What are standard monitoring devices for anesthesia in future?

Monitoring the patient's physiological functions is critical in clinical anesthesia. The latest version of the Japanese Society of Anesthesiologists' Guidelines for Safe Anesthesia Monitoring, revised in 2019, covers various factors, including electroencephalogram monitoring, oxygenation, ventilation, circulation, and muscle relaxation. However, with recent advances in monitoring technologies, the information provided has become more detailed, requiring practitioners to update their knowledge. At a symposium organized by the Journal of Anesthesia in 2023, experts across five fields discussed their respective topics: anesthesiologists need to interpret not only the values displayed on processed electroencephalogram monitors but also raw electroencephalogram data in the foreseeable future. In addition to the traditional concern of preventing hypoxemia, monitoring for potential hyperoxemia and the effects of mechanical ventilation itself will become increasingly important. The importance of using AI analytics to predict hypotension, assess nociception, and evaluate microcirculation may increase. With the recent increase in the availability of neuromuscular monitoring devices in Japan, it is important for anesthesiologists to become thoroughly familiar with the features of each device to ensure its effective use. There is a growing desire to develop and introduce a well-organized, integrated "single screen" monitor.

Influence of the Pringle maneuver during partial hepatectomy on the neuromuscular block induced by intermittent and continuous dosing of rocuronium.

PURPOSE: The Pringle maneuver (PM) is a common procedure in hepatectomy that is known to interrupt drug elimination. The purpose of this study was to examine the influence of PM on the duration of action of rocuronium administered by intermittent bolus dosing, the continuous rocuronium infusion dose required for maintenance of a moderate neuromuscular block, and changes in plasma concentrations of rocuronium. METHODS: Twenty-seven adult patients undergoing partial hepatectomy with PM were enrolled in this study. The duration of action of 0.2 mg/kg rocuronium boluses (DUR), and the continuous rocuronium infusion dose required for maintenance of the height of the first twitch of the train-of-four (T1) at 10-20% of the control value (%T1), respectively, were electromyographically monitored on the adductor digiti minimi muscle. The effects of PM on DUR, %T1, and the plasma concentration of rocuronium were measured. RESULTS: The DUR was significantly prolonged during PM [mean: 42.2 (SD: 8.0) min, P < 0.001] compared to baseline [29.7 (6.3) min]. It was prolonged even after completion of the PM [46.2 (10.5) min, P < 0.001]. The plasma concentration of rocuronium measured at every reappearance of T1 was comparable between before and during PM. %T1 [15.5 (5.6)%] was significantly depressed after the start of PM [6.5 (3.9)%, P < 0.001], with persistence of the depression even after completion of PM. However, there were no significant changes in the plasma concentration of rocuronium. CONCLUSIONS: Rocuronium-induced neuromuscular block is significantly augmented during PM. However, the augmentation is not associated with an increase in plasma rocuronium concentration.

Postoperative prosthetic mitral valve occlusion due to left atrial thrombus during veno-arterial extracorporeal membrane oxygenation: a case report.

BACKGROUND: Anticoagulation using heparin is generally used to prevent thrombus formation during mechanical circulatory support, such as veno-arterial extracorporeal membrane oxygenation (VA-ECMO). However, during the early period following cardiac surgery, anticoagulation becomes more difficult due to the greater risk of critical bleeding complications. CASE PRESENTATION: A 71-year-old man presented with acute prosthetic valve occlusion caused by left atrial thrombus formation and bioprosthetic valve thrombosis during peripheral VA-ECMO following mitral valve replacement (MVR) despite continuous heparin administration and loading of antiplatelet agents. The VA-ECMO flow rate decreased 10 h after the intensive care unit (ICU) admission after MVR. Exploratory transesophageal echocardiography (TEE) examination revealed a left atrial thrombus, prosthetic valve obstruction by the thrombus, and an intrapericardial hematoma. CONCLUSIONS: Intracardiac thrombus formation might occur during VA-ECMO despite appropriate anticoagulation and loading of antiplatelet agents. Exploratory TEE examination was helpful in the detection of intra-atrial thrombus formation after cardiac surgery and surgical decision-making.

