Target-controlled infusion versus manually-controlled infusion of propofol for general anaesthesia or sedation in adults

Comparison of recovery profiles in target-controlled infusions (TCI) versus manually controlled infusions for total intravenous anesthesia (TIVA) in laparoscopic surgeries. A randomized controlled trial

Background and Aims

Considerable importance has been attached to early recovery and discharge readiness after surgeries. Many centers use total intravenous anesthesia (TIVA) as their anesthesia technique of choice. Target-controlled infusions (TCI) have been proposed as a method to precisely deliver continuous infusions of propofol and opioids as compared to the traditionally used manual-controlled infusion (MCI) methods. However, TCI has also been shown to result in the administration of larger doses of propofol which could cause delayed emergence and recovery from anesthesia. Studies involving TCI have focused mainly on its effects on anesthesia induction but not much literature is available on recovery profiles of patients on TCI. This study was designed to compare the effect of conventionally used MCI methods versus the target-controlled infusion (TCI) method of administering TIVA on recovery characteristics in patients undergoing laparoscopic surgery.

Material and Methods

This was a prospective randomized interventional study on 54 patients. Our primary objective was to compare the rates of recovery from anesthesia as judged by four parameters. Time to return of spontaneous ventilation, time to respond to verbal commands, time to extubation, and time to shift patient out of the operating room after stoppage of propofol infusion. As secondary objectives, intraoperative average bispectral index (BIS) values and total anesthetic drugs (propofol and fentanyl) consumption were also compared.

Results

We noted that for laparoscopic surgeries lasting less than 4 hours, both MCI and TCI techniques of TIVA have comparable rates of recovery after the stoppage of propofol infusion. Total consumption of propofol and fentanyl was also similar; however, with the use of the TCI method of TIVA, better depth of anesthesia as evidenced by lower average BIS levels was noted.

Conclusion

Recovery rates after TIVA using a target-controlled infusion (TCI) system are similar to BIS-guided MCIs in patients undergoing laparoscopic surgery lasting less than 4 hours. TCI resulted in better depths of anesthesia though per kg/min consumption of propofol was found to be more.

Target-Controlled Anesthesia Reduces Postoperative Delirium in Spinal Surgical Patients: A Prospective Pilot Study

The aim of this pilot study was to examine the effect of combined target-controlled anesthesia and manually controlled anesthesia on the incidence of postoperative delirium (POD) in patients undergoing spinal surgery. All of the patients were enrolled before spinal surgery and divided into 2 groups at random: one group received combined sevoflurane target-controlled inhalation and sufentanil target-controlled infusion (S-S TCI group), whereas the other received combined manually controlled sevoflurane inhalation and sufentanil infusion (S-S MCI group). Data related to preoperative factors, perioperative factors, and postoperative data were retrospectively collected. Compared with the S-S MCI group, the dosage of vasoactive drugs after surgery, postoperative recovery time, time to cannula removal, and the incidence of POD were significantly decreased in the S-S TCI group (P < 0.05). Overall, POD appeared in 81 patients (16.8%) by postoperative day 3. Multiple regression analysis showed that postoperative blood loss and manually controlled anesthesia were risk factors for POD in spinal surgery patients. Therefore, prophylactic blood transfusion and phenylephrine can reduce the incidence of POD in the presence of postoperative hypotension. Target-controlled anesthesia may improve the quality of anesthesia as well as reduce POD in spinal surgical patients. These results provide clinical evidence for improving the prevention, diagnosis, and management of POD.

A "Smart" Biosensor-Enabled Intravascular Catheter and Platform for Dynamic Delivery of Propofol to "Close the Loop" for Total Intravenous Anesthesia

BACKGROUND

Target-controlled infusion anesthesia is used worldwide to provide user-defined, stable, blood concentrations of propofol for sedation and anesthesia. The drug infusion is controlled by a microprocessor that uses population-based pharmacokinetic data and patient biometrics to estimate the required infusion rate to replace losses from the blood compartment due to drug distribution and metabolism. The objective of the research was to develop and validate a method to detect and quantify propofol levels in the blood, to improve the safety of propofol use, and to demonstrate a pathway for regulatory approval for its use in the USA.

