Postoperative Analgesic Efficacy of Bilateral Transversus Abdominis Plane Block in Patients Undergoing Midline Colorectal Surgeries Using Ropivacaine: A Randomized, Double-blind, Placebo-controlled Trial.

BACKGROUND: Ultrasound-guided transversus abdominis plane (TAP) block is done as a part of multimodal analgesia for pain relief after abdominal surgeries. This prospective randomized, double-blind, placebo-controlled trial was conducted to evaluate the postoperative analgesic efficacy of bilateral TAP block in patients undergoing midline colorectal surgeries using ropivacaine.
MATERIALS AND METHODS: Eighty patients scheduled for elective colorectal surgeries involving midline abdominal wall incision under general anesthesia were enrolled in this prospective randomized controlled trial. Group A received TAP block with 20 ml of 0.2% ropivacaine on either side of the abdominal wall, and Group B received 20 ml of normal saline. The time to request for rescue analgesia, total analgesic consumption in 24 h, and satisfaction with the anesthetic technique were assessed.
RESULTS: The mean visual analog scale scores at rest and on coughing were higher in control group (P > 0.05). Time (min) to request for the first rescue analgesia was prolonged in study group compared to control group (P < 0.001). The total tramadol consumption in 24 h postoperatively was significantly high in control group (P < 0.001). Nausea/vomiting was more common in control group (P > 0.05). The level of satisfaction concerning postoperative pain control/anesthetic technique was higher in study group (P < 0.001).
CONCLUSION: TAP block produces effective and prolonged postoperative analgesia in patients undergoing midline colorectal surgery. It is a technically simple block to perform with a high margin of safety. It produces a considerable reduction in mean intravenous postoperative tramadol requirements, reduction in postoperative pain scores, and increased time to first request for further analgesia, both at rest and on movement.

RCT Entities:   Population Interventions Outcomes

INTRODUCTION

Effective and appropriate postoperative pain management requires a proactive approach using a variety of treatment modalities and techniques to obtain an optimal outcome with respect to facilitating rapid recovery and returning to full function, allowing early discharge from the hospital, improving quality of life for the patient, and reducing morbidity. One such regional technique in this multimodal or balanced analgesia approach is transversus abdominis plane (TAP) block.[1] The TAP block provides a good analgesia after abdominal operations, among which the colorectal operations are the most frequently performed procedures.[2] Postoperative pain requiring bed rest and persistent gastrointestinal dysfunction are key factors keeping patients in the hospital.[3] Opioids remain the mainstay of postoperative pain relief but can result in significant adverse effects including sedation, nausea, vomiting, urinary retention, respiratory depression, delayed recovery of colonic mobility, and prolonged postoperative ileus.[45] Although epidural analgesia traditionally had a key role in postoperative pain management after colorectal surgery, the technique is labor-intensive and has the risk of serious neuraxial morbidity, albeit rare.[6]

TAP block is a new, rapidly expanding regional analgesic technique that provides analgesia following abdominal surgery. TAP block became increasingly popular worldwide because of its relative simplicity and efficacy along with minimal side effects. It involves a single bolus injection of local anesthetic into the anatomical compartment to saturate the somatic afferents before they leave the TAP to supply anterior abdominal wall from T8 to L1 dermatome through the lumbar triangle of Petit. TAP block is particularly useful for cases when an epidural is contraindicated or refused.[7] The block can be performed unilaterally (e.g., appendicectomy) or bilaterally when the incision crosses the midline (e.g., Pfannenstiel incision). A single injection can be used, or a catheter inserted for several days for the analgesic benefit. Apart from usual beneficial effects of regional anesthetic technique on postoperative morbidity, TAP block reduces the surgical stress response.[8]

The increasing use of TAP block as a form of pain relief after abdominal surgery warrants evaluation of its effectiveness as an adjunctive technique to routine care and when compared with other analgesic techniques.[9] Hence, the present study was conducted to evaluate the postoperative analgesic efficacy of ultrasound-guided TAP block after colorectal surgery.

