M. Huiku

EEG spectral entropy, heart rate, photoplethysmography and motor responses to skin incision during sevoflurane anaesthesia.

Background:  Analgesia is a part of balanced anaesthesia, but direct indicators of nociception do not exist. We examined the relationship between motor reactions and physiological variables during skin incision in sevoflurane anaesthesia and hypothesized that nociception could be detected and graded by significant changes in these variables.

Effects of nitric oxide synthase inhibition on dexmedetomidine-induced vasoconstriction in healthy human volunteers

BACKGROUND This study aimed to assess the contribution of endothelial nitric oxide synthesis to the net responses of human peripheral blood vessels in vivo to the selective alpha(2)-adrenoceptor agonist dexmedetomidine. METHODS Two groups of healthy young men were studied. In the first experiment, after brachial plexus block, the responses of digital arteries to systemically administered dexmedetomidine (target plasma concentration 1.2 ng ml(-1)) were studied using a photoplethysmograph (n=10) during i.a. infusions of saline and the nitric oxide synthase (NOS) inhibitor N(G)-monomethyl-L-arginine (L-NMMA) (8 micromol min(-1)). In a separate experiment, after pre-treatment with acetylsalicylic acid, responses to increasing doses of dexmedetomidine (0.01-164 ng min(-1)) in the presence and absence of L-NMMA were compared in dorsal hand veins (DHV) (n=10) using linear variable differential transformers. RESULTS L-NMMA significantly augmented dexmedetomidine-induced vasoconstriction of digital arteries as assessed by an increase in light transmission through a finger and by a decrease in finger temperature. The mean (95% confidence interval) extent of the additional effect of L-NMMA over the constrictor effect of dexmedetomidine alone was 19% (14-24) (P<0.0001). In DHV, L-NMMA had variable effects on the dexmedetomidine-constriction dose-response curve. In three subjects, the curve was shifted significantly to the left (with a >10-fold difference in ED(50)), but ED(50) was only marginally affected by L-NMMA in the other subjects (difference in ED(50) <five-fold). CONCLUSIONS The endothelial NOS enzyme has a significant role in opposing the vasoconstrictor action of dexmedetomidine at drug concentrations within the therapeutic range.

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.