Suppression of pentylenetetrazol-elicited seizure activity by intraosseous propranolol in pigs

Epilepsy and sudden death: personal reflections and call for global action

To solve the mystery of sudden unexpected death in persons with epilepsy (SUDEP), a global focus is needed to identify persons at risk, develop treatment regimens, and prevent its occurrence. A world wide network of professionals must focus on basic scientific research programs and clinical and epidemiology studies. Team work among different multidisciplinary professionals in clinical settings and within and among laboratories should address the global issues of SUDEP. If the correct term 'SUDEP' is used on autopsy reports and if verbal autopsies postmortem are conducted when needed, the true incidence of SUDEP may be found to be much higher than previously thought and the market for new antiepileptics and other drugs to prevent SUDEP will be larger. Symposia should discuss new data and lessons learned from the last 20 to 30 years to be applied by scientists and clinicians worldwide to gain a better understanding of SUDEP. 'Think out of the box' when evaluating an established animal model with potential for modification(s) to study mechanism(s) of SUDEP. Multiple relevant animal models are needed to understand the pathophysiology of SUDEP, hypothesize about effective treatments, develop small pilot studies in persons with epilepsy, and conduct confirmatory large-scale clinical trials. The fields of pharmacology, clinical pharmacology, and cardiology have much to offer as we work to improve compliance, develop new antiepileptic drugs, and apply different categories of drugs to resolve the mystery of SUDEP. Ambulatory simultaneous EKG and EEG telemetry monitoring of patients at risk for sudden death will help identify cardiac vs. brain epileptogenic triggers for treatment to decrease risk of SUDEP. Respiratory function monitoring is also needed. Academic fellowships and competitions for medical students, postdoctoral fellows, residents and faculty will attract medical and graduate trainees to work on SUDEP. Grant funding is essential to move the SUDEP knowledge base forward. Leaders must solve the global mystery of SUDEP using a leadership philosophy foundation that provides innovative vision and approaches for SUDEP research and teaching programs. The interaction of teaching and research is essential: while a student is learning how to conduct research he must simultaneously learn to become a teacher. Medical and graduate leaders must provide vision and a fertile environment to teach students of today to become the self learners and leaders of tomorrow to find solutions for SUDEP.

The mystery of sudden death: mechanisms for risks

This review addresses the possible overlapping mechanisms that may apply to the risk of sudden unexpected death occurring in epilepsy and in cardiac disease. It explores the interaction between the central and peripheral autonomic nervous systems and the cardiopulmonary systems. Included is a discussion of the potential interactive role of genetically determined subtle cardiac risk factors for arrhythmias with a predisposition for seizure-related cardiac arrhythmias. We address the possible mechanisms that are operant in producing both epileptogenic and cardiogenic arrhythmias. Finally, we speculate about potential preventive measures to minimize the risk of both sudden unexpected death in epilepsy and sudden cardiac death.

Clinical pharmacology: drugs as a benefit and/or risk in sudden unexpected death in epilepsy?

Death may be the consequence of natural or unnatural causes, such as accidents, homicide, and suicide, which have no relationship to the disease of epilepsy. Direct causes of death include status epilepticus, and indirect causes may be head trauma or drowning subsequent to a seizure. When death occurs suddenly and without explanation, the term sudden unexpected unexplained death is used. Unexplained is a term that clinicians and research scientists are working to clarify. Numerous preclinical animal studies have been conducted as models for sudden death and have led to clinical studies in persons with epilepsy. These studies show that sympathetic nerve stimulation, ouabain, or coronary occlusion increased temporal dispersion of recovery of ventricular excitability and led to an underlying electrical instability that predisposed the ventricularmyocardium to arrhythmia. Cardiac arrhythmias in an animal model for ouabain-induced toxicity were associated with neural autonomic dysfunction. Neural discharges were characterized by increases, decreases, or no change in the discharge of postganglionic cardiac sympathetic nerves monitored simultaneously, predisposing to cardiac arrhythmia. Stimulation of the sympathetic ventrolateral cardiac nerve produced a shift in the origin of the pacemaker and tachyarrhythmias because the nerve is not uniformly distributed to the various regions of the heart but is localized to the atrioventricular junctional and ventricular regions. Such nonuniform distribution of sympathetic nerves would also contribute to initiation of arrhythmia as a nonuniform neural discharge occurred. Studies examining the physiology and pharmacology of this finding in multiple animal models found that subconvulsant, interictal discharge was associated with autonomic cardiac neural non-uniform discharge and cardiac arrhythmias. As a result of further investigations, Lathers and Schraeder edited a book in 1990 that summarized the clinical problem of sudden unexpected death and epilepsy (SUDEP). The contributors concluded that there was a paucity of clinical data addressing the mechanism of death. Regulatory response resulting from the consequent increased awareness of SUDEP occurred in 1993, when the FDA focused attention of practitioners and pharmaceutical manufacturers on the question of whether use of anticonvulsant drugs contributes to or prevents sudden unexpected death in epileptic persons. The FDA-convened panel of scientists considered the prevalence of sudden unexpected death in patients involved in studies associated with developing new anticonvulsant drugs and reviewed data on the risk of sudden unexpected death in patients taking lamotrigine. The risk of SUDEP was no different from thatfound in the young epilepsy population in general. Estimated SUDEP rates in patients receiving the new anticonvulsant drugs lamotrigine, gabapentin, topiramate, tigabine, and zonisamide were found to be similar to those in patients receiving standard anticonvulsant drugs, suggesting that SUDEP rates reflect population rates and not a specific drug effect. The FDA required warning labels on the risk of SUDEP in association with the use of each of the above-mentioned drugs. Another effect of bringing SUDEP to the attention of epilepsy researchers has been the expansion of basic science and the development of epidemiological and clinical studies directed at this phenomenon. Results from some of these studies are discussed in this article.

