Anesthesia Delivery System Research Articles

The effectiveness of computerized anesthesia in primary mandibular molar pulpotomy: A randomized controlled trial.

The technique of local anesthetic administration is an important consideration in the behavior guidance of a pediatric patient. The study hypothesized that there is no difference in the pain effectiveness in the experimental subjects with the use of single tooth anesthesia and the controls with the use of conventional technique (traditional inferior alveolar nerve block [IANB]).The purpose of this study was to compare the anesthesia effectiveness of traditional IANB; IANB using a computer-controlled local anesthetic delivery system (CCLAD); and intraligamental anesthesia (ILA) using CCLAD in pulpotomy of the primary mandibular second molars. Ninety-one healthy 5- to 9-year-old children underwent pulpotomy of the mandibular second molars. They were randomly assigned into Group A (traditional IANB), Group B (IANB using CCLAD), or Group C (ILA injection using CCLAD). The effectiveness of anesthesia was measured during different steps of pulpotomy using the sounds, eyes, and motor (SEM) scale. The postoperative complications were recorded after 24 hours. For all five pulpotomy steps, the anesthesia effectiveness was similar among the three anesthesia techniques. Anesthesia effectiveness was not significantly different (based on SEM scores) between the three groups during clamp application, drilling of the tooth, entering the pulp, pulp extirpation, and removal of the clamp (P = .635, P = .996, P = .630, P = .945, and P = .101, respectively). There was no significant difference in postoperative complications between the three groups. The IANB anesthesia using CCLAD and periodontal ligament anesthesia using CCLAD were as effective as traditional IANB in anesthetizing the primary mandibular molars during pulpotomy.

Movement control during aspiration with different injection systems via video monitoring-an in vitro model.

The aim of the present study was an evaluation of movement during double aspiration by different manual syringes and one computer-controlled local anesthesia delivery system (C-CLAD). With five different devices (two disposable syringes (2, 5ml), two aspirating syringes (active, passive), one C-CLAD), simulation of double aspiration in a phantom model was conducted. Two experienced and two inexperienced test persons carried out double aspiration with the injection systems at the right and left phantom mandibles in three different inclination angles (n=24×5×2 for each system). 3D divergences of the needle between aspiration procedures (mm) were measured with two video cameras. An average movement for the 2-ml disposal syringe of 2.85mm (SD 1.63), for the 5ml syringe of 2.36mm (SD 0.86), for the active-aspirating syringe of 2.45mm (SD 0.9), for the passive-aspirating syringe of 2.01mm (SD 0.7), and for the C-CLAD, an average movement of 0.91mm (SD 0.63) was seen. The movement was significantly less for the C-CLAD compared to the other systems (p<0.001). The movement of the needle in the soft tissue was significantly less for the C-CLAD compared to the other systems (p<0.001). A difference in involuntary movement of the syringe could be seen in comparison between manual and C-CLAD systems. Launching the aspiration by a foot pedal in computer-assisted anesthesia leads to a minor movement. To solve the problem of movement during aspiration with possibly increased false-negative results, a C-CLAD seems to be favorable.

Comparison of Pain Perception for Nasopalatine Nerve Block using Conventional and Computerized Local Anesthesia Delivery Systems in Adults: A Randomized Split-mouth Clinical Study

