Controlled Infusion Of Propofol Research Articles

THRIVE: a different approach in microlaryngeal surgeries

<p>Microlaryngeal surgeries (MLS) are typically performed under general anaesthesia either by employing a microlaryngeal tube or without endotracheal intubation using high frequency jet ventilation. Recently, trans-nasal humidified rapid insufflation ventilatory exchange (THRIVE) without ET tube can be used. It has no compromised view/ access as in MLS tube and no barotrauma/movement of vocal cords/ tumour implantation as in jet ventilation. We aimed to assess the feasibility and safety of tubeless MLS using THRIVE. From December 2019 to December 2020, all the patients undergoing tubeless MLS were included. Anaesthesia was conducted with target controlled propofol infusion and muscle relaxation with THRIVE oxygen support. Perioperative data was collected and analysed. A total of 21 patients underwent MLS using THRIVE as the sole method of ventilation. Mean age was 52.6 (±13.77) years, and mean body mass index (BMI) was 25.63 (±4.91) kg/m<sup>2</sup>. The surgical indications were vocal cord tumor/ biopsy and vocal polyp/cyst excision. Mean apnoea time was 27 min. At the end of surgery, mean end tidal CO<sub>2</sub> was 66 mmHg. Surgeon’s satisfaction about the operating field was recorded and he rated it as either excellent (70%) or good (30%). In carefully selected patients, a combination of THRIVE and TIVA offers a good alternative to conventional anaesthesia with tubes. Our study demonstrated a considerable safe apnoea time with an acceptable CO<sub>2</sub> build up. Surgeon acceptance of the technique was extremely promising and the operating conditions were highly rated by them.</p>

Awake Sedation With Propofol Attenuates Intraoperative Stress of Carotid Endarterectomy in Regional Anesthesia

Carotid endarterectomy in regional anesthesia is often associated with increased perioperative stress. We assumed that carotid endarterectomy performed under awake sedation with propofol is more beneficial to prevent such stress than alprazolam premedication only. A total of 47 consecutive patients with significant carotid artery stenosis were enrolled into this investigation and followed up for 5years to explore vascular complications. All operations were performed under regional anesthesia. As premedication, all patients took 0.5mg of alprazolam 30minutes before the procedure. After randomization, 22 patients had awake sedation with target controlled propofol infusion, and the other 25 had only premedication. Cortisol plasma levels were serially analyzed: before surgery (T1), before (T2) and after release of carotid clamp (T3), and at 2 (T4) and 24 postoperative hours (T5). Alprazolam levels were also measured before and after the surgery. The plasma concentration of cortisol was significantly lower in the propofol sedation group at T2 (P<0.001), T3 (P=0.001), and T4 (P<0.001) than in the alprazolam-only group. Alprazolam levels did not correlate with cortisol levels at any time point. A significant positive correlation was found between the clamp time and plasma cortisol level at T3 (P=0.018), similarly between the degree of contralateral carotid stenosis and plasma cortisol level at T3 (P=0.03). Plasma cortisol concentration 2hours after the operation (T4) proved to be an independent predictor of carotid restenosis during the 5-year follow-up (odds ratio: 1.67, 95% confidence interval: 1.02-2.73, P=0.04). An additional intraoperative propofol sedation provides better stress relief than alprazolam-only premedication during awake carotid endarterectomy.

Photoplethysmography Response to Laryngeal Mask Airway Insertion during Propofol-Remifentanil Anethesia.

The present study was aimed to evaluate the abilities of photoplethysmography (PPG)-derived parameters, including sample entropy of PPG (SampEn), amplitude of PPG (PPGA), pulse beat interval (PBI) and diastolic interval (DI) extracted by nonlinear or linear methods, to monitor the balance between nociception and antinociception. 26 ASA I or II patients were randomized into one of the three groups to receive a remifentanil effect-compartment target controlled infusion (Ceremi) of 1, 3 and 5 ng/ml and an effect-compartment target controlled propofol infusion (Ceprop) to keep the state entropy (SE) at 50 (40~60). Laryngeal mask airway (LMA) insertion was applied as a noxious stimulus. The percentage of change in SampEn (△SampEn, AUC=0.896), PBI (△PBI, AUC=0.896) and DI (ΔDI, AUC=0.972), but not in PPGA (△PPGA, AUC=0.667), were statistically excellent in discriminating low Ceremi (1 ng/ml) from higher Ceremi (3 and 5 ng/ml). Additionally, the prediction probabilities (Pk) values of △SampEn, ΔPBI and ΔDI were high as well with 0.795, 0.754 and 0.813 for discriminating Ceremi. These results demonstrated that nonlinear and linear parameters of SampEn, PBI and DI had strong dependency on Ceremi in response to LMA insertion and could provide nociceptive information during propofol-remifentanil anesthesia. This indicated that PPG-derived parameters were potential to develop the clinical assessment of nociception-antinociception balance under general anesthesia.

