Comparison of success rates, learning curves, and inter-subject performance variability of robot-assisted and manual ultrasound-guided nerve block needle guidance in simulation.

BACKGROUND: This study focuses on a recently developed robotic nerve block system and its impact on learning regional anaesthesia skills. We compared success rates, learning curves, performance times, and inter-subject performance variability of robot-assisted vs manual ultrasound (US)-guided nerve block needle guidance. The hypothesis of this study is that robot assistance will result in faster skill acquisition than manual needle guidance. METHODS: Five co-authors with different experience with nerve blocks and the robotic system performed both manual and robot-assisted, US-guided nerve blocks on two different nerves of a nerve phantom. Ten trials were performed for each of the four procedures. Time taken to move from a shared starting position till the needle was inserted into the target nerve was defined as the performance time. A successful block was defined as the insertion of the needle into the target nerve. Average performance times were compared using analysis of variance. P<0.05 was considered significant. Data presented as mean (standard deviation). RESULTS: All blocks were successful. There were significant differences in performance times between co-authors to perform the manual blocks, either superficial (P=0.001) or profound (P=0.0001); no statistical difference between co-authors was noted for the robot-assisted blocks. Linear regression indicated that the average decrease in time between consecutive trials for robot-assisted blocks of 1.8 (1.6) s was significantly (P=0.007) greater than the decrease for manual blocks of 0.3 (0.3) s. CONCLUSIONS: Robot assistance of nerve blocks allows for faster learning of needle guidance over manual positioning and reduces inter-subject performance variability.

Transcontinental anaesthesia: a pilot study.

BACKGROUND: Although telemedicine is one of the key initiatives of the World Health Organization, no study has explored the feasibility and efficacy of teleanaesthesia. This bi-centre pilot study investigates the feasibility of transcontinental anaesthesia. METHODS: Twenty patients aged ≥ 18 yr undergoing elective thyroid surgery for ≥ 30 min were enrolled in this study. The remote and local set-up was composed of a master-computer (Montreal) and a slave-computer (Pisa). Standard Internet connection, remote desktop control, and video conference software were used. All patients received total i.v. anaesthesia controlled remotely (Montreal). The main outcomes were feasibility, clinical performance, and controller performance of transcontinental anaesthesia. The clinical performance of hypnosis control was the efficacy to maintain bispectral index (BIS) at 45: 'excellent', 'good', 'poor', and 'inadequate' control represented BIS values within 10, from 11 to 20, from 21 to 30, or >30% from target. The clinical performance of analgesia was the efficacy to maintain Analgoscore values at 0 (-9 to 9); -3 to +3 representing 'excellent' pain control, -3 to -6 and +3 to +6 representing 'good' pain control, and -6 to -9 and +6 to +9 representing 'insufficient' pain control. The controller performance was evaluated using Varvel parameters. RESULTS: Transcontinental anaesthesia was successful in all 20 consecutive patients. The clinical performance of hypnosis showed an 'excellent and good' control for 69% of maintenance time, and the controller performance showed an average global performance index of 57. The clinical performance of analgesia was 'excellent and good' for 92% of maintenance time, and the controller performance showed a global performance index of 1118. CONCLUSIONS: Transcontinental anaesthesia is feasible; control of anaesthesia shows good performance indexes. Clinical registration number NCT01331096.

Evaluation of a novel closed-loop total intravenous anaesthesia drug delivery system: a randomized controlled trial.

