Precision and bias of target controlled propofol infusion for sedation † †Presented in abstract format at the World Congress of Anaesthesiology, Paris, 2004

Propofol Target-Controlled Infusion in Emergency Department Sedation (ProTEDS): a multicentre, single-arm feasibility study

BACKGROUND

Procedural sedation is a core skill of the emergency physician. Bolus administration of propofol is widely used in UK EDs. Titrated to an end point of sedation, it has a rapid effect but has been associated with adverse incidents. The use of a target-controlled infusion (TCI) of propofol is not routine but may reduce the incidence of adverse incidents.The primary aims of this single-arm feasibility study were patient satisfaction and to establish recruitment rates for a randomised controlled trial comparing propofol TCI to bolus administration.

METHODS

Four EDs in Scotland, UK, participated. Patients aged 18-65 years, with anterior shoulder dislocation, weight ≥ 50kg, fasted ≥ 90 min were screened. Patients underwent reduction of their dislocated shoulder using TCI propofol. The primary end point was patient satisfaction recorded on a Visual Analogue Scale.

RESULTS

Between 3 April 2017 and 31 December 2018, 25 patients were recruited with a recruitment rate of 20% for the 16-month recruitment window, with a temporary pause to allow amendment of drug dosage.Two patients were excluded. Twenty achieved adequate sedation, defined as a Modified Observer's Assessment of Alertness/Sedation Scale (OAA/S) 3. Successful reduction was achieved in all adequately sedated. Patient satisfaction was documented in 14 patients, mean±SD of 97±9 and time to sedation was 25±8 min. No adverse events were recorded using the Society of Intravenous Anaesthesia adverse event reporting tool.

CONCLUSION

Propofol TCI was acceptable as a method of procedural sedation for patients. The lower than expected recruitment rates highlight the need for dedicated research support.

TRIAL REGISTRATION NUMBER

NCT03442803.

A study protocol for a feasibility study: Propofol Target-Controlled Infusion in Emergency Department Sedation (ProTEDS)-a multi-centre feasibility study protocol

Background

Procedural sedation is a core skill of the emergency physician. Bolus administration of propofol is widely utilised in UK emergency departments to provide procedural sedation. Bolus administration of propofol, titrated to an endpoint of sedation, has a rapid effect but can easily result in apnoea and loss of airway patency. The use of a target-controlled infusion of propofol allows for controlled titration to an effect site concentration and may reduce the rate of adverse incidents. Target-controlled infusion of propofol is not currently used in emergency departments.The primary aim of this feasibility study is to ensure that propofol target-controlled infusion (TCI) is acceptable to the patient and that recruitment rates are adequate to power a randomised controlled trial comparing propofol target-controlled infusion versus bolus administration.

Methods

This study will recruit in four emergency departments in Scotland, UK. Patients aged 18-65 years with anterior shoulder dislocation, weighing ≥ 50 kg and fasted ≥ 90 min, will be screened. Recruited patients will undergo emergency reduction of a dislocated shoulder facilitated by procedural sedation utilising TCI of propofol.The widespread adoption of TCI propofol by emergency departments will require evidence that it is safe, potentially effective, patient centred and a timely method of providing procedural sedation. The primary endpoint will be acceptability measured by patient satisfaction. The secondary endpoints will include incidence and severity of adverse events, number of shoulder reduction attempts, nursing opinion of patient experience, patient's reported pain score and time from commencement of TCI propofol sedation to desired sedation level.The study will be open for recruitment from April 2017 to December 2018.

Discussion

If the study demonstrates patient acceptability with adequate recruitment, we will be in a position to determine the feasibility of progression to a randomised controlled clinical trial of TCI compared to bolus administration of propofol.

Trial registration

ClinicalTrials.gov Identifier: NCT03442803. Registered retrospectively on 22 February 2018.

