Analgesia-nociception index accurately predicts inadequate pectoralis muscle fascia block (PECS) in patients undergoing breast surgery: A prospective observational study.

BACKGROUND: Postoperative opioid administration has been largely replaced by regional anesthesia techniques. We aimed to determine whether intraoperative Analgesia-Nociception Index (ANI) can aid in early evaluation of the effectiveness of regional blocks such as the pectoralis muscle fascia block (PECS, pectoserratus and interpectoral plane blocks) and predicting the need for analgesics postoperatively. METHODS: This prospective observational study enrolled 30 women (age: 20-80 years) undergoing unilateral, non-intubated, breast tumor excision alone or in conjunction with sentinel lymph node biopsy. PECS block was performed following sedation. ANI readings were obtained at 1-min intervals, and polar coordinates were assigned to the distance from the nipple (0.5-cm intervals) and o'clock position (15-min intervals) for each reading. Pain scores were assessed using a numeric rating scale from 0 to 10, and analgesics were administered depending on pain score post-operatively. RESULTS: 8 (27%), 19 (63%), and 3 (10%) patients received morphine, tramadol, and no analgesics, respectively. In total, 954 ANI measurements were obtained. At the proposed cut-off of 50, the sensitivity and specificity of the ANI nadir for need of post-operative opioids were 0.875 and 0.932, respectively. Block effectiveness was most satisfactory in the upper lateral quadrant of the breast with nipple-areolar complex (NAC) sparing effect. Most average ANI measurements for the NAC were <50. No patient experienced postoperative nausea/vomiting, although one reported dizziness. CONCLUSIONS: The intraoperative ANI nadir <50 was strongly correlated with need for postoperative opioids. The ANI may aid in objectively evaluating the effectiveness of pectoralis muscle fascial blocks and predicting postoperative need for analgesics.

Opioid-sparing anesthesia with dexmedetomidine provides stable hemodynamic and short hospital stay in non-intubated video-assisted thoracoscopic surgery: a propensity score matching cohort study.

OBJECTIVES: Dexmedetomidine is an alpha-2 agonist with anti-anxiety, sedative, and analgesic effects and causes a lesser degree of respiratory depression. We hypothesized that the use of dexmedetomidine in non-intubated video-assisted thoracic surgery (VATS) may reduce opioid-related complications such as postoperative nausea and vomiting (PONV), dyspnea, constipation, dizziness, skin itching, and cause minimal respiratory depression, and stable hemodynamic status. METHODS: Patients who underwent non-intubated VATS lung wedge resection with propofol combined with dexmedetomidine (group D) or alfentanil (group O) between December 2016 and May 2022 were enrolled in this retrospective propensity score matching cohort study. Intraoperative vital signs, arterial blood gas data, perioperative results and treatment outcomes were analyzed. Of 100 patients included in the study (group D, 50 and group O, 50 patients), group D had a significantly lower degree of decrement in the heart rate and the blood pressure than group O. Intraoperative one-lung arterial blood gas revealed lower pH and significant ETCO2. The common opioid-related side effects, including PONV, dyspnea, constipation, dizziness, and skin itching, all of which occurred more frequently in group O than in group D. Patients in group O had significantly longer postoperative hospital stay and total hospital stay than group D, which might be due to opioid-related side effects postoperatively. CONCLUSIONS: The application of dexmedetomidine in non-intubated VATS resulted in a significant reduction in perioperative opioid-related complications and maintenance with acceptable hemodynamic performance. These clinical outcomes found in our retrospective study may enhance patient satisfaction and shorten the hospital stay.

Total intravenous anesthesia decreases hospital stay but not incidence of postoperative pulmonary complications after lung resection surgery: a propensity score matching study.

