Transversus Abdominis Plane Block versus Ilioinguinal/Iliohypogastric Nerve Block with Wound Infiltration for Postoperative Analgesia in Inguinal Hernia Surgery: A Randomized Clinical Trial.

BACKGROUND: Various analgesic modalities have been used for postoperative analgesia in patients undergoing inguinal hernia surgery. In this randomized clinical trial, we have compared the analgesic efficacy of transversus abdominis plane (TAP) block with that of ilioinguinal/iliohypogastric (IIIH) nerve block with wound infiltration in patients undergoing unilateral open inguinal hernia repair. AIM: The primary objective of this study was to compare the efficacy of postoperative analgesia of ultrasound-guided TAP block and IIIH block with wound infiltration (WI) in patients undergoing open inguinal hernia surgery. SETTINGS AND
DESIGN: This was a randomized clinical trial performed in a tertiary care hospital.
MATERIALS AND METHODS: Sixty patients scheduled for hernia repair were randomized into two groups, Group T and Group I. Postoperatively, under ultrasound guidance, Group T received 20 ml of 0.25% ropivacaine - TAP block and Group I received 10 ml of 0.25% ropivacaine - IIIH block + WI with 10 ml of 0.25% ropivacaine. The primary outcome measure was the time to rescue analgesia in the first 24 h postoperatively. Fentanyl along with diclofenac was given as first rescue analgesic when the patient complained of pain. STATISTICAL ANALYSIS: Statistical comparisons were performed using Student's t-test and Chi-square test.
RESULTS: Mean time to rescue analgesia was 5.900 ± 1.881 h and 3.766 ± 1.754 h (P < 0.001) and the mean pain scores were 5.73 ± 0.784 and 6.03 ± 0.850 for Group TAP and IIIH + WI, respectively. Hemodynamics were stable in both the groups. One-third of the patients received one dose of paracetamol in addition to the rescue analgesic in the first 24 h. There were no complications attributed to the block.
CONCLUSION: As a multimodal analgesic regimen, definitely both TAP block and IIIH block with wound infiltration have a supporting role in providing analgesia in the postoperative period for adult inguinal hernia repair. In this study, ultrasound-guided TAP block provided longer pain control postoperatively than IIIH block with WI after inguinal hernia repair. There were no complications attributed to the blocks in either of the group.

INTRODUCTION

Open inguinal hernia surgery is one of the commonly performed surgical procedures which is associated with substantial postoperative pain and distress. The reported incidence of pain after inguinal hernia repair varies from 0% to 37%.[1] These procedures can be performed under regional anesthesia or general anesthesia and postoperative analgesia can be provided by various analgesic modalities.

A multimodal approach includes nonsteroidal anti-inflammatory drugs, paracetamol infusion,[2] and regional anesthetic techniques such as local infiltration or nerve blocks. The use of local anesthetic for blocks/infiltration is associated with a shorter intra-hospital recovery, lesser morbidity, and overall costs.[3] Infiltration of local anesthetic also improves acute postoperative pain management by decreasing postoperative pain, opioid demand with its resultant complications such as nausea, vomiting, and respiratory depression. It also delays the time to rescue analgesic administration.[4]

Pain and discomfort are important components which are expected after abdominal wall incision.[5] Peripheral nerve blocks such as transversus abdominis plane (TAP) block, abdominal field blocks, and ilioinguinal/iliohypogastric (IIIH) nerve blocks have been described in the literature as means to alleviate pain due to abdominal wall incision.[3] The anterolateral abdominal wall is innervated by thoracolumbar nerves T7 to L1 which emanates from the anterior rami of the spinal nerves and thereby traversing through the plane between the layers of the transversus abdominis and internal oblique muscles of the abdomen.[6] This plane is known as TAP. The iliohypogastric nerve (L1) divides between the internal oblique and transversus abdominis near the iliac crest supplying part of the skin over the inguinal region, gluteal region, and hypogastric region. The ilioinguinal nerve (L1) supplies the upper and medial part of the thigh and also part of the skin covering the genitalia. TAP block and IIIH nerve blocks are regional anesthetic techniques in which local anesthetics are deposited to block the sensory nerves supplying the anterior abdominal wall.[7]

Studies have revealed the efficacy of blind as well as ultrasound-guided TAP block and IIIH nerve block with wound infiltration in providing adequate postoperative analgesia in patients who have undergone inguinal hernia repair when compared to routine parenteral and oral analgesics.[37]

The purpose of this study was to compare the efficacy and duration of analgesia with ultrasound-guided TAP block and IIIH nerve block with wound infiltration in the postoperative period among patients undergoing unilateral open inguinal hernia surgery. The primary outcome of the present study was to compare the duration and quality of postoperative analgesia using visual analog scale (VAS). The secondary outcomes measured were the hemodynamic parameters, analgesic requirements, and complications, if any.