ABSTRACTIntroductionProfound local anesthesia (LA) is necessary in order to reduce patient discomfort during oral surgical procedures. However, injection technique itself may be a potentially painful procedure. A comfortable and consistent LA can increase the level of trust between the patient and the operator, since even a thought of intraoral injection causes a considerable amount of anxiety in many patients. To reduce this anxiety, a computer-controlled local anesthesia delivery (CCLAD) system is commercially available as a possible means of minimizing the sensation of pain (especially for palatal injections).AimThe aim of the present study was to compare the pain perception, when injections were administered using the CCLAD system or a conventional technique in patients requiring oral surgical procedures in the maxillary anterior region.Materials and MethodsThis randomized split-mouth study included 15 patients (7 females and 8 males). Conventional syringe or computerized single tooth anesthesia (STA) system with a 30-gauge needle was used to give nasopalatine nerve block by the same operator, over a minimum gap of 7 days. Immediately after injection, patient's pain perception was assessed using numeric rating scale (NRS). Overall difference in pain perception and effect of change in sequence of type of anesthesia were determined using unpaired t-test.ResultsResults of the study showed statistically significant difference between the pain scores of STA system and conventional injection technique; however, the change in sequence of anesthesia technique did not show any effect on the effectiveness of STA system.ConclusionThe STA system significantly reduces the pain perception after administration of nasopalatine nerve block in adults.Clinical significanceUse of STA system for administration of nasopalatine nerve block in adults provides better patient acceptance and pain control over conventional cartridge syringe.How to cite this articleKohale BR, Agrawal AA, Erlewad D. Comparison of Pain Perception for Nasopalatine Nerve Block using Conventional and Computerized Local Anesthesia Delivery Systems in Adults: A Randomized Split-mouth Clinical Study. J Contemp Dent 2016;6(3):177-180.

A Multicenter Evaluation of a Closed-Loop Anesthesia Delivery System: A Randomized Controlled Trial.

Closed-loop systems for anesthesia delivery have been shown to outperform traditional manual control in different clinical settings. The present trial was aimed at evaluating the feasibility and efficacy of Bispectral Index (BIS)-guided closed-loop anesthesia delivery system (CLADS) in comparison with manual control across multiple centers in India. Adult patients scheduled for major surgical procedures of an expected duration of 1 to 3 hours were randomized across 6 sites into 2 groups: a CLADS group and a manual group. In the manual control group, propofol infusion was titrated manually by the attending anesthesiologist to a BIS of 50 during induction and maintenance. Analgesia was maintained with fentanyl infusion and nitrous oxide in both groups. In the CLADS group, both induction and maintenance of anesthesia were performed automatically using CLADS. The primary outcome measure was the performance of the system as assessed by the percentage of total anesthesia time BIS remained ±10 of target BIS. The secondary outcome measures were a percentage of anesthesia-time heart rate and mean arterial pressure within 25% of the baseline, median absolute performance error, wobble, and global score. Wobble indicates intraindividual variability in the control of BIS, and global score reflects the overall performance; lower values indicate superior performance for both parameters. The performance parameters of the system also were compared among the participating sites. Two hundred forty-two patients were randomized. BIS was maintained within ±10 of target for significantly longer time in the CLADS group (81.4% ± 8.9 % of anesthesia duration) than in the manual group (55.34% ± 25%, P < 0.0001). The indices that assess performance were significantly better in the CLADS group than the manual group as follows: median absolute performance error was 10 (10, 12) (median [interquartile range]) in the CLADS group versus 18 (14, 24) in the manual group, P < 0.0001; wobble was 9 (8, 10) in CLADS group versus 10 (8, 14) in the manual group, P = 0.0009; and Global score, which reflects overall performance, was 24 (19, 30) in the CLADS group versus 51 (31, 99) in the manual group, P < 0.0001. The percentage of time heart rate was within 25% of the baseline was significantly greater in the CLADS group (heart rate of 95 [87, 99], median [interquartile range], in the CLADS group versus 90 [75, 98] in the manual group P = 0.0031). On comparison of data between the centers, the performance parameters did not differ significantly among the centers in the CLADS group (P = 0.94), but the parameters differed significantly among the centers in the manual group (P < 0.001). Our study in a multicenter setting proves the consistently better performance of automated anesthesia drug delivery compared with conventional manual control. This highlights an important advantage of an automated system for delivering standardized anesthesia, thereby overcoming differences in practices among anesthesiologists.