BACKGROUND: There is no consensus regarding the superiority of volatile or total intravenous anesthesia (TIVA) in reducing the incidence of postoperative pulmonary complications (PPCs) after lung resection surgery (LRS). Thus, the aim of this study was to investigate the different anesthetic regimens and the incidence of PPCs in patients who underwent LRS. We hypothesized that TIVA is associated with a lower incidence of PPCs than volatile anesthesia. METHODS: This was a retrospective cohort study of patients who underwent LRS at Taipei Veterans General Hospital between January 2016 and December 2020. The patients' charts were reviewed and data on patient characteristics, perioperative features, and postoperative outcomes were extracted and analyzed. The patients were categorized into TIVA or volatile anesthesia groups and their clinical data were compared. Propensity score matching was performed to reduce potential selection bias. The primary outcome was the incidence of PPCs, whereas the secondary outcomes were the incidences of other postoperative events, such as length of hospital stay (LOS) and postoperative nausea and vomiting (PONV). RESULTS: A total of 392 patients each were included in the TIVA and volatile anesthesia groups. There was no statistically significant difference in the incidence of PPCs between the volatile anesthesia and TIVA groups. The TIVA group had a shorter LOS (p < 0.001) and a lower incidence of PONV than the volatile anesthesia group (4.6% in the TIVA group vs. 8.2% in the volatile anesthesia group; p = 0.041). However, there were no significant differences in reintubation, 30-day readmission, and re-operation rates between the two groups. CONCLUSIONS: There was no significant difference between the incidence of PPCs in patients who underwent LRS under TIVA and that in patients who underwent LRS under volatile anesthesia. However, TIVA had shorter LOS and lower incidence of PONV which may be a better choice for maintenance of anesthesia in patients undergoing LRS.

Arterial blood pressure waveform in liver transplant surgery possesses variability of morphology reflecting recipients' acuity and predicting short term outcomes.

We investigated clinical information underneath the beat-to-beat fluctuation of the arterial blood pressure (ABP) waveform morphology. We proposed the Dynamical Diffusion Map algorithm (DDMap) to quantify the variability of morphology.  The underlying physiology could be the compensatory mechanisms involving complex interactions between various physiological mechanisms to regulate the cardiovascular system. As a liver transplant surgery contains distinct periods, we investigated its clinical behavior in different surgical steps. Our study used DDmap algorithm, based on unsupervised manifold learning, to obtain a quantitative index for the beat-to-beat variability of morphology. We examined the correlation between the variability of ABP morphology and disease acuity as indicated by Model for End-Stage Liver Disease (MELD) scores, the postoperative laboratory data, and 4 early allograft failure (EAF) scores. Among the 85 enrolled patients, the variability of morphology obtained during the presurgical phase was best correlated with MELD-Na scores. The neohepatic phase variability of morphology was associated with EAF scores as well as postoperative bilirubin levels, international normalized ratio, aspartate aminotransferase levels, and platelet count. Furthermore, variability of morphology presents more associations with the above clinical conditions than the common BP measures and their BP variability indices. The variability of morphology obtained during the presurgical phase is indicative of patient acuity, whereas those during the neohepatic phase are indicative of short-term surgical outcomes.

True intratracheal oxygen concentration delivered by SentriO Oxy™ masks under various respiratory conditions: a bench study.

SentriO Oxy™ is a newly available, Food and Drug Administration-approved oxygenation mask system that provides high oxygenation, even on low-flow (5-10 L/min) oxygen. This study aimed to accurately measure the intratracheal fraction of inspired oxygen (FiO2) using SentriO Oxy™ masks under relatively low oxygen flow rates. A manikin-ventilator-test lung simulation system was used. We measured FiO2 at the level of the carina, 5 minutes after applying 45 different respiratory parameter combinations using SentriO Oxy™ masks. Tidal volume (TV) was set to 300, 500, and 700 mL; respiratory rate (RR) was set to 8, 12, 16, 20, and 24 breaths per minute; and oxygen flow rate was set to 6, 8, and 10 L/min. Our hypothesis was that FiO2 would be proportional to the difference between oxygen flow rate and minute ventilation. FiO2 measured by smaller TV, lower RR, or higher oxygen flows revealed a significantly higher value, confirming our hypothesis. In addition, using linear regression analysis, we found that TV, RR, and oxygen flow were all significant factors influencing the measured FiO2. Our experiment proposed two prediction equations considering the oxygen flow rate, TV, and RR. The results of our study may provide information and prediction of FiO2 for clinicians to use SentriO Oxy™ masks during sedative anesthetic procedures under low oxygen flow rates.

Response surface model comparison and combinations for remifentanil and propofol in describing response to esophageal instrumentation and adverse respiratory events.

