Anaesthetic efficacy and postinduction hypotension with remimazolam compared with propofol: a multicentre randomised controlled trial

Remimazolam, a short-acting benzodiazepine, may be used for induction and maintenance of total intravenous anaesthesia, but its role in the management of patients with multiple comorbidities remains unclear. In this phase 3 randomised controlled trial, we compared the anaesthetic efficacy and the incidence of postinduction hypotension during total intravenous anaesthesia with remimazolam vs. propofol. A total of 365 patients (ASA physical status 3 or 4) scheduled for elective surgery were assigned randomly to receive total intravenous anaesthesia with remimazolam (n = 270) or propofol (n = 95). Primary outcome was anaesthetic effect, quantified as the percentage of time with Narcotrend® Index values ≤ 60, during surgery (skin incision to last skin suture), with a non-inferiority margin of -10%. Secondary outcome was the incidence of postinduction hypotensive events. Mean (SD) percentage of time with Narcotrend Index values ≤ 60 during surgery across all patients receiving remimazolam (93% (20.7)) was non-inferior to propofol (99% (4.2)), mean difference (97.5%CI) -6.28% (-8.89-infinite); p = 0.003. Mean (SD) number of postinduction hypotension events was 62 (38.1) and 71 (41.1) for patients allocated to the remimazolam and propofol groups, respectively; p = 0.015. Noradrenaline administration events (requirement for a bolus and/or infusion) were also lower in patients allocated to remimazolam compared with propofol (14 (13.5) vs. 20 (14.6), respectively; p < 0.001). In conclusion, in patients who were ASA physical status 3 or 4, the anaesthetic effect of remimazolam was non-inferior to propofol.

What is the potential benefit of pre-hospital extracorporeal cardiopulmonary resuscitation for patients with an out-of-hospital cardiac arrest? A predictive modelling study

AIM

In this predictive modelling study we aimed to investigate how many patients with an out-of-hospital cardiac arrest (OHCA) would benefit from pre-hospital as opposed to in-hospital initiation of extracorporeal cardiopulmonary resuscitation (ECPR).

METHODS

A temporal spatial analysis of Utstein data was performed for all adult patients with a non-traumatic OHCA attended by three emergency medical services (EMS) covering the north of the Netherlands during a one-year period. Patients were considered potentially eligible for ECPR if they had a witnessed arrest with immediate bystander CPR, an initial shockable rhythm (or signs of life during resuscitation) and could be presented in an ECPR-centre within 45 minutes of the arrest. Endpoint of interest was defined as the hypothetical number of ECPR eligible patients after 10, 15 and 20 minutes of conventional CPR and upon (hypothetical) arrival in an ECPR-centre as a fraction of the total number of OHCA patients attended by EMS.

RESULTS

During the study period 622 OHCA patients were attended, of which 200 (32%) met ECPR eligibility criteria upon EMS arrival. The optimal transition point between conventional CPR and ECPR was found to be after 15 minutes. Hypothetical intra-arrest transport of all patients in whom no return of spontaneous circulation (ROSC) was obtained after that point (n=84) would have yielded 16/622 (2.5%) patients being potentially ECPR eligible upon hospital arrival (average low-flow time 52 minutes), whereas on-scene initiation of ECPR would have resulted in 84/622 (13.5%) potential candidates (average estimated low-flow time 24 minutes before cannulation).

CONCLUSION

Even in healthcare systems with relatively short transport distances to hospital, consideration should be given to pre-hospital initiation of ECPR for OHCA as it shortens low-flow time and increases the number of potentially eligible patients.

Comparison of haemodynamic- and electroencephalographic-monitored effects evoked by four combinations of effect-site concentrations of propofol and remifentanil, yielding a predicted tolerance to laryngoscopy of 90

This prospective study evaluates haemodynamic and electroencephalographic effects observed when administering four combinations of effect-site concentrations of propofol (Ce_PROP) and remifentanil (Ce_REMI), all yielding a single predicted probability of tolerance of laryngoscopy of 90% (P_TOL = 90%) according to the Bouillon interaction model. We aimed to identify combinations of Ce_PROP and Ce_REMI along a single isobole of P_TOL that result in favourable hypnotic and haemodynamic conditions. This knowledge could be of advantage in the development of drug advisory monitoring technology. 80 patients (18–90 years of age, ASA I–III) were randomized into four groups and titrated towards Ce_PROP (Schnider model, ug⋅ml⁻¹) and Ce_REMI (Minto model, ng⋅ml⁻¹) of respectively 8.6 and 1, 5.9 and 2, 3.6 and 4 and 2.0 and 8. After eleven minutes of equilibration, baseline measurements of haemodynamic endpoints and bispectral index were compared with three minutes of responsiveness measurements after laryngoscopy. Before laryngoscopy, bispectral index differed significantly (p < 0.0001) between groups in concordance with Ce_PROP. Heart rate decreased with increasing Ce_REMI (p = 0.001). The haemodynamic and arousal responses evoked by laryngoscopy were not significantly different between groups, but Ce_PROP = 3.6 μg⋅ml⁻¹ and Ce_REMI = 4 ng⋅ml⁻¹ evoked the lowest median value for ∆HR and ∆SAP after laryngoscopy. This study provides clinical insight on the haemodynamic and hypnotic consequences, when a model based predicted P_TOL is used as a target for combined effect-site controlled target- controlled infusion of propofol and remifentanil. Heart rate and bispectral index were significantly different between groups despite a theoretical equipotency for P_TOL, suggesting that each component of the anaesthetic state (immobility, analgesia, and hypnotic drug effect) should be considered as independent neurophysiological and pharmacological phenomena. However, claims of (in)accuracy of the predicted P_TOL must be considered preliminary because larger numbers of observations are required for that goal.

Influence of Bayesian optimization on the performance of propofol target-controlled infusion

Background

Target controlled infusion (TCI) systems use population-based pharmacokinetic (PK) models that do not take into account inter-individual residual variation. This study compares the bias and inaccuracy of a population-based vs a personalized TCI propofol titration using Bayesian adaptation. Haemodynamic and hypnotic stability, and the prediction probability of alternative PK models, was studied.

Methods

A double-blinded, prospective randomized controlled trial of 120 subjects undergoing cardiac surgery was conducted. Blood samples were obtained at 10, 35, 50, 65, 75 and 120 min and analysed using a point-of-care propofol blood analyser. Bayesian adaptation of the PK model was applied at 60 min in the intervention group. Median (Absolute) Performance Error (Md(A)PE) was used to evaluate the difference between bias and inaccuracy of the models. Haemodynamic (mean arterial pressure [MAP], heart rate) and hypnotic (bispectral index [BIS]) stability was studied. The predictive performance of four alternative propofol PK models was studied.

