In critically ill patients, the central nervous system remains vulnerable to multiple insults including ischemia, hemorrhagic events, and encephalopathy. The peripheral nervous system is vulnerable in the setting of neuromuscular blockade (NMB), related drug-drug interactions, and drug-clinical state interactions. Optimal assessment of the nervous system is done by means of the clinical neurological examination. In this manner, orientation, arousal, and responsiveness to stimulation provide feedback on focal and global stability of the central nervous system. Where clinical evaluation is compromised, such as with deep sedation and NMB, risk of undetected seizure activity, and/or progression of neurological injury increases dramatically. A patient receiving NMB risks breakthrough awareness and pain. Long-term complications of NMB including prolonged weakness or paralysis as well as post- traumatic stress dramatically increase morbidity and length of stay.
Technologies such as electroencephalogram (EEG) and bispectral index (BIS™) monitoring are effective for assessing cerebral function as well as level of sedation or arousal, respectively, in patients with a compromised neurological assessment. Neuromuscular transmission (NMT) monitoring by means of peripheral nerve stimulation and assessment of the evoked response may be utilized, within the context of clinical assessment, to determine level of chemical paralysis and minimize dosing of NMB agents.
This article explores utilization and differentiates technologies such as EEG, BIS, and NMT monitoring. Monitoring parameters are illustrated using a case study approach.