BACKGROUND: The primary aim of this essay was to explore the best fitting model in remifentanil-propofol combined administrations during esophageal instrumentation (EI) from five distinct response surface models. The secondary aim was to combine the models to give appropriate effect-site drug concentrations (Ces) range with maximal comfort and safety. METHODS: The Greco, reduced Greco, Minto, Scaled C50 Hierarchy and Fixed C50 Hierarchy models were constructed to fit four drug effects: loss of response to esophageal instrumentation (LREI), loss of response to esophageal instrumentation revised (LREIR), intolerable ventilatory depression (IVD) and respiratory compromise (RC). Models were tested by chi-square statistical test and evaluated with Akaike Information Criterion (AIC). Model prediction performance were measured by successful prediction rate (SPR) and three prediction errors. RESULTS: The reduced Greco model was the best fitting model for LREI and RC, and the Minto model was the best fitting model for LREIR and IVD. The SPRs of reduced Greco model for LREI and RC were 81.76% and 79.81%. The SPRs of Minto model for LREIR and IVD were 80.32% and 80.12%. Overlay of the reduced Greco model for LREI and Minto model for IVD offered visual aid for guidance in drug administration. CONCLUSION: Using proper response surface model to fit different drug effects will describe the interactions between anesthetic drugs better. Combining response surface models to select the more reliable effect-site drug concentrations range can be used to guide clinical drug administration with greater safety and provide an improvement of anesthesia precision.

How early warning with the Oxygen Reserve Index (ORi™) can improve the detection of desaturation during induction of general anesthesia?

The Oxygen Reserve Index (ORi™) is a dimensionless parameter with a value between 0 and 1. It is related to the real-time oxygenation status in the moderate hyperoxic range. The purpose of this study is to investigate the added warning time provided by different ORi alarm triggers and the continuous trends of ORi, SpO2, and PaO2. We enrolled 25 patients who were scheduled for elective surgery under general anesthesia with planned arterial catheterization before induction. The participants received standardized preoxygenation, induction, and intubation. The patients remained apneic and ventilation was resumed when the SpO2 fell below 90%. The ORi and SpO2 were recorded every ten seconds and arterial blood was sampled every minute, from preoxygenation to resumed ventilation. Alarm triggers set to the ORi peak and the ORi 0.55 values provided 300 and 145 s of significant added warning time compared to SpO2 (p < 0.0001). The coefficient of determination was 0.56 between the ORi and the PaO2 ≤ 240 mmHg and showed a positive correlation. The ORi enables the clinicians to monitor the patients' oxygen status during induction of general anesthesia and can improve the detection of impending desaturation. However, further studies are needed to assess its clinical potential in the high hyperoxic range.The protocol was retrospectively registered at ClinicalTrials.gov on July 21, 2021 (NCT04976504).

Improvement in vocal-cord visualization with Trachway video intubating stylet using direct oxygen flow and effective analysis of the fraction of inspired oxygen: a bench study.

The Trachway video intubating stylet device facilitates the visualization of the airways of patients from the tip of an endotracheal tube (ETT) during intubation. The major limitations of Trachway are the restricted view due to secretions and the risk of a prolonged apnea during intubation. We conducted a bench study to verify the performance of an alternative, easily applicable airway device that allows better visualization of trackways during Trachway-assisted intubation and prevents the detrimental effects of apnea-related hypoxia. We conducted a bench study to thoroughly evaluate the oral-secretion-elimination ability of a newly designed oxygen delivery device (ODD) to improve vocal-cord visualization using the three commonly used ETT sizes (i.e., 7, 7.5, and 8 mm). Moreover, we measured the fraction of inspired oxygen (FiO2) under different, continuous oxygen-flow supplies (1-10 L/min) during intubation. Each condition was analyzed for a 2 min video-stylet-intubation period. The supplemental oxygen flow and FiO2 fraction achieved using our ODD were higher, and smaller ETTs exhibited better secretion elimination. The ODD, which can be easily coupled with Trachway stylets, enabled high-quality visualization during oxygen flows of 6-8 L/min, and higher FiO2 fractions were achieved at higher oxygen flow rates. The use of the ODD improved the visualization of the airways during video stylet-assisted intubations using the additional FiO2 supply. The ODD developed in this study improves the visualization of airways with Trachway stylets and enhances the safety of intubation.