Results

MdPE and MdAPE did not differ between groups during the pre-adjustment period (control group: 6.3% and 16%; intervention group: 5.4% and 18%). MdPE differed in the post-adjustment period (12% vs. -0.3%), but MdAPE did not (18% vs. 15%). No difference in heart rate, MAP or BIS was found. Compared with the other models, the Eleveld propofol PK model (patients) showed the best prediction performance.

Conclusions

When an accurate population-based PK model was used for propofol TCI, Bayesian adaption of the model improved bias but not precision.

Clinical trial registration

Dutch Trial Registry NTR4518.

Pharmacokinetics and pharmacodynamics of propofol: changes in patients with frontal brain tumours

Background

Models of propofol pharmacokinetics and pharmacodynamics developed in patients without brain pathology are widely used for target-controlled infusion (TCI) during brain tumour excision operations. The goal of this study was to determine if the presence of a frontal brain tumour influences propofol pharmacokinetics and pharmacodynamics and existing PK-PD model performance.

Methods

Twenty patients with a frontal brain tumour and 20 control patients received a propofol infusion to achieve an induction-emergence-induction anaesthetic sequence. Propofol plasma concentration was measured every 4 min and at each transition of the conscious state. Bispectral index (BIS) values were continuously recorded. We used non-linear mixed-effects modelling to analyse the effects of the presence of a brain tumour on the pharmacokinetics and pharmacodynamics of propofol. Subsequently we calculated the predictive performance of Marsh, Schnider, and Eleveld models in terms of median prediction error (MdPE) and median absolute prediction error (MdAPE).

Results

Patients with brain tumours showed 40% higher propofol clearance than control patients. Performance of the Schnider model (MdPEpk -20.0%, MdAPEpk 23.4%) and Eleveld volunteer model (MdPEpk -8.58%, MdAPEpk 21.6%) were good. The Marsh model performed less well (MdPEpk -14.3%, MdAPEpk 41.4%), as did the Eleveld patient model (MdPEpk -30.8%, MdAPEpk 32.1%).

Conclusions

Brain tumours might alter the pharmacokinetics of propofol. Caution should be exerted when using propofol TCI in patients with frontal brain tumours due to higher clearance.

Trial registry number

NCT01060631.

Predictive performance of eleven pharmacokinetic models for propofol infusion in children for long-duration anaesthesia

Background

Predictive performance of eleven published propofol pharmacokinetic models was evaluated for long-duration propofol infusion in children.

Methods

Twenty-one aged three-11 yr ASA I-II patients were included. Anaesthesia was induced with propofol or sevoflurane, and maintained with propofol, remifentanil, and fentanyl. Propofol was continuously infused at rates of 4-14 mg kg  - 1 h - 1 after an initial bolus of 1.5-2.0 mg kg  - 1 . Venous blood samples were obtained every 30-60 min for five h and then every 60-120 min after five h from the start of propofol administration, and immediately after the end of propofol administration. Model performance was assessed with prediction error (PE) derivatives including divergence PE, median PE (MDPE), and median absolute PE (MDAPE) as time-related PE shift, measures for bias, and inaccuracy, respectively.

Results

We collected 85 samples over 270 (130) (88-545), mean (SD) (range), min. The Short model for children, and the Schüttler general-purpose model had acceptable performance (-20%≤MDPE ≤ 20%, MDAPE ≤ 30%, -4% h - 1  ≤   divergence PE ≤ 4% h - 1 ). The Short model showed the best performance with the maximum predictive performance metric. Two models developed only using bolus dosing (Shangguan and Saint-Maurice models) and the Paedfusor of the remaining nine models had significant negative divergence PE (≤-6.1% h - 1 ).

Conclusions

The Short model performed well during continuous infusion up to 545 min. This model might be preferable for target-controlled infusion for long-duration anaesthesia in children.

Dexmedetomidine pharmacodynamics in healthy volunteers: 2. Haemodynamic profile

Background

Dexmedetomidine, a selective α 2 -adrenoreceptor agonist, has unique characteristics, with little respiratory depression and rousability during sedations. We characterized the haemodynamic properties of dexmedetomidine by developing a pharmacokinetic-pharmacodynamic (PKPD) model with a focus on changes in mean arterial blood pressure (MAP) and heart rate.

Methods

Dexmedetomidine was delivered i.v. to 18 healthy volunteers in a step-up fashion by target-controlled infusion using the Dyck model. Exploratory PKPD modelling and covariate analysis were conducted in NONMEM.

Results

Our model adequately describes dexmedetomidine-induced hypotension, hypertension, and bradycardia, with a greater effective concentration for the hypertensive effect. Changes in MAP were best described by a double-sigmoidal E max model with hysteresis. Covariate analysis revealed no significant covariates apart from age on the baseline MAP in the population pharmacokinetic model used to develop this PKPD model. Simulations revealed good general agreement with published descriptive studies of haemodynamics after dexmedetomedine infusion.

Conclusions

The present integrated PKPD model should allow tighter control over the desired level of sedation, while limiting potential haemodynamic side-effects.

Clinical trial registration

NCT01879865.

Propofol-based anaesthesia versus sevoflurane-based anaesthesia for living donor kidney transplantation: results of the VAPOR-1 randomized controlled trial

Background

Kidney transplantation is associated with harmful processes affecting the viability of the graft. One of these processes is associated with the phenomenon of ischaemia-reperfusion injury. Anaesthetic conditioning is a widely described strategy to attenuate ischaemia-reperfusion injury. We therefore conducted the Volatile Anaesthetic Protection of Renal Transplants-1 trial, a pilot project evaluating the influence of two anaesthetic regimens, propofol- vs sevoflurane-based anaesthesia, on biochemical and clinical outcomes in living donor kidney transplantation.

Methods

Sixty couples were randomly assigned to the following three groups: PROP (donor and recipient propofol), SEVO (donor and recipient sevoflurane), and PROSE (donor propofol and recipient sevoflurane). The primary outcome was renal injury reflected by urinary biomarkers. The follow-up period was 2 yr.

