The Preventive Effect Of Continuous Infusion Of Methoxamine On Hypotension During The General Anesthesia In Thoracoscopic Surgery

Objective:To explore the clinical efficacy and safety of preventive continuous infusion and remedial single injection of methoxamine for preventing hypotension during the general anesthesia period in thoracoscopic surgery.Methods:80 ASA I or Ⅱ patients aged 20 to 65 years undergoing elective thoracoscopic surgery under general anesthesia were randomly divided into2 groups : Methoxamine single injection group(Group A, n = 40) and Methoxamine continuous infusion group(Group B, n = 40). Group A had no preventive medication, if SBP dropped more than 20% of baseline, then group A were injected methoxamine 1.5mg. BP was measured again after3 minutes, if SBP still dropped more than 20% of baseline, then group A were injected methoxamine 1.0mg again until SBP returned to within(100±20)% of baseline. Group B was injected methoxamine 1.0mg while the induction, then group B were infused 0.01% methoxamine at the rate of2 ml / kg / h. If SBP dropped more than 20% of baseline, then group B were injected methoxamine 1.5mg. BP was measured again after 3minutes, if SBP still dropped more than 20% of baseline, then group B were injected methoxamine 1.0mg again and while adjusted the infusion rate to 3ml / kg /h, until SBP restored and maintained within( 100±20) % of baseline.Hemodynamic parameters were recorded: systolic blood pressure(SBP),diastolic blood pressure(DBP), heart rate(HR). Recorded anesthesia time, operation time, urine output, blood loss, fluid volume, methoxamine dosage and the number of single injection of methoxamine to correct hypotension.Results:The incidence of hypotension in group A and group B were 40% and15% respectively(P<0.05), the incidence of hypotension were 25% and7.5% respectively during induction period(P<0.05). The number of single injection of methoxamine was lower in group B than in group A(P<0.05),the minimum values of SBP and DBP were higher in group B than in group A(P<0.05).Conclusions:Applying methoxamine is effective to prevent hypotension during the general anesthesia period in thoracoscopic surgery. Comparing with remedial single injection, preventive continuous infusion can reduce the incidence of hypotension significantly and maintain the blood pressure fluctuations <20% of baseline effectively, which hemodynamics is more stable.