Introduction: gastrointestinal stasis is a common painful syndrome in pet rabbits, related to their digestive system features, whose treatment is based on opioids administration associated with fluid therapy and progressive refeeding. Methods: the aim of this study was to analyse the effects of this condition and its antalgic treatment on cardiac rhythm using electrocardiogram tracings. For this purpose, rabbits with gastro-intestinal stasis were prospectively recruited (Stasis group) and compared with healthy rabbits receiving or not receiving opioids (Healthy with/without opioids groups). Results: a total of 51 rabbits were included in the study, i.e., Stasis group (n=14), Healthy with opioids group (n=13), and Healthy without opioids group (n=24). A significant increase in QT interval (p<0.01) was observed in the two groups receiving opioids, and the mean maximum heart rate was higher in the Stasis group (250±33 beats per minute) than in the Healthy with opioids group (223±26 beats per minute). Heart rate variability evaluated using the vasovagal tonus index was not different between the groups, however other indicators of heart rate variability such as the mean variability of the duration of 20 successive R-R intervals was increased by 2.4% in the Healthy group receiving opioids, as compared with the Healthy without opioids group. In the Stasis group, very marked gastric dilation was significantly associated with sinus pauses, as compared with other groups (p=0.04). Conclusion: electrocardiogram, and especially heart rate can be influenced by opioids administration and probably by pain during the management of gastrointestinal stasis syndrome in hospitalisation.