Study Design and Setting
This retrospective cohort study was approved by the Ethics committee of Luoyang Central Hospital, Zhengzhou University, Henan, China. Because of its retrospective study nature, the need for informed consent was waived. All methods were performed following the relevant guidelines and regulations. The manuscript was prepared according to the statement on the Strengthening the Reporting of Observational Studies in Epidemiology (STROBE).
The inclusion criteria were patients aged 18 and above who received either DEX or propofol infusion during CABG surgery as an adjunct for general anaesthesia and as a postoperative sedative drug until extubation in the ICU. Exclusion criteria were patients receiving DEX and propofol together at any time during the intraoperative and postoperative periods except for an induction dose of propofol at the start of general anaesthesia and patients who had severe comorbidities, including valvular heart disease, infections, and lung, kidney and liver dysfunction.
After the patients had received premedication of 10 mg morphine and 0.3 mg scopolamine by intramuscular injection, they were anesthetised with etomidate (0.3 mg/kg), sufentanil (0.8 μg/kg) and atracurium (0.2 mg/kg), their tracheas were intubated, and their lungs were mechanically ventilated (I/E = 1:1.5; VT = 6-8 ml/kg; 10–12/min). Anesthesia was maintained with infusions of propofol or DEX initially at 2–12 mg/kg/hr. or 1.0 μg/kg/hr., respectively, and reduced thereafter to DEX 0.3 μg/kg/hr. All patients received 1–2% sevoflurane, sufentanil (0.6–0.8 μg/kg) and atracurium (0.1 mg/kg) when required during surgery. Patients received routine monitoring, including invasive arterial pressure, Bispectral Index (BIS) (Covidien, USA) value, body temperature, pulse oximetry and ECG. Pulmonary artery pressure, cardiac index and cardiac output were continuously monitored via a Swan-Ganz catheter (Vigileo II, Edwards, Irvine, USA).
The patients underwent median sternotomy; the left internal mammary artery and part of the saphenous vein were harvested at normal body temperature. Heparin was administered intravenously to adjust the activated clotting time readings within the appropriate range. CABG was performed on a beating heart with off-pump surgery as a routine procedure. However, if the mean pulmonary artery pressure was higher than 50% of the mean arterial pressure and the patient was haemodynamically unstable when surgeons attempted to elevate the heart for surgery, a heart beating on-pump surgery was performed using partial assistance from the cardiopulmonary bypass (CPB). The patient was connected to the CPB circuit to maintain circulation, and the coronary artery bypass grafting was completed under CPB assistance without cardiac arrest. Methoxamine was used to increase peripheral vascular resistance when raising the patient's heart during off-pump CABG, with volume control to maintain circulatory stability and reduce myocardial oxygen consumption. Because it is necessary to control the patient's heart rate during off-pump CABG, only methoxamine was used without other positive inotropic drugs, for example, norepinephrine, which could excite the β receptor.
The primary outcome measured was pulmonary complication following CABG between patients who received DEX or propofol. This was defined as any pre-defined pulmonary complications following surgery, including respiratory infection, respiratory failure, pleural effusion, atelectasis, pneumothorax, bronchospasm, aspiration pneumonitis, pulmonary oedema, pulmonary embolism, and acute respiratory distress syndrome.
The secondary outcomes include the duration of mechanical lung ventilation, postoperative morbidity, 30-day mortality and length of stay (LOS) in ICU and hospital. We also looked at exploratory outcomes of intraoperative findings such as surgical times and estimated blood loss.
Demographic data such as age, gender, body mass index, comorbidities including cardiac arrhythmia type and alcohol consumption (alcoholism: defined as drinking wine during two meals/day), American Society of Anaesthesiology (ASA) physical status classification and laboratory data of kidney function, blood count and C-reactive protein (CRP) were collected. Intraoperative data included inotropic drugs used, anaesthetic agents, duration of anaesthesia, duration of surgery, intraoperative fluid, urine output, autologous blood transfusion, extracorporeal circulation and intra-aortic balloon pump assistance.
Postoperative data including new-onset cardiac arrhythmia and complications after surgery were also collected as outcome measures. Postoperative pulmonary complications were defined as postoperative pneumonia, hypoxemia (PaO2/FiO2 ≤ 300 mmHg), postoperative respiratory failure (PaO2/FiO2 ≤ 200 mmHg and required mechanical ventilation for more than 48 h) and atelectasis and bronchospasm exacerbation of pre-existing chronic lung disease. Surgical bleeding was defined as chest tube drainage exceeding 500 ml per hour or 200 ml per hour for three consecutive hours accompanied by blood volume replacement and hemodynamic instability.
All continuous variables, if normally distributed, were presented as mean ± SD; otherwise, the non-normally distributed data and categorical data were presented as median (25-75 IQR) or number (percentage). First, we compared the clinical characteristics, including demographic data, laboratory data, post-operative data and data during surgery. The Mann-Whitney U test was used to analyze continuous variables. The Chi-square test was used to compare categorical variables to evaluate the difference between the DEX and the propofol group. Based on the statistical comparisons between the two groups, the significant preoperative factors and important perioperative factors related to the postoperative pulmonary complications such as time of surgery, length of stay in the hospital, duration of mechanical ventilation, length of stay in ICU after surgery, DEX use, CPB assistance, diabetes, wound infection, age and BMI were integrated into a multivariate logistic regression model, and the adjusted ORs, 95% CIs, and P values were calculated for each variable. All data were analysed with SPSS 22 (ABS, USA). A P value less than 0.05 was considered to be of statistical significance.
BMC Anesthesiol. 2022;22(51) © 2022 BioMed Central, Ltd.