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    In Vitro Effect of Dexmedetomidine on Platelet Aggregation
    (Elsevier Science Inc, 2013) Kose, Emine Arzu; Nevruz, Oral; Honca, Mehtap; Yildirim, Vedat
    Background and objectives: Dexmedetomidine is a selective alpha(2)-agonist. There are 250-300 alpha(2)-agonist-adrenoceptor on the surface of each human platelet and ephedrine induces platelet aggregation by binding these receptors. This study was designed to study platelet function after incubation with therapeutic concentrations of dexmedetomidine. Methods: The study was carried out on 18 healthy, non-smoking males, ages ranging 25 to 35 years old. Because of the recommended therapeutic concentration range of dexmedetomidine obtained by intravenous infusion is 0.4-1.2 ng.mL(-1), dexmedetomidine solutions were prepared in three different concentrations. The calculated value of dexmedetomidine solution and diluent without dexmedetomidine as control were added to the blood sample. Thus, we obtained 0, 0.4, 0.8 and 1.2 ng.mL(-1) dexmedetomidine concentrations of plasma. Each concentration of dexmedetomidine was incubated with whole blood at 37 degrees C during 15 minutes. Then blood samples were centrifugated to prepare platelet-rich plasma and platelet-poor plasma. The platelet-rich plasma was diluted with the platelet-poor plasma to yield test platelet-rich plasma with a final platelet count of 250 +/- 50 X 10(9).L-1. Results: The platelet aggregation amplitudes and slopes were statistically similar among all groups by the aggregation test, which were performed with ADP, collagen or epinephrine. Conclusion: Therapeutic concentrations of dexmedetomidine had no effect on the platelet functions in healthy individuals in vitro. (C) 2013 Sociedade Brasileira de Anestesiologia. Published by Elsevier Editora Ltda. All rights reserved.
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    Preoperative exercise heart rate recovery predicts intraoperative hypotension in patients undergoing noncardiac surgery
    (Elsevier Science Inc, 2012) Kose, Emine Arzu; Kabul, Hasan Kutsi; Yildirim, Vedat; Tulmac, Murat
    Study Objective: To assess the predictive role of heart rate (HR) recovery in the detection of intraoperative hypotension in patients undergoing noncardiac surgery. Design: Prospective, observational study. Setting: Department of cardiology and operating rooms of university hospitals. Patients: 160 ASA physical status 1 and 2 patients scheduled for elective noncardiac surgery. Measurements: All patients underwent exercise stress testing. Maximum HRs and metabolic equivalent levels were recorded. Heart rate recovery at the first, second, and third minutes were calculated by subtracting HRs one, two, and three minutes into the recovery period from the maximal HR at peak exercise. A decrease in mean arterial pressure (MAP) of greater than 30% was defined as intraoperative hypotension and recorded. Patients were classified to two groups according to whether they had intraoperative hypotension. Main Results: Hypotensive episode was observed in 31 patients (19.7%) during the operation. The presence of diabetes mellitus was higher in patients with intraoperative hypotension (22.6% vs 7.1%, P = 0.019). Mean HR recovery at the first, second, and third minutes was significantly lower in the intraoperative hypotension group (P = 0.001, P = 0.004, and P = 0.031, respectively). Heart rate recovery at the first, second, and third minutes was a good predictor of intraoperative hypotension, but only HR recovery at the first minute (OR 0.82, 95% CI 0.73 to 0.92, P = 0.001) and HR recovery at the second minute (OR, 0.90; 95% CI, 0.82 to 0.98; P = 0.019) were independent predictors of intraoperative hypotension. A higher negative correlation was noted between the degree of MAP reduction and HR recovery at the first minute (r = -0.797, P = 0.001). Conclusions: Abnormal preoperative exercise HR recovery predicts intraoperative hypotension in patients undergoing noncardiac surgery. Given the importance of intraoperative hypotension, preoperative use of exercise testing might be considered. (c) 2012 Elsevier Inc. All rights reserved.