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  • Title: Postoperative upper airway obstruction after recovery of the train of four ratio of the adductor pollicis muscle from neuromuscular blockade.
    Author: Eikermann M, Blobner M, Groeben H, Rex C, Grote T, Neuhäuser M, Beiderlinden M, Peters J.
    Journal: Anesth Analg; 2006 Mar; 102(3):937-42. PubMed ID: 16492855.
    Abstract:
    Anesthetics, and even minimal residual neuromuscular blockade, may lead to upper airway obstruction (UAO). In this study we assessed by spirometry in patients with a train-of-four (TOF) ratio >0.9 the incidence of UAO (i.e., the ratio of maximal expiratory flow and maximal inspiratory flow at 50% of vital capacity [MEF50/MIF50] >1) and determined if UAO is induced by neuromuscular blockade (defined by a forced vital capacity [FVC] fade, i.e., a decrease in values of FVC from the first to the second consecutive spirometric maneuver of > or =10%). Patients received propofol and opioids for anesthesia. Spirometry was performed by a series of 3 repetitive spirometric maneuvers: the first before induction (under midazolam premedication), the second after tracheal extubation (TOF ratio: 0.9 or more), and the third 30 min later. Immediately after tracheal extubation and 30 min later, 48 and 6 of 130 patients, respectively, were not able to perform spirometry appropriately because of sedation. The incidence of UAO increased significantly (P < 0.01) from 82 of 130 patients (63%) at preinduction baseline to 70 of 82 patients (85%) after extubation, and subsequently decreased within 30 min to values observed at baseline (80 of 124 patients, 65%). The mean maximal expiratory flow and maximal inspiratory flow at 50% of vital capacity ratio after tracheal extubation was significantly increased from baseline (by 20%; 1.39 +/- 1.01 versus 1.73 +/- 1.02; P < 0.01), and subsequently decreased significantly to values observed at baseline (1.49 +/- 0.93). A statistically significant FVC fade was not present, and a FVC fade of > or =10% was observed in only 2 patients after extubation. Thus, recovery of the TOF ratio to 0.9 predicts with high probability an absence of neuromuscular blocking drug-induced UAO, but outliers, i.e., persistent effects of neuromuscular blockade on upper airway integrity despite recovery of the TOF ratio, may still occur.
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