Tourniquet application after local forearm warming to improve venodilation for peripheral intravenous cannulation in young and middle-aged adults: A single-blind prospective randomized controlled trial

BackgroundLocal forearm warming before tourniquet application is often used to promote venodilation for peripheral intravenous cannulation; however, few studies have compared the effect of tourniquet application with and without local warming on vein size.ObjectiveTo evaluate the effectiveness of tourniquet application after local forearm warming with that of tourniquet application alone in young and middle-aged adults.DesignA single-blind, prospective, parallel group, randomized controlled trial.SettingA national university in Japan.ParticipantsSeventy-two volunteers aged 20–64 years.MethodsParticipants were randomly allocated to one of two groups: tourniquet application for 30 s after forearm application of a heat pack warmed to 40 °C ± 2 °C for 15 min (active warming group; n = 36) or tourniquet application for 30 s after applying a non-warmed heat pack for 15 min (passive warming group; n = 36). The primary outcomes were vein cross-sectional area on the forearm, measured after the intervention by blinded research assistants using ultrasound. Secondary outcomes were shortest diameter, and longest diameter of vein on the forearm, forearm skin temperature, body temperature, pulse, systolic blood pressure, and diastolic blood pressure. All outcomes were assessed at the same site before and immediately after the intervention, once per participant.ResultsVein cross-sectional area, shortest vein diameter, and longest vein diameter were significantly increased in the active warming group compared with the passive warming group (p < 0.01). Tourniquet application after local warming was superior to tourniquet application alone in increasing vein cross-sectional, shortest diameter, and longest diameter (between-group differences of 2.2 mm², 0.5 mm, and 0.5 mm, respectively), and in raising skin temperature (between-group difference: 5.2 °C). However, there were no significant differences in body temperature, pulse, or systolic or diastolic blood pressure between the groups. There were no adverse events associated with either intervention.ConclusionTourniquet application after local warming was associated with increased forearm vein size when compared with tourniquet application alone, and was demonstrated as being safe. Thus, with demonstrable effects on vein size, we recommend local warming before tourniquet application as a safe and effective technique for improving venodilation.