Comparative Study of the Analgesic Efficacy of Intrathecal Fentanyl with Ultrasound-Guided Transversus Abdominis Plane Block after Lower Segment Cesarean Section.

BACKGROUND: This study was conducted to compare the analgesic efficacy of intrathecal fentanyl with ultrasound-guided transversus abdominis plane (TAP) block after lower segment cesarean section. The objectives of the study were to compare the effects of subarachnoid fentanyl versus TAP block with respect to duration of postoperative analgesia, time for first analgesic request, total analgesic consumption in 24 h, time to first breastfeed and Apgar score at 1 and 5 min.
MATERIALS AND METHODS: Sixty-two patients undergoing elective or emergency cesarean delivery were recruited for the study in a prospective, randomized, single-blind manner. The patients were randomly allocated to either intrathecal fentanyl group (Group F) or TAP block group (Group T) after determining the eligibility criteria. Group F patients received subarachnoid block with 10 mg of 0.5% bupivacaine heavy with 25 mcg of fentanyl. Group T patients received subarachnoid block with 10 mg of 0.5% bupivacaine heavy prior to surgery and at the end of surgery, they received TAP block with 0.25% bupivacaine 20 mL on each side.
RESULTS: Group T had significantly longer time for the first analgesic request (7.65 ± 1.23 h) than group F (4.10 ± 0.32 h). The total analgesic consumption in 24 h was significantly less in Group T (1.0 ± 0) than Group F (2.13 ± 0.34). The Visual Analogue Scale scores at rest and on movement were significantly less in Group T than Group F at all-time points. The Apgar score at 1 and 5 min and time to first breast feed were comparable between the two groups. The incidence of side effects was less in Group T.
CONCLUSION: This study indicated that ultrasound-guided TAP block has a better analgesic as well as safety profile compared to intrathecal fentanyl for cesarean delivery. Copyright:

INTRODUCTION

Lower segment cesarean section (LSCS) is one of the most commonly performed surgical procedures in obstetric practice. It is a major surgical procedure after which substantial postoperative discomfort and pain can be anticipated. Up to 79% of women experience pain at the incision site that can last for up to 2 months.[1] Subarachnoid opioids are commonly being used for the management of postoperative pain after LSCS. It seems to be a preferred additive for caesarean section surgery to add fentanyl or sufentanil to intrathecal bupivacaine to improve analgesia time and provide hemodynamic stability and faster return of the motor block and ambulation.[2] Effective pain management after cesarean section represents a unique challenge. Robust mother-infant interaction during the early postdelivery period is thought to be of considerable psychological importance to the mother and to make a substantial contribution to the optimal development of the infant.[3] Inadequate relief of postoperative pain may have a detrimental effect on ambulation, breastfeeding and maternal bonding, while efficient analgesia increases the amount of breastfeeding and weight gain for infants.[4] Therefore, postcesarean section analgesia must provide adequate pain control while allowing the mother to remain active and available to tend to the needs of her newborn baby. Although adhering to the current perioperative care requirements, which include improved postoperative recovery and prompt discharge, it is necessary to resolve the problems associated with inadequate analgesia. Without compromising the standard of service, these priorities must be met.[3] Multimodal analgesia represents an attempt to meet the above-mentioned goals. The use of intrathecal opioids is a crucial component of this approach and patients typically receive intrathecal, systemic or both as components of multimodal analgesia. However, opioids, whether given through intrathecal or systemic route are frequently associated with adverse effects such as nausea, pruritis, sedation and occasionally respiratory depression. Thus, knowledge about alternative (nonopioid) analgesia is important.[5]

A regional analgesic technique that blocks T6-L1 nerve branches and has an emerging role in postoperative analgesia for lower abdominal surgery is the transversus abdominis plane (TAP) block. Multiple injections into the abdominal wall using local anesthetics were originally described in early 1980s. The procedure was modified and described by Rafi in 2001.[6] It is a simple and safe technique which is a potential alternative to spinal opioids for analgesia after cesarean section, whether guided by anatomic landmarks or by ultrasound. However, there are few studies comparing TAP block with spinal opioids. If superior to spinal opioids TAP block would have the advantage of improved analgesia, reduction in opioid-associated adverse effects, and the absence of motor blockade.[5]