Comparison of two electromyography-based neuromuscular monitors, AF-201P and TetraGraph, in rocuronium-induced neuromuscular block: A prospective comparative study.

BACKGROUND: The study aimed to compare the responses obtained simultaneously from the newly developed electromyography (EMG)-based neuromuscular monitors, AF-201P and TetraGraph™, during rocuronium-induced neuromuscular block. METHODS: Twenty patients were enrolled in this study. During total intravenous general anesthesia, train-of-four (TOF) responses following 0.9-mg/kg-rocuronium administration were monitored at the abductor digiti minimi muscle with AF-201P and TetraGraph on the contralateral arms. Sugammadex 2 mg/kg was administered when both devices showed TOF counts (TOFC) = 2. The primary outcome was time from rocuronium administration to the first appearance of the post-tetanic count (PTC) response (first PTC). The secondary outcomes were supramaximal current, baseline compound muscle action potential, onset time, time to TOFC = 1, time to TOFC = 2, and time from sugammadex administration to TOF ratio ≥ 0.9. We used the paired t-test and Wilcoxon signed-rank test to analyze parametric and non-parametric data, respectively. P < 0.05 defined statistical significance. RESULTS: A total of 19 patients were analyzed. The supramaximal current was significantly lower with AF-201P than TetraGraph (31.7 ± 13.2 vs. 43.2 ± 8.2, p = .002). The time to first PTC (24.9 ± 9.4 vs. 27.3 ± 8.9 min, p = .026), time to TOFC = 1 (42.3 ± 9.0 vs. 45.1 ± 10.4 min, p = .03), and time to TOFC = 2 (52.0 ± 10.5 vs. 54.6 ± 11.7 min, p = .014) were significantly faster with AF-201P than with TetraGraph. There were no significant differences in the other outcomes between the devices. CONCLUSIONS: AF-201P showed faster recovery of rocuronium-induced neuromuscular block compared with TetraGraph.

A comparison between the adductor pollicis muscle and the abductor digiti minimi muscle using electromyography AF-201P in rocuronium-induced neuromuscular block: a prospective comparative study.

BACKGROUND: The AF-201P, a new electromyography (EMG)-based neuromuscular monitor has been developed recently. The aim of this clinical study was to compare two ulnar nerve innervated muscles: the adductor pollicis (AP) muscle and the abductor digiti minimi (ADM) muscle during the recovery from rocuronium-induced neuromuscular block by using EMG AF-201P. METHODS: Twenty patients undergoing surgery with general anesthesia were enrolled in the study. During total intravenous general anesthesia, train-of-four (TOF) and post-tetanic counts (PTC) responses following 0.9 mg/kg rocuronium administration were concurrently monitored at the AP and the ADM muscles with EMG AF-201P on the opposite arms. At the end of the surgery, sugammadex 2 mg/kg was administered when TOF counts of 2 (TOFC2) was observed at both muscles. The primary outcome of the study was time from administration of rocuronium to first appearance of PTC response (first PTC). The secondary outcomes of the study were time from administration of rocuronium to TOF count of 1 (TOFC1), time from first PTC to TOFC1 (PTC-TOF time), time to TOFC2, and time from administration of sugammadex to TOF ratio ≥ 0.9. Agreement between the two muscles was assessed using the Bland-Altman analysis. Data are expressed as mean ± standard deviation. RESULTS: Nineteen patients were included in the analysis. Time to first PTC was significantly faster at the ADM muscle than the AP muscle (24.4 ± 11.4 min vs 32.4 ± 13.1 min, p = 0.006). PTC-TOF time was significantly longer with the ADM muscle than the AP muscle (19.4 ± 7.3 min vs 12.4 ± 10.6 min, p = 0.019). There were no significant differences in time to TOFC2 and sugammadex-facilitated recovery between the two muscles. Bland-Altman analyses showed acceptable ranges of bias and limits of agreement of the two muscles. CONCLUSIONS: The ADM muscle showed a good agreement with the AP muscle during rocuronium-induced neuromuscular block but faster recovery of PTC response when using EMG. TRIAL REGISTRATION: UMIN-CTR (Registration No. UMIN000044904 ). Registered 19 July 2021 -Retrospectively registered, https://center6.umin.ac.jp/cgi-bin/ctr_e/ctr_view.cgi?recptno=R000051290 .