Fire safety study on high-flow nasal oxygen in shared-airway surgeries with diathermy and laser: simulation based on a physical model.

High-flow nasal oxygen (HFNO) has been used in "tubeless" shared-airway surgeries but whether HFNO increased the fire hazard is yet to be examined. We used a physical model for simulation to explore fire safety through a series of ignition trials. An HFNO device was attached to a 3D-printed nose with nostrils connected to a degutted raw chicken. The HFNO device was set at twenty combinations of different oxygen concentration and gas flow rate. An electrocautery and diode laser were applied separately to a fat cube in the cavity of the chicken. Ten 30 s trials of continuous energy source application were conducted. An additional trial of continuous energy application was conducted if no ignition was observed for all the ten trials. A total of eight short flashes were observed in one hundred electrocautery tests; however, no continuous fire was observed among them. There were thirty-six events of ignition in one hundred trials with laser, twelve of which turned into violent self-sustained fires. The factors found to be related to a significantly increased chance of ignition included laser application, lower gas flow, and higher FiO2. The native tissue and smoke can ignite and turn into violent self-sustained fires under HFNO and continuous laser strikes, even in the absence of combustible materials. The results suggest that airway surgeries must be performed safely with HFNO if only a short intermittent laser is used in low FiO2.

Fiber-Needle Swept-Source Optical Coherence Tomography for the Real-Time Visualization of the Transversus Abdominis Plane Block Procedure in a Swine Model.

BACKGROUND: Fascia blocks (eg, the transversus abdominis plane [TAP] block) target the intermuscular fascia layers. Ultrasound techniques have allowed peripheral blocks to be performed with accuracy and safety, however, with limitations. Optical coherence tomography (OCT) is based on low-coherence interferometry. In this study, we examined the ability of OCT to identify the TAP. METHODS: A swept-source OCT probe was placed in a 17-gauge needle to obtain imaging. The needle was inserted within 2 different angle ranges (0°-30° and 30°-60°) on a slice of pork belly to assess imaging characteristics. A series of real-time OCT imaging of the muscle, fascia, and interfascial space was obtained. The tissue location of the needle tip was identified using near-infrared (NIR) imaging. In vivo OCT imaging was further done on 3 female 6-month-old native Chinese Landrance Duroc pigs. Real-time images of tissue layers were obtained with needle insertion. Ultrasound imaging of the OCT needle probe was also performed at the same time for needle trajectory guidance. After imaging, the OCT probe was removed, and 5 mL of normal saline was injected via the needle to confirm correct fascia plane identification. RESULTS: In and ex vivo studies showed clear visual distinction of muscle, fascia, and interfascial layer with OCT, with limitations. Independent validation of OCT criteria for the muscle/fascia differentiation by 20 OCT readers for the in vivo data demonstrated the sensitivity = 0.91, specificity = 0.90, and accuracy = 0.89. Although the angle of needle entry affected the depth of OCT penetration in the muscle, the attenuation coefficient values of the fascia and muscle tissue were statistically different (P < .001) and with high area under the receiver operating characteristics (ROC) curve (AUC) (AUC = 0.93 in 0°-30° and AUC = 1 in 30°-60°) for fascia identification. CONCLUSIONS: This study introduced a novel needle imaging probe method to identify the transversus abdominis fascia plane in real-time. Quantitative calculation of the attenuation coefficients can further aid objective identification by providing direct confirmation of the tip position, increasing the first-pass success rate, and decreasing the need for needle repositioning. Combining OCT and ultrasound may improve the accuracy of anesthetics placement.

Novel Imaging Revealing Inner Dynamics for Cardiovascular Waveform Analysis via Unsupervised Manifold Learning.

