INTRODUCTION
Major gynecological cancer surgeries are associated with long postoperative recovery periods and complications owing to surgical trauma [1]. Therefore, Enhanced Recovery After Surgery (ERAS) principles should be used to reduce postoperative complications and accelerate recovery. Although epidural analgesia, according to ERAS, is still considered the gold standard in major abdominal surgeries, the tendency towards minimally invasive methods has increased considering the complications and side effects as well as the widespread use of ultrasonography (USG). Peripheral nerve blocks have become an integral part of multimodal analgesia [2-4]. A transversus abdominis plane block (TAPB) is frequently used for somatic anaesthesia of the anterior abdominal wall [5].
For somatic blockade of the anterior abdominal wall, blocking the thoracolumbar nerves, namely the lateral and anterior branches of the T6-L1 dermatomes, is required [6]. Midline surgery requires bilateral block. The TAPB can be applied laterally, posteriorly or subcostally depending on the site of application. Among these, the USG-guided PTAPB through the lateral abdominal wall between the costa and crista iliaca is more suitable for sub-umbilical; because it provides analgesia below the T10 level. The STAPB applied obliquely from below the xiphoid to the iliac crest, may be appropriate for upper abdominal surgeries; it covers the T6-T9 dermatomes [7-9]. Another alternative for upper abdominal surgeries is the rectus sheath block (RSB), which creates a sensory block in the intercostal nerves at the T7-T12 levels extending on the anterior abdominal wall from the xiphoid to the symphysis pubis [10]. For upper abdominal surgery, the RSB and STAPB may be an suitable alternatives. Moreover, for midline incisions extending from the xiphoid to the symphysis pubis, bilateral RSB or STAPB are required in addition to bilateral PTAPB to cover both the lower abdomen and the anterior wall of the upper abdomen. Studies have shown the efficacy of USG-guided PTAPB, STAPB and RSB separately on postoperative analgesia and opioid use [3,11,12].
Therefore, we aimed to investigate whether STAPB or RSB combined with PTAPB would be more effective for postoperative analgesia in gynecological cancer operations performed primarily through midline laparotomy. Second, we evaluated the intra- and postoperative opioid consumption, intraoperative hemodynamics, adverse effects and length of hospital stay.
MATERIALS AND METHODS
Ethical approval
This single-center, prospective, randomized trial was designed in accordance with the principles of the Declaration of Helsinki and was approved by the ethics committee of Başakşehir Çam and Sakura City Hospital (protocol no: 2023-596, date: 22.11.2023). The clinical trial was also registered (NCT06342076) .
Patient population, randomization, and blinding
Patients aged >18 years with American Society of Anesthesiologists physical status of II-III, who underwent gynecologic cancer surgery through a midline incision and with obtained written informed consent were included in the study. Patients with a local anesthetic allergy, body mass index (BMI) > 40 kg/m2, chronic pain, history of previous abdominal surgery, and refusal or inability to cooperate with postoperative patient-controlled analgesia (PCA) were excluded from the study.
Based on the power analysis performed by predicting the effect of the primary objective on pain scores, the minimum sample size was determined to be 12 for each group with an effect size of 1.4, 5% margin of error and 95% power. Fifty patients were included in the study. By using MedCalc 18.2.1 software (0: STAPB, 1: RSB), the patients were randomized in a 1:1 ratio into the STAPB and RSB groups. The patients were blinded to the study allocation. At the end of the surgery, surgical dressings were applied in the same fashion regardless of group allocation. One anesthetist performed all blocks; another assessed the pain scores and postoperative outcomes. The anesthetist assessing the pain scores was blinded to the study groups.
In the STAPB group, one patient was excluded because of the need for high-dose vasopressors & inotropes due to significant bleeding. In the RSB group, two patients who could not use PCA during the postoperative follow-up were excluded (Fig. 1).