METHODS

We conceptualized and prototyped a novel "smart" biosensor-enabled intravenous catheter capable of quantifying propofol at physiologic levels in the blood, in real time. The clinical embodiment of the platform is comprised of a "smart" biosensor-enabled catheter prototype, a signal generation/detection readout display, and a driving electronics software. The biosensor was validated in vitro using a variety of electrochemical methods in both static and flow systems with biofluids, including blood.

RESULTS

We present data demonstrating the experimental detection and quantification of propofol at sub-micromolar concentrations using this biosensor and method. Detection of the drug is rapid and stable with negligible biofouling due to the sensor coating. It shows a linear correlation with mass spectroscopy methods. An intuitive graphical user interface was developed to: (1) detect and quantify the propofol sensor signal, (2) determine the difference between targeted and actual propofol concentration, (3) communicate the variance in real time, and (4) use the output of the controller to drive drug delivery from an in-line syringe pump. The automated delivery and maintenance of propofol levels was demonstrated in a modeled benchtop "patient" applying the known pharmacokinetics of the drug using published algorithms.

CONCLUSIONS

We present a proof-of-concept and in vitro validation of accurate electrochemical quantification of propofol directly from the blood and the design and prototyping of a "smart," indwelling, biosensor-enabled catheter and demonstrate feedback hardware and software architecture permitting accurate measurement of propofol in blood in real time. The controller platform is shown to permit autonomous, "closed-loop" delivery of the drug and maintenance of user-defined propofol levels in a dynamic flow model.

Propofol Sedation for Intragastric Balloon Removal: Looking for the Optimal Body Weight Descriptor

AIM

Sedation is considered as a prerequisite for the safe and effective conclusion of Bioenterics Intragastric Balloon (BIB) removal (our aim was to ascertain the most appropriate body size scalars for propofol dosing and assess the efficacy and safety of a sedative approach involving the infusion of propofol for BIB removal.

METHOD

Retrospective analysis of prospectively collected data of 414 adults scheduled to undergo BIB removal. Our primary end-point was to delineate the relationship between propofol dosing and body size descriptors namely body mass index, total body weight, ideal body weight, lean body weight (LBW) and normalized LBW. Sedative efficacy of this practice, anesthesia or procedural-related adverse events and patients' satisfaction level served as secondary outcome parameters.

RESULTS

Propofol dose (mg/kg/min) was positively related to all body weight descriptors in an important manner (p < 0.001). Among them, LBW was singled out as the body size descriptor to best capture the appropriate needs of propofol (R² = 0.432; p = 0.000). Hypoxemia, hemodynamic compromise, gastroesophageal reflux or moderate movement occurred rarely; all of them were readily reversed. The majority of participants had no recollection of the noxious phase of the procedure or declared at least adequately satisfied from the experience (84% and 95%, respectively).

CONCLUSION

LBW could serve as relatively more accurate dosing scalar compared to actual or ideal body weight descriptors, in obese individuals undergoing BIB removal under propofol sedation. The conscious/deep sedation based on propofol infusion emerges as a feasible and efficacious sedative approach for this procedure.

Operative Gynecological Laparoscopy Under Conscious Sedation

BACKGROUND AND OBJECTIVES

Operative laparoscopy is generally performed under general anesthesia. Local anesthesia and conscious sedation may be useful in select short procedures. In the present study, we evaluated safety and efficacy of operative laparoscopy under conscious sedation.

METHODS

Retrospective observational study evaluating patients undergoing gynecologic laparoscopy. Laparoscopy under conscious sedation was performed for each patient with umbilical direct insertion of a 12-mm port, followed by 2 ancillary ports at 1 cm medially to the anterior superior iliac spine. Conversion to conventional laparoscopy or laparotomy was recorded. Conscious sedation was obtained using Remifentanil and Propofol, administered by an infusion system based on pharmacokinetic and pharmacodynamic models. Local anesthesia was administered at port insertion sites and for paracervical block. Pain intensity was evaluated with the Visual Analog Scale (VAS). Adverse events and drug concentrations throughout the procedure were retrieved.