BACKGROUND: Cardiovascular waveforms contain information for clinical diagnosis. By learning and organizing the subtle change of waveform morphology from large amounts of raw waveform data, unsupervised manifold learning helps delineate a high-dimensional structure and display it as a novel 3-dimensional (3D) image. We hypothesize that the shape of this structure conveys clinically relevant inner dynamics information. METHODS: To validate this hypothesis, we investigate the electrocardiography (ECG) waveform for ischemic heart disease and arterial blood pressure (ABP) waveform in dynamic vasoactive episodes. We model each beat or pulse to be a point lying on a manifold-like a surface-and use the diffusion map (DMap) to establish the relationship among those pulses. The output of the DMap is converted to a 3D image for visualization. For ECG datasets, first we analyzed the non-ST-elevation ECG waveform distribution from unstable angina to healthy control in the 3D image, and we investigated intraoperative ST-elevation ECG waveforms to show the dynamic ECG waveform changes. For ABP datasets, we analyzed waveforms collected under endotracheal intubation and administration of vasodilator. To quantify the dynamic separation, we applied the support vector machine (SVM) analysis and reported the total accuracy and macro-F1 score. We further performed the trajectory analysis and derived the moving direction of successive beats (or pulses) as vectors in the high-dimensional space. RESULTS: For the non-ST-elevation ECG, a hierarchical tree structure comprising consecutive ECG waveforms spanning from unstable angina to healthy control is presented in the 3D image (accuracy = 97.6%, macro-F1 = 96.1%). The DMap helps quantify and visualize the evolving direction of intraoperative ST-elevation myocardial episode in a 1-hour period (accuracy = 97.58%, macro-F1 = 96.06%). The ABP waveform analysis of Nicardipine administration shows interindividual difference (accuracy = 95.01%, macro-F1 = 96.9%) and their common directions from intraindividual moving trajectories. The dynamic change of the ABP waveform during endotracheal intubation shows a loop-like trajectory structure, which can be further divided using the manifold learning knowledge obtained from Nicardipine. CONCLUSIONS: The DMap and the generated 3D image of ECG or ABP waveforms provides clinically relevant inner dynamics information. It provides clues of acute coronary syndrome diagnosis, shows clinical course in myocardial ischemic episode, and reveals underneath physiological mechanism under stress or vasodilators.

Enhanced recovery after surgery: Prediction for early extubation in video-assisted thoracic surgery using a response surface model in anesthesia.

BACKGROUND/PURPOSE: Enhanced recovery after surgery (ERAS) is a growing tendency in modern perioperative period management, but no protocol has been established for a strategy that optimally facilitates rapid recovery from anesthesia. We hypothesized that applying a total intravenous anesthesia (TIVA) method to the response surface model (RSM) would allow prediction of the emergence and endotracheal tube extubation in cases undergoing video-assisted thoracotomy surgery (VATS). METHODS: Thirty patients who were scheduled to undergo VATs under TIVA were enrolled. Pharmacokinetic profiles were calculated using a Tivatrainer. Emergence from anesthesia was observed and the exact time point of the regained response (RR) was recorded. The effect of concentration was analyzed and applied to a response surface model. RESULTS: The cumulative prediction curve of the RR was closer to the 50% probability as set by the OAA/S ≥ 4 than by the OAA/S ≥ 2 model. The median, averages, and standard deviations of the time differences were 14.5, 22.05 ± 19.23 min for the OAA/S ≥2 model and 10.4, 14.26 ± 10.40 min for the OAA/S ≥ 4 model. CONCLUSION: The OAA/S ≥ 4 model could identify the target concentration in propofol-remifentanil pairs that predicted the time of emergence from VATS in 10 min. Our results indicate that RSM can be used to derive an ERAS protocol for VATS under TIVA. Further studies should investigate application of RSM to predict ERAS for various types of procedures.

Plasma concentration based response surface model predict better than effect-site concentration based model for wake-up time during gastrointestinal endoscopy sedation.