BACKGROUND: We have developed an automatic anaesthesia system for closed-loop administration of anaesthesia drugs. The control variables used were bispectral index (BIS) and Analgoscore for hypnosis and antinociception, respectively. METHODS: One hundred and eighty-six patients were randomly enrolled in two groups. Propofol, remifentanil, and rocuronium were administered using closed-loop feedback control (closed-loop, n = 93) or manually (control group, n = 93). The clinical performance of hypnosis control was determined by calculating the offset from a BIS of 45: 'excellent', 'good', 'poor', and 'inadequate' control was defined as BIS values within 10%, from 11% to 20%, from 21% to 30%, or >30% offset from the target. The clinical performance of analgesia was defined as the offset from Analgoscore values. Data presented as mean (standard deviation) (95% confidence interval). RESULTS: Excellent or good control of hypnosis was achieved significantly longer in the closed-loop group [47.0 (9.8%) (45.0/49.0), 34.4 (4.7%) (33.5/35.4)] than in the control group [37.3 (14.3%) (34.4/40.2) and 32.3 (7.6%) (30.7/33.7)], respectively (P<0.0001 and 0.0085). Poor and inadequate control of hypnosis was significantly shorter in the closed-loop group [10.8 (5.0%) (9.8/11.8) and 7.7 (6.2%) (6.4/9.0)] than in the control group [14.7 (6.8%) (13.3/16.0) and 15.8 (14.7%) (12.8/18.8)], respectively (P<0.0001). Excellent control of analgesia was achieved significantly longer in the closed-loop group [78.7 (16.2%) (75.4/82.0)] than in the control group [73.7 (17.8%) (70.1/77.3)] (P=0.0456). CONCLUSIONS: The closed-loop system was better at maintaining BIS and Analgoscore than manual administration.

First robotic tracheal intubations in humans using the Kepler intubation system.

BACKGROUND: Intubation is one of the most important anaesthetic skills. We developed a robotic intubation system (Kepler intubation system, KIS) for oral tracheal intubation. METHODS: In this pilot study, 12 patients were enrolled after approval of the local Ethics board and written informed consent. The KIS consists of four main components: a ThrustMaster T.Flight Hotas X joystick (Guillemot Inc., New York, NY, USA), a JACO robotic arm (Kinova Rehab, Montreal, QC, Canada), a Pentax AWS video laryngoscope (Ambu A/S, Ballerup, Denmark), and a software control system. The joystick allows simulation of the wrist or arm movements of a human operator. The success rate of intubation and intubation times were measured. RESULTS: Eleven men and one woman aged 66 yr were included in this study. Intubation was successful in all but one patient using KIS at a total time of [median (inter-quartile range; range)] 93 (87, 109; 76, 153) s; in one patient, fogging of the video laryngoscope prevented intubation using KIS. CONCLUSIONS: We present the first human testing of a robotic intubation system for oral tracheal intubation. The success rate was high at 91%. Future studies are needed to assess the performance and safety of such a system.

Reduced cerebral oxygen saturation during thoracic surgery predicts early postoperative cognitive dysfunction.

BACKGROUND: The objective of this prospective study is to determine cognitive dysfunction after thoracic surgery. METHODS: Seventy-six patients undergoing thoracic surgery with single-lung ventilation (SLV) of an expected duration of >45 min were enrolled. Monitoring consisted of standard clinical parameters and absolute oximetry (S(ct)O(2)). The Mini-Mental State Exam (MMSE) test was used to assess cognitive function before operation and at 3 and 24 h after operation. Data were analysed using Spearman correlation test; risks for cognitive dysfunction were expressed as odds ratios. P<0.05 and data are presented as median (interquartile range). RESULTS: One patient was excluded from the study. S(ct)O(2) during SLV decreased to critical values of <65%, 60%, and 55% in 40 (53%), 15 (20%), and 5 patients (7%), respectively. Twenty-two patients (29%) had a decrease of MMSE>2 points 3 h after surgery, eight patients (10%) had a decrease of MMSE>2 points 24 h after surgery. Postoperative cognitive dysfunction correlated at r(2)=0.272, 0.285, 0.297 with patient exposure times to S(ct)O(2)<65% (P=0.018), <60% (P=0.013), <55% (P=0.010), respectively. The odds ratios of developing early cognitive dysfunction ranged from 2.03 (95% CI: 0.74-5.59) for a short (<5 min) exposure to S(ct)O(2)<65% to a maximum of 9.56 (95% CI: 1.75-52.13) when S(ct)O(2) was <60% for more than 30 min. CONCLUSIONS: Early cognitive dysfunction after thoracic surgery with SLV is positively related to intraoperative decline of S(ct)O(2).

Reduced cerebral oxygen saturation measured by absolute cerebral oximetry during thoracic surgery correlates with postoperative complications.

