Cerebrospinal Fluid Diagnostics of Alzheimer's Disease in Patients with Idiopathic Normal Pressure Hydrocephalus.

BACKGROUND: Alzheimer's disease (AD) is the most common cause of dementia worldwide and a frequent comorbidity in idiopathic normal pressure hydrocephalus (iNPH). The presence of AD pathology is associated with worse outcomes after a shunt procedure in iNPH. Preoperative diagnosis of AD is challenging in patients with iNPH, which involves reduced concentrations of the cerebrospinal fluid (CSF) AD biomarkers. OBJECTIVE: Our aim was to estimate the effect size of iNPH as a factor in CSF levels of AD biomarkers and to test if correction could be used to improve diagnostic value. METHODS: Our cohort included 222 iNPH patients with data in the Kuopio NPH registry and brain biopsy and CSF samples available. We divided the patients into groups according to AD pathology per brain biopsy. For control cohorts, we had CSF samples from cognitively healthy individuals (n = 33) and patients with diagnosed AD and no iNPH (n = 39).*-31ptResults:Levels of all investigated biomarkers differed significantly between groups, with the exception of t-Tau levels between healthy individuals and iNPH patients with AD pathology. Applying a correction factor for each biomarker (0.842*Aß1 - 42, 0.779*t-Tau, and 0.610*P-Tau181) for the effect of iNPH yielded a sensitivity of 2.4% and specificity of 100%. The ratio of P-Tau181 to Aß1 - 42 was moderately effective in aiding recognition of AD pathology in iNPH patients (sensitivity 0.79, specificity 0.76, area under the curve 0.824). CONCLUSION: Correcting for iNPH as a factor failed to improve diagnostic effectiveness, but the P-Tau181/Aß1 - 42 ratio showed some utility in the diagnosis of AD in iNPH patients.

Predictors of treatment limitations in Finnish intensive care units.

BACKGROUND: Few studies have examined the factors that predict the limitations of life-sustaining treatment (LST) to patients in intensive care units (ICUs). We aimed to identify variables associated with the decision of withholding of life support (WHLS) at admission, WHLS during ICU stay and the withdrawal of ongoing life support (WDLS). METHODS: This retrospective observational study comprised 17,772 adult ICU patients who were included in the nationwide Finnish ICU Registry in 2016. Factors associated with LST limitations were identified using hierarchical logistic regression. RESULTS: The decision of WHLS at admission was made for 822 (4.6%) patients, WHLS during ICU stay for 949 (5.3%) patients, and WDLS for 669 (3.8%) patients. Factors strongly predicting WHLS at admission included old age (adjusted odds ratio [OR] for patients aged 90 years or older in reference to those younger than 40 years was 95.6; 95% confidence interval [CI], 47.2-193.5), dependence on help for activities of daily living (OR, 3.55; 95% CI, 3.01-4.2), and metastatic cancer (OR, 4.34; 95% CI, 3.16-5.95). A high severity of illness predicted later decisions to limit LST. Diagnoses strongly associated with WHLS at admission were cardiac arrest, hepatic failure and chronic obstructive pulmonary disease. Later decisions were strongly associated with cardiac arrest, hepatic failure, non-traumatic intracranial hemorrhage, head trauma and stroke. CONCLUSION: Early decisions to limit LST were typically associated with old age and chronic poor health whereas later decisions were related to the severity of illness. Limitations are common for certain diagnoses, particularly cardiac arrest and hepatic failure.

Gelatin and the risk of acute kidney injury after cardiac surgery.

