Autonomic impairment in tetanus: delayed baroreflex involvement

Autonomic nervous system impairment plays an important role in the clinical course of tetanus and is thought to be responsible for life-threatening complications. It is believed to be associated with predominance of sympathetic activity. Direct baroreflex involvement has not yet been reported. We hypothesized that impaired baroreflex may contribute to the autonomic cardiovascular dysregulation in tetanus. In a patient with tetanus baroreflex sensitivity was measured on the first 5 consecutive days non-invasively using a Finometer device. Baroreflex gain was calculated as sequential cross-correlation between heart rate and blood pressure. Short-time pulse interval standard deviations (SDNN) were derived. Additionally, heart rate and arterial blood pressure were monitored and recorded continuously. Baroreflex gain values and SDNN were compared to a sex- and age-matched control subject. Compared to the control subject the patient with tetanus initially did not show a significant difference in baroreflex gain values (mean 3.68 vs 3.15, p=0.1). However, in the course of the disease an almost complete baroreflex failure occurred (mean 1.0 vs 3.15 and 0.97 vs 3.15, both p<0.0001). No correlation was found between the dynamics of baroreflex gain values and blood pressure or heart rate variability expressed by standard deviation and variance. All 5 measurements in the tetanus patient showed decreased short-time SDNN when compared to the control subject and healthy standards. In our patient we found baroreflex impairment as a part of complex autonomic dysfunction in tetanus. Furthermore, baroreflex impairment occurred only delayed. Blood pressure instability could not be explained by baroreflex dynamics. We suggest that a shift towards sympathetic activity possibly overruled the effects of decreased baroreflex sensitivity on blood pressure regulation.