RESULTS

Our study population included 166 patients. They underwent laparoscopic unilateral versus bilateral salpingo-oophorectomy, ovarian cystectomy, bilateral salpingo-oophorectomy and omentectomy for a borderline ovarian tumor, myomectomy; or underwent surgery for unexplained infertility evaluation, pelvic pain, staging of ovarian cancer. Mean duration of pneumoperitoneum was 22.3 ± 7.2 min. Rate of conversion to laparoscopy under general anesthesia was 17/166 (10.2%) and there were only 3 cases of patients with low tolerability to the procedure. No severe adverse events occurred. Hospital discharge occurred in all unconverted cases after 6 to 18 h.

CONCLUSIONS

Operative laparoscopy under conscious sedation and local anesthesia appears to be a feasible technique in gynecologic surgery with no adverse patient outcomes.

The Role of GABA Receptor Agonists in Anesthesia and Sedation

GABA (γ-aminobutyric acid) receptors, of which there are two types, are involved in inhibitory synapses within the central nervous system. The GABA_A receptor (GABAAR) has a central role in modern anesthesia and sedation practice, which is evident from the high proportion of agents that target the GABAAR. Many GABAAR agonists are used in anesthesia practice and sedation, including propofol, etomidate, methohexital, thiopental, isoflurane, sevoflurane, and desflurane. There are advantages and disadvantages to each GABAAR agonist currently in clinical use. With increasing knowledge regarding the pharmacology of GABAAR agonists, however, newer sedative agents have been developed which employ 'soft pharmacology', a term used to describe the pharmacology of agents whereby their chemical configuration allows rapid metabolism into inactive metabolites after the desired therapeutic effect(s) has occurred. These newer 'soft' GABAAR agonists may well approach ideal sedative agents, as they can offer well-controlled, titratable activity and ultrashort action. This review provides an overview of the role that GABAAR agonists currently play in sedation and anesthesia, in addition to discussing the future role of novel GABAAR agonists in anesthesia and sedation.

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.

SEDATION IN COLONOSCOPY BY USING THREE DIFFERENT PROPOFOL INFUSION METHODS AND ANALYSIS OF PLASMA CONCENTRATION LEVELS: A PROSPECTIVE COMPARATIVE STUDY

Background

The propofolemia becomes directly linked to the clinical effects of this anesthetic and is the focus for studies comparing propofol clinical use, in different administration methods routinely used in endoscopy units where sedation is widely administered to patients.

Aim

To evaluate the effects of three different regimens of intravenous propofol infusion in colonoscopies.

Methods

A total of 50 patients that underwent colonoscopies were consecutively assigned to three groups: 1) intermittent bolus infusion; 2) continuous manually controlled infusion; 3) continuous automatic infusion. Patients were monitored with Bispectral IndexTM (BIS) and propofol serum levels were collected at three different timepoints. The development of an original dilution of propofol and an inventive capnography catheter were necessary.

Results

Regarding clinical outcomes, statistical differences in agitation (higher in group 1, p=0.001) and initial blood pressure (p=0.008) were found. As for propofol serum levels, findings were similar in consumption per minute (p=0.748) and over time (p=0.830). In terms of cost analysis, group 1 cost was R$7.00 (approximately US$2,25); group2, R$17.50 (approximately US$5,64); and group 3, R$112.70 (approximately US$36,35, p<0.001). Capnography was able to predict 100% of the oxygen saturation drop (below 90%).

Conclusion

The use of propofol bolus administration for colonoscopies, through continuous manually controlled infusion or automatic infusion are similar regarding propofolemia and the clinical outcomes evaluated. The use of an innovative capnography catheter is liable and low-cost solution for the early detection of airway obstruction.

