Target-controlled infusion of propofol and remifentanil in cardiac anaesthesia: influence of age on predicted effect-site concentrations

Unwanted spontaneous responsiveness and burst suppression in patients undergoing entropy-guided total intravenous anesthesia with target-controlled infusion: An observational prospective trial

STUDY OBJECTIVE

To estimate the incidence of unwanted spontaneous responsiveness and burst suppression (BSupp) in patients undergoing state entropy (SE) and surgical pleth index (SPI)-guided total intravenous anesthesia (TIVA) with target-controlled infusion (TCI).

DESIGN

Observational, prospective, single-center study.

SETTINGS

Operating room.

PATIENTS

107 adult (<65 years) and elderly (≥65 years) women undergoing breast surgery.

INTERVENTIONS

Propofol-remifentanil TIVA-TCI-guided by SE for depth of anesthesia monitoring (target value 40-60) and SPI for antinociception monitoring (target value 20-50) without neuromuscular blockade.

MEASUREMENTS

Age; body mass index; American Society of Anesthesiologists physical status classification; concentration at the effect site of propofol (CeP) and remifentanil (CeR) at loss of responsiveness (LoR), median during anesthesia maintenance (MdM), and at return of responsiveness (RoR); propofol infusion duration; incidence of postoperative delirium (POD) with Confusing Assessment Method for the Intensive Care Unit.

MAIN RESULTS

During SE-SPI-guided TIVA-TCI, 13.1% of patients showed unwanted spontaneous responsiveness, whereas 45.8% showed BSupp. Unwanted spontaneous responsiveness was observed mainly in adults (p < 0.05), and higher CeP RoR (p < 0.05) was registered. BSupp was observed mainly in patients showing a lower CeP MdM (p < 0.01) and CeP RoR (p < 0.05). Unwanted spontaneous responsiveness and BSupp were not associated with significant differences in CeRs. An age-related hysteresis effect was observed, resulting in higher CeP LoR than CeP RoR (p < 0.001). 12.2% of patients showed POD. Only preoperative serum albumin was associated with increased likelihood of POD (p = 0.046).

CONCLUSIONS

The SE-SPI-guided TIVA-TCI did not prevent unwanted spontaneous responsiveness and BSupp. CeP RoR may be used as a proxy for anesthetic sensitivity.

Reliability of the Minto model for target-controlled infusion of remifentanil during cardiac surgery with cardiopulmonary bypass

BACKGROUND

The Minto pharmacokinetic model is used for target-controlled infusion of remifentanil. The reliability of this model has never been evaluated during normothermic cardiac surgery with cardiopulmonary bypass (CPB). The aim of this study was to assess the predictive performance of the model during CPB to determine its reliability during cardiac surgery.

METHODS

This was a single-centre observational study. Arterial blood samples were drawn at five time points: T1, after tracheal intubation; T2, immediately before CPB; T3, 10 min after starting CPB; T4, 45 min after starting CPB; T5, 10 min after weaning off CPB. Prediction error (PE) and absolute prediction error (APE) were calculated for each sample and used to determine median prediction error (MDPE) and median absolute prediction error (MDAPE) per patient. Risk factors for APE >30% were assessed using multivariable analysis. Results are presented as medians with inter-quartile ranges.

RESULTS

Fifty-eight patients with 283 blood samples (110 during CPB) were included. In the pre-CPB period, MDPE and MDAPE were -17.3 [-32.9 to 2.3] and 24.6 [12-37.7]%, whereas during CPB, they were -1.8 [-15.6 to 11.1] and 14.0 [6.74-27.1]%, respectively. There was no statistically significant difference between measured and predicted remifentanil plasma concentrations during CPB. Age, preoperative albumin concentrations, temperature, and haemodilution were not independently associated with MDAPE >30%.

CONCLUSIONS

The Minto model accurately predicts plasma remifentanil concentrations during cardiac surgery with CPB.

CLINICAL TRIAL REGISTRATION

2017-A03153-50.

Feasibility and postoperative opioid sparing effect of an opioid-free anaesthesia in adult cardiac surgery: a retrospective study

Background

No previous study investigated the dexmedetomidine-based opioid-free anesthesia (OFA) protocol in cardiac surgery. The main objective of this study was to evaluate the feasibility and the postoperative opioid-sparing effect of dexmedetomidine-based OFA in adult cardiac surgery patients.

Methods

We conducted a single-centre and retrospective study including 80 patients above 18 years old who underwent on-pump cardiac surgery between November 2018 and February 2020. Patients were divided into two groups: OFA (lidocaine, ketamine, dexmedetomidine, MgSO4) or opioid-based anaesthesia (remifentanil and anti-hyperalgesic medications such as ketamine and/or MgSO4 and/or lidocaine at the discretion of the anesthesiologist). The primary endpoint was the total amount of opioid consumed in its equivalent of intravenous morphine during the first 48 postoperative hours. Secondary outcomes included perioperative hemodynamics, post-operative maximal pain at rest and during coughing and adverse outcomes. Data are expressed as median [interquartile range].