Early post-operative cognitive dysfunction after closed-loop versus manual target controlled-infusion of propofol and remifentanil in patients undergoing elective major non-cardiac surgery: Protocol of the randomized controlled single-blind POCD-ELA trial.

Introduction:Post-operative cognitive dysfunction (POCD) is frequent in patients older than 60 years undergoing major non-cardiac surgery, and increases both morbidity and mortality. Anesthetic drugs may exert neurotoxic effects and contribute to the genesis of POCD. The hypothesis of the POCD-ELA trial was that closed-loop target-controlled infusion of propofol and remifentanil could reduce the occurrence of POCD by decreasing the risk of excessive depth of anesthesia and the dose of anesthetic drugs.Methods and analysis:We designed a single-center, single-blind, randomized, controlled, parallel trial and aim to include 204 patients aged >60 years undergoing elective major non-cardiac surgery. Patients will be randomized to receive closed-loop versus manual target-controlled infusion of propofol and remifentanil guided by bispectral index monitoring. Cognitive assessment will be performed the day before surgery (baseline) and within 72 hours after surgery, using a battery of validated neuropsychological tests. The primary outcome is the incidence of POCD within 72 hours after surgery. POCD is defined as a Z-score value > 1.96 for at least 2 different tests or a Z-score composite value >1.96. The calculation of the Z-score is based on data from an age-matched control population who did not undergo surgery or general anesthesia.Ethics and dissemination:This study was approved by the Ethics Committee (Comité de Protection des Personnes Est-II) and authorized by the French Health Products Agency (Agence Nationale de Sécurité des Médicaments, Saint-Denis, France). The University Hospital of Besancon is the trial sponsor and the holder of all data and publication rights. Results of the study will be submitted for publication in a peer-review international medical journal and for presentation in abstract (oral or poster) in international peer-reviewed congresses.Registration:The trial is registered with ClinicalTrials.gov (Identifier: NCT02841423, principal investigator: Prof Emmanuel Samain, date of registration: July 22, 2016). Last amendment of protocol: version 8.0 April 2018.

The study of safety and saving efficacy on bispectral index-based closed-loop target controlled infusion propofol with bispectral index-target controlled infusion pump for gynecological laparoscopic surgery

Objective To observe hemodynamic change and saving efficacy in patients undergone gynecological laparoscopic surgery under closed-loop control of target controlled infusion(TCI) propofol guided by BIS with BIS-TCI pump. To explore the guiding effect and reference value of BIS-TCI pump on accurate implementation of total intravenous anesthesia. Methods Forty patients who experienced gynecological laparoscopic surgery were enrolled in this study and divided into two groups randomly. The anesthesia was maintained with closed-loop control of propofol TCI guided by BIS with BIS-TCI pump in the closed-loop group. While the anesthesia was maintained with manually regulating plasma concentration 2-5 mg/L of propofol TCI guided by BIS with TCI pump in the opened-loop group. The target BIS value was 50±5. The plasma concentration 4 μg/L of remifentanil TCI was used for analgesia. BIS value, MAP, HR were recorded for each patient at the time point of pre-anesthesia, tracheal intubation, 1 min after tracheal intubation, 5 min after tracheal intubation, skin incision, 30 min after skin incision, skin suture, the end of surgery, consciousness recovery, extubation, 5 min after extubation. The consumption of propofol, the anesthesia recovery time, the score of numerical rating scale(NRS) and Ramsay were also recorded. Results The dosage of propofol during the anesthesia was decreased by 10% in the closed-loop group which compared with opened-loop group[(6.2±1.4) mg·kg-1·h-1 vs (6.9±1.0) mg·kg-1·h-1(P>0.05). BIS value, MAP, HR between the two groups had no significant differences at the each time point (P>0.05), but the hemodynamic change at the time point of skin incision was less in the closed-loop group compared with opened-loop group(P 0.05). Conclusions Compared with the opened-loop control of propofol TCI guided by BIS with TCI pump, the closed-loop control of propofol TCI guided by BIS with BIS-TCI pump could be safely applied in clinic, made the infusion of anesthetics more individually, and decreased the consumption of propofol. At the same time, closed-loop controlled infusion with BIS-TCI pump can also decrease the anesthesiologist's workload and make patients pass the peri anesthesia period smoothly and safely. Key words: Bispectral index; Target controlled infusion; Propofol; Laparoscopic surgerical procedures