Results

Three couples were excluded, leaving 57 couples for analysis. Concentrations of kidney injury molecule-1 (KIM-1), N -acetyl-β- d -glucosaminidase (NAG), and heart-type fatty acid binding protein (H-FABP) in the first urine upon reperfusion showed no differences. On day 2, KIM-1 concentrations were higher in SEVO [952.8 (interquartile range 311.8-1893.0) pg mmol -1 ] compared with PROP [301.2 (202.0-504.7) pg mmol -1 ]. This was the same for NAG: SEVO, 1.835 (1.162-2.457) IU mmol -1 vs PROP, 1.078 (0.819-1.713) IU mmol -1 . Concentrations of H-FABP showed no differences. Measured glomerular filtration rate at 3, 6, and 12 months showed no difference. After 2 yr, there was a difference in the acute rejection rate ( P =0.039). Post hoc testing revealed a difference between PROP (35%) and PROSE (5%; P =0.020). The difference between PROP and SEVO (11%) was not significant ( P =0.110).

Conclusions

The SEVO group showed higher urinary KIM-1 and NAG concentrations in living donor kidney transplantation on the second day after transplantation. This was not reflected in inferior graft outcome.

Clinical trial registration

NCT01248871.

Pharmacokinetic and pharmacodynamic interactions in anaesthesia. A review of current knowledge and how it can be used to optimize anaesthetic drug administration

This review describes the basics of pharmacokinetic and pharmacodynamic drug interactions and methodological points of particular interest when designing drug interaction studies. It also provides an overview of the available literature concerning interactions, with emphasis on graphic representation of interactions using isoboles and response surface models. It gives examples on how to transform this knowledge into clinically and educationally applicable (bedside) tools.

A comparison of propofol-to-BIS post-operative intensive care sedation by means of target controlled infusion, Bayesian-based and predictive control methods: an observational, open-label pilot study

Purpose

We evaluated the feasibility and robustness of three methods for propofol-to-bispectral index (BIS) post-operative intensive care sedation, a manually-adapted target controlled infusion protocol (HUMAN), a computer-controlled predictive control strategy (EPSAC) and a computer-controlled Bayesian rule-based optimized control strategy (BAYES).

Methods

Thirty-six patients undergoing short lasting sedation following cardiac surgery were included to receive propofol to maintain a BIS between 40 and 60. Robustness of control for all groups was analysed using prediction error and spectrographic analysis.

Results

Although similar time courses of measured BIS were obtained in all groups, a higher median propofol effect-site concentration (CePROP) was required in the HUMAN group compared to the BAYES and EPSAC groups. The time course analysis of the remifentanil effect-site concentration (CeREMI) revealed a significant increase in CeREMI in the EPSAC group compared to BAYES and HUMAN during the case. Although similar bias and divergence in control was found in all groups, larger control inaccuracy was observed in HUMAN versus EPSAC and BAYES. Spectrographic analysis of the system behavior shows that BAYES covers the largest spectrum of frequencies, followed by EPSAC and HUMAN.

Conclusions

Both computer-based control systems are feasible to be used during ICU sedation with overall tighter control than HUMAN and even with lower required CePROP. EPSAC control required higher CeREMI than BAYES or HUMAN to maintain stable control.

Clinical trial number: NCT00735631.

Electronic supplementary material

The online version of this article (10.1007/s10877-018-0208-2) contains supplementary material, which is available to authorized users.

Phenylephrine increases cardiac output by raising cardiac preload in patients with anesthesia induced hypotension

Induction of general anesthesia frequently induces arterial hypotension, which is often treated with a vasopressor, such as phenylephrine. As a pure α-agonist, phenylephrine is conventionally considered to solely induce arterial vasoconstriction and thus increase cardiac afterload but not cardiac preload. In specific circumstances, however, phenylephrine may also contribute to an increase in venous return and thus cardiac output (CO). The aim of this study is to describe the initial time course of the effects of phenylephrine on various hemodynamic variables and to evaluate the ability of advanced hemodynamic monitoring to quantify these changes through different hemodynamic variables. In 24 patients, after induction of anesthesia, during the period before surgical stimulus, phenylephrine 2 µg kg^-1 was administered when the MAP dropped below 80% of the awake state baseline value for > 3 min. The mean arterial blood pressure (MAP), heart rate (HR), end-tidal CO₂ (EtCO₂), central venous pressure (CVP), stroke volume (SV), CO, pulse pressure variation (PPV), stroke volume variation (SVV) and systemic vascular resistance (SVR) were recorded continuously. The values at the moment before administration of phenylephrine and 5(T₅) and 10(T₁₀) min thereafter were compared. After phenylephrine, the mean(SD) MAP, SV, CO, CVP and EtCO₂ increased by 34(13) mmHg, 11(9) mL, 1.02(0.74) L min^-1, 3(2.6) mmHg and 4.0(1.6) mmHg at T₅ respectively, while both dynamic preload variables decreased: PPV dropped from 20% at baseline to 9% at T₅ and to 13% at T₁₀ and SVV from 19 to 11 and 14%, respectively. Initially, the increase in MAP was perfectly aligned with the increase in SVR, until 150 s after the initial increase in MAP, when both curves started to dissociate. The dissociation of the evolution of MAP and SVR, together with the changes in PPV, CVP, EtCO₂ and CO indicate that in patients with anesthesia-induced hypotension, phenylephrine increases the CO by virtue of an increase in cardiac preload.

Pharmacokinetic-pharmacodynamic model for propofol for broad application in anaesthesia and sedation

BACKGROUND

Pharmacokinetic (PK) and pharmacodynamic (PD) models are used in target-controlled-infusion (TCI) systems to determine the optimal drug administration to achieve a desired target concentration in a central or effect-site compartment. Our aim was to develop a PK-PD model for propofol that can predict the bispectral index (BIS) for a broad population, suitable for TCI applications.

METHODS

Propofol PK data were obtained from 30 previously published studies, five of which also contained BIS observations. A PK-PD model was developed using NONMEM. Weight, age, post-menstrual age (PMA), height, sex, BMI, and presence/absence of concomitant anaesthetic drugs were explored as covariates. The predictive performance was measured across young children, children, adults, elderly, and high-BMI individuals, and in simulated TCI applications.

RESULTS

Overall, 15 433 propofol concentration and 28 639 BIS observations from 1033 individuals (672 males and 361 females) were analysed. The age range was from 27 weeks PMA to 88 yr, and the weight range was 0.68-160 kg. The final model uses age, PMA, weight, height, sex, and presence/absence of concomitant anaesthetic drugs as covariates. A 35-yr-old, 170 cm, 70 kg male (without concomitant anaesthetic drugs) has a V₁, V₂, V₃, CL, Q₂, Q₃, and k_e0 of 6.28, 25.5, 273 litres, 1.79, 1.75, 1.11 litres min^-1, and 0.146 min^-1, respectively. The propofol TCI administration using the model matches well with recommendations for all age groups considered for both anaesthesia and sedation.

