Impact of arm position compared to tourniquet and general anesthesia on peripheral vein width in supine adult patients: a prospective, monocentric, cross-sectional study.

Background: IV access is a commonly performed procedure that is often taught based on tradition rather than evidence. The effect of arm retroflexion on vein width, either alone or in combination with a tourniquet or general anesthesia (GA), remains unclear. In this case, the sonographically measured vein width is a surrogate parameter for the success of the puncture.

Methods: Prospective, cross-sectional study involving 57 patients scheduled for surgery in general anesthesia. We analyzed the impact of arm retroflexion, tourniquet, general anesthesia, and their combinations on the antebrachial veins in supine patients by ultrasound. Measurements were taken awake and during general anesthesia, each with and without the application of a tourniquet, and in three different arm positions (0°, 30°, and max° retroflexion) each. Data are presented as median and interquartile range [IQR].

Results: Tourniquet application (AT) had the greatest single effect on Cubital vein outer diameter compared to the baseline value of all measures (3.9 mm [3.4-5.1]; 4.8 mm [4.1-5.7], P = 0.001, r = 0.515). This effect was surpassed by the combination of AT and GA (5.1 mm [4.6-6.6], P = 0.001, r = 0.889). In contrast, retroflexion alone did not result in an increase at either 30° (4.2 mm [3.7-5.1], p = 1.0, r = 0.12) or max° (4.2 mm [3.6-4.9], p = 0.72, r = 0.23). With GA and AT, no further enlargement was measurable by 30° (5.4 mm [4.6-6.6], p = 1.0, r = 0.15) or max° (5.4 mm [4.6-6.6], p = 1.0, r = 0.07) retroflexion compared to GA-AT-0° (5.1 mm [4.6-6.6], p = 1.0, r = 0.15).

Conclusions: This study provides evidence that retroflexion of the arm in supine patients, whether alone or in addition to a tourniquet or general anesthesia, does not have any additional effect on vein width as a surrogate parameter for successful IV success. It shows for the first time that general anesthesia effectively increases vein diameter.

Trial registration: DRKS00029603 (date of registration 07.07.2022).