Results

Patients in the OFA-group had a higher EuroSCORE II, with more diabetes, more dyslipidemia and more non-elective surgery but fewer smoking history. In the OFA group, the median loading dose of dexmedetomidine was 0.6 [0.4–0.6] μg.kg^− 1 while the median maintenance dose was 0.11 μg.kg^− 1.h^− 1 [0.05–0.20]. In 10 (25%) patients, dexmedetomidine was discontinued for a drop of mean arterial pressure below 55 mmHg. The median total amount of opioid consumed in its equivalent of intravenous morphine during the first 48 postoperative hours was lower in the OFA group (15.0 mg [8.5–23.5] versus 30.0 mg [17.3–44.3], p < 0.001). While no differences were seen with rest pain (2.0 [0.0–3.0] versus 0.5 [0.0–5.0], p = 0.60), the maximal pain score during coughing was lower in OFA group (3.5 [2.0–5.0] versus 5.5 [3.0–7.0], p = 0.04). In OFA group the incidence of atrial fibrillation (18% versus 40%, p = 0.03) and non-invasive ventilation use (25% versus 48%, p = 0.04) were lower. The incidence of bradycardia and the intraoperative use of norepinephrine were similar between both groups.

Conclusion

Dexmedetomidine-based OFA in cardiac surgery patients is feasible and could be associated with a lower postoperative morphine consumption and better postoperative outcomes. Further randomized studies are required to confirm these promising results and determine the optimal associations, dosages, and infusion protocols during cardiac surgery.

Graphical abstract

Supplementary Information

The online version contains supplementary material available at 10.1186/s12871-021-01362-1.

Age influences on Propofol estimated brain concentration and entropy during maintenance and at return of consciousness during total intravenous anesthesia with target-controlled infusion in unparalyzed patients: An observational prospective trial

PURPOSE

Aging affects pharmacodynamics/pharmacokinetics of anesthetics, but age effects on Entropy-guided total intravenous anesthesia with target-controlled infusions (TIVA-TCI) are not fully characterized. We compared aging effects on effective estimated brain concentration of Propofol (CeP) during TIVA-TCI Entropy-guided anesthesia, without neuromuscular blockade (NMB).

METHODS

We performed an observational, prospective, single-center study enrolling 75 adult women undergoing Entropy-guided Propofol-Remifentanil TIVA-TCI for breast surgery. Primary endpoint was the relationship between age and CeP at maintenance of anesthesia (MA) during Entropy-guided anesthesia. Secondary endpoints were relationships between age and CeP at arousal reaction (AR), return of consciousness (ROC) and explicit recall evenience. We calculated a linear model to evaluate the age's impact on observational variable and performed pairwise tests to compare old (≥65 years, n = 50) and young (<65 years, n = 25) patients or patients with and without an AR.

RESULTS

We did not observe age-related differences in CeP during MA, but CeP significantly (p = 0,01) decreased with age at ROC. Entropy values during MA increased with age and were significantly higher in the elderly (RE: median 56[IQR49.3-61] vs 47.5[42-52.5],p = 0.001; SE: 51.6[45-55.5] vs 44[IQR40-50],p = 0.005). 18 patients had an AR, having higher maximum RE (92.5[78-96.3] vs 65[56.5-80.5],p<0.001), SE (79[64.8-84] vs 61[52.5-69],p = 0.03, RE-SE (12.5[9.5-16.5] vs 6 [3-9],p<0.001.

CONCLUSION

Older age was associated with lower CeP at ROC, but not during MA in unparalysed patients undergoing breast surgery. Although RE and SE during MA, at comparable CeP, were higher in the elderly, Entropy, and in particular an increasing RE-SE, is a reliable index to detect an AR.

A Comparison of Different Remifentanil Effect-Site Concentrations to Allow for Early Extubation After Cardiac Surgery

OBJECTIVES

Assess different remifentanil effect-site concentrations (Ce) for readiness for extubation time after cardiac surgery.

DESIGN

Prospective, randomized, blinded, controlled study.

DESIGN

Single university hospital.

PARTICIPANTS

Seventy-three patients scheduled for cardiac surgery.

INTERVENTIONS

After ethical approval, patients scheduled for cardiac surgery with target-controlled propofol infusion were randomly assigned to receive remifentanil effect-site concentrations (Ce) of 1, 2, or 3 ng/mL (n = 25, 25, and 23, respectively).

MEASUREMENTS AND MAIN RESULTS

The primary endpoint was readiness for extubation. Secondary outcomes were also recorded, including the cumulative doses and number of changes of propofol and remifentanil, hemodynamic variables, time to spontaneous eye opening and breathing, actual extubation, incidences of light anesthesia and myocardial ischemia, need for vasopressors and inotropes, and intensive care unit (ICU) and hospital stays. There was no difference in the time to readiness for extubation in any of the groups (0.1 ng/mL: 11.5 min (5-37); 0.2 ng/mL: 22 min (10-35); and 0.3 ng/mL: 21 min (10-49), p < 0.532); however, there was a significant difference among the 3 groups regarding the cumulative remifentanil doses (p < 0.001). Time to spontaneous eye opening and breathing, actual extubation, use of vasopressors and inotropes, incidences of light anesthesia and myocardial ischemia, and length of ICU and hospital stay were similar for all groups. Forty-six of the 73 patients were extubated on-table.

CONCLUSION

Remifentanil Ce 1, 2, and 3 ng/mL produced comparative effects on time to extubation and hemodynamic responses to cardiac surgery. The 3 Ce resulted in immediate on-table extubation in 50% of patients.

Age progression from vicenarians (20-29 year) to nonagenarians (90-99 year) among a population pharmacokinetic/pharmacodynamic (PopPk-PD) covariate analysis of propofol-bispectral index (BIS) electroencephalography

BACKGROUND

Pharmacokinetic/pharmacodynamic (PK/PD) modeling has made an enormous contribution to intravenous anesthesia. Because of their altered physiological, pharmacological and pathological aspects, titrating general anesthesia in the elderly is a challenging task.

