The Analgesic Effect of Bilateral Quadratus Lumborum Block and Its Postoperative Implication on Kidney Function in Colorectal Surgery: a Comparative Randomized Control Trial Study With Epidural Anesthesia.

• Study place: Ain Shams University Hospitals.
• Written informed consent will be taken from all patients.
• Patients with an American Society of Anesthesiologists (ASA) physical status I-III, aged between 35 and 65 years were included in this study and scheduled for short colorectal surgery (2-4 hours), such as segmental colectomies and polypectomy using either the sub umbilical incision or laparoscopic technique. Patients with major cardiac or cerebral vascular diseases, bleeding disorders (known contraindication for EP anesthesia and in QL which is considered a deep block), abnormal kidney functions (elevated creatinine, BUN level, or history of renal disease), and neurological disorders were excluded. Patients with known allergy to local anesthetics, puncture site infection, and body mass index (BMI) of >35 kg/m2 were also excluded. Also, patients with intra-operative complications such as hemodynamic instability and unexpected prolonged surgical duration were excluded. Patients who refused to consent to the study were not enrolled, without any discontinuation of their management.

The selected patients were randomized using an automated computer-assisted method (www.randomizer.org), which divided them into 2 groups: the control group (EP) received epidural anesthesia, whereas the study group (QL) received a QL block. The interventions were done by well-experienced anesthesiologists.

Renal Doppler. An experienced radiologist performed the renal Doppler with at least 5 years experience in the doppler field being blinded to the patients' data. A renal Doppler study was performed for both groups preoperatively and postoperatively. Patients were asked to lie supine or in lateral positions. The ultrasound (US) probe was applied to the anterior or midaxillary line with the probe in a transverse direction until the kidney was adequately visualized. The intrarenal and main renal arteries were assessed using color and pulse wave Doppler. The intrarenal arteries assessment was repeated at the upper, mid, and lower pole levels of each kidney. Also, the renal RI of the main renal artery was measured bilaterally. All measurements for each patient were collected and the average RI was calculated. The normal RI is considered when the value was <0.7. The renal Doppler was assessed within 24 hours pre-operative and within 2-3 hours after surgery completion.

Patient preparation. Patients who fasted for 8 hours, with full clinical and laboratory results, were examined for any exclusion criteria with specific concerns with regard to kidney function. 12 hours before the scheduled time for surgery, renal Doppler was performed to measure the renal RI of all patients, before starting to fast for surgery and after adequate hydration was checked, based on his ward fluid chart.

Inside the operating room. The standard monitoring, including electrocardiogram (ECG), oxygen saturation, non-invasive blood pressure, and capnogram for end-tidal carbon dioxide (ETCO2), were applied. Infusion of Ringer's lactate solution (8 mL/kg) was started through a wide bore cannula. IV midazolam 0.05 mg/kg was given as a premedication before the induction of anesthesia by 2 μg/kg fentanyl, 2 mg/kg propofol, and 0.5 mg/kg atracurium. An endotracheal tube was inserted to initiate mechanical ventilation while keeping the ETCO2 in the range of 35-45 mmHg. Anesthesia maintenance was performed with 1.5% isoflurane and oxygen and topped up with IV atracurium 0.5 mg/kg every 20 minutes. The urinary output was followed up using a urinary catheter. IV fentanyl dose of 1 μg/kg was administered, in response to an increase in blood pressure or heart rate of >20% of the baseline measurement. Continuous ECG, blood pressure, and pulse saturation were monitored. To ensure an adequate fluid balance, fluid input, fluid output (urine and third space loss), blood loss, and central venous pressure were recorded. The inhalational anesthetic isoflurane was discontinued at the end of the surgery, followed by the administration of IV neostigmine of 0.05 mg/kg and atropine of 0.02 mg/kg, to reverse the residual neuromuscular block. The trachea was extubated after spontaneous breathing returned.