The comparison of predictive performance in bispectral index prediction during target effect-site controlled infusion of propofol using different blood effect-site equilibration rate constants in the same pharmacokinetic model

BackgroundBlood-brain equilibration rate constant (ke0) is derived from either pharmacokinetic and pharmacodynamic modeling (ke0_model) or a model-independent observed time to peak effect (ke0_tpeak). Performance in bispectral index (BIS) prediction was compared between ke0_model and ke0_tpeak for microemulsion or long chain triglyceride (LCT) propofol.MethodsTime to peak effect (tpeak, time to a maximally reduced BIS value) of microemulsion propofol after an intravenous bolus (1 mg/kg) was measured in 100 patients (group Amicro). An observed tpeak of 1.6 min for LCT propofol was obtained from an earlier study. Another 40 patients received a target controlled infusions of microemulsion propofol (ke0_model = 0.187/min, group Bmicro = 20) or LCT propofol (ke0_model = 0.26/min, group BLCT = 20) and remifentanil. The ke0_tpeak's in group Bmicro and BLCT were calculated using the observed tpeak value obtained from group Amicro and 1.6 min, respectively. Effect-site concentrations of propofol were recalculated using the amounts of propofol infused over time and ke0_tpeak's. Predicted BIS values calculated by sigmoid Emax equations with ke0_model and ke0_tpeak were compared with observed BIS values during induction and emergence for both formulations of propofol.ResultsObserved tpeak of microemulsion propofol was 1.68 min. The median performance errors of BIS in group Bmicro were -1.83% (-24.8 to 18.9, ke0_model) and -2.42% (-26.1 to 36.2, ke0_tpeak), while 8.01% (-20.5 to 30.1, ke0_model) and 7.37% (-27.0 to 49.1, ke0_tpeak) in group BLCT. The median absolute performance errors of BIS in group Bmicro were 11.87% (2.2-31.1ke0_model) and 14.38% (-0.6 to 44.6, ke0_tpeak), while 17.31% (5.54-36.0, ke0_model) and 18.28% (-0.1 to 56.0, ke0_tpeak) in group BLCT.ConclusionsThe ke0_model showed better performance in BIS prediction than the ke0_tpeak.

Effect of hypercapnia on pleth variability index during stable propofol: Remifentanil anesthesia

Background:The pleth variability index (PVI), which is calculated from respiratory variations in the perfusion index (PI), has been shown to predict fluid responsiveness in mechanically ventilated patients; however, vasomotor tone changes induced by hypercapnia can affect PI and hence may slim down the accuracy of PVI. This study was designed to find out the impact of mild hypercapnia on PVI.Methods:A total of 30 patients were randomized after induction of general anesthesia with target controlled infusion propofol and remifentanil to either hypercapnia, (etCO2 =45 mmHg), (group 1, 15 patients) or normocapnia (etCO2 =35 mmHg) (group 2, 15 patients). After a stabilization period of 10 min, patients were crossed over to the other intentional level of etCO2. Heart rate (HR), mean arterial pressure (MAP), PI, PVI were collected at the end of each stabilization period.Results:Patient characteristics and baseline values of HR, MAP, PI and PVI were comparable between the groups. Carryover effect was statistically excluded. Hypercapnia significantly increased PI and decreased PVI with significant negative correlation.Conclusion:Hypercapnia retracts back PVI values compared with normocapnia. Precise judgment of fluid responsiveness as indicated by PVI necessitates its comparison against similar etCO2 levels.

