Accuracy and Precision of Three Acceleromyographs, Three Electromyographs, and a Mechanomyograph Measuring the Train-of-four Ratio in the Absence of Neuromuscular Blocking Drugs.

BACKGROUND: The accuracy and precision of currently available, widely used acceleromyograph and electromyograph neuromuscular blockade monitors have not been well studied. In addition, the normalization of the train-of-four ratio from acceleromyography (train-of-four ratio [T4/T1] divided by the baseline train-of-four ratio) has not been validated in comparison to mechanomyography. METHODS: Enrolled patients had surgery under general anesthesia with a supraglottic airway and without any neuromuscular blocking drugs. Three acceleromyograph monitors, three electromyograph monitors, and a mechanomyograph built in the authors' laboratory were tested. Most patients had an electromyograph and the mechanomyograph on one arm and a third monitor on the contralateral arm. Train-of-four ratios were collected every 12 to 20 s for the duration of the anesthetic. At least 1,000 train-of-four ratios were recorded for each device. Gauge repeatability and reproducibility analysis was performed. RESULTS: Twenty-eight patients were enrolled. In total, 9,498 train-of-four ratio measurements were collected. Since no neuromuscular blocking drugs were used, the expected train-of-four ratio was 1.0. All of the acceleromyograph monitors produced overshoot in the train-of-four ratio (estimated means, 1.10 to 1.13) and substantial variability (gauge SDs, 0.07 to 0.18). Normalization of the train-of-four ratio measured by acceleromyography improved the estimated mean for each device (0.97 to 1.0), but the variability was not improved (gauge SDs, 0.06 to 0.17). The electromyograph and the mechanomyograph monitors produced minimal overshoot (estimated means, 0.99 to 1.01) and substantially less variation (gauge SDs, 0.01 to 0.02). For electromyography and mechanomyography, 0.3% of all train-of-four ratios were outside of the range 0.9 to 1.1. For acceleromyography, 27 to 51% of normalized train-of-four ratios were outside the range of 0.9 to 1.1. CONCLUSIONS: Three currently available acceleromyograph monitors produced overshoot and substantial variability that could be clinically significant. Normalization corrected the overshoot in the average results but did not reduce the wide variability. Three electromyograph monitors measured the train-of-four ratio with minimal overshoot and variability, similar to a mechanomyograph.

Reducing airborne transmissible diseases in perioperative environments.

The COVID-19 pandemic has transformed our understanding of aerosol transmissible disease and the measures required to minimise transmission. Anaesthesia providers are often in close proximity to patients and other hospital staff for prolonged periods while working in operating and procedure rooms. Although enhanced ventilation provides some protection from aerosol transmissible disease in these work areas, close proximity and long duration of exposure have the opposite effect. Surgical masks provide only minimal additional protection. Surgical patients are also at risk from viral and bacterial aerosols. Despite having recently experienced the most significant pandemic in 100 yr, we continue to lack adequate understanding of the true risks encountered from aerosol transmissible diseases in the operating room, and the best course of action to protect patients and healthcare workers from them in the future. Nevertheless, hospitals can take specific actions now by providing respirators for routine use, encouraging staff to utilise respirators routinely, establishing triggers for situations that require respirator use, educating staff concerning the prevention of aerosol transmissible diseases, and providing portable air purifiers for perioperative spaces with low levels of ventilation.

Comparative performance of stimpod electromyography with mechanomyography for quantitative neuromuscular blockade monitoring.

