Effect of dual direct and alternating currents on pain induced by blood sampling and intramuscular injection processes.

Objective: This study investigates the effects of cathodal, anodal, and intermittent electrical stimulation on pain intensity associated with arterial blood sampling, venous blood sampling, and intramuscular injection.

Methods: In a triple-blind clinical trial, 160 patients requiring arterial, venous blood sampling, and intramuscular injection were randomly divided into four groups. Three intervention groups received 5 mA anodal, cathodal direct, or alternating currents during the procedure, while the control group received only a topical eutectic mixture of local anesthetics (EMLA). Pain intensity was measured using the visual analog scale (VAS) immediately after the procedure, while procedure duration, number of attempts, and heart rate changes were recorded as secondary outcome.

Results: All forms of electrical stimulation significantly reduced procedural pain compared to EMLA. Cathodal direct current demonstrated the greatest analgesic effect, with mean VAS score reductions of 2-3 points across all procedures. The time required for arterial blood sampling in the cathodal group was significantly less than with EMLA, while no difference was observed in the procedure time and frequency of attempts in other processes. Furthermore, electrical stimulation groups, particularly the cathodal mode, exhibited lower post-procedure heart rates, suggesting attenuated physiological stress responses.

Conclusion: We found that applying electric currents during the procedure reduces the pain of blood sampling or injections. The greatest analgesia was observed with cathodal direct current stimulation compared to other groups.

Clinical trial registration: Date of registration: 27 January 2024. Clinical Trials.gov Identifier: IRCT20240123060780N1. URL: https://irct.behdasht.gov.ir/trial/75119.