METHODS

Eighty patients were consecutively enrolled divided by decades from vicenarians (20-29 year) to nonagenarians (90-99 year) into eight groups. Using target controlled infusion (TCI) and electroencephalographic (EEG)-derived bispectral index (BIS) we set propofol plasma concentration (C_p) to gradually reach 3.5 μg mL^-1 over 3.5-min. In each patient, we constructed a PK/PD model and conducted a population PK/PD (PopPK-PD) covariate analysis.

RESULTS

Age was significant covariate for baseline BIS effect (E₀), inhibitory propofol concentration at 50% BIS decline (IC₅₀) and maximum BIS decline (E_max). First-order rate constant K_e0 of 0.47 min^-1 in vicenarians (20-29 year) gradually increased with age-progression to 1.85 min^-1 in nonagenarians (90-99 year). Simulation modelling showed that clinically recommended C_p of 3.5 μg mL^-1 for 20-29 year BIS 50 should be reduced to 3.0 for 30-49 year, 2.5 for 50-69 year and 2.0 for 80-89 year.

CONCLUSION

We quantified and graded EEG-BIS age-progression among different age groups divided by decades. We demonstrated deeper BIS values with decades' age progression. Our data has important implications for propofol dosing. The practical information for physicians in their daily clinical practice is using propofol C_p of 3.5 μg mL^-1 might not yield BIS value of 50 in elderly patients. Our simulations showed that the recommended regimen of C_p 3.5 μg mL^-1 for 20-29 year should be gradually decreased to 2.0 μg mL^-1 for 80-89 year.

CLINICAL TRIAL REGISTRY NUMBERS

European Community Clinical Trials Database EudraCT (http://eudract.emea.eu) initial trial registration number: 2011-002847-81, and subsequently registered at www.clinicaltrials.gov; trial registration number: NCT02585284. Xijing Hospital of Fourth Military Medical University ethics committee approval number 20110707-4.

Performance of TCI Propofol Using the Schnider Model for Cardiac Surgery on Cardiopulmonary Bypass-A Pilot Study

OBJECTIVE

This pilot study aimed to evaluate the performance of target-controlled infusion (TCI) of propofol using the Schnider pharmacokinetic model in patients undergoing cardiac surgery requiring cardiopulmonary bypass.

DESIGN

This was a prospective pharmacokinetic study.

SETTING

A tertiary care hospital.

PARTICIPANTS

This study is comprised of 10 patients, aged between 46 and 81, who underwent elective cardiac surgery requiring the use of cardiopulmonary bypass.

INTERVENTIONS

Anesthetic technique was standardized. Hypnosis was maintained using TCI of propofol, titrated to achieve a bispectral index of 30 to 60. Calculated plasma propofol concentrations were recorded at 5 time points in total, before, during, and after cardiopulmonary bypass. Blood propofol concentration was measured at each of these time points.

MEASUREMENTS AND MAIN RESULTS

The prediction errors and absolute prediction errors were calculated for each sample. From these, the median prediction error (MDPE) and its absolute value (MDAPE) were derived. Agreement between predicted and measured propofol concentrations was assessed using a Bland-Altman plot. Mean prediction errors were also compared pre-, on, and post-bypass using the generalized linear latent and mixed model. The MDPE and MDAPE were both found to be 45%, indicating significant bias toward under-prediction in the Schnider pharmacokinetic model. This bias was increased at an average propofol concentration of 4.5 μg/mL and above. A significant decrease in mean prediction error was noted while on bypass (45.6%, 95% confidence intervals 9.2-82.1).

CONCLUSIONS

The performance of the Schnider pharmacokinetic model for TCI propofol was poor, with a tendency toward under-prediction of blood propofol concentration, especially at higher average concentrations of propofol. While mitigating the risk of awareness, the risk of other adverse effects like hypotension and cardiorespiratory depression is increased. Patients should therefore be adequately monitored, and predicted plasma propofol concentrations taken in context with other patient parameters. A lower target concentration of propofol is probably sufficient to maintain an adequate depth of anesthesia as measured by BIS.

Perioperative Care of Elderly Surgical Outpatients

The ambulatory setting offers potential advantages for elderly patients undergoing elective surgery due to the advancement in both surgical and anesthetic techniques resulting in quicker recovery times, fewer complications, higher patient satisfaction, and reduced costs of care. This review article aims to provide a practical guide to anesthetic management of elderly outpatients. Important considerations in the preoperative evaluation of elderly outpatients with co-existing diseases, as well as the advantages and disadvantages of different anesthetic techniques on a procedural-specific basis, and recommendations regarding the management of common postoperative complications (e.g., pain, postoperative nausea and vomiting [PONV], delirium and cognitive dysfunction, and gastrointestinal dysfunction) are discussed. The role of anesthesiologists as perioperative physicians is important for optimizing surgical outcomes for elderly patients undergoing ambulatory surgery. The implementation of high-quality, evidence-based perioperative care programs for the elderly on an ambulatory basis has assumed increased importance. Optimal management of perioperative pain using opioid-sparing multimodal analgesic techniques and preventing PONV using prophylactic antiemetics are key elements for achieving enhanced recovery after surgery.

Factors affecting recovery from anaesthesia with propofol-remifentanil target-controlled infusion in laparoscopic surgery

Objective

This study was performed to analyse factors influencing the effect-site concentration (Ce) of propofol at return of consciousness (ROC) with target-controlled infusion of propofol–remifentanil after laparoscopic surgery.

