Pre-cooling for Reducing Pain from Local Anesthetic Injections for Hemorrhoidectomy: An Open-label, Randomized, Crossover Trial.

ABSTRACT

Objectives: Excisional hemorrhoidectomy (EH) is sometimes same-day surgery under local anesthesia (LA); however, the LA injection can be painful. We conducted an open-label, crossover, randomised controlled trial to evaluate the efficacy and safety of pre-cooling in reducing pain associated with LA injection. Methods: Patients aged ≥ 20 years undergoing bilateral EH were randomly assigned to 1 of 2 pre-cooling sequences a cooling-first sequence and a cooling-second sequence. In the first intervention phase, 2 minutes of pre-cooling was applied before LA injection in patients randomized to the cooling-first sequence; patients in the cooling-second sequence were asked to wait for 2 minutes (without pre-cooling) before LA injection. The pre-cooling sequences and the perianal sides targeted for injection were reversed in the second intervention phase. The primary outcome was the visual analogue scale (VAS) rating for pain from LA injection, which was obtained twice for each patient. Adverse events due to pre-cooling (e.g., skin disorders) were documented. Results: Of 114 screened patients, 51 were randomized to the cooling-first (n = 26; analyzed n = 26) or cooling-second sequence (n = 25; analyzed n = 25). The 2-minute pre-cooling was completed by 48 patients (94%). VAS scores for LA injection pain decreased significantly with pre-cooling compared to without (difference estimate, -1.71; 95% confidence interval, -2.12 to -1.31; p< 0.001). No adverse events were reported. Conclusions: Two minutes of skin pre-cooling effectively and safely reduces LA injection pain in patients undergoing EH.