Study protocol
All patients were evaluated the day before surgery and were informed about the use of the numeric rating scale (NRS) for pain (0 = no pain; 10 = worst imaginable pain) [10] and PCA. No medication was administered to the patients before surgery. In addition to American Society of Anesthesiologists-standardized monitoring in the operating room i.e., [(continuous heart rate (HR), noninvasive blood pressure (MAP), noninvasive oxygen saturation (SpO2), end-tidal carbon dioxide and temperature], patient state index (PSI) for depth of anaesthesia, near-infrared spectroscopy (NIRS) for cerebral oxygenation and noninvasive advanced hemodynamic monitoring for fluid management (Masimo SET, Masimo Co.) were also applied. After routine anesthesia, orotracheally intubated patients were connected to a mechanical ventilator. Remifentanil (0.05-0.3 mcg/kg/min) and sevoflurane (MAC: 0.8-1) were used for the maintenance of anesthesia with a PSI of 25-50. Invasive arterial monitoring was performed for all patients. At the end of the surgery, 8 mg each of dexamethasone and of ondansetron were administered intravenously for antiemetic purposes during the postoperative period. The same surgical team performed all surgeries to avoid the effect of the surgical procedure on postoperative pain.
After the induction of postoperative analgesia, both groups underwent USG-guided bilateral PTAPB in addition to STAPB or RSB, according to randomization. Asepsis-antiseptic conditions were provided for all blocks; an in-plane technique was used with a high-frequency ultrasonography probe (12-15 MHz, Hitachi Arietta 65). After hydrodissection with 1-2 ml of saline for each block, 20 ml each of 0.25% bupivacaine for PTAPB and 0.125% bupivacaine for STAPB and RSB were applied. USG confirmed the spread of the local anesthetic. A maximum of 150 bupivacaine injections were administered to each patient.
In the ward, all patients were routinely administered 1 g paracetamol at 8 h intervals and 75 mg of diclofenac sodium at 12 h intervals. For 24 h, PCA was administered using intravenous morphine (PCA: 0.25 mg/ml morphine, 100 ml volume, 2 ml lock time, 20 min; maximum dose, 2 mg in 4 h).
Block application protocols
1. Posterior transversus abdominis plane block (PTAPB)
PTAPB was performed using an in-plane technique parallel to the crista iliaca and mid-axillary line. After visualizing the three muscle layers (i.e., external oblique, internal oblique and transversus abdominis muscles) were visualized parallel to each other on the abdominal wall, the fascia between the internal oblique and transversus abdominis muscles was targeted using a 20-gauge block needle (Stimuplex® Ultra 360®, 0.9×100 mm, B. Braun). For this block application, the correct needle position was confirmed by hydro-dissection using 1-2 ml of saline and 20 ml of 0.25% bupivacaine. Twenty milliliters was applied to each side, for a total of 40 ml.
2. Subcostal transversus abdominis plane block (STAPB)
For STAPB, the rectus muscle was visualized under the xiphoid; the transversus abdominis muscle was visualized under the rectus abdominis muscle by advancing laterally under the costa. The probe was advanced until visualizing the linea semilunaris. The needle was advanced until reaching the fascia between the rectus abdominis and transversus abdominis muscles. For this block application, the correct needle position was confirmed by hydro dissection using 1-2 ml of saline and 20 ml of 0.125% bupivacaine. Twenty milliliters was applied to each side, for a total of 40 ml .
3. Rectus sheath block (RSB)
For the RSB, the rectus muscle was visualized under the xiphoid midline. The needle was advanced through the posterior fascia of the rectus muscle to its posterior aspect in association with the peritoneum. For this block application, the correct needle position was confirmed by hydro-dissection using 1-2 ml of saline and 20 ml of 0.125% bupivacaine. Twenty milliliters was applied to each side, for a total of 40 ml.
Tracking parameters
Demographic data (age, and BMI) and American Society of Anesthesiologists clinical classifications were recorded. Hemodynamic parameters (HR, MAP, and SpO2) and NIRS scores were recorded preoperatively (T1), after the block (T2), 10 min after block (T3), and after the extubation (T4). The total amount of intraoperatively administered remifentanil was determined. After extubation, the use of PCA in the postoperative recovery unit was initiated after repeated explanation. Patients with a modified Aldreate score > 9 were transferred to the ward. The following were also recorded and analyzed: NRS values at the 1st, 6th, 12th, and 24th postoperative hours, total opioid (morphine, mg) used in 24 h; demand and bolus requirements; length of hospital stay; adverse effects such as nausea and vomiting; surgical complications.