Propofol target-controlled infusion for sedated gastrointestinal endoscopy: A comparison of propofol alone versus propofol-fentanyl-midazolam

Gastrointestinal (GI) endoscopy is the major technique for diagnosis of GI disease and treatment. Various sedation and analgesia regimens such as midazolam, fentanyl, and propofol can be used during GI endoscopy. The purpose of the study was to compare propofol alone and propofol combination with midazolam and fentanyl in moderate sedation for GI endoscopy. One hundred patients undergoing GI endoscopy were enrolled in this study. All patients received a propofol target-controlled infusion (TCI) to maintain sedation during the procedure. Patients were randomly allocated into either Group P (propofol TCI alone) or Group C (combination of propofol TCI plus midazolam and fentanyl). Dermographic data, anesthetic parameters (sedation regimen, blood pressure, heart rate, and oxygen saturation), procedure parameters (procedure time, colonoscopy, or panendoscopy), propofol consumption, and adverse events (hypoxia, hypotension, and bradycardia) were all recorded. Postprocedural records included recovery time, postoperative adverse events (nausea, vomiting, dizziness, recall, and pain) and satisfaction. The average propofol consumption was 251 ± 83 mg in Group P and 159 ± 73 mg in Group C (p < 0.001). The incidence of transient hypotension was higher in Group P (p = 0.009). The recovery time and discharge time were both shorter in Group C (p < 0.001 and p = 0.006 respectively). Overall, postprocedural adverse events were similar in both groups. The postanesthetic satisfaction was comparable in both groups. TCI of propofol combined with midazolam and fentanyl achieved sedation with fewer hypotension episodes and shorter recovery and discharge time than propofol TCI alone in patients undergoing GI endoscopy.

Effects of mild to moderate sedation on saccadic eye movements

Sedatives alter the metrics of saccadic eye movements. If these effects are nonspecific consequences of sedation, like drowsiness and loss of attention to the task, or differ between sedatives is still unresolved. A placebo-controlled multi-step infusion of one of three sedatives, propofol or midazolam, both GABA-A agonists, or dexmedetedomidine, an α2-adrenergic agonist, was adopted to compare the effects of these three drugs in exactly the same experimental conditions. 60 healthy human volunteers, randomly divided in 4 groups, participated in the study. Each infusion step, delivered by a computer-controlled infusion pump, lasted 20min. During the last 10min of each step, the subject executed a saccadic task. Target concentration was doubled at each step. This block was repeated until the subject was too sedated to continue or for a maximum of 6 blocks. Subjects were unaware which infusion they were receiving. A video eye tracker was used to record the movements of the right eye. Saccadic parameters were modeled as a function of block number, estimated sedative plasma concentration, and subjective evaluation of sedation. Propofol and midazolam had strong effects on the dynamics and latency of the saccades. Midazolam, and to a less extent, propofol, caused saccades to become increasingly hypometric. Dexmedetedomidine had less impact on saccadic metrics and presented no changes in saccadic gain. Suppression of the sympathetic system associated with dexmedetomidine has different effects on eye movements from the increased activity of the inhibitory GABA-A receptors by propofol and midazolam even when the subjects reported similar sedation level.

Low effect-site concentration of propofol target-controlled infusion reduces the risk of hypotension during endoscopy in a Taiwanese population

OBJECTIVE

Target-controlled infusion (TCI) of propofol is an effective way of delivering propofol during endoscopy. However, the ideal effect-site concentration (Ce) of propofol has not yet been defined in an Asian population. This study aimed to determine the ideal Ce of propofol in painless gastrointestinal endoscopy in a Taiwanese population.

METHODS

A total of 121 consecutive patients undergoing diagnostic endoscopy were recruited for this study. The endoscopic procedure was carried out within 1 h. TCI of propofol was utilized during the procedure. All patients received the same regimen to induce conscious sedation, including a bolus of midazolam (0.04 mg/kg) and fentanyl (0.5 μg/kg). The Ce of propofol was calculated using the Schneider model. Patients were randomly assigned to either the low Ce group (1.5-2.5 μg/mL) or high Ce group (3.0-4.0 μg/mL). Their cardiovascular and respiratory events were monitored during the procedure and the patients' post-procedure satisfaction was evaluated.

RESULTS

The mean requirement for propofol was 232.02 mg in the low Ce group and 329.56 mg in the high Ce group, respectively (P < 0.0001). No unexpected event was observed in either group. However, more episodes of hypotension were observed in the high Ce group (P = 0.026). The post-procedure satisfaction rate between the two groups was comparable.

