Survival analysis for respiratory failure in patients with food-borne botulism

Aminopyridines Restore Ventilation and Reverse Respiratory Acidosis at Late Stages of Botulism in Mice

Botulinum neurotoxin (BoNT) is a potent protein toxin that causes muscle paralysis and death by asphyxiation. Treatments for symptomatic botulism are intubation and supportive care until respiratory function recovers. Aminopyridines have recently emerged as potential treatments for botulism. The clinically approved drug 3,4-diaminopyridine (3,4-DAP) rapidly reverses toxic signs of botulism and has antidotal effects when continuously administered in rodent models of lethal botulism. Although the therapeutic effects of 3,4-DAP likely result from the reversal of diaphragm paralysis, the corresponding effects on respiratory physiology are not understood. Here, we combined unrestrained whole-body plethysmography (UWBP) with arterial blood gas measurements to study the effects of 3,4-DAP, and other aminopyridines, on ventilation and respiration at terminal stages of botulism in mice. Treatment with clinically relevant doses of 3,4-DAP restored ventilation in a dose-dependent manner, producing significant improvements in ventilatory parameters within 10 minutes. Concomitant with improved ventilation, 3,4-DAP treatment reversed botulism-induced respiratory acidosis, restoring blood levels of CO2, pH, and lactate to normal physiologic levels. Having established that 3,4-DAP-mediated improvements in ventilation were directly correlated with improved respiration, we used UWBP to quantitatively evaluate nine additional aminopyridines in BoNT/A-intoxicated mice. Multiple aminopyridines were identified with comparable or enhanced therapeutic efficacies compared with 3,4-DAP, including aminopyridines that selectively improved tidal volume versus respiratory rate and vice versa. In addition to contributing to a growing body of evidence supporting the use of aminopyridines to treat clinical botulism, these data lay the groundwork for the development of aminopyridine derivatives with improved pharmacological properties. SIGNIFICANCE STATEMENT: There is a critical need for fast-acting treatments to reverse respiratory paralysis in patients with botulism. This study used unrestrained, whole-body plethysmography and arterial blood gas analysis to show that aminopyridines rapidly restore ventilation and respiration and reverse respiratory acidosis when administered to mice at terminal stages of botulism. In addition to supporting the use of aminopyridines as first-line treatments for botulism symptoms, these data are expected to contribute to the development of new aminopyridine derivatives with improved pharmacological properties.

Early recovery of botulism: one decade of experience

BACKGROUND

Botulism is a rare but serious disease, which appears in different forms. In this study, we reviewed the clinical features, laboratory data, and outcomes of patients who referred to our tertiary center.

MATERIALS AND METHODS

All confirmed cases of botulism referred to an academic referral center and a teaching hospital during 2009-2019, were retrospectively reviewed.

RESULTS

Fifty-three cases of clinical or laboratory-confirmed botulism were examined in this study. Nineteen patients were confirmed by laboratory data (serotype A (89.5%) and serotype E (10.5%)). In seven cases, the cause of botulism was unclear. In two patients, systemic symptoms emerged after the therapeutic injection of botulinum neurotoxin. The majority of cases (83%) were caused by an obvious food source. In 66% of cases, the initial symptoms emerged within less than 36 h, while in 20.8% of cases, the symptoms developed within or after 36 h; however, in seven patients that their botulism sources were unclear, the onset could not be estimated. All patients showed cranial involvement and generalized manifestation, and 49.1% had gastrointestinal symptoms. Except for two patients who were not treated due to immediate drug reactions who manifested severe hemodynamic instability, the rest of the patients were treated with trivalent antitoxin (A, B, and E). The complete resolution of the symptoms during hospitalization was documented in 50.9% of the patients. About 17% of the patients were intubated. Two patients died due to massive bilateral pulmonary thromboembolism and cardiac asystole following respiratory failure.

CONCLUSIONS

Although the complete resolution of the symptoms usually takes several weeks, in our experience, most patients showed at least partial resolution upon discharge. Early treatment results in better outcomes.

Practical approach to respiratory emergencies in neurological diseases

Many neurological diseases may cause acute respiratory failure (ARF) due to involvement of bulbar respiratory center, spinal cord, motoneurons, peripheral nerves, neuromuscular junction, or skeletal muscles. In this context, respiratory emergencies are often a challenge at home, in a neurology ward, or even in an intensive care unit, influencing morbidity and mortality. More commonly, patients develop primarily ventilatory impairment causing hypercapnia. Moreover, inadequate bulbar and expiratory muscle function may cause retained secretions, frequently complicated by pneumonia, atelectasis, and, ultimately, hypoxemic ARF. On the basis of the clinical onset, two main categories of ARF can be identified: (i) acute exacerbation of chronic respiratory failure, which is common in slowly progressive neurological diseases, such as movement disorders and most neuromuscular diseases, and (ii) sudden-onset respiratory failure which may develop in rapidly progressive neurological disorders including stroke, convulsive status epilepticus, traumatic brain injury, spinal cord injury, phrenic neuropathy, myasthenia gravis, and Guillain-Barré syndrome. A tailored assistance may include manual and mechanical cough assistance, noninvasive ventilation, endotracheal intubation, invasive mechanical ventilation, or tracheotomy. This review provides practical recommendations for prevention, recognition, management, and treatment of respiratory emergencies in neurological diseases, mostly in teenagers and adults, according to type and severity of baseline disease.

