title: Evaluation of the surgical stress index during spinal and general anaesthesia.
abstract: BACKGROUND
  Although in modern anaesthesia, monitoring depth of anaesthesia and quality of neuromuscular block are routine, monitoring of analgesia still remains challenging. Recently, the surgical stress index (SSI), derived from finger photoplethysmographic signal, was introduced as a surrogate variable reflecting the nociception-antinociception balance. This study aimed at evaluating the SSI in patients undergoing regional anaesthesia either alone or combined with sedation compared with patients undergoing general anaesthesia (GA).
  
  
  METHODS
  Seventy-one patients undergoing general (n=24) or spinal anaesthesia with (n=24) or without sedation (n=23) were included. SSI was measured the day before surgery and at defined time points during anaesthesia and surgery and also in the recovery room. SSI was compared with haemodynamic variables like heart rate and systolic arterial pressure.
  
  
  RESULTS
  The SSI was higher in patients undergoing spinal anaesthesia [mean 65, CI (59.3-70.5)] compared with GA [48 (39.9-56.4), P<0.01], and baseline [41 (37.3-44.2), P<0.001]. During spinal anaesthesia with sedation [44 (36.2-50.9)], it was comparable with the baseline level (P>0.05). In comparison with baseline, SSI in the recovery room was higher in patients after GA [59 (48.4-67.9), P<0.025] but not after spinal anaesthesia [53 (47.6-60.1), P>0.05] or after spinal anaesthesia with sedation [54 (45.8-65.1), P>0.05]. Changes of the SSI were not reflected by changes of haemodynamic variables.
  
  
  CONCLUSIONS
  In fully awake patients under spinal anaesthesia, the SSI does not reflect the nociception-antinociception balance. This may be due to the influence of mental stress on the sympathetic nervous system. Even light sedation attenuates these influences.
authors.affiliation: Department of Anaesthesiology and Intensive Care Medicine, University-Hospital Schleswig-Holstein, Campus Kiel, Schwanenweg 21, D-24105 Kiel, Germany. ilies@anaesthesie.uni-kiel.de
authors.forename: C
authors.initials: C
authors.lastname: Ilies
authors.forename: M
authors.initials: M
authors.lastname: Gruenewald
authors.forename: J
authors.initials: J
authors.lastname: Ludwigs
authors.forename: C
authors.initials: C
authors.lastname: Thee
authors.forename: J
authors.initials: J
authors.lastname: Höcker
authors.forename: R
authors.initials: R
authors.lastname: Hanss
authors.forename: M
authors.initials: M
authors.lastname: Steinfath
authors.forename: B
authors.initials: B
authors.lastname: Bein
mesh_terms: D000293:Adolescent; D000328:Adult; D000368:Aged; D000369:Aged, 80 and over; D000768:Anesthesia, General / Q000379:methods*; D000775:Anesthesia, Spinal / Q000379:methods*; D001794:Blood Pressure / Q000502:physiology; D016292:Procedural Sedation; D005260:Female; D006339:Heart Rate / Q000502:physiology; D006801:Humans; D008297:Male; D008875:Middle Aged; D016343:Monitoring, Intraoperative / Q000379:methods*; D019637:Orthopedic Procedures; D011446:Prospective Studies; D013312:Stress, Physiological / Q000502:physiology*; D013564:Sympathetic Nervous System / Q000502:physiology; D013520:Urologic Surgical Procedures; D055815:Young Adult