Main instruments: Drager Fabius anesthesia machine, interlive vue MX600 monitor,
Train-Of-Four-Watch muscle relaxation monitor, Philips IU22 Color Doppler Ultrasound
Diagnostic Instrument.
Diaphragm ultrasound scan: Prior to anesthesia induction, patients will lie on the bed in a
semi-recumbent (45°) position. One operator skilled in ultrasonography will identify and
locate diaphragm using the hyperechoic pleural and peritoneal layers with an Philips IU22
Color Doppler Ultrasound Diagnostic Instrument.
Anesthesia method: After the patient entered the operating room, venous access will be opened
in the forearm, and routine monitoring of non-invasive BP, ECG, oxygen saturation(SpO₂) and
bispectral index(BIS) will be performed. During anesthesia induction, propofol 2.5mg/kg and
sufentanil 5μg/kg will be injected intravenously. When the BIS value drops below 60, the
muscle relaxation monitor will be calibrated. After T1 and TOF are stable, rocuronium will be
injected intravenously at 0.6 mg/kg. By the time T1=0, endotracheal intubation will be given,
and the respiratory parameters will need to be adjusted to volume control ventilation (VT
8-10 ml/kg, respiratory rate(RR) 12-18 times/min, and PETCO2 35-45 mmHg). During the
maintenance stage of anesthesia, the pneumoperitoneum pressure will be at a low level of
8-10mmHg, propofol target-controlled infusion(TCI) will be applied to maintain the plasma
concentration of 2.5-5.5 μg/mL, remifentanil TCI will be used to keep the plasma
concentration of 0.5-5 ng/mL, and rocuronium will be continuously pumped intravenously with
0.3-0.6 mg/kg/h for deep muscle relaxations, with the the post-tetanic twitch count (PTC)
value of 1 to 2.
Muscle relaxation monitoring: TOF-Watch SX muscle relaxation monitor is going to be adopted
in our study. The investigators will standardize the electrode position of the muscle
relaxation monitor. The distal electrode will be placed at the intersection of the radial
edge of the ulnar flexor carpi and the proximal edge of the wrist curve, while the proximal
electrode will be placed 3-6 cm away from the distal electrode. Two electrodes will put on
either side of the predicted location of the ulnar nerve, which will be able to minimize the
impact caused by misjudgment of the location of the nerve.
Measurement of diaphragmatic thickness: When B-mode ultrasound will be used to measure the
thickness of the diaphragm, a 5-12MHz linear array ultrasound probe will be put in the left
midaxillary line between the 8-10 costale, where is called the diaphragmatic zone of
apposition (ZAP). In the breathing exercise, the diaphragm is relatively fixed at ZAP, and
the breathing action has little influence on the movement of the diaphragm at ZAP, the
diaphragm only shows systolic and diastolic changes. Therefore, the measurement of the
diaphragm thickness at ZAP can truly reflect the overall thickness change of the diaphragm
during the respiratory cycle. Each value will be measured three times in three consecutive
breathing cycles, and the average of the nine measurements will be taken. The values of
diaphragmatic thickness at the end of inspirations (DTEI) and diaphragmatic thickness at the
end of expirations (DTEE) will be recorded respectively, then the change rate of
diaphragmatic thickness fraction (DTF) = (DTEI - DTEE) / DTEE × 100% will be calculated. In
addition, the recover rate of DTF = (pre-anesthetic DTEI - postoperative DTEI) /
pre-anesthetic DTEI × 100% also will be figured out. Ultrasound measurements should be
performed by two physicians with ultrasound experience. Results will be kept confidential to
the investigator, who will analyze the ultrasound data when the research is over.
The infusion of anesthetic drugs should be stopped at the end of surgery, and the patients
will be transferred into the Post-Anesthesia Care Unit (PACU) with endotracheal catheters and
continued monitoring. When the TOF value was ≥2%, patients in each group will be given SUG
(2mg/kg), respectively. The researchers will record the recovery conditions of diaphragmatic
function monitored by bedside ultrasound at the immediate time,10min, 30min and 2h after
extubation.