BACKGROUND: Gelatin has been used as a plasma volume expander because of its ability to preserve intravascular volume more effectively than crystalloids. However, gelatin may have detrimental effects on kidney function and increase the risk of acute kidney injury (AKI). METHOD: We investigated by retrospective analysis of prospectively collected data whether the administration of 4% succinyl gelatin is associated with an increased risk of AKI after cardiac surgery. We compared two propensity score-matched groups of 1,187 patients (crystalloid group and gelatin group). RESULTS: The incidence of AKI was similar in both groups (gelatin 21% and crystalloid 20%) (p = 0.414). The incidence of moderate AKI (8% vs. 6%) was higher in the gelatin group, but there was no difference in mild or severe AKI. Postoperative serum creatine on the first (70 vs. 70 µmol L-1 , p = 0.689) or fourth (71 vs. 70, p = 0.313) postoperative day was similar between groups and there was no difference in the need for new renal replacement therapy (p = 0.999). Patients in the gelatin group received less crystalloids (2080 ml vs. 4130 ml, p = 0.001) and total fluids (3760 ml vs. 4180 ml, p = 0.001), their fluid balance was less positive (p = 0.001) and they required less vasoactive and inotropic medication (p = 0.001). Gelatin was not associated with increased mortality compared to the crystalloid group. CONCLUSION: Gelatin was not associated with AKI after cardiac surgery.

Elevated CSF LRG and Decreased Alzheimer's Disease Biomarkers in Idiopathic Normal Pressure Hydrocephalus.

Leucine-rich-alpha-2-glykoprotein (LRG) is suggested as a potential biomarker for idiopathic normal pressure hydrocephalus (iNPH). Our goal was to compare the cerebrospinal fluid (CSF) LRG levels between 119 iNPH patients and 33 age-matched controls and with the shunt responses and the brain biopsy Alzheimer's disease (AD) pathology among the iNPH patients. CSF LRG, Aß1-42, P-tau181, and T-tau were measured by using commercial ELISAs. The LRG levels in the CSF were significantly increased in the iNPH patients (p < 0.001) as compared to the controls, regardless of the AD pathology. However, CSF LRG did not correlate with the shunt response in contrast to the previous findings. The CSF AD biomarkers, i.e., Aß1-42, T-tau, and P-tau correlated with the brain biopsy AD pathology as expected but were systematically lower in the iNPH patients when compared to the controls (<0.001). Our findings support that the LRG levels in the CSF are potentially useful for the diagnostics of iNPH, independent of the brain AD pathology, but contrary to previous findings, not for predicting the shunt response. Our findings also suggest a need for specific reference values of the CSF AD biomarkers for the diagnostics of comorbid AD pathology in the iNPH patients.

Bioavailability of oxycodone by mouth in coronary artery bypass surgery patients - a randomized trial.

OBJECTIVE: Pain after coronary artery by-pass (CAB) surgery is severe. Analgesic administration by mouth is unreliable until after gastrointestinal function has recovered. We evaluated the bioavailability of oxycodone co-administered with naloxone by mouth in patients after CAB surgery using either a conventional extracorporeal circulation (CECC) or off-pump surgery (OPCAB). METHODS: Twenty-four patients, 50-73 years, 12 with CECC and 12 with OPCAB, were administered a 10/5 mg oxycodone-naloxone controlled-release tablet by mouth on the preoperative day and for the first seven postoperative days (PODs) thereafter. Blood samples were collected up to 24 h after the preoperative administration, and then randomly either on POD1 and POD3 or on POD2 and POD4. The oxycodone concentration in plasma was analyzed using liquid chromatography-mass spectrometry. RESULTS: On POD1 oxycodone absorption was markedly delayed in five of six patients after CECC and in all six patients after OPCAB surgery; median of tmax after CECC 630 [range 270-1420] minutes and after OPCAB 1020 [720-1410] minutes, compared to median of 120-315 min preoperatively and on POD2-POD4. The carry-over corrected AUC0-24 values on the PODs did not differ from the preoperative values, but were higher on POD3 compared with POD1 in both CECC and OPCAB groups. The rate and extent of oxycodone absorption equaled preoperative values on POD2 and onwards in patients with CAB surgery. CONCLUSIONS: Bioavailability of oxycodone by mouth was similar after CAB surgery via CECC or having OPCAB. Data indicate that POD2 is an appropriate time to start oxycodone administration by mouth after CAB surgery.

Gelatin and the risk of bleeding after cardiac surgery.