CONCLUSIONS

We developed a PK-PD model to predict the propofol concentrations and BIS for broad, diverse population. This should be useful for TCI in anaesthesia and sedation.

A randomized controlled trial of an Internet-based cognitive-behavioural intervention for non-specific chronic pain: an effectiveness and cost-effectiveness study

BACKGROUND

Cognitive-behavioural treatment can nowadays be delivered through the Internet. This form of treatment can have various advantages with regard to availability and accessibility. Previous studies showed that Internet-based treatment for chronic pain is effective compared to waiting-list control groups.

METHODS

We conducted a randomized controlled trial comparing an Internet-based cognitive-behavioural intervention with e-mail therapist contact to a face-to-face cognitive-behavioural group intervention. Of the 72 participants who were randomly assigned to an Internet or a group course, 50 participants completed the intervention. Participants were assessed at baseline (T0), immediately after the 7-week course (T1) and at the booster session 2 months later (T2). Pain-related catastrophizing was the primary outcome measure. Pain intensity, fatigue, pain-related interference, locus of control, pain coping, global health-related quality of life and medical expenses were secondary outcome variables.

RESULTS

Significant improvement was found on catastrophizing, pain coping, locus of control and aspects of global health-related quality of life in both the Internet and the group courses directly after the course and at the booster session. Pain intensity was improved in both courses at the booster session. At T2, improvement in catastrophizing, pain intensity, pain coping and some quality of life dimensions was significantly greater in completers of the Internet course than in the group course. Furthermore, the Internet course was cost-effective compared to the group course.

CONCLUSIONS

We conclude that the Internet-based cognitive-behavioural intervention was at least as effective as the face-to-face group intervention and, on some outcome measures appeared to be even more effective.

Cerebral haemodynamic physiology during steep Trendelenburg position and CO(2) pneumoperitoneum

BACKGROUND

The steep (40°) Trendelenburg position optimizes surgical exposure during robotic prostatectomy. The goal of the current study was to elucidate the influence of this patient positioning on cerebral blood flow and zero flow pressure (ZFP), and to assess the validity of different methods of evaluating ZFP.

METHODS

In 21 consecutive patients who underwent robotic endoscopic radical prostatectomy under general anaesthesia, transcranial Doppler flow velocity waveforms and invasive arterial and central venous pressure (CVP) waveforms suitable for analysis were recorded throughout the whole operative procedure in 14. The ZFP was determined by regression analysis of the pressure-flow plot and by different simplified formulas. The effective cerebral perfusion pressure (eCPP), pulsatility index (PI), and resistance index (RI) were determined.

RESULTS

While patients were in the Trendelenburg position, the ZFP increased in parallel with the CVP. The PI, RI, gradient between the ZFP and CVP, and the gradient between the CPP and the eCPP did not increase significantly (P<0.05) after 3 h of the steep Trendelenburg position. Using the formula described by Czosnyka and colleagues, the ZFP correlated closely with that calculated by linear regression throughout the course of the operation.

CONCLUSIONS

Prolonged steep Trendelenburg positioning and CO(2) pneumoperitoneum does not compromise cerebral perfusion. ZFP and eCPP are reliable variables for assessing brain perfusion during prolonged steep Trendelenburg positioning.

Pressure monitoring during neuroendoscopy: new insights

BACKGROUND

Significant increases in intracranial pressure (ICP) may occur during neuroendoscopic procedures. To detect and prevent serious and sustained increases, ICP should be monitored. At present, controversy exists on the optimal location of the monitoring sensor. Therefore, we conducted an in vitro study to estimate the pressure gradients between the ventricle, the 'gold standard' site, and the rinsing inlet and outlet.

METHODS

A head model and a standard endoscope were used. Rinsing was enforced by using a pressurized infusion bag. Using clinically relevant flow rates, pressure was measured at the rinsing inlet and outlet, in the ventricle, and at the distal end of the rinsing channel using a tip sensor or a capillary tube.

RESULTS

At a flow of 61 ml min(-1), the steady-state pressures measured at the rinsing inlet, in the ventricle, and at the rinsing outlet were 38, 26, and 12 mm Hg, respectively. At 135 ml min(-1), these increased to 136, 89, and 42 mm Hg. Transendoscopic pressure measurements were always within 1 mm Hg of the ventricular pressure.

CONCLUSIONS

During endoscopy, measurements at the rinsing inlet overestimated the ventricular pressure by ∼50 mm Hg during heavy rinsing, whereas measurements at the rinsing outlet underestimated the pressure by ∼50 mm Hg. An electronic tip sensor or a pressure capillary tube placed at the distal end of the lumen of the rinsing channel of the endoscope did not interfere with rinsing flow and produced measurements that were equal to ventricular pressures.

Optimizing intravenous drug administration by applying pharmacokinetic/pharmacodynamic concepts

This review discusses the ways in which anaesthetists can optimize anaesthetic-analgesic drug administration by utilizing pharmacokinetic and pharmacodynamic information. We therefore focus on the dose-response relationship and the interactions between i.v. hypnotics and opioids. For i.v. hypnotics and opioids, models that accurately predict the time course of drug disposition and effect can be applied. Various commercial or experimental drug effect measures have been developed and can be implemented to further fine-tune individual patient-drug titration. The development of advisory and closed-loop feedback systems, which combine and integrate all sources of pharmacological and effect monitoring, has taken the existing kinetic-based administration technology forwards closer to total coverage of the dose-response relationship.

Influence of obesity on propofol pharmacokinetics: derivation of a pharmacokinetic model

BACKGROUND

The objective of this study was to develop a pharmacokinetic (PK) model to characterize the influence of obesity on propofol PK parameters.

METHODS

Nineteen obese ASA II patients undergoing bariatric surgery were studied. Patients received propofol 2 mg kg(-1) bolus dose followed by a 5-20-40-120 min, 10-8-6-5 mg kg(-1) h(-1) infusion. Arterial blood samples were withdrawn at 1, 3, 5 min after induction, every 10-20 min during propofol infusion, and every 10-30 min for 2 h after stopping the propofol infusion. Arterial samples were processed by high-performance liquid chromatography. Time-concentration data profiles from this study were pooled with data from two other propofol PK studies available at http://www.opentci.org. Population PK modelling was performed using non-linear mixed effects model.

RESULTS

The study involved 19 obese adults who contributed 163 observations. The pooled analysis involved 51 patients (weight 93 sd 24 kg, range 44-160 kg; age 46 sd 16 yr, range 25-81 yr; BMI 33 sd 9 kg m(-2), range 16-52 kg m(-2)). A three-compartment model was used to investigate propofol PK. An allometric size model using total body weight (TBW) was superior to all other models investigated (linear TBW, free fat mass, lean body weight, normal fat mass) for all clearance parameters. Variability in V2 and Q2 was reduced by a function showing a decrease in both parameters with age.

