The Potential of Quantified Lower Cranial Nerve EMG for Monitoring of Anesthetic Depth

EMG monitoring

While most neurophysiologists are familiar with electromyography (EMG) for the purpose of clinical diagnostics, this technique also has a long tradition for neuro-monitoring. In short, intra-operative use of EMG can be divided into stimulated EMG on the one hand and monitoring of the free-running EMG and its spontaneous activity on the other hand. Methods for utilization of stimulated EMG are covered elsewhere in this book. This chapter focuses on the monitoring of spontaneous, or, more correctly, "surgically evoked" EMG. The history and underlying physiologic principles of intra-operative EMG are covered in this chapter as well as a detailed overview of the methodology. Building up from the basis of this background, we describe examples of how EMG can be used to help in intra-operative detection of adverse events and also in the prediction of postoperative outcomes. In the opinion of the authors, EMG should not be used as a "standalone" technique in contemporary neuro-monitoring. Most of its significant potential may be realized when it is used in a complementary way together with other modalities, mainly motor evoked potentials. Bearing this in mind, we sketch out how such a complementary setup may be used for improved neuro-monitoring.

Effect of rocuronium on the bispectral index under anesthesia and tracheal intubation

The aim of the present study was to investigate the effect of various doses of rocuronium on bispectral index (BIS) responses to propofol induction and tracheal intubation, as well as the role of the non-depolarization muscle relaxant rocuronium on the depth of sedation. A total of 72 patients (American Society of Anesthesiologists physical status I-II) were anaesthetized with propofol using a target-controlled infusion, and randomly divided into two sedation level groups (n=36). The patients were divided into 2 groups according to the BIS value: A normal sedation group (group 1), with a stable BIS value at 40-60, and a deep sedation group (group 2), with a BIS value <20 or with burst suppression. Each group was randomly divided into 4 subgroups A-D (n=9) according to the various doses of rocuronium (0.3, 0.6, 0.9 and 1.2 mg/kg). Tracheal intubation was performed after 2 min of rocuronium administration. BIS, electromyography (EMG), heart rate (HR) and mean arterial pressure (MAP) were recorded continuously and averaged over 1 min during baseline (T1), steady state (T2), 2 min after rocuronium infusion (T3), and 0, 2 and 5 min after tracheal intubation. The results demonstrated that HR and MAP decreased significantly at T2 and T3 compared with T1. Following tracheal intubation (L0), HR and MAP significantly increased compared with T2 and T3, and returned to levels similar to those prior to intubation after 5 min. In group 1C and 1D, BIS was significantly decreased at T3 compared with T2; BIS was significantly increased at L0 compared with T3 in group 1A and 1B. EMG at earlier stages of anesthesia was significantly higher compared with other points, and was significantly increased at L0 compared with T3 in group 1A and 1B. These results demonstrated that BIS response may be associated with the dosage of rocuronium in the normal sedation group, although no association was observed with the deep sedation group. Tracheal intubation resulted in marked hemodynamic changes under both normal and deep sedation.

Neuroanesthesiology update

We review topics pertinent to the perioperative care of patients with neurological disorders. Our review addresses topics not only in the anesthesiology literature, but also in basic neurosciences, critical care medicine, neurology, neurosurgery, radiology, and internal medicine literature. We include literature published or available online up through December 8, 2013. As our review is not able to include all manuscripts, we focus on recurring themes and unique and pivotal investigations. We address the broad topics of general neuroanesthesia, stroke, traumatic brain injury, anesthetic neurotoxicity, neuroprotection, pharmacology, physiology, and nervous system monitoring.