BACKGROUND: Gelatins has been used in cardiac surgery because of their ability to preserve intravascular volume better than crystalloids. Unfortunately, gelatin has been associated with impaired coagulation and hemostasis, that may cause increased bleeding. We investigated whether the administration of gelatin increases postoperative bleeding after cardiac surgery. METHODS: Retrospective, observational single-center cohort study in the intensive care unit of a tertiary teaching hospital. Postoperative bleeding, chest tube drainage volume and consumption of blood products were compared between groups. RESULTS: Cohort included 3067 consecutive patients who underwent cardiac surgery. First 1698 patients received gelatin (gelatin group), and 1369 patients did not (crystalloid group). The characteristics of the patients in the gelatin and crystalloid groups were comparable. Postoperative chest tube drainage was 18% (95% CI 11%-20%) greater during the first 12 hours (P < .001) and 15% (95% CI 7%-17%) greater during the first 24 hours (P < .001) in the gelatin group compared to the crystalloid group. Severe and massive postoperative bleeding was more common in the gelatin group compared to the crystalloid group (21% vs 16%, P < .001). Patients in the gelatin group received red blood cells (40% vs 20%, P < .001) and platelets (12% vs 8%, P < .001) more frequently than patients in the crystalloid group. However, the number of administered fresh-frozen plasma transfusions did not differ between the groups. CONCLUSION: Gelatin may increase postoperative bleeding and the need for blood product transfusions after cardiac surgery.

Intensive care patient survival after limiting life-sustaining treatment-The FINNEOL* national cohort study.

BACKGROUND: Few studies have examined survival in intensive care unit (ICU) patients after the restriction of life-sustaining treatment (LST). We aimed to analyse independent factors associated with hospital and 12-month survival rates in ICU patients after treatment restrictions. METHODS: This retrospective observational study examined all patients treated in adult ICUs from 1 January 2016 until 31 December 2016 included in the Finnish ICU Registry. Multivariable logistic regression analysis was performed to explain the effect on survival. RESULTS: Decisions to limit LST were made for 2444 patients (13.7%; 95% CI 13.2-14.2). ICU, hospital, and 12-month survival rates were 71% (95% CI 69-73), 49% (95% CI 47-51), and 24% (95% CI 22-26), respectively. In patients for whom life support was withheld, increased 12-month survival rates were associated with admission from the operating theatre (OR 1.9, 95% CI 1.1-3.4), good pre-hospital physical fitness (OR 4.7, 95% Cl 1.2-16.8) and being housed at home (OR 2.0, 95% Cl 1.4-2.8). Decreased survival rates were associated with admission from a hospital ward (OR 0.67, 95% Cl 0.5-0.9), higher comorbidity (OR 0.6, 95% Cl 0.4-0.9), cancer (OR 0.4, 95%CI 0.2-0.9), greater illness severity (SAPS II; OR 0.98, 95% Cl 0.98-0.99), and higher care intensity (TISS-76; OR 0.93, 95% Cl 0.92-0.95). CONCLUSION: Survival among ICU patients with limited treatment was higher than expected. Advanced age was not associated with higher mortality, potentially because treatment restrictions may be set more easily for older patients.

Impact of minimal invasive extracorporeal circulation on the need of red blood cell transfusion.

OBJECTIVE: Minimal invasive extracorporeal circulation may decrease the need of packed red blood cell transfusions and reduce hemodilution during cardiopulmonary bypass. However, more data are needed on the effects of minimal invasive extracorporeal circulation in more complex cardiac procedures. We compared minimal invasive extracorporeal circulation and conventional extracorporeal circulation methods of cardiopulmonary bypass. METHODS: A total of 424 patients in the minimal invasive extracorporeal circulation group and 844 patients in the conventional extracorporeal circulation group undergoing coronary artery bypass grafting and more complex cardiac surgery were evaluated. Age, sex, type of surgery, and duration of perfusion were used as matching criteria. Hemoglobin <80 g/L was used as red blood cell transfusion trigger. The primary endpoint was the use of red blood cells during the day of operation and the five postoperative days. Secondary endpoints were hemodilution (hemoglobin drop after the onset of perfusion) and postoperative bleeding from the chest tubes during the first 12 hours after the operation. RESULTS: Red blood cell transfusions were needed less often in the minimal invasive extracorporeal circulation group compared to the conventional extracorporeal circulation group (26.4% vs. 33.4%, p = 0.011, odds ratio 0.72, 95% confidence interval 0.55-0.93), especially in coronary artery bypass grafting subgroup (21.3% vs. 35.1%, p < 0.001, odds ratio 0.50, 95% confidence interval 0.35-0.73). Hemoglobin drop after onset of perfusion was also lower in the minimal invasive extracorporeal circulation group than in the conventional extracorporeal circulation group (24.2 ± 8.5% vs. 32.6 ± 12.6%, p < 0.001). Postoperative bleeding from the chest tube did not differ between the groups (p = 0.808). CONCLUSION: Minimal invasive extracorporeal circulation reduced the need of red blood cell transfusions and hemoglobin drop when compared to the conventional extracorporeal circulation group. This may have implications when choosing the perfusion method in cardiac surgery.