BACKGROUND: Regional cerebral oxygen saturation (S(ct)O(2)) has recently been shown to decrease significantly during thoracic surgery. The present study investigates whether these desaturations are related to postoperative complications. METHODS: Fifty patients undergoing thoracic surgery with a single-lung ventilation (SLV) of >45 min duration were enrolled. Regional cerebral oxygen saturation was measured using absolute oximetry; standard clinical variables, and SOFA and Clavien scores were recorded. Correlation between minimum S(ct)O(2) during SLV and postoperative complication scores was analysed using Pearson's correlation test, chi(2) test, and logistic regression. RESULTS: Forty-seven patients underwent lobectomy, two patients a pneumonectomy and 1 patient a chest wall resection. Eighty-two per cent of the patients had a decrease in S(ct)O(2) of >15% from baseline value, and 10% of the patients had a minimal absolute S(ct)O(2) value between 45% and 55%. The minimal absolute S(ct)O(2) values during SLV correlated with the Clavien score (R(2)=0.098, P=0.0201) and the non-respiratory SOFA score (R(2)=0.090, P=0.0287). By defining a threshold of S(ct)O(2)=65%, the odds ratio of having a non-respiratory organ failure was 2.37 (95% CI 1.18-4.39, P=0.043) and a complication according to the Clavien score (Clavien score >0) was 3.19 (95% CI 1.60-6.34, P=0.0272). CONCLUSIONS: Thoracic surgery with SLV seemed to be associated with a significant decrease in S(ct)O(2), and minimal S(ct)O(2) values correlated positively with postoperative complications.

Comparison of four different display designs of a novel anaesthetic monitoring system, the 'integrated monitor of anaesthesia (IMA)'.

BACKGROUND: A novel monitoring system (integrated monitor of anaesthesia, IMA) which integrates three components of general anaesthesia on one single display was developed. The focus of this study was to evaluate the performance and user-friendliness of four different display designs. METHODS: Four interface displays of the IMA were developed, including one numerical, one numerical and graphical (mixed numerical-graphical), one only graphical, and one an advanced two-dimensional graphical display. Each of the four displays was evaluated in a random order by 10 staff anaesthetists and 10 residents/fellows using a set of five scenarios. Scenarios involved one or more abnormal variables that participants had to verbally phrase. For each interface test, reaction time, response accuracy, and NASA-Task Load Index were measured and compared. RESULTS: The numerical, graphical, and advanced-graphical interfaces yielded similar median reaction times, respectively, 7.99 s (5.15-10.79), 8.21 s (6.20-11.88), and 9.43 s (6.19-13.3). Reaction times were significantly shorter (P<0.006) with the mixed numerical-graphical interface: 6.26 s (4.52-8.32). The correct response rate was significantly lower in the graphical interface. The three others presented no statistical difference when compared among each other. The mixed numerical-graphical interface yielded a significantly lower NASA-TLX than the numerical and the advanced-graphical interfaces (19/100 vs 34/100, P<0.003). CONCLUSIONS: A mixed numerical-graphical display design appears to present the best results in terms of user reaction times, response accuracy, and performance index when detecting abnormal critical events.

Significant decrease of cerebral oxygen saturation during single-lung ventilation measured using absolute oximetry.

BACKGROUND: Single-lung ventilation (SLV) during thoracic surgery causes important cardiopulmonary disturbances. Absolute cerebral oximetry was used to determine the incidence and magnitude of the decrease in cerebral oxygen saturation (Sct(o(2))) in patients undergoing SLV during thoracic surgery. METHODS: Data were obtained from 20 consecutive patients undergoing thoracic surgery and necessitating SLV of more than 1 h. The FORESIGHTtrade mark (CASMED, USA) absolute oximeter was used to measure left, right, and average absolute Sct(o(2)) every 5 min from the awake state to extubation. Bispectral index and standard monitoring parameters were also recorded every 5 min. Blood gas analysis was performed every 15 min. Data median (IQR) (range) were analysed using repeated-measures anova and Spearman's correlation test, P<0.05. RESULTS: Patients [median age 65 yr (range 46-75)] showed an absolute Sct(o(2)) of 80% (78, 82) (74-87) in the awake state, which decreased to a minimum Sct(o(2)) value of 63% (57, 65) (53-73) during SLV to recover to an Sct(o(2)) of 71% immediately after extubation. During SLV, all patients had a decrease of more than 15% of the initial Sct(o(2)) and 70% of patients had a decrease of more than 20%. The decrease in Sct(o(2)) was not correlated with any standard clinical parameters, for example, arterial pressure, blood loss, peripheral oxygen saturation, or Pa(o(2)). CONCLUSIONS: Thoracic surgery with SLV seems to be associated with a significant decrease of Sct(o(2)) in the majority of patients. Parameters such as peripheral oxygen saturation or Po(2) which are used to guide SLV during thoracic surgery are not sufficient to detect significant cerebral oxygen desaturations.

