Influence of isoflurane and propofol on gastric slow wave patterns and pacing efficacy in pigs

Background and purpose: Gut motility is partly driven by underlying rhythmic electrical activity called slow waves. The origin and propagation of these electrical events are studied extensively in anesthetized animal models. However, the effects of anesthesia on slow waves remain unclear. This study examined how propofol and isoflurane influence spatiotemporal features of slow waves, anterior-posterior coupling, and the efficacy of gastric pacing. Methods: Nine pigs were anesthetized sequentially with propofol and isoflurane, and baseline electrical activity was measured using high-resolution surface-contact electrode arrays placed on the anterior and posterior gastric serosa. Following baseline recordings, pacing was applied to assess its effects. Slow wave propagation patterns were quantified and the efficacy of spatial entrainment during pacing was compared under propofol and isoflurane. Results: Propofol exhibited antegrade propagation with 86% symmetry between anterior and posterior gastric surfaces, whereas isoflurane reduced symmetry to 25% (p=0.0187) with propagation patterns frequently changing. Slow wave period (18.8±5.1 vs 28.1± 14.3 s, p=0.016), amplitude (1.5±0.7 vs 0.7±0.4 mV, p=0.002), and speed (4.4±1.1 vs 3.5±0.7 mm/s, p=0.018) differed significantly between anesthetic groups at baseline, while only amplitude and speed differed during pacing. Spatial entrainment success was higher with propofol (83%) than isoflurane (57%), but pacing effects remained localized to the paced surface without propagation across the greater curvature. Conclusion: Isoflurane induced more gastric dysrhythmias than propofol, making propofol preferable for studying normal activity and isoflurane preferred for investigating therapies. The uncoupling of anterior and posterior surfaces suggests a potential electrical barrier at the greater curvature, warranting further investigation.