BACKGROUND: Sedation for esophagogastroduodenoscopy (EGD) and colonoscopy is characterized by rapid patient induction and emergence. The drugs midazolam and alfentanil have long been used for procedural sedation; however, the relationship between plasma or effect-site concentrations (Cp or Ce, respectively) and emergence remains unclear. The aim of this study is to develop patient wake-up prediction models for both Cp and Ce using response surface modeling, a pharmacodynamics tool for assessing patients' responses. METHODS: The Observer's Alertness/Sedation (OAA/S) score was used to monitor sedation depth during the examinations. Concentration pairs of midazolam and alfentanil were calculated for each of Cp and Ce using pharmacokinetic simulation software. Response surface models were developed using the Greco construct. Temporal analysis was done by comparing model-predicted wake-up time with true patient wake-up time. RESULTS: Thirty-three patients with an average body mass index of 21.85 ± 2.3 kg/m2 were pooled for analysis. The average duration of examination were 2.9 ± 1.4 min for EGD and 6.6 ± 2.7 min for colonoscopy. Seventy-five concentration pairs of midazolam and alfentanil were obtained for each Cp and Ce. The Cp-based Greco response surface model showed significant synergy between midazolam and alfentanil and was a better predictor of patient wake-up time, with an average deviation of 1.0 ± 3.9 min, while the Ce model show time deviation greater than 20 min. CONCLUSION: The early phases of drug distribution are unique and complicated by nonsteady-state concentrations, and our study revealed that Ce-based wake-up time prediction is more difficult under these circumstances.

Tracheal sounds accurately detect apnea in patients recovering from anesthesia.

Apnea should be monitored continuously in the post anesthesia care unit (PACU) to avoid serious complications. It has been confirmed that tracheal sounds can be used to detect apnea during sedation in healthy subjects, but the performance of this acoustic method has not been evaluated in patients with frequent apnea events in the PACU. Tracheal sounds were acquired from the patients in the PACU using a microphone encased in a plastic bell. Concurrently, a processed nasal pressure signal was used as a reference standard to identify real respiratory events. The logarithm of the tracheal sound variance (log-var) was used to detect apnea, and the results were compared to the reference method. Sensitivity, specificity, positive likelihood ratios (PLR), and negative likelihood ratios (NLR) were calculated. One hundred and twenty-one patients aged 55.5 ± 13.2 years (mean ± SD) with a body mass index of 24.6 ± 3.7 kg/m2 were included in data analysis. The total monitoring time was 52.6 h. Thirty-four patients experienced 236 events of apnea lasting for a total of 122.2 min. The log-var apnea detection algorithm detected apnea with 92% sensitivity, 98% specificity, 46 PLR and 0.08 NLR. The performance of apnea detection in the PACU using the log-var tracheal sounds method proved to be reliable and accurate. Tracheal sounds could be used to minimize the potential risks from apnea in PACU patients.

Novel mandibular advancement bite block with supplemental oxygen to both nasal and oral cavity improves oxygenation during esophagogastroduodenoscopy: a bench comparison.

Drug-induced respiratory depression is a major cause of serious adverse events. Adequate oxygenation is very important during sedated esophagogastroduodenoscopy (EGD). Nasal breathing often shifts to oral breathing during open mouth EGD. A mandibular advancement bite block was developed for EGD using computer-assisted design and three-dimensional printing techniques. The mandible is advanced when using this bite block to facilitate airway opening. The device is composed of an oxygen inlet with one opening directed towards the nostril and another opening directed towards the oral cavity. The aim of this bench study was to compare the inspired oxygen concentration (FiO2) provided by the different nasal cannulas, masks, and bite blocks commonly used in sedated EGD. A manikin head was connected to one side of a two-compartment lung model by a 7.0 mm endotracheal tube with its opening in the nasopharyngeal position. The other compartment was driven by a ventilator to mimic "patient" inspiratory effort. Using this spontaneously breathing lung model, we evaluated five nasal cannulas, two face masks, and four new oral bite blocks at different oxygen flow rates and different mouth opening sizes. The respiratory rate was set at 12/min with a tidal volume of 500 mL and 8/min with a tidal volume of 300 mL. Several Pneuflo resistors of different sizes were used in the mouth of the manikin head to generate different degrees of mouth opening. FiO2 was evaluated continuously via the endotracheal tube. All parameters were evaluated using a Datex anesthesia monitoring system. The mandibular advancement bite block provided the highest FiO2 under the same supplemental oxygen flow. The FiO2 was higher for devices with oxygen flow provided via an oral bite block than that provided via the nasal route. Under the same supplemental oxygen flow, the tidal volume and respiratory rate also played an important role in the FiO2. A low respiratory rate with a smaller tidal volume has a relative high FiO2. The ratio of nasal to oral breathing played an important role in the FiO2 under hypoventilation but less role under normal ventilation. Bite blocks deliver a higher FiO2 during EGD. The ratio of nasal to oral breathing, supplemental oxygen flow, tidal volume, and respiratory rate influenced the FiO2 in most of the supplemental oxygen devices tested, which are often used for conscious sedation in patients undergoing EGD and colonoscopy.