Effect of desflurane-remifentanil vs. Propofol-remifentanil anesthesia on arterial oxygenation during one-lung ventilation for thoracoscopic surgery: a prospective randomized trial

BACKGROUND

One-lung ventilation during thoracic surgery frequently disturbs normal systemic oxygenation. However, the effect of anesthetics on arterial oxygenation during one-lung ventilation has not been well established in human study. In this clinical trial, we investigated whether a difference between desflurane-remifentanil and propofol-remifentanil anesthesia can be observed with regard to oxygenation during one-lung ventilation for thoracoscopic surgery.

METHODS

Adult patients with lung cancer, scheduled for video-assisted thoracoscopic lobectomy without preoperative oxygen support, were screened and randomized to receive desflurane or propofol, with remifentanil continuous infusion in both groups. Mechanical ventilation was performed with tidal volume of 8 ml/kg and F_IO₂ 0.5 during two-lung ventilation, and 6 ml/kg and 1.0 during one-lung ventilation, both with positive end-expiratory pressure of 5 cmH₂O. Arterial blood gas analysis was performed preoperatively, during two-lung ventilation, and after 15, 30, 45, and 60 min of one-lung ventilation. The primary endpoint was PaO₂ at 30 min after initiating one-lung ventilation. Statistical analyses included the independent t-test for the primary endpoint and a mixed model with a post-hoc analysis to evaluate the serial changes in values.

RESULTS

Patients were recruited between July 9 and December 2, 2014. In total, 103 patients were analyzed (n = 52 in desflurane group and n = 51 in propofol group). The primary endpoint, PaO₂ at 30 min of one-lung ventilation was lower in the desflurane group than the propofol group (170 ± 72 vs. 202 ± 82 mmHg; p = 0.039). Serial changes in PaO₂ during one-lung ventilation showed lower levels during desflurane anesthesia compared with propofol anesthesia (mean difference, 45 mmHg; 95% confidence interval, 16-75 mmHg; p = 0.003).

CONCLUSIONS

In conclusion, desflurane-remifentanil anesthesia resulted in decreased arterial oxygenation compared with that of propofol-remifentanil anesthesia during one-lung ventilation for thoracoscopic surgery in patients with lung cancer.

TRIAL REGISTRATION

ClinicalTrials.gov identifier: NCT02191371 , registered on July 7, 2014.

Practice guidelines for propofol sedation by non-anesthesiologists: the Korean Society of Anesthesiologists Task Force recommendations on propofol sedation

In South Korea, as in many other countries, propofol sedation is performed by practitioners across a broad range of specialties in our country. However, this has led to significant variation in propofol sedation practices, as shown in a series of reports by the Korean Society of Anesthesiologists (KSA). This has led the KSA to develop a set of evidence-based practical guidelines for propofol sedation by non-anesthesiologists. Here, we provide a set of recommendations for propofol sedation, with the aim of ensuring patient safety in a variety of clinical settings. The subjects of the guidelines are patients aged ≥ 18 years who were receiving diagnostic or therapeutic procedures under propofol sedation in a variety of hospital classes. The committee developed the guidelines via a de novo method, using key questions created across 10 sub-themes for data collection as well as evidence from the literature. In addition, meta-analyses were performed for three key questions. Recommendations were made based on the available evidence, and graded according to the modified Grading of Recommendations Assessment, Development and Evaluation system. Draft guidelines were scrutinized and discussed by advisory panels, and agreement was achieved via the Delphi consensus process. The guidelines contain 33 recommendations that have been endorsed by the KSA Executive Committee. These guidelines are not a legal standard of care and are not absolute requirements; rather they are recommendations that may be adopted, modified, or rejected according to clinical considerations.

Target-controlled versus fractionated propofol sedation in flexible bronchoscopy: A randomized noninferiority trial

BACKGROUND AND OBJECTIVE

Fractionated propofol administration (FPA) in flexible bronchoscopy (FB) may lead to oversedation and an increased risk of adverse events, because a stable plasma concentration of propofol is not maintainable. The purpose of this randomized noninferiority trial was to evaluate whether target-controlled infusion (TCI) of propofol is noninferior to FPA in terms of safety in FB.

