This randomized prospective study was done in Mansoura Oncology Center, after approval of the institutional review board (MD/15.05.91), and clinical trials registration number is NCT03319511.
Seventy-two female patients, undergoing unilateral modified radical mastectomy with axillary dissection and physical status American Society of Anesthesiologists (ASA) II-IV aged 35 to 70 years, were included. Patients with cardiovascular, pulmonary, renal, hepatic, and endocrinal diseases were accepted. Patients were excluded upon refusal for regional techniques or the presence of coagulopathy, local infection, and hypersensitivity to anesthetic drugs.
Complete medical history, clinical examination, and routine laboratory investigations were assessed (ECG, complete blood picture, coagulation profile, liver and renal function tests). Further investigations were done according to morbidity (as echocardiography, pulmonary function test). All patients were informed about the regional anesthesia techniques, and consent was written.
In the preparation area, an intravenous peripheral line was inserted opposite to surgical side. Preload with 10 ml/kg Ringer’s lactate was given except in patients with renal impairment, pulmonary congestion, or impaired systolic function. In the operating room, monitoring included electrocardiography (ECG), heart rate (HR), noninvasive mean blood pressure (MBP), and oxygen saturation (SpO2).
Patients were randomly assigned through the closed envelop method into two equal groups, the thoracic paravertebral block (TPVB) group and the segmental thoracic spinal anesthesia (STSA) group (each n = 35).
Regional procedures were done under complete aseptic precautions, and the skin infiltration was performed with 2 ml lignocaine 1% before needle puncture.
Thoracic paravertebral block
Patients were in a setting position. Linear ultrasound (Siemens Acuason 300, Germany) probe of high-frequency linear transducer (7–12 MHz) was used to confirm the thoracic levels T2 and T4 that were marked at their superior aspect. The US probe was placed transversely, perpendicular to the longitudinal plane of the spinous processes. Medially, the transverse process was visualized, while the pleura appear under the inferolateral aspect. A 22 G spinal needle was introduced in-plane in a medial direction (Krediet et al. 2015), aiming to penetrate the internal intercostal membrane; after negative aspiration, 0.3 ml (1.5 mg)/kg of 0.5% plain bupivacaine in addition to 0.5 microgram (mcg)/kg dexmedetomidine (DEX) was slowly injected over 2–3 min. The dose was divided between two punctures at levels T2 and T4. Spread of local anesthetic leads to depression of the pleura.
Segmental thoracic spinal anesthesia
The patient was in the sitting position with a flexed head. Determine the space and depth using ultrasound. In the parasagittal plane, 2 cm from the midline, the desired level (T5–6) was determined by an ultrasound (2–5 MHz) curved array probe through counting up from the last rib. A skin mark was placed to identify the correct level of the block. The probe is moved medially along the 5th rib echo to identify the ligamentum flavum and posterior dura hyperechoic lines (Salman et al. 2011).
A paramedian approach with a 25 G Quincke spinal needle was used. After piercing the ligamentum flavum, the needle’s stylet was removed, and the hub was observed for free flow clear cerebrospinal fluid (CSF); 1.5 ml of plain bupivacaine 0.5% in addition to 5 mcg DEX was injected. Then, the patient was placed in a lateral position on the surgical side for 15 min before shifting to a supine position.
The technique was abandoned upon patient request, if ultrasonic scanning of dura is not clear, more than 4 attempts, or repeated paresthesia. If paresthesia occurred, withdraw the needle 0.5–1 mm; the injection must be painless.
The onset of sensory block was evaluated by pinprick test with a 25-gauge needle along the anterior axillary line using a 3-point score: grade 0: Sharp pin felt; grade 1: analgesia, the dull sensation felt; and grade 2: anesthesia, no sensation felt. The block onset was tested every 5 min in TPVB group for 30 min, every 2 min in STSA group for 15 min after the completion of the injection, and then every 30 min following surgery until sensory regression.
Block success was defined as a complete sensory block in all T2–T6 dermatomes within 30 min of injection; analgesia and sedation — if required for painless surgery — were provided through increments of iv midazolam 1–2 mg for sedation, fentanyl 25 mcg for analgesia, and propofol 50 mg consecutively. General anesthesia (GA) was scheduled in case of block failure, compromised ventilation, difficulty to control pain, agitation, or upon patient request. Then, the case would be excluded from the study.
The motor block was evaluated before surgery; in the upper limbs, it was assessed by the epidural scoring scale for arm movements (ESSAM) score: handgrip (T1/C8), wrist flexion (C8/C7), and elbow flexion (C6/ C5); four grades (0–3) were based on the number of absent movements in the 3 joints ascendingly (Abd Elrazek et al. 1999). The motor block in the lower limbs was assessed by the modified Bromage scale (Cline et al. 2004). Motor regression in the limbs was assessed every 15 min until recovery.
Grading of sedation was evaluated by using the Ramsay sedation scale of 6 grades from 1: awake to 6: unarousable (Ramsay et al. 1974). The sedation score was recorded basal and then every 30 min during the procedure. Patients, postoperative assessors, and surgeons were blinded for procedure. The satisfaction was assessed after surgery for surgeons, while after 24 h for patients, using VAS (0–10), zero level was the least, and 10 was the highest satisfaction level.
Quality of analgesia was measured by visual analog score (VAS) on a 0–10 cm scale; 0 is no pain and 10 the maximum pain. VAS score was measured at 0, 2, 4, 6, 8, 12, 18, and 24 h postoperatively. Whenever VAS score is ≥ 4, analgesia was provided by oral paracetamol 1 g every 8 h, IV 30 mg of ketorolac every 8 h, and incremental doses of meperidine 20 mg as rescue analgesia if VAS is still ≥ 4. Total analgesic consumption in 24 h, number of patients requiring analgesia, and the time to first analgesic request were recorded. The incidence of complications was recorded including bradycardia, hypotension, nausea, vomiting, and hypoxia. Hypotension is considered on a 20% drop in baseline MBP or systolic pressure below 90 mmHg; it was treated with iv ephedrine 5 mg increments. Bradycardia is considered if HR ˂ 50 beat/min; it was treated with iv atropine 0.5 mg. Hypoxia is considered if oxygen saturation ˂ 90%; it was managed by oxygen mask, assisted breathing; if not sufficient for ventilation, a laryngeal mask or an endotracheal tube is inserted to proceed as GA.
A pilot study including 5 patients in each group was conducted to determine the study sample size with regard to efficacy. The difference in fentanyl requirements was a differentiating outcome. The mean and standard deviation (SD) for TPVB group were 12 ± 9, while it was 5 ± 8 for STSA. Accordingly, the calculated effect size was 0.822 using the priory G*Power two-tailed test. Assuming α error of 0.05, and a power of 90%, the sample size was 66. An additional 5% was considered for data drop, so the sample size was 70 divided into 35 for each group. The results of this pilot study are also implemented increasing the spinal dose from 1 to 1.5 ml of bupivacaine for better coverage of breast dermatomes. Also, adopting the lateral position for 15 min after spinal injection thus increases block selectivity and safety.
The collected data were coded, processed, and analyzed using SPSS (Statistical Package for Social Science, SPSS Inc., Chicago, IL, USA) program version 21 for windows. Shapiro-Wilk test was used to check the normality of data distribution. Qualitative data were described using numbers and percent. Association between categorical variables was tested using the chi-square test or Fisher exact test. Continuous variables were presented as mean ± SD for parametric data and median (min-max) for nonparametric data. The two groups were compared with the Student t-test for parametric data, while the Mann-Whitney test was used to compare nonparametric data.