TABLE 1.

Baseline Characteristics

Variable	Successful first dose (n = 406)a	Unsuccessful first dose (n = 16)a	P valueb
Age, y	63 (14)	58 (10)	.052
Female	176 (43%)	4 (25%)	.15
BMI	28.6 (5.1)	26.5 (4.9)	.17
ASA score	2.57 (0.59)	2.44 (0.51)	.27
History of spine surgery at same level	63 (16%)	2 (12%)	>.99

ASA, American Society of Anesthesiology; BMI, body mass index.

^aMean (SD); n (%).

^bWilcoxon rank sum test; Pearson χ² test; Fisher exact test.