The opioid-sparing efficacy of ultrasound-guided quadro-iliac plane block versus transversus abdominis plane block after cesarean delivery: A randomized controlled trial

Abstract

Background:

Post-cesarean pain comprises somatic and visceral components, yet the transversus abdominis plane (TAP) block addresses only somatic afferents. The quadro-iliac plane block (QIPB) is a novel posterior fascial plane technique theorized to provide broader coverage of both nociceptive pathways. Comparative evidence between these techniques in the obstetric population is lacking.

Methods:

This prospective, randomized, single-blind, controlled trial enrolled 36 ASA I–II parturients undergoing elective cesarean delivery under spinal anesthesia at Mansoura University Hospital (IRB: R.25.04.3145; PACTR202505592518309). Patients were randomized 1:1 to bilateral ultrasound-guided TAP block (n = 18) or bilateral QIPB (n = 18). The primary outcome was total nalbuphine consumption within 24 hours. Secondary outcomes included time to first rescue analgesic request, postoperative Visual Analogue Scale (VAS) pain scores, hemodynamic parameters, and adverse effects.

Results:

Twenty-four-hour nalbuphine consumption was significantly lower in the QIPB group (5.28 ± 0.96 mg vs. 9.56 ± 2.04 mg; P < 0.001), representing a 45% reduction. The time to first rescue analgesia was significantly prolonged with QIPB (9.78 ± 1.22 vs. 7.0 ± 1.32 hours; P < 0.001). VAS scores were significantly lower at 6 and 12 hours postoperatively (P < 0.001 and P = 0.007, respectively). No clinically relevant hemodynamic differences were observed between groups, and adverse event rates were comparable.

Conclusions:

Compared with the TAP block, the QIPB provides superior and more prolonged postoperative analgesia following elective cesarean delivery, with a favorable safety profile. These findings support further evaluation of the QIPB within multimodal Enhanced Recovery After Cesarean protocols, particularly where intrathecal opioid is not employed, and inform the design of future multicenter trials.

Introduction

Optimal postoperative pain management after cesarean delivery should aim to provide effective analgesia while minimizing adverse effects as adequate pain control promotes early ambulation, reduces the risk of thromboembolism, facilitates breastfeeding, improves mother–infant bonding, and lowers the risk of chronic pain and postpartum depression.[1,2] Postoperative pain following cesarean delivery comprises two distinct components: somatic pain arising from the abdominal wall incision, and visceral pain resulting from uterine manipulation and peritoneal handling. The anterior abdominal wall receives its sensory innervation from neural afferents coursing through the fascial plane between the internal oblique and transversus abdominis muscles, including the intercostal, subcostal, iliohypogastric, and ilioinguinal nerves—the primary targets of abdominal wall regional blocks.[3,4]

Regional nerve blocks are increasingly incorporated into multimodal analgesic regimens following cesarean delivery as part of Enhanced Recovery After Surgery (ERAS) pathways. ERAS protocols for cesarean delivery specifically recommend the use of regional anesthesia techniques as a cornerstone of multimodal analgesia, with the goal of minimizing opioid consumption, facilitating early mobilization, and optimizing maternal recovery.[2,5,6] Within this framework, the transversus abdominis plane (TAP) block and the quadro-iliac plane block (QIPB) represent two techniques of growing clinical interest, each targeting distinct nociceptive pathways.

The TAP block has been widely incorporated into multimodal analgesic regimens after cesarean delivery, with multiple trials demonstrating reductions in postoperative pain scores and opioid consumption.[7,8] Its analgesic coverage, however, remains confined to the somatic component of post-cesarean pain, with no reliable reach to the visceral afferents responsible for uterine and peritoneal discomfort.

The QIPB is a novel fascial plane block that targets the interfascial plane between the inner iliac crest and the posterior surface of the quadratus lumborum muscle, where local anesthetic is proposed to distribute widely, achieving coverage of the ilioinguinal, iliohypogastric, subcostal, genitofemoral, and lumbar plexus nerves, thereby providing both somatic and visceral analgesia—a theoretical advantage over the TAP block, which is limited to somatic coverage.[9,10] The bilateral approach has been specifically described for obstetric procedures including cesarean delivery, and the technique has demonstrated promising analgesic efficacy in this population.[10]

Direct comparative evidence between the TAP block and QIPB in the obstetric population remains limited. Most existing studies have evaluated each technique independently against systemic analgesia or placebo rather than conducting rigorous head-to-head comparisons within the same patient population,[10,11] leaving the relative analgesic superiority of one technique over the other yet to be established.

