0, 1 and 10nM dexmedetomidine during the pre-ischaemic period (n=7 each group). Secondly, 1 microM yohimbine, an alpha-2 antagonist, was given during the pre-ischaemic period, alone or in combination with 10 nM dexmedetomidine (n=7 each group).

RESULTS

Dexmedetomidine administration reduced coronary flow significantly (103.6+/-4.7%, 77.9+/-3.7, 63.7+/-6.1%, of the baseline values for 0, 1 and 10 nM dexmedetomidine, respectively), and yohimbine administration reversed this effect (88.0+/-2.2%). Dexmedetomidine improved the infarct size at each concentration (45.3+/-3.6, 30.2+/-3.3, and 21.2+/-2.3% of the total left ventricular mass for 0, 1, and 10nM dexmedetomidine, respectively), which was also reversed by yohimbine (43.6+/-1.4%).

CONCLUSION

Dexmedetomidine exhibited a cardioprotective effect on global ischaemia in the isolated rat heart model, which was mediated by alpha-2 adrenergic stimulation.