CONCLUSIONS

We have derived a population PK model using obese and non-obese data to characterize propofol PK over a wide range of body weights. An allometric model using TBW as the size descriptor of volumes and clearances was superior to other size descriptors to characterize propofol PK in obese patients.

Muscle potentials evoked by magnetic stimulation of the sciatic nerve in unilateral sciatic nerve dysfunction

Magnetic stimulation of the sciatic nerve and subsequent recording of the muscle-evoked potential (MEP) was performed in eight dogs and three cats with unilateral sciatic nerve dysfunction. Localisation of the lesion in the sciatic nerve was based on the history, clinical neurological examination and on results of electromyography examination. Aetiology of the sciatic nerve lesion was diverse. A significant difference was found in MEP between the normal and the affected limbs. In addition, absence of conscious pain sensation, absence of voluntary motor function and a poor outcome seemed associated with the inability to evoke an MEP in the affected limb.

Influence of steep Trendelenburg position and CO(2) pneumoperitoneum on cardiovascular, cerebrovascular, and respiratory homeostasis during robotic prostatectomy

BACKGROUND

The steep (40 degrees ) Trendelenburg position optimizes surgical exposure during robotic prostatectomy. The goal of the current study was to investigate the combined effect of this position and CO(2) pneumoperitoneum on cardiovascular, cerebrovascular, and respiratory homeostasis during these procedures.

METHODS

Physiological data were recorded during the whole surgical procedure in 31 consecutive patients who underwent robotic endoscopic radical prostatectomy under general anaesthesia. Heart rate, mean arterial pressure, central venous pressure, Sp(o(2)), Pe'(co(2)), P(Plat), tidal volume, compliance, and minute ventilation were monitored and recorded. Arterial samples were obtained to determine the arterial-to-end-tidal CO(2) tension gradient. Continuous regional cerebral tissue oxygen saturation (Sct(o(2))) was determined by near-infrared spectroscopy.

RESULTS

Although patients were in the Trendelenburg position, all variables investigated remained within a clinically acceptable range. Cerebral perfusion pressure (CPP) decreased from 77 mm Hg at baseline to 71 mm Hg (P=0.07), and Sct(o(2)) increased from 70% to 73% (P<0.001). Pe'(co(2)) increased from 4.12 to 4.79 kPa (P<0.001) and the arterial-to-Pe'(co(2)) tension difference increased from 1.06 kPa in the normal position to a maximum of 1.41 kPa (P<0.001) after 2 h in the Trendelenburg position.

CONCLUSIONS

The combination of the prolonged steep Trendelenburg position and CO(2) pneumoperitoneum was well tolerated. Haemodynamic and pulmonary variables remained within safe limits. Regional cerebral oxygenation was well preserved and CPP remained within the limits between which cerebral blood flow is usually considered to be maintained by cerebral autoregulation.

Pharmacokinetic models for propofol--defining and illuminating the devil in the detail

The recently introduced open-target-controlled infusion (TCI) systems can be programmed with any pharmacokinetic model, and allow either plasma- or effect-site targeting. With effect-site targeting the goal is to achieve a user-defined target effect-site concentration as rapidly as possible, by manipulating the plasma concentration around the target. Currently systems are pre-programmed with the Marsh and Schnider pharmacokinetic models for propofol. The former is an adapted version of the Gepts model, in which the rate constants are fixed, whereas compartment volumes and clearances are weight proportional. The Schnider model was developed during combined pharmacokinetic-pharmacodynamic modelling studies. It has fixed values for V1, V3, k(13), and k(31), adjusts V2, k(12), and k(21) for age, and adjusts k(10) according to total weight, lean body mass (LBM), and height. In plasma targeting mode, the small, fixed V1 results in very small initial doses on starting the system or on increasing the target concentration in comparison with the Marsh model. The Schnider model should thus always be used in effect-site targeting mode, in which larger initial doses are administered, albeit still smaller than for the Marsh model. Users of the Schnider model should be aware that in the morbidly obese the LBM equation can generate paradoxical values resulting in excessive increases in maintenance infusion rates. Finally, the two currently available open TCI systems implement different methods of effect-site targeting for the Schnider model, and in a small subset of patients the induction doses generated by the two methods can differ significantly.

Influence of an increased intracranial pressure on cerebral and systemic haemodynamics during endoscopic neurosurgery: an animal model

BACKGROUND

During endoscopic neurosurgery, direct mechanical stimulation of the brain by the endoscope and increased intracranial pressure (ICP) caused by the continuous rinsing can induce potentially lethal haemodynamic reflexes, brain ischaemia, and excessive fluid resorption.

METHODS

In a newly presented rat model of endoscopic neurosurgery, stereotactic access to the cerebrospinal fluid was secured and the ICP was increased by controlled infusion until complete suppression of the cerebral perfusion pressure (CPP). The haematocrit (Hct) level was determined before and after the procedure. During the whole procedure, invasive arterial pressure, ICP, and heart rate were continuously recorded and evaluated in a subsequent offline analysis. After the procedure, the animals were allowed to recover and 7 days later they were killed for histological examination.

RESULTS

Suppression of the CPP resulted in a severe hypertension combined with tachycardia or mild bradycardia. The Hct decreased from 41 to 35 over the minutes of CPP suppression. After cessation of the infusion, the ICP decreased to 37% of the plateau pressure within 2.5 s. In the first few minutes after restoration of normal ICP, five animals died because of pulmonary oedema.

CONCLUSIONS

Upon complete suppression of the CPP, an obvious hypertension developed, often together with tachycardia, but no severe bradycardia. At high ICP levels, we observed an important translocation of irrigation fluid to the vascular space. Fatality was not caused by ischaemia or arrhythmia but due to pulmonary oedema.

Comparison of contemporary EEG derived depth of anesthesia monitors with a 5 step validation process

During the last decennium, a growing number of depth of anesthesia monitors, extracting information from the spontaneous electroencephalogram (EEG) have been developed and commercialized. The growing interest in depth of anesthesia monitoring resulted in an intensified technological progress. Innovations on both hardware and mathematical algorithms were introduced for improving the extraction of data. Because of the abundance of monitors now commercially available, it becomes increasingly important to develop a standardized reproducible methodology for comparing depth of anesthesia monitors. In this review, the authors present a strategy to compare monitors of the hypnotic component of anesthesia, based on the available literature and their own experience with validation studies. They also discuss the level of validation of the most commonly used EEG derived depth of anesthesia monitors.