To address this gap, the present randomized controlled trial was designed to directly compare the analgesic efficacy of ultrasound-guided TAP block versus ultrasound-guided QIPB in patients undergoing elective cesarean delivery under spinal anesthesia. The primary objective was to compare total opioid consumption within 24 hours between the two techniques. Secondary objectives included time to first rescue analgesic request, postoperative pain scores, hemodynamic stability, and adverse event incidence, with the hypothesis that the QIPB would provide superior postoperative analgesia as reflected by reduced opioid consumption and lower pain intensity scores during the early postoperative period.

Methods

Study design and setting

This prospective, randomized, single-blind, controlled trial was conducted over a period of 1 year at Mansoura University Hospital, following approval from the Medical Research Ethics Committee, Institutional Review Board (IRB) of the Faculty of Medicine, Mansoura University (IRB approval code: R.25.04.3145; date of approval: 22 April 2025). The trial was prospectively registered with the Pan African Clinical Trials Registry under the registration number PACTR202505592518309 (registered 15 May 2025), in accordance with WHO and ICMJE standards. Written informed consent was obtained from all participants prior to enrolment.

Eligibility criteria

Patients were considered eligible for inclusion if they were aged between 18 and 40 years and classified as American Society of Anesthesiologists (ASA) physical status grade I or II. Patients were excluded if they refused to participate or if they had a documented history of neuromuscular disease, hematological disease, or psychiatric illness.

Sample size calculation

Sample size was estimated based on postoperative analgesic requirements reported by Borys et al.,[12] who conducted a randomized controlled trial comparing the TAP block and the quadratus lumborum block for acute postoperative pain following cesarean section. Using G*Power software (version 3.1.9.7), a two-tailed independent samples calculation was performed with an effect size of 1.36, derived from the estimated group means and standard deviations of 21.28 ± 3.11 mg versus 28.89 ± 7.25 mg reported therein, with an alpha error of 0.05 and a statistical power of 95%. This yielded a minimum required sample of 16 patients per group. To account for an anticipated dropout rate of 20%, the final target sample size was set at a minimum of 18 patients per group.

Randomization and allocation

Eligible patients were randomly assigned in a 1:1 ratio to one of two parallel groups using a computer-generated table of random numbers. Allocation concealment was achieved using sequentially numbered, opaque, sealed envelopes prepared prior to study initiation by an investigator not involved in patient enrolment or outcome assessment. Envelopes were opened in sequence at the time of block administration, after confirmation of eligibility and completion of spinal anesthesia, ensuring that the treating anesthesiologist was unable to foresee upcoming assignments at the point of enrolment.

Blinding

Both blocks were administered by the same experienced anesthesiologist to ensure technical consistency. A second anesthesiologist, who was blinded to group allocation throughout the entire 24-hour observation period, was solely responsible for all postoperative data collection, pain scoring, and adverse event recording; this investigator had no involvement in block administration and was not present during the procedure.

Patient-level blinding was not feasible in this trial. The two techniques require different patient positioning—supine for the TAP block and lateral decubitus for the QIPB—precluding the use of a sham procedure without exposing patients to an additional needle pass for no clinical benefit. The primary outcome, total nalbuphine consumption, is an objective nurse-administered metric unlikely to be influenced by patient awareness of group allocation. The trial is therefore classified as single-blind, with blinding applied at the level of outcome assessment where it most directly protects against detection bias.

Anesthetic management

All patients underwent a standardized preoperative assessment comprising a detailed history, thorough physical examination, and laboratory workup including a complete blood count, coagulation profile, and hepatic and renal function tests. Upon arrival to the operating room, standard monitoring was applied, including continuous electrocardiography (ECG), pulse oximetry, and noninvasive arterial blood pressure measurement. Intravenous access was secured via an 18-gauge wide-bore peripheral cannula. Spinal anesthesia was then administered with the patient in the seated position using a 25-gauge spinal needle at the appropriate lumbar interspace. Intrathecal injection consisted of 2 mL of hyperbaric bupivacaine 0.5%.

Following completion of the cesarean section and skin closure, each patient received the regional analgesic block according to her assigned group, as detailed below.