MATERIALS AND METHODS

This study was a randomized clinical trial conducted from October 2014 to April 2016 after protocol approval by the institutional ethical committee and registration at clinical trials registry – India (CTRI/2014/10/007735, October 7, 2014). Sixty patients were randomized into two groups of thirty each which included male patients in the age group between 18 and 65 years belonging to the American Society of Anesthesiologists (ASA) I or II, posted for unilateral open inguinal hernia surgery. Patients were excluded if they had any known drug allergies, other contraindications to spinal anesthesia, bilateral inguinal hernia/irreducible hernia, and body mass index (BMI) >35 Kg/m2. Selected patients underwent a routine preoperative evaluation on the evening before surgery. Informed or written consent was obtained after explanation of the procedure to the patients. Patients were shifted to operation theater complex on the day of surgery. Noninvasive monitors such as an electrocardiogram, noninvasive blood pressure (BP), and pulse oximeter were connected. The subarachnoid block was performed by the operator in all patients in sitting position in L3–L4 space with 3–3.2 ml of 0.5% hyperbaric bupivacaine.

Ultrasound guidance guided transversus abdominis plane block

In Group T after surgery, transverses abdominis plane block was performed using a B Braun Stimuplex needle under ultrasound guidance using Sonosite ultrasound machine with 5–10 MHz linear probe. The transducer was placed in a transverse plane, above the iliac crest, in the region of the anterior axillary line and after visualization of the muscles and intervening plane, 20 ml of 0.25% ropivacaine was injected into the TAP [Figure 1].

Figure 1

Transversus abdominis plane block LA: Local anesthesia, EO: Eternal oblique, IO: Internal oblique, TA: Transversus abdominis, TAP: Transversus abdominis plane block

Ultrasound guidance guided ilioinguinal/iliohypogastric block + WI

In Group I, surgical wound infiltration was done with 10 ml of 0.25% ropivacaine by the surgeon at the end of surgery. Then, IIIH nerve block was performed using a B Braun Stimuplex needle under ultrasound guidance with Sonosite ultrasound machine. A 5–10 MHz linear probe was placed in the axial plane at the level of the anterior superior iliac spine, and after identifying the IIIH nerves in the TAP, 10 ml of 0.25% ropivacaine was given close to the nerves [Figures 2 and 3].

Figure 2

Ilioinguinal/iliohypogastric nerve bundle

Figure 3

Ilioinguinal/iliohypogastric block – LA: Local anesthetic, EO: External oblique, IO: Internal oblique, TA: Transversus abdominis, IIIH: Ilioinguinal/iliohypogastric nerve block

After completion of the block, the patients were kept under observation for 24 h. Intravenous (IV) fentanyl 25 mcg was given as breakthrough/rescue analgesic along with 75 mg of diclofenac intramuscular (IM) (as per ward protocol). Patients were monitored for the need of any subsequent analgesia for 24 h. The parameters assessed for 24 h from the time of administration of block were heart rate, BP, pain at rest using (VAS 0–10; 0 = no pain, 10 = max pain), the time to first rescue analgesia (VAS >5), any adverse effects such as nausea, vomiting, and motor weakness.

Statistical analysis

The sample size was calculated using In Silico online power calculator for two means to calculate the power of the study. This was based on average analgesic consumption in both the groups. We selected a sample size of sixty patients with α error of 0.05 and power of 100%, with thirty patients each in TAP group and IIIH + WI group. The results were generalizable. Randomization was done using computer-generated table of random numbers which were enclosed in opaque sealed envelopes. Patients were randomly assigned to two groups of thirty each. Postoperatively, patients in Group T received ultrasound guidance (USG) TAP block (n = 30), whereas Group I received USG IIIH block with WI (n = 30).

Statistical data were analyzed using Statistical package for social science (SPSS) version 21. The baseline characteristics and outcome variables were described using mean and standard deviation and dichotomous and categorical variables were expressed as percentages. For continuous variables, independent Student's t-test was applied and P < 0.05 was considered statistically significant. For comparing proportions between two groups, Chi-square test was used and P < 0.05 was considered statistically significant.

RESULTS

The demographic data were similar in both the study groups. The subjects in both the groups were well matched with respect to age and weight. The mean age in Group T was 37.2 years and in Group I was 35.2 years. All were male patients with a mean weight of 71 kg in Group T and 72.3 kg in Group I.

The hemodynamic parameters, i.e., heart rate, BP, mean arterial pressures were comparable in both the groups. This suggests that TAP block as well as IIIH nerve block with wound infiltration did not produce any adverse effects on the vital signs of the patient [Figures 4 and 5].

Figure 4

Postoperative heart rate

Figure 5

Postoperative mean arterial pressure

The time to rescue analgesia was one of the primary outcomes and was compared among the two groups. The mean time (in hours) to require rescue analgesia was found to be 5.900 ± 1.881 and 3.766 ± 1.754 for Group T and Group I, respectively. T-test was used to calculate the significance of this difference in the mean time between the two groups. On comparison of these two values, the difference in mean time to rescue analgesia was statistically significant (P < 0.001) [Figure 6].