Vasoactive-inotropic score and the prediction of morbidity and mortality after cardiac surgery.

BACKGROUND: The vasoactive-inotropic score (VIS) predicts mortality and morbidity after paediatric cardiac surgery. Here we examined whether VIS also predicted outcome in adults after cardiac surgery, and compared predictive capability between VIS and three widely used scoring systems. METHODS: This single-centre retrospective cohort study included 3213 cardiac surgery patients. Maximal VIS (VISmax) was calculated using the highest doses of vasoactive and inotropic medications administered during the first 24 h post-surgery. We established five VISmax categories: 0-5, >5-15, >15-30, >30-45, and >45 points. The predictive accuracy of VISmax was evaluated for a composite outcome, which included 30-day mortality, mediastinitis, stroke, acute kidney injury, and myocardial infarction. RESULTS: VISmax showed good prediction accuracy for the composite outcome [area under the curve (AUC), 0.72; 95% confidence interval (CI), 0.69-0.75]. The incidence of the composite outcome was 9.6% overall and 43% in the highest VISmax group (>45). VISmax predicted 30-day mortality (AUC, 0.76; 95% CI, 0.69-0.83) and 1-yr mortality (AUC, 0.70; 95% CI, 0.65-0.74). Prediction accuracy for unfavourable outcome was significantly better with VISmax than with Acute Physiology and Chronic Health Evaluation II (P=0.01) and Simplified Acute Physiological Score II (P=0.048), but not with the Sequential Organ Failure Assessment score (P=0.32). CONCLUSIONS: In adults after cardiac surgery, VISmax predicted a composite of unfavourable outcomes and predicted mortality up to 1 yr after surgery.

Continuous Ropivacaine Infusion Offers No Benefit in Treating Postoperative Pain After Cardiac Surgery.

OBJECTIVE: One multimodal pain management method for reducing postoperative opioid need after cardiac surgery is to continuously infuse local anesthetic into a median sternotomy wound. Previous studies have shown contradictory results with this method; therefore, no consensus exists on its effectiveness. The authors tested the effectiveness of continuous 0.2% ropivacaine infusion into a sternotomy wound after cardiac surgery. DESIGN: Prospective, randomized, double-blinded, placebo-controlled trial. SETTING: Single-institution, tertiary-level, university hospital. PARTICIPANTS: Total of 90 patients undergoing coronary artery bypass grafting or heart valve surgery. INTERVENTIONS: Patients were assigned randomly to receive 0.2% ropivacaine or placebo into a sternotomy wound for 48 hours postoperatively. Pain was controlled with standardized oxycodone boluses after surgery and patient-controlled analgesia oxycodone after extubation; total oxycodone consumption was recorded. Pain was assessed 3  times daily, at rest and during deep breathing, with the visual analogue scale. MEASUREMENTS AND MAIN RESULTS: Forty-seven patients were assigned to receive ropivacaine and 43 to receive placebo infusion. Cumulative oxycodone consumption was 97 ± 27 mg with ropivacaine and 96 ± 29 mg with placebo (p = 0.813). Pain scores were similar between groups, both at rest (p = 0.630) and during deep breathing (p = 0.793). Adverse event incidences and surgical wound infection rates were similar between groups. CONCLUSION: Continuous 0.2% ropivacaine infusions at the median sternotomy wound did not reduce postoperative pain or opioid consumption during the first 48 hours after cardiac surgery. This technique apparently was not beneficial for post-sternotomy pain treatment.