Methods

In total, 112 patients who underwent laparoscopic surgery under general anaesthesia were given propofol at the target concentration of 3.5 µg/ml. Remifentanil (Ce: 4.0 ng/ml) and 0.9 mg/kg of rocuronium were administered when the Observer’s Assessment of Alertness/Sedation score reached 1. Two minutes after injection of rocuronium, tracheal intubation was initiated. The bispectral index (BIS) was maintained between 45 and 55.

Results

Ce values of propofol at loss of consciousness (LOC) and ROC were significantly correlated. Age was significantly correlated with Ce of propofol at ROC. At LOC, propofol Ce values of patients aged 65–80, 45–64, and 20–44 years were 1.8 ± 0.8, 2.2 ± 0.7, and 2.3 ± 0.8 µg/ml, respectively, and the BIS was 70 ± 10, 68 ± 7, and 69 ± 10, respectively. At ROC, the propofol Ce values of the three groups were 1.2 ± 0.3, 1.4 ± 0.3, and 1.5 ± 0.3 µg/ml, respectively, and the BIS was 80 ± 5, 82 ± 6, and 83 ± 6, respectively.

Conclusions

The concentration of propofol at ROC was significantly affected by age, and ROC of propofol–remifentanil anaesthesia after laparoscopic surgery was well predicted by the concentration at LOC.

Impact of the Cytochrome P450 2B6 (CYP2B6) Gene Polymorphism c.516G>T (rs3745274) on Propofol Dose Variability

BACKGROUND AND OBJECTIVES

Propofol is the most commonly used hypnotic worldwide, but its effective dose varies greatly between individuals. The present study sought to investigate the relationship between the c.516G>T polymorphism in the CYP2B6 (cytochrome P450 2B6) gene and the required propofol dose.

METHODS

One hundred and eight patients treated with propofol were recruited, and environmental, clinical and surgical data were collected. Genotyping for the c.516G>T polymorphism was performed by real-time PCR. Multiple linear regression analysis was performed to estimate the predictive variables of the total propofol dose.

RESULTS

For patients under general anaesthesia, the predictive variables of the total propofol dose were surgery duration (partial R (2) = 19.9 %), age (partial R (2) = 10.5 %), weight (partial R (2) = 10.1 %) and presence of the T allele (partial R (2) = 6.8 %). From the estimated coefficient of regression values, the surgery duration and weight were the factors that increased the propofol dose, while age and presence of the T allele decreased the total dose of the drug needed. The total propofol doses based on the GG or GT/TT genotypes were 151.5 ± 64.2 mg and 129.3 ± 44.6 mg, respectively (p = 0.043).

CONCLUSIONS

Our results indicate that 34 % of the variance in the required propofol dose may be explained by these factors and that CYP2B6 c.516G>T polymorphism, which decreases the metabolism of the drug, accounts for approximately 7 % of the drug dosage. Our results show the possible influence of CYP2B6 c.516G>T genetic variant on propofol dose in patients under general anaesthesia.

Comparison of TIVA and Desflurane Added to a Subanaesthetic Dose of Propofol in Patients Undergoing Coronary Artery Bypass Surgery: Evaluation of Haemodynamic and Stress Hormone Changes

Introduction. Increased levels of stress hormones are associated with mortality in patients undergoing coronary artery bypass grafting (CABG). Aim. To compare total intravenous anaesthesia (TIVA) and desflurane added to a subanaesthetic dose of propofol. Material and Methods. Fifty patients were enrolled in this study. Fentanyl (3-5 mcg/kg/h) was started in both groups. Patients were divided into two groups. The PD group (n = 25) received 1 minimum alveolar concentration (MAC) desflurane anaesthesia in addition to propofol infusion (2-3 mg/kg/h), while P group (n = 25) received propofol infusion (5-6 mg/kg/h) only. Biochemical data, cortisol, and insulin levels were measured preoperatively (T0), after initiation of CPB but before cross-clamping the aorta (T1), after removal of the cross-clamp (T2), and at the 24th postoperative hour (T3). Results. Systolic, diastolic, and mean arterial pressure levels were significantly higher in PD group than those in P group in T1 and T2 measurements (p ≤ 0.05). CK-MB showed a significant decrease in group P (p ≤ 0.05). When we compared both groups, cortisol levels were significantly higher in PD group than P group (p ≤ 0.05). Conclusion. Stress and haemodynamic responses were better controlled using TIVA than desflurane inhalation added to a subanaesthetic dose of propofol in patients undergoing CABG.

Perioperative management of a patient undergoing a novel mini-invasive percutaneous transcatheter left ventricular reconstruction procedure

Survivors of myocardial infarction might have residual damage and higher risks of developing heart failure. This increasing complication encompasses up to 45% of all infarcts. As anesthesiologists we will have to perform anesthesia more frequently in patients with such challenging medical history schedule to undergo mini-invasive surgical procedures. We present the case of a 51-year-old man with severe heart failure post-myocardial infarction with multiple sclerosis undergoing a novel percutaneous transcatheter ventricular reconstruction via a left mini-thoracotomy. To guide the surgeon during the intervention we used a real-time 3D echocardiography, enlightening the fact that guidance is crucial for that kind of procedure. To lower postoperative pain and the inflammatory response we have administered successfully intravenous lidocaine, indicating that it is possible to avoid regional anesthesia in patients with multiple sclerosis scheduled for mini-invasive left ventricular reconstruction requiring a mini-thoracotomy.