Sample size calculation
Based on the power analysis performed by predicting the effect of the primary objective on pain scores, the minimum sample size was determined to be 12 for each group with an effect size of 1.4, 5% margin of error and 95% power.
Statistical analysis
Statistical analyses were performed using NCSS 11 (Number Cruncher Statistical System, 2017 Statistical Software). In our study, frequency and percentage values were given for the variables. Mean, standard deviation, median, minimum and maximum values were calculated for continuous variables. A regular distribution analysis of continuous variables was performed using the Kolmogorov-Smirnov test. Chi-square analysis was used to determine the relationships between categorical variables. When appropriate, categorical variables were assessed using the Fisher's exact test and Fisher-Freeman- Halton test. An independent samplea t-test was used to compare the two groups in terms of continuous independent variables with a normal distribution. The Mann-Whitney U test was used to compare two independent groups for variables that did not meet the assumption of normal distribution. For independent variables that did not have a normal distribution, the Wilcoxon's signed-rank test was used to compare the two groups. A P value < 0.05 was considered statistically significant.
RESULTS
The data of 47 patients; (24, STAPB group; 23, RSB group); who underwent gynecologic cancer surgery, were analyzed.
Upon analyzing the demographic data, their age, BMI, American Society of Anesthesiologists clinical classification, surgical diagnosis (ovarian or endometrial), and pathology rates (benign or malignant) were found to be similar. Operative times were longer in the STAPB group than in the RSB group (P > 0.05), although not significantly (252 ± 88.8 and 217.3 ± 62.3, respectively) (Table 1).
Intraoperative hemodynamic parameters (i.e, HR, MAP, central and peripheral oxygenation (SpO2, NIRS right and left) were similar in both groups (Fig. 2).
During the postoperative period, the median NRS values were significantly lower in the STAPB group than in RSB group at 1, 12 and 24 h (P < 0.05); whereas the pain scores at 6 h were similar (Fig. 3).
The total amount of intraoperative remifentanil was similar in both groups (P > 0.05). In the STAPB group, number of opioid requests, number of boluses and total amount of opioids used were significantly lower when the PCA device was used for 24 h postoperatively (P < 0.05). No rescue analgesics were required in either group except for routine applications (Fig. 4).
No significant differences were observed in the length of hospital stay, postoperative nausea and vomiting, or surgical complications (Table 2).
DISCUSSION
In open gynecologic cancer surgeries where in an upper abdominal incision was added in addition to a lower abdominal incision, the NRS values at the 1, 12 and 24 h were lower in the STAPB group, which we applied in addition to PTAPB, as compared to the RSB group; the opioid demand and bolus numbers as well as the total opioid amounts used with the PCA device in the first 24 h postoperatively were also lower.
Postoperative pain involves a wide range of issues, such as patient comfort, delay in mobilization, length of hospital stay, morbidities, and related costs [13]. Therefore, the treatment of acute postoperative pain during major surgeries is one of the cornerstones of the ERAS protocols. Although epidural analgesia remains the gold standard according to the ERAS protocols, its use is decreasing in current practice owing to side effects such as motor block and hypotension [4,14]. Peripheral trunk blocks, which reduce the need for opioids and related complications by providing optimum postoperative analgesia, facilitate patient mobilization, have no severe systemic effects such as hypotension, are less invasive, and are the most important part of multimodal analgesia with the widespread use of USG [15]. In our clinic, trunk blocks with a lower systemic side effect profile were preferred because of the invasive properties of the epidural catheter and the delayed mobilization due to motor block in our patient group who underwent major gynecologic cancer surgeries, were of advanced age, and with high comorbidities; along with frailty caused by cancer. Although there is no definite clarity regarding when to apply the blocks, those performed after induction have reportedly been more effective [16,17]. Although blocks performed at these four sites may seem time-consuming and cumbersome, they are easier to perform and have fewer side effects than central blocks. Compared with epidural blocks, the use of USG also confirmed local anesthetic spread. This facilitates block construction and increases operator confidence. Therefore, we prefer post-induction applications in clinical practice.