METHODS

Coprimary outcomes were the mean lowest arterial oxygen saturation (SpO₂ ) during FB and the number of propofol dose adjustments in relation to procedure duration. Secondary outcomes were the number of occasions with SpO₂  < 90% and/or oxygen desaturations of >4% from baseline, number of occasions with systolic blood pressure < 90 mm Hg, cough frequency, cumulative propofol dose, recovery time, maximum transcutaneous CO₂ , mean SpO₂ and O₂ delivery during FB.

RESULTS

Seventy-seven patients were included. TCI was noninferior to FPA in terms of mean (standard deviation) lowest SpO₂ during the procedure (88.3% (5.4%) vs 86.9% (7.3%)) and required fewer dose adjustments (0.04/min vs 0.28/min, P < 0.001) but a higher cumulative propofol dose (264 vs 194 mg, P = 0.003). All other secondary outcomes were comparable between the groups.

CONCLUSION

We suggest that TCI of propofol is a favourable sedation technique for FB with equal safety issues and fewer dose adjustments compared with FPA.

The median effective concentration (EC50) of propofol with different doses of fentanyl during colonoscopy in elderly patients

BACKGROUND

Propofol and fentanyl are the most widely administered anesthesia maintaining drugs during colonoscopy. In this study, we determined the median effective concentration (EC50) of propofol required for colonoscopy in elderly patients, and the purpose of this study was to describe the pharmacodynamic interaction between fentanyl and propofol when used in combination for colonoscopy in elderly patients.

METHODS

Ninety elderly patients scheduled for colonoscopy were allocated into three groups in a randomized, double-blinded manner as below, F0.5 group (0.5 μg.kg(-1) fentanyl), F1.0 group (1.0 μg.kg(-1) fentanyl) and saline control group. Anaesthesia was achieved by target-controlled infusion of propofol (Marsh model, with an initial plasma concentration of 2.0 μg.ml(-1)) and fentanyl. Colonoscopy was started 3 min after the injection of fentanyl. The EC50 of propofol for colonoscopy with different doses of fentanyl was measured by using an up-and-down sequential method with an adjacent concentration gradient at 0.5 μg.ml(-1) to inhibit purposeful movements. Anaesthesia associated adverse events and recovery characters were also recorded.

RESULTS

The EC50 of propofol for colonoscopy in elderly patients were 2.75 μg.ml(-1) (95% CI, 2.50-3.02 μg.ml(-1)) in F0.5 group, 2.05 μg.ml(-1) (95% CI, 1.98-2.13 μg.ml(-1)) in F1.0 group and 3.08 μg.ml(-1) (95% CI, 2.78-3.42 μg.ml(-1)) in control group respectively (P < 0.05). Patients in the F1.0 group had a significantly longer awake time and length of hospital stay than those in control group (P < 0.05).

CONCLUSION

Increasing doses of fentanyl up to 1.0 μg.kg(-1) reduces the propofol EC50 required for elderly patients undergoing colonoscopy, and there was no significant difference in anaesthesia associated adverse events but prolonged awake and discharge time.

TRIAL REGISTRATION

Chinese Clinical Trial Registry ChiCTR15006368. Date of registration: May 3, 2015.

Pharmacokinetic-pharmacodynamic relationship of anesthetic drugs: from modeling to clinical use

Anesthesia is a combination of unconsciousness, amnesia, and analgesia, expressed in sleeping patients by limited reaction to noxious stimulations. It is achieved by several classes of drugs, acting mainly on central nervous system. Compared to other therapeutic families, the anesthetic drugs, administered by intravenous or pulmonary route, are quickly distributed in the blood and induce in a few minutes effects that are fully reversible within minutes or hours. These effects change in parallel with the concentration of the drug, and the concentration time course of the drug follows with a reasonable precision mathematical models based on the Fick principle. Therefore, understanding concentration time course allows adjusting the dosing delivery scheme in order to control the effects.   The purpose of this short review is to describe the basis of pharmacokinetics and modeling, the concentration-effects relationship, and drug interactions modeling to offer to anesthesiologists and non-anesthesiologists an overview of the rules to follow to optimize anesthetic drug delivery.