PURPOSE: The purpose of this study was to compare the Stimpod electromyograph neuromuscular blockade monitor to mechanomyography, which is widely considered to be the reference standard. METHODS: The Stimpod electromyograph was used with its designated electrode array on the same hand as the mechanomyograph. Pairs of train-of-four measurements were recorded every 0.5-2 min. When the train-of-four count was zero on the electromyograph monitor, pairs of post tetanic count measurements were recorded every 2.5 min, instead of train-of-four measurements. Measurements were recorded from immediately after induction of anesthesia until just before emergence. Stimulation current was set to 60 mA with a duration of 200 microsec. The mechanomyography recording system recorded each twitch waveform for analysis. High resolution electromyograph waveforms were also recorded using a datalogger accessory provided by the manufacturer, facilitating inspection of individual waveforms. The administration of neuromuscular blocking drugs was left up to the discretion of the anesthesia care team. RESULTS: Twenty-three patients contributed 1,088 data pairs suitable for analysis. Bland-Altman analysis of 415 pairs of train-of-four ratios showed a bias of 0.028 and limits of agreement of -0.18 and 0.24. Two hundred seventy-three train-of-four count data pairs were compared by Cohen's quadratically weighted kappa which was calculated to be 0.44, indicating moderate agreement. Three hundred thirty-eight post tetanic count data pairs were compared by Cohen's quadradically weighted kappa which was calculated to be 0.80, indicating substantial agreement. CONCLUSION: The electromyograph produced results that were comparable to the mechanomyograph.

Evolution of a laboratory mechanomyograph.

Mechanomyography is currently the accepted laboratory reference standard for quantitative neuromuscular blockade monitoring. Mechanomyographs are not commercially available. Previously, a mechanomyograph was built by our laboratory and used in several clinical studies. It was subsequently redesigned to improve its usability and functionality and to accommodate a wider range of hand sizes and shapes using an iterative design process. Each version of the redesigned device was initially tested for usability and functionality in the lab with the investigators as subjects without electrical stimulation. The redesigned devices were then assessed on patients undergoing elective surgery under general anesthesia without neuromuscular blocking drugs. Since the patients were not paralyzed, the expected train-of-four ratio was 1.0. The device accuracy and precision were represented by the train-of-four ratio mean and standard deviation. If issues with the device's useability or functionality were discovered, changes were made, and the redesign processes repeated. The final mechanomyograph design was used to collect 2,362 train-of-four ratios from 21 patients. The mean and standard deviation of the train-of-four ratios were 0.99 ± 0.030. Additionally, the final mechanomyograph design was easier to use and adjust than the original design and fit a wider range of hand sizes. The final design also reduced the frequency of adjustments and the time needed for adjustments, facilitating data collection during a surgical procedure.

Comparison of a Modern Digital Mechanomyograph to a Mechanomyograph Utilizing an Archival Grass Force Transducer.

BACKGROUND: Mechanomyography is the traditional gold standard research technique for quantitative assessment of neuromuscular blockade. Mechanomyography directly measures the isometric force generated by the thumb in response to ulnar nerve stimulation. Researchers must construct their own mechanomyographs since commercial instruments are no longer available. A mechanomyograph was constructed, and its performance was compared against an archival mechanomyography system from the 1970s that utilized an FT-10 Grass force transducer, hypothesizing that train-of-four ratios recorded on each device would be equivalent. METHODS: A mechanomyograph was constructed using 3D-printed components and modern electronics. An archival mechanomyography system was assembled from original components, including an FT-10 Grass force transducer. Signal digitization for computerized data collection was utilized instead of the original paper strip chart recorder. Both devices were calibrated with standard weights to demonstrate linear voltage response curves. The mechanomyographs were affixed to opposite arms of patients undergoing surgery, and the train-of-four ratio was measured during the onset and recovery from rocuronium neuromuscular blockade. RESULTS: Calibration measurements exhibited a positive linear association between voltage output and calibration weights with a linear correlation coefficient of 1.00 for both mechanomyography devices. The new mechanomyograph had better precision and measurement sensitivity than the archival system: 5.3 mV versus 15.5 mV and 1.6 mV versus 5.7 mV, respectively (P < 0.001 for both). A total of 767 pairs of train-of-four ratio measurements obtained from eight patients had positive linear association (R 2 = 0.94; P < 0.001). Bland-Altman analysis resulted in bias of 3.8% and limits of agreement of -13% and 21%. CONCLUSIONS: The new mechanomyograph resulted in similar train-of-four ratio measurements compared to an archival mechanomyography system utilizing an FT-10 Grass force transducer. These results demonstrated continuity of gold standard measurement of neuromuscular blockade spanning nearly 50 yr, despite significant changes in the instrumentation technology.

