Facemask ventilation and vocal cord angle following neuromuscular blockade: a prospective observational study#

Numerous studies support the idea that neuromuscular blockade facilitates facemask ventilation after induction of anaesthesia. Although improved airway patency or pulmonary compliance and a resolution of laryngospasm have been suggested as possible causes, the exact mechanism remains unclear. We aimed to assess whether neuromuscular blockade improves facemask ventilation and to clarify whether this phenomenon is associated with the vocal cord angle. This prospective observational study included patients aged between 20 and 65 years scheduled for elective surgery under general anaesthesia. After induction of anaesthesia, patients' lungs were ventilated with pressure-controlled ventilation using a facemask. During facemask ventilation, a flexible bronchoscope was inserted through a self-sealing diaphragm at the elbow connector attached to the facemask and breathing circuit and positioned to allow a continuous view of the vocal cords. The mean tidal volume and vocal cord angle were measured before and after administration of neuromuscular blocking drugs. Of 108 patients, 100 completed the study. Mean (SD) tidal volume ((11.0 (3.9) ml.kg^-1 vs. 13.6 (2.6) ml.kg^-1; p < 0.001) and mean (SD) vocal cord angle (17° (10°) vs. 26° (5°); p < 0.001) increased significantly after neuromuscular blockade. The proportional increase in mean tidal volume after neuromuscular blockade was positively correlated with vocal cord angle (Spearman's ρ = 0.803; p < 0.001). In conclusion, neuromuscular blockade facilitated facemask ventilation, and the improvement was correlated with further opening of the vocal cords.     

The DIFFMASK score for predicting difficult facemask ventilation: a cohort study of 46,804 patients

Facemask ventilation is an essential part of airway management. Correctly predicting difficulties in facemask ventilation may reduce the risk of morbidity and mortality among patients at risk. We aimed to develop and evaluate a weighted risk score for predicting difficult facemask ventilation during anaesthesia. We analysed a cohort of 46,804 adult patients who were assessed pre-operatively airway for 13 predictors of difficult airway management and subsequently underwent facemask ventilation during general anaesthesia. We developed the Difficult Facemask (DIFFMASK) score in two consecutive steps: first, a multivariate regression analysis was performed; and second, the regression coefficients of the adjusted regression model were converted into a clinically applicable weighted point score. The predictive accuracy of the DIFFMASK score was evaluated by assessment of receiver operating characteristic curves. The prevalence of difficult facemask ventilation was 1.06% (95%CI 0.97–1.16). Following conversion of regression coefficients into 0, 1, 2 or 3 points, the cumulated DIFFMASK score ranged from 0 to 18 points and the area under the receiver operating characteristic curve was 0.82. The Youden index indicated a sum score ≥ 5 as an optimal cut-off value for prediction of difficult facemask ventilation giving a sensitivity of 85% and specificity of 59%. The DIFFMASK score indicated that a score of 6–10 points represents a population of patients who may require heightened attention when facemask ventilation is planned, compared with those patients who are obviously at a high- or low risk of difficulties. The DIFFMASK score may be useful in a clinical context but external, prospective validation is needed.     

术后非去极化肌松药肌松残余拮抗新进展

背景非去极化肌松药在临床麻醉中使用非常普遍,术后不可避免地发生肌松残余作用,其危害主要为呼吸不良事件,严重可导致死亡。 目的有效合理的肌松拮抗能降低术后肌松残余的发生率,减少相关并发症,因此,拮抗至关重要。内容阐述非去极化肌松药使用后手术结束时是否需要拮抗、拮抗的时机、拮抗剂的剂量和新的拮抗模式。趋向选择性肌松拮抗可...     

Sedation and neuromuscular blockade in paediatric intensive care: a review of current practice in the UK

BACKGROUND: Our aim was to investigate the current practice of sedation and neuromuscular blockade in critically ill children in paediatric intensive care units (PICUs) in the UK. METHODS: A postal questionnaire was sent to all PICUs in the UK. RESULTS: The most commonly used sedative agents were midazolam in combination with morphine. Written clinical guidelines for the sedation of critically ill children were available in 45% of units. Sedation is formally assessed in 40% of units. Vecuronium is the most commonly used neuromuscular blocking agent. In the UK, 31% of critically ill children are likely to receive neuromuscular blocking agents. Depth of neuromuscular blockade is routinely assessed in 16% of patients. CONCLUSIONS: Relatively few units possess clinical guidelines for the sedation of critically ill children, and only a minority formally assess sedation levels. Where neuromuscular blocking agents are administered, sedation is frequently inadequately assessed and the depth of neuromuscular blockade is rarely estimated.     

