title: Responsiveness of the frontal EMG for monitoring the sedation state of critically ill patients.
abstract: BACKGROUND
  Excessive sedation is associated with adverse patient outcomes during critical illness, and a validated monitoring technology could improve care. We developed a novel method, the responsiveness index (RI) of the frontal EMG. We compared RI data with Ramsay clinical sedation assessments in general and cardiac intensive care unit (ICU) patients.
  
  
  METHODS
  We developed the algorithm by iterative analysis of detailed observational data in 30 medical-surgical ICU patients and described its performance in this cohort and 15 patients recovering from scheduled cardiac surgery. Continuous EMG data were collected via frontal electrodes and RI data compared with modified Ramsay sedation state assessments recorded regularly by a blinded trained observer. RI performance was compared with Entropy™ across Ramsay categories to assess validity.
  
  
  RESULTS
  RI correlated well with the Ramsay category, especially for the cardiac surgery cohort (general ICU patients ρ=0.55; cardiac surgery patients ρ=0.85, both P<0.0001). Discrimination across all Ramsay categories was reasonable in the general ICU patient cohort [P(K)=0.74 (sem 0.02)] and excellent in the cardiac surgery cohort [P(K)=0.92 (0.02)]. Discrimination between 'lighter' vs 'deeper' (Ramsay 1-3 vs 4-6) was good for general ICU patients [P(K)=0.80 (0.02)] and excellent for cardiac surgery patients [P(K)=0.96 (0.02)]. Performance was significantly better than Entropy™. Examination of individual cases suggested good face validity.
  
  
  CONCLUSIONS
  RI of the frontal EMG has promise as a continuous sedation state monitor in critically ill patients. Further investigation to determine its utility in ICU decision-making is warranted.
authors.affiliation: Anaesthetics, Critical Care and Pain Medicine, General Intensive Care Unit, Edinburgh Royal Infirmary, Little France Crescent, Edinburgh, UK. twalsh@staffmail.ed.ac.uk
authors.forename: T S
authors.initials: TS
authors.lastname: Walsh
authors.forename: T P
authors.initials: TP
authors.lastname: Lapinlampi
authors.forename: P
authors.initials: P
authors.lastname: Ramsay
authors.forename: M O K
authors.initials: MO
authors.lastname: Särkelä
authors.forename: K
authors.initials: K
authors.lastname: Uutela
authors.forename: H E
authors.initials: HE
authors.lastname: Viertiö-Oja
mesh_terms: D000328:Adult; D000368:Aged; D000369:Aged, 80 and over; D000465:Algorithms; D000758:Anesthesia; D000762:Anesthesia Recovery Period; D006348:Cardiac Surgical Procedures; D015331:Cohort Studies; D003422:Critical Care / Q000379:methods; D016638:Critical Illness; D004576:Electromyography / Q000379:methods; D005625:Frontal Lobe / Q000187:drug effects*; D006801:Humans; D008875:Middle Aged; D008991:Monitoring, Physiologic / Q000379:methods*; D015203:Reproducibility of Results; D012121:Respiration, Artificial