Block techniques

Transversus Abdominis Plane Block

The patient was positioned supine. Using a high-frequency linear ultrasound probe, the three layers of the lateral abdominal wall musculature were identified in the mid-axillary line between the iliac crest and the costal margin. A needle was advanced in-plane under real-time ultrasound guidance and directed into the fascial plane between the internal oblique and transversus abdominis muscles bilaterally, as originally described by McDonnell et al.[4] The correct needle tip position within the plane was confirmed sonographically by the appearance of a hypoechoic lens-shaped fluid collection separating the two muscle layers prior to full injection. A volume of 20–30 mL of bupivacaine 0.25% was deposited on each side.

Quadro-Iliac Plane Block

The patient was repositioned to the lateral decubitus position for each side in turn. Using a low-frequency curvilinear ultrasound probe, the iliac crest was identified as the primary bony landmark. The quadratus lumborum muscle was visualized at its attachment to the posterior iliac crest, and the target interfascial plane between the inner aspect of the iliac crest and the posterior surface of the quadratus lumborum muscle was identified. A needle was advanced in-plane under real-time ultrasound guidance toward this target plane, with the iliac crest serving as a bony backstop to prevent excessive needle advancement.[9,10] The correct needle tip position was confirmed sonographically prior to injection. A volume of 20–30 mL of bupivacaine 0.25% was injected on each side.

Outcome measures

The primary outcome was the total postoperative nalbuphine consumption within the first 24 hours following surgery.

Secondary outcomes included: (1) time to first rescue analgesic request; (2) postoperative pain intensity assessed by the Visual Analogue Scale (VAS) at rest, during coughing, and on movement, recorded at 1, 2, 4, 6, 12, and 24 hours postoperatively; (3) postoperative hemodynamic parameters, specifically noninvasive mean arterial blood pressure (MAP) and heart rate (HR), recorded at the same time points; and (4) the incidence of postoperative adverse effects, including nausea, vomiting, pruritus, and respiratory depression.

Statistical analysis

Data analysis was performed using SPSS software, version 26 (SPSS Inc., PASW Statistics for Windows, Version 26.0; Chicago, IL, USA). Qualitative data are presented as frequencies and percentages. Quantitative data were tested for normality using the Kolmogorov–Smirnov test and, where normally distributed, are expressed as mean ± standard deviation (SD). Statistical significance was judged at the 0.05 level for all analyses. The Chi-square test was used to compare qualitative variables between groups where appropriate. The independent samples Student’s t-test was used to compare two independent groups for normally distributed continuous data. The primary outcome (24-hour nalbuphine consumption) was analyzed without adjustment as it represented a single prespecified comparison. All secondary outcomes assessed across multiple time points (VAS scores, MAP, and heart rate, each at six time points) were treated as exploratory, and a Bonferroni correction was applied to control for multiple comparisons, setting the adjusted threshold for statistical significance at α =0.0083 (0.05 ÷ 6) for these analyses.

Artificial Intelligence Assistance: Claude Sonnet 4.6 (Anthropic, San Francisco, CA, USA) was used solely for language editing and grammatical refinement of the manuscript text. All scientific content, study design, data collection, data interpretation, statistical analysis, and conclusions were generated, performed, and verified exclusively by the authors. The use of this tool is disclosed in accordance with recently published guidance on the responsible use of large language models in scientific writing.[13]

Results

Participant flow and baseline characteristics

A total of 40 patients were assessed for eligibility, of whom four were excluded for not meeting the inclusion criteria. The remaining 36 patients were randomized equally into two groups: 18 patients received the TAP block and 18 received the QIPB. There were no losses to follow-up and no discontinuations of the allocated intervention in either group; all 36 enrolled participants were included in the final analysis [Figure 1].

Figure 1.

Consort flow chart showing study design among studied patients

Baseline demographic characteristics were comparable between the two groups. The mean age was 24.44 ± 1.95 years in the TAP group and 24.33 ± 2.47 years in the QIPB group.

Analgesic outcomes

The primary and secondary analgesic outcomes are summarized in Table 1. A statistically significant difference was observed between the two groups with respect to total postoperative nalbuphine consumption within the first 24 hours. Mean nalbuphine consumption was significantly higher in the TAP block group compared with the QIPB group (9.56 ± 2.04 mg vs. 5.28 ± 0.96 mg; P < 0.001; 95% CI: 3.20–5.35), representing a 45% reduction in the QIPB group. This difference is considered clinically significant in the obstetric context, where cumulative opioid exposure during early lactation carries direct implications for neonatal transfer through breast milk, maternal sedation, and the quality of early mother–infant interaction.[11]

Table 1.

