Lumbo-sacral epidural anaesthesia as a complement to dissociative anaesthesia during scrotal herniorrhaphy of livestock pigs in the field

How is depth of anaesthesia assessed in experimental pigs? A scoping review

BACKGROUND

Despite the large number of pigs involved in translational studies, no gold standard depth of anaesthesia indicators are available. We undertook a scoping review to investigate and summarize the evidence that sustains or contradicts the use of depth of anaesthesia indicators in this species.

METHODS

Medline, Embase and CAB abstract were searched up to September 22nd 2022. No limits were set for time, language and study type. Only original articles of in vivo studies using pigs or minipigs undergoing general anaesthesia were included. The depth of anaesthesia indicators reported in the selected papers were divided in two categories: A, indicators purposely investigated as method to assess depth of anaesthesia; B, indicators reported but not investigated as method to assess depth of anaesthesia.

RESULTS

Out of 13792 papers found, 105 were included after the screening process. Category A: 17 depth of anaesthesia indicators were found in 19 papers. Studies were conducted using inhalant anaesthetics as the main anaesthetic agent in the majority of the cases (13/19 = 68.4%), while 3/19 (15.8%) used propofol. The most investigated depth of anaesthesia indicators were bispectral index (8/19 = 42.1%) and spectral edge frequency 95% (5/19 = 26.3%). Contrasting results about the specific usefulness of each depth of anaesthesia indicators were reported. Category B: 23 depth of anaesthesia indicators were found in 92 papers. The most reported depth of anaesthesia indicators were: motor response following a stimulus (37/92 = 40.2%), depth of anaesthesia scores (21/92 = 23.3%), bispectral index (16/92 = 17.8%) and spectral edge frequency 95% (9/92 = 9.8%).

CONCLUSION

Results highlight the lack of scientifically valid and reliable indicators to ensure adequate depth of anaesthesia in pigs.

Miniature Companion Pig Sedation and Anesthesia

With their increase in popularity in North America as pets, miniature companion pigs are in need of veterinary professionals familiar with sedation and anesthesia for the species. This article provides a review of the agents used for sedation, premedication, induction, and maintenance of anesthesia for miniature companion pigs. This review also covers species-specific anatomic and physiologic factors of miniature companion pigs with respect to administration of anesthetics, endotracheal intubation, anesthetic maintenance, and common complications so that the reader can make an informed anesthetic plan for the species.

Effect of Cranial Flexion of Pelvic Limbs on Interlaminar Length of the Lumbosacral Space in Sternally and Laterally Recumbent Juvenile Duroc and Adult Yucatan Pigs

Epidural puncture in swine is technically challenging. Several combinations of limb and body positions have been suggested to increase lumbosacral interlaminar space (LSS) and lumbosacral angle (LSA). This study investigated whether cranial hyperflexion of pelvic limbs increased LSS and LSA in laterally and sternally recumbent juvenile Duroc and adult Yucatan pigs and assessed which position produced the largest LSS. Juvenile Duroc (n = 7) and adult Yucatan (n = 7) pigs were euthanized and randomly placed in 4 positions: sternal with neutral limbs, sternal with cranially hyperflexed limbs, lateral with neutral limbs, and lateral with hyperflexed limbs. LSS and LSA were measured on transverse axial CT images of the spine and compared by using multivariate ANOVA and the Student t test. In both age groups, LSS was greater in lateral flexed (juvenile, 7.0 ± 0.7 mm; adult, 15.9 ± 1.1 mm) and sternal flexed (juvenile, 7.5 ± 1 mm; adult, 17.1 ± 1.1 mm) positions than in lateral neutral (juvenile, 5.4 ± 0.9 mm; adult, 9.6 ± 1.6 mm) position. In addition, in both age groups, LSS and LSA in lateral neutral position were smaller than lateral flexed, sternal neutral, and sternal flexed positions. In adults, LSS was greater in lateral flexed and sternal flexed than in sternal neutral position. Hyperflexion of pelvic limbs increases LSS and LSA in sternally recumbent adult Yucatan pigs and laterally recumbent adult Yucatan and juvenile Duroc swine. Increased LSS from positioning pigs with pelvic limbs flexed in sternal or lateral recumbence may facilitate epidural puncture compared with neutral limb positioning.