MATERIALS AND METHODS

The current study was conducted in a tertiary care hospital. After obtaining approval from the Institutional Ethical Committee and written informed consent, eighty patients of physical status American Society of Anesthesiologists (ASA) Classes I and II aged 25–60 years of either sex, scheduled for elective colorectal surgeries involving midline abdominal wall incision under general anesthesia, were enrolled for this prospective randomized controlled trial.

Exclusion criteria were history of relevant drug allergy, morbid obesity (body mass index >40 kg/m2), local site sepsis, opioid dependence. The patients were clinically assessed, evaluated, and investigated before anesthesia. The visual analog scale (VAS) as the method of rating pain was explained to all the patients before surgery. Patients were kept fasting for 8 h and received 150 mg ranitidine as premedication. On arrival to the operating room, an intravenous (IV) access using 18-gauge cannula was established. Standard monitoring including electrocardiogram, blood pressure, and pulse oximetry, end-tidal carbon dioxide monitoring, neuromuscular monitoring were instituted. Anesthesia was induced with propofol (2 mg/kg) and morphine sulfate (0.1 mg/kg). Neuromuscular blockade was achieved with atracurium (0.5 mg/kg) and subsequently appropriate sized cuffed endotracheal tube was placed in. Anesthesia was maintained with oxygen (33%), nitrous oxide (66%), and isoflurane. TAP block was performed at the end of the surgery. The patients were randomly allocated to two groups:

Group A (study group): TAP block with 20 ml of 0.2% ropivacaine on either side of abdominal wall

Group B (control group): TAP block with 20 ml of normal saline on either side of the abdominal wall.

The allocation sequence was generated by a random number table, and group allocation was concealed in a sealed envelope. The patients and the investigators performing the block and providing postoperative care were blinded to group assignment. Study solutions were prepared by an anesthesiologist not involved in performing block or data collection. All patients received IV ondansetron (0.1 mg/kg) and IV paracetamol (20 mg/kg) 30 min before the completion of surgery. At the end of surgery, neuromuscular paralysis was reversed by neostigmine (0.04 mg/kg) and glycopyrrolate (0.01 mg/kg). Tracheal extubation was done once the criteria for neuromuscular blockade were met.

Technique of transversus abdominis plane block

In our study, we used ultrasound-guided technique for giving TAP block. After optimal positioning with the patient supine, the target area was properly draped under all aseptic precautions using chlorhexidine in alcohol. The ultrasound probe was transversely oriented to the anterolateral abdominal wall where the three muscle layers were most distinct. After identification of the TAP between the internal oblique and transverse abdominis muscles, the probe was moved posterolaterally to lie across the midaxillary line just superior to the iliac crest (i.e., over the triangle of Petit). A 50 mm 22-gauge spinal needle was used in our study. The block needle was then introduced anteriorly and advanced in an in-plane approach. A needle tip was directed into the plane below internal oblique and transversus abdominis muscles and was followed by insertion of 20 ml of 0.2% ropivacaine or normal saline. The TAP block was then performed on opposite side using a similar technique.

At the end of surgery and emergence from anesthesia, patients were transferred to the postoperative ward. Postoperatively, patient's heart rate (beats/min), mean arterial pressure (MAP) (mmHg), and oxygen saturation were monitored for 24 h. The presence and severity of pain, nausea, vomiting, and rescue analgesia requirement were assessed postoperatively at 0, 0.5, 1, 2, 4, 6, 12, and 24 h by an investigator blinded to group allocation. The severity of pain was assessed using a 10 cm VAS (0 - no pain and 10 - worst imaginable pain). Tramadol (2 mg/kg) IV was administered to the patient if the VAS was >3 as rescue analgesia. The time to request for rescue analgesia, total analgesic consumption in 24 h were recorded. Rescue antiemetic was given with ondansetron (4 mg) IV when patients complained of nausea or vomiting. Patient satisfaction with the anesthetic technique was assessed 24 h postoperatively using an 11-point scale (0 - not satisfied; 10 - fully satisfied).