CONCLUSION

A low Ce of propofol TCI (1.5-2.5 μg/mL) achieved adequate anesthesia, reduced the risk of hypotension, and attained a high satisfaction rate in a Taiwanese population undergoing diagnostic painless endoscopy.

Dental sedation for patients with intellectual disability: a prospective study of manual control versus Bispectral Index-guided target-controlled infusion of propofol

STUDY OBJECTIVE

To investigate the use of propofol sedation using Bispectral Index (BIS)-guided target-controlled infusion (TCI) in dental patients with intellectual disability.

DESIGN

Single-center, prospective, randomized clinical trial.

SETTING

Academic outpatient clinic.

SUBJECTS

40 ASA physical status 1 and 2 patients with intellectual disability.

INTERVENTIONS

Patients were randomized to two groups. The manual control (MC) group (n = 20) had sedation by manually controlled infusion of propofol without a BIS index monitor. The BIS-TCI group (n = 20) had sedation by BIS-guided TCI of propofol.

MEASUREMENTS

The required dose of propofol, recovery time for the eyelash reflex, and spontaneous eye opening times were recorded.

MAIN RESULTS

BIS-TCI significantly reduced the dose of propofol and shortened the recovery times for eyelash reflex and spontaneous eye opening.

CONCLUSION

Propofol sedation using BIS-guided TCI is a useful and safe method in the management of patients with intellectual disability.

Electrochemical quantification of 2,6-diisopropylphenol (propofol)

2,6-Diisopropylphenol (propofol) is a potent anesthetic drug with fast onset of the anesthetic effect and short recovery time for the patients. Outside of the United States, propofol is widely used in performing target controlled infusion anesthesia. With the long term vision of an electrochemical sensor for in vivo monitoring and feedback controlled dosing of propofol in blood, different alternatives for the electrochemical quantification of propofol using diverse working electrodes and experimental conditions are presented in this contribution. When the electrochemical oxidation of propofol takes place on a glassy carbon working electrode, an electrochemically active film grows on the electrode surface. The reduction current of the film is proportional to the propofol concentration and the accumulation time. Based on these findings a stripping analytical method was developed for the detection of propofol in acidic solutions between 0 and 30 μM, with a detection limit of 5.5±0.4 μM. By restricting the scanned potential window between 0.5 V and 1.0 V in cyclic voltammetric experiments, the formation of the electrochemically active polymer can be prevented. This allowed the development of a direct voltammetric method for assessing propofol in acidic solutions between 0 and 30 μM, with a 3.2±0.1 μM (n=3) detection limit. The stripping method has a better sensitivity but somewhat worse reproducibility because the electrode surface has to be renewed between each experiment. The direct method does not require the renewal of the electrode surface between measurements but has no adequate selectivity towards the common interfering compounds.

Optimal sedation for gastrointestinal endoscopy: review and recommendations

Sedation practices for endoscopy vary widely. The present review focuses on the commonly used regimens in endoscopic sedation and the associated risks and benefits together with the appropriate safety measures and monitoring practices. In addition, alternatives and additions to intravenous sedation are discussed. Personnel requirements for endoscopic sedation are reviewed; there is evidence presented to indicate that non-anesthetists can administer sedative drugs, including propofol, safely and efficaciously in selected cases. The development of endoscopic sedation as a multi-disciplinary field is highlighted with the formation of the Australian Tripartite Endoscopy Sedation Committee. This comprises representatives of the Australian and New Zealand College of Anaesthetists, the Gastroenterological Society of Australia and the Royal Australasian College of Surgeons. Possible future directions in this area are also briefly summarized.