Levosimendan increases bleeding risk after heart valve surgery: a retrospective analysis of a randomized trial.

OBJECTIVE: To investigate whether levosimendan, an inotrope with cardioprotective properties, increases postoperative bleeding after cardiac surgery. DESIGN: Retrospective analysis of a randomized, prospective clinical study. SETTING: Post-anesthesia care unit (PACU) and surgical ward in a university hospital. PARTICIPANTS: Two hundred heart valve surgery patients. INTERVENTIONS: The patients were randomized to receive either a 24-hour intravenous infusion of levosimendan or placebo. Infusion was administered as a 24 µg/kg bolus over 30 minutes and then continued at a dose of 0.2 µg/kg/min. MEASUREMENTS AND MAIN RESULTS: Postoperative bleeding was approximately 31% greater in the levosimendan group (1050 mL) compared to the placebo group (880 mL, p = 0.008). Serious bleeding exceeding 1000 mL was more common in the levosimendan group than the placebo group (51 v 38 patients, p = 0.044, risk ratio (RR) 1.37, 95% CI 1.00-1.87). However, the risk of reoperation for bleeding did not increase if patients received levosimendan (RR 1.52, 95% CI 0.77-2.97, p = 0.309). This result did not change after excluding patients who received clopidogrel preoperatively (RR 2.13, 95% CI 0.98-4.65, p = 0.145). The groups did not differ regarding transfused blood products. Eight patients, including seven from the levosimendan group, had delayed (diagnosed>48 hours after the surgery) cardiac tamponade and underwent re-exploration (7 v 1, p = 0.031). CONCLUSIONS: Levosimendan increased the risk of postoperative bleeding after cardiac valve surgery. In addition, the risk of postoperative cardiac tamponade was increased in patients who received levosimendan compared to placebo.

Comparison of spectral entropy and BIS VISTA™ monitor during general anesthesia for cardiac surgery.

OBJECTIVES: We compared the primary metrics of the Spectral entropy M-ENTROPY™ module and BIS VISTA™ monitor-i.e., bispectral index (BIS), state entropy (SE), and response entropy (RE) in terms of agreement and correlation during general anesthesia for cardiac surgery. We also evaluated responsiveness of electroencephalogram (EEG)-based and hemodynamic parameters to surgical noxious stimulation, skin incision, and sternotomy, hypothesizing that RE would be a better responsiveness predictor. METHODS: BIS and entropy sensors were applied before anesthesia induction in 32 patients having elective cardiac surgery. Total intravenous anesthesia was standardized and guided by the BIS index with neuromuscular blockade tested with train-of-four monitoring. Parameters included SE, RE, BIS, forehead electromyography (EMG), and hemodynamic variables. Time points for analyzing BIS, entropy, and hemodynamic values were 1 min before and after: anesthesia induction, intubation, skin incision, sternotomy, cannulation of the aorta, cardiopulmonary bypass (CPB), cross-clamping the aorta, de-clamping the aorta, and end of CPB; also after starting the re-warming phase and at 10, 20, 30, and 40 min following. RESULTS: The mean difference between BIS and SE (Bland-Altman) was 2.14 (+16/- 11; 95% CI 1.59-2.67), and between BIS and RE it was 0.02 (+14/- 14; 95% CI 0.01-0.06). BIS and SE (r(2) = 0.66; P = 0.001) and BIS and RE (r(2) = 0.7; P = 0.001) were closely correlated (Pearson's). EEG parameters, EMG values, and systolic blood pressure significantly increased after skin incision, and sternotomy. The effect of surgical stimulation (Cohen's d) was highest for RE after skin incision (-0.71; P = 0.0001) and sternotomy (-0.94; P = 0.0001). CONCLUSION: Agreement was poor between the BIS index measured by BIS VISTA™ and SE values at critical anesthesia time points in patients undergoing cardiac surgery. RE was a good predictor of arousal after surgical stimulation regardless of the surgical level of muscle relaxation. Index differences most likely resulted from different algorithms for calculating consciousness level.