Heat transfer coefficient: Medivance Arctic Sun Temperature Management System vs. water immersion.

BACKGROUND AND OBJECTIVE: To improve heat transfer, the Medivance Arctic Sun Temperature Management System (Medivance, Inc., Louisville, CO, USA) features an adhesive, water-conditioned, highly conductive hydrogel pad for intimate skin contact. This study measured and compared the heat transfer coefficient (h), i.e. heat transfer efficiency, of this pad (hPAD), in a heated model and in nine volunteers' thighs; and of 10 degrees C water (hWATER) in 33 head-out immersions by 11 volunteers. METHODS: Volunteer studies had ethical approval and written informed consent. Calibrated heat flux transducers measured heat flux (W m-2). Temperature gradient (DeltaT) was measured between skin and pad or water temperatures. Temperature gradient was changed through the pad's water temperature controller or by skin cooling on immersion. RESULTS: The heat transfer coefficient is the slope of W m-2/DeltaT: its unit is W m-2 degrees C-1. Average with (95% CI) was: model, hPAD = 110.4 (107.8-113.1), R2 = 0.99, n = 45; volunteers, hPAD = 109.8 (95.5-124.1), R2 = 0.83, n = 51; and water immersion, hWATER = 107.1 (98.1-116), R2 = 0.86, n = 94. CONCLUSION: The heat transfer coefficient for the pad was the same in the model and volunteers, and equivalent to hWATER. Therefore, for the same DeltaT and heat transfer area, the Arctic Sun's heat transfer rate would equal water immersion. This has important implications for body cooling/rewarming rates.

The staircase phenomenon at the corrugator supercilii muscle in comparison with the hand muscles.

BACKGROUND: Phonomyography (PMG) is a novel method to monitor neuromuscular block. It is non-invasive and can be applied to any muscle. It can be used interchangeably with mechanomyography (MMG). The staircase phenomenon has not been investigated for this method or at the corrugator supercilii muscle. The purpose of this work was to determine the staircase effect at three different muscles using two different methods. METHODS: In 10 patients undergoing general anaesthesia with sevoflurane, using a laryngeal mask airway without the aid of neuromuscular block, one piezo-electric microphone each was applied to the corrugator supercilii muscle and the first dorsal interosseus muscle. In addition, a force transducer was attached to the tip of the thumb to determine the force of the adductor pollicis muscle. Supramaximal stimulation at 1 Hz was used at the ulnar and the facial nerve. All signals were simultaneously recorded for 30 min. Data are presented as means (SD). RESULTS: The staircase effect was significantly positive for the first dorsal interosseus muscle and the adductor pollicis muscle. The signal potentiation was not significantly different between the first dorsal interosseus muscle with a maximum increase at 148 (19)% using PMG, and the adductor pollicis muscle at 154 (22)% using MMG. The evoked signals reached a plateau after 15-18 min at both muscles. There was only a small initial increase in signal height at the corrugator supercilii to a maximum of 117 (20)% at 7 min, after which the signals decreased to reach a plateau at 25 min. In comparison with the signal height of 105 (25)% at 30 min, there was no significant difference of signal heights throughout the observation period. CONCLUSIONS: A positive staircase phenomenon is found equally at the first dorsal interosseus muscle and the adductor pollicis muscle. There is no significant staircase effect at the corrugator supercilii muscle.