|Year : 2020 | Volume
| Issue : 2 | Page : 134-139
Do clinical signs of recovery from neuromuscular blockade compare reliably with objective parameters of train-of-four and double burst stimulation: An observational single-center study
Bhavna Hooda1, Rijesh R Unnithan2, Saurabh Sud1, Deepak Dwivedi1, Puja Dudeja3
1 Department of Anaesthesia and Critical Care, Command Hospital (Southern Command), Pune, Maharashtra, India
2 Department of Anaesthesia and Critical Care, Armed Forces Medical College, Pune, Maharashtra, India
3 Preventive and Social Medicine, Armed Forces Medical College, Pune, Maharashtra, India
|Date of Submission||29-Feb-2020|
|Date of Decision||14-Apr-2020|
|Date of Acceptance||02-May-2020|
|Date of Web Publication||19-Sep-2020|
Dr. Saurabh Sud
Department of Anaesthesia and Critical Care, Command Hospital (Southern Command), Pune - 411 040, Maharashtra
Source of Support: None, Conflict of Interest: None
Background: Recovery from neuromuscular blockade is commonly assessed by clinical signs. There exists wide disparity in what is recommended to monitor neuromuscular blockade and routine clinical practice by anesthesiologists. The objective signs of train-of-four (TOF) ratio of >0.9 and double burst stimulation (DBS) ratio of 1.0 indicate adequate neuromuscular function. This study was planned at a tertiary care hospital to evaluate the ongoing practice of assessing neuromuscular recovery employing clinical signs and comparing with simultaneous TOF and DBS values.
Design: A cross-sectional analytical study.
Methodology: A total of 100 consecutive patients undergoing surgical procedures lasting more than 1-h duration under general anesthesia with intermediate acting muscle relaxant were enrolled and data of 60 patients analyzed. After extubation, an independent observer recorded simultaneous TOF and DBS ratio using acceleromyography as the clinical signs of neuromuscular recovery (eye opening, tongue protrusion, head lift, sustained bite, hand grip strength, and ability to cough) were attained.
Statistical Analysis: Statistical analysis was done utilizing SPSS version 20 (SPSS Inc., Chicago IL, USA) software. Continuous variables are expressed as mean (standard deviation) and Pearson's correlation coefficient was applied to study the correlation between the clinical parameters and quantitative measures of neuromuscular recovery.
Results: There was a significant association between ability to retain tongue depressor (sustained bite), absent double vision and ability to cough effectively and TOF and DBS ratios (P < 0.05). None of the clinical signs correlated with TOF ratio >0.9 or DBS ratio of 1.0.
Conclusion: Clinical signs of recovery fail to reliably predict postoperative residual paralysis compared to objective neuromuscular monitoring.
Keywords: Delayed emergence from anesthesia, neuromuscular agents, postanesthesia residual paralysis, train-of-four monitoring
|How to cite this article:|
Hooda B, Unnithan RR, Sud S, Dwivedi D, Dudeja P. Do clinical signs of recovery from neuromuscular blockade compare reliably with objective parameters of train-of-four and double burst stimulation: An observational single-center study. Indian Anaesth Forum 2020;21:134-9
|How to cite this URL:|
Hooda B, Unnithan RR, Sud S, Dwivedi D, Dudeja P. Do clinical signs of recovery from neuromuscular blockade compare reliably with objective parameters of train-of-four and double burst stimulation: An observational single-center study. Indian Anaesth Forum [serial online] 2020 [cited 2020 Oct 24];21:134-9. Available from: http://www.theiaforum.org/text.asp?2020/21/2/134/295324
| Introduction|| |
Since the discovery of curare by Griffith and Johnson in 1942, neuromuscular blocking agents (NMBAs) form an integral part of balanced anesthesia care. However, the use of NMBAs is associated with increased incidence of delayed postoperative recovery and six-fold rise in mortality. Persistence of neuromuscular blockade in the post-anesthesia care unit, i.e. postoperative residual paralysis (PORP), postoperative residual curarization, or residual neuromuscular block (RNMB) is a real problem with an incidence as high as 65%, yet it fails to attract concern among anesthesiologists worldwide. There is a huge discrepancy between what is recommended and what is routinely practiced. Surveys conducted across Europe, the US, Australian, and Singaporean anesthesiologists observed that objective monitoring was done in < 20% patients either due to a lack of intent on the part of the anesthesiologists, unfounded belief that monitoring may be unnecessary in experienced hands or the inability to interpret results.,,,, Recently published RECITE-US study evaluated the burden of PORP and the results were an eye opener with almost 65% showing residual paralysis (train-of-four [TOF] ratio<0.9) and almost 31.0% with TOF ratio below 0.6.