Target Controlled Infusion for non-anaesthesiologist propofol sedation during gastrointestinal endoscopy: The first double blind randomized controlled trial

BACKGROUND

Target Controlled Infusion is a sophisticated tool for providing optimal sedation regimen avoiding under or oversedation in gastrointestinal endoscopy.

AIMS

To compare standard moderate sedation vs. non-anaesthesiologist-administered propofol sedation during gastrointestinal endoscopy.

METHODS

Randomized controlled trial of 70 consecutive colonoscopies and 70 consecutive esophagogastroduodenoscopies (EGD). Standard group (n=70), received fentanyl (1 μg/kg)+midazolam (0.03-0.04 mg/kg) or midazolam only; propofol group (n=70), received fentanyl (1 μg/kg)+propofol Target Controlled Infusion (1.2-1.6 μg/ml) or propofol Target Controlled Infusion only. Discharge time, endoscopist satisfaction and patient satisfaction were recorded in all endoscopies.

RESULTS

Colonoscopy: discharge time was significantly shorter in the propofol than the standard group (1.1 ± 0.3 vs. 5 ± 10.2 min, respectively; P=0.03). Endoscopist satisfaction was significantly higher (98.3 ± 11.4/100 vs. 87.2±12/100; P=0.001); patient satisfaction was significantly higher (95 ± 9.3/100 vs. 85.5 ± 14.4/100; P=0.002) in the propofol compared to the standard group. EGD: discharge time was not significantly different in the propofol and standard groups (1.1 ± 0.7 vs. 3.9 ± 9.2 min, respectively; P=0.146). Endoscopist satisfaction was significantly higher (92.7 ± 14.3/100 vs. 82.8 ± 21.2/100; P=0.03); patient satisfaction was significantly higher (93.8 ± 18.2/100 vs. 76.5 ± 25.2/100; P=0.003). In the propofol group 94.3% of patients vs. 71.4% of patients in standard group asked to receive the same sedation in the future (P=0.021).

CONCLUSION

Target Controlled Infusion is a promising method for non-anaesthesiologist-administered propofol sedation.

Total Intravenous Anesthesia-Target Controlled Infusion for colorectal surgery. Remifentanil TCI vs sufentanil TCI

The aim of the study was to compare the effect of remifentanil and sufentanil administered for total intravenous anaesthesia (TIVA) using target-controlled infusion (TCI) on intraoperative hemodynamic response, tracheal intubation and extubation times in patients undergoing colorectal surgery.

METHODS

Sixty patients undergoing open colorectal surgery for colorectal tumors or inflammatory diseases were randomized prospectively into one of two groups: remifentanil group R (n = 30) received TIVA-TCI with propofol and remifentanil and sufentanil group S (n = 30) received TIVA-TCI with propofol and sufentanil. Changes of mean arterial pressure (MAP) and heart rate (HR) were compared during induction and maintenance of anaesthesia. Response to tracheal intubation was assessed as episodes of hypertension, increased HR and bispectral index values, sweating, lacrimation, and coughing. The numbers of target plasma concentration (Cp) adjustments of opioids and propofol due to painful stimulation were recorded during surgery. Recovery time expressed as extubation time was also evaluated.

RESULTS

MAP and HR, expressed as area under the curve (AUC), were not significantly different between groups during anesthesia and surgery. During induction of anesthesia, MAP values decrease from baseline, in both groups (p < 0.001). Intergroup comparison revealed that MAP decreased more in the remifentanil than sufentanil group (p = 0.027). HR decreased from baseline values only in the remifentanil group (p = 0.05). The number of target concentration adjustments for propofol and opioid was higher in the remifentanil group as compared with sufentanil group (p = 0.02 and p = 0.04). Hemodynamic responses to tracheal intubation and extubation times were not significantly different between the groups.

CONCLUSION

Both remifentanil and sufentanil TCI produced stable hemodynamic conditions during open colorectal surgery but sufentanil TCI was associated with less decrease in blood pressure and heart rate, and required fewer dose adjustments during anesthesia induction.

