Heart rate variability under sensorial stimulation as a prognostic parameter for the functional outcome of severe head injury

This article investigates the predictive efficiency in respect of functiona l outcome after severe traumatic brain injury, of psychophysiological param eters during a baseline period or during sensorial stimulution for the dura tion of unconsciousness. The frequency spectra of heart frequency and the c ardiosomatic coupling served as psychophysiological parameters. Additional clinical parameters included age, brain stem involvement, traumatic subarac hnoidal bleeding and sedation. The test panel consisted of 34 patients. Eac h of them had scored for at least three days a coma depth below 8 on the Gl asgow Coma Scale. The evaluation of the functional outcome was effected by means of the Functional Independence Measure (FIM). The duration of unconsc iousness was best predicted by the incidence of brain stem involvement. The functional outcome correlated best with the maximum of the middle frequenc y spectrum (0.09 - 0.15 Hz) of the heart frequency. This holds for therapeu tic stimulation but not for baseline measurement. All the other clinical an d psychophysiological parameters did not make a significant contribution to the prognosis. Hence, our investigation replicated other investigations wh ich had already pointed out the high significance of brain stem involvement for the remission process with regard to head traumata. Our research shows that the analysis of the frequency spectrum of heart rate variability is n ot only helpful in therapy evaluation but also in making a prognosis.