Changes in a surgical stress index in response to standardized pain stimuli during propofol–remifentanil infusion

BACKGROUND

The surgical stress index (SSI) is based on a sum of the normalized pulse beat interval (PBI) and the pulse wave amplitude (PPGA) time series of the photoplethysmography. As a measure of the nociception-anti-nociception balance in response to a standardized pain stimulus, SSI was compared with EEG changes in state and response entropy (SE and RE), PPGA, and heart rate (HR) during various targeted pseudo-steady-state concentrations of propofol and remifentanil.

METHODS

Forty ASA I patients were allocated to one of the four groups to receive a remifentanil step-up/-down effect-compartment target-controlled infusion (Ce(remi)) of 0, 2, 6, 2, 0 ng ml(-1), or 6, 2, 0, 2, 6 ng ml(-1), and an effect-compartment target-controlled propofol infusion (Ce(prop)) to keep the SE between 30 and 50 or 15 and 30, respectively. At each steady-state Ce(remi), maximum change in SSI, SE, RE, PPGA, and HR after a noxious stimulus was compared with the baseline value. A correlation and prediction probability (P(K)) with Ce(prop) and Ce(remi) was measured.

RESULTS

Static and dynamic values of SSI correlated to Ce(remi) better than SE, RE, HR, and PPGA. SSI was independent of Ce(prop), in contrast to SE and RE. The P(K) for Ce(remi) both before and during a noxious stimulus was better with SSI.

CONCLUSIONS

SSI appeared to be a better measure of nociception-anti-nociception balance than SE, RE, HR, or PPGA.

Influence of intraoperative opioid on postoperative pain and pulmonary function after laparoscopic gastric banding: remifentanil TCI vs sufentanil TCI in morbid obesity

BACKGROUND

Choice of opioid may influence postoperative pain, recovery, and respiratory homeostasis in morbid obesity. The aim of this study was to compare the effects of target-controlled infusions (TCIs) of remifentanil or sufentanil on postoperative analgesia, recovery, and pulmonary function after laparoscopic gastric banding.

METHODS

Forty morbidly obese patients undergoing laparoscopic gastric banding received BIS-guided desflurane anaesthesia combined with remifentanil TCI (Group R) or sufentanil TCI (Group S). Intraoperative haemodynamic stability, BIS controllability, and immediate recovery in the operating room were measured. Pulmonary function, modified Aldrete score, modified Observers Assessment of Alertness and Sedation score, blood gas analysis, and visual analogue score for pain and postoperative nausea and vomiting were measured on admission to the post-anaesthesia care unit and 30, 60, 120 min afterwards. After operation, patients received patient-controlled analgesia with morphine.

RESULTS

During the first two postoperative hours, cumulative morphine consumption was higher in the remifentanil group compared with the sufentanil group, but was equal values after that time. Recovery profiles and spirometry showed no significant differences. During maintenance, remifentanil gave a better haemodynamic stability.

CONCLUSIONS

As few differences occurred in the postoperative period, the theoretical advantage of remifentanil over the longer acting sufentanil can be questioned when using TCI technology.

Feasibility study for the administration of remifentanil based on the difference between response entropy and state entropy †

BACKGROUND

Facial electromyography (FEMG) may have utility in the assessment of nociception during surgery. The difference between state entropy (SE) and response entropy (RE) is an indirect measure of FEMG. This study assesses an automated algorithm for remifentanil administration that is based on maintaining an entropy difference (ED) that is less than an upper boundary condition and greater than a lower boundary condition.

METHODS

The algorithm was constructed with a development set (n = 40), and then automated and studied with a validation set (n = 20) of patients undergoing anterior cruciate ligament repair. The percentage of time that the ED was maintained between the two boundary conditions was determined. Remifentanil and propofol predicted effect-site concentrations (Ce) were determined at surgical milestones and, after drug discontinuation, the time to response to verbal stimulation and orientation was measured.

RESULTS

The median (25th-75th percentile) per cent of time that the ED was recorded between the boundary conditions was 99.3% (98.1-99.8%). Predicted propofol (microg ml(-1)) and remifentanil (ng ml(-1)) Ce (sd), respectively, were 3.5 and 4.0 at induction, 1.9 (0.8) and 7.2 (3.7) at the end of surgery, and 1.1 (0.5) and 3.2 (2.2) at eye opening. The median time to eye opening and orientation was 3.8 and 6.8 min, respectively.

CONCLUSION

This feasibility study supports the concept that remifentanil may be delivered using an algorithm that maintains the difference between SE and RE between the upper and lower boundary condition.

Do we need inhaled anaesthetics to blunt arousal, haemodynamic responses to intubation after i.v. induction with propofol, remifentanil, rocuronium?

BACKGROUND

The aim of this study was to determine whether, after propofol, rocuronium and remifentanil rapid sequence induction, inhaled anaesthetic agents should be started before intubation to minimize autonomic and arousal response during intubation.

METHODS

One hundred ASA I and II patients were randomized to receive 1 MAC of desflurane or sevoflurane during manual ventilation or not. Anaesthesia was induced with an effect-site-controlled infusion of remifentanil at 2 ng ml(-1) for 3 min. Patients then received propofol to induce loss of consciousness (LOC). Rocuronium (0.6 mg kg(-1)) was given at LOC and the trachea was intubated after 90 s of manual breathing support (=baseline) with or without inhaled anaesthetics. Vital signs and bispectral index (BIS) were recorded until 10 min post-intubation to detect autonomic and arousal response.

RESULTS

A significant increase in BIS value after intubation was seen in all groups. The increases were mild, even in those not receiving pre-intubation inhaled anaesthetics. However, in contrast to sevoflurane, desflurane appeared to partially blunt the arousal response. Heart rate, systolic and diastolic pressure increase similarly in all groups.

CONCLUSIONS

Desflurane and sevoflurane were unable to blunt the arousal reflex completely, as measured by BIS, although the reflex was significantly less when desflurane was used. Rapid sequence induction with remifentanil, propofol and rocuronium and without inhaled anaesthetics before intubation can be done without dangerous haemodynamic and arousal responses at intubation after 90 s.

Depth of anaesthesia monitoring: what's available, what's validated and what's next?

Depth of anaesthesia monitors might help to individualize anaesthesia by permitting accurate drug administration against the measured state of arousal of the patient. In addition, the avoidance of awareness or excessive anaesthetic depth might result in improved patient outcomes. Various depth of anaesthesia monitors based on processed analysis of the EEG or mid-latency auditory-evoked potentials are commercially available as surrogate measures of anaesthetic drug effect. However, not all of them are validated to the same extent.