Analgesic characters among studied groups

	Transversus abdominis plane block n=18	Quadro-iliac plane block n=18	Test of significance	95% CI
Total postoperative nalbuphine consumption in first 24 hour in mg	9.56±2.04	5.28±0.96	P<0.001*	3.20–5.35
Time to first rescue analgesic request	7.0±1.32	9.78±1.22	P<0.001*	−3.64 to−1.92

CI=Confidence interval. Data expressed as mean±SD, *statistically significant

Similarly, the time to first rescue analgesic request was significantly shorter in the TAP block group than in the QIPB group (7.0 ± 1.32 hours vs. 9.78 ± 1.22 hours; P < 0.001; 95% CI: −3.64 to − 1.92), indicating a prolonged analgesic duration with the QIPB technique.

Postoperative pain scores

Postoperative pain intensity, as assessed by the VAS at multiple time points, is presented in Figure 2. No statistically significant differences were detected between groups at 1, 2, 4, or 24 hours postoperatively (P = 0.641, 0.560, 0.060, and 0.090, respectively). However, statistically significant between-group differences emerged at 6 and 12 hours postoperatively. At 6 hours, mean VAS scores were significantly higher in the TAP block group compared with the QIPB group (5.17 ± 1.54 vs. 3.0 ± 0.84; P < 0.001; 95% CI: 1.32–3.01). At 12 hours, VAS scores remained significantly higher in the TAP block group (6.78 ± 0.65 vs. 6.17 ± 0.62; P = 0.007; 95% CI: 0.18–1.04).

Figure 2.

Postoperative VAS score change among studied groups

Postoperative hemodynamics

Mean arterial pressure

Serial measurements of postoperative mean arterial pressure (MAP) are presented in Table 2. No statistically significant intergroup differences were observed during the first four postoperative hours (P = 0.889, 0.337, and 0.083 at 1, 2, and 4 hours, respectively). From 6 hours onward, MAP values were significantly higher in the TAP block group compared with the QIPB group. At 6 hours, mean MAP was 78.83 ± 4.90 mmHg in the TAP group versus 73.89 ± 5.20 mmHg in the QIPB group (P = 0.006; 95% CI: 1.52–8.37). This pattern was sustained at 12 hours (82.50 ± 4.91 vs. 77.33 ± 5.90 mmHg; P = 0.007; 95% CI: 1.49–8.85) and at 24 hours (86.44 ± 4.69 vs. 79.72 ± 5.56 mmHg; P = 0.001; 95% CI: 3.24–10.21).

Table 2.

Postoperative mean arterial blood pressure changes among studied groups (exploratory outcome)

Postoperative MAP (mmHg)	Transversus abdominis plane block n=18	Quadro-iliac plane block n=18	Raw P	95% CI	Bonferroni correction (P=0.008)
1 h	72.06±5.52	71.78±6.33	P=0.889	−3.75–4.30	NS
2 h	74±5.03	72.28±5.56	P=0.337	−1.87–5.31	NS
4 h	75.67±4.42	72.78±5.25	P=0.083	−0.40–6.18	NS
6 h	78.83±4.90	73.89±5.20	P=0.006*	1.52–8.37	S
12 h	82.50±4.91	77.33±5.90	P=0.007*	1.49–8.85	S
24 h	86.44±4.69	79.72±5.56	P=0.001*	3.24–10.21	S

CI=Confidence interval, NS=Nonsignificant, S=significant. Data expressed as mean±SD, *statistically significant

Heart rate

A parallel pattern was observed for postoperative heart rate, as shown in Table 3. The mean heart rate did not differ significantly between groups at 1, 2, or 4 hours postoperatively (P = 0.669, 0.391, and 0.081, respectively). On raw P values, differences emerged at 6 hours (83.67 ± 5.47 vs. 79.33 ± 4.60 beats/min; P = 0.015; 95% CI: 0.91–7.76), 12 hours (87.06 ± 5.18 vs. 83.44 ± 3.84 beats/min; P = 0.023; 95% CI: 0.52–6.70), and 24 hours (90.28 ± 4.39 vs. 86.11 ± 3.96 beats/min; P = 0.005; 95% CI: 1.33–7.00), with higher values consistently recorded in the TAP block group; however, only the 24-hour difference remained significant after Bonferroni correction.