Thus, we designed a study that aims to compare the efficacy of postoperative analgesia with a subarachnoid block with bupivacaine with fentanyl and subarachnoid block with bupivacaine with TAP block. Our aim was to observe the time of the first request of analgesia and total rescue analgesic requirements in LSCS during the first 24 h.

MATERIALS AND METHODS

After approval of the Institutional Ethics Committee (VIEC/2016/APP/127, Ethical Committee Registration no: ECR/747/Inst/KA/2015 dated November 16, 2017), this prospective, randomized single-blind study was conducted from January 2018 to June 2019. The study followed to the Helsinki Declaration (World Medical Association, 1995). All study parts were reviewed according to the strengthening the reporting of randomized clinical trials in “CONSORT guidelines.” Informed and written consent was taken from all the patients before enrolment in the study and use of the patient data for research and educational purposes.

Sixty-two patients of the American Society of Anesthesiologists (ASA) physical status I or II undergoing cesarean section through Pfannenstiel incision were included in the study. Patients with body mass index <18 or >35, chronic pain disorder, contraindications for spinal anesthesia, and having a history of drug allergy to local anesthetic drugs were excluded from the study.

Each patient fulfilling the eligibility criteria was randomly allocated into two groups (Group F and Group T) by using the sealed envelope method. Group F (n = 31) patients received intrathecal fentanyl 25 mcg and 10 mg of 0.5% bupivacaine heavy. Group T (n = 31) patients received intrathecal 10 mg of 0.5% bupivacaine heavy and TAP block with 20 mL of 0.25% bupivacaine on each side at the end of surgery.

In the operating room, all patients were monitored by electrocardiogram, noninvasive blood pressure, and pulse oximetry (SpO2). An intravenous (i.v.) line was secured using 18 G cannula and patients were preloaded with 10 mL.kg−1 of ringer lactate over 10–15 min. All patients were explained about their pain measurement by visual analogue scale (VAS; 0 for no pain and 10 for severe intolerable pain). Spinal anesthesia was given in a sitting position under aseptic condition at the L2–L3/L3–L4 intervertebral space. Lumbar puncture was performed using 25G/26G Quincke's spinal needle, confirmed by a free flow of cerebrospinal fluid, and the drug was administered. The parturients were placed in the supine position with 15°–20° left uterine displacement, and supplemental oxygen was delivered through a facemask at 5 L.min−1.

At the end of the surgery, Group T patients received bilateral ultrasound (ACUSON, Siemens Medical Solutions, USA, Inc) guided TAP block with 20 mL of 0.25% bupivacaine. The sterility of the surgical field was maintained, and the puncture area and ultrasound probe were prepared in a sterile manner. The ultrasound probe was placed in between the 12th rib and iliac crest at the level of mid-axillary line. Once external oblique, internal oblique, and transversus abdominis muscles were visualized, 23G Quincke's spinal needle was advanced in an in-plane technique till the plane between the internal oblique and transversus abdominis muscles. Once the tip of the needle was placed between the internal oblique and transversus abdominis muscles, negative aspiration was confirmed and 2 mL of the prepared drug was administered, followed by the remaining 18 mL under direct ultrasonography (USG) guidance. The block was performed with a high-frequency linear probe of 8–13 MHz. The contralateral block was performed using the same technique. All patients received standard analgesia according to obstetric department protocols consisting of rectal diclofenac 50 mg bd, first dose inserted at the end of surgery. They received i.v. tramadol 1 mg.kg−1 as first rescue analgesic and i.v. paracetamol 15 mg.kg−1 as second rescue analgesic when VAS was more than 4.