Comparison of the Effect of Anesthesia With Midazolam-Fentanyl Versus Propofol-Remifentanil on Bispectral Index in Patients Undergoing Coronary Artery Bypass Graft

The aim of this study was to compare the effect of anesthesia with midazolam-fentanyl versus propofol-remifentanil on the BIS (bispectral index) in patients undergoing coronary artery bypass grafting (CABG). Sixty-four patients undergoing CABG were randomly assigned to one of two study groups: midazolam-fentanyl (MF, N= 32) or propofol-remifentanil (PR, N= 32). The BIS was measured before induction of anesthesia, five minutes after induction of anesthesia, at skin incision, sternotomy, pericardiotomy, aorta cannulation, onset of cardiopulmonary bypass, during rewarming, five minutes after separation from cardiopulmonary bypass, at thorax closure, and at the end of the surgery. There were no significant differences between the two groups with regard to age and gender. The difference in mean BIS between the two groups was significant (P < 0.05) at all times, except before induction, five minutes after induction, at skin incision and on rewarming. Changes in the BIS were lower in the PR group than in the MF group. Both techniques can provide adequate anesthesia in patients undergoing CABG. However, the probability of awareness during anesthesia is lower with propofol-remifentanil than with midazolam-fentanyl.

Association of Robotic Totally Endoscopic Coronary Artery Bypass Graft Surgery Associated With a Preliminary Cardiac Enhanced Recovery After Surgery Program: A Retrospective Analysis

OBJECTIVES

The robotic totally endoscopic coronary artery bypass graft (TECAB) surgery reduces patients' recovery time. The present trial investigated the feasibility and safety of an initial enhanced recovery after surgery (ERAS) path for patients undergoing robotic beating-heart TECAB and compared it with both conventional surgery and traditional perioperative care. It was hypothesized that the preliminary ERAS pathway associated with a beating-heart TECAB procedure could have a synergistic effect on postoperative patient care.

DESIGN

Observational retrospective study.

SETTING

University hospital.

PARTICIPANTS

Patients scheduled for coronary artery bypass graft and undergoing robotic beating-heart TECAB (n = 38) were compared with those undergoing standard surgery and perioperative care (n = 33). The outcomes were the possibility of tracheal extubation at the end of the surgery and the incidence of postoperative complications.

MEASUREMENTS AND MAIN RESULTS

The main comorbidities were similar between the 2 groups. Extubation on the operating table in the TECAB group was possible in all cases without requiring prompt endotracheal tube reinsertion. The proportion of patients transfused was significantly lower in the TECAB group (p = 0.009). In addition, the duration of intensive care unit and hospital stay were reduced significantly by 24 hours and by 4 days, respectively, in the TECAB group compared with the standard group (p< 0.05).

CONCLUSIONS

The present results suggested that a program coupling a beating-heart TECAB with a preliminary ERAS path for patients requiring a single coronary revascularization is feasible and safe. This approach could reduce postoperative mechanical ventilation time, transfusion rate, and both intensive care unit and hospital stay.

Cardioprotective Effects of Remifentanil in a Sympathetic Hyperactivity Model in Rabbits

OBJECTIVE

In this study, the antiarrhythmic and anti-ischemic effects of a 6 μg kg(-1) min(-1) infusion dose of remifentanil are investigated in a central sympathetic hyperactivity model in rabbits.

METHODS

In this study, 18 New Zealand rabbits were used. The subjects were randomly divided into three groups (n=6) and received 10 μmol L(-1) glutamate intracerebroventricularly to provide the central sympathetic hyperactivity. In group 1, 10 μmol L(-1) glutamate was used; in group 2, 1 h before L-glutamate injection, 40 mg kg(-1) N (omega)-nitro-L-arginine methyl ester was intravenously (iv) administered; and in group 3, also 1 h before L-glutamate injection, 40 mg kg(-1) N (omega)-nitro-L-arginine methyl ester was iv administered. A 6 μg kg(-1) min(-1) dose of remifentanil infusion was administered 5 min before L-glutamate injection. Heart rate, systolic arterial pressure and mean arterial pressure were measured and recorded. Within 15 min of the intracerebroventricular L-glutamate injection, premature ventricular complexes, bigeminy ventricular arrhythmia, ventricular tachycardia, ST-segment shift and T-wave inversions were recorded.

RESULTS

When incidences of heart rate, rate pressure product, premature ventricular complexes and bigeminy ventricular arrhythmia were compared between groups, significant differences were not determined. Mean arterial pressure was more significantly increased in group 2 than in the other groups (p<0.05). Ventricular tachycardia, ST-segment shift and T-wave inversions were significantly lower in group 3 than in groups 1 and 2 (p<0.05).

CONCLUSION

Remifentanil (6 μg kg(-1) min(-1) for 5 min of infusion) prevented life-threatening ventricular tachycardia and electrocardiographic signs of myocardial ischemia in a model of arrhythmia resulting from the association of central sympathetic overactivity.