Lessons from aviation safety: pilot monitoring, the sterile flight deck rule, and aviation-style computerised checklists in the operating room.

Commercial aviation practices including the role of the pilot monitoring, the sterile flight deck rule, and computerised checklists have direct applicability to anaesthesia care. The pilot monitoring performs specific tasks that complement the pilot flying who is directly controlling the aircraft flight path. The anaesthesia care team, with two providers, can be organised in a manner that is analogous to the two-pilot flight deck. However, solo providers, such as solo pilots, can emulate the pilot monitoring role by reading checklists aloud, and utilise non-anaesthesia providers to fulfil some of the functions of pilot monitoring. The sterile flight deck rule states that flight crew members should not engage in any non-essential or distracting activity during critical phases of flight. The application of the sterile flight deck rule in anaesthesia practice entails deliberately minimising distractions during critical phases of anaesthesia care. Checklists are commonly used in the operating room, especially the World Health Organization surgical safety checklist. However, the use of aviation-style computerised checklists offers additional benefits. Here we discuss how these commercial aviation practices may be applied in the operating room.

Train-of-four monitoring with the twitchview monitor electctromyograph compared to the GE NMT electromyograph and manual palpation.

The purpose of this study was to compare train-of-four count and ratio measurements with the GE electromyograph to the TwitchView electromyograph, that was previously validated against mechanomography, and to palpation of train-of-four count. Electrodes for both monitors were applied to the same arm of patients undergoing an unrestricted general anesthetic. Train-of-four measurements were performed with both monitors approximately every 5 min. In a subset of patients, thumb twitch was palpated by one of the investigators. Eleven patients contributed 807 pairs of train-of-four counts or ratios. A subset of 5 patients also contributed palpated train-of-four counts. Bland-Altman analysis of the train-of-four ratio found a bias of 0.24 in the direction of a larger ratio with the GE monitor. For 72% of data pairs, the GE monitor train-of-four ratios were larger. For 59% of data pairs, the GE monitor train-of-four counts were larger (p < 0.0001). For 11% of data pairs, the GE monitor train-of-four count was 4 when the Twitchview monitor count was zero. When manual palpation of train-of-four count was compared to train-of-four count determined by the monitors, 70% of data pairs were identical between palpation and TwitchView train-of-four count, while 30% of data pairs were identical between palpation and GE train-of-four count. For 7% of data pairs, the GE monitor train-of-four count was 4 when the palpation count was 0. The GE electromyograph may overestimate the train-of-four count and ratio. The GE electromyograph frequently reported 4 twitches when none were actually present due to misinterpretation of artifacts.

Development of an aviation-style computerized checklist displayed on a tablet computer for improving handoff communication in the post-anesthesia care unit.

Critical patient care information is often omitted or misunderstood during handoffs, which can lead to inefficiencies, delays, and sometimes patient harm. We implemented an aviation-style post-anesthesia care unit (PACU) handoff checklist displayed on a tablet computer to improve PACU handoff communication. We developed an aviation-style computerized checklist system for use in procedural rooms and adapted it for tablet computers to facilitate the performance of PACU handoffs. We then compared the proportion of PACU handoff items communicated before and after the implementation of the PACU handoff checklist on a tablet computer. A trained observer recorded the proportion of PACU handoff information items communicated, any resistance during the performance of the checklist, the type of provider participating in the handoff, and the time required to perform the handoff. We also obtained these patient outcomes: PACU length of stay, respiratory events, post-operative nausea and vomiting, and pain. A total of 209 PACU handoffs were observed before and 210 after the implementation of the tablet-based PACU handoff checklist. The average proportion of PACU handoff items communicated increased from 49.3% (95% CI 47.7-51.0%) before checklist implementation to 72.0% (95% CI 69.2-74.9%) after checklist implementation (p < 0.001). A tablet-based aviation-style handoff checklist resulted in an increase in PACU handoff items communicated, but did not have an effect on patient outcomes.