It is a common practice for anesthesiologists at high-volume centers to rely on clinical signs of recovery to assess readiness for reversal and extubation. Clinical signs appear at TOF ratios of 0.65–0.75 and fail to ensure adequate recovery from neuromuscular blockade; resulting in PORP and its adverse events in the post-anesthesia care unit (PACU).
We, therefore, planned to conduct a study at our institute if the currently employed subjective parameters ensure adequate neuromuscular recovery after use of intermediate acting NMBAs, as defined by objective parameters of neuromuscular monitoring (TOF ratio and double burst stimulation [DBS] ratio).
| Methodology|| |
This was a cross-sectional analytical study conducted in a tertiary care hospital of western Maharashtra from January 2017 to December 2017. The inclusion criteria for participation in the study were the age group of 18–65 years, in the American Society of Anesthesiologists physical Status I and II, scheduled for elective surgical procedure lasting more than 60 min under general anesthesia. The exclusion criteria included patients with preexisting neuromuscular disease (myasthenia gravis, peripheral neuropathies, and nerve injuries), electrolyte and acid base imbalances, on potassium or calcium supplements, suffering from hepatic/renal and metabolic function impairment (diabetes) and patients on drugs likely to interfere with neuromuscular transmission (NMT) (aminoglycosides, antiepileptic, antiarrhythmics, and calcium channel blockers). Based on data from other researchers noting an PORP of 32% when no objective means of neuromuscular monitoring was employed versus 1.6% in the TOF-monitored patients, for a power of 90% and beta error of 0.5, a sample size of 60 was required to find significant difference between groups. We enrolled 100 consecutive patients to allow for drop outs based on the exclusion criteria and the nonavailability of the TOF monitor. Patients who satisfied the inclusion criteria were randomly selected from the operation theatre (OT) list. Institutional ethical clearance was obtained and written informed consent was taken from the participants preoperatively. Patients who were hypothermic, with major intraoperative blood loss and patients, who were not extubated, were also excluded. Statistical analysis was done utilizing SPSS version 20 (SPSS Inc., Chicago IL, USA) software. Each parameter was assessed for statistical significance using unpaired t-test and P value with 95% confidence interval (CI) analyzed. Continuous variables are expressed as mean (standard deviation) and Pearson's correlation coefficient was applied to study the correlation between the clinical parameters and quantitative measure of neuromuscular recovery.
All patients underwent routine preanesthetic evaluation and were given tablet alprazolam 0.25 mg orally night before surgery. On arrival in the operation theater, nil per oral status and patency of peripheral line were confirmed. Standard monitoring ensued which included (heart rate, noninvasive blood pressure, peripheral capillary oxygen saturation, electrocardiography [ECG], end tidal carbon dioxide), Bispectral index along with neuromuscular monitor (Datex-Ohmeda S/5™ compact critical care monitor with NMT module) and baseline values were noted.
Procedure of neuromuscular monitoring
All patients were counseled preoperatively about the neuromuscular monitoring technique. Two surface electrodes (ECG electrodes) were placed on volar aspect of forearm – one at proximal flexion crease of wrist and other 3 cm proximal to distal electrode, after cleaning with spirit. After induction and before the administration of muscle relaxant, supramaximal stimulus was measured by applying single twitch stimulus on the ulnar nerve and response of adductor pollicis (thumb) muscle was noted. Pre-relaxant value of TOF and DBS ratio was noted by the principal investigator. Subsequent dosing of relaxant was administered as appropriate by the attending anesthesiologist and the principal investigator had no role dosing of relaxant.