Intraoperatively, patients were monitored and recorded the heart rate, systolic, and diastolic blood pressure every minute for the first 5 min, then 30, 60, 90, and 120 min after the wound closure up to the time when rescue analgesia was given or whichever was earlier. The time taken to reach the optimum sensory level was measured every 5 min by observing the reaction to the pin prick. The time taken to attain complete motor block and the duration of motor block were assessed using a modified Bromage scale. The duration of sensory block was assessed by observing the reaction to pin prick. VAS (0–10 cm) was assessed at rest and on movement, every 2 h up to 6 h followed by every 6 h up to 24 h. The time for first analgesic request and total analgesic consumption in 24 h was recorded. The neonatal Apgar scores at 1 and 5 min after birth were noted and the time to first breastfeed was observed from the end of surgery.

Side effects such as nausea and vomiting, pruritis, sedation, respiratory depression, and constipation were assessed. Nausea and vomiting were assessed on a categorical scoring scale (0 = no symptoms, 1 = only nausea, 2 = nausea and vomiting). The sedation level was measured as a sedation score (0 = awake and alert, 1 = quietly awake, 2 = asleep but easily excited, 3 = deep sleep, reacting to a painful stimulus). Patients were labeled to be sedated if score >2.

Statistical analysis

A prospective sample size calculation indicated that 31 patients were required in two groups to have 90% power to detect a 25% difference at Type 1 (α) error of 0.05 for the duration of analgesia and assuming a drop out of 10%. The Statistical analysis was performed by STATA 11.2 (Stata Corp., College Station, TX, USA). Students independent sample t-test was used for hemodynamic parameters, block characteristics, analgesic consumption, visual analog and Apgar score. Chi-square test used to measure the association between variables obtained. P < 0.05 was considered statistically significant.

RESULTS

A total of 62 patients were enrolled in the study. One patient from each group was excluded because of breach in the postoperative analgesic protocol. Thirty patients were analyzed in each group [Figure 1]. There was no significant difference in age, ASA grade, duration, and type of surgery [Table 1]. The VAS pain score was significantly lower in Group T at rest and on movement at all-time intervals [Table 2].

Figure 1

Consort flow diagram

Table 1

Demographic characteristics

Parameters	Group F (n=30)	Group T (n=30)	P
Age (years)	25.70±4.65	26.03±4.12	0.769
ASA I/II	0/30	0/30	-
Elective/emergency	17/13	13/17	0.302
Duration of surgery (min)	88.67±8.80	91.67±9.22	0.203

Values are presented as mean±SD and proportion. Student independent t-test/Chi-square test used to compare the mean±SD/proportions, P<0.05 significant. SD=Standard deviation, ASA=American Society of Anesthesiologists

Table 2

Comparison of Visual Analog Scale score at rest and on movement

Group	2 h	4 h	6 h	12 h	18 h	24 h
At rest
Group F (n=30)	0	4.93±0.69	4.17±0.53	3.70±0.47	3.40±0.50	2.87±0.51
Group T (n=30)	0	0.07±0.25	2.17±1.84	2.57±0.86	2.70±0.60	2.60±0.50
P	-	<0.001	<0.001	<0.001	<0.001	0.044
At movement
Group F (n=30)	0	6.27±0.83	5.40±0.62	4.97±0.32	4.87±0.34	4.10±0.71
Group T (n=30)	0	0.97±1.03	3.60±1.83	4.03±1.09	3.73±0.45	3.63±0.49
P	-	<0.001	<0.001	<0.001	<0.001	0.005

Values are presented as mean±SD. Student independent t-test used to compare the data. SD=Standard deviation

The first analgesic request time in TAP block was significantly higher (7.65 ± 1.23 vs. 4.10 ± 0.32, P < 0.001) and the total analgesic requirement was significantly less in 24 h. The time to achieve the maximum level of sensory block was significantly longer in Group F and the duration of sensory block was significantly more in Group F as compared to Group T (222.13 ± 2.29 vs. 195.77 ± 6.86, P < 0.001). However, the time for the complete motor block as well as the duration of motor block was comparable between the groups [Table 3].