Different infusion methods of propofol in the anesthesia for the aged more than 80 years during painless colonoscopy

Objective To investigate the results of three formula of anesthesia management of propofol in the aged more than 80 years during colonoscopy. Methods 120 aged patients＞80 years scheduled to undergo painless colonoscopy were randomly divided into three groups,Group Ⅰ,Ⅱ and Ⅲ,each group 40 patients.Patients in Group Ⅰ received target controlled infusion of propofol and in Group Ⅱ received continuous infused propofol by vein pump,while patients in Group Ⅲ received manual controlled infusion of propofol.MAP、ECG、HR、SpO2 were recorded before colonoscopy,during and after colonoscopy.Anesthetic induction time,length of colonoscopy time,total propofol dosage,recovery time,side effects and satisfaction were also recorded. Results All patients had finished colonoscopy safely.There is no difference about MAP,ECG,HR and SpO2 among the three groups.The anesthetic induction time were (40±6),(58±10),(58±8) s,respectively.The recovery time were (3.7±1.3),(5.0±1.8),(6.9±1.7)min,respectively.The total propofol dosage were (91±11), (1 10±14), (131±16) mg,respectively.In Group Ⅰ,lower propofol dosage was recorded,anesthetic induction time and recovery time were shorter than those in Group Ⅱ and Ⅲ.The side effects were the least in Group Ⅰ and its satisfaction was the best. Conclusions It is satisfactory in aged patients＞80 years to administer propofol with different administration ways during colonoscopy.Target controlled infusion (TCL) of propofol may be the better way for the anesthesia ofthe aged during painless colonoscopy. Key words: The aged＞80 years; Painless colonoscopy; Propofol; Target controlled infusion

Spectral Entropy as a Measure of Hypnosis and Hypnotic Drug Effect of Total Intravenous Anesthesia in Children during Slow Induction and Maintenance

We evaluated whether spectral entropy (SpE) can measure the depth of hypnosis and the hypnotic drug effect in children during total intravenous anesthesia. Sixty healthy children, aged 3-16 yr, were studied. Anesthesia was induced with an increasing target controlled infusion of propofol, and maintained by a stable remifentanil infusion and variable concentrations of target controlled infusion propofol. Depth of hypnosis was assessed according to the University of Michigan Sedation Scale (UMSS). Estimated plasma (C(p)) and pseudo effect site (C(eff)) propofol concentrations reflected the hypnotic drug effect. Patients were stratified to three age groups. The correlations between SpE versus UMSS, C(p), and C(eff) were analyzed by Prediction Probability (P(k)). The pharmacodynamic relationship between SpE and C(p), and the differences of SpE values between the age groups at the corresponding UMSS levels, were studied. Respective mean P(k) values for the youngest, middle, and oldest age groups were: 1) during induction: SpE versus UMSS 0.87, 0.87, and 0.93; SpE versus C(p) 0.92, 0.95, and 0.97; and SpE versus C(eff) 0.88, 0.94, and 0.95; 2) during maintenance: SpE versus C(eff) 0.86, 0.75, and 0.81. The pharmacodynamic analysis determined an association between SpE and C(p) that followed the E(max) model closely. There were significant differences in SpE values between age groups at corresponding UMSS sedation levels. SpE measures the level of hypnosis and hypnotic drug effect in children during total intravenous anesthesia. There is an age dependency associated with SpE. Anesthesia should not be steered solely on the basis of SpE.

A comparison of the effectiveness of dexmedetomidine versus propofol target‐controlled infusion for sedation during fibreoptic nasotracheal intubation

Fibreoptic intubation is a valuable modality for airway management. This study aimed to compare the effectiveness of dexmedetomidine vs target controlled propofol infusion in providing sedation during fibreoptic intubation. Forty patients with anticipated difficult airways and due to undergo tracheal intubation for elective surgery were enrolled and randomly allocated into the dexmedetomidine group (1.0 microg.kg(-1) over 10 min) (n = 20) or the propofol target controlled infusion group (n = 20). Intubating conditions and patient tolerance as graded by a scoring system were evaluated as primary outcomes. Intubation was successful in all patients. Satisfactory intubating conditions were found in both groups (19/20 in each group). The median (IOR [range]) comfort score was 2 (1-2 [1-4]) in the dexmedetomidine group and 3 (2-4 [2-5]) in the propofol group (p = 0.027), favouring the former. The dexmedetomidine group experienced fewer airway events and less heart rate response to intubation than the propofol group (p < 0.003 and p = 0.007, respectively). Both dexmedetomidine and propofol target-controlled infusion are effective for fibreoptic intubation. Dexmedetomidine allows better tolerance, more stable haemodynamic status and preserves a patent airway.

