Hemodynamic changes after interscalene brachial plexus block depending on its side
 
Cesnaitis T., Tamosiunas R., Gelmanas A.

Lithuanian University of Health Sciences, Dept. of Anaesthesiology, Kaunas, Lithuania.
 
Background and Goal of Study:  Interscalene brachial plexus block (ISB) is a first choice method performing shoulder surgery or diagnostic procedures around the world. Despite this common procedure there are still many undesirable events concerning hemodynamic changes. Exact causes are not yet fully determined. The goal of our study is to find how hemodynamics of patient is affected by ISB depending on its side. 

Materials and methods:  We investigated 78 patients, who needed shoulder surgery. All subjects were in sinus rhythm, and no abnormalities were detected with medical history and physical examination. Patient exclusion criteria: refused consent of enrollment in the investigation; coexisting diseases that were likely to impact changes in hemodynamics during the surgery. After obtaining the approval from the Ethics Committee the patients were included randomly into 2 groups depending on operating side. Two equal groups of 39 patients underwent one side ISB. All patients received 0.5% 20 ml bupivacaine and 2% 20 ml lidocaine Ultrasound-Guided ISB. Hemodynamic changes were registered with impedance cardiography test and standard patient monitoring in various periods of operation for the first hour.

Results and discussion:  The patient population included both sexes, median age was 42,3 years with the ASA physical status I and II, weight from 50 to 98 kg and height between 155 and 192 cm. We found statistically significant difference between left and right side block. Left side ISB caused lower cardiac index after 10, 20 and 40 min. Systemic vascular resistance index was lower in every stage after 10 min. Mean blood pressure was lower after positioning the patients, 20, 30 and 60 min. Drop in heart rate was observed after 20 and 40 min. in left side block group. Acceleration index was higher in left side group after 10, 20 and 30 min. There was no statistically significant differences concerning systolic index and cardiac output. ISB has a different effects to hemodynamics depending on the block's side. In respect to our hypotheses, we suggest that left ISB, possibly through extension of block to the stellate ganglion, alters the autonomic outflow to the central circulatory system more than right ISB. 

Conclusion:  Left side ISB has higher influence to hemodynamic changes during left shoulder surgery. To fully investigate the influence of ISB side to hemodynamic changes more studies should be carried out and reviewed systemically to get reliable results.