Impedance cardiography of interscalenous brachial plexus blockade

Abstract

Background and aims: Haemodynamic changes are possible due to changes in body positioning and reflectory reactions of autonomic nervous system during the shoulder surgery under the ISB. The distribution of sympathetic fibres to pacemaker tissues of the sinoatrial node, which regulate HR, varies considerably between the right and left sympathetic pathways: most fibres are carried by right stellate cardiac nerves, whereas there is only a sparse supply from the left stellate cardiac nerves. Left-sided structures predominantly innervate the atrioventricular node. The goal was to test hypothesis that haemodynamic changes assessed by impedance cardiography are not comparable in right and left sided ISB. Methods: We prospectively examined 81 consecutive patients undergoing shoulder surgery under ISB and assigned to one of two groups depending on the operated side. Patients received a single-injection ISB. Central circulatory variables were assessed by Impedance Cardiography Test. The data was measured before and after the ISB, after the patient was placed in a beach-chair position, and every 10 minutes during the first hour of the surgery. Recorded haemodynamic variables: BP, HR, SI, CO, CI, SVR, ACI. Data were analyzed using ANOVA. Results: The absence of significant differences in the data on the two groups indicate that the changes in hamodynamic parameters were the same for both groups. However, statistically significant changes were observed for both groups in certain time perids when compared with the parameter before the ISB. Conclusion: No statistically significant differences were revealed between the groups. Statistically significant changes were revealed compared to variables before the ISB.