In vivo potentiation of atracurium neuromuscular blockade by nimodipine in rabbits

The interaction between nimodipine, a calcium channel blocker, used for the treatment of subarachnoid haemorrhage, and atracurium, was studied in rabbits. An intravenous dose of 0.1 mg.kg-1 of nimodipine given over 3 min caused a potentiation of the neuromuscular blocking action of atracurium (administered at an infusion rate of 7.5 micrograms.kg-1.min-1), measured on the indirectly stimulated tibialis-anterior muscle of the animal. (ED50)inf and (ED95)inf were significantly reduced (30.7% and 23.3%) in nimodipine-treated animals (P less than 0.05 and P less than 0.02, respectively). No changes were observed in recovery rate.     

Rocuronium 0.3 mg x kg-1 (ED95) induces a normal peak effect but an altered time course of neuromuscular block in patients with Duchenne's muscular dystrophy

BACKGROUND: In patients with Duchenne's muscular dystrophy (DMD) recovery from neuromuscular block is delayed. It has been assumed that this is because of a higher potency of muscle relaxants in this patient cohort. We determined the peak effect, and the time course of action of rocuronium 0.3 mg x kg(-1) (ED(95)) in DMD patients. METHODS: Twenty-four patients (12 with DMD and 12 controls; aged 10-18 years) were studied. All patients were anesthetized with propofol and fentanyl/remifentanil. Neuromuscular transmission was monitored by acceleromyography. After induction all patients received a single dose of rocuronium 0.3 mg x kg(-1). The complete time course of action as onset, peak effect and spontaneous recovery was recorded. RESULTS: The onset time (s) to maximum block was significantly (P < 0.01) prolonged in DMD patients (median: 315; range: 120-465) compared with controls (195, 75-270). The peak effect (% twitch depression relative to baseline) was not different between the groups (DMD: 59-100; controls: 28-100). In the DMD group, recovery was significantly (P < 0.01) delayed compared with controls at all recorded time points. The clinical duration (min) was 40.3 (22-89) in the DMD group vs 9.8 (6-17) in the control group (P < 0.01). CONCLUSIONS: The similar peak effect in both groups does not confirm the thesis of rocuronium having a higher potency in DMD patients. The documented very long recovery after the ED(95) of rocuronium emphasizes the need for careful assessment of neuromuscular function in DMD patients.     

Residual neuromuscular blockade in the ICU: a prospective observational study and national survey

Residual neuromuscular blockade is associated with significant morbidity. It has been widely studied in anaesthesia; however, the incidence of residual neuromuscular blockade in patients managed in the ICU is unknown. We conducted a prospective observational study in a tertiary ICU to determine the incidence of residual neuromuscular blockade using quantitative accelerographic monitoring. We tested for residual neuromuscular blockade (defined as a train-of-four ratio < 0.9) before cessation of sedation in anticipation of tracheal extubation. We also surveyed 16 other ICUs in New Zealand to determine their use of neuromuscular monitoring. A total of 191 patients were included in the final analysis. The incidence (95%CI) of residual neuromuscular blockade was 43% (36–50%), with a similar incidence observed in non-postoperative and postoperative patients. There was a lower risk of residual neuromuscular blockade with atracurium than rocuronium (risk ratio (95%CI) of 0.39 (0.12–0.78)) and a higher risk with pancuronium than rocuronium (1.59 (1.06–2.49)). Our survey shows that, in New Zealand ICUs, monitoring of neuromuscular function is rarely carried out before tracheal extubation. When neuromuscular monitoring is undertaken, it is based on individual clinician suspicion and performed using qualitative measurements. No ICU reported using a quantitative monitor or a clinical guideline. The results demonstrate a high incidence of residual neuromuscular blockade in our ICU patients and identify the type of neuromuscular blocking drug as a possible risk factor. Monitoring neuromuscular function before tracheal extubation is not currently the standard of care in New Zealand ICUs. These data suggest that residual neuromuscular blockade may be an under-recognised problem in ICU practice.     