Table 3

Block characteristics of both groups

Variables	Group F (n=30)	Group T (n=30)	P
Time to attain maximum sensory block (T5-6)	12.60±0.61	11.57±1.14	<0.001
Time for complete motor block	7.32±0.36	7.38±0.43	0.517
Duration of sensory block	222.13±2.29	195.77±6.86	<0.001
Duration of motor block	183.50±6.04	185.23±7.02	0.309
Time to first analgesic request (h)	4.10±0.32	7.65±1.23	<0.001
Total analgesic consumption in 24 h	2.13±0.34	1.0±0	<0.001

Values are presented as mean±SD. Student independent t-test used to compare the data. SD=Standard deviation

On comparing the mean heart rates at 1, 2, 3, 4, 5, 30, 60, 90, 120, and 180 min, it was found that the mean heart rate was significantly less in Group F at 60, 90, and 120 min (P < 0.05) [Figure 2]. On comparing the systolic blood pressure at 1, 2, 3, 4, 5, 30, 60, 90, 120, and 180 min, it was found that the systolic blood pressure was less in Group F at early phase of subarachnoid block in Group F at 3, 4 and 5 min (P < 0.05) [Figure 3]. Similarly, the diastolic blood pressure was significantly less in Group F at 2, 3, and 4 min (P < 0.05), and significantly more at 120 min (P = 0.013) [Figure 4].

Figure 2

Comparison of heart rate

Figure 3

Comparison of systolic blood pressure

Figure 4

Comparison of diastolic blood pressure

Both groups were comparable in Apgar score at 1 min and 5 min, and time to first breastfeed in patients [Table 4]. Both groups were comparable in pruritus and nausea and vomiting [Table 5]. No patient in either group had adverse effects of sedation, constipation, or respiratory depression.

Table 4

Comparison of Apgar score and time to first breastfeed in patients studied

Group	Apgar score		Time to first breastfeed (min)
	1 min	5 min
Group F (n=30)	7.60±0.50	8.77±0.43	69.17±5.27
Group T (n=30)	7.57±0.50	8.90±0.31	68.17±4.45
P	0.797	0.172	0.430

Values are presented as mean±SD. Student independent t-test used to compare the data. SD=Standard deviation

Table 5

Comparison of incidence of adverse effect

	Nausea and vomiting		Pruritus
	Yes	No	Yes	No
Group F (n=30)	1	29	17	13
Group T (n=30)	3	27	0	30
P	0.301		<0.001

Values are presented as proportion. Chi-square test used

DISCUSSION

LSCS is one of the most performed obstetric surgical procedures. The analgesic regimen should provide safe, effective analgesia with minimal side effects for the mother and child.[7] The benefits of adequate perioperative analgesia are clear, including a reduction in stress response, postoperative morbidity, and improved surgical outcome.[8] Effective pain control accelerates recovery from surgery and bonding of mother and child. Although a multimodal analgesic regimen, single-shot neuraxial analgesic techniques using long-acting opioids, or patient-controlled epidural opioid administration produce effective analgesia, they are associated with a frequent incidence of side effects which reduce overall patient satisfaction.

Over the recent years, there has been growing interest in regional nerve block techniques with promising results on efficacy, as USG-guided technique is safe, effective, and reduces the need for supplemental analgesia, thereby lowering the incidence of drug-related side effects. For a number of abdominal surgeries, including cesarean delivery, TAP block is an abdominal wall nerve block of excellent efficacy.[9]

As a component of spinal anesthesia, the superiority of postcesarean analgesia produced by long-acting spinal opioids over their systemic counterparts,[1011] makes them an integral part of multimodal analgesic regimens.[121314] Since neuraxial anesthesia has been established as the best modality for caesarean delivery, it has become difficult to justify excluding a small dose of intrathecal morphine,[15] given the superior analgesia it produces, the prolonged duration of this analgesia.[161718]

