Investigation of beta blocker withdrawal syndrome after esmolol infusion in rats

SUMMARY:Investigation of ?Beta Blocker Withdrawal Syndrome? after Esmolol Infusion in RatsAyşe Pelin Girgin, MD. Dokuz Eylul University Hospital,Department of Anesthesiology and Reanimation, IZMIR.This randomized, controlled, experimental study investigated if esmolol, beta-1receptor blocker, caused ?Beta blocker withdrawal syndrome? or not after abrupt cessation.Eighteen male Wistar rats were divided into 3 groups. After tracheostomy andinvasive monitorization, baseline values of heart rate and systemic arterial pressure wererecorded in anesthetized rats during spontaneous ventilation. In Control group (n=6); after abolus dose (0.5 mL), 0.9% NaCl was infused for 45 minutes. In groups of E150 (n=6) and E300(n=6), after a bolus dose (0.5 mg/kg), esmolol was infused with doses of 150 microg/kg/minor 300 microg/kg/min for 45 minutes, respectively. The hemodynamic values obtained duringinfusion period and following 30 minutes were given as percentages of the baseline. Varianceanalysis and Student?s t test were performed for statistical analysis and a value of p<0.05 wasconsidered significant.No statistical significance was found in regard to baseline values among groups. Ingroups of Control, E150 and E300, percentages of heart rate were 99.0±4% (p>0.05), 77.7±3%(p<0.01), 79.5±4% (p<0.01) at the end of infusion, and 98.8±5% (p>0.05), 93.6±3% (p>0.05),87.3±4% (p<0.05) at the 30th minute after stopping infusion, respectively. Percentages ofmean arterial pressure were 89.5±4% (p<0.05), 62.8±4% (p<0.01), 62.5±3% (p<0.01) at theend of infusion, and 80.3±4% (p<0.01), 79.4±3% (p<0.01), 77.7±7% (p<0.05) at the 30thminute after the end of infusion in groups of control, E150 and E300, respectively. During the30 minutes of observation period, hemodynamic values did not exceed the baseline.It is determined that, after a bolus dose, abrupt withdrawal of esmolol infusion at dosesof 150 microg/kg/min or 300 microg/kg/min, do not cause beta blocker withdrawal syndromein rats. However, results of this experimental study should be supported with a clinicalprospective one.Keywords: Esmolol, beta blocker withdrawal syndrome, rat.