Statistical analysis

Statistical software SPSS (version 16.0, SPSS Inc. Chicago, IL., USA) and Microsoft Excel were used to carry out the statistical analysis of data. Data were analyzed by means of descriptive statistics, namely, means, standard deviations, and percentages and presented by means of bar and line diagrams. For parametric data, Student's independent t-test was employed. Chi-square test or Fisher's exact test, whichever appropriate, was used for nonparametric data. P < 0.05 was considered statistically significant.

RESULTS

There was no statistically significant difference (P > 0.05) between the study and control groups with respect to demographic characteristics such as age, weight, gender, ASA classification, and duration of surgery [Table 1]. Although the heart rate was higher with a mean of 82.63 ± 5.30 in control group compared to 81.31 ± 3.87 in study group, the difference was not statistically significant (P = 0.206). MAP was showing statistically insignificant difference (P = 0.071) with a mean of 91.33 ± 2.23 in study and 92.37 ± 2.71 in control groups. Oxygen saturation was comparable between two groups with a mean of 98.70 ± 0.44 and 98.62 ± 0.51 in study and control groups, respectively [Table 2]. The mean VAS score at rest in study group was 1.74 ± 0.70 and in control group was 3.46 ± 0.57 with P < 0.001 [Table 3 and Figure 1]. VAS score on coughing showed statistically highly significant difference (P < 0.001) with a mean of 2.03 ± 0.65 in study group and 3.71 ± 0.52 in control group [Figure 2]. Time (min) to request for the first rescue analgesia was assessed in 24 h which was prolonged in study group (183.9 ± 35.92 min) compared to control group (32.6 ± 13.67), and it was statistically significant (P < 0.001) [Figure 3]. Total tramadol consumption in 24 h postoperatively was significantly high in control group with a mean of 312.5 ± 75.74 than in study group (145 ± 84.58) (P < 0.001) [Figure 4]. Of forty patients in study group, five patients (12.5%) had nausea and three patients (7.5%) vomiting. In control group, of forty patients, eight patients (20%) had nausea and five patients (12.5%) had vomiting [Table 4]. The difference was statistically insignificant between two groups (P > 0.05). The level of satisfaction concerning postoperative pain control/anesthetic technique was higher in study group with a mean of 8.3 ± 0.64 compared to control group with a mean of 5.7 ± 0.57. The difference was highly significant between two groups (P < 0.001) [Table 5 and Figure 5].

Table 1

Demographic data of the two groups

Table 2

Comparison of vital parameters (mean±standard deviation) between the two groups

Table 3

Pain scoring and analgesic requirement

Figure 1

Comparison of pain score at rest (visual analog scale; VASREST) between the two groups

Figure 2

Comparison of pain score on coughing (visual analog scale; VASCOUGHING) between the two groups

Figure 3

Comparison of time to first request of tramadol

Figure 4

Comparison of tramadol requirement (mg) in 24 h

Table 4

Comparison of adverse effects

Table 5

Comparison of patient satisfaction with the anesthetic technique

Figure 5

Comparison of level of patient satisfaction concerning postoperative pain relief/anesthetic technique between the two groups

DISCUSSION

In patients with abdominal surgery, multimodal analgesic technique reduces morbidity, cost, and hospital stay.[10] Although systematically administered opiates and central neuraxial techniques cause considerable adverse effect, they remain the mainstay analgesic modality after abdominal surgery.[51112] Nowadays, peripheral nerve block techniques have been introduced to the practice of anesthesia to prevent surgical abdominal pain successfully and thereby preventing problems associated with the use of systemic opioids or central neuraxial blocks.[131415] TAP block, in which analgesia to the skin, muscles of the anterior abdomen, and parietal peritoneum are obtained, is one of the new techniques used to block the sensory afferent nerves of the anterior abdomen.[1316] The description of the landmark technique for performing TAP block advocated a single entry point, the triangle of Petit, to access a number of abdominal wall nerves hence providing more widespread analgesia.[17] More recently, ultrasound-guided TAP block has been described with the promise of better localization and deposition of the local anesthetic with improved accuracy.[7] TAP block reduces postoperative analgesic consumption, prolongs the time to first analgesic request, and reduces opioid-related side effects.[15] In our study, TAP block was given at the end of surgery using the ultrasound-guided technique. This technique facilitates easy needle visualization so as to prevent improper needle placement outside the muscle or the puncture of the organ situated there. Moreover, a hypoechoic layer, created by injection of local anesthetic, was also easily visualized.