Exhaustion by design

We would like to highlight a problem with the design of the carbon dioxide (CO2) absorber of a Maquet FLOW-i® Anaesthesia Delivery System machine (Maquet Cardiovascular, LLC, Wayne, NJ, USA) that results in elevated inspired CO2 levels. The FLOW-i anaesthesia machine is fitted with a disposable proprietary CO2 absorber canister containing enabling rapid change of an exhausted absorber. Sofnolime™ granules are coated with an indicator that changes from white to purple at exhaustion. During a recent case under general anaesthesia with mechanical ventilation through a circle circuit with a fresh gas flow of 2 l.min−1, the baseline inspired CO2 level was found to be 0.53 kPa, even though only approximately one-third of the Sofnolime granules were visibly exhausted (Fig. 2a). The absorber function was not bypassed and the inspiratory and expiratory valves were working correctly. Attempts to decrease the inspired CO2 levels by gentle knocking of the absorber canister to settle the granules were unsucessful. As the inspired CO2 level continued to rise, we changed the absorber canister and the inspired CO2 fell back to zero. Examination of the CO2 absorber canister revealed uneven exhaustion of the absorber granules preferentially towards the machine-facing aspect of the canister (Fig. 2b), where both the inflow and exit pipe channels are situated (Fig. 2c). We think that there may be preferential airflow between these, leading to the clinical problems and granule exhaustion pattern we found. We invite Maquet to comment on whether they are considering redesign of the inflow/exit channel positions relative to each other, or the incorporation of baffles, to overcome this problem.

Robust control of burst suppression for medical coma

Objective. Medical coma is an anesthetic-induced state of brain inactivation, manifest in the electroencephalogram by burst suppression. Feedback control can be used to regulate burst suppression, however, previous designs have not been robust. Robust control design is critical under real-world operating conditions, subject to substantial pharmacokinetic and pharmacodynamic parameter uncertainty and unpredictable external disturbances. We sought to develop a robust closed-loop anesthesia delivery (CLAD) system to control medical coma. Approach. We developed a robust CLAD system to control the burst suppression probability (BSP). We developed a novel BSP tracking algorithm based on realistic models of propofol pharmacokinetics and pharmacodynamics. We also developed a practical method for estimating patient-specific pharmacodynamics parameters. Finally, we synthesized a robust proportional integral controller. Using a factorial design spanning patient age, mass, height, and gender, we tested whether the system performed within clinically acceptable limits. Throughout all experiments we subjected the system to disturbances, simulating treatment of refractory status epilepticus in a real-world intensive care unit environment. Main results. In 5400 simulations, CLAD behavior remained within specifications. Transient behavior after a step in target BSP from 0.2 to 0.8 exhibited a rise time (the median (min, max)) of 1.4 [1.1, 1.9] min; settling time, 7.8 [4.2, 9.0] min; and percent overshoot of 9.6 [2.3, 10.8]%. Under steady state conditions the CLAD system exhibited a median error of 0.1 [−0.5, 0.9]%; inaccuracy of 1.8 [0.9, 3.4]%; oscillation index of 1.8 [0.9, 3.4]%; and maximum instantaneous propofol dose of 4.3 [2.1, 10.5] mg kg−1. The maximum hourly propofol dose was 4.3 [2.1, 10.3] mg kg−1 h−1. Performance fell within clinically acceptable limits for all measures. Significance. A CLAD system designed using robust control theory achieves clinically acceptable performance in the presence of realistic unmodeled disturbances and in spite of realistic model uncertainty, while maintaining infusion rates within acceptable safety limits.

Effect of paravertebral nerve blocks on narcotic use after mastectomy with reconstruction

IntroductionPain control outcomes using local anesthetic delivery systems vs usual narcotics at our institution revealed that use of local anesthetic delivery systems decreased narcotic use greater than 40% in patients with no reconstruction but had very little effect in patients receiving reconstruction. As part of our quality improvement program, the anesthesiology department trained and began offering paravertebral blocks (PVBs) to patients having reconstruction. We reviewed pain control outcomes to understand how the use of paravertebral nerve blocks affected narcotic use in reconstructed patients. MethodsRetrospective review of prospectively collected data on patients undergoing mastectomy with or without reconstruction in the 6-month period after introduction of PVB analgesia. Patients received preoperative single-shot paravertebral nerve blocks at T2 to T3 and T5 to T6 with bupivacaine .5% and epinephrine 1:200,000 (7.5 mL per injection). Patients who had a bilateral mastectomy with reconstruction received bilateral paravertebral nerve blocks at the same locations. Narcotic doses were converted to morphine equivalents (MSEs) to allow comparison. ResultsThere were 102 patients with mastectomy during that period and 91 were evaluable. Fifty-one had no reconstruction with an average MSE use of 37.9. There were 40 with reconstruction, 33 had PVB with average MSE of 42.6, and 7 patients had reconstruction with no PVB with average MSE of 71.1. There were no major complications. ConclusionsInstitution of the PVB for patients undergoing mastectomy with reconstruction lowered average MSE use. We will continue to offer paravertebral blocks in this cohort of patients.

