Background: This study investigates the impact of introducing a post-general anesthesia ultrasound (PAUS) mapping on the type of vascular access chosen for hemodialysis in patients without previous accesses. Methods: Two hundred three of 297 consecutive patients met inclusion criteria and were reviewed. Within-subjects analysis was performed on patients with both an outpatient ultrasound-guided vein mapping and a PAUS using sign tests and Wilcoxon signed rank tests. Furthermore, a between-subjects analysis added patients with only the outpatient vein mapping; demographic and comorbidity data were analyzed using t-tests and chi-squared tests. An ordinal logit regression was run for the type of access placed, while a bivariate logit regression was used to compare rates of autogenous access maturation. Results: One hundred sixty-five (81%) patients received both a standard outpatient vein mapping and a PAUS. At the outpatient vein mapping, 130 (79%) patients had suitable veins for an autogenous access, whereas 35 (21%) patients did not have suitable veins for an autogenous access and were planned for a prosthetic access. During PAUS, all 165 (100%) patients were found to have suitable veins for autogenous access formation (P < 0.001). When comparing specific autogenous access configurations, Wilcoxon signed rank testing showed significantly more preferable access configurations in the PAUS group than the outpatient mapping (P < 0.001); outpatient mapping resulted in 81 (47%) radiocephalic accesses, 10 (6%) radiobasilic accesses, 20 (12%) brachiocephalic accesses, 19 (12%) brachiobasilic accesses, and 35 (21%) prosthetic accesses planned, in contrast to 149 (90%) radiocephalic accesses, 3 (2%) radiobasilic accesses, 10 (6%) brachiocephalic accesses, 3 (2%) brachiobasilic accesses, and 0 prosthetic accesses when the same patients were analyzed using PAUS. With the analysis expanded to include the 38 (19%) patients with only the outpatient vein mapping (without-PAUS), the Wilcoxon-Mann-Whitney test showed no significant differences between the groups in terms of outpatient vein mapping plans (P = 0.10); however, when comparing the PAUS plans to the outpatient vein mapping plans, there was again a significantly increased proportion of preferred access types in the PAUS group compared with the outpatient group (P < 0.001). In the ordinal logit multivariate analysis, the only significant variable was the postanesthesia ultrasound, which positively correlated with more favorable access configurations (coefficient = 2.61, P < 0.001). The bivariate logit regression for autogenous access maturation rates found no significant difference between the without-PAUS group and the PAUS group (P = 0.13). Conclusions: Introducing a postanesthesia ultrasound mapping to guide vein-finding significantly increases the quality and quantity of suitable veins found, subsequently leading to increased proportions preferred access placement (autogenous versus prosthetic and forearm versus upper extremity).