[Sudden infant death--an emotional trigger mechanism]

Southall and coworkers have demonstrated in a recent study that attacks of lifelessness with sudden and severe hypoxemia and cyanosis are caused by a combination of respiratory arrest in expiration, and a right-to-left shunting of the blood through the lungs due to increased pulmonary vascular resistance. This mechanism is thought to be the cause of death. They have also defined the precipitating factors which are sudden, naturally occurring stimuli causing fear, anger or pain. They underline the importance of elements of surprise and unexpectedness. These observations lend strong support to the "fear paralysis" hypothesis proposed in 1986 by Kaada and Gabrielsen. We stressed that the process leading to death was triggered on by emotional factors (first and foremost fear). Stimuli evoking fear are any threat perceived as a danger. Actual stimuli in infants are restrained movement, sudden and unexpected noises, sudden exposure to strange environments and persons. Elements of surprise and novelty were similarly emphasized. The reflex is suppressed by the administration of anxiolytic drugs like clonidine and amitriptyline.