The Utilization of Chemical "Hard Warmers" and Multiple Insulation Methods for Warming of Normal Saline in Cold Environment Background.-It has been reported that chemical "hand warmers" can be utilized to warm intravenous (IV) normal saline (NS) for use in rewarming of hypothermic patients. The suggested fluid temperatures range from 37ยฐC to 41ยฐC.
Objectives.-The objectives of this prospective, interventional study are to determine the maximum temperature achieved, time to maximum temperature, and efficacy of insulation in warming NS.
Methods.-The study was performed in February 2010 in downstate New York. Twelve 1-L IV NS bags were cooled to 3ยฐC and divided into 4 warming groups: (1) wrapped with 8 Grabbers (Grand Rapids, MI) 7-hour hand warmers secured by duct tape; (2) wrapped with 3 Grabbers Peel N' Stick Adhesive body warmers; (3) duct tape/8 hand warmers with foil blanket insulation; (4) duct tape/8 hand warmers with Ensolite type foam insulation. The Grabbers company reported an average warmer temperature of 57ยฐC. Temperature measurements were taken every 5 minutes with a digital metal probe (Vernier. Beaverton, OR) from each IV bag. The mean temperatures of the 4 groups at 5-minute intervals were used for Mann-Whitney U analysis.
Results.-The study environment temperature was 0ยฐC. The hand warmer/tape group plateaued at 135 minutes with 12.43ยฐC. The adhesive warmer group plateaued at 145 minutes with 13.8ยฐC. The foil insulation group plateaued at 145 minutes with 14.33ยฐC. The Ensolite group plateaued at 145 minutes with 17.63ยฐC. The temperature difference between the warmer/duct tape, adhesive, and foil insulation group did not achieve significance. The temperature difference between the warmer/duct tape and the foam insulation group was significant, p ฯฝ 0.00019.
Conclusions.-Hand warmers failed to quickly or adequately warm IV NS to usable temperature for hypothermia treatment. Use of foam insulation improves heat transfer to the IV NS. Limitations included small sample and only one saline bag volume tested.