Response to double-burst appears before response to train-of-four stimulation during recovery from non-depolarizing neuromuscular blockade

Background: Double-burst stimulation (DBS) it a relatively new nerve stimulation mode introduced for improved manual detection of residual neuromuscular blockade. Previous studies have shown that DBS_{3,3 50/50} (3 stimuli at 50 Hz followed 0.75 seconds later by 3 stimuli at 50 Hz) can detect deeper degrees of neuromuscular blockade than train-of-four (TOF) stimulation.
Aim: The aim of the present study was to examine if DBS_{3,3 80/40} (3 stimuli at 80 Hz followed 0.750 s later by 3 stimuli at 40 Hz) can detect even deeper degrees of neuromuscular blockade than DBS_{3,3 50/50} and to determine the time lapse from reappearance of response to each of the two DBS modes until reappearance of response to the TOF mode of nerve stimulation.
Methods: The study comprised 20 women undergoing gynaecological surgery and anaesthetised with fentanyl, thiopentone, halothane, and nitrous oxide. Neuromuscular transmission was monitored by using mechanomyography and stimulation of the ulnar nerve. Atracurium was used for neuromuscular blockade.
Results: Elapsed time from reappearance of response to DBS_{3,3 80/40} and DBS_{3,3 50/50} to reappearance of response to TOF stimulation was 459±196 (mean±SD) and 360±150 seconds, respectively, ( P <0.05).
Conclusions: DBS_{3,3 80/40} is capable of detecting deeper degrees of blockade than DBS_{3,3 50/50} which again is capable of detecting deeper degrees of blockade than TOF.     

The effect of neuromuscular blockade on the efficiency of mask ventilation of the lungs

We conducted a two-part study to assess the practice of withholding neuromuscular blockade until the ability to ventilate the lungs using a bag and face mask (mask ventilation) has been established following induction of anaesthesia. The first part of the study consisted of a postal survey (71% response rate) of 188 anaesthetists in the Oxford region to assess their current practice. Thirty per cent of respondents always checked mask ventilation before administering a neuromuscular blocking drug, whereas 39% of respondents (all them consultants) never did this. A further 31% only did so in the case of known or anticipated difficulty with the airway. In the second part of the study, we measured inspired (V(TI)) and expired (V(TE)) tidal volumes before and after neuromuscular blockade in 30 patients undergoing general anaesthesia. The ratio V(TE)/V(TI) was used as a measure of the efficiency of ventilation. There was no difference in V(TE)/V(TI) before [mean (SD) 0.47 (0.13)] and after [0.45 (0.13)] neuromuscular blockade. We conclude that neuromuscular blockade does not affect the efficiency of mask ventilation in patients with normal airways.     

The effect of neuromuscular blockade on mask ventilation

We wished to test the hypothesis that neuromuscular blockade facilitates mask ventilation. In order reliably and reproducibly to assess the efficiency of mask ventilation, we developed a novel grading scale (Warters scale), based on attempts to generate a standardised tidal volume. Following induction of general anaesthesia, a blinded anaesthesia provider assessed mask ventilation in 90 patients using our novel grading scale. The non-blinded anaesthesiologist then randomly administered rocuronium or normal saline. After 2 min, mask ventilation was reassessed by the blinded practitioner. Rocuronium significantly improved ventilation scores on the Warters scale (mean (SD) 2.3 (1.6) vs 1.2 (0.9), p<0.001). In a subgroup of patients with a baseline Warters scale value of >3 (i.e. difficult to mask ventilate; n=14), the ventilation scores also showed significant improvement (4.2 (1.2) vs 1.9 (1.0), p=0.0002). Saline administration had no effect on ventilation scores. Our data indicate that neuromuscular blockade facilitates mask ventilation. We discuss the implications of this finding for unexpected difficult airway management and for the practice of confirming adequate mask ventilation before the administration of neuromuscular blockade.     