Medical devices for the anesthetist: current perspectives

Anesthesiologists are unique among most physicians in that they routinely use technology and medical devices to carry out their daily activities. Recently, there have been significant advances in medical technology. These advances have increased the number and utility of medical devices available to the anesthesiologist. There is little doubt that these new tools have improved the practice of anesthesia. Monitoring has become more comprehensive and less invasive, airway management has become easier, and placement of central venous catheters and regional nerve blockade has become faster and safer. This review focuses on key medical devices such as cardiovascular monitors, airway equipment, neuromonitoring tools, ultrasound, and target controlled drug delivery software and hardware. This review demonstrates how advances in these areas have improved the safety and efficacy of anesthesia and facilitate its administration. When applicable, indications and contraindications to the use of these novel devices will be explored as well as the controversies surrounding their use.

Individualizing propofol dosage: a multivariate linear model approach

In the last decades propofol became established as an intravenous agent for the induction and maintenance of both sedation and general anesthesia procedures. In order to achieve the desired clinical effects appropriate infusion rate strategies must be designed. Moreover, it is important to avoid or minimize associated side effects namely adverse cardiorespiratory effects and delayed recovery. Nowadays, to attain these purposes the continuous propofol delivery is usually performed through target-controlled infusion (TCI) systems whose algorithms rely on pharmacokinetic and pharmacodynamic models. This work presents statistical models to estimate both the infusion rate and the bolus administration. The modeling strategy relies on multivariate linear models, based on patient characteristics such as age, height, weight and gender along with the desired target concentration. A clinical database collected with a RugLoopII device on 84 patients undergoing ultrasonographic endoscopy under sedation-analgesia with propofol and remifentanil is used to estimate the models (training set with 74 cases) and assess their performance (test set with 10 cases). The results obtained in the test set comprising a broad range of characteristics are satisfactory since the models are able to predict bolus, infusion rates and the effect-site concentrations comparable to those of TCI. Furthermore, comparisons of the effect-site concentrations for dosages predicted by the proposed Linear model and the Marsh model for the same target concentration is achieved using Schnider model and a factorial design on the factors (patients characteristics). The results indicate that the Linear model predicts a dosage profile that is faster in leading to an effect-site concentration closer to the desired target concentration.

The potential regimen of target-controlled infusion of propofol in flexible bronchoscopy sedation: a randomized controlled trial

OBJECTIVES

Target-controlled infusion (TCI) provides precise pharmacokinetic control of propofol concentration in the effect-site (Ce), eg. brain. This pilot study aims to evaluate the feasibility and optimal TCI regimen for flexible bronchoscopy (FB) sedation.

METHODS

After alfentanil bolus, initial induction Ce of propofol was targeted at 2 μg/ml. Patients were randomized into three titration groups (i.e., by 0.5, 0.2 and 0.1 μg/ml, respectively) to maintain stable sedation levels and vital signs. Adverse events, frequency of adjustments, drug doses, and induction and recovery times were recorded.

RESULTS

The study was closed early due to significantly severe hypoxemia events (oxyhemoglobin saturation <70%) in the group titrated at 0.5 μg/ml. Forty-nine, 49 and 46 patients were enrolled into the 3 respective groups before study closure. The proportion of patients with hypoxemia events differed significantly between groups (67.3 vs. 46.9 vs. 41.3%, p = 0.027). Hypotension events, induction and recovery time and propofol doses were not different. The Ce of induction differed significantly between groups (2.4±0.5 vs. 2.1±0.4 vs. 2.1±0.3 μg/ml, p = 0.005) and the Ce of procedures was higher at 0.5 μg/ml titration (2.4±0.5 vs. 2.1±0.4 vs. 2.2±0.3 μg/ml, p = 0.006). The adjustment frequency tended to be higher for titration at 0.1 μg/ml but was not statistically significant (2 (0∼6) vs. 3 (0∼6) vs. 3 (0∼11)). Subgroup analysis revealed 14% of all patients required no further adjustment during the whole sedation. Comparing patients requiring at least one adjustment with those who did not, they were observed to have a shorter induction time (87.6±34.9 vs. 226.9±147.9 sec, p<0.001), a smaller induction dose and Ce (32.5±4.1 vs. 56.8±22.7 mg, p<0.001; 1.76±0.17 vs. 2.28 ±0.41, p<0.001, respectively), and less hypoxemia and hypotension (15.8 vs.56.9%, p = 0.001; 0 vs. 24.1%, p = 0.008, respectively).

