Short-term variability of blood pressure and heart rate in Guillain-Barre syndrome without respiratory failure

The effect of Guillain-Barre syndrome (GBS) on the short-term variability o f blood pressure and heart rate was evaluated in six patients presenting wi th a moderate form of the syndrome, i.e. unable to stand up unaided and wit hout respiratory failure, at the height of the disease and during recovery. The patients were compared with six age-matched healthy volunteers. During the acute phase of the syndrome, GBS patients exhibited a significant hear t rate elevation (+26 beats/min compared with healthy subjects), but the ac celeratory response to atropine, or to 60 degrees head-up tilt, was maintai ned. Resting plasma noradrenaline levels were high in acute GBS, but the se cretory response to tilt was preserved. Desensitization to noradrenaline wa s observed in acute GBS with a reduced presser action of this cl-adrenocept or agonist. Blood pressure levels were normal and head-up tilt did not indu ce orthostatic hypotension in this moderate form of GBS. Power spectral ana lysis demonstrated marked alterations in cardiovascular variability. The ov erall heart period variability was markedly reduced with the reduction pred ominantly in the high-frequency (respiratory) range (-73%). The low-frequen cy component of heart period variability was also reduced (-54%). This card iovascular profile of moderate GBS at the height of the disease could resul t from a demyelination of the reflex loop controlling respiratory oscillati ons in heart rate and from a desensitization of the arterial tree to an ele vated plasma noradrenaline. Sympathetic nervous activation may contribute t o the high resting heart rate in acute GBS.