Table 3.

Postoperative mean heart rate change among studied groups (exploratory outcome)

Postoperative heart rate (b/min)	Transversus abdominis plane block n=18	Quadro-iliac plane block n=18	Test of significance (Raw P)	95% CI	Bonferroni correction (P=0.008)
1 h	76.89±7.01	76.06±4.26	P=0.669	−3.10–4.76	NS
2 h	78.39±6.07	76.83±4.55	P=0.391	−2.08–5.19	NS
4 h	80.72±5.75	77.61±4.54	P=0.081	−0.40–6.62	NS
6 h	83.67±5.47	79.33±4.60	P=0.015*	0.91–7.76	NS
12 h	87.06±5.18	83.44±3.84	P=0.023*	0.52–6.70	NS
24 h	90.28±4.39	86.11±3.96	P=0.005*	1.33–7.00	S

CI=Confidence interval, NS=Nonsignificant, S=significant. Data expressed as mean±SD, *statistically significant

Adverse effects

The incidence of postoperative adverse effects was comparable between groups, with no statistically significant differences detected for any of the monitored complications [Table 4]. Neither group experienced nausea or respiratory depression throughout the 24-hour observation period. Vomiting was reported in four patients (22.2%) in the TAP block group and three patients (16.7%) in the QIPB group; given that expected cell frequencies fall below five with n = 18 per group, Fisher’s exact test was applied, yielding no statistically significant difference between groups (P = 1.000). Pruritus was recorded in one patient (5.6%) in each group (Fisher’s exact test; P = 1.000).

Table 4.

Side effects among studied groups (exploratory outcome)

	Transversus abdominis plane block n=18	Quadro-iliac plane block n=18	Test of significance
Nausea	0	0	……
Vomiting	4 (22.2)	3 (16.7)	FET; P=1.000
Pruritis	1 (5.6)	1 (5.6)	FET; P=1.000
Respiratory depression	0	0	…….

FET=Fisher exact test. ꭓ²=Chi-Square test, data expressed as number (%)

Overall, both techniques demonstrated a comparable and acceptable safety profile with respect to postoperative adverse events. Repositioning to the lateral decubitus position for the QIPB was well tolerated; no patient experienced hemodynamic instability or discomfort attributable to the position change, and all repositioning was performed under continuous hemodynamic monitoring and direct anesthesiologist supervision.

Discussion

Overview of main findings

In this small randomized study of 36 ASA I–II parturients undergoing elective cesarean delivery under spinal anesthesia without intrathecal opioid, the QIPB was associated with lower 24-hour nalbuphine consumption than the TAP block (5.28 vs. 9.56 mg; P < 0.001), a 45% reduction, and with a longer time to first rescue analgesia (mean difference 2.78 hours; 95% CI: 1.92–3.64; P < 0.001). VAS scores favored the QIPB at the 6- and 12-hour assessments, the interval in which the spinal anesthetic has worn off and the fascial plane block carries the analgesic load. Age was similar between groups (24.44 ± 1.95 vs. 24.33 ± 2.47 years); other patient-level variables were not formally compared, so residual confounding cannot be excluded, although the consistent direction of effect across endpoints makes unmeasured imbalance an unlikely sole explanation. No clinically relevant hemodynamic differences were observed between groups. Adverse events occurred at similar rates in both arms.

Lower opioid exposure is relevant in the obstetric setting because sedation, nausea, vomiting, pruritus, and breast-milk transfer of opioid all track with cumulative dose and can affect maternal vigilance, breastfeeding, and early mother–infant interaction during the first postoperative day.[1,2,8] A pharmacokinetic review confirms that maternally administered opioids transfer into breast milk in proportion to maternal dose and drug clearance, reinforcing the value of minimizing maternal opioid load during early lactation.[14]

Mechanistic rationale and opioid-sparing effect

A plausible explanation for the analgesic difference lies in what each block reaches. Post-cesarean pain has a somatic component from the abdominal wall incision and a visceral component from uterine manipulation and peritoneal handling.[3] The TAP block reaches only the T7–L1 somatic afferents within the anterolateral abdominal wall.[4] The QIPB is deposited adjacent to the quadratus lumborum, where local anesthetic is thought to spread along the thoracolumbar fascia toward the lower thoracic paravertebral space,[10] a route supported by cadaveric injectate-mapping work[15] but of acknowledged variability.[16] A block addressing both somatic and visceral input would be expected to produce less breakthrough pain, and therefore less rescue opioid demand, than one addressing somatic input alone.