Effects of different doses of sufentanil and remifentanil combined with propofol in target-controlled infusion on stress reaction in elderly patients

The current study aimed to observe the effects of sufentanil and remifentanil combined with propofol in target-controlled infusion (TCI) on perioperative stress reaction in elderly patients. A total of 80 elderly patients requiring general anesthesia were recruited. They were divided into four groups (each n=20) according to different target concentrations of remifentanil and sufentanil. These target concentrations were: 4 ng/ml remifentanil + 0.2 ng/ml sufentanil for group I; 3 ng/ml remifentanil + 0.3 ng/ml sufentanil for group II; 2 ng/ml remifentanil + 0.5 ng/ml sufentanil for anesthesia induction and post-intubation 3 ng/ml remifentanil + 0.2 ng/ml sufentanil for anesthesia maintenance for group III; and 5 ng/ml remifentanil for anesthesia induction and post-intubation 4 ng/ml remifentanil for anesthesia maintenance for group IV. Norepinephrine (NE), epinephrine (E) and angiotensin II (Ang II) levels in plasma were measured prior to the induction of anesthesia, as well as at several different time-points following surgery. The numbers of intraoperative severe hemodynamic fluctuation, postoperative eye-opening and extubation time, and post-extubation restlessness and pain scores were recorded. Group IV had a larger circulation fluctuation control number and higher levels of NE, E and Ang II at 3 h after surgery than any other group (P<0.01). Although group IV had shorter postoperative eye-opening and extubation times compared with the other groups (P<0.05), it also had higher restlessness and pain scores (P<0.01). The combined use of sufentanil and remifentanil stabilizes perioperative hemodynamics and reduces stress hormone levels.

Hemodynamic profile of target-controlled spinal anesthesia compared with 2 target-controlled general anesthesia techniques in elderly patients with cardiac comorbidities

BACKGROUND AND OBJECTIVES

The impact of anesthesia techniques in patients experiencing hip fracture is controversial. This study compares the effects on blood pressure of 3 anesthesia techniques that are considered safe for the elderly.

METHODS

Forty-five patients older than 75 years, with American Society of Anesthesiologists physical status III or IV, with cardiac comorbidities, and undergoing surgery for hip fracture, were randomized to receive continuous spinal anesthesia (CSA), propofol target-controlled infusion (TCI), or sevoflurane (SEVO). In CSA patients, a T10 metameric level target was achieved by titration of 2.5 mg of bupivacaine boluses. In patients on TCI and SEVO, a bispectral value target of around 50 guided the concentration of propofol or sevoflurane. Analgesia in the TCI and SEVO groups was provided with remifentanil. Hypotension was defined as a 30% decrease in mean arterial pressure and was treated with an intravenous bolus of ephedrine.

RESULTS

The number of hypotension episodes was lower in the CSA group: 0 (range, 0-6) versus 11.5 (range, 1-25) in the TCI group and 10 (range, 1-23) in the SEVO group (P < 0.001). Both TCI and SEVO patients needed more ephedrine compared with CSA patients (30.5 [15.5], 26 [23], and 1.5 [2.5] mg, respectively, P < 0.001). The maximal decrease in mean arterial pressure was lower in the CSA group (26% [17%]) compared with that in the TCI group (47% [8%]) and the SEVO group (46% [12%]; P < 0.001).

CONCLUSIONS

In elderly patients, spinal anesthesia using titrated doses of bupivacaine provided better blood pressure stability than propofol or sevoflurane anesthesia.

A comparison of three different target-controlled remifentanil infusion rates during target-controlled propofol infusion for oocyte retrieval

OBJECTIVE

To evaluate the effects of three different target-controlled remifentanil infusion rates during target-controlled propofol infusion on hemodynamic parameters, pain, sedation, and recovery score during oocyte retrieval.

METHODS

Sixty-nine women were scheduled for oocyte retrieval. Target-controlled propofol infusion at an effect-site concentration of 1.5 μg/mL was instituted. The patients were randomly allocated to receive remifentanil at an effect-site concentration of either 1.5 (group I, n = 23), 2 (group II, n = 23) or 2.5 ng/mL (group III, n = 23). Hemodynamic variables, sedation, pain, the Aldrete recovery score, and side effects were recorded.

RESULTS

Hemodynamic variables, sedation and pain scores and the number of patients with the maximum Aldrete recovery score 10 min after the procedure were comparable among the groups. The number of patients in group III with the maximum Aldrete recovery score 5 min after the procedure was significantly lower than that in groups I and II. One patient in group II and one patient in group III suffered from nausea.

CONCLUSION

Similar pain-free conscious sedation conditions without significant changes in hemodynamic parameters were provided by all three protocols. However, target controlled infusion of remifentanil at 1.5 or 2 ng/mL proved superior at providing early recovery compared to 2.5 ng/mL.

Influence of preoperative cognitive status on propofol requirement to maintain hypnosis in the elderly

BACKGROUND

The loss of cholinergic neurones in the basal forebrain has been shown to correlate to the extent of cognitive dysfunction during ageing in humans and to the hypnotic potency of propofol in animal models. We examined how the preoperative cognitive status, as assessed by mini-mental state examination (MMSE), may interact with propofol consumption during anaesthesia in the elderly.

METHODS

In a prospective study, we recruited 41 patients (65-99 yr) undergoing surgery for hip fracture. Femoral nerve block was performed for analgesia. Target-controlled infusion of propofol (Schnider's model) was adjusted to the bispectral index within the range 40-60. Multiple linear regression analysis determined whether age, BMI, gender, duration of anaesthesia, and preoperative MMSE score affected the propofol consumption (general linear model, Systat 8.0).

RESULTS

BMI and MMSE score significantly affected the mean value of propofol consumption. A low MMSE score (below 19) was associated with an observed decrease in propofol requirement in patients >65 yr of age. No significant effect of age, gender, and duration of anaesthesia on the propofol consumption was observed.