The mechanisms of carbon monoxide production by inhalational agents

Carbon monoxide can be formed when volatile anaesthetic agents such as desflurane and sevoflurane are used with anaesthetic breathing systems containing carbon dioxide absorbents. This review describes the possible chemical processes involved and summarises the experimental and clinical evidence for the generation of carbon monoxide. We emphasise the different conditions that were used in the experimental work, and explain some of the features of the clinical reports. Finally, we provide guidelines for the prevention and detection of this complication.

Value of Cushing reflex as warning sign for brain ischaemia during neuroendoscopy † †This work was performed at the Department of Anaesthesia, Ghent University Hospital, Ghent, Belgium

BACKGROUND

During an endoscopic neurosurgical procedure a sudden increase in intracranial pressure may occur at any time. We present a prospective study of haemodynamic changes during such procedures.

METHODS

Physiological data were recorded during the whole operative procedure in 17 consecutive patients who underwent an endoscopic neurosurgical procedure under general anaesthesia. Monitoring included invasive blood pressure, intracranial pressure, electrocardiogram, end-expired carbon dioxide, pulse oximetry and heart rate. Pressure and ECG waveforms were recorded at 100 Hz and evaluated in a subsequent offline analysis.

RESULTS

In almost every case, the occurrence of hypertension and tachycardia was clearly the result of an increase in intracranial pressure. Also, a Cushing reflex developed in almost every case where the cerebral perfusion pressure dropped below 15 mm Hg. The occurrence of bradycardia was not systematically associated with a low cerebral perfusion pressure.

CONCLUSION

In this study, we describe the haemodynamic effects of increased intracranial pressure during endoscopic neurosurgical procedures and their respective sequence of events at high temporal resolution. Although most clinicians rely on the occurrence of bradycardia to diagnose intracranial hypertension during endoscopic neurosurgical procedures, we show that a simultaneous onset of hypertension and tachycardia is a better indicator of impaired brain perfusion. Waiting for a persistent bradycardia to alert the surgeon during endoscopic neurosurgical procedures could allow severe bradycardia or even asystole to develop.

Time course of inhaled anaesthetic drug delivery using a new multifunctional closed-circuit anaesthesia ventilator. In vitro comparison with a classical anaesthesia machine †

BACKGROUND

The aim of this study was to detail the time-course, defined as the changes in end-tidal drug concentration with time, and consumption of inhaled anaesthetics when using a multifunctional closed-circuit anaesthesia machine in various drug delivery modes, and to compare it with a classical anaesthesia machine using an out-of-circle vaporizer under high and low fresh gas flow conditions.

METHODS

Using an artificial test lung, sevoflurane and desflurane time-course and consumption were compared when using the Zeus apparatus (Dräger, Lubeck, Germany) with direct injection of inhaled anaesthetics or the Primus apparatus (Dräger, Lubeck, Germany) using a classical out-of-circle vaporizer. Anaesthetics were targeted at 1 and 2 MAC end-tidal during 15 min. For both apparatus, out-of-circle high and low fresh gas control (FGC) and for Zeus, auto-control (AC) modes (fixed fresh gas flow at 6 and 1 litre min(-1) and uptake mode) were compared. Time to reach target, initial overshoot and stability at target, and wash-out times were compared.

RESULTS

In FGC, an initial overshoot in end-tidal drug concentration is seen when using 6 litre min(-1) fresh gas flow and a slower time course is observed when using only 1 litre min(-1) in both apparatus. In auto-control mode, the time course of both sevoflurane and desflurane was very fast and not influenced by the changes in fresh gas flow. No overshoot at target was seen. At all settings, the wash-out times were faster when using Zeus than Primus. Inhaled anaesthetic consumption was lowest with the Zeus ventilator in uptake AC mode.

CONCLUSION

A combination of the fastest time course and lowest consumption of sevoflurane and desflurane was found when using the Zeus apparatus in AC uptake mode.

Spectral entropy measurement of patient responsiveness during propofol and remifentanil. A comparison with the bispectral index †

BACKGROUND

We compared two spectral entropies, state entropy (SE) and response entropy (RE), based on the irregularity of the EEG, to measure loss of response to verbal command (LOR(verbal)) and noxious stimulus (LOR(noxious)) with the bispectral index (BIS) during propofol infusion with and without remifentanil.

METHODS

Three groups of 20 patients received an effect-site controlled propofol infusion (Ce(PROP)) starting at 1 microg ml(-1) and increased in steps of 0.5 microg ml(-1) at 4 min intervals. In addition, a remifentanil infusion was maintained at a group-dependent, fixed effect-site target concentration (Ce(REMI)) (0, 2 or 4 ng ml(-1)). The ability of BIS, SE or RE to predict LOR(verbal) and LOR(noxious) were compared with the changes in BIS, SE and RE using logistic regression, prediction probability (P(K)), and sensitivity/specificity.

RESULTS

In all groups, BIS, SE and RE decreased with increasing Ce(PROP). However, BIS decreased more smoothly than SE and RE at deeper levels of sedation. At LOR(verbal), BIS(50), SE(50) and RE(50) increased with increasing Ce(REMI). BIS, SE and RE all detected LOR(verbal) accurately but BIS performed better at 100% sensitivity. Sensitivity/specificity for detection of LOR(verbal) decreased for all methods with increasing Ce(REMI). LOR(noxious) was poorly described by all measures.

CONCLUSION

LOR(verbal) was detected accurately by BIS, SE and RE except for 100% sensitivity, where BIS performed better. Though BIS, SE and RE were influenced by remifentanil during propofol administration, their ability to detect LOR(verbal) remained accurate. None of the measures predicted LOR(noxious).

Production of compound A and carbon monoxide in circle systems: an in vitro comparison of two carbon dioxide absorbents

Two new generation carbon dioxide absorbents, DrägerSorb Free and Amsorb Plus, were studied in vitro for formation of compound A or carbon monoxide, during minimal gas flow (500 ml x min(-1)) with sevoflurane or desflurane. Compound A was assessed by gas chromatography/mass spectrometry and carbon monoxide with continuous infrared spectrometry. Fresh and dehydrated absorbents were studied. Mean (SD) time till exhaustion (inspiratory carbon dioxide concentration >or= 1 kPa) with fresh absorbents was longer with DrägerSorb Free (1233 (55) min) than with Amsorb Plus (1025 (55) min; p < 0.01). For both absorbents, values of compound A were < 1 ppm and therefore below clinically significant levels, but were up to 0.25 ppm higher with DrägerSorb Free than with Amsorb Plus. Using dehydrated absorbents, values of compound A were about 50% lower than with fresh absorbents and were identical for DrägerSorb Free and Amsorb Plus. With dehydrated absorbents, no detectable carbon monoxide was found with desflurane.

