Comparing Neuromuscular Blockade Measurement Between Upper Arm (TOF Cuff®) and Eyelid (TOF Scan®) Using Mivacurium during General Anesthesia

Abstract

BACKGROUND Mivacurium is a non-depolarizing neuromuscular blocking agent. TOF-Cuff® is a device that monitors intraoperative neuromuscular blockade and blood pressure. TOF-Scan® measures muscle relaxation status of an anaesthetized patient. This study included 36 patients aged 18 to 75 years presenting for elective surgery, to compare neuromuscular blockade measured using the TOF-Cuff of the upper arm and the TOF-Scan of the facial corrugator supercilii muscle during general anesthesia and following administration of mivacurium. MATERIAL AND METHODS Train-of-four (TOF) values were obtained every 30 s before intubation and successively every 5 min until extubation. RESULTS The median onset time for TOF-Cuff was longer than for TOF-Scan (210 s vs 90 s, P<0.00001). Multiplying the time to relaxation (according to TOF-Scan) by 1 to 8, respectively, provided concordance with the TOF-Cuff result for the following cumulative percentages of patients: 5.5%, 38.9%, 58.3%, 77.8%, 83.3%, 86.1%, 88.9%, and 91.7%. Analogue values for time to recovery from the last dose were 11.1%, 63.9%, 83.3%, 86.1%, 86.1%, 88.9%, 88.9%, and 91.7%. The proportion of patients who still had TOFratio=0 in the assessment performed at min 15 did not differ significantly between these 2 methods (P=0.088). Both TOF-Scan and TOF-Cuff showed a false-negative result in patients with clinical symptoms of preterm recovery; the numerical difference favored TOF-Cuff (1.6% vs 2.1%) but without statistical significance (P=0.2235). CONCLUSIONS When measurement on the limb is not possible, TOF-Scan on the eyelid can be an alternative for TOF-Cuff on the upper arm, if the time to relaxation is multiplied by at least 8, which is enough for 90% of patients.

Figure 1

Placement of devices (A) TOF-Scan and (B) TOF-Cuff.

Figure 2

(A) Kaplan-Meier curve presenting time to TOF_ratio=0 measured with both methods. (Created in: Statistica 13.3, Tibco). (B) The Bland-Altman plot (average vs difference) for onset of neuromuscular block after mivacurium 0.2 mg/kg. The solid line illustrates the mean difference and the dashed lines indicate average difference ±1.96 standard deviation of the difference. (Created in: Microsoft Excel 2019). TOF – train-of-four; TOF-Cuff – a device designed for neuromuscular monitoring on an upper arm; TOF-Scan – a device designed for neuromuscular monitoring on a facial corrugator supercilii muscle.

Figure 3

The Bland-Altman plot (average vs difference) for time from the last dose of mivacurium to TOF_ratio>90. The solid line illustrates the mean difference and the dashed lines indicate average difference ±1.96 standard deviation of the difference. TOF – train-of-four; TOF-Cuff – a device designed for neuromuscular monitoring on an upper arm; TOF-Scan – a device designed for neuromuscular monitoring on a facial corrugator supercilii muscle. (Created in: Microsoft Excel 2019).