Pharmacodynamic Model of the Hemodynamic Effects of Propofol and Remifentanil and Their Interaction with Noxious Stimulation.

: Despite the known impact of propofol and remifentanil on hemodynamics and patient outcomes, there is a lack of comprehensive quantitative analysis, particularly in surgical settings, considering the influence of noxious stimuli. The aim of this study was to develop a quantitative semi-mechanistic population model that characterized the time course changes in mean arterial pressure (MAP) and heart rate (HR) due to the effects of propofol, remifentanil, and different types of noxious stimulation related to the clinical routine. : Data from a prospective study were used; the study analyzed the effects of propofol and remifentanil general anesthesia on female patients in physical status of I-II according to the American Society of Anesthesiologists (ASA I-II) undergoing gynecology surgery.

Mechanism-Based Modeling of Perioperative Variations in Hemoglobin Concentration in Patients Undergoing Laparoscopic Surgery.

Background: Hemoglobin concentration ([Hb]) in the perioperative setting should be interpreted in the context of the variables and processes that may affect it to differentiate the dilution effects caused by changes in intravascular volume. However, it is unclear what variables and processes affect [Hb]. Here, we modeled the perioperative variations in [Hb] to identify the variables and processes that govern [Hb] and to describe their effects.

Effects of remifentanil on brain responses to noxious stimuli during deep propofol sedation.

Background: The safety of anaesthesia has improved as a result of better control of anaesthetic depth. However, conventional monitoring does not inform on the nature of nociceptive processes during unconsciousness. A means of inferring the quality of potentially painful experiences could derive from analysis of brain activity using neuroimaging.

Semimechanistic models to relate noxious stimulation, movement, and pupillary dilation responses in the presence of opioids.

Intraoperative targeting of the analgesic effect still lacks an optimal solution. Opioids are currently the main drug used to achieve antinociception, and although underdosing can lead to an increased stress response, overdose can also lead to undesirable adverse effects. To better understand how to achieve the optimal analgesic effect of opioids, we studied the influence of remifentanil on the pupillary reflex dilation (PRD) and its relationship with the reflex movement response to a standardized noxious stimulus.

Bilateral Bispectral Index Monitoring Performance in the Detection of Seizures in Nonanesthetized Epileptic Patients: An Observational Study.

Background: The aim of this observational study was to determine whether bilateral bispectral index (BIS) monitoring can detect seizures in epileptic patients.

Methods: Four-channel frontal BIS monitoring and standard 40-channel electroencephalography monitoring were conducted in epileptic patients undergoing evaluation for epilepsy surgery. The BIS numerical value, signal quality index, electromyography, suppression ratio, and color density spectral array were continuously recorded.

Current status of perioperative hypnotics, role of benzodiazepines, and the case for remimazolam: a narrative review.

Anaesthesiologists and non-anaesthesiologist sedationists have a limited set of available i.v. hypnotics, further reduced by the withdrawal of thiopental in the USA and its near disappearance in Europe.

Influence of an "Electroencephalogram-Based" Monitor Choice on the Delay Between the Predicted Propofol Effect-Site Concentration and the Measured Drug Effect.

Background: Clinicians can optimize propofol titration by using 2 sources of pharmacodynamic (PD) information: the predicted effect-site concentration for propofol (Ceprop) and the electroencephalographically (EEG) measured drug effect. Relation between these sources should be time independent, that is, perfectly synchronized. In reality, various issues corrupt time independency, leading to asynchrony or, in other words, hysteresis.

Foreseeing postoperative pain in neurosurgical patients: pupillometry predicts postoperative pain ratings-an observational study.

Pupillary reflex dilation (PRD) is triggered by noxious stimuli and diminished by opioid administration. In the postoperative period, PRD has been shown to be correlated with pain reporting and a useful tool to guide opioid administration. In this study we assessed whether pupillary measurements taken before extubation were related with the patient's reported pain in the Post-Anesthesia Care Unit (PACU) using the Numerical Rating Scale (NRS).

Perioperative blood loss: estimation of blood volume loss or haemoglobin mass loss?

Background: Perioperative blood loss is an essential parameter in research into Patient Blood Management. However, currently there is no "gold standard" method to quantify it. Direct measurements of blood loss are considered unreliable methods, and the formulae to estimate it have proven to be significantly inaccurate.

Refined Multiscale Entropy Using Fuzzy Metrics: Validation and Application to Nociception Assessment.

The refined multiscale entropy (RMSE) approach is commonly applied to assess complexity as a function of the time scale. RMSE is normally based on the computation of sample entropy (SampEn) estimating complexity as conditional entropy. However, SampEn is dependent on the length and standard deviation of the data.

Entropy Measures as Descriptors to Identify Apneas in Rheoencephalographic Signals.