Counting train-of-four twitch response: comparison of palpation to mechanomyography, acceleromyography, and electromyography.

BACKGROUND: Train-of-four twitch monitoring can be performed using palpation of thumb movement, or by the use of a more objective quantitative monitor, such as mechanomyography, acceleromyography, or electromyography. The relative performance of palpation and quantitative monitoring for determination of the train-of-four ratio has been studied extensively, but the relative performance of palpation and quantitative monitors for counting train-of-four twitch responses has not been completely described. METHODS: We compared train-of-four counts by palpation to mechanomyography, acceleromyography (Stimpod™), and electromyography (TwitchView Monitor™) in anaesthetised patients using 1691 pairs of measurements obtained from 46 subjects. RESULTS: There was substantial agreement between palpation and electromyography (kappa = 0.80), mechanomyography (kappa = 0.67), or acceleromyography (kappa = 0.63). Electromyography with TwitchView and mechanomyography most closely resembled palpation, whereas acceleromyography with StimPod often underestimated train-of-four count. With palpation as the comparator, acceleromyography was more likely to measure a lower train-of-four count, with 36% of counts less than palpation, and 3% more than palpation. For mechanomyography, 31% of train-of-four counts were greater than palpation, and 9% were less. For electromyography, 15% of train-of-four counts were greater than palpation, and 12% were less. The agreement between acceleromyography and electromyography was fair (kappa = 0.38). For acceleromyography, 39% of train-of-four counts were less than electromyography, and 5% were more. CONCLUSIONS: Acceleromyography with the StimPod frequently underestimated train-of-four count in comparison with electromyography with TwitchView.

Infection Prevention Precautions for Routine Anesthesia Care During the SARS-CoV-2 Pandemic.

Many health care systems around the world continue to struggle with large numbers of SARS-CoV-2-infected patients, while others have diminishing numbers of cases following an initial surge. There will most likely be significant oscillations in numbers of cases for the foreseeable future, based on the regional epidemiology of severe acute respiratory syndrome coronavirus 2 (SARS-CoV-2). Less affected hospitals and facilities will attempt to progressively resume elective procedures and surgery. Ramping up elective care in hospitals that deliberately curtailed elective care to focus on SARS-CoV-2-infected patients will present unique and serious challenges. Among the challenges will be protecting patients and providers from recurrent outbreaks of disease while increasing procedure throughput. Anesthesia providers will inevitably be exposed to SARS-CoV-2 by patients who have not been diagnosed with infection. This is particularly concerning in consideration that aerosols produced during airway management may be infective. In this article, we recommend an approach to routine anesthesia care in the setting of persistent but variable prevalence of SARS-CoV-2 infection. We make specific recommendations for personal protective equipment and for the conduct of anesthesia procedures and workflow based on evidence and expert opinion. We propose practical, relatively inexpensive precautions that can be applied to all patients undergoing anesthesia. Because the SARS-CoV-2 virus is spread primarily by respiratory droplets and aerosols, effective masking of anesthesia providers is of paramount importance. Hospitals should follow the recommendations of the Centers for Disease Control and Prevention for universal masking of all providers and patients within their facilities. Anesthesia providers should perform anesthetic care in respirator masks (such as N-95 and FFP-2) whenever possible, even when the SARS-CoV-2 test status of patients is negative. Attempting to screen patients for infection with SARS-CoV-2, while valuable, is not a substitute for respiratory protection of providers, as false-negative tests are possible and infected persons can be asymptomatic or presymptomatic. Provision of adequate supplies of respirator masks and other respiratory protection equipment such as powered air purifying respirators (PAPRs) should be a high priority for health care facilities and for government agencies. Eye protection is also necessary because of the possibility of infection from virus coming into contact with the conjunctiva. Because SARS-CoV-2 persists on surfaces and may cause infection by contact with fomites, hand hygiene and surface cleaning are also of paramount importance.