Behaviour of spectral entropy, spectral edge frequency 90%, and alpha and beta power parameters during low-dose propofol infusion

BackgroundIn this study we analyse the behaviour, potential clinical application and optimal cortical sampling location of the spectral parameters: (i) relative alpha and beta power; (ii) spectral edge frequency 90%; and (iii) spectral entropy as monitors of moderate propofol-induced sedation. MethodsMulti-channel EEG recorded from 12 ASA 1 (American Society of Anesthesiologists physical status 1) patients during low-dose, target effect-site controlled propofol infusion was used for this analysis. The initial target effect-site concentration was 0.5 μg ml−1 and increased at 4 min intervals in increments of 0.5 to 2 μg ml−1. EEG parameters were calculated for 2 s epochs in the frequency ranges 0.5–32 and 0.5–47 Hz. All parameters were calculated in the channels: P4–O2, P3–O1, F4–C4, F3–C3, F3–F4, and Fp1–Fp2. Sedation was assessed clinically using the OAA/S (observer’s assessment of alertness/sedation) scale. ResultsRelative beta power and spectral entropy increased with increasing propofol effect-site concentration in both the 0.5–47 Hz [F(18, 90) = 3.455, P<0.05 and F(18, 90) = 3.33, P<0.05, respectively] and 0.5–32 Hz frequency range. This effect was significant in each individual channel (P<0.05). No effect was seen of increasing effect-site concentration on relative power in the alpha band. Averaged across all channels, spectral entropy did not outperform relative beta power in either the 0.5–32 Hz [Pk=0.79 vs 0.814 (P>0.05)] or 0.5–47 Hz range [Pk=0.81 vs 0.82 (P>0.05)]. The best performing indicator in any single channel was spectral entropy in the frequency range 0.5–47 Hz in the frontal channel F3–F4 (Pk=0.85). ConclusionsRelative beta power and spectral entropy when considered over the propofol effect-site range studied here increase in value, and correlate well with clinical assessment of sedation.

A clinical study of general anesthesia using target controlled infusion of propofol and remifentanil on the aged patient

目的 通过BIS监测丙泊酚靶控输注复合瑞芬太尼麻醉在老年病人手术中的临床应用探讨适合于老年病人的最佳丙泊酚一瑞芬太尼靶浓度.方法 选择ASA Ⅰ-Ⅲ级、年龄≥65岁老年病人60例,随机分为3组,每组20例:(1)组,丙泊酚血浆Ct(Ctpro)2 mg/L;(2)组,Ctpro 3 mg/L;(3)组,ctpro 4 mg/L.三组的瑞芬太尼血浆Ct(CtR)都是5 μg/L.用TCI泵进行丙泊酚分步诱导,当Ctpro达所设值时,开始瑞芬太尼靶控输注,静注琥珀胆碱插管,观察BIS变化.术中维持每组所设Ctpro和CtR.如果HR＜50 bpm,静注阿托品;SBP＜基础值的30%,静注麻黄碱;SBP＞基础值30%或者HR＞90 bpm,增加Ctpro.术中观察麻醉前、诱导、插管、插管后5 min及术中血液动力学变化;麻醉诱导及术中阿托品、麻黄素的使用情况;术毕清醒时间及拔管时间;术后并发症的发生率.结果 SBP:第(1)组病人插管时、插管后5 min及术中SBP明显升高,与麻醉前相比P＜0.01;第(2)组和第(3)组病人诱导、插管后5 min及术中SBP明显降低,与麻醉前相比P＜0.01,其中第(3)组更明显.HR:第(1)组病人诱导时HR明显降低,而插管时却明显升高,与麻醉前相比P＜0.01;第(2)组病人诱导和插管后5 min明显降低,与麻醉前相比P＜0.01;第(3)组病人诱导、插管及术中均明显降低,与麻醉前相比P＜0.01.BIS:三组病人的BIS值在诱导、插管、插管后及术中与麻醉前相比均明显降低,P＜0.01.麻醉诱导及术中第(3)组患者阿托品、麻黄素的使用率明显高于另外两组,P＜0.01.术毕三组患者清醒时间、拔管时间、并发症的发生率相比无统计学差异.结论 BIS监测下丙泊酚靶控输注复合瑞芬太尼麻醉应用于老年病人手术,术毕清醒快、拔管早,术后并发症少.其中麻醉诱导阶段Ctpro3.0 mg/L+CtR5.0 μg/L组血流动力学较为稳定,麻醉维持阶段ctpro2.0 mg/L～3.0 mg/L+CtR5.0 μg/L组血流动力学较为稳定。

