Development of an algorithm using clinical tests to avoid post-operative residual neuromuscular block

Abstract

Background: Quantitative neuromuscular monitoring is the gold standard to detect postoperative residual curarization (PORC). Many anesthesiologists, however, use insensitive, qualitative neuromuscular monitoring or unreliable, clinical tests. Goal of this multicentre, prospective, double-blinded, assessor controlled study was to develop an algorithm of muscle function tests to identify PORC.

Methods: After extubation a blinded anesthetist performed eight clinical tests in 165 patients. Test results were correlated to calibrated electromyography train-of-four (TOF) ratio and to a postoperatively applied uncalibrated acceleromyography. A classification and regression tree (CART) was calculated developing the algorithm to identify PORC. This was validated against uncalibrated acceleromyography and tactile judgement of TOF fading in separate 100 patients.

Results: After eliminating three tests with poor correlation, a model with four tests (r = 0.844) and uncalibrated acceleromyography (r = 0.873) were correlated to electromyographical TOF-values without losing quality of prediction. CART analysis showed that three consecutively performed tests (arm lift, head lift and swallowing or eye opening) can predict electromyographical TOF. Prediction coefficients reveal an advantage of the uncalibrated acceleromyography in terms of specificity to identify the EMG measured train-of-four ratio < 0.7 (100% vs. 42.9%) and <0.9 (89.7% vs. 34.5%) compared to the algorithm. However, due to the high sensitivity of the algorithm (100% vs. 94.4%), the risk to overlook an awake patient with a train-of-four ratio < 0.7 was minimal. Tactile judgement of TOF fading showed poorest sensitivity and specifity at train of four ratio < 0.9 (33.7%, 0%) and <0.7 (18.8%, 16.7%).

Conclusions: Residual neuromuscular blockade can be detected by uncalibrated acceleromyography and if not available by a pathway of four clinical muscle function tests in awake patients. The algorithm has a discriminative power comparable to uncalibrated AMG within TOF-values >0.7 and <0.3.

Trial registration: Clinical Trials.gov (principal investigator's name: CU, and identifier: NCT03219138) on July 8, 2017.

Keywords: Postoperative residual curarization; acceleromyography; algorithm; clinical muscle function tests; electromyography.

Conflict of interest statement

Ethics approval and consent to participate

Study protocol was approved by the Institutional Ethical Committee (Ethikkommission der Fakultät für Medizin der Technischen Universität München, Munich, Germany; protocol N° 1783/07) in 2007. Study was performed from 2008 to 2009. Informed consent of the patients was obtained before data collection.

Consent for publication

Not applicable. This study did not contain any individual person’s data in any form (including individual details, images or videos).

Competing interests

Manfred Blobner and Friedrich Pühringer have received honoraria, travel fundings and the conduct of contracted research from GlaxoSmithKline and MSD, Haar, Germany. Matthias Janda has received payments, travel fundings for lectures from MSD, Haar, Germany. Berthold Bein has received honoraria for consulting and giving lectures from MSD, Haar, Germany. Heidrun Fink has received honoraria from MSD, Haar, Germany. All other authors declare that they have no competing interests.

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Figures

Fig. 1

CONSORT Flow Diagram

Fig. 2

Example of an instable EMG signal during return of consciousness. After moving the arm the cable was disconnected. The patient did not accept connecting the EMG again or the AMG on the contralateral arm

Fig. 3

Specification of eight clinical tests in relation to the Train-of-Four Ratio (TOFR) as measured by electromyography

Fig. 4

Regression analysis with classification and regression tree (CART). The upper section of the figure depicts how CART revealed six nodes of test scores that significantly divide the collective regarding the TOFR measured by calibrated electromyography (EMG). The lower section of the figure shows boxplots of EMG measured TOFR in patients allocated to the respective nodes. The test combinations of node 11 (arm lift ≥5 s, head lift ≥5 s, and swallowing without any hindrance) was able to discriminate between patients with TOFR

Fig. 5

Receiver operated characteristic (ROC) curves to discriminate electromyography (EMG) measured train-of-four ratio (TOFR) with uncalibrated AMG and algorithm of muscle function tests. The area under the curves (AUC) of uncalibrated acceleromyography (AMG) and the algorithm of muscle function tests did not differ significantly for TOFR p = 0.094) as well as TOFR <0.9 (p = 0.136)

Fig. 6

Risk to overlook patients with residual neuromuscular blockade with a TOFR