Donchin, Y., Constantini, S., Szold, A., Byrne, E. A., and Porges, S. W. (1992). Cardiac vagal tone predicts outcome in neurosurgical patients. Critical Care Medicine, 20(7), 942-949.
Abstract
Objective: To evaluate the relationship
between presurgical levels of cardiac vagal tone
and outcome in neurosurgical patients.
Design: Prospective series.
Setting: Respiratory ICU in a university
hospital.
Patients: Fifty-one adults admitted to the
respiratory ICU between 1982 and 1985. Forty-two
patients were scheduled for elective
neurosurgery, and nine patients suffered from head
trauma.
Interventions: Ten minutes of electrocardiographic
(EKG) data were recorded before medical
intervention. Neurosurgical patients scheduled
for surgery had EKG data recorded 24 hrs
before their operation. Trauma patients had
EKG data recorded immediately after arrival in
the respiratory ICU.
Measurements and Main Results: Cardiac vagal
tone was evaluated using a vagal tone index,
quantified from the EKG. Cardiac vagal tone
monitored before surgical intervention significantly
distinguished between the outcome groups
only for the elective neurosurgical patients. Age,
gender, heart rate, Glasgow Coma Scale scores,
and tumor location, size, and malignancy were
not related to outcome in the elective neurosurgery
group. However, within the trauma group,
low Glasgow Coma Scale scores were significantly
related to poor outcome.
Conclusions: Cardiac vagal tone may offer
important predictive value by alerting the physician
to the functional consequence of head
injury. Information relating to autonomic nervous
system functioning, such as the vagal tone
index used in this study, may provide additional
information that will complement the computed
tomography scan results. This study demonstrates
that the vagal tone index is a predictive
factor that may be efficiently extracted from the
heart rate pattern routinely monitored in ICUs.