A Comparison Between the Adductor Pollicis Muscle Using TOF-Watch SX and the Abductor Digiti Minimi Muscle Using TetraGraph in Rocuronium-Induced Neuromuscular Block: A Prospective Observational Study.

BACKGROUND: The commonly used acceleromyography (AMG)-based neuromuscular monitor TOF-Watch SX is no longer manufactured. Recently, a new portable electromyography (EMG)-based neuromuscular monitor TetraGraph was introduced in clinical anesthesia. The aim of the study was to compare the responses obtained simultaneously from the abductor digiti minimi (ADM) muscle with TetraGraph and the adductor pollicis (AP) muscle with TOF-Watch SX during rocuronium-induced neuromuscular block. METHODS: Patients undergoing orthopedic surgery with general anesthesia were enrolled in this prospective, observational study. During total intravenous general anesthesia, train-of-four (TOF) responses following 0.9-mg·kg -1 rocuronium administration were monitored at the AP muscle with TOF-Watch SX and the ADM muscle with TetraGraph on the opposite arms. Sugammadex 2 mg·kg -1 was administered when both devices showed TOF counts (TOFCs) = 2. The primary outcome was time from rocuronium administration to first appearance of posttetanic count (PTC) response (first PTC). The secondary outcomes were baseline TOF ratios (TOFRs), onset time, time to first reappearance of TOFC = 1 (time to TOFC1), time to first reappearance of TOFC = 2 (time to TOFC2), and time from sugammadex administration to TOFR ≥0.9 with TetraGraph or to normalized TOFR ≥0.9 with TOF-Watch SX (recovery time). We used paired t test and Wilcoxon signed-rank test to analyze parametric and nonparametric data, respectively. P <.05 defined statistical significance. RESULTS: A total of 20 patients were analyzed. The baseline TOFRs were significantly higher with TOF-Watch SX than with TetraGraph (105 [96-110] vs 100 [98-101]; P = .0002). The time to first PTC (minutes) (31.7 ± 9.6 vs 41.1 ± 12.3; P < .001), time to TOFC1 (minutes) (48.0 ± 12.7 vs 58.8 ± 19.2; P < .001), time to TOFC2 (minutes) (56.2 ± 15.7 vs 74.2 ± 23.7; P < .001), and recovery time (seconds) (61.5 [32-148] vs 75.5 [94-102]); P = .043) were significantly faster with TOF-Watch SX than with TetraGraph. There were no significant differences in onset time. CONCLUSIONS: TOF-Watch SX overestimated recovery from rocuronium-induced neuromuscular block compared with TetraGraph.

Comparison of a new EMG module, AF-201P, with acceleromyography using the post-tetanic counts during rocuronium-induced deep neuromuscular block: a prospective, multicenter study.