Anesthesia was induced with fentanyl 2 μg/kg and propofol (2–2.5 mg/kg) till the loss of motor response to shoulder shrug. The airway was secured with appropriate size of endotracheal tube after the injection of intermediate duration non-depolarizing muscle relaxant (vecuronium 0.1 mg/Kg/atracurium 0.5 mg/kg/rocuronium 0.5 mg/kg). General anesthesia was maintained with oxygen/nitrous oxide/sevoflurane maintaining minimum alveolar concentration of 1.0–1.2. Additional boluses of relaxant and opioid were given as deemed appropriate by the attending anesthesiologist.
Neuromuscular monitoring after reversal
At the conclusion of the surgery, all the anesthetics were cut off and NMB was reversed with injection neostigmine 50 μg/kg and injection glycopyrrolate 10 μg/kg as per the protocol of our institution. The patients were extubated at the discretion of attending anesthesiologist. In our institute the attending anesthesiologist normally extubates a patient if they are able to open eyes and/or protrude tongue and can generate tidal volume of 5–6 ml/kg. The TOFR and DBS ratio was recorded at this time as TOFR0 and DBS0 by the independent observer (principal researcher). The principal investigator thereafter observed the TOFR and DBS as and when the predecided clinical signs were observed as eye opening corresponding with TOFR1, sustained tongue protrusion as TOFR2, sustained head lift as TOFR3, ability to retain tongue depressor (sustained bite) as TOFR4, hand grip (60% of baseline) as TOFR5, absent double vision as TOFR6 and ability to cough effectively as TOFR7 with simultaneous DBS1–7 recordings. The best of 3 readings at each time point were recorded.
| Results|| |
One hundred patients were enrolled in the study and after excluding the patients based on inclusion criteria and protocol violations due to hypothermia, shivering, unplanned ventilation, unexpected bleeding, etc., 60 patients completed the study and were analyzed [Figure 1].
The baseline demographic and perioperative parameters are presented in [Table 1]. The median TOF count and DBS count at reversal were 3 (1,4) and 1 (0,1), respectively. The median TOF ratio and DBS ratio at extubation was 0.4 (0,1.01) and 0.6 (0.1,1.4), respectively.
The overall incidence of PORP at PACU admission, defined as TOF <0.7 and TOF <0.9 was 26.7% (16 patients) and 73.3% (44 patients), respectively.
The mean TOF and DBS ratios as the clinical signs of recovery of muscle strength appeared were noted [Table 2]. The mean TOF and DBS ratio at clinical sign of tongue depressor test was noted as 0.82±0.08 and 0.89±0.08 respectively. The mean TOF and DBS ratio at achieving 60% grip strength was 0.83 ± 0.10 and 0.91 ± 0.11, respectively. Absent diplopia was noted at mean TOF and DBS ratios of 0.86±.09 and 0.92 ± 0.08, respectively. Ability to cough effectively showed mean TOF and DBS ratio as 0.89 ± 0.05 and 0.96 ± 0.06, respectively.
|Table 2: Train-of-four ratio and double burst stimulation ratio at each clinical standpoint (n=60)|
Click here to view
There was a linear correlation between TOF ratio and DBS3,3 patterns as evaluated by Pearson's correlation coefficient (r = 0.99; P < 0.01) [Table 3]. There was statistically significant correlation was noted for clinical signs namely tongue depressor test, absent diplopia and ability to cough effectively with TOF and DBS ratios (P <0.05).
|Table 3: Correlation of clinical signs with mean train-of-four and double stimulation ratios (n=60)|
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| Discussion|| |
Postoperative residual paralysis is a problem that is believed to be as low as 1% by anesthesiologists worldwide. It was defined almost four decades back as a TOF ratio below 0.7 based on resumption of normal spontaneous respiration with near normal vital capacity and inspiratory force in healthy awake volunteers, and the incidence noted as 42%.