Double Assurance of Epidural Space Detection Using Fiberoptics-Based Needle Design and Autofluorescence Technologies for Epidural Blockade in Painless Labor.

Purpose: Technology of reflectance spectroscopy incorporated with auto-fluorescence spectroscopy were employed to increase the safety of epidural placement in regional anesthesia which is generally used for surgery, epidural anesthesia, post-operative pain control and painless childbirth. Method: Ex vivo study of auto-fluorescence spectroscopy was performed for the para-vertebral tissues contained fat, interspinous ligament, supraspinous ligament and ligamentumflavum by multimode microplate reader at wavelength 405 nm for the purpose of tissue differentiation. A specially designed optic-fiber-embedded needle was employed to incorporate with both reflectance and autofluorescence spectroscopies in order to probe the epidural space as double assurance demands. In vivo study was carried out in a Chinese native swine weighted about 30 kg under intubated general anesthesia with ventilation support. The reflective (405 nm) and autofluorescence signals (λ and λ*) were recorded at 5 different sites by an oscilloscope during the needle puncture procedure from skin to epidural space in the back of the swine. Results: Study of either autofluorescence spectroscopy for tissue samples or ex vivo needle puncture in porcine trunk tissues indicates that ligmentumflavum has at least 10-fold higher fluorescence intensity than the other tissues. In the in vivo study, ligamentumflavum shows a double-peak character for both reflectance and autofluorescence signals. The epidural space is located right after the drop from the double-peak. Both peaks of reflectance and fluorescence are coincident which ensures that the epidural space is correctly detected. Conclusions: The fiber-optical technologies of double-assurance demands for tissue discrimination during epidural needle puncture can not only provide an objective visual information in a real-time fashion but also it can help the operator to achieve much higher success rate in this anesthesia procedure.

Efficiency of oxygen delivery through different oxygen entrainment devices during sedation under low oxygen flow rate: a bench study.

Sedative anesthetic procedures outside the operating room may depend on cylinders as oxygen source. Cylinders have limited storage capacity and a low oxygen flow rate improves the durability. We conducted the bench study to evaluate the fraction of inspired oxygen (FiO2) in different oxygen entrainment devices under low oxygen flow rate. The purpose of the bench study was to provide information to choose appropriate oxygen entrainment devices in non-operating room sedative anesthetic procedures. We utilized a manikin head-test lung-ventilator model and evaluated eight oxygen entrainment devices, including four nasal cannulas, two oral bite blocks, and two masks. Two different minute volumes that defined as the normal ventilation and the hypoventilation group were evaluated. Three pneuflow resistors were placed in turn in the mouth represented ratio of the nasal/oral breathing. Each condition was sampled 70 times after a 3 min ventilation period. Most devices had few drop in FiO2 according to the increased oral breathing ratio in normal ventilation. Most devices had obvious drop in FiO2 related to the increased oral breathing ratio in hypoventilation. Oxygen reservoir units had little effect for accumulating oxygen in normal ventilation. In the hypoventilation group, oxygen reservoir units helped oxygen retention in local area and maintained a higher oxygen concentration. There were multiple factors lead to different oxygen fraction that we measured, such as different devices, respiratory patterns, and oxygen reservoir units. The result of our bench study provided some information for anesthesiologist to choose appropriate oxygen entrainment devices in various sedative anesthetic procedures.

Oral capnography is more effective than nasal capnography during sedative upper gastrointestinal endoscopy.