Optimization of desflurane administration in morbidly obese patients: a comparison with sevoflurane using an ‘inhalation bolus’ technique

BACKGROUND

The concept of an 'inhalation bolus' can be used to optimize inhaled drug administration. We investigated the depth of anaesthesia, haemodynamic stability, and recovery time in morbidly obese patients resulting from bispectral index (BIS)-guided sevoflurane or desflurane administration and BIS-triggered inhalation boluses of sevoflurane or desflurane combined with titration of remifentanil.

METHODS

Fifty morbidly obese patients undergoing laparoscopic gastroplasty received either BIS-guided sevoflurane or desflurane anaesthesia in combination with a remifentanil target-controlled infusion. Intraoperative haemodynamic stability and BIS control were measured. Immediate recovery was recorded.

RESULTS

Intraoperatively, the BIS was between 40 and 60 for a greater percentage of time in the sevoflurane (78 (13)% of case time) than in the desflurane patients (64 (14)% of case time), owing to too profound anaesthesia in the desflurane patients at the start of the procedure. However, fewer episodes of hypotension were found in the desflurane group, without the occurrence of more hypertensive episodes. During immediate recovery, eye opening, extubation, airway maintenance, and orientation occurred sooner in the desflurane group.

CONCLUSIONS

Immediate recovery was significantly faster in the desflurane group. Overall hypnotic controllability measured by BIS was less accurate with desflurane. Overall haemodynamic controllability was better when using desflurane. Fewer episodes of hypotension were found in the desflurane group. The use of the inhalation bolus was found to be appropriate in both groups without causing severe haemodynamic side effects. Minimal BIS values were significantly lower after a desflurane bolus.

A comparison of bispectral index and ARX-derived auditory evoked potential index in measuring the clinical interaction between ketamine and propofol anaesthesia

We evaluated the effects of a bolus (0.4 mg.kg-1) and continuous infusion (1 mg.kg-1.h-1) of ketamine on Bispectral Index (BIS) and A-Line(R) ARX Index (AAI) during propofol anaesthesia. We included 15 ASA I patients scheduled for general anaesthesia. Induction was performed by infusion of propofol at 100 ml.h-1 until loss of consciousness. Both BIS and AAI monitors responded appropriately at that time. The calculated effect site concentration of propofol at loss of consciousness was maintained by means of a computer controlled infusion system. A 'pseudo' steady-state effect site concentration was reached after 4 min. After 1 min of baseline measurements, ketamine was administered. BIS values increased from the 3rd to the 8th min after the administration of ketamine. The AAI showed no significant increase or decrease, but between-patient variability increased.

Propofol versus remifentanil for monitored anaesthesia care during colonoscopy

BACKGROUND AND OBJECTIVE

We conducted an open, prospective, randomized study to compare the efficacy, safety and recovery characteristics of remifentanil or propofol during monitored anaesthesia care in patients undergoing colonoscopy.

METHODS

Forty patients were randomly assigned to receive either propofol (1 mg kg(-1) followed by 10 mg kg (-1) h(-1), n = 20) or remifentanil (0.5 microg kg(-1) followed by 0.2 microg kg(-1) min(-1), n = 20). The infusion rate was subsequently adapted to clinical needs.

RESULTS

In the propofol group, arterial pressure and heart rate decreased significantly from the baseline. These variables remained unchanged in the remifentanil group, but hypoventilation occurred in 55% of patients. Early recovery was delayed in the propofol group (P < 0.002). Recovery of cognitive and psychomotor functions was faster in the remifentanil group. Fifteen minutes after anaesthesia, the Digit Symbol Substitution Test score was 28.6 +/- 12.8 versus 36.2 +/- 9.4 and the Trieger Dot Test score was 25.6 +/- 8.1 versus 18.7 +/- 4.1 in the propofol and remifentanil groups, respectively (both P < 0.05). Patient satisfaction, using a visual analogue scale, was higher in the propofol group (96 +/- 7 versus 77 +/- 21, P < 0.001).

CONCLUSIONS

Remifentanil proved efficient in reducing pain during colonoscopy. Emergence times were shorter and the recovery of cognitive function was faster with remifentanil compared with propofol. Remifentanil provided a smoother haemodynamic profile than propofol; however, the frequent occurrence of remifentanil-induced hypoventilation requires the cautious administration of this agent.

Cost-reduction analysis of propofol versus sevoflurane: maintenance of anaesthesia for gynaecological surgery using the bispectral index

BACKGROUND AND OBJECTIVE

The study was designed to compare the costs of propofol versus sevoflurane for the maintenance of the hypnotic component of anaesthesia during general anaesthesia, guided by the bispectral index, for gynaecological laparoscopic surgery.

METHODS

Forty ASA Grade I-II female patients scheduled for gynaecological laparoscopy were randomly allocated to two groups. All patients received a continuous infusion of remifentanil (0.25 microg kg(-1) min(-1)) for 2 min. Then anaesthesia was induced with propofol 1% at 300 mL h(-1) until loss of consciousness. To guide the bispectral index between 40 and 60, Group 1 patients received propofol 10 mg kg(-1) h(-1) initially, which was increased or decreased by 2 mg kg(-1) h(-1) steps; Group 2 patients received sevoflurane, initially set at 2 vol.% and adjusted with steps of 0.2-0.4%. The time and quality of anaesthesia and recovery were assessed in two postoperative standardized interviews.

RESULTS

Patient characteristics, the propofol induction dose, the bispectral index and the haemodynamic profiles during induction of anaesthesia, and its duration, were similar between the groups. In Group 1, 7.55 +/- 1.75 mg kg(-1) h(-1) propofol and in Group 2, 0.20 +/- 0.09 mL kg(-1) h(-1) liquid sevoflurane were used for maintenance. The cost for maintenance, including wasted drugs, was higher when using propofol (Euro 25.14 +/- 10.69) than sevoflurane (Euro 12.80 +/- 2.67). Postoperatively, recovery profiles tended to be better with propofol; however, the day after discharge no differences were found.

CONCLUSIONS

When applying the bispectral index to guide the administration of hypnotic anaesthetic drugs, propofol-based maintenance of anaesthesia was associated with the highest cost. A trend towards a better recovery profile was obtained with propofol. However, on the day after discharge, no differences in quality were observed.