Subsequently, several authors provided evidence of impaired pharyngeal function and genioglossus hypoactivity, swallowing dysfunction, reduced upper esophageal sphincter tone, reduced upper airway volume, and impaired ventilatory drive to hypoxia at a TOF ratio of 0.7 in studies on volunteers.,,
Clinical studies also demonstrated symptoms and signs of muscle weakness (inability to speak, smile, cough, facial weakness, etc.,) and critical respiratory events in the PACU in the form of hypoxemic events, airway obstruction, risk of pulmonary aspiration, delayed extubation, reintubation rates, increased postoperative pulmonary complications, and delayed PACU discharge at TOF ratio below 0.9.,,,,,
With growing body of evidence, PORP, defined now as TOF ratio below 0.9, is now recognized as a problem of significant magnitude with incidence as high as 65%. Debaene et al. observed residual weakness defined as TOF <0.7 at 16% and TOF <0.9 at 45% of a cohort of over 500 patients at PACU admission. A subsequent meta-analysis investigated 24 studies including 3375 patients and NM monitoring done in 24% patients and neuromuscular blockade antagonism in 62.1%, the noted incidence was 12% (TOF < 0.7) and 41% (TOF < 0.9), respectively. Intuitively, PORP depends on myriad of factors namely definition of residual blockade (TOF below 0.7,0.8 or 0.9), method of objective monitoring, time of assessment of residual blockade, type and dose of NMBA, NM monitoring-guided intraoperative dosing of NMBA, type of anesthesia, antagonism of NM blockade, patient factors (renal disease, liver disease, acid–base imbalance, electrolyte imbalance, burns, neuromuscular diseases, age, and hypothermia), and concomitant medications (pyridostigmine, corticosteroids, phenytoin, carbamazepine, antiarrhythmics, calcium channel blockers, aminoglycosides, tetracycline, etc.,). In our study, the incidence of residual paralysis (objective values of TOF of 0.9 and DBS of 1) was 73.3% when clinical signs were employed, similar to earlier studies.
Despite the recognition of PORP as a problem in the PACU for over four decades, anesthesiologists have failed to imbibe this truism with only about 1% acknowledging this as a clinical problem completely at odds with the current evidence. In practice, clinicians are relying on clinical tests alone or less frequently, in tandem with objective measures of neuromuscular monitoring in assessing the residual paralysis. Clinical tests though reproducible and easy to perform, but have serious limitations, as they depend on cooperation of patient, level of patient's sedation/consciousness and their ability to comprehend and perform these tests. Further, these do not correlate well with recovery from neuromuscular blockade as many patients who are able to perform clinical tests, may have substantial RNMB.,
TOF and DBS are the most commonly employed objective tests to detect the degree of recovery from neuromuscular blockade in the postoperative period. DBS has now slowly replaced qualitative TOF due to its increased sensitivity in detecting PORP.,, Just like the clinical criteria fail to recognize PORP in a vast majority of patients, objective signs are also being questioned as at a TOF ratio of more than 0.9, there may still be clinically significant residual paralysis with diplopia, blurry vision, facial weakness, facial numbness, generalized weakness, difficulty in swallowing, and reduced visual acuity. In addition, the reliability of qualitative TOF may be questionable in comparison to acceleromyography with residual paralysis (TOF <0.9) noted in acceleromyography group (14.5%) versus qualitative TOF group (50.0%) (P <0.0001) in a cohort of 155 patients after GA with rocuronium as the relaxant.
In our study, 5-s sustained head lift failed to show significant correlation with TOF and DBS whereas tongue depressor test, absent diplopia and ability to cough were good indicators of recovery as they correlated with TOF ratio of approximately 0.80–0.90 and DBS ratio of 0.89–0.96. Our results echo the findings of Kopman et al. who noted diplopia, visual disturbances, reduced grip strength, inability to oppose dentition, facial weakness, difficulty to drink or speak at TOF ratio of 0.70–0.75 in healthy volunteers after mivacurium infusion. Further the authors also noted persistent diplopia at TOF ratios between 0.85 and 1.0. Heier et al. also observed that 12 awake volunteers were able to protrude the tongue, swallow, sustain a 5-s head lift, speak and open eyes at a TOF ratio of 0.65–0.75.