Recent advances in neuromuscular monitors have facilitated the development of a new electromyographic module, AF-201P™. The purpose of this study was to investigate the relationship between post-tetanic counts (PTCs) assessed using the AF-201P™ and the acceleromyographic TOF Watch SX™ during rocuronium-induced deep neuromuscular block. Forty adult patients consented to participate in this study. The integrated AF-201P™ stimulating and sensing electrode was placed over the ulnar nerve on the distal volar forearm and the belly of the abductor digiti minimi muscle of one arm. The TOF Watch SX™ was applied with the provided hand adaptor on the opposite arm, to observe twitch responses of the adductor pollicis muscle. After stabilization of train-of-four (TOF) responses, rocuronium 0.9 mg kg-1 was administered intravenously. Then, PTCs were observed every 3 min using both monitors. Whenever the TOF count was detected with the TOF Watch SX™, rocuronium 0.2 mg kg-1 was administered, and successive PTC measurements were continued. A total of 1732 paired PTC data points were obtained and analyzed. Regression analysis showed no significant difference in PTCs between the two monitors (PTCs measured by the TOF Watch SX™ = 0.78·PTCs measured by AF-201P™ + 0.21, R = 0.56). Bland-Altman analysis also showed acceptable ranges of bias [95% CI] and limits of agreement (0.3 [0.2 to 0.5] and - 4.6 to 5.3) for the PTCs. The new EMG module, AF-201P™, showed reliable PTCs during deep neuromuscular block, as well as the TOF Watch SX™.

Plasma rocuronium concentration in cell salvage blood following cardiac surgery: a case series.

PURPOSE: The aim of the study was to evaluate the plasma rocuronium concentration in autologous blood transfusion obtained from the cell salvage (CS) system following cardiac surgery with cardiopulmonary bypass (CPB). METHODS: This prospective observational study was conducted in a university teaching hospital from July to November 2020. Patients undergoing general anesthesia for cardiac surgery with CPB were enrolled in the study. After separation from CPB, residual blood remaining in the extracorporeal system was collected as the control sample. The second sample (CS blood) was collected from the autologous blood transfusion obtained after completion of the CS system with Cell Saver® Elite®. Hematocrit values of both samples were also examined. RESULTS: Ten subjects (aged 57-86 years) were enrolled in this study. Plasma rocuronium concentrations (ng/ml) were significantly lower in the CS blood (94.0 ± 77.5) compared to the control (2950 ± 812.2) (p = 0.002). Hematocrit values (%) were significantly higher in the CS blood (75.2 ± 11.3) compared to the control (40.2 ± 10.2) (p = 0.002). CONCLUSION: Autologous blood transfusion obtained from CS system following cardiac surgery with CPB, only retained a small amount of plasma rocuronium concentration, therefore, the risk of autologous blood transfusion contributing to clinically relevant residual neuromuscular blockade postoperatively should be considered to be low. TRIAL REGISTRATION: This trial was registered in the University Hospital Medical Information Network under registration number UMIN000040877 (registration date; June 24, 2020).

Extravascular leakage of induction doses of rocuronium: four cases in which both depth of neuromuscular block and plasma concentration of rocuronium were assessed.

The duration of action of extravasated rocuronium varies depending on the patient's comorbidities. In patients who receive high doses of non-depolarizing neuromuscular blocking agents subcutaneously, anesthesiologists should be aware of unexpected prolongation of the progress and recovery of neuromuscular block. In such cases, the depth and recovery of neuromuscular block should be objectively monitored to avoid residual neuromuscular block and recurarization.

High-dose rocuronium-induced paralysis of the adductor pollicis muscle facilitates detection of the timing for tracheal intubation in elderly patients: a randomized double-blind study.

PURPOSE: To prevent coughing related to tracheal intubation and the resultant exposure of intubating staff to the patients' expiratory aerosols, the timing of tracheal intubation needs to be precisely predicted. The aim of this study was to evaluate the hypothesis that the timing for safe tracheal intubation in elderly patients can be determined by acceleromyographically monitoring paralysis of the adductor pollicis muscle when high-dose rocuronium, given to block the respiratory muscles, is administered. METHODS: Forty elderly (65-92 years) patients were enrolled in this study and randomly assigned to two groups, to receive rocuronium 0.6 mg/kg or 1 mg/kg. After induction of anesthesia and observing acceleromyographic train-of-four (TOF) responses of the adductor pollicis muscle to ulnar nerve stimulation, the patients randomly received either dose of rocuronium. The onset times from rocuronium administration to TOF counts of 0 were measured. Soon thereafter, a single anesthesiologist who was blinded to the allocated dose of rocuronium performed laryngoscopy and tracheal intubation, and assessed intubating conditions. Data were analyzed by the unpaired t-test and Chi-squared test. RESULTS: The averaged [SD] onset time of neuromuscular blockade was significantly shorter with 1 mg/kg than 0.6 mg/kg rocuronium (104.3 [30.1] s vs. 186.8 [37.5] s, p < 0.001). Patients who received 0.6 mg/kg rocuronium variously showed either poor (n = 9) or good (n = 11) intubating conditions. However, all patients who received 1 mg/kg rocuronium had excellent intubating conditions. CONCLUSIONS: If 1 mg/kg rocuronium is administered, a TOF count of 0 acceleromyographically observed at the adductor pollicis muscle can reveal the adequate timing for tracheal intubation.