Our study demonstrated that a multimodal analgesic regimen with a TAP block reduces pain scores and rescue analgesic requirements. It also delays the time to first analgesic request and provides better satisfaction with pain relief compared with the standard regimen like a subarachnoid block with fentanyl. Various studies comparing TAP block and subarachnoid block showed that the TAP block produces better analgesia reduces opioid consumption and reduces the incidence of opioid-induced adverse effects.[7192021]

Since neuraxial morphine has been established as the best modality for post cesarean analgesia,[22] various trials have compared the analgesic efficacy of TAP block with intrathecal morphine. They noted that superior analgesia was seen with intrathecal morphine as compared to TAP block but at the expense of adverse effects.[52324] Hence, to reduce the adverse effects of morphine we have used fentanyl as an adjuvant with subarachnoid block.

In our study, we found that the duration of postoperative analgesia and time for the first analgesic request was longer in Group T (7.65 ± 1.23 h) compared to Group F (4.10 ± 0.32 h) which was statistically significant (P < 0.001). The total analgesic consumption in 24 h was reduced by half in Group T (1.0 ± 0) as compared to Group F (2.13 ± 0.34) which was also statistically significant (P < 0.001). The mean postoperative VAS scores at rest and on movement at 2, 4, 6, 12, 18, and 24 h postoperatively were significantly lower in Group T than in Group F (P < 0.05).

Similarly, Srivastava et al.,[9] Eslamian et al.[25] and Tan et al.[20] had observed that the longer time to ask for first analgesia, than patients in the control group, utilized less patient-controlled analgesia (PCA) tramadol and reduced cumulative tramadol usage during the first 24 h after surgery in the TAP block group. In our study, time for first rescue analgesic request in Group F was 4.10 ± 0.32 h which is similar to one study in which the patients received 25 mcg of intrathecal fentanyl and it was found that the time to first PCA demand was 4.3 ± 1.4 h.[3]

McDonnell et al.[7] observed that reduced cumulative postoperative morphine consumption in patients who received TAP block for postoperative analgesia than the patients in the control group. Furthermore, postoperative VAS pain scores at rest and on movement were reduced with TAP block. The reason for a prolonged duration of analgesic effect after TAP blockade may relate to the fact that the TAP is relatively poorly vascularized, and therefore drug clearance may be delayed. Biswas et al.[26] and Khosravi et al.[27] compared the analgesic efficacy of intrathecal fentanyl with hyperbaric bupivacaine after caesarean delivery, showed no significant differences in neonatal Apgar scores at 1 min and 5 min. In our study, also there were no differences in neonatal Apgar scores at 1 min and 5 min.

Abdallah et al.[4] in his review article mentioned the missing outcome of effect of TAP block on breastfeeding. In our study, we found that the time for first breastfeed was comparable between the two groups (69.17 ± 5.27 min vs. 68.17 ± 4.45 min) which signifies that patients in both groups were satisfied with their pain management in the immediate postoperative period and could feed and care for their babies' pain-free. There was no statistical difference in nausea and vomiting, however, pruritus between the groups in our study was statistically different.

Limitations of the study are we did not encounter any ultrasound-guided TAP block complication as the sample size was not enough. We used a single-blinded study design because of ethical consideration; we did not inject normal saline in the other group. Hence, the investigators were unblinded to the treatment received by both groups. We did not compare with intrathecal bupivacaine alone.

CONCLUSION

Our study showed that patients who received TAP block for post cesarean section pain management reported a longer duration of analgesia, lower VAS scores at all-time points till 24 h postoperatively, and less analgesic consumption 24 h postoperatively compared to fentanyl mixed subarachnoid block.

Hence, we conclude that TAP block has the potential to become an important tool in the management of multimodal postoperative pain of cesarean delivery.

Financial support and sponsorship

Nil.

Conflicts of interest

There are no conflicts of interest.