Perioperative use of physostigmine to reduce opioid consumption and peri-incisional hyperalgesia: a randomised controlled trial.

BACKGROUND: Several studies have shown that cholinergic mechanisms play a pivotal role in the anti-nociceptive system by acting synergistically with morphine and reducing postoperative opioid consumption. In addition, the anti-cholinesterase drug physostigmine that increases synaptic acetylcholine concentrations has anti-inflammatory effects. METHODS: In this randomised placebo-controlled trial including 110 patients undergoing nephrectomy, we evaluated the effects of intraoperative physostigmine 0.5 mg h-1 i.v. for 24 h on opioid consumption, hyperalgesia, pain scores, and satisfaction with pain control. RESULTS: Physostigmine infusion did not affect opioid consumption compared with placebo. However, the mechanical pain threshold was significantly higher (2.3 [sd 0.3]) vs 2.2 [0.4]; P=0.0491), and the distance from the suture line of hyperalgesia (5.9 [3.3] vs 8.5 [4.6]; P=0.006), wind-up ratios (2.2 [1.5] vs 3.1 [1.5]; P=0.0389), and minimum and maximum postoperative pain scores at 24 h (minimum 1.8 [1.0] vs 2.4 [1.2]; P=0.0451; and maximum 3.2 [1.4] vs 4.2 [1.4]; P=0.0081) and 48 h (minimum 0.9 [1.0] vs 1.6 [1.1]; P=0.0101; and maximum 2.0 [1.5] vs 3.2 [1.6]; P=0.0029) were lower in the study group. Pain Disability Index was lower and satisfaction with pain control was higher after 3 months in the physostigmine group. CONCLUSIONS: In contrast to previous trials, physostigmine did not reduce opioid consumption. As pain thresholds were higher and hyperalgesia and wind-up lower in the physostigmine group, we conclude that physostigmine has anti-hyperalgesic effects and attenuates sensitisation processes. Intraoperative physostigmine may be a useful and safe addition to conventional postoperative pain control. CLINICAL TRIAL REGISTRATION: EudraCT number 2012-000130-19.

Infrared absorption spectrometer for the determination of temperature and species profiles in an entrained flow gasifier.

An absorption spectrometer utilizing a tunable distributed feedback diode laser at 2.3 µm and an interband cascade laser at 3.1 µm has been developed to measure temperature and concentrations of CO, CH4, C2H2, and H2O under gasification conditions. A wavelength division multiplexing approach using a single ZrF4-fiber was used to measure both wavelength regions simultaneously. The performance of the spectrometer has been tested in laminar flat flames and a heated cell and then applied for measurements at an atmospheric entrained flow gasifier (REGA). A water-cooled optical probe was used to provide optical access at two measurement positions. By moving the burner, axial profiles of temperature and species concentration could be obtained. These profiles were compared with numerical simulations and can be used to validate the simulation.