title: Entropy and bispectral index for assessment of sedation, analgesia and the effects of unpleasant stimuli in critically ill patients: an observational study.
abstract: BACKGROUND
  Sedative and analgesic drugs are frequently used in critically ill patients. Their overuse may prolong mechanical ventilation and length of stay in the intensive care unit. Guidelines recommend use of sedation protocols that include sedation scores and trials of sedation cessation to minimize drug use. We evaluated processed electroencephalography (response and state entropy and bispectral index) as an adjunct to monitoring effects of commonly used sedative and analgesic drugs and intratracheal suctioning.
  
  
  METHODS
  Electrodes for monitoring bispectral index and entropy were placed on the foreheads of 44 critically ill patients requiring mechanical ventilation and who previously had no brain dysfunction. Sedation was targeted individually using the Ramsay Sedation Scale, recorded every 2 hours or more frequently. Use of and indications for sedative and analgesic drugs and intratracheal suctioning were recorded manually and using a camera. At the end of the study, processed electroencephalographical and haemodynamic variables collected before and after each drug application and tracheal suctioning were analyzed. Ramsay score was used for comparison with processed electroencephalography when assessed within 15 minutes of an intervention.
  
  
  RESULTS
  The indications for boli of sedative drugs exhibited statistically significant, albeit clinically irrelevant, differences in terms of their association with processed electroencephalographical parameters. Electroencephalographical variables decreased significantly after bolus, but a specific pattern in electroencephalographical variables before drug administration was not identified. The same was true for opiate administration. At both 30 minutes and 2 minutes before intratracheal suctioning, there was no difference in electroencephalographical or clinical signs in patients who had or had not received drugs 10 minutes before suctioning. Among patients who received drugs, electroencephalographical parameters returned to baseline more rapidly. In those cases in which Ramsay score was assessed before the event, processed electroencephalography exhibited high variation.
  
  
  CONCLUSIONS
  Unpleasant or painful stimuli and sedative and analgesic drugs are associated with significant changes in processed electroencephalographical parameters. However, clinical indications for drug administration were not reflected by these electroencephalographical parameters, and barely by sedation level before drug administration or tracheal suction. This precludes incorporation of entropy and bispectral index as target variables for sedation and analgesia protocols in critically ill patients.
authors.affiliation: Department of Intensive Care Medicine, Bern University Hospital and University of Bern, Freiburgstrasse, CH-3010 Bern, Switzerland.
authors.forename: Matthias
authors.initials: M
authors.lastname: Haenggi
authors.forename: Heidi
authors.initials: H
authors.lastname: Ypparila-Wolters
authors.forename: Christine
authors.initials: C
authors.lastname: Bieri
authors.forename: Carola
authors.initials: C
authors.lastname: Steiner
authors.forename: Jukka
authors.initials: J
authors.lastname: Takala
authors.forename: Ilkka
authors.initials: I
authors.lastname: Korhonen
authors.forename: Stephan M
authors.initials: SM
authors.lastname: Jakob
mesh_terms: D000328:Adult; D000368:Aged; D000369:Aged, 80 and over; D000698:Analgesia / Q000379:methods*; D016638:Critical Illness / Q000628:therapy*; D004569:Electroencephalography / Q000187:drug effects* / Q000379:methods; D019277:Entropy; D006801:Humans; D006993:Hypnotics and Sedatives / Q000494:pharmacology / Q000627:therapeutic use*; D008875:Middle Aged; D010146:Pain / Q000188:drug therapy* / Q000503:physiopathology; D010147:Pain Measurement / Q000187:drug effects / Q000379:methods
chemical_list: D006993:Hypnotics and Sedatives
references.citation: Intensive Care Med. 2008 Feb;34(2):308-15
references.pmid: 17898996
references.citation: Br Med J. 1974 Jun 22;2(5920):656-9
references.pmid: 4835444
references.citation: Intensive Care Med. 1996 Nov;22(11):1186-90
references.pmid: 9120111
references.citation: Acta Anaesthesiol Scand. 2004 Feb;48(2):154-61
references.pmid: 14995936
references.citation: Anesthesiology. 2007 Apr;106(4):687-95; quiz 891-2
references.pmid: 17413906
references.citation: Crit Care Med. 1998 May;26(5):947-56
references.pmid: 9590327
references.citation: Intensive Care Med. 2001 May;27(5):853-8
references.pmid: 11430541
references.citation: Crit Care Clin. 1999 Jan;15(1):17-33, v
references.pmid: 9929784
references.citation: Pharmacotherapy. 2001 Jan;21(1):1-6
references.pmid: 11191727
references.citation: Anesth Analg. 2005 Oct;101(4):1141-1151
references.pmid: 16192535
references.citation: Chest. 1997 Nov 5;112(5):1317-23
references.pmid: 9367475
references.citation: JAMA. 2003 Jun 11;289(22):2983-91
references.pmid: 12799407
references.citation: Crit Care Med. 2002 Jan;30(1):119-41
references.pmid: 11902253
references.citation: Br J Anaesth. 1998 Jun;80(6):834-6
references.pmid: 9771317
references.citation: Intensive Care Med. 1998 Dec;24(12):1294-8
references.pmid: 9885883
references.citation: Intensive Care Med. 2001 Jan;27(1):107-14
references.pmid: 11280620
references.citation: Anesthesiology. 1998 Oct;89(4):980-1002
references.pmid: 9778016
references.citation: Anesth Analg. 2005 Dec;101(6):1713-1718
references.pmid: 16301247
references.citation: Crit Care Med. 1995 Dec;23(12):1954-61
references.pmid: 7497717
references.citation: Am J Respir Crit Care Med. 2002 Apr 1;165(7):867-903
references.pmid: 11934711
references.citation: Crit Care Med. 1999 Jul;27(7):1325-9
references.pmid: 10446827
references.citation: Pharmacotherapy. 2000 Jan;20(1):75-82
references.pmid: 10641977
references.citation: Crit Care Med. 2005 May;33(5):1146-7
references.pmid: 15891353
references.citation: N Engl J Med. 2000 May 18;342(20):1471-7
references.pmid: 10816184
references.citation: Crit Care Med. 1999 Aug;27(8):1499-504
references.pmid: 10470756
references.citation: Chest. 1998 Aug;114(2):541-8
references.pmid: 9726743