Continuous autonomic system monitoring during neurosurgical procedures –proof of concept

Vegetative reactions are common during neurosurgical procedures. Known effects are mainly cardiovascular, including tachy- and bradyarrhythmia, hyper- and hypotonia as well as cardiac arrest. Computer-assisted real-time analysis of heart rate variability (HRV), baroreflex-sensitivity (BRS) allows for continuous evaluation of the autonomic nervous system (ANS). We analyzed ANS parameters during intracranial neurosurgical procedures. In this pilot study, we aim to provide proof-of-concept that ANS monitoring during surgery is feasible and yields stable results.We included 129 consecutive patients undergoing neurosurgery for intracranial pathologies over a period of four months. Heart rate (HR) and mean arterial pressure (MAP) were continuously monitored during routine anesthesiology care. Data were recorded via ICM + software. HRV, BRS and other vegetative parameters were calculated continuously. Intraoperative events such as hypo-/hypertonia or brady-/tachycardia were monitored.Mean age was 47.2 ± 17.7 years. Of all patients, 54.3% were male (n = 70). For every patient, four intraoperative episodes were defined: start of anesthesia until incision - start of incision until craniotomy - craniotomy until end of resection or intracranial manipulation - end phase until skin closure. BRS continuously decreased during cranial surgery, indicating stabilized autonomic function. Furthermore, blood pressure variability was increased during semi-sitting surgery.Autonomic system monitoring during neurosurgical procedures is safe and feasible. Intraoperatively, an increasing sympathetic activity has been observed without clear disctinction between surgical or anesthesiological events as underlying cause. Monitoring results are reproducible and may be of importance for the detection and prevention of intraoperative cardiovascular events.