Functional Respiratory Imaging After Neostigmine or Sugammadex

Overview

The use of neuromuscular blocking agents (NMBAs) is still associated with postoperative pulmonary complications. The investigators rely on acceleromyography (AMG) of a peripheral nerve/muscle to assess the patients' breathing capability at the end of surgery. It is possible that respiratory complications after surgery (e.g. desaturation and atelectasis) are related to the lack of diaphragm activity. A previous trial by our study group links the use of sugammadex, a novel selective relaxant binding agent (SRBA) for reversal of neuromuscular blockade, to an increase in diaphragm electrical activity, compared to reversal with neostigmine. Our hypothesis is that by making nicotinergic acetylcholine receptors free from rocuronium in the diaphragmatic neuromuscular junctions, instead of increasing the amount of acetylcholine (like neostigmine does), sugammadex will result in a better neuromuscular coupling. This may have its subsequent effects on the central control of breathing, influencing the balance between intercostal and diaphragm activity. The investigators now propose a study in rats, where the investigators will use Functional Respiratory Imaging (FRI, property of FluidDA n.v., Groeningenlei 132, B-2550 Kontich) to assess regional lung ventilation after sugammadex, neostigmine or spontaneous reversal. The images obtained through micro-CT scans allow us to accurately reconstruct airway morphology in the free-breathing rat. It will provide us with new insights into breathing physiology after reversal of neuromuscular blockade.

This study is designed to assess the effect of sugammadex, neostigmine/glycopyrrolate and spontaneous reversal of a moderate rocuronium-induced neuromuscular blockade on regional lung ventilation. This is a randomized, controlled, parallel-group double blind trial in rats. A total of 18 adult male Sprague-Dawley rats will be used, 6 in each treatment group. The animals will be randomized in one of three groups, in a 1:1:1 ratio. This randomization will be performed according to a computer-generated randomization list. The first group will receive neostigmine/glycopyrrolate. The second group will receive sugammadex. The third group will receive water for injection. Reversal agents will be administered at a train-of-four (TOF) of 0.5, as measured with AMG. The investigators will assess regional ventilation by means of micro-CT scanning during spontaneous breathing after the TOF ratio has reached ≥ 0.9. This way, the investigators can accurately reconstruct airway morphology. The different airway sections can then be linked to the corresponding lung tissue, and a full anatomical picture is thus rendered. A comparison of morphological scans at different breathing levels (e.g. end-inspiratory and end-expiratory) will allow us to model breath-by-breath regional airway and alveolar recruitment.