In hypotensive trauma, PIV access succeeds in about two-thirds of attempts, but the odds of success fall with each repeat—making early alternatives worth considering in patients with no measurable blood pressure.

• Across 886 attempts in 471 patients, first-attempt success was 70%; cumulative success reached 83% by the second attempt.
• Among patients still without access, success fell from 70% on the first attempt to 54% on the second and 39% on the third.

A measurable initial systolic pressure was associated with greater PIV success. These observational findings support considering IO or other alternative access after one failed attempt when no blood pressure is measurable; they do not establish a universal cutoff.