Aviation-Style Computerized Surgical Safety Checklist Displayed on a Large Screen and Operated by the Anesthesia Provider Improves Checklist Performance.

BACKGROUND: Many hospitals have implemented surgical safety checklists based on the World Health Organization surgical safety checklist, which was associated with improved outcomes. However, the execution of the checklists is frequently incomplete. We reasoned that aviation-style computerized checklist displayed onto large, centrally located screen and operated by the anesthesia provider would improve the performance of surgical safety checklist. METHODS: We performed a prospective before and after observational study to evaluate the effect of a computerized surgical safety checklist system on checklist performance. We created checklist software and translated our 4-part surgical safety checklist from wall poster into an aviation-style computerized format displayed onto a large, centrally located screen and operated by the anesthesia provider. Direct observers recorded performance of the first part of the surgical safety checklist that was initiated before anesthetic induction, including completion of each checklist item, provider participation and distraction level, resistance to use of the checklist, and the time required for checklist completion before and after checklist system implementation. We compared trends of the proportions of cases with 100% surgical safety checklist completion over time between pre- and postintervention periods and assessed for a jump at the start of intervention using segmented logistic regression model while controlling for potential confounding variables. RESULTS: A total of 671 cases were observed before and 547 cases were observed after implementation of the computerized surgical safety checklist system. The proportion of cases in which all of the items of the surgical safety checklist were completed significantly increased from 2.1% to 86.3% after the computerized checklist system implementation (P < .001). Before computerized checklist system implementation, 488 of 671 (72.7%) cases had <75% of checklist items completed, whereas after a computerized checklist system implementation, only 3 of 547 (0.5%) cases had <75% of checklist items completed. CONCLUSIONS: The implementation of a computerized surgical safety checklist system resulted in an improvement in checklist performance.

Ultrasound Identification of the Guidewire in the Brachiocephalic Vein for the Prevention of Inadvertent Arterial Catheterization During Internal Jugular Central Venous Catheter Placement.

BACKGROUND: Imaging the guidewire with ultrasonography in the internal jugular vein during central venous catheterization often is used to verify proper guidewire placement and to aid in prevention of inadvertent arterial catheterization. It is known, however, that inadvertent arterial catheterization can occur despite imaging the guidewire in the internal jugular vein because the guidewire may continue through the far wall of the internal jugular vein and into an adjacent artery. We propose confirmation of the guidewire in the brachiocephalic vein with ultrasonography as a more reliable method of confirming proper guidewire placement. METHODS: A prospective feasibility study of 200 adult cardiothoracic surgery patients undergoing internal jugular vein catheterization was performed to determine whether the guidewire could be imaged with ultrasonography in the brachiocephalic vein. The guidewire was imaged in the internal jugular vein in a short-axis view, and the transducer was then angled caudally under the clavicle, following the guidewire into the brachiocephalic vein. RESULTS: The right internal jugular vein was catheterized in 193 patients and the left internal jugular in 7 patients. The brachiocephalic vein was successfully imaged in all but 2 patients. In 3 patients, the guidewire could not be clearly identified in the brachiocephalic vein because of interference from the leads of a heart rhythm device (pacemaker or defibrillator) or preexisting catheter. In 2 patients, the guidewire was not seen initially in the brachiocephalic vein because of coiling in the internal jugular vein, and in 1 patient because of the guidewire passing into the right subclavian vein, but all 3 were subsequently imaged in the brachiocephalic vein after repositioning. CONCLUSIONS: During internal jugular vein catheterization, the brachiocephalic vein was imaged with ultrasonography in 99% of patients (the lower 1-sided 99% confidence limit is 96%). The guidewire was imaged in the brachiocephalic vein in all cases except when leads from a heart rhythm device caused interference, although in some patients with leads, the guidewire could be imaged without difficulty. The absence of the guidewire from the brachiocephalic vein was indicative of a malpositioned guidewire.