Efficacy of Antitoxin Therapy in Treating Patients With Foodborne Botulism: A Systematic Review and Meta-analysis of Cases, 1923-2016

Background

Botulism is a rare, potentially severe illness, often fatal if not appropriately treated. Data on treatment are sparse. We systematically evaluated the literature on botulinum antitoxin and other treatments.

Methods

We conducted a systematic literature review of published articles in PubMed via Medline, Web of Science, Embase, Ovid, and Cumulative Index to Nursing and Allied Health Literature, and included all studies that reported on the clinical course and treatment for foodborne botulism. Articles were reviewed by 2 independent reviewers and independently abstracted for treatment type and toxin exposure. We conducted a meta-analysis on the effect of timing of antitoxin administration, antitoxin type, and toxin exposure type.

Results

We identified 235 articles that met the inclusion criteria, published between 1923 and 2016. Study quality was variable. Few (27%) case series reported sufficient data for inclusion in meta-analysis. Reduced mortality was associated with any antitoxin treatment (odds ratio [OR], 0.16; 95% confidence interval [CI], .09-.30) and antitoxin treatment within 48 hours of illness onset (OR, 0.12; 95% CI, .03-.41). Data did not allow assessment of critical care impact, including ventilator support, on survival. Therapeutic agents other than antitoxin offered no clear benefit. Patient characteristics did not predict poor outcomes. We did not identify an interval beyond which antitoxin was not beneficial.

Conclusions

Published studies on botulism treatment are relatively sparse and of low quality. Timely administration of antitoxin reduces mortality; despite appropriate treatment with antitoxin, some patients suffer respiratory failure. Prompt antitoxin administration and meticulous intensive care are essential for optimal outcome.

Disorders of the Diaphragm

Pathologic processes that involve the central nervous system, phrenic nerve, neuromuscular junction, and skeletal muscle can impair diaphragm function. When these processes are of sufficient severity to cause diaphragm dysfunction, respiratory failure may be a consequence. This article reviews basic diaphragm anatomy and physiology and then discusses diagnostic and therapeutic approaches to disorders that result in unilateral or bilateral diaphragm dysfunction. This discussion provides a context in which disorders of the diaphragm and their implications on respiratory function can be better appreciated.

Early diagnosis and treatment in a child with foodborne botulism

INTRODUCTION

Foodborne botulism is a neuroparalytic disease caused by ingestion of food contaminated with botulinum toxins. Despite rare the mortality rate is high if untreated. Diagnosis of botulism is still a challenge for clinician, due to the variability of clinical manifestations and disease course. We report on a child with type B botulin intoxication who was early diagnosed and treated underlining that clinical suspicion is crucial to start prompt treatment.

CASE PRESENTATION

An 11-year-old boy presented with bilateral ptosis and mydriasis, dry mouth, difficulty in swallowing, dysphonia, urine retention and constipation. Clear sensorium and no fever were observed. Immediately the suspicion of botulism was risen and botulinum antitoxin was administered. 3 days later serum and rectal samples tested positive for Clostridium botulinum. The patient completely recovered when discharged from hospital.

DISCUSSION

Foodborne botulism is still possible in developed countries. The confirmation test of botulism requires some days. To avoid long delays between intoxication and diagnosis prompt clinical suspicion is thus crucial. The outcome depends on rapid implementation of appropriate management with intensive respiratory care and antitoxin administration.

Botulinum toxin B increases intrinsic muscle activity in organotypic spinal cord-skeletal muscle co-cultures

In organotypic spinal cord-skeletal muscle co-cultures, motoneurons are driven by locomotor commands and induce contractions in surrounding muscle fibres. Using these co-cultures, it has been shown that effects of organophosphorus compounds on neuromuscular synapses can be determined in vitro. In the present study we aimed to extend this in vitro tool for pharmacologic testing of botulinum toxin B. This neurotoxin is widely used for the treatment of dystonia. Besides its effects on the neuromuscular junction, botulinum toxins may also act at centrally located synapses. Incubation with botulinum toxin B (Neurobloc(®)) induced a significant increase in muscular activity after 24, 48 and 72h. Application of the NMDA- and AMPA-receptor antagonists AP5 (20μM) and CNQX (15μM) induced a similar augmentation of muscle activity after 48 and 72h, respectively. Administration of the glycine- and GABA(A)-receptor antagonists strychnine (1μM) and bicuculline (100μM) did not alter intrinsic muscle activity. In contrast, application of a non-depolarizing muscle relaxant rocuronium bromide reduced the muscle activity in a dose-dependent manner. Our findings suggest that glutamatergic synapses in the spinal cord are more sensitive to botulinum toxin B than synaptic contacts between spinal motoneurons and muscle fibres.