Sympathectomy-like effects of brachial plexus block in arteriovenous access surgery

We used color Doppler ultrasonography to prospectively study the effects of supraclavicular brachial plexus block (BPB) on blood flow and vein diameter in patients undergoing arteriovenous access surgery. BPB might produce a sympathectomy-like effect that could have a role in improving patencty. Thirty-one consecutive patients who underwent arteriovenous access surgery with BPB were studied prospectively, in addition to 5 patients with BPB having other operations and 5 patients undergoing general anesthesia for elective surgery. Vessel diameter and pulsatility index (PI) were among the parameters measured. Mean PI decreased from 6.18 ± 1.67 before the block to 3.92 ± 1.75 at 10 min after initiation of the block (p=0.001). Basilic vein diameter increased from 6.28 ± 0.86 mm (range 4.85 to 7.30) before the block to 7.83 ± 1.52 mm (range 5.80 to 12.14) 10 min after the block (p = 0.03). In the general anesthesia control group the PI decreased, but returned to preanesthetic levels immediately after the patients reached the recovery room. In the nonaccess BPB group the PI remained low after the block for at least 5 h. Brachial plexus block causes significant venous dilation and a significant decrease in the pulsatility index. This appears to be due to a beneficial sympathectomy-like effect of the block that might prevent early failure and improve patency in vascular access surgery.