BACKGROUND: Crystalloids are commonly heated in microwave ovens for intravenous or subcutaneous usage (e.g., in liposuction). However, few studies have empirically determined the parameters for this procedure. This study experimentally evaluated the heating of saline solution (sodium chloride 0.9%) at different initial temperatures to derive an equation to calculate heating parameters as well as the temperature decrease in saline solutions after heating. METHODS: The initial temperature of intravenous pouches containing saline solution (500 and 1,000 mL) was adjusted to 15°C, 20°C, or 25°C. The 500 and 1,000 mL pouches were then warmed in a microwave (900 W) for 60 and 120 seconds, respectively. The temperature of the saline solution was measured during heating and immediately and 30 minutes after heating. An equation was derived from the results. RESULTS: Warming the 500 and 1,000 mL pouches for 60 and 120 seconds, respectively, at 900 W increased the temperature of these pouches by 20°C. The derived equation was as follows: final temperature = initial temperature + [0.165 × time (s)/volume (L)]. No significant differences were found between the internal and external temperatures of the pouches after heating. CONCLUSIONS: Determining the initial temperature of crystalloid solutions is essential for obtaining the desired temperature after microwave warming. The equation derived in the present study enables calculation of the final temperature of solutions with various initial temperatures. The external temperature of the pouches accurately reflects their internal temperature.
Hypothermia; Microwaves; Parenteral infusions
