Ojective To compare different vasopressor response to commonly used vasoconstrictors, ephedrine, phenylephrine and norepinephrine, when combined with dexmedetomidine during prone position surgery under general anesthesia. At the same time we focused on other hemodynamic parameters changes.
Methods Sixty-six patients undergoing elective lumbar spine surgery in prone position under general anesthesia, 25 males and 41 females, aged 26 - 64 years, BMI 18.5 - 24.9 kg/m2, falling into ASA physical status Ⅰ or Ⅱ, were enrolled in this study. The protocol of induction and maintenance of general anesthesia were identical in three groups. A bolus of 0.4 μg/kg dexmedetomidine was given 10 min prior to anesthesia induction, after that, dexmedetomidine was infused at 0.2 μg·kg-1·h-1. During surgery, when their MAP dropped more than 20% off the base level, or SBP decreased to lower than 95 mmHg , patients would be randomised to receive an intravenous ephedrine 0.1 mg/kg (group DE, n = 22), phenylephrine 1 μg/kg (group DP, n = 23) or norepinephrine 0.06 μg/kg (group DN, n = 21). Physiological variables recorded included mean arterid pressure (MAP), heart rate (HR), central venous pressure (CVP), cardiac output (CO), systemic vascular resistence (SVR) and stroke volume variation (SVV). The hemodynamic changes were measured immediately prior to ephedrine, phenylephrine or norepinephrine administration (T0), 1 min after administration (T1), 3 min after administration (T2), 5 min after administration (T3), 7 min after administration (T4), 9 min after administration (T5).
Results Compared with T0, a significant increase in MAP was observed in group DE at T1 - T5 (P < 0.05), in group DP at T1 - T4 (P < 0.05) and in group DN at T1 - T2 (P < 0.05). Compared with T0, groups DE, DP and DN elevated MAP maximum by (29.8 ± 12.4)%, (38.4 ± 12.7)% and (23.6 ± 10.0)%, respectively. Compared with T0, ephedrine produced a significant increase in the HR at T1 - T5 (P < 0.05). In group DP, HR had a tendancy of slowing down at T1 - T3 (P < 0.05). A bolus injection of ephedrine caused significant increase in cardiac output from T1 - T5 (P < 0.05). The magnitude of the increment of CO in group DE was higher than that of group DP and group DN (P < 0.05), while it showed no significant percentage changes between group DP and group DN.
Conclusion To reverse intraoperative hypotention correlated with compression of inferior vena cava, increased systemic vascular resistance and an increase in parasympathetic activity under general anesthesia in prone position, phenylephrine, norepinephrine and ephedrine can all increase blood pressure rapidly when combined with dexmedetomidine in lumbar spine surgery. Accompanied by increasing cardiac output significantly, bolus ephedrine will produce a more persistent pressor response than that of norepinephrine and phenelypherine. |