Negative pressure ventilation vs. spontaneous assisted ventilation during rigid bronchoscopy: A controlled randomised trial

Background: Ventilation during interventional rigid bronchoscopy (IRB) under general anaesthesia (jet ventilation, positive pressure ventilation and spontaneous assisted ventilation) may offer some difficulties. This study compares the effectiveness during IRB of intermittent negative pressure ventilation (INPV) and spontaneous assisted ventilation (SAV). Methods: Thirty-eight patients submitted to IRB were randomised into two groups: SAV or INPV. All patients received a total intravenous anaesthesia; INPV patients were paralysed. Pre-and intra-operative arterial blood gases and O₂ flow through a rigid bronchoscope were assessed. The endoscopist applying a subjective score evaluated the operating conditions. Results: Patients of the INPV group, as compared to the SAV group, required a lower dosage of fentanyl (2.6 ± 1.8 (μg · kg^?1· h^?1 vs. 6.6 ± 4.8 μg · kg^?1· h^?1), a lower O₂ supply (3.3 ± 2.8 1/min vs. 11.6 ± 3.4 1/min), a shorter recovery time (5.4 ± 2.9 min vs. 9.8 ± 7.1 min) and no manually assisted ventilation (0 ± 0 vs. 1 ± 1.1 nd?/procedure). Intraoperative PaCO₂ was higher in the SAV (8.1 ± 1.3 kPa) than in the INPV group (5.0 ± 1.6 kPa) and intraoperative pH differed in the two groups (7.26 ± 0.05, SAV vs. 7.47 ± 0.08, INPV). Operating conditions, as assessed by a subjective score, were considered better with INPV than with SAV (4.9 vs. 4.3). Conclusions: As compared to SAV, INPV in paralysed patients during IRB reduces administration of opioids, shortens recovery time, prevents respiratory acidosis, excludes the need for manually assisted ventilation, reduces 02 need and affords optimal surgical conditions. INPV appears a safe, non-invasive and effective ventilatory management during IRB.     

A retrospective observational study of neuromuscular monitoring practice in 30,430 cases from six Danish hospitals

Timely application of objective neuromuscular monitoring can avoid residual neuromuscular blockade. We assessed the frequency of objective neuromuscular monitoring with acceleromyography and the last recorded train-of-four ratio in a cohort of Danish patients. We extracted data from all patients receiving general anaesthesia from November 2014 to November 2016 at six hospitals in the Zealand Region of Denmark. Acceleromyography was available in all operating rooms and data were recorded automatically. The primary outcome measure was acceleromyography use in patients receiving neuromuscular blocking agents, divided into non-depolarising agents and succinylcholine only. The dataset included 76,743 cases, of which 30,430 received a neuromuscular blocking drug. Non-depolarising drugs were used in 16,525 (54%) and succinylcholine as the sole drug in 13,905 (46%) cases. Acceleromyography was used in 14,463 (88%) patients who received a non-depolarising neuromuscular blocking drug and in 4224 (30%) receiving succinylcholine alone. Acceleromyography use varied between the departments from 58% to 99% for non-depolarising drugs and from 3% to 79% for succinylcholine alone. The median (IQR [range]) of the last recorded train-of-four ratio before tracheal extubation was 0.97 (0.90–1.06 [0.01–2.20]) when non-depolarising drugs were used, and was less than 0.9 in 22% of cases. The OR for oxygen desaturation was higher with the use of succinylcholine [2.51 (95%CI 2.33–2.70) p < 0.001] and non-depolarising drugs [2.57 (95%CI 2.32–2.84) p < 0.001] as compared with cases where no neuromuscular blockade drug was used. In conclusion, acceleromyography was almost always used in cases where non-depolarising neuromuscular blocking drugs were used, but a train-of-four ratio of 0.9 was not always achieved. Monitoring was used in less than 30% of cases where succinylcholine was the sole drug used.     