In another clinical study, 71% patients with TOF < 0.7 could perform sustained (5-s) head lift at PACU admission. It is noteworthy that sustained head lift has a sensitivity of merely 10% to indicate residual paralysis, though specificity is high.
Similar to our results, the reliability of grip strength as a surrogate of objective NM monitoring was evaluated in a recent study and significant correlation was obtained between electronic dynamometer recorded grip strength and TOF ratio (correlation coefficient 0.886).
Similar to our observation, a tongue depressor test was found highly specific but poorly sensitive to predict PORP (defined TOF < 0.9).
Murphy et al. evaluated 149 patients in the PACU at admission and up to 1 h, based on the presence of 16 symptoms (general weakness, 5-s head lift; 5-s hand grip; 5-s eye opening; 5-s tongue protrusion; ability to hold tongue depressor; blurry vision; double vision; ability to track objects; facial numbness; ability to smile; ability to swallow; ability to smile; ability to speak; ability to cough; and ability to breathe deeply) and eleven objective signs (5-s head lift; 5-s hand grip; 5-s eye opening; 5-s tongue protrusion; tongue depressor test; ability to smile; swallow; speak; cough; object tracking and ability to breathe deeply) at TOF < 0.9 and TOF >0.9. An increased incidence and severity of symptoms were noted at all-time points in the patients with TOF < 0.9 (P <0.001). The median TOF was 0.75 (0.33–0.87) in the TOF <0.9 group and 1.01 (0.90–1.28) in the TOF >0.9 group, respectively. All patients in the TOF <0.9 group showed symptoms of muscle weakness at PACU admission and the weakness persisted after 1 h in 83% of the patients in the TOF < 0.9 group. The authors further observed ability to track objects and ability to cough were the most sensitive predictors of PORP. The findings are in congruence to our study emphasizing that ocular muscles are particularly sensitive to NMBAs and diaphragm, abdominal and laryngeal muscles may have significant residual effect of relaxant.
Unterbuchner et al. endeavored to develop an algorithm based on eight clinical tests to predict residual neuromuscular paralysis. Similar to our findings, no single test was found to be a reliable predictor of PORP. Employing regression analysis, they observed four parameters combined (open eyes ≥5 s, arm lift ≥5 s, head lift ≥5 s and swallowing without hindrance showed a sensitivity and specificity of 92.5% and 42.9%, respectively, at TOF <0.9; and sensitivity and specificity of 100% and 34.5%, respectively, at TOF < 0.7. The authors concluded that PORP can be detected by uncalibrated acceleromyography and if not available by a pathway of four clinical muscle function tests in awake patients.
We also found a close relationship between DBS and TOF stimulation over a wide degree of clinical blockade also seen in other studies.,
There were certain limitations in the study. First, clinical impact of the residual paralysis in terms of adverse respiratory events was not studied. However, we endeavored to carry out an observational study with the aim of recognizing the problem objectively and sensitizing the clinicians of the need for objective measures of NM monitoring. Second, confounding factors were not delineated as muscle weakness can be multifactorial (inhalational anesthetics and opioids). Third, different muscle relaxants were employed and results could be different for each relaxant.
| Conclusion|| |
Awareness of unrecognized PORP is the need of the hour. No single clinical sign of muscle strength reliably rules out residual paralysis, though absent diplopia and ability to cough effectively may closely approach a TOF of more than 0.9 and DBS of 1.0. The clinical practice of denial of objective measures of NM monitoring needs to be changed and perioperative NM monitoring be imbibed into practice to improve patient safety.
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Conflicts of interest
There are no conflict of interest.
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[Table 1], [Table 2], [Table 3]