Thoracic bioimpedance during extradural anesthesia - Effect of different hydroxyethyl starch solutions on stroke volume under sympatholysis

Objective: Alteration of stroke volume index (SI, ml/m(2)) during extradura l anesthesia (EDA) by infusion of different hydroxyethyl starch solutions ( HES) before induction of EDA. Design and Setting: Randomized, clinical stud y. Patients: 40 patients (mean age 65.3 years) undergoing EDA (extent of an algesia: Th 9-Th 7) for transurethral procedures. Before induction of EDA 1 0 patients in each group were infused with 500 ml 6% HES (A: 450/0.7; B: 20 0/0.5; C: 70/0.5) or with 500 mi Ringer's lactate (D) within 15 min. Interv entions: Measurement of heart rate (HR) and SI by thoracic bioimpedance and mean arterial pressure (MAP, mmHg) by oscillometry.:Results: Decreases of SI, MAP and HR induced by sympathicolysis were observable in all patients. Compared with the values before infusion (mean difference +/- SD), SI and M AP decreased significantly (p < 0.05) in group C (SI: 6.7 +/- 3.1 ml/m(2), MAP: 25.5 +/- 13.0 mmHg) as well as in group D (SI: 9.5 +/- 3.6 ml/m(2), MA P: 25.5 +/- 9.0 mmHg) 120 min after induction of EDA. In group A and B the decreases of SI and MAP were not significant. Conclusions: The infusion of middle- or high-molecular HES before induction of EDA are positively effecting the SI and MAP decrease induced by sympath icolysis. Thus, middle- and high-molecular HES can reduce the cardiocircula tory side effects of sympathicolysis.