Background.Northern Thailand's biggest botulism outbreak to date occurred on 14 March 2006 and affected 209 people. Of these, 42 developed respiratory failure, and 25 of those who developed respiratory failure were referred to 9 high facility hospitals for treatment of severe respiratory failure and autonomic nervous system involvement. Among these patients, we aimed to assess the relationship between the rate of ventilator dependence and the occurrence of treatment by day 4 versus day 6 after exposure to bamboo shoots (the source of the botulism outbreak), as well as the relationship between ventilator dependence and negative inspiratory pressure.

Methods.We reviewed the circumstances and timing of symptoms following exposure. Mobile teams treated patients with botulinum antitoxin on day 4 or day 6 after exposure in Nan Hospital (Nan, Thailand). Eighteen patients (in 7 high facility hospitals) with severe respiratory failure received a low‐ and high‐rate repetitive nerve stimulation test, and negative inspiratory pressure was measured.

Results.Within 1–65 h after exposure, 18 of the patients with severe respiratory failure had become ill. The typical clinical sequence was abdominal pain, nausea and/or vomiting, diarrhea, dysphagia and/or dysarthria, ptosis, diplopia, generalized weakness, urinary retention, and respiratory failure. Most patients exhibited fluctuating pulse and blood pressure. Repetitive nerve stimulation test showed no response in the most severe stage. In the moderately severe stage, there was a low‐amplitude compound muscle action potential with a low‐rate incremented/high‐rate decremented response. In the early recovery phase, there was a low‐amplitude compound muscle action potential with low‐ and high‐rate incremented response. In the ventilator‐weaning stage, there was a normal‐amplitude compound muscle action potential. Negative inspiratory pressure variation among 14 patients undergoing weaning from mechanical ventilation was observed. Kaplan–Meier survival analysis identified a shorter period of ventilator dependency among patients receiving botulinum antitoxin on day 4 ( ).

Conclusions.Patients receiving botulinum antitoxin on day 4 had decreased ventilator dependency. In addition, for patients with foodborne botulism, an effective referral system and team of specialists are needed.