Auditory evoked potentials for monitoring during anaesthesia: a study of data quality

The auditory evoked potential termed the middle latency response (MLR) has been suggested as an indicator of adequacy of anaesthesia during surgery. However, the response is small and must be extracted from high levels of background noise. A key consideration in using the MLR for clinical monitoring is whether data quality is sufficient to detect small changes. The aim of this study was to investigate the quality of the MLR recorded during anaesthesia, as a rigorous analysis of data quality is lacking in many studies. MLR recordings from patients sedated in intensive care after cardiac surgery were compared to recordings from a reference group of young volunteers with normal hearing. Data quality was measured with the F(sp) parameter. A bootstrap analysis was used to measure statistical response presence and to detect within-subject changes during clinical anaesthesia. Noise levels were high in the normative group probably due to myogenic and EEG activity. With 5 Hz click stimulation, MLR presence in the normative group was below 30%. Response presence improved using stimulation paradigms with chirps or maximum length sequences and reached 100% with a combination of maximum length sequences and chirps. F(sp) values generally improved during anaesthesia as noise levels reduced and MLR presence was 100% for MLS click stimulation. Changes in the MLR amplitude with propofol infusion rate were small. Some within-subject changes in MLR amplitude were detected using the bootstrap analysis, but 100% detection was not possible.

CONCLUSION

Obtaining good quality MLR data in awake subjects is challenging. Data quality improves during clinical anaesthesia and with advanced stimulation methods, but reliable detection of changes in the MLR for clinical monitoring remains a challenge.

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

BACKGROUND

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

METHODS

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

RESULTS

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

CONCLUSION

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

Future directions in endoscopic sedation

The role of sedation in endoscopic procedures has increased and so has the demand for advances in its administration. The pursuit of new agents or administration techniques and their study specific to endoscopic nonsurgical procedures is necessary to improve patient comfort and safety.The science of moderate and deep sedation specific to endoscopy is fledgling but approaching new horizons.

Effect site concentration during propofol TCI sedation: a comparison of sedation score with two pharmacokinetic models

Target controlled infusion (TCI) pumps function using a programme based on a pharmacokinetic/pharmacodynamic model. We compared the Marsh and Schnider models to find out which better correlates with the clinically observed effect of propofol as assessed by the Observer Assessment of Alertness/Sedation (OAAS) score and the Bispectral index. We assessed the sedation score and Bispectral index score in 40 un-premedicated patients undergoing surgical procedures under spinal anaesthesia with propofol sedation to a target concentration of 2 microg.ml(-1). Half of the patients received TCI propofol driven by the Schnider model in effect site control, the other half were sedated with TCI propofol driven by the Marsh model in plasma control. We calculated the effect site concentration predicted by both models for all the patients. Changes in the sedation score and Bispectral index correlated better with the Marsh than with the Schnider effect site prediction in both study groups.

Propofol for sedation in neuro-intensive care

Interventions in the intensive care unit often require that the patient be sedated. Propofol is a widely used, potent sedative agent that is popular in critical care and operating room settings. In addition to its sedative qualities, propofol has neurovascular, neuroprotective, and electroencephalographical effects that are salutory in the patient in neurocritical care. However, the 15-year experience with this agent has not been entirely unbesmirched by controversy: propofol also has important adverse effects that must be carefully considered. This article discusses and reviews the pharmacology of propofol, with specific emphasis on its use as a sedative in the neuro-intensive care unit. A detailed explanation of central nervous system and cardiovascular mechanisms is presented. Additionally, the article reviews the literature specifically pertaining to neurocritical care use of propofol.

Application of physiology-based pharmacokinetic and pharmacodynamic modeling to individualized target-controlled propofol infusions

This study compared the ability of the physiology-based pharmacokinetic (PBPK) model with that of compartmental models used in propofol infusion devices to predict the pharmacokinetics and pharmacodynamics of propofol in various patient groups (children, pregnant women, young men, normal weight adults, and obese adults). With a PBPK model, loss of consciousness (LOC) and recovery of consciousness (ROC) corresponded to a narrow range of brain tissue concentrations (2.2-4.0 mg/L). With the compartmental models, predicted effect concentrations were also within a narrow range at LOC, but were outside the range at ROC. In individuals of normal weight, coefficients of variation (CV) of the predicted brain or effect concentrations at LOC were in a similar range-between 18% and 32%. In obese individuals, however, interindividual CV values for brain or effect concentrations were 41% (PBPK) and 93% (compartmental). This comparison suggests the increased flexibility of PBPK models over compartmental models, the latter of which rely heavily on the patient group from which the model was derived. The incorporation of PBPK models may provide target-controlled infusions with enhanced ability to predict response in a wide variety of patients.