Monitoring intraoperative neuromuscular blockade and blood pressure with one device (TOF-Cuff): A comparative study with mechanomyography and invasive blood pressure.

OBJECTIVE: The overall objective of the study is to determine the ability of TOF-Cuff device (blood-pressure modified cuff, including stimulation electrodes) to monitor with the same device the non-invasive blood pressure (NIBP) and the depth of a neuromuscular blockade (NMB) induced pharmacologically, by stimulation of the brachial plexus at the humeral level and recording evoked changes in arterial pressure.

MATERIAL AND METHOD: Clinical, single-centre, open-controlled study with 32 adult patients ASA I-III for scheduled elective surgery under general anaesthesia in supine position, for the validation of neuromuscular monitoring, comparing the values obtained from neuromuscular relaxation TOF-Cuff with those obtained by mechanomyography (MMG) (control method) during the recovery phase of NMB, when a TOF ratio>0.7 and>0.9 (primary endpoint) were reached respectively. And an additional consecutive study of 17 patients for validation of NIBP monitoring with TOF-Cuff device vs invasive blood pressure measured by an intra-arterial catheter. All data were analyzed using the Bland-Altman method.

RESULTS: Recovery from NMB measured with the TOF-Cuff was earlier compared to MMG. Comparing TOF-ratio>0.9 measured with TOF-Cuff vs TOF-ratio>0.7 with MMG, a specificity of 91% and a positive predictive value of 84% were obtained. In NIBP measurement, the mean error and standard deviation of both systolic blood pressure (1.6±7mmHg) and diastolic blood pressure (-3.4±6.3) were within the European accuracy requirements for medical devices.

CONCLUSIONS: The TOF-Cuff device has been shown to be valid and safe in the monitoring of NMB and in the measurement of NIBP, with no patient presenting any adverse events, skin-level lesions or residual pain. It is not interchangeable with MMG, having a TOF-ratio>0.9 quantified by the TOF-Cuff device, a good correlation with a TOF-ratio>0.7 on MMG.