The Effect of the Level of Sedation on Recovery in Patients undergoing Target Controlled Propofol Infusion with a Bolus of Fentanyl for Strabismus Surgery

Background: An immediate examination of ocular movement is required during strabismus surgery. The aim of this study was to determine the effect of the level of sedation on the recovery of patients undergoing a target controlled propofol infusion with a bolus of fentanyl for strabismus surgery. Methods: Twenty-one outpatients scheduled to undergo strabismus surgery were assigned randomly to one of two groups. In both groups, sedation was induced with a bolus of fentanyl 1μg/kg intravenously followed by an infusion of propofol with a target concentration of 1.0μg/ml. The target concentration was increased or decreased by 0.1 μg/ml steps until the patient reached and maintained the observer's assessment of alertness/sedation (OAA/S) scale score of 3 (group A) or 4 (group B). The supplemental analgesics consisted of fentanyl 25－50μg bolus injection. The target concentration of propofol, the total dose of fentanyl, delayed awakening, and recovery time were recorded. Results: The mean target concentration of propofol (mean ± SD) in group A (1.8 ± 0.4μg/ml) was significantly higher than that of group B (1.3 ± 0.4μg/ml) (P ＜ 0.05). There were no significant differences in the total dose of fentanyl, delayed awakening and recovery time between the two groups. There was an an increasing trend in the recovery time with the total dose per kilogram of body weight of fentanyl (Spearman's correlation coefficient, r = 0.384, P = 0.086). Conclusions: The levels of sedation did not affect the recovery time in patients during target propofol infusion with a bolus of fentanyl. However, the addition of fentanyl tended to prolo ng the recovery time. (Korean J Anesthesiol 2007; 52: S 42～6)

Tracheal Intubating Conditions and Hemodynamic Change in Ambulatory Surgery: Propofol and Remifentanil Target Controlled Infusions with Low Dose Rocuronium

Background: This study evaluated the tracheal intubating conditions and hemodynamic changes in tracheal intubation according to the different effect-site concentrations of remifentanil combined with a target controlled infusion (TCI) of propofol using low dose rocuronium. Methods: Forty-five patients presenting for ambulatory surgery were randomly assigned to one of three groups according to the target effect-site concentration of remifentanil: 2.5 ng/ml (group R2.5), 3.0 ng/ml (group R3.0), 3.5 ng/ml (group R3.5). After midazolam administration, anesthesia was induced using a target effect-site controlled infusion of propofol 4.0μg/ml, which was then reduced to 2.5μ g/ml. At the same time, a TCI of remifentanil was started. A neuromuscular blockade was produced by rocuronium 0.4 mg/kg. The trachea was intubated 4 min after induction. The tracheal intubation conditions were assessed using a standard scoring system. The noninvasive arterial blood pressure, heart rate (HR), and bispectral index were recorded at 1 min intervals from the start of induction to 5 min after intubation. Results: Intubation was successful in all patients except for one in the R2.5 group. The number of excellent intubating conditions was significantly higher in the R3.5 group (12/15) than in the R2.5 group (6/15) (P ＜ 0.05). The mean arterial pressure (MAP) in the R2.5 and R3.0 groups increased significantly at 1 min after intubation (P ＜ 0.05), but the MAP in the R3.5 group increased slightly at 1 min after intubation.

