K. Uutela

Measurement of surgical stress in anaesthetized children

BACKGROUNDnThe 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.nnnMETHODSnIn 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.nnnRESULTSnEndotracheal 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.nnnCONCLUSIONSnSSI, PPGA, HR, NIBP, RE, and RE-SE detect autonomic responses to nociceptive stimuli in anaesthetized children undergoing strabismus surgery.

Autonomic nervous system state: the effect of general anaesthesia and bilateral tonsillectomy after unilateral infiltration of lidocaine

BACKGROUNDnAutonomic nervous system (ANS) sensitively responds to intraoperative stress. Several indices characterizing the state and responses of autonomic signs to nociceptive stimuli have been introduced. This study evaluated the behaviour of ANS descriptors after induction, before and during tracheal intubation, and during bilateral tonsillectomies after random and blinded unilateral infiltration of lidocaine 1% until emergence from anaesthesia.nnnMETHODSnTwelve patients undergoing bilateral tonsillectomy were anaesthetized with fentanyl and propofol (induction) and sevoflurane (maintenance). All patients were monitored throughout anaesthesia for middle finger temperature, non-invasive arterial pressure, heart rate (HR) and pulse rate (PR), state entropy (SE) and response entropy (RE), and surgical pleth index (SPI). New parameters complementing the above and characterizing the ANS state (ANSS) and responses are pulse-to-pulse interval (PPI), pulse plethysmographic amplitude (PPGA), ANSS, and an index based on maximal ANSS for the subject (ANSSI). Serial data were stored as 10 s averages into a laptop computer.nnnRESULTSnAnaesthesia induction was associated with an increase in finger temperature to >30 degrees C within 10 min, whereas PPGA increased to their maximum levels within 5 min. Laryngoscopy and intubation were associated with transient autonomic responses in most patients. All autonomic signs indicated statistically significant sympathetic activation during saline-infiltrated tonsillectomies when compared with lidocaine-infiltrated sides (P<0001). Hypnotic measures (SE and RE) and finger temperatures did not differ between the sides.nnnCONCLUSIONSnHR, PPI, PPGA, ANSS, ANSSI, SPI, and RE-SE detect autonomic responses to nociceptive stimuli and differentiate between tonsillectomies on locally anaesthetized tonsils from controls.

High levels of surgical stress index before movements of anesthetized patients: A-87

High levels of surgical stress index before movements of anesthetized patients K. Uutela1, M. Huiku1, P. Karkas1, M. Kymalainen1, N. Ojala1, A. Yli-Hankala2 1GE Healthcare, Helsinki; 2Tampere University Hospital, Tampere, Finland Background and Goal of Study: Surgical stress Index (SSI) is a novel method for measuring the hemodynamic changes related to the surgical stress response (1). Sudden noxious stimulation may cause movements whose exact time cannot be predicted. However, we hypothesized that during the surgery, changes in the balance between the level of analgesia and the average level of noxious stimulation might increase both stress level and probability of movements. Materials and Methods: Physiological parameters were measured from 55 female patients anesthetized with propofol and remifentanil, and paralyzed with rocuronium. Remifentanil effect-site concentration was changed between 1, 3, and 5 ng/ml. SSI was calculated off-line. We compared the maximum SSI level of the periods 5 min before patient movements noticed by a research nurse with the maximum SSI levels of random 5 min periods of the surgery of patients with no noticed movements. Results and Discussions: Of the 55 patients, 13 had annotated movements during the surgery, and 20 had no annotated movements at all. Average rocuronium dosages were similar (32 and 33 mg/h, respectively). As the SSI levels of the two groups were overlapping, the SSI information alone could not infallibly predict whether an individual patient will move or not within the next 5 minutes. However, there were significantly (p 0.05; Mann-Whitney) more high SSI values with the patients that did move.