Comparison of the Pain Perception of Conventional and Computer-controlled Anesthesia Techniques for Extraction of Maxillary First Premolar

ABSTRACT Introduction Anterior middle superior alveolar (AMSA) block is a nerve block technique in conjunction with computer-controlled local anesthetic delivery (CCLAD) system. Anterior middle superior alveolar produces local anesthesia (LA) to the maxillary teeth from second premolar to the central incisor including the hard palate and corresponding soft-tissue of both buccal and palatal side, with single palatal injection. Aim To evaluate efficacy of AMSA block for extraction of maxillary first premolar. Study design In randomized single blind, split mouth clinical trial, the 14 patients received the conventional buccal-palatal (B-P) anesthesia on one side and CCLAD anesthesia AMSA for other side. The treatment consisted of bilateral extraction of maxillary first premolars for orthodontics. Pain perception ratings were obtained by using 10 point visual analog scale (VAS). Results A total of 100% cases had painless injection with CCLAD, whereas 28.57% patients had painless injection experience with conventional LA. In all cases, there was no pain during extraction on both sides. With CCLAD, buccal retraction was painful in four cases whereas palatal retraction was painful in one case. Conclusion Anterior middle superior alveolar block injected with CCLAD is better as LA technique for extraction of maxillary first premolar as compared to B-P approach. How to cite this article Manekar VS. Comparison of the Pain Perception of Conventional and Computer-controlled Anesthesia Techniques for Extraction of Maxillary First Premolar. World J Dent 2015;6(3):150-153.

Behavioral response and pain perception to computer controlled local anesthetic delivery system and cartridge syringe.

The present study evaluated and compared the pain perception, behavioral response, physiological parameters, and the role of topical anesthetic administration during local anesthetic administration with cartridge syringe and computer controlled local anesthetic delivery system (CCLAD). A randomized controlled crossover study was carried out with 120 children aged 7-11 years. They were randomly divided into Group A: Receiving injection with CCLAD during first visit; Group B: Receiving injection with cartridge syringe during first visit. They were further subdivided into three subgroups based on the topical application used: (a) 20% benzocaine; (b) pressure with cotton applicator; (c) no topical application. Pulse rate and blood pressure were recorded before and during injection procedure. Objective evaluation of disruptive behavior and subjective evaluation of pain were done using face legs activity cry consolability scale and modified facial image scale, respectively. The washout period between the two visits was 1-week. Injections with CCLAD produced significantly lesser pain response, disruptive behavior (P < 0.001), and pulse rate (P < 0.05) when compared to cartridge syringe injections. Application of benzocaine produced lesser pain response and disruptive behavior when compared to the other two subgroups, although the result was not significant. Usage of techniques which enhance behavioral response in children like injections with CCLAD can be considered as a possible step toward achieving a pain-free pediatric dental practice.

Cartridge syringe vs computer controlled local anesthetic delivery system: Pain related behaviour over two sequential visits - a randomized controlled trial.

