Glottal Patency during Experimental Cortical Seizures in Piglets

Abstract

Abstract. Objective: Systemically-induced seizures produce glottal airflow obstruction in anesthetized pigs, resulting in hypercapnia and respiratory acidosis. Cortically-induced seizures may be more representative of human seizure disorders. The purpose of this study was to describe glottal area patency (GAP) in piglets during cortically-induced seizures. Methods: Nineteen spontaneously breathing, lightly anesthetized (alphaxalone-alphadolone IV) piglets (aged 10 Ϯ 2 days) were instrumented for recording nasal airflow, subglottic pressure, and electrocorticogram. Glottal visualization was achieved supraglottically using a 1.2-mm fiberoptic scope inserted through the thyrohyoid membrane. Following baseline-control, hypoxic-rebreathing, and new baseline recordings, seizures were induced using subcortical injections of crystalline penicillin G (100,000 units/ injection). Five consecutive-breath representative epochs were digitized from baseline-control, hypoxic-rebreathing, and seizure conditions. For each breath, GAP was measured at the onset of inspiratory pressure, peak of inspiratory effort (Ip), and onset of expiration. Results: The piglets were physiologic at baseline-control and new baseline conditions, and showed expected increases in ventilation and GAP during rebreathing experiments. GAP was maximum at Ip under baseline and rebreathing conditions, but was significantly decreased and airway resistances were increased during seizure conditions (p < 0.05, ANOVA). Conclusions: Generalized seizure activity results in reduced GAP at the peak of inspiratory effort. Increased work of breathing during seizures is created by direct mechanical obstruction at the level of the larynx.

Swine model for translational research of invasive intracranial monitoring

“…Dr. Terndrup and various coauthors described in the late 1980s and mid‐1990s the use of assorted chemoconvulsants, most notably subcortical PCN injection, to demonstrate physiologic changes in vital signs occurring during convulsive activity in pigs (Terndrup et al., 1993, 1994, 1995, 1999; Terndrup & Fordyce, 1995; Leaming et al., 1999). In addition, due to easy glottal access, several glottal parameters were investigated in relation to clinical events (Terndrup et al., 1995; Leaming et al., 1999). Interestingly, the cortical seizure activity was not assessed beyond its presence by a single tungsten wire electrode; therefore, the spatial and temporal variability has not been understood.…”

“…Interestingly, the cortical seizure activity was not assessed beyond its presence by a single tungsten wire electrode; therefore, the spatial and temporal variability has not been understood. Furthermore, they noted vigorous motor seizures with high doses of PCN necessary to evaluate parameters of interest to anesthesiologists (Terndrup et al., 1995, 1999; Leaming et al., 1999). In these studies, subcortical injections of PCN were higher, 100 μl (1,000,000 U/ml) and several injections were used to induce activity (Terndrup et al., 1999).…”

Proposed Mechanism-Based Risk Stratification and Algorithm to Prevent Sudden Death in Epilepsy

“…Laryngospasm has been suspected during seizures in patients or observed postictally, based on findings of stridor and a narrowed airway when attempting to place an endotracheal tube (48) or intensive inspiratory effort (16,49), but ictal laryngospasm is difficult to directly assess in patients or animals [see e.g., (50)(51)(52)]. Pulmonary edema, a common finding at autopsy in SUDEP cases, is also indirect evidence of laryngospasm (53)(54)(55).…”

Intracranial electrophysiological recordings on a swine model of mesial temporal lobe epilepsy

“…However, few studies have investigated pig epilepsy models. The most studied epilepsy model in pigs is the chemical seizure induction with penicillin-triggered epileptogenic activity (12)(13)(14)(15)(16)(17). Penicillin injection results in a focal reduction of GABA-dependent inhibition leading to an increase in excitatory cortical afferents which triggers epileptiform bursts (18).…”