Rheoencephalography (REG) is a simple and inexpensive technique that intends to monitor cerebral blood flow (CBF), but its ability to reflect CBF changes has not been extensively proved. Based on the hypothesis that alterations in CBF during apnea should be reflected in REG signals under the form of increased complexity, several entropy metrics were assessed for REG analysis during apnea and resting periods in 16 healthy subjects: approximate entropy (ApEn), sample entropy (SampEn), fuzzy entropy (FuzzyEn), corrected conditional entropy (CCE) and Shannon entropy (SE). To compute these entropy metrics, a set of parameters must be defined a priori, such as, for example, the embedding dimension m, and the tolerance threshold r.

Pharmacodynamic modelling of the effect of remifentanil using the Pupillary Pain Index.

Using a targeted controlled infusion of remifentanil during total intravenous anesthesia, we investigated the effect-site concentrations of remifentanil that correlate with different values of the Pupillary Pain Index and which concentrations were necessary for achieving a Pupillary Pain Index ≤ 4 and its usefulness in titrating opioids. The Pupillary Pain Index was measured in 54 patients prior to surgery under different remifentanil effect-site concentrations and subsequently modeled. One hundred and twenty-eight measurements were taken at different remifentanil concentrations while titrating propofol for a similar depth of hypnosis using a BIS monitor.

Poincaré plot analysis of cerebral blood flow signals: Feature extraction and classification methods for apnea detection.

Objective: Rheoencephalography is a simple and inexpensive technique for cerebral blood flow assessment, however, it is not used in clinical practice since its correlation to clinical conditions has not yet been extensively proved. The present study investigates the ability of Poincaré Plot descriptors from rheoencephalography signals to detect apneas in volunteers.

Methods: A group of 16 subjects participated in the study.

Tools to screen and measure cognitive impairment after surgery and anesthesia.

Cognition is essential to all aspects of our everyday life. Although we take our cognitive function for granted, the perioperative period is prone to several aggressions that might impair it. Postoperative cognitive dysfunction, has been the aim of many studies recently, and was shown to be very common with an incidence that can reach 40%, yielding not only impairment in cognition, but also longer hospital stays, higher costs and greater mortality.

Computerized tests to evaluate recovery of cognitive function after deep sedation with propofol and remifentanil for colonoscopy.

The use of sedation for diagnostic procedures including gastrointestinal endoscopy is rapidly growing. Recovery of cognitive function after sedation is important because it would be important for most patients to resume safe, normal life soon after the procedure. Computerized tests have shown being accurate descriptors of cognitive function.

Time-frequency Features for Impedance Cardiography Signals During Anesthesia Using Different Distribution Kernels.

Objective: This works investigates the time-frequency content of impedance cardiography signals during a propofol-remifentanil anesthesia.

Materials And Methods: In the last years, impedance cardiography (ICG) is a technique which has gained much attention. However, ICG signals need further investigation.

Effects of Ketamine on Pupillary Reflex Dilation: A Case Report.

Ketamine is an important component of multimodal treatment and a commonly used anesthetic drug. However, its analgesic effects have not been fully assessed intraoperatively because of difficulties in measuring this effect. In this case report, a woman underwent general anesthesia with ketamine and its pupillary reflexes were measured to detect autonomic changes in response to pain.

Assessment of sedation-analgesia by means of Poincaré analysis of the electroencephalogram.

Monitoring the levels of sedation-analgesia may be helpful for managing patient stress on minimally invasive medical procedures. Monitors based on EEG analysis and designed to assess general anesthesia cannot distinguish reliably between a light and deep sedation. In this work, the Poincaré plot is used as a nonlinear technique applied to EEG signals in order to characterize the levels of sedation-analgesia, according to observed categorical responses that were evaluated by means of Ramsay Sedation Scale (RSS).

A randomized comparison of the Ambu AuraGain versus the LMA supreme in patients undergoing gynaecologic laparoscopic surgery.

Second generation supraglottic airway devices providing high seal airway pressures are suitable for patients undergoing gynecologic laparoscopy. We compared the seal pressure achieved by the new Ambu AuraGain™ versus LMA Supreme™ following pneumoperitoneum in the Trendelenburg position. Sixty female patients were randomly allocated to ventilation with either the AuraGain or the Supreme.

Influence of general anaesthesia on the brainstem.

The exact role of the brainstem in the control of body functions is not yet well known and the same applies to the influence of general anaesthesia on brainstem functions. Nevertheless in all general anaesthesia the anaesthesiologist should be aware of the interaction of anaesthetic drugs and brainstem function in relation to whole body homeostasis. As a result of this interaction there will be changes in consciousness, protective reflexes, breathing pattern, heart rate, temperature or arterial blood pressure to name a few.

Comparison of the qCON and qNOX indices for the assessment of unconsciousness level and noxious stimulation response during surgery.

The objective of this work is to compare the performances of two electroencephalogram based indices for detecting loss of consciousness and loss of response to nociceptive stimulation. Specifically, their behaviour after drug induction and during recovery of consciousness was pointed out. Data was recorded from 140 patients scheduled for general anaesthesia with a combination of propofol and remifentanil.