Background Local anesthetic injection is one of the most anxiety provoking procedure in dentistry. Knowledge about change in pain related behaviour during consecutive visits helps in and scheduling of treatment procedures and management of children in dental clinic. Aim To compare the pain perception, behavioural response and the associated change in physiological parameters while receiving local anesthesia injection with cartridge syringe and computer controlled local anesthetic delivery system (CCLAD) over two consecutive visits. Material and Methods In this randomized controlled cross over trial, 120 children aged 7 – 11 years were randomly divided into group A: receiving injections with CCLAD during first visit; group B: receiving injections with cartridge syringe during first visit. The physiological parameters (heart rate and blood pressure) were recorded before and during injection procedure. Objective evaluation of disruptive behaviour and subjective evaluation of pain perceived were done using Face Legs Activity Cry Consolability (FLACC) scale and modified facial image scale (FIS) respectively. Results No statistical difference in pain response (p= 0.164) and disruptive behaviour (p = 0.120) between cartridge syringe and CCLAD injections were seen during the first visit although the latter showed lesser scores. However, during the second visit there were significant increase in pain response (p = 0.004) and disruptive behaviour (p = 0.006) in cartridge syringe group with an associated increase in heart rate. Conclusions Injections with CCLAD produced lesser pain ratings and disruptive behaviour than cartridge syringe in children irrespective of order of visit. Key words:Behaviour, cartridge syringe, CCLAD, local anesthesia.

ALFAXALONE AS AN INTRAMUSCULAR INJECTABLE ANESTHETIC IN KOI CARP (CYPRINUS CARPIO)

Fish are commonly anesthetized with MS-222 (tricaine methanesulfonate), a sodium-channel-blocker used as an immersion anesthetic, but its mechanism of action as a general anesthetic is uncertain. Alfaxalone is a neurosteroid that acts at the GABA(A) receptors. Alfaxalone has been evaluated and was deemed successful as an immersion agent in koi carp. Alfaxalone is an effective intramuscular anesthetic in multiple species. A reliable intramuscular anesthetic in fish would be useful in multiple settings. The purpose of this study was to investigate alfaxalone as an intramuscular injectable anesthetic agent in koi carp (Cyprinus carpio). Eight koi carp were utilized in a crossover design. In each trial, six fish received 1 mg/kg, 5 mg/kg, or 10mg/kg of alfaxalone intramuscularly. They were assessed every 15 min for opercular rate and sedation score. The sedation score was based on a visual scale from 0 to 5, 0 indicating no response and 5 indicating absent righting reflex and anesthesia. Anesthetized koi were placed on a fish anesthesia delivery system (FADS). Time to anesthesia/recovery was recorded and heart rate was recorded every 15 min. Anesthesia was achieved in 0/6, 1/6, and 5/6 fish at 1, 5, and 10 mg/kg, respectively. Duration of anesthesia for one fish at 5 mg/kg was 2 hr. At 10 mg/kg, median anesthesia duration was 6.5 (3-10) hr. At 10 mg/kg, prolonged apnea (2-3 hr) was observed in 3/6 fish, 2/3 died under anesthesia, and 1/3 recovered 10 hr post-injection. Median peak sedation scores were 1.5, 2.5, and 5, at 1, 5, and 10 mg/kg, respectively. A dosage of 10 mg/kg alfaxalone resulted in 33% mortality. The duration of anesthesia and opercular rate were unpredictable. Due to variation in response despite consistent conditions, as well as risk of mortality, intramuscular alfaxalone cannot be recommended for anesthesia in koi carp.

A technique for administering xenon gas anesthesia during surgical procedures in mice.

Carrying out invasive procedures in animals requires the administration of anesthesia. Xenon gas offers advantages as an anesthetic agent compared with other agents, such as its protection of the brain and heart from hypoxia-induced damage. The high cost of xenon gas has limited its use as an anesthetic in animal experiments, however. The authors designed and constructed simple boxes for the induction and maintenance of xenon gas and isoflurane anesthesia in small rodents in order to minimize the amount of xenon gas that is wasted. While using their anesthesia delivery system to anesthetize pregnant mice undergoing caesarean sections, they measured the respiratory rates of the anesthetized mice, the survival of the pups and the percentages of oxygen and carbon dioxide within the system to confirm the system's safety.

Putting it all together: recommendations for improving pain management in plastic surgical procedures-surgical facial rejuvenation.