Potency estimation of sugammadex for the reversal of moderate rocuronium-induced neuromuscular block: a non-randomized dose-response study.

PURPOSE: There is no report investigating the precise potency of sugammadex for antagonizing various intensities of rocuronium-induced neuromuscular block. The aim of this study was to evaluate the ED95 of reversibility of sugammadex and reveal the safety factor of 2 mg/kg of sugammadex for moderate rocuronium-induced neuromuscular block. METHODS: Fifteen patients were enrolled in this study. After induction of anesthesia, we recorded the adductor pollicis muscle response to ulnar nerve stimulation using acceleromyography. All patients received 0.6 mg/kg rocuronium. When the first twitch (T1) of the train-of-four (TOF) response reappeared, rocuronium infusion was commenced to maintain T1 at 10% of the control. After the surgery was completed and infusion of rocuronium was stopped, patients were given sugammadex by a cumulative dose technique. The effective doses of sugammadex that led to recovery of the amplitude of T1 and the TOF ratio by 95% (ED95) were calculated from the regression lines of least-squares regression analysis. RESULTS: The mean ED95 of sugammadex for recovery of T1 and the TOF ratio from rocuronium-induced moderate neuromuscular block was 1.34 (0.24) and 1.14 (0.24) mg/kg, respectively. CONCLUSIONS: The ED95 of sugammadex for the recovery of T1 was significantly greater than that for the TOF ratio. However, a sugammadex dose of 2 mg/kg is equivalent to about 1.5 times the ED95 of sugammadex for reversal of moderate rocuronium-induced block, indicating its safety margin.

The Utility of Point-of-Care Transesophageal Echocardiography in the Intensive Care Unit for Detecting the Cause of Hemolytic Anemia After Ascending Aorta Replacement.

Hemolysis is well-known as a complication after mitral valve surgery, and hemolytic anemia after valvular surgery in the intensive care unit (ICU) usually leads ICU physicians to a careful imaging examination. However, hemolytic anemia following aortic replacement rarely has been described and little is known. The authors present a patient with hemolytic anemia after ascending aortic replacement for type A aortic dissection repair. In the patient, transthoracic echocardiography (TTE), contrast-enhanced computed tomography (CT), and laboratory tests failed to identify the cause of hemolytic anemia. Transesophageal echocardiography (TEE) finally revealed a stenosis of the proximal anastomosis of the graft, with turbulent flow due to protrusion into the lumen. This finding was thought to represent the cause of hemolysis and was sufficient to convince the surgeons to repair the lesion. In the repair surgery, inversion of the inner felt strip that had been applied to the proximal anastomosis of the replacement ascending aorta was confirmed as shown with TEE, and the constricted anastomosis was repaired. Although TTE and CT generally have been used to identify the lesion of mechanical hemolysis after cardiac surgery, point-of-care TEE could have promptly identified the causative lesion in the present patient. Point-of-care TEE in the ICU could become a first-line imaging examination for postoperative hemolysis in cardiac patients.

Effect of Right-Lateral Versus Left-Lateral Tilt Position on Compression of the Inferior Vena Cava in Pregnant Women Determined by Magnetic Resonance Imaging.

