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Background: Excessive sedation is associated with adverse patient outcomes during critical illness, and a validated monitoring technology could improve care. We developed a novel method, the responsiveness index (RI) of the frontal EMG. We compared RI data with Ramsay clinical sedation assessments in general and cardiac intensive care unit (ICU) patients., Methods: We developed the algorithm by iterative analysis of detailed observational data in 30 medical-surgical ICU patients and described its performance in this cohort and 15 patients recovering from scheduled cardiac surgery. Continuous EMG data were collected via frontal electrodes and RI data compared with modified Ramsay sedation state assessments recorded regularly by a blinded trained observer. RI performance was compared with Entropy™ across Ramsay categories to assess validity., Results: RI correlated well with the Ramsay category, especially for the cardiac surgery cohort (general ICU patients ρ=0.55; cardiac surgery patients ρ=0.85, both P<0.0001). Discrimination across all Ramsay categories was reasonable in the general ICU patient cohort [P(K)=0.74 (sem 0.02)] and excellent in the cardiac surgery cohort [P(K)=0.92 (0.02)]. Discrimination between 'lighter' vs 'deeper' (Ramsay 1-3 vs 4-6) was good for general ICU patients [P(K)=0.80 (0.02)] and excellent for cardiac surgery patients [P(K)=0.96 (0.02)]. Performance was significantly better than Entropy™. Examination of individual cases suggested good face validity., Conclusions: RI of the frontal EMG has promise as a continuous sedation state monitor in critically ill patients. Further investigation to determine its utility in ICU decision-making is warranted.

Background The Surgical Pleth Index ( SPI), derived from pulse amplitude and heartbeat interval, is proposed to monitor anti-nociception during anaesthesia. Its response to noxious stimulation can be affected by the intravascular volume status. This study investigated the effect of a fluid challenge ( FC) on SPI during steady-state conditions. Methods After Institutional Review Board approval, 33 consenting patients undergoing neurosurgery received a 4 ml/kg starch FC over less than 5 min under stable surgical stimulation conditions and stable propofol ( CePPF) and remifentanil ( CeREMI) effect-site concentrations as estimated by target-controlled infusion systems. Intravascular volume status was assessed using the Delta Down ( DD). We looked at the SPI response to FC according to DD, CePPF, and CeREMI. Results Following FC, SPI did not change in 16, increased in 12, and decreased in 3 patients. CeREMI poorly affected the SPI response to FC. In normovolaemic patients, the probability of an SPI change after FC was low under common CePPF (0.9 to 3.9 μg/ml). A decrease in SPI was more probable with worsening hypovolaemia and lowering CePPF, while an increase in SPI was more probable with increasing CePPF. SPI changes were only attributable to modifications in pulse wave amplitude and not in heart rate. Conclusions During stable anaesthesia and surgery, SPI may change in response to FC. The effect of FC on SPI is influenced by volaemia and CePPF through pulse wave amplitude modifications. These situations may confound the interpretation of SPI as a surrogate measure of the nociception-anti-nociception balance. [ABSTRACT FROM AUTHOR]

Background The Surgical Pleth Index (SPI) is proposed as a means to assess the balance between noxious stimulation and the anti-nociceptive effects of anaesthesia. In this study, we compared SPI, mean arterial pressure (MAP), and heart rate (HR) as a means of assessing this balance. Methods We studied a standard stimulus [head-holder insertion (HHI)] and varying remifentanil concentrations (CeREMI) in a group of patients undergoing neurosurgery. Patients receiving target-controlled infusions were randomly assigned to one of the three CeREMI (2, 4, or 6 ng ml−1), whereas propofol target was fixed at 3 µg ml−1. Steady state for both targets was achieved before HHI. Intravascular volume status (IVS) was evaluated using respiratory variations in arterial pressure. Prediction probability (Pk) and ordinal regression were used to assess SPI, MAP, and HR performance at indicating CeREMI, and the influence of IVS and chronic treatment for high arterial pressure, as possible confounding factors. Results The maximum SPI, MAP, or HR observed after HHI correctly indicated CeREMI in one of the two patients [accurate prediction rate (APR)=0.5]. When IVS and chronic treatment for high arterial pressure were taken into account, the APR was 0.6 for each individual variable and 0.8 when all of them predicted the same CeREMI. That increase in APR paralleled an increase in Pk from 0.63 to 0.89. Conclusions SPI, HR, and MAP are of comparable value at gauging noxious stimulation–CeREMI balance. Their interpretation is improved by taking account of IVS, treatment for chronic high arterial pressure, and concordance between their predictions. [ABSTRACT FROM AUTHOR]

The performance of recently introduced Surgical Stress Index (SSI), based on heart rate and photoplethysmography, was estimated during sevoflurane-fentanyl and isoflurane-fentanyl anesthesia during surgical procedures. Forty ASA I-III patients were enrolled. Anesthesia was induced with fentanyl 2 μgkg-1 and thiopentone 3-5 mg kg-1. Tracheal intubation was performed 5 minutes after fentanyl bolus. Patients were randomly allocated to receive sevoflurane (n = 20) or isoflurane (n = 20) in 30% oxygen/air. State entropy was kept at 40-60, target being 50. During surgery, fentanyl boluses 1.5 μgkg-1 were given at 30-40-minute intervals. SSI increased significantly after intubation. During surgery, the decrease of SSI after fentanyl boluses was similar in sevoflurane and isoflurane groups but SSI values were higher in sevoflurane than in isoflurane group. Tracheal intubation, skin incision, and surgical stimuli increased SSI from baseline, indicating that nociceptive stimuli increase SSI. Fentanyl boluses during surgery decreased SSI, indicating that increasing analgesia decreases SSI. [ABSTRACT FROM AUTHOR]

Background: No validated monitoring method is available for evaluating the nociception/antinociception balance. We assessed the surgical stress index (SSI), computed from finger photoplethysmographic waveform amplitudes and pulse-to-pulse intervals, in patients undergoing shoulder surgery under general anesthesia (GA) and interscalene plexus block and in patients with GA only. Methods: In this prospective, randomized study in 26 patients, increased blood pressure (BP) or heart rate, movement, and coughing were considered to be signs of intraoperative nociception and were treated with alfentanil. GA was maintained with desflurane aiming at a State Entropy level of 50. Photoplethysmographic waveforms were collected from the contra-lateral arm to the surgery and SSI values from 0 (no surgical stress) to 100 (maximal surgical stress) were calculated off-line. Results: Two minutes after skin incision, SSI had not increased in the plexus group and was lower in the plexus group (38 ± 13) compared with the controls (58 ± 13, P<0.005). Among the controls, 1 min before alfentanil administration, the SSI value was higher than during periods of adequate antinociception, 59 ± 11 vs. 39 ± 12 ( P<0.01). The total cumulative need for alfentanil was higher in controls (2.7 ± 1.2 mg) compared with the plexus group (1.6 ± 0.5 mg; P=0.008). Tetanic stimulation to the ulnar region of the hand increased SSI significantly only among the patients with plexus block not covering the site of the stimulation. Conclusion: SSI values were lower in patients with plexus block covering the sites of nociceptive stimuli. In detecting nociceptive stimuli, SSI had better performance than heart rate, BP, or response entropy. [ABSTRACT FROM AUTHOR]