CONCLUSION

Titration at 0.5 μg/ml is risky for FB sedation. A subgroup of patients required no more TCI adjustment with fewer complications. Further studies are warranted to determine the optimal regimen of TCI for FB sedation.

TRIAL REGISTRATION

ClinicalTrials.gov NCT01101477.

Design and implementation of a closed-loop control system for infusion of propofol guided by bispectral index (BIS)

BACKGROUND

This study describes the design of a hypnosis closed-loop control system with propofol. The controller used a proportional-integral (PI) algorithm with the bispectral index (BIS) as the feedback signal. Our hypothesis was that a PI closed-loop control could be applied in clinical practice safely keeping the BIS within a pre-determined target range.

METHODS

The adjustment of the PI parameters was based on simulation. The procedure had three steps: obtaining a patient model using data from 12 patients, designing and adjusting the controller in simulation, and fine tuning the PI parameters in a pilot study (10 patients). The resulting controller was tested in 24 American Society of Anesthesiology (ASA) I-II patients. The controller directly decides the infusion rate of propofol, and no model is necessary in its online operation. The BIS target was set to 50. Remifentanil was used for analgesia.

RESULTS

We evaluated the efficiency and safety of the automatic feedback system. It worked properly in all the patients. The median performance error was -1.62, and the median absolute performance error was 11.03. Average propofol-normalized consumption was 5.3 ± 1.8 mg/kg/h. Mean percentage of BIS in the range 40-60 was 83%. Mean time to open eyes was 8 ± 4 min. Time to extubation was 9 ± 5 min. Hemodynamic adverse event or intraoperative awareness were not recorded.

CONCLUSIONS

The closed-loop system was able to maintain the BIS within an acceptable range of levels. The control of a propofol infusion guided by the BIS is feasible without hemodynamic instability in ASA I/II patients.

How best to approach endoscopic sedation?

Sedation is the drug-induced reduction of a patient's consciousness. The aim of sedation in endoscopic procedures is to increase the patient's comfort and to improve endoscopic performance, especially in therapeutic procedures. The most commonly used sedation regimen for conscious sedation in gastrointestinal endoscopy is still the combination of benzodiazepines with opioids. However, the use of propofol has increased enormously in the past decade and several studies show advantages of propofol over the traditional regimes in terms of faster recovery time. It is important to be aware that the complication rate of endoscopies increases when sedation is used; therefore, a thorough risk evaluation before the procedure and monitoring during the procedure must be performed. In addition, properly trained staff and emergency equipment should be available. The best approach to sedation in endoscopy is to choose a sedation regimen for the individual patient, tailored according to the clinical risk assessment and the anxiety level of the patient, as well as to the type of planned endoscopic procedure.

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.

[Manual single infusion of combined remifentanil and propofol for anesthesia during laparoscopic gynecology procedures: a case series]

OBJECTIVE

To describe a single manual infusion technique for total intravenous anesthesia with remifentanil and propofol.

MATERIAL AND METHODS

Descriptive study of a series of 30 women classified as ASA 1 or 2 who received total intravenous anesthesia by means of a single manual infusion of a combination of remifentanil and propofol for laparoscopic gynecology procedures. The patients received 5 microg of remifentanil plus 2 mg of propofol per milliliter of normal saline solution. The rate of infusion was established according to remifentanil requirements and modified in accordance with the bispectral (BIS) index.

RESULTS

Sufficient hemodynamic stability was maintained in all patients, with BIS values between 40 and 60. The average time until awakening was 5.2 minutes after the anesthetic infusion had been halted.

CONCLUSIONS

Total intravenous anesthesia by means of a single manual infusion of remifentanil and propofol provided appropriate anesthetic and surgical conditions, with rapid, predictable awakening.