Intravenous versus intramuscular midazolam in treatment of chemically induced generalized seizures in swine

Midazolam is a water-soluble benzodiazepine proven to be efficacious in sedation, hypnosis, and induction and maintenance of anesthesia. Because of its water solubility, it is a desirable drug for the control of status epilepticus when intravenous (IV) access is not obtainable. This study compares intramuscular (IM) versus IV routes of administration of midazolam in the control of tonic-clonic activity produced by chemically induced generalized seizures in a swine model. When midazolam was administered by IV route, tonic-clonic activity lasted a mean of 34 +/- 5.4 seconds, and when administered by IM route, the tonic-clonic activity lasted a mean of 116 +/- 41 seconds. Both were considerably abbreviated when compared with the expected duration of pentylenetetrazol-induced seizures in the swine model. Serum levels of midazolam achieved by the IV route were considerably higher than those achieved by the IM route. It is concluded that midazolam is effective in the control of tonic-clonic manifestations of generalized seizures when administered by the IV or the IM route and that no correlation exists between serum levels achieved and the time to control the seizure.

Intraosseous administration of antibiotics: same-dose comparison with intravenous administration in the weanling pig

STUDY OBJECTIVES

To assess the reliability of the intraosseous route of administration for delivery of a loading dose of broad-spectrum antibiotics in a pediatric animal model.

DESIGN

Serum levels achieved within 90 minutes of equivalent intraosseous (IO) and IV bolus dosing of ceftriaxone, cefotaxime, and a combination of ampicillin and gentamicin were compared in the weanling pig.

SUBJECTS

Twelve female weanling pigs were studied in the Animal Facilities Laboratory at the University of Mississippi Medical Center.

INTERVENTIONS

Through a proximal tibial IO catheter, each anesthetized animal received one of the following: 50 mg/kg ceftriaxone, 50 mg/kg cefotaxime, or 300 mg/kg ampicillin followed immediately by 2.5 mg/kg gentamicin. Venous blood was obtained for antibiotic assay at 15, 30, 45, 60, and 90 minutes after IO injection. The animals were allowed to recover, and, after a one-week washout period, each received the same antibiotic and dose as before through a peripheral IV. Levels were assayed at the same intervals and IO versus IV were compared.

MEASUREMENTS AND MAIN RESULTS

Comparable serum levels of all four antibiotics were achieved by the two routes. Gentamicin levels were statistically indistinguishable IO versus IV at all assay intervals. Ampicillin and cefotaxime levels achieved by the two routes were equivalent within one hour of dosing. Serum levels of ceftriaxone after IO administration paralleled those after IV dosing but remained significantly lower at all time intervals.

CONCLUSIONS

In the weanling pig model, the IO route was used to deliver serum levels of broad-spectrum antibiotics comparable to those attained after IV administration. The data support the use of standard parenteral doses for IO administration. To overcome potential avid protein binding of ceftriaxone in the bone marrow, we recommend using ceftriaxone at its highest recommended IO loading dose. Consistent with many other medications that have been similarly tested, these data indicate that initial or empiric antibiotic coverage in hypodynamic and shock states in infants and young children need not await the establishment of traditional IV access.