Postoperative pain is a major concern for patients undergoing facial aesthetic surgery. Aggressive efforts to reduce postoperative pain while avoiding adverse sequelae, such as nausea and vomiting, will result in an improved patient experience. Newer pharmaceuticals, medical devices, and longer-acting local anesthetics offer the potential to reduce pain and enhance patient satisfaction. The purpose of this report is to review the options and apply them to 3 specific facial aesthetic procedures: face-lift, brow lift, and blepharoplasty. Our review investigates methods used for pain control in the surgical facial rejuvenation patient. We highlight those techniques that have been documented efficacy. We share specific methods of pain management for the more common surgical facial rejuvenation procedures that we perform. In an effort to maximize patient comfort, we assess the effectiveness of various devices, technologies, and treatment modalities available for pain control after surgical facial rejuvenation. These include local anesthetics, topical creams, intravenous acetaminophen, perioperative ketorolac, local anesthetic wound catheter delivery systems, liposomal bupivacaine, tarsorrhaphy/frost sutures, postoperative pharmacologic therapeutics, prophylactic steroids, and tricks to eliminate pain with suture removal. Additionally, we summarize the primary investigator's preferred method of pain management for the common surgical facial rejuvenation procedures performed. Recent advances in postoperative pain control can significantly improve the patient's surgical experience. This multimodal therapy includes new pharmaceuticals, longer-acting local anesthetics, and devices designed to minimize postoperative pain. Adoption of these techniques may also reduce the need for narcotics and prevent postoperative adverse sequelae.

Anesthesia Quality and Safety

Anesthesia Quality and Safety

New Gadgets in Local Anesthesia: A review

Local pain management is the most critical aspect of patient care in dentistry. When efforts to achieve local anesthesia are unsuccessful, the resulting stress for both the patient and practitioner can be significant. It is imperative on our part to update our knowledge and skills in using newer alternatives in pain control and management and ways of administering them to increase the comfort level of our patients and resolve the cliched paradigm of Pain and Dentistry are inseparable. The improvements in techniques for local anesthesia are probably the most significant advances that have occurred in dental science. This paper provides an update on comparatively newer gadgets that are less commonly used to deliver local anesthetics. Keywords: Computer controlled local anesthesia delivery system (CCLAD), Intraosseous Injection delivery system, Local anesthesia delivery device, Needle-less injector, Vibrating tactile devices.

Evaluation of closed‐loop anesthesia delivery for propofol anesthesia in pediatric cardiac surgery

The objective of this study was to compare the feasibility of closed-loop anesthesia delivery with manual control of propofol in pediatric patients during cardiac surgery. Forty ASA II-III children, undergoing elective cardiac surgery under cardiopulmonary bypass (CPB) in a tertiary care hospital, were randomized to receive propofol either through a closed-loop anesthesia delivery system (CL group) or through traditional manual control (manual group) to achieve a target BIS of 50. Patients were induced and subsequently maintained with a propofol infusion. The propofol usage and the efficacy of closed-loop system in controlling BIS within ±10 of the target were compared with that of manual control. The maintenance of BIS within ±10 of target and intraoperative hemodynamic stability were similar between the two groups. However, induction dose of propofol was less in the CL group (2.06±0.79mg·kg(-1) ) than the manual group (2.95±1.03mg·kg(-1) ) (P=0.006) with less overshoot of BIS during induction in the closed-loop group (P=0.007). Total propofol used in the off-CPB period was less in the CL group (6.29±2.48mg·kg(-1) h(-1) vs 7.82±2.1mg·kg(-1) h(-1) ) (P=0.037). Phenylephrine use in the pre-CPB period was more in the manual group (16.92±10.92μg·kg(-1) vs 5.79±5.98μg·kg(-1) ) (P=0.014). Manual group required a median of 18 (range 8-29) dose adjustments per hour, while the CL group required none. This study demonstrated the feasibility of closed-loop controlled propofol anesthesia in children, even in challenging procedures such as cardiac surgery. Closed-loop system needs further and larger evaluation to establish its safety and efficacy.

Real-time closed-loop control in a rodent model of medically induced coma using burst suppression.