Our observations with respect to demographic characteristics, ASA status, and duration of surgery were concordant with the study conducted in 2011 by Bharti et al., wherein they evaluated the analgesic efficacy of TAP block in colorectal surgeries using 20 ml of 0.25% bupivacaine (TAP group) or 20 ml normal saline (control group) on each side of the abdominal wall.[18] The hemodynamic parameters between two groups were also comparable in our study. These findings were in accordance with the study done by Bharti et al. and Bhattacharjee et al.[1819]

Our results with regard to pain scores were consistent with those of Bharti et al.,[18] who found that patients in the TAP group had significantly lower pain scores at rest and when coughing as compared with the control group at all time points. Similar results were obtained by McDonnell et al.,[16] Sharma et al.,[20] and Niraj et al.[21] Most of the prospective studies with the exception of the Cochrane review and meta-analysis agreed with our results that TAP block decreases the postoperative pain scores both at rest and on coughing in patients undergoing abdominal surgeries over 24 h postoperative period.[22]

Our results regarding total analgesic consumption in 24 h and time to first request of analgesia were consistent with that of Bharti et al.,[18] McDonnell et al.,[16] and Molla et al.[9] Incidence of nausea and vomiting was low in both groups; 20% of patients had nausea and 12.5% vomiting in control group, whereas 12.5% of patients had nausea and 7.5% vomiting in study group. Postoperative nausea and vomiting were low in study group as compared to control group, but the difference was statistically insignificant. Our results were consistent with the study of Bharti et al.[18] but contrary to McDonnell et al.[16] The contradiction may have been attributable to the prophylactic use of antiemetic injection ondansetron (0.1 mg/kg) 30 min before the completion of surgery in our study. The patients were highly satisfied in study group in a postoperative period of 24 h because of reduction in intensity of pain, less opioid use, and less opioid-related side effects.

In our comparative study, there were more or less no complications attributable to TAP block. In general, TAP block has so far displayed a good safety profile. A large incentive for the widespread use of TAP block is the fact that there are few complications attributable to TAP block in the current literature. Although the TAP block complications reported are infections, hematomas, nerve injuries, symptoms of toxic action of anesthetics drug related to its administration into vessel or too high dose, puncture of peritoneal cavity, intestinal perforation, puncture of liver, we did not report any such complication, because in our study, ultrasound-guided technique was used which is safe as it helps direct visualization of needle tip so as to prevent the visceral injury.

The results of our study showed that TAP block provides effective postoperative analgesia after colorectal surgery, decreasing the postoperative opioid requirement and opioid-related side effects so as to give good patient satisfaction in the postoperative period. The use of ultrasound helped us accurately deposit local anesthetic in the correct neurovascular plane, minimizing the risk of systemic toxicity and failed blocks. It also made possible real-time visualization of the shaft and the tip of the needle as well as the spread of injectate.

CONCLUSION

We conclude that TAP block produced effective and prolonged postoperative analgesia as compared with standard therapy in patients undergoing midline colorectal surgery. It is a technically simple block to perform with a high margin of safety, especially with ultrasonography guidance. It showed a considerable reduction in mean IV postoperative tramadol requirements, reduction in postoperative pain scores, and increased time to first request for further analgesia, both at rest and on movement. Although TAP block provides effective postoperative analgesia after colorectal surgery, it requires confirmation by further studies using different study design and various groups of patients (children, obese, elderly). As a final recommendation, we believe that the block should be considered in all patients undergoing midline abdominal surgery unless contraindicated.

Financial support and sponsorship

Nil.

Conflicts of interest

There are no conflicts of interest.