BACKGROUND: Despite the existing dogma that women undergoing cesarean delivery under spinal anesthesia should be positioned with a 15° left-lateral tilt, the patients were actually positioned in a right-lateral tilt position in several of the original studies. The superiority of right versus left positioning for optimal inferior vena cava volume is unknown. We used magnetic resonance imaging to compare the effects of right-lateral and left-lateral tilt positions on abdominal aortic and inferior vena cava volumes in pregnant women. METHODS: Thirteen women with singleton pregnancies and gestational age 31-39 weeks underwent magnetic resonance imaging while in the supine position, and in the left-lateral (15° and 30°) and right-lateral tilt (15° and 30°) positions, which were maintained by placing a 1.5-m-long piece of polyethylene foam under either side of the body. Abdominal aorta and inferior vena cava volume were measured between the L1-L2 disk and L3-L4 disk levels using magnetic resonance images. RESULTS: Aortic volume did not differ significantly among any of the positions examined. Mean inferior vena cava volume was significantly greater in the 30° left-lateral tilt position than in the 15° right-lateral tilt (10.7 ± 7.5 vs 5.9 ± 5.1 mL; mean difference, 4.8; 95% CI, 1.2-8.5; P = .002) and 30° right-lateral tilt (10.7 ± 7.5 vs 5.9 ± 2.5 mL; mean difference, 4.8; 95% CI, 1.2-8.4; P = .002) positions. Mean inferior vena cava volume in the 15° left-lateral tilt position did not differ significantly from that in the 15° right-lateral tilt (mean difference, 0.4; 95% CI, -3.2 to 4.0; P = 1.000) or 30° right-lateral tilt (mean difference, 0.4; 95% CI, -3.3 to 4.0; P = 1.000) positions. Mean inferior vena cava volume in the supine position only differed significantly from that in the 30° left-lateral tilt position (5.2 ± 3.8 vs 10.7 ± 7.5 mL; mean difference, 5.5; 95% CI, 1.8-9.1; P < .001). The greatest inferior vena cava volume was observed in the 30° left-lateral tilt position in 9 of 13 subjects (70%), and in the 30° right-lateral tilt in 3 subjects (23%). CONCLUSIONS: The 30° left-lateral tilt position most consistently reduced inferior vena cava compression by the gravid uterus compared with the supine position. Mean inferior vena cava volume in pregnant women was not increased at either angle of the right-lateral tilt position compared with the 30° left-lateral tilt position. However, in a subset of patients, the 30° right-lateral tilt position achieved the optimal inferior vena cava volume. Further investigation to understand this variability is warranted.

Efficiency of the TOF-Cuff™ for the evaluation of rocuronium-induced neuromuscular block and its reversal with sugammadex: a comparative study vs. acceleromyography.

PURPOSE: The aim of this study was to compare TOF-Cuff™ (TOF-C) and TOF-Watch™ (TOF-W) data following rocuronium-induced neuromuscular block and its reversal with sugammadex. METHODS: Twenty elderly patients aged 68-82 years scheduled for surgery under general anesthesia were enrolled in this study. After induction of anesthesia, neuromuscular block resulting from administration of 0.6 mg/kg rocuronium was concurrently evaluated using TOF-C and TOF-W. The onset of neuromuscular block and duration until the first twitch response following post-tetanic count (PTC) and 2 Hz train-of-four (TOF) stimulation reappeared were evaluated. When the response to the TOF stimulus was detected with both monitors, additional doses of rocuronium were administered to maintain the neuromuscular block. After surgery, 2 mg/kg sugammadex was administered when 1-2 TOF twitches were observed with the TOF-W and the time required for facilitated recovery to a TOF ratio of > 0.9 was assessed. RESULTS: Regression analyses revealed no statistically significant differences in the mean [SD] onset of rocuronium-induced neuromuscular block [127.8 (27.2) s, 123.5 (30.5) s], time to recovery of the first PTC twitch [23.9 (8.0) min, 25.4 (8.6) min], time to recovery of the first twitch with TOF stimulation [37.2 (8.8) min, 38.9 (11.1) min] and time to adequate reversal with sugammadex [139.2 (30.6) s, 151.8 (31.5) s] between TOF-C and TOF-W, respectively. Bland-Altman analyses also showed acceptable ranges of the biases and limits of agreement between the two methods. CONCLUSIONS: TOF-C may be clinically applicable for the evaluation of both the depth of neuromuscular block and restoration of neuromuscular function.