Can BIS monitoring be used to assess the depth of propofol anesthesia in the treatment of refractory status epilepticus?

PURPOSE: Appropriate treatment of generalized convulsive refractory status epilepticus (RSE) requires general anesthesia in the intensive care unit (ICU) with continuous electroencephalography (cEEG) monitoring. During out of office hours and weekends, cEEG monitoring is not always available. The Bispectral Index (BIS) monitor can be used to assess the hypnotic component of general anesthesia. We conducted a study to evaluate the feasibility of using the BIS monitoring to assess the burst suppression (BS) pattern during propofol anesthesia in RSE. METHODS: Ten adult patients with RSE admitted to the ICU were monitored simultaneously with cEEG and BIS monitoring. We compared the BIS and suppression ratio (SR) values with the EEG burst suppression pattern when the depth of anesthesia was titrated to the BS level monitoring by cEEG. RESULTS: We found an excellent correlation between the cEEG burst rate per minute and the BIS (r² =-0.9; p< 0.001) and SR (r² = -0.88; p < 0.001). The sensitivity and specificity of BIS score of 30 to detect BS in electroencephalography were 99% and 98%, respectively. The BIS monitor was not able to recognize regional epileptic activity and epileptic bursts during the BS pattern. DISCUSSION: The cEEG can be considered as the primary monitoring technique in the assessment of the depth of anesthesia in the treatment of RSE. If cEEG is not available, the BIS monitor can be used to guide the level of anesthesia, targeting BS in patients with RSE.

Is external jugular vein cannulation feasible in emergency care? A randomised study in open heart surgery patients.

UNLABELLED: The optimal intravenous catheterisation site for emergencies is unknown. The external jugular vein might be preferable route compared to cubital veins in emergencies due to more rapid circulation time to heart and faster cardiac responses. However, the feasibility of the different venous catheterisation sites has not been compared in relation to catheterisation time and success rate. METHODS: We examined the time differences and success rates of external jugular compared to antecubital vein catheterisations. 32 paramedics and 28 emergency department residents performed external jugular and antecubital venous catheterisations on anesthetized patients scheduled for elective cardiac surgery. The primary outcome was catheterisation time and the secondary outcomes the failure rate and catheterisation times needed to succeed. RESULTS: Antecubital venous catheterisation was faster (113+/-89s) compared to external jugular vein catheterisation (156+/-112s), p=0.008 and the success rate was higher (93% compared to 68%, respectively, p=0.001). Less attempts were needed for antecubital vein catheterisations compared to external jugular vein catheterisations (p=0.002). For the antecubital vein, subjects needed two attempts in 6 patients and three attempts in 6 patients. For the external jugular vein, subjects needed two attempts in 13 patients and three attempts in 20 patients. Two (6%) paramedics and two (7%) residents failed to catheterise the antecubital vein. Nine (28%) paramedics and 10 (36%) residents failed to catheterise the external jugular vein. CONCLUSIONS: Antecubital vein catheterisation was faster and had a superior success rate compared to external jugular vein catheterisation.

Midlatency auditory-evoked potentials in the assessment of sedation in cardiac surgery patients.

OBJECTIVES: Midlatency auditory-evoked potentials (MLAEPs) may provide an objective measure of depth of sedation. The aim of this study was to evaluate MLAEPs for measuring sedation in cardiac surgery patients. DESIGN: Prospective study. SETTING: Intensive care unit of a university hospital. PARTICIPANTS: Twenty-two patients scheduled for elective coronary artery bypass grafting. INTERVENTIONS: MLAEPs were obtained at 5 time points: the day before surgery (baseline), 1 hour before surgery, after premedication, postoperatively during deep (Ramsay 6) and moderate (Ramsay 4) sedation, and the day after surgery. MEASUREMENTS AND MAIN RESULTS: The latency of the Nb MLAEP component increased from 44 ms (38-60 ms; median, range) at baseline to 49 ms (41-64 ms) after premedication (p = 0.03) and further to 63 ms (48-80 ms) during deep sedation after surgery (P < 0.01). Although a decreasing clinical level of sedation after rewarming was not associated with a significant change in Nb latency (61 ms [42-78 ms]), the MLAEP NaPa amplitude increased from 0.9 muV (0.4-1.6 microV) to 1.3 muV (0.8-3.9 microV; p = 0.01). Nb latency remained increased the day after surgery (49 ms [37-71 ms]) as compared with baseline (p < 0.01). CONCLUSIONS: MLAEP latencies can reflect subtle changes in auditory perception, while amplitudes seem to change with transition between deep levels of sedation.