Figure 6

Mean time to rescue analgesia in both groups

Figure 7 shows mean pain scores at rest between the Group T and I. At 4 h, mean pain score was 4.2 in Group T and 6 in Group I. Beyond 6th h there was no significant difference in the VAS scores [Figure 7].

Figure 7

Mean postoperative pain scores

One-third of patients in both the groups received only one dose of paracetamol 15 mg/kg infusion IV as an additional breakthrough analgesic within the first 24 h of the postoperative period which was not significant. This showed that almost equal number of patients needed (P = 0.791) an additional dose of analgesic following the first analgesic was given.

The main side effect noted was postoperative nausea and vomiting with an incidence of 35%, but the incidence of nausea and vomiting was comparable among the two groups (P = 0.791).

DISCUSSION

Acute postoperative pain following open inguinal hernia repair is maximum during the first 24 h period.[8] Various modalities have been adopted to reduce this pain which includes parenteral opioids, nonsteroidal anti-inflammatory drugs, central neuraxial analgesia, TAP block, IIIH nerve blocks, and wound infiltration with varying results. Among all these techniques, TAP and IIIH blocks are effective and easy to perform with least complications.[4910111213]

Very few studies have compared TAP with IIIH blocks in adults undergoing inguinal hernia mesh repair. Sasaoka et al. and Asad et al. indicated that addition of a genitofemoral block to IIIH nerve block provides better pain relief compared with IIIH block alone.[1415] However, it is quite difficult to block genital branch under ultrasound guidance. Hence, we decided to add wound infiltration along with IIIH nerve block in one group and to compare it with TAP block alone in another group.

In our prospective randomized clinical trial, we compared pain intensity using VAS pain score and 24 h analgesic consumption. We found that the time for VAS to reach >5 (first breakthrough analgesia– fentanyl 25 mcg/IV and diclofenac 75 mg/IM) was longer in TAP group (5.9 ± 1.881) compared to IIIH group (3.76 ± 1.75). The study is similar to a study which compared ultrasound-guided transverses abdominis plane block and IIIH nerve blocks for day care inguinal hernia repair done by Aveline et al.[16] which reported that TAP block patients expressed significantly less pain at rest on VAS scores at 4, 12, and 24 h. Similarly, a meta-analysis was conducted by Yu et al.[17] including all relevant randomized controlled trials in the published literature, to compare the efficacy of TAP block with local anesthesia infiltration for postoperative analgesia. These researchers concluded that TAP block was comparable to local anesthesia infiltration for short-term analgesia; but, they found that TAP block could also provide better long-lasting analgesia, especially at 24 h after surgery.[17] However, in our study, we used IIIH block + wound infiltration with a local anesthetic which resulted in good quality and an equal amount of rescue analgesia in both the groups.

Frassanito et al. compared ultrasound-guided TAP with IIIH block and reported that patients in the TAP group had significantly lower VAS scores immediately after surgery as well as at 24 h compared to IIIH group. They also reported that TAP group had significantly lower VAS on coughing at the end of surgery and at the time of discharge which was similar to our study. However, in their study, IIIH group required increased amount of analgesic consumption for the first 24 h compared to the TAP group. In contrast to their study, in our study, the incidence of consumption of rescue analgesia was lesser even in the IIIH group which can be explained by the fact that we used wound infiltration along with IIIH block while they had used IIIH block alone.[18]

There are some contrasting reports especially in pediatric anesthesia, where it has been found that IIIH blocks are more superior to TAP blocks for herniotomy procedures. It is to be noted that pediatric herniotomy procedures are done with minimal incision without placing a mesh whereas adult patients require extensive dissection along with mesh placement.[19202122]

In our clinical trial, both TAP block group as well as IIIH block group had minimal side effects. The main side effect we noted was postoperative nausea and vomiting with an incidence of 35%. One of the reasons for this could have been the use of fentanyl as rescue analgesia which is emetogenic, otherwise TAP and IIIH blocks are safe with minimal side effects for hernia procedure.

Limitations

There were a few limitations in our study. We only studied male patients of ASA I and II and with a BMI of less than 35 kg/m2. Since the number of females who come for this operation in our institution is very low, we eliminated them to maintain uniformity. The anesthetist in charge was not blinded for the block technique.

CONCLUSION

Both TAP block and IIIH nerve block with wound infiltration are effective regional blocks for open inguinal hernia procedure in adult patients. The time for first rescue analgesia was prolonged in TAP group compared to IIIH group, but total analgesic requirement within the first 24 h remained the same in both the groups with minimal side effects. Hence, both TAP block as well as IIIH block with wound infiltration can be used as effective modalities to control postoperative pain after open inguinal hernia procedures.

Financial support and sponsorship

Nil.

Conflicts of interest

There are no conflicts of interest.