Perioperative diaphragm ultrasonography for detecting residual curarization after surgery

Perioperative diaphragm ultrasonography as a novel means of detecting residual curarization after surgery

With an incidence ranging from 7 to 88 percent, post-operative residual curarization (PORC) continues to be a significant clinical problem. Residual blockage increases the risk of respiratory problems, such as airway obstruction, hypoxia, and reintubation, and prolongs the time of stay in the post-anaesthesia care unit (PACU). Neuromuscular monitoring of the train-of-four ratio (TOFr) at the adductor pollicis is regarded the gold standard for determining satisfactory recovery following neuromuscular blockade, with a TOFr of more than 0.9 indicating sufficient recovery. However, owing to the complexity of the technique, the demand for specialised equipment, the ease with which the test may be interfered with, and the discomfort of the test, the use of a neuromuscular monitor remains clinically limited.

The diaphragm is a significant respiratory muscle, performing 60–70% of the respiratory effort. Its malfunction manifests as postoperative respiratory failure, particularly when prolonged mechanical ventilation is used. Ultrasound is a non-invasive and visible approach for measuring diaphragm morphology in healthy volunteers and intensive care unit (ICU) patients that is repeatable, practical, and valid. In spontaneous breathing, diaphragmatic ultrasound (DUS) metrics such as diaphragmatic excursion (DE) and diaphragm thickening fraction (DTF) correlate with inspiratory nasal pressure and transdiaphragmatic pressure. As such, DUS may be used to forecast diaphragm muscle strength in lieu of direct assessment, which would be invasive and likely to result in serious problems. Recently, a study was published to evaluate the diagnostic accuracy of ultrasound parameters in detecting residual neuromuscular blockade in patients receiving general anaesthesia with nondepolarizing neuromuscular blockade for non-thoracic and non-abdominal surgery, using TOFr as the reference standard.

Between July and October 2019, patients having non-thoracic and non-abdominal surgery under general anaesthetic were enrolled at Peking Union Medical College Hospital. The gold standard for PORC was a train-of-four ratio (TOFr) less than 0.9. The diaphragmatic excursion (DE) and diaphragm thickening fraction (DTF) were measured using ultrasonography during quiet breathing (QB) and deep breathing (DB) (DB). The diaphragm excursion fraction (DEF) was determined by dividing the DE-QB value by the DE-DB value. The differential in diaphragm excursion (DED) was defined as DE-DB minus DE-QB. The cut-off values for ultrasonic parameters employed in the prediction of PORC were determined using receiver operating characteristic curve analysis.

75 patients were enrolled in total, with a PORC prevalence of 54.6 percent. The DE-DB and DED were connected favourably with the TOFr, but the DEF was correlated negatively with the TOFr. The DE-DB cut-off value for predicting PORC was 3.88 cm, with an 85.4 percent sensitivity (95 percent confidence interval [CI]: 70.1–93.9 percent), a 64.7 percent specificity (95 percent CI: 46.4–79.7 percent), a positive likelihood ratio of 2.42 (95 percent CI: 1.5–3.9), and a negative likelihood ratio of 0.23 (95 percent CI: 0.1–0.5. The DED cut-off value was 1.5 cm, with a specificity of 94.2 percent (95 percent confidence interval [CI]: 80.3–99.3 percent), a sensitivity of 63.4 percent (95 percent CI: 46.9–77.9 percent), a positive likelihood ratio of 10.78 percent (95 percent CI: 2.8–42.2 percent), and a negative likelihood ratio of 0.39 percent (95 percent CI: 0.3–0.6 percent).

This is the first diagnostic test that focuses only on the use of DUS characteristics for PORC detection. Our results indicate that DE-DB and DTF-DB have a substantial correlation with TOFr. The DTF DB, DE-DB, DEF, and DED were significantly lower in patients with persistent curarization. The DED, in instance, exhibited a poor sensitivity but a good specificity for detecting PORC. This work may give an alternate way for detecting PORC by using the current ultrasound instruments. Perioperative DUS may contribute to the identification of PORC, since DED has a high specificity.

Reference –

Lang, J., Liu, Y., Zhang, Y. et al. Peri-operative diaphragm ultrasound as a new method of recognizing post-operative residual curarization. BMC Anesthesiology 21, 287 (2021). https://doi.org/10.1186/s12871-021-01506-3