The influence of 0.5 % isoflurane on a vecuronium-induced neuromuscular blockade

The influence of adding 0.5% isoflurane to a narcotic-based anaesthesia on the duration of effect and recovery time after repetitive administration of vecuronium was studied in ten healthy patients. The twitch response in the adductor pollicis muscle was recorded after supramaximal train-of-four (TOF) stimulation of the ulnar nerve at the wrist. Prior to endotracheal intubation a bolus dose of vecuronium (0.08 mg/kg b.w.) was given. During surgery repeated injections of vecuronium (0.02 mg/kg b.w.) were administered at a TOF ratio of 0.25. Hand-skin temperature, systolic blood pressure, end-tidal CO2 and isoflurane concentrations were continuously monitored. Before and after 90 min administration of isoflurane, the duration of effect was 21 +/- 4 and 24 +/- 5 min (mean +/- s.d., P less than 0.05) respectively. Corresponding recovery times were 270 +/- 60 and 280 +/- 70 s (n.s.). Skin temperature remained unchanged and systolic blood pressure showed only minor variations. The addition of 0.5% isoflurane to a narcotic-based anaesthesia causes a moderate increase in duration of effect but no change in recovery time from a repetitive vecuronium-induced neuromuscular blockade of 0.02 mg/kg.     

Decrease in functional residual capacity and ventilation homogeneity after neuromuscular blockade in anesthetized preschool children in the lateral position

BACKGROUND: While functional residual capacity (FRC) is reduced in children undergoing general anesthesia, the lateral position leads to an increase in FRC compared with the supine position. The impact of neuromuscular blockade remains unknown. We tested the hypothesis that neuromuscular blockade leads to a decrease in FRC and increase in lung clearance index (LCI) while the application of positive endexpiratory pressure (PEEP) of 6 cmH(2)O leads to a restoration in both parameters. METHODS: After approval of the local Ethics Committee, we studied 18 preschool children (2-6 years) without cardiopulmonary disease, who were scheduled for elective surgery. Anesthesia was standardized using propofol and fentanyl. FRC and LCI were calculated by a blinded observer using a SF6 multibreath washout technique with an ultrasonic transit-time airflow meter (Exhalyzer D). Measurements were taken in the left lateral position (PEEP 3 cmH2O) after 1. intubation with a cuffed tracheal tube, 2. neuromuscular blockade with rocuronium, and 3. the additional application of PEEP (6 cmH2O). RESULTS: Functional residual capacity mean (sd) decreased from 31.6 (4.4) ml.kg(-1) to 27.6 (4.2) ml.kg(-1) (P<0.001) following neuromuscular blockade while the LCI increased from 6.54 (0.6) to 7.0 (0.6) (P相似文献   

The effect of changes in arm temperature on neuromuscular monitoring in the presence of atracurium blockade

This study was designed to investigate the relationship between arm temperature and the degree of blockade as monitored by peripheral nerve stimulation by a comparison of both arms of each patient; one exposed to the environment and the other wrapped to maintain its temperature. The decrease in the temperatures of the exposed arms were significantly more than the wrapped arms. A discrepancy was noted proportional to the temperature difference between the two arms, when the train-of-four counts were compared. A recommendation is made to maintain the temperature of the monitored arm above 32 degrees C.     

残余肌松与全麻术后呼吸功能不全关系的临床研究

目的 了解全麻手术后在麻醉恢复室(postanesthesia care unit,PACU)内呼吸功能不全的发生率,并评估其与残余肌松的关系.方法 择期全麻手术成年患者623例,术后PACU内用4个成串刺激(TOF)监测肌松,按临床指征拔管,根据拔管后即刻测量TOF值将患者分成3组,TOF＞0.9为A组；TOF 0.7～0.9为B组；TOF＜0.7为C组,记录每组出现呼吸功能不全的例数.结果 全麻手术后在PACU内呼吸功能不全的发生率为4.5％,A组患者472例,其中有7例(1.5％)出现呼吸功能不全,B组患者112例,9例(8.0％)出现,C组患者39例,有12例(30.8％)出现,最常见的是低氧血症和上呼吸道梗阻.C组与A组和B组比较及B组与A组比较,出现呼吸功能不全比例明显增高(P＜0.01).结论 存在残余肌松(TOF＜0.9)的患者更易出现术后呼吸功能不全,应加强围手术期肌松监测,掌握恰当的拔管时机.