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INTRODUCTION:
Preoperative duplex ultrasound mapping (DUM) of the veins and arteries of the upper extremities is widely accepted to optimize creation of arteriovenous fistulas (AVF) for long term hemodialysis access. Vein diameter is an independent predictor for fistula maturation. A diameter of 2.5 mm has been established as the minimum vein size predictive of fistula success. Based on the preoperative vein size an operative plan is typically established. This study compares the size of veins measured by DUM preoperatively with that obtained after an anesthetic to determine if the anesthetic results in increases in vein diameter and thus changes the operative plan (conversion from graft to fistula, or to a fistula more distal in the upper extremity). A second goal was to determine if a change in plan resulted in a matured access.
METHODS:
Sixty-eight patients were enrolled (July 2013 - December 2014). Preoperative DUM were completed in an accredited vascular laboratory. Intraoperative vein mapping and surgery were performed by 2 board certified vascular surgeons. Intraoperative measurements were performed after an anesthetic (regional or general) at the same levels as preoperative mapping. Access success was determined at routine follow-up appointments. Significance testing was two sided with a significance level of 5%.
RESULTS:
Sixty-eight patients were analyzed. Average age was 57.7 years (range 16-83). There were 47 men (69%) and 21 women (31%). Sixty-five had a regional anesthetic with a supra- or infra-clavicular block; 3 patients had a general anesthetic.
Table one shows that two areas, the intraoperative mid forearm and distal forearm cephalic veins, were significantly larger than the preoperative measurements. Other areas measured were generally larger than the pre-operative DUM but not significant (Table 1).
Thirty-eight of 68 patients (56% of study group) had the pre-operative surgical plan altered based on the repeat intraoperative DUM. Of this group 4 were lost to follow up or underwent transplantation. Of the remaining 34 patients with an intra-operative plan change, 19 (56%) had a more distal fistula created or were converted from a graft to a fistula that matured and was used for dialysis. In 3 of the 34 patients (9%) the intraoperative DUM findings prompted the alteration to a more proximal fistula or conversion to a graft that was successfully used for dialysis. Overall in 22 of the 34 cases (65%) where the plan was changed resulted in an access that was used for dialysis.
CONCLUSIONS:
The use of an intraoperative duplex after an anesthetic resulted in a significant dilation of the forearm cephalic veins and a change in the pre-operative plan in 56% of patients in this study. This suggests that intraoperative DUM is a valuable tool to increase the use of veins that would normally not be used based on their preoperative size, and in over half will result in a functioning access.

Table 1: Vein Sizes

Zone	Pre-op Cephalic in mm (SE)	Intra-op Cephalic in mm (SE)	Delta (SE)	p value
Proximal arm	2.62 (0.20)	2.95 (0.31)	0.33 (0.29)	NS
Mid arm	2.81 (0.20)	3.25 (0.30)	0.44 (0.26)	NS
Antecubital fossa	3.29 (0.20)	3.17 (0.30)	-0.12 (0.30)	NS
Proximal forearm	2.28 (0.15)	2.51 (0.23)	0.27 (0.22)	NS
Mid forearm	1.18 (0.16)	2.14 (0.22)	0.96 (0.19)*	<0.001
Distal forearm (wrist)	1.74 (0.14)	2.23 (0.20)	0.50 (0.16)*	=0.04
NS: not significant *: significant