title: Measurement of surgical stress in anaesthetized children.
abstract: BACKGROUND
  The surgical stress index (SSI), derived from a combination of heart rate (HR) and photoplethysmographic amplitude (PPGA) time series, is a novel method for continuous monitoring of intraoperative stress and has been validated in adults. The applicability of SSI and its constituents to monitoring children has not been previously evaluated.
  
  
  METHODS
  In this controlled trial, 22 anaesthetized patients, aged 4-17 yr, undergoing strabismus surgery were randomized into two groups, Group LL and Group BSS. Patients in Group LL received topical conjunctival anaesthesia with a 1:1 mixture of lidocaine 2% and levobupivacaine 0.75%, and patients in Group BSS received balanced salt solution.
  
  
  RESULTS
  Endotracheal intubation (n=22) increased median (range) SSI from 39.2 (22.6-55.6) to 53.6 (35.8-63.3) (P<0.001), decreased PPGA from 5.62 (2.79-9.69) to 5.27 (2.59-7.54)% (P=0.001), and increased the difference of response entropy (RE) and state entropy (SE) of frontal biopotentials (RE-SE) from 3.1 (0.06-9.1) to 5.7 (0.6-9.4) (P=0.01). Conventional haemodynamic variables also increased, median (range) HR from 72.9 (56.7-113.8) to 84.2 (60.4-124.8) beats min(-1) (P<0.001), and systolic non-invasive arterial pressure (S-NIBP) from 87 (78-143) to 103 (79-125) (P=0.007). When 3 min baseline before surgery was compared with 12 min of surgery, median (range) SSI increased from 43.3 (31.2-58.0) to 49.9 (39.3-57.2) (P=0.042) vs from 46.6 (26.8-57.8) to 52.1 (31.7-60.1) (P=0.024) and PPGA decreased from 6.60 (3.10-8.24) to 5.80 (3.03-7.65)% (P<0.001) vs from 5.51 (3.25-9.84) to 5.06 (3.08-8.99)% (P=0.042), in Groups LL and BSS, respectively, but SSI or other indicators did not differ significantly between the groups.
  
  
  CONCLUSIONS
  SSI, PPGA, HR, NIBP, RE, and RE-SE detect autonomic responses to nociceptive stimuli in anaesthetized children undergoing strabismus surgery.
authors.affiliation: Department of Anaesthesiology and Intensive Care Medicine, Eye Hospital, Helsinki, Finland. helena.kallio@hus.fi
authors.forename: H
authors.initials: H
authors.lastname: Kallio
authors.forename: L I
authors.initials: LI
authors.lastname: Lindberg
authors.forename: A S
authors.initials: AS
authors.lastname: Majander
authors.forename: K H
authors.initials: KH
authors.lastname: Uutela
authors.forename: M L
authors.initials: ML
authors.lastname: Niskanen
authors.forename: M P J
authors.initials: MP
authors.lastname: Paloheimo
mesh_terms: D000293:Adolescent; D000768:Anesthesia, General / Q000379:methods; D000772:Anesthesia, Local / Q000379:methods; D002648:Child; D002675:Child, Preschool; D004311:Double-Blind Method; D005260:Female; D006339:Heart Rate; D006801:Humans; D007431:Intraoperative Complications / Q000175:diagnosis*; D007442:Intubation, Intratracheal; D008297:Male; D016343:Monitoring, Intraoperative / Q000379:methods*; D017156:Photoplethysmography; D013312:Stress, Physiological / Q000175:diagnosis*