The role of capnography in esophagogastroduodenoscopy (EGD) is controversial. Simultaneous supplemental oxygen, position of patient, open mouth breathing pattern, and anatomy of the oral and nasal cavity can influence capnography accuracy. This study first measured capnographic data via the nasal or oral cavity during sedated EGD. Secondly, we investigated the influence of supplementary oxygen through the oral cavity on the capnographic reading. Patients with ASA class I or II status admitted for routine EGD exams were enrolled. End-tidal carbon dioxide measurements were performed simultaneously via nasal catheter and oral catheter with standard oral bite and nasal cannula supplementary oxygen when the patient is awake, during sedation and during sedation with endoscopy. The influence of oral supplementary oxygen, oral capnography were recorded using a mandibular advancement bite block. One hundred and four patients were enrolled. Breathing in the conscious patient is conducted primarily via the nostrils (95%). When sedated with endoscope placement, the percentage of nasal breathing decreased significantly to 47% and oral capnography sufficiently captured data in 100% of patients. Supplementary oral oxygen decreased oral capnographic measurement significantly (38.89 ± 7.148 vs. 30.73 ± 7.84, p < 0.001). However, the measurements using the MA bite block did not differ from oral cavity catheter (28.86 ± 8.51 vs. 30.73 ± 7.839, p = 0.321). The conscious patient breathes mostly nasally while the sedated patient breathes mostly orally during EGD when an oral bite is in place. Capnography measurement via oral cannula increases the measurement accuracy and efficacy. Oral supplementary oxygen may decrease capnographic measurement but still provide sufficient reading for interpretation.

A Coaxial Dual-element Focused Ultrasound Probe for Guidance of Epidural Catheterization: An Experimental Study.

Ultrasound guidance for epidural block has improved clinical blind-trial problems but the design of present ultrasonic probes poses operating difficulty of ultrasound-guided catheterization, increasing the failure rate. The purpose of this study was to develop a novel ultrasonic probe to avoid needle contact with vertebral bone during epidural catheterization. The probe has a central circular passage for needle insertion. Two focused annular transducers are deployed around the passage for on-axis guidance. A 17-gauge insulated Tuohy needle containing the self-developed fiber-optic-modified stylet was inserted into the back of the anesthetized pig, in the lumbar region under the guidance of our ultrasonic probe. The inner transducer of the probe detected the shallow echo signals of the peak-peak amplitude of 2.8 V over L3 at the depth of 2.4 cm, and the amplitude was decreased to 0.8 V directly over the L3 to L4 interspace. The outer transducer could detect the echoes from the deeper bone at the depth of 4.5 cm, which did not appear for the inner transducer. The operator tilted the probe slightly in left-right and cranial-caudal directions until the echoes at the depth of 4.5 cm disappeared, and the epidural needle was inserted through the central passage of the probe. The needle was advanced and stopped when the epidural space was identified by optical technique. The needle passed without bone contact. Designs of the hollow probe for needle pass and dual transducers with different focal lengths for detection of shallow and deep vertebrae may benefit operation, bone/nonbone identification, and cost.

A desflurane and fentanyl dosing regimen for wake-up testing during scoliosis surgery: Implications for the time-course of emergence from anesthesia.

BACKGROUND/PURPOSE: The Stagnara wake-up test assesses neurological deficits during scoliosis surgery, and response surface interaction models for opioids and inhaled agents predicts anesthetic drug effects. We hypothesized that there is an optimal desflurane-fentanyl dosing regimen that can provide a faster and more predictable wake-up time, while also ensuring adequate analgesia during wake-up testing. METHODS: Twenty-three American Society of Anesthesiologists Class I-II scoliosis patients who received desflurane-fentanyl anesthetic regimens were enrolled in this posthoc study, and their intraoperative drug administration data were collected retrospectively. Desflurane and fentanyl effect site concentrations were calculated using pharmacokinetic models, and converted to equivalent remifentanil-sevoflurane concentrations. RESULTS: Results were fitted into Greco models for predicting the probability of an Observers Assessment of Alertness/Sedation score of <2. At time of wake-up, the models correctly predicted the probability that patients would respond to voice prompts and prodding was approximately 50%. The probability of pain intensity was distributed between 50% and 95%, indicating a low degree of pain at emergence. When comparing subgroups defined by calculated effect-site fentanyl concentrations, the wake-up time in the intermediate concentration group was significantly shorter than that in the high concentration group (p = 0.024). CONCLUSION: This study provides evidence that desflurane-fentanyl-based anesthesia is conducive to rapid emergence followed by an immediate neurological evaluation. Intermediate fentanyl effect-site concentrations (1-2 ng/mL) at time of wake-up were associated with good balance between rapid emergence and adequate analgesia. Furthermore, we believe that generalizing response surface models to a variety of inhalation agent-opioid combinations using simple relative potency relationships is possible and practical.