Effect of Dexmedetomidine on Maintaining Perioperative Hemodynamic Stability in Elderly Patients:A Systematic Review and Meta-analysis

Objective Dexmedetomidine is a highly selective alpha-2 adrenergic receptor agonist with sedative and analgesic properties but without respiratory depression effect and has been widely used in perioperative anesthesia.Here we performed a systematic review and meta-analysis to evaluate the effect of dexmedetomidine on maintaining perioperative hemodynamic stability in elderly patients.Methods PubMed,Web of Science,the Cochrane Library,China National Knowledge Infrastructure(CNKI),and Wanfang Data were searched for randomized-controlled trials(RCTs)on the application of dexmedetomidine in maintaining perioperative hemodynamic stability in elderly patients from their inception to September,2021.The standardized mean differences(SMD)with 95%confidence interval(CI)were employed to analyze the data.The random-effect model was used for the potential clinical inconsistency.Results A total of 12 RCTs with 833 elderly patients(dexmedetomidine group,546 patients;control group,287 patients)were included.There was no significant increase in perioperative heart rate(HR),mean arterial pressure(MAP),and diastolic blood pressure(DBP)in the dexmedetomidine group before and during the operation.In addition,the variations of hemodynamic indexes including HR,MAP,SBP(systolic blood pressure),and DBP were significantly lower in the dexmedetomidine group compared with the control group(HR:SMD=-0.87,95%CI:-1.13 to-0.62;MAP:SMD=-1.12,95%CI:-1.60 to-0.63;SBP:SMD=-1.27,95%CI:-2.26 to-0.27;DBP:SMD=-0.96,95%CI:-1.33 to-0.59).Subgroup analysis found that with the prolongation of 1.0μg/kg dexmedetomidine infusion,the patient’s heart rate declined in a time-dependent way.Conclusion Dexmedetomidine provides more stable hemodynamics during perioperative period in elderly patients.However,further well-conducted trials are required to assess the effective and safer doses of dexmedetomidine in elderly patients.

Downregulation of Na^＋/Ca^2＋ Exchanger Isoform 1 Protects Isolated Hearts by Sevoflurane Postconditioning but Not by Delayed Remote Ischemic Preconditioning in Rats

Background：Calcium regulatory proteins-L-type Ca^2＋ channels （LTCCs）,ryanodine receptor 2 （RyR2）,and Na^＋/Ca^2＋ exchanger isoform 1 （NCX1） have been recognized as important protective mechanisms during myocardial ischemia-reperfusion injury （I/RI）.Both sevofturane postconditioning （SevoPoC） and delayed remote ischemic preconditioning （DRIPC） have been shown to protect the heart against I/RI.In this study,we aimed to compare the effects of SevoPoC and DRIPC on the expression of the three calcium regulatory proteins in an isolated rat heart model.Methods：After 30-min balanced perfusion,isolated hearts from rats were subjected to 30-min ischemia followed by 60-min reperfusion.Totally 40 isolated hearts were randomly assigned to four groups （n =10/group）：time control group,I/RI group,SevoPoC group,and DRIPC group.The effect of SevoPoC （3% v/v） and DRIPC were observed.Myocardial infarct size （IS）,cardiac troponin I level,and heart function were measured.The protein and messenger RNA levels of LTCCs,RyR2,and NCX1 were determined.Results：Both SevoPoC and DRIPC improved the recovery of myocardial function,and reduced cardiac troponin Ⅰ release after I/RI.The decrease in IS was more significant in the SevoPoC group than that in the DRIPC group （16.50% ± 4.54% in the SevoPoC group [P =0.0006],and 22.34% ± 4.02% in the DRIPC group [P =0.0007] vs.35.00% ± 5.24% in the I/RI group,respectively）.SevoPoC,but not DRIPC significantly inhibited the activity of NCX 1 （0.59 ＋ 0.09 in the I/RI group vs.0.32 ± 0.16 in the SevoPoC group,P =0.006;vs.0.57 ± 0.14 in the DRIPC group,P =0.072）.No statistical significant differences were observed in the expression of LTCCs and RyR2 between SevoPoC and DRIPC.In addition,subsequent correlation analysis showed a significantly positive relationship between the cardiac troponin Ⅰ level and the protein expression ofNCX1 （r =0.505,P =0.023）.Conclusion：SevoPoC may be more effective in the cardioprotection than DRIPC partly due to the deactivation of NCX1.