A case series of re-establishment of neuromuscular block with rocuronium after sugammadex reversal.

We report the use of rocuronium to re-establish neuromuscular block after reversal with sugammadex. The aim of this study was to investigate the relationship between the dose of rocuronium needed to re-establish neuromuscular block and the time interval between sugammadex administration and re-administration of rocuronium. Patients who required re-establishment of neuromuscular block within 12 h after the reversal of rocuronium-induced neuromuscular block with sugammadex were included. After inducing general anesthesia and placing the neuromuscular monitor, the protocol to re-establish neuromuscular block was as follows. An initial rocuronium dose of 0.6 mg/kg was followed by additional 0.3 mg/kg doses every 2 min until train-of-four responses were abolished. A total of 11 patients were enrolled in this study. Intervals between sugammadex and second rocuronium were 12-465 min. Total dose of rocuronium needed to re-establish neuromuscular block was 0.6-1.2 mg/kg. 0.6 mg/kg rocuronium re-established neuromuscular block in all patients who received initial sugammadex more than 3 h previously. However, when the interval between sugammadex and second rocuronium was less than 2 h, more than 0.6 mg/kg rocuronium was necessary to re-establish neuromuscular block.

Effect of lateral tilt angle on the volume of the abdominal aorta and inferior vena cava in pregnant and nonpregnant women determined by magnetic resonance imaging.

BACKGROUND: Left-lateral tilt position is used to reduce assumed aortocaval compression by the pregnant uterus. METHODS: Magnetic resonance images of 10 singleton parturients at full term and 10 healthy nonpregnant women were obtained for measurement of the abdominal aorta and inferior vena cava volume between the L1-L2 disk and L3-L4 disk levels in both the supine and left-lateral tilt positions (15°, 30°, and 45°) maintained by insertion of a 1.5-m-long polyethylene foam placed under the right side of the parturient's body. RESULTS: Aortic volume did not differ significantly between parturients and nonpregnant women in the supine position (12.7 ± 2.0 vs.12.6 ± 2.1 ml, mean ± SD; mean difference, -0.1; 95% confidence interval [CI], -2.0 to 1.9; P = 0.95). Inferior vena cava volume in the supine position was significantly lower in parturients than in nonpregnant women (3.2 ± 3.4 vs.17.5 ± 7.8 ml; mean difference, 14.3; 95% CI, 8.3-20.2; P < 0.001). Aortic volume in parturients did not differ among left-lateral tilt positions. Inferior vena cava volume in the parturients was not increased at 15° (3.0 ± 2.1 ml; mean difference, -0.2; 95% CI, -1.5 to 1.2; P > 0.99), but was significantly increased at 30° (11.5 ± 8.6 ml; mean difference, 8.3; 95% CI, 2.3-14.2; P = 0.009) and 45° (10.9 ± 6.8 ml; mean difference, 7.7; 95% CI, 2.2-13.1; P = 0.015). CONCLUSIONS: In parturients, the aorta was not compressed, and a 15° left-lateral tilt position did not effectively reduce inferior vena cava compression.

Reversal with sugammadex in the absence of monitoring did not preclude residual neuromuscular block.

