Effect of cold marble application for vascular access in obese patients: a randomized controlled trial

Background: Peripheral intravenous (IV) cannulation in obese patients is often more painful and may trigger a stronger autonomic response because of difficult venous access and higher sympathetic tone. Cervical cold stimulation is a simple, non-pharmacological maneuver that may enhance vagal activity and modulate pain perception. This study aimed to determine whether brief bilateral cold marble application to the lateral neck can reduce cannulation pain and blunt hemodynamic changes in obese patients. Methods: In this prospective, randomized, controlled trial, 180 obese adults scheduled for elective surgery were enrolled; 169 patients were included in the final analysis. Patients were randomized into three groups: no intervention (Control), bilateral room-temperature marble application (RTM), or bilateral cold marble application at 4°C (CM). The marble was applied over the lateral cervical region for 30 seconds immediately before IV cannulation. Cannulation was performed by a blinded anesthesiologist using a 22-gauge catheter. The primary outcome was cannulation pain assessed by a 10-cm numeric rating scale (NRS). Secondary outcomes were changes in heart rate (HR) and blood pressure. Results: Baseline demographic and hemodynamic variables were similar among groups. Cannulation pain showed a significant between-group difference (P < 0.001): mean NRS was 4.9 ± 1.8 in the Control group, 4.3 ± 1.7 in the RTM group, and 3.5 ± 1.6 in the CM group, indicating the greatest analgesic effect with cold application. The proportion of patients reporting mild pain (NRS ? 3) was highest in the CM group. HR response also differed: HR increased after cannulation in the Control (+2.4 ± 4.2 bpm) and RTM (+2.7 ± 4.4 bpm) groups, whereas it slightly decreased in the CM group (–1.1 ± 3.8 bpm), consistent with attenuation of the autonomic response. Blood pressure changes were small and clinically insignificant in all groups. No adverse events related to the intervention were observed. Conclusion: A 30-second bilateral cold marble application to the lateral cervical region is an easy, inexpensive, and safe technique that reduces IV cannulation pain and blunts the heart rate response in obese patients. This maneuver can be readily integrated into routine practice, particularly in bariatric and anxious populations, to improve procedural comfort. Abbreviations: CM: cold marble, IV: intravenous, bpm: beats per minute, NRS: Numerical Rating Scale. RTM: room-temperature marble application,.