Although USG-guided STAPB provides analgesia for both lower and upper abdominal surgeries, it provides more effective analgesia than PTAPB in upper abdominal surgeries [9,11]. Although STAPB and RSB provide more effective analgesia for upper abdominal surgery, RSB must be administered in high volumes to reach the T6 dermatome [9,18]. Owing to the variation in the thoracolumbar nerves and the associated differences in dermatomal spread, quadruple TAPB, rather than classical TAPB, is recommended for anterior abdominal wall blockade [6]. In major abdominal surgeries, STAPB provides adequate analgesia when used with classical TAPB as part of the four-quadrant TAPB [19].
The combination of TAP and RSB applied in upper abdominal surgeries has been shown to reduce postoperative pain scores and opioid consumption as compared with the control group [20,21]. TAP and RSB have reportedly been more effective in postoperative analgesia and in reducing opioid consumption than wound infiltration in upper abdominal surgeries [22]. In this study in which only STAPB or RSB was blocked continuously with a catheter for postoperative analgesia in gynecologic midline cancer surgeries, pain scores and opioid consumption in the first postoperative 24 h were lower in the group wherein subcostal TAP was applied as compared to RSB. However, in this study, no block was applied to cover for lower abdominal surgery [23]. Furthermore, in which intravenous PCA was used instead of a catheter and, in addition to blocks for postoperative analgesia, we used STAPB or RSB to provide somatic analgesia to the upper abdomen owing to the insufficient spread of PTAPB to the thoracic dermatomes.
Dermatomal spread in peripheral blocks may vary depending on the concentration, volume and anatomical variations of the local anesthetic applied. In this application, high volumes and low concentrations of local anesthetics are preferred to prevent dose-related local anesthetic toxicity [24,25]. Although the level of dermatomal spread was not controlled in our study, no postoperative local anesthetic systemic toxicity was observed in our patients; the doses of the local anesthetic drugs used were below the daily maximum toxic levels.
Although intravenous opioids are frequently preferred for postoperative analgesia in major abdominal surgeries, side effects, such as nausea, vomiting, hypotension, respiratory depression, pruritus and ileus, should not be ignored [26]. Intravenous high-dose opioids used postoperatively may increase postoperative nausea and vomiting as well as length of hospital stay [27]. In our study, side effects such as nausea and vomiting remained similar and did not affect the length of hospital stay, owing to the benefit of peripheral blocks and the low amounts of opioids used postoperatively in both groups (3.7 ± 3.7; 6.8 ± 4.4).
Limitations
The current study had some limitations. It was studied at a single institution, and the block consisted of a single injection. Although pain assessment varies according to individual factors and personal expectations, adequate intraoperative analgesia is often not achieved. Although we controlled the depth of anaesthesia with PSI monitoring, applied targeted fluid management with advanced hemodynamic monitoring, and provided hemodynamic stability, the intraoperative pain monitoring with hemodynamic parameters may still have been insufficient. In this study, it was not optimal to evaluate patients only in the first postoperative 24 h at 6 h intervals and at rest. A single observer did not conduct the assessment, which may have caused inter-observer bias. Although postoperative pain affects the length of hospital stay, many other factors, including social conditions, health care systems and personal care, affect the length of hospital stay. Therefore, in future studies, we recommend pain follow-up with mobilization at more frequent intervals.
Conclusions
Peripheral nerve blocks may be an alternative method in major surgeries due to their advantages, such as avoiding motor blockade caused by epidural blocks and facilitating early mobilization, without causing side effects like hypotension. In this study, STAPB added to PTAPB provided more effective analgesia than RSB for postoperative pain management in major open gynecologic cancer surgeries.
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