Acute intracranial lesions and respiratory sinus arrhythmia
J. I. Frank, A. H. Ropper and G. Zuniga
Neuromedical/Neurosurgical Intensive Care Unit, Massachusetts General Hospital, Boston.
We studied the effects of acute intracranial lesions on the respiratory
sinus arrhythmia (RSA) with the use of computerized measurements of the
ratio of expiratory to inspiratory R-R intervals. The RSA was reduced below
the 95th percentile for age in 20 of 27 patients, an average of 2 days
after an acute event. Only four patients, without neurological deficits,
had a normal RSA. Two patients, with signs of secondary brain-stem
compression from a mass, had an increased RSA, without the bradycardia that
is usually associated with Cushing's response. Twenty-three patients had
their respiratory rate controlled by positive pressure ventilation during
testing, and our preliminary findings suggested that this was not
responsible for reducing the RSA. Acute intracranial lesions caused a
diminished RSA, perhaps by reducing supratentorial influences on vagal
cardioinhibitory activity. In contrast, once signs of secondary brain-stem
compression occur, the RSA is greatly increased while the heart rate
remains unchanged, offering a possible method of noninvasive monitoring for
this complication.