CONCLUSIONS

Propofol requirement to maintain hypnosis during general anaesthesia appears to decrease with deterioration in the cognitive status in the elderly. We suggest that a cognitive dysfunction linked to a cerebral cholinergic dysfunction may influence the brain sensitivity for propofol in aged patients.

Population pharmacokinetics of landiolol hydrochloride in healthy subjects

Landiolol hydrochloride is a newly developed cardioselective, ultra short-acting beta(1)-adrenergic receptor blocking agent used for perioperative arrhythmia control. The objective of this study was to characterize the population pharmacokinetics of landiolol hydrochloride in healthy male subjects. A total of 420 blood concentration data points collected from 47 healthy male subjects were used for the population pharmacokinetic analysis. NONMEM was used for population pharmacokinetic analysis. In addition, the final pharmacokinetic model was evaluated using a bootstrap method and a leave-one-out cross validation method. The concentration time course of landiolol hydrochloride was best described by a two-compartment model with lag time. The final parameters were total body clearance (CL: 36.6 mL/min/kg), distribution volume of the central compartment (V1: 101 mL/kg), inter-compartmental clearance (16.1 mL/min/kg), distribution volume of the peripheral compartment (55.6 mL/kg), and lag time (0.82 min). The inter-individual variability in the CL and V1 were 21.8% and 46.3%, respectively. The residual variability was 22.1%. Model evaluation by the two different methods indicated that the final model was robust and parameter estimates were reasonable. The population pharmacokinetic model for landiolol hydrochloride in healthy subjects was developed and was shown to be appropriate by both bootstrap and leave-one-out cross validation methods.

[Propofol administration systems. Handling, hemodynamics and propofol consumption]

BACKGROUND

During anaesthesia propofol is administered either by manual controlled infusion (MCI) or by target controlled infusion (TCI) techniques. In this study two different TCI systems for propofol administration were evaluated with regard to handling, patient safety, and costs and compared to administration of propofol by the MCI technique.

METHODS

In a prospective study, 90 patients scheduled for elective surgery of the nose or nasal sinuses were randomly enrolled in three groups. The two TCI systems were examined in two groups of 30 patients: one group received propofol following the pharmacokinetic TCI model of Schnider (TCI-Schnider) and the other group received propofol following the TCI model of Marsh (TCI-Marsh). A manual perfusion technique (MCI, n=30) was used in the control group. Depth of anesthesia was controlled using the bispectral index (BSI) which was adjusted to fall within the range of 40-55. Hemodynamics, extubation times and time of awaking, rate and quality of propofol dose adjustment, total drug requirements, costs, and quality of recovery were documented. The incidence of postoperative nausea and vomiting (PONV) as well as shivering and patient satisfaction were also documented.

RESULTS

Demographics, hemodynamics and perioperative data did not differ between the groups. Propofol consumption within the first 60 min also showed no significant differences. In the course of extended anaesthesia, propofol consumption was significantly less in both TCI groups compared to the control group (MCI) and the TCI-Schnider group also showed less episodes of bradycardia. The necessity of propofol dose adjustment did not differ significantly between the TCI groups. Administration and consumption of anaesthesia co-medication (fentanyl, remifentanil, cisatracurium) did not differ between the groups.

CONCLUSION

The investigated propofol administration procedures using the MCI or TCI techniques were safe and easy to handle under BIS monitoring. No differences were found concerning extubation times and time of awaking. During extended anaesthesia procedures (>60 min), propofol consumption was lower with both TCI techniques and thus costs could be saved.

BIS and Entropy in the elderly

The interaction of many poorly defined, physiological, pharmacological, and pathological factors make titration of general anaesthesia in the elderly difficult. There may be a potential clinical benefit using the processed electroencephalogram (EEG) to monitor hypnotic level in this population. We prospectively studied 16 patients aged over 65 years having hip fractures repaired under general anaesthesia by experienced anaesthetists blinded to Bispectral Index (BIS(XP)) and Entropy values. Pre-induction EEG indices did not correlate with age or mini-mental state examination (MMSE). During maintenance of anaesthesia, BIS(XP) and Response Entropy (RE) values were within the recommended range of 40-60, 45% and 32% of the total time, respectively. BIS(XP) and Response Entropy (RE) values were above 60 for 11% and 13% of the total time, respectively, and below 40 for 44% and 55% of the total time, respectively. BIS(XP) correlated well with RE in 12 patients, but in the other four patients there was a difference of more than 20 points between BIS(XP) and RE.

Impact of bispectral index monitoring on propofol administration in patients undergoing cardiopulmonary bypass

Propofol anaesthesia using target control infusion during cardiac surgery has become more popular recently. However, without depth of anaesthesia monitoring, the standard target concentration used may be higher than necessary to maintain adequate hypnosis during hypothermic cardiopulmonary bypass. The purpose of this study was to evaluate the effect of bispectral index monitoring on propofol administration during hypothermic cardiopulmonary bypass. After ethics committee approval and written informed consent, 20 New York Heart Association class I-III patients scheduled for elective cardiac surgery requiring hypothermic cardiopulmonary bypass were studied in this prospective randomised controlled trial. In group C, routine anaesthesia was practised, where patients received propofol at target concentration between 1.5 to 2.5 microg/ml during cardiopulmonary bypass. In group B, the target concentration was titrated to a bispectral index value of 40 to 50. Mean arterial pressure and bispectral index were recorded at various time intervals. The use of propofol, phenylephrine, sodium nitroprusside and adrenaline were recorded. The median propofol administration in group B was significantly less than that in group C (2.9 mg/kg/h compared to 6.0 mg/kg/h). The bispectral index value during bypass was significantly lower in group C than in group B, reflecting a deeper state of anaesthesia. There was no difference in the use of inotropes, vasoconstrictors or vasodilators. Bispectral index monitoring enables a 50% reduction in propofol administration at this standard dose during hypothermic cardiopulmonary bypass.

