Influence of Different Warming Methods in Rabbits Subjected to Prolonged Pneumoperitoneum

The objective of this study was to evaluate the influence of heated CO₂ and forced-air warming on perioperative temperature in a rabbit model of prolonged pneumoperitoneum.

Thirty-seven New Zealand rabbits, weighing an average of 3.85 kg, were divided into four experimental groups with different warming methods: the control group (CT) underwent unheated pneumoperitoneum (22 °C); another group (HP) underwent pneumoperitoneum with heated CO₂ (36 °C); a third group (FA) underwent unheated pneumoperitoneum but with the use of a forced-air warming device (43 °C) positioned between the animal and the surgical table; and the fourth group of animals (HP + FA) underwent heated pneumoperitoneum with the use of a forced-air warming device. For all animals, the pneumoperitoneum was maintained for 120 min. The animals' temperature was measured immediately before sedation (I0), at the beginning of insufflation (I1, which was mandatory 60 min after I0), every 15 min during pneumoperitoneum (I2-I9), and 15 min after desufflation (I10). The data were analyzed and compared by Student's t-test, ANOVA, Pearson's correlation and linear regression, considering p < 0.05 as significant.

There was no difference between the groups regarding weight, temperature at I0, temperature at I1, volume of CO₂ used, or Δt (I0-I1). In all groups, there was a decrease in temperature when comparing the final instants (I9 or I10) with the initial instants (I0 or I1) of the study (p < 0.05). However, the groups that used the forced-air warming (FA and HP + FA) had a smaller decrease in temperature and a higher final temperature, with no difference between these groups. Furthermore, these groups recovered their temperature better after deflation (from I9 to I10). For all groups, a correlation between time and temperature was observed, but in the groups that used a heated mattress, the slope of the linear regression line was smaller.

The use of a forced-air warming system (combined or not with the use of heated CO₂) reduced the heat loss during prolonged pneumoperitoneum in a small animal model. This warming method is recommended for preventing hypothermia in laparoscopic surgeries with expected prolonged surgical time.