Short term biological effects of rewarming hypothermic piglets with 915 MHz microwaves

Abstract

In order to determine the short term consequences of rewarming hypothermic piglets with 915 MHz microwave radiation, hypothermia was induced in 14 newborn piglets weighing less that 1.25 kg each. Prior to suckling, the piglets were dried, weighed, and their rectal temperatures recorded. The rectal temperatures were reduced to 25°C by placing the piglets in a 10°C cooling unit following a protocol approved by the University Animal Care Committee. The microwave (MW) generator was programmed to rewarm at a rate of approximately 1.0°C min^-1, while infrared (IR) rewarming was provided by a 250 W IR heating lamp. Piglets were rewarmed to 38°C and then returned to the sow where their temperatures were monitored until 38°C was maintained. Blood samples were taken at birth, after cooling, after rewarming, and at sacrifice. The piglets were sacrificed 48 h after rewarming and dissected for subsequent plasma and tissue analysis. Rewarming time was shorter (P<0.05) for MW than IR rewarmed piglets: 10,75 ± 4,60 y 101,81 ± 7,20 min, respectively. Plasma cortisol levels showed no significant differences (P>0.05) due to treatment within the four sampling times. Cortisol levels between times for each treatment were different (P<0.05). Plasma glucose levels from samples taken at birth, after cooling, and after rewarming were not significantly different between treatment groups. Rewarming treatment did not influence liver glucose and glycogen levels. The percentage area of the adrenal gland zones showed no significant difference (P>0.05) between treatment groups. It was concluded that rewarming hypothermic piglets with 915 MHz MWR does not appear to cause any detrimental effects, thus it may provide a safe and time efficient method for treating piglet hypothermia in a commercial farm situation.