[A case of amyotrophic lateral sclerosis presenting with circulatory collapse during artificial respiration]

A 71-year-old man developed dysarthria and difficulty of swallowing in December 1997. He was diagnosed as having the bulbar type of amyotrophic lateral sclerosis (ALS). In November 1998, he was admitted to our hospital to undergo treatment for bulbar palsy and respiratory discomfort. In January 1999, ventilatory support (synchronous intermittent mandatory ventilation) during sleep at night was initiated. Severe progressive hypotension and loss of consciousness were observed soon after the start of artificial respiration, and both symptoms disappeared after artificial respiration was discontinued. This phenomenon was observed consistently during ventilatory support, while unpleasant stimuli such as bronchoscopy and replacement of the cannula tube induced severe hypertension. To clarify the mechanism of underlying these abnormal changes in blood pressure, autonomic function tests were performed while awake during the daytime. Ventilatory support induced a drop in blood pressure accompanied by a decrease in influx speed to the right ventriculum, the latter of which suggested a reduction in venous return. These values returned to the baseline following detachment of the ventilator. A 60 degrees head-up tilt (HUT) angle and standing from a supine position produced orthostatic hypotension, the latter of which was accompanied by a compensatory increase in pulse rate. The basal supine plasma noradrenaline (NA) level was high and the HUT showed a slight elevation of NA. The basal supine plasma arginine vasopressin (AVP) level was within the normal range, whereas the AVP level did not increase during HUT. Urinary secretion rates of NA and 3-methoxy-4-hydroxy-phenylglycol were elevated. A cold pressor test demonstrated reflex hypertension. The oculovagal reflex, coefficient of variation of R-R intervals. (CVR-R) and increase in pulse rate in response to atropine administration were within the normal range. The combination of midodrine, L-dihydroxyphenylserine (DOPS) and increasing intravascular volume via continuous intravenous drip infusion relieved the circulatory collapse during artificial respiration. In conclusion, the present case of ALS had sympathetic hyperactivity, somatosympathetic reflex and dysregulation of the baroreflex arc. Degeneration of central autonomic network, including the hypothalamus and the central nucleus of the amygdala, which has been shown in some ALS patients, might underlie the autonomic abnormalities in this patient.