- Ethics approval and consent to participate:
This study was conducted from October 2019 to December 2021 after the approval of the Department of Anesthesiology and the local research and ethical committee (on October 9, 2018). It was registered at ClinicalTrials.gov on April 3, 2019 (ClinicalTrials.gov ID: NCT03903367).
- Written informed consent was obtained from all participants and is available upon request.
- Funding: No external source of funding.
For 44 patients aged 18 to 65 who underwent elective open-heart surgery via median sternotomy, we obtained written informed consent. The patients were excluded if they had chest trauma, unstable hemodynamics, contraindications to local anesthetic drugs or to perform TPVB, patients with impaired left ventricular function, coagulation abnormalities, opioid abuse, history of chronic pain, psychic problems, and BMI ≥ 30.
The patients were prepared preoperatively by history taking, physical examination, and routine investigations such as CBC, coagulation profile, renal profile, liver profile, ABG, CXR, Echocardiography, and Coronary angiography.
On arrival at the operating theatre, an intravenous cannula (18G) was inserted, and IV 250 to 500 ml crystalloid fluids were infused, arterial line and central venous line were inserted under sedation (3-5 mg midazolam), and a complete aseptic condition, the monitor was attached to the patients to take preoperative readings of heart rate, O2 saturation, blood pressure, end-tidal CO2, and electrocardiogram. The urinary catheter was inserted following the induction of anesthesia. Following laryngoscopy and endotracheal intubation, the patient was administered midazolam 0.1 mg/kg, fentanyl 3-5 µg/kg, propofol up to 1-2 mg, and atracurim 0.5 mg/kg. Anesthesia was induced 3-5 minutes after preoxygenation with 100% O2. Anaesthesia was sustained at a 100% oxygen level; isoflurane was titrated according to the desired depth of anesthesia and atracurium infusion 5-10 mic/kg/min.
- A computer-generated permuted block randomization sequence was employed to randomize the patients into two groups.
Group Ⅰ (Fentanyl group) (n = 22): GA was administered, and fentanyl infusions were initiated at a rate of 2µg/kg/h following intubation and were discontinued at the conclusion of the surgery. Group Ⅱ (paravertebral group) (n=22): In the preoperative phase, ultrasound-guided bilateral thoracic paravertebral catheters were inserted at the level of T4. A 0.3ml/kg 0.25% bupivacaine bolus dose was administered in each catheter, with a total of 20 ml administered on each side. General anesthesia was administered for 15-20 minutes prior to the commencement of a continuous infusion of 0.1 ml/kg/h 0.25% bupivacaine, which was terminated once the procedure was complete. After 24 hours, the catheters were eliminated. When there was an increase ≥20% in the mean blood pressure (MBP) or heart rate (HR) from the baseline was observed, an incremental dose of fentanyl (2 µg/kg) was administered.
The patients were transferred to the ICU after the completion of the surgery, where they were reconnected to the mechanical ventilator. The Critical-Care Pain Observation Tool (CPOT) was used to evaluate postoperative pain. The patient was considered pain free if CPOT≤ 2, if CPOT≥3 the patient received intravenous morphine 2-3 mg.
Ultrasound-guided TPVB Procedure: The back of the patient was exposed, and skin white was applied by lidocaine 1% at the site of injection using an ultrasound Philips HD5 machine and linear ultrasound probe (4-16 MHz) in complete aseptic conditions. In the transverse approach, the transverse process was visualized by moving the probe medially after aligning it over the long axis of the rib. This was accomplished by tilting the probe to identify the internal intercostal membrane, parietal pleura, and external intercostal muscle.
From the lateral to medial direction, In-plane introduction of the needle was performed at the probe's lateral end. The needle tip was positioned near the costotransverse ligament in the paravertebral space. The local anesthetic spread should cause displacement of the pleura anteriorly. The catheters were inserted after the bolus dose of local anaesthetic was injected to create a space for the catheter, via an 18G Tuohy needle, 3-4 cm distal to needle tip then the catheters were tunneled and fixed in place by adhesive tape.
age, sex, weight, height, type of operation, left ventricular ejection fraction, Euro score II, and operative data were all recorded. time required for aortic cross-clamp, total bypass time, total operative time, and the necessity of inotropic support. Before the induction of anesthesia, the mean arterial blood pressure and heart rate were measured and recorded. Subsequently, they were measured and recorded 1 minute prior to the skin incision, 3 minutes after the skin incision, 1 minute prior to the sternotomy, and 3 minutes after the sternotomy. At 8, 12, and 24 hours after admission to the ICU, the Critical-Care Pain Observation Tool (CPOT) was the initial outcome. The second outcome was the time required for tracheal extubation, the total 24-hour morphine requirement, and the intraoperative fentanyl requirements, Chest tube drainage volume, duration of ICU stay, and complications associated with paravertebral block, such as pneumothorax and blood vessel or dural puncture.
The Statistical Analysis:
In order to determine the sample size, the comparison of CCPOT at 24h postoperative between patients who underwent sternotomy treated with bilateral continuous paravertebral block and those treated with IV fentanyl infusion, due to the fact that it was the primary result of our studies. As reported in a previous publication (9), In the paravertebral block-treated group, the median and interquartile range of the 24-hour postoperative visual analogue scale (VAS) were approximately 6 (1–11), whereas in the fentanyl group, it was approximately 7 (1–23, respectively). The median was considered in replacement of the mean and estimated the SD from the range. Accordingly, for each group, it was determined that a minimum of 22 patients was the appropriate sample size. The data were statistically described in terms of mean and standard deviation (₱SD), median and range, or frequencies and percentages. The normal distribution of numerical data was evaluated using the Kolmogorov-Smirnov test. The numerical variables were compared using the student t-test. A statistically significant P-value was defined as one that was less than 0.05. IBM SPSS (Statistical Package for the Social Science; IBM Corp, Armonk, NY, USA) release 22 for Microsoft Windows was employed to conduct all statistical analyses.