Regional anaesthesia and propofol sedation for carotid endarterectomy

Many surgeons now perform carotid endarterectomy under regional anaesthesia. The aim of the present study was to review a sedation technique using a computer-controlled infusion of propofol. A consecutive series of 84 carotid endarterectomies done by a single surgeon and commenced under regional anaesthesia with sedation was studied. There were 54 men and 27 women (three bilateral procedures), with a median age of 71 years (range 48-87 years). All patients had carotid stenosis > 70% 80 procedures were done for symptomatic disease and three asymptomatic patients were treated before cardiac surgery (one bilateral). Seventy-seven procedures were completed under regional anaesthesia and sedation alone; seven required conversion to general anaesthetic, usually for intolerance of the operation. An intraoperative shunt was required on only four occasions (5%). Postoperatively eight patients required critical care monitoring, usually for blood pressure control. The remainder were nursed on the vascular ward, and 68% were discharged home on the day after surgery. No patient died, but there were two neurological complications. One patient had a cerebellar stroke 10 days after surgery, but recovered fully after 4 months. A second developed cerebral oedema due to severe intraoperative hypertension and required intensive care for 15 days. He too recovered fully. Five patients had a further episode of transient cerebral ischaemia within 1 month of operation, but in all cases duplex imaging showed a widely patent carotid and there were no sequelae. Target controlled propofol infusion is an effective method of sedation in patients undergoing carotid endarterectomy.

A Comparison of Target- and Manually Controlled Infusion Propofol and Etomidate/Desflurane Anesthesia in Elderly Patients Undergoing Hip Fracture Surgery

Elderly patients have a higher risk of developing adverse drug reactions during anesthesia, especially anesthesia affecting cardiovascular performance. In this prospective randomized study we compared quality of induction, hemodynamics, and recovery in elderly patients scheduled for hip fracture surgery and receiving either etomidate/desflurane (ETO/DES) or target-controlled (TCI) or manually controlled (MAN) propofol infusion for anesthesia. Sixteen patients were anesthetized with ETO (0.4 mg/kg) followed by DES titrated from an initial end-tidal concentration of 2.5%. Eighteen patients received propofol TCI at an initial plasma concentration of 1 microg/mL and titrated upwards by 0.5-microg/mL steps. Fifteen patients received a bolus induction of propofol 1 mg/kg over 60 s followed by an infusion initially set at 5 mg . kg(-1) . h(-1). All received a bolus (20 microg/kg) followed by an infusion of 0.4 microg . kg(-1) . min(-1) alfentanil. According to hemodynamics, concentrations of DES or propofol (TCI group) and propofol infusion rate (MAN group) were respectively adjusted by a step of 20% and 50%. In the TCI and ETO/DES groups, the time spent at a mean arterial blood pressure within 15% and 30% of baseline values was more than 60% and 80% of anesthesia time, whereas in the MAN group it was <30% and 60%, respectively. In the MAN group more anesthetic drug adjustments were recorded (6.4 +/- 2.8 versus 2.5 +/- 1.2 [ETO/DES] and 2.6 +/- 1 [TCI]). TCI improves the time course of propofol's hemodynamic effects in elderly patients.

Precision and bias of target controlled propofol infusion for sedation

The purpose of this study is to test precision and systematic bias of a target controlled infusion (TCI) of propofol in human volunteers at two sedative concentrations. We studied the 'Diprifusor' model (Marsh Pharmacokinetics and a Graseby 3400 infusion pump) in 18 human volunteers at two sedative target plasma concentrations (0.5 and 1.0 microg ml(-1)). Twenty minutes after infusion start or change and 20 min after discontinuation of the infusion plasma propofol concentrations were measured using liquid chromatography-mass spectroscopy (LC-MS). Plasma propofol concentrations were compared with concentrations predicted by the TCI system. Agreement of those two measures (precision and bias) was determined using regression analysis. We found little systematic bias but poor precision. When setting the TCI system to deliver a plasma concentration of 1.0 microg ml(-1) one can predict the actual plasma concentration with 95% confidence only within a range of 0.44-1.38 microg ml(-1). This finding helps to explain differences in responses to propofol sedation; pharmacokinetic variability appears to be an important factor.

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

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. 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. 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. 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).

THIS MONTH IN ANESTHESIOLOGY

THIS MONTH IN ANESTHESIOLOGY

Psychomotor recovery after sedation for outpatient colonoscopy:target controlled propofol infusion is significantly better than morphine and midazolam

s and Programme: European Society of Anaesthesiologists; 9th Annual Meeting with the Swedish Society of Anaesthesiology; Gothenburg, Sweden, 7-10 April 2001: Ambulatory Anaesthesia