BACKGROUND: In Japan, routine clinical care does not normally involve the use of a monitoring device to guide the administration of neuromuscular blocking drugs or their antagonists. Although most previous reports demonstrate that sugammadex offers more rapid and reliable antagonism from rocuronium-induced neuromuscular blockade, this advantage has not been confirmed in clinical settings when no neuromuscular monitoring is used. In this multicenter observational study, we sought to determine whether sugammadex reduces the incidence of postoperative residual weakness compared with neostigmine when the administration of rocuronium and its antagonists is not guided by neuromuscular monitoring. METHODS: This study was conducted in two 5-month periods that preceded and followed the introduction of sugammadex into clinical practice in Japan. Five university-affiliated teaching hospitals participated in this study. Neostigmine was used to antagonize rocuronium-induced neuromuscular blockade in the first phase, and sugammadex was used in the second phase. The timing and doses of rocuronium, neostigmine, and sugammadex were determined by the attending anesthesiologists without the use of neuromuscular function monitoring devices. To ascertain the incidence of postoperative residual neuromuscular weakness, the train-of-four ratio (TOFR) was determined acceleromyographically after tracheal extubation. Since our practice also does not usually involve calibration and normalization of accelerographic responses, both TOFR <0.9 and TOFR <1.0 were used as the criteria for defining postoperative residual weakness. RESULTS: In the first phase, 109 patients received neostigmine (average dose 33 µg/kg) and 23 patients were considered (by clinical criteria) to have adequate recovery and did not receive neostigmine (spontaneous recovery group). In the second phase, 117 patients received sugammadex (average dose 2.7 mg/kg) for antagonism of rocuronium-induced blockade. The incidence (95% confidence interval) of TOFR <0.9 under spontaneous recovery, after neostigmine, and after sugammadex, was 13.0% (2.8%-33.6%), 23.9% (16.2%-33.0%), and 4.3% (1.7%-9.4%), respectively. The incidence (95% confidence interval) of TOFR <1.0 in these groups was 69.6% (47.1%-86.6%), 67.0% (57.3%-75.7%), and 46.2% (36.9%-55.6%), respectively. The use of sevoflurane in the neostigmine group and the short interval between the administration of the last doses of rocuronium and sugammadex were associated with a higher incidence of postoperative residual weakness. CONCLUSIONS: This study demonstrated that the risk of TOFR <0.9 after tracheal extubation after sugammadex remains as high as 9.4% in a clinical setting in which neuromuscular monitoring (objective or subjective) was not used. Our finding underscores the importance of neuromuscular monitoring even when sugammadex is used for antagonism of rocuronium-induced neuromuscular block.

Distribution of epidural saline upon injection and the epidural volume effect in pregnant women.

BACKGROUND: How injected epidural solution is distributed and affects the epidural volume in pregnant women are unclear. METHODS: Lumbar epidural catheters were placed using the loss-of-resistance technique with saline in eight full-term (39 weeks' gestation) parturients for labor and eight volunteer nonpregnant women. Lumbosacral cerebrospinal fluid volume was measured on thoracic and lumbosacral axial magnetic resonance images. Another image series was obtained after injecting 10 ml saline into the epidural space through the catheter to compare the saline distribution (dural sac coating and exit from foramina) and cerebrospinal fluid volume before and after epidural injection. Dural sac coating was based on observation of epidural saline in the anterior epidural space after injection in axial magnetic resonance images at the pedicle levels from T12 to L5. Saline leakage from the foramina was determined by the same method at six disc levels from T11-T12 to L4-L5. RESULTS: Significantly fewer images of pregnant women than nonpregnant women showed saline surrounding the dural sac (0 [0-0] vs. 3 [1-4], median [interquartile range]; P < 0.01) and saline leakage from the foramina (0 [0-1] vs. 6 [4-6]; P < 0.01). The mean reduction in cerebrospinal fluid volume was significantly greater in pregnant (8.4 ± 1.4 ml; mean ± SD) than in nonpregnant women (4.6 ± 1.1 ml; P < 0.001). CONCLUSION: Limited dural sac coating and decreased leakage from the foramina of saline injected into the epidural space may account for the facilitation of longitudinal spread of epidural analgesia in pregnant women. The epidural volume effect is greater in pregnant than in nonpregnant women.