N100 auditory potential and electroencephalogram discriminate propofol-induced sedation levels.

OBJECTIVE: In the present study, we evaluated the electroencephalogram (EEG) and auditory N100 potential (N100) before and during propofol-induced sedation. The aim was to test whether using EEG and N100 the level of sedation may be evaluated. METHODS: Twenty-nine cardiac surgery patients were studied. The EEG signal and the N100 potential were recorded at awake one day before the cardiac operation and two times after the operation, when the clinical level of postoperative propofol sedation was considered deep (Ramsay Score 6) and moderate (Ramsay Score 4). Discriminant analysis was used to select those spectral EEG and/or N100 variables which would predict the correct level of sedation best. The final classification was based on canonical discriminant functions and Mahalanobis' distance. RESULTS: The spectral EEG variables (slow/fast-ratio, delta, and beta2 powers) predicted the correct level of sedation with 81% (canonical discriminant functions) and 80% (Mahalanobis' distance) accuracy. Similarly, the N100 (amplitude, latency, and the first principal component) predicted the correct level of sedation with 91% and 92% accuracy, and the combination of the EEG and N100 with 96% and 93% accuracy. CONCLUSIONS: Our findings suggest that the combined use of EEG and N100 may help to differentiate the propofol-induced sedation levels, and thus be a useful compliment to clinical sedation scales.

Assessment of postoperative sedation level with spectral EEG parameters.

OBJECTIVES: Several sedation scores have been developed, but still a need exists for an objective method to monitor sedation level during intensive care. Our study presents a procedure for finding a combination of electroencephalogram (EEG) characteristics, which could be used in estimating sedation level. METHODS: We measured EEG in 29 cardiac surgical patients prior to and after the cardiac bypass grafting operation at different sedation levels. The clinical assessment of sedation levels was evaluated with the Ramsay Score. Spectral EEG parameters were computed and a linear model to predict postoperative sedation level was constructed by using principal component analysis and regression analysis. RESULTS: Sedation levels modified all computed spectral EEG parameters. The model based on optimal combination of EEG parameters predicted the observed Ramsay Score value with a prediction probability of 88%. CONCLUSIONS: This study suggests that a combination of spectral EEG parameters may discriminate between 3 sedation levels: awake, moderate sedation and deep sedation.

Evidence of auditory processing during postoperative propofol sedation.

OBJECTIVES: Our aim was to characterize cerebral event-related responses, which index the detection of auditory stimuli during postoperative sedation. METHODS: We monitored auditory event-related potentials (ERPs) before and after elective cardiac operation in 29 patients. Sedation levels, induced with propofol, were evaluated clinically with Ramsay score (RS). RESULTS: During deep sedation (RS 6), patients could be categorized into 3 groups according to ERP responses evoked by a standard 'oddball' paradigm. In one group, there were no cortical responses indexing the detection of a sound (N100), another group showed clear responses, and the third group was characterized by a later P300a component which was taken to reflect orienting to a novel stimulus in adults who were awake. However, in deep sedation, P300a did not show behaviour characteristic to an orienting reaction. In moderate sedation (RS 4), all the patients showed a visible N100. Total sedative propofol dose, hemodynamics and the spontaneous electroencephalography (EEG) were not connected to the category of an individual's responses. CONCLUSIONS: The results of our study suggest that the detection and automatic auditory information processing function during postoperative sedation, and may signal the individual stages of awakening in a sensitive way. In addition, the findings suggest a deficit in sensory memory function during sedation.