Peri-operative diaphragm ultrasound as a new method of recognizing post-operative residual curarization

Background This study sought to evaluate the diagnostic accuracy of peri-operative diaphragm ultrasound in assessing post-operative residual curarization (PORC). Methods Patients undergoing non-thoracic and non-abdominal surgery under general anaesthesia were enrolled from July 2019 to October 2019 at Peking Union Medical College Hospital. A train-of-four ratio (TOFr) lower than 0.9 was considered as the gold standard for PORC. Diaphragm ultrasound parameters included diaphragmatic excursion (DE) and diaphragm thickening fraction (DTF) during quiet breathing (QB) and deep breathing (DB). The diaphragm excursion fraction (DEF) was calculated as the DE-QB divided by the DE-DB. The diaphragm excursion difference (DED) was defined as DE-DB minus DE-QB. Receiver operating characteristic curve analysis was used to determine the cut-off values of ultrasound parameters for the prediction of PORC. Results In total, 75 patients were included, with a PORC incidence of 54.6%. The DE-DB and DED were positively correlated with the TOFr, while the DEF was negatively correlated with the TOFr. The DE-DB cut-off value for predicting PORC was 3.88 cm, with a sensitivity of 85.4% (95% confidence interval [CI]: 70.1-93.9%), specificity of 64.7% (95% CI: 46.4-79.7%), positive likelihood ratio of 2.42 (95% CI 1.5-3.9), and negative likelihood ratio of 0.23 (95% CI: 0.1-0.5). The DED cut-off value was 1.5 cm, with a specificity of 94.2% (95% CI: 80.3-99.3%), sensitivity of 63.4% (95% CI: 46.9-77.9%), positive likelihood ratio of 10.78 (95% CI: 2.8-42.2), and negative likelihood ratio of 0.39 (95% CI: 0.3-0.6). Conclusions Peri-operative diaphragm ultrasound may be an additional method aiding the recognition of PORC, with DED having high specificity.