A medically induced coma is an anesthetic state of profound brain inactivation created to treat status epilepticus and to provide cerebral protection after traumatic brain injuries. The authors hypothesized that a closed-loop anesthetic delivery system could automatically and precisely control the electroencephalogram state of burst suppression and efficiently maintain a medically induced coma. In six rats, the authors implemented a closed-loop anesthetic delivery system for propofol consisting of: a computer-controlled pump infusion, a two-compartment pharmacokinetics model defining propofol's electroencephalogram effects, the burst-suppression probability algorithm to compute in real time from the electroencephalogram the brain's burst-suppression state, an online parameter-estimation procedure and a proportional-integral controller. In the control experiment each rat was randomly assigned to one of the six burst-suppression probability target trajectories constructed by permuting the burst-suppression probability levels of 0.4, 0.65, and 0.9 with linear transitions between levels. In each animal the controller maintained approximately 60 min of tight, real-time control of burst suppression by tracking each burst-suppression probability target level for 15 min and two between-level transitions for 5-10 min. The posterior probability that the closed-loop anesthetic delivery system was reliable across all levels was 0.94 (95% CI, 0.77-1.00; n = 18) and that the system was accurate across all levels was 1.00 (95% CI, 0.84-1.00; n = 18). The findings of this study establish the feasibility of using a closed-loop anesthetic delivery systems to achieve in real time reliable and accurate control of burst suppression in rodents and suggest a paradigm to precisely control medically induced coma in patients.

A closed-loop anesthetic delivery system for real-time control of burst suppression

Objective. There is growing interest in using closed-loop anesthetic delivery (CLAD) systems to automate control of brain states (sedation, unconsciousness and antinociception) in patients receiving anesthesia care. The accuracy and reliability of these systems can be improved by using as control signals electroencephalogram (EEG) markers for which the neurophysiological links to the anesthetic-induced brain states are well established. Burst suppression, in which bursts of electrical activity alternate with periods of quiescence or suppression, is a well-known, readily discernible EEG marker of profound brain inactivation and unconsciousness. This pattern is commonly maintained when anesthetics are administered to produce a medically-induced coma for cerebral protection in patients suffering from brain injuries or to arrest brain activity in patients having uncontrollable seizures. Although the coma may be required for several hours or days, drug infusion rates are managed inefficiently by manual adjustment. Our objective is to design a CLAD system for burst suppression control to automate management of medically-induced coma. Approach. We establish a CLAD system to control burst suppression consisting of: a two-dimensional linear system model relating the anesthetic brain level to the EEG dynamics; a new control signal, the burst suppression probability (BSP) defining the instantaneous probability of suppression; the BSP filter, a state-space algorithm to estimate the BSP from EEG recordings; a proportional–integral controller; and a system identification procedure to estimate the model and controller parameters. Main results. We demonstrate reliable performance of our system in simulation studies of burst suppression control using both propofol and etomidate in rodent experiments based on Vijn and Sneyd, and in human experiments based on the Schnider pharmacokinetic model for propofol. Using propofol, we further demonstrate that our control system reliably tracks changing target levels of burst suppression in simulated human subjects across different epidemiological profiles. Significance. Our results give new insights into CLAD system design and suggest a control-theory framework to automate second-to-second control of burst suppression for management of medically-induced coma.

A plea for an independent holistic anaesthesia delivery system

A plea for an independent holistic anaesthesia delivery system

Pain-related behaviour in children: a randomised study during two sequential dental visits

To determine the difference in pain- and distress-related behaviour in children between two consecutive dental treatment sessions using a computer-controlled local anaesthetic delivery system, with dental anxiety as co-variable. A randomised prospective study over two sequential visits in three paediatric dental practices. For both visits 112 young, healthy children needing dental treatment were randomly assigned to either the use of the Wand(®) or the Sleeper One(®). All statistical analyses were performed using SPSS 17. A significance level of p<0.01 was used, correcting for conducting a high number of tests. Children showed significantly more muscle tension, more verbal protest, and more crying or screaming during the second treatment. Sequential dental treatments seem to have a conditioning effect. It is important to know the level of dental anxiety to adjust the treatment sequence to the needs of the child.