The coronary and myocardial effects of remifentanil and sufentanil in the erythrocyte-perfused isolated rabbit heart

Remifentanil-induced hypotension may be associated with adverse ischemic myocardial events. Although these events can be easily attributed to a decrease in coronary pressure perfusion, we tested the hypothesis that remifentanil could directly affect coronary vasomotor tone. Therefore, we assessed intrinsic coronary and myocardial in vitro effects of remifentanil on a Langendorff's rabbit model and compared these effects with those provoked by similar intracoronary concentrations of sufentanil. Under general anesthesia, hearts from New Zealand rabbits were rapidly excised and mounted on an erythrocyte-perfused and isolated heart preparation. The hearts were then exposed to increasing concentrations (10-1000 nM) of either remifentanil (n = 10) or sufentanil (n = 8). Between each concentration, hearts were allowed to return to baseline status. The maximal coronary and myocardial effects of each concentration of both drugs were noted. Baseline values of coronary blood flow and myocardial performances were comparable between groups. Neither remifentanil nor sufentanil induced significant coronary and myocardial effects. These results suggest that myocardial ischemia, which may occur during remifentanil-induced hemodynamic disturbances, especially in cardiac patients, is only related to a decrease in coronary perfusion pressure provoked by peripheral hemodynamic changes.

Comparison of the anaesthetic requirement with target-controlled infusion of propofol to insert the laryngeal tube vs. the laryngeal mask

BACKGROUND AND OBJECTIVE

The target effect-site concentration of propofol to insert a laryngeal mask airway was recently reported as almost 5 microg mL(-1). The present study aimed to determine the target effect-site concentration with target-controlled infusion of propofol to place classical larnygeal mask airway or current laryngeal tube in adult patients.

METHODS

We included 40 patients scheduled for short gynaecological and radiological procedures under general anaesthesia in a randomized, double-blind manner using the Dixon's up-and-down statistical method. Monitoring included standard cardiorespiratory monitors, and bispectral index monitoring was used for all patients. Anaesthesia was conducted with a target-controlled infusion system: Diprifusor. The initial target plasma concentration of propofol was 5 microg mL(-1), and was changed stepwise by 0.5 microg mL(-1) increments according to Dixon's up-and-down method. Criteria for acceptable insertion were: Muzi's score < or = 2, and mean arterial blood pressure, heart rate or bispectral index variation <20% the baseline values.

RESULTS

Target effect-site concentration of propofol required to insert laryngeal tube was 6.3 +/- 0.3 microg mL(-1) with Dixon method and ED50 was 6.1 microg mL(-1) (5.9-6.4) with logistic regression method. In the case of larnygeal mask airway they were 7.3 +/- 0.2 microg mL(-1) (Dixon method) and 7.3 microg mL(-1) (7.1-7.5; with logistic regression) respectively (P < 0.05). ED95 (logistic regression) was 6.8 microg mL(-1) (5.9-7.6) for laryngeal tube and 7.7 microg mL(-1) (7.3-8.0) for larnygeal mask airway (P < 0.05). Haemodynamic incidents were 55% in the larnygeal mask airway group vs. 30% in the laryngeal tube group (P < 0.05).

CONCLUSIONS

The target effect-site concentration of propofol for insertion of laryngeal tube was lower than for larnygeal mask airway (P < 0.05), with a consequent reduction of the propofol induced haemodynamic side-effects.

[Continuous infusion of remifentanil and target-controlled infusion of propofol for coronary surgery in elderly patients: comparison with continuous infusion of remifentanil and propofol]

OBJECTIVES

Comparison of the length of mechanical ventilation and postoperative complications after coronary surgery in elderly patients anaesthetised with propofol associated with either alfentanil or remifentanil.

STUDY DESIGN

Retrospective study with an historic control group.

PATIENTS

Three hundred thirty-eight consecutive patients (75-year-old or more) undergoing isolated coronary surgery. One hundred and fifty seven patients operated between January 1998 and June 2000 received alfentanil (1 microg/kg/minute) with a manually control infusion of propofol, 181 operated between July 2000 and 2002, remifentanil 0.25 microg/kg/minute with target controlled infusion of propofol (target blood concentration: 1.5 to 2 microg/ml).

METHODS

The two groups were compared for preoperative and surgical data. The length of mechanical ventilation, stay in ICU and the main postoperative complications were compared between the two groups.

RESULTS

Length of mechanical ventilation was significantly reduced in the remifentanil group (6 +/- 9 h vs. 13 +/- 63 h ; p <0.0001), 70% of the patients were extubated before the 6th postoperative hours against 53% in the alfentanil group (p =0.0023). This was not associated with a reduction of stay in ICU or postoperative complications. During surgery, an increased used of vasopressor was observed in the remifentanil group (40.2% vs 2.4% ; p <0.0001) with a postoperative elevation of blood concentration of CKMb (35.7 +/- 38.2 microg/l, vs. 27.7 +/- 31.9 microg/l, p =0.02).

CONCLUSION

Elderly patients undergoing coronary surgery were extubated earlier with remifentanil. However, this had no effect on duration of ICU stay but was associated with an increased used of vasopressor.