Assessing ultrasonographic optic nerve sheath diameter in animal model with anesthesia regimens

Abstract

To determine the normal optical nerve sheath (ONS) diameter ultrasonography (ONSUS) and evaluate the possible effects of drugs on ONS diameter during anesthetic induction in healthy pigs. Methods: Healthy piglets were divided into three groups: a control group, that received xylazine and ketamine (X/K); other that received xylazine, ketamine and propofol (X/K/P); and a third group that received xylazine, ketamine, and thiopental (X/K/T). The sheath diameter was assessed by ultrasonography calculating the average of three measurements of each eye from the left and right sides. Results: 118 animals were anesthetized (49 X/K 33 X/K/P and 39 X/K/T). Mean ONS sizes on both sides in each group were 0.394 ± 0.048 (X/K), 0.407 ± 0.029 (X/K/P) and 0.378 ± 0.042 cm (X/K/T) (medians of 0.400, 0.405 and 0.389, respectively). The ONS diameter varied from 0.287-0.512 cm (mean of 0.302 ± 0.039 cm). For group X/K, the mean diameter was 0.394 ± 0.048 cm. Significant differences in ONS sizes between the groups P and T (X/K/P > X/K/T, p = 0.003) were found. No statistically significant differences were detected when other groups were compared (X/K = X/K/P, p = 0.302; X/K = X/K/T, p = 0.294). Conclusion: Sedation with thiopental lead to significative ONS diameter reduction in comparison with propofol. ONSUS may be useful to evaluate responses to thiopental administration.

Animal models for the study of intracranial hematomas (Review)

“…They were first used as modeling for brain hematomas by Bullock et al in 1984 (61), where ICH was induced by femoral artery cannulation, which provides blood at arterial pressures directly to the brain. Ever since, these animals have been used for different experimental models of brain hematoma, such as autologous blood injection, bacterial collagenase and cerebral balloons (70,(93)(94)(95)(96).…”

“…Studies for ultrasound assessment of the optic nerve sheath diameter ( 34 , 94 ) and transcranial Doppler pulsatility index ( 35 ) have taken advantage of this method because of sudden IHT development. Thus, the balloon model appears to be sufficient for generating oscillations in intracranial pressure measurements as well as for causing an impact on cerebral hemodynamic conditions and valuable for studying the effects of mechanical damage to the brain tissue ( 43 ).…”

“…A few studies compared the index population with appropriate controls ( 56 , 57 , 94 , 104 ). Some studies report the control group to be composed by intact animals, the comparison of different infusions as autologous blood or collagenase, and even the reproduction of ICH with the exclusive insertion of an intracranial canula without any intervention ( 77 , 88 , 93 , 103 ).…”

“…Xi et al ( 57 ) infused the same amount of saline in contrast to different preparations of red blood cells in order to assess brain swelling and the brain blood barrier permeability, also in rats. With distinction from the models described, Azevedo et al ( 94 ) assessed ultrasound of the optic nerve sheath (ONSD) in piglets to observe these animals ONSD standard values and its variation according to different anesthetics infusion. These values also served as references to non-invasive screening for ICH simulation; whereas Friess et al ( 104 ) evaluated neurological multimodal monitoring (ICP, oximetry and microdialysis) in randomized pigs with no-impact rotational traumatic brain injury and no injured instrumented (the same techniques) sham.…”