This direction is consistent with the published literature. Blanco et al.,[17] in the seminal head-to-head trial of 76 parturients, found significantly lower cumulative morphine consumption with the quadratus lumborum block (QLB) than the TAP block at 12, 24, and 48 hours, with similar VAS scores between groups. Borys et al.,[12] whose data informed our sample size calculation, reported the same pattern: their TAP block patients required significantly more supplemental morphine (P = 0.039) despite comparable VAS scores. The meta-analysis by Ferguson et al.[18] pooled six trials and 543 parturients and confirmed an opioid-sparing advantage of QL-type blocks over the TAP block, with lower 24-hour pain scores at rest (mean difference − 0.60; 95% CI: −1.03 to − 0.17) and on activity (−1.05; 95% CI: −1.54 to − 0.56). Zhao et al.,[11] using a control comparator, confirmed the opioid-sparing effect of the QLB to be robust on trial-sequential analysis.

Several caveats apply to the magnitude of our effect, which sits at the higher end of published estimates. Nalbuphine, a mixed κ-agonist/μ-antagonist, is not pharmacologically equivalent to morphine, so milligram comparisons with morphine-based trials are approximate.[19] The spinal protocol did not include intrathecal morphine, placing the comparison in the setting where the fascial plane block carries the analgesic burden; a systematic review found that the TAP block adds analgesic benefits when intrathecal opioid is absent but not when it is present.[20] Finally, the enrolled patients were young, healthy, and free of comorbid pain conditions, which may have allowed a clearer intergroup signal than would be seen in higher-risk parturients.

Duration of analgesia and pain scores

The longer time to first rescue with the QIPB likely reflects two features: deposition within a relatively avascular interfascial plane bounded by the iliac crest, which may slow absorption and contain the injectate,[10] in contrast to the more vascularized TAP compartment with variable cephalad spread[21], and coverage of a visceral pathway the TAP block cannot reach. Single-shot TAP block analgesia after cesarean delivery is generally confined to the early postoperative hours.[22,23] Because the spinal protocol was identical in both groups, the 2.78-hour intergroup difference reflects the differential between the two blocks rather than the absolute duration of either.

The VAS trajectory mirrored the opioid data. Scores were low and similar in both groups during the first four hours, reflecting residual spinal blockade, then diverged significantly at 6 hours (P < 0.001) and remained separated at 12 hours (P = 0.007), the window in which the fascial plane block is the only active regional analgesic. Blanco et al.[17] noted the same early equivalence attributable to spinal anesthesia. By 24 hours, the difference was no longer significant (P = 0.090), partly because single-shot bupivacaine analgesia wanes by this point and partly because TAP patients had received more rescue nalbuphine, which compresses the apparent VAS difference. Because VAS was compared across six time points, a Bonferroni correction was applied (adjusted α = 0.0083); both significant time points survived. The VAS is unidimensional and cannot separate somatic from visceral pain, so these data cannot directly confirm the proposed visceral advantage of the QIPB.[24]

Hemodynamic findings

MAP and HR were similar between groups during the first four hours, consistent with residual spinal blockade. From 6 hours onward, MAP differences at 6, 12, and 24 hours survived Bonferroni correction, whereas only the 24-hour heart rate difference survived; the 6- and 12-hour heart rate differences should be regarded as exploratory. Although MAP and heart rate remained statistically different at 24 hours, the absolute differences (6.72 mmHg and 4.17 beats/minute) are small, both groups remained within the normal physiological range, and these differences are not clinically meaningful in this healthy ASA I–II population. Postoperative MAP and HR are also influenced by fluid administration, oxytocin, uterine massage, nursing stimulation, and anxiety, none of which were controlled. These findings should therefore be regarded as hypothesis-generating rather than evidence of a clinically important hemodynamic benefit.

Safety

Both techniques showed a comparable and acceptable safety profile. Neither group experienced nausea or respiratory depression. Vomiting (22.2% vs. 16.7%) and pruritus (5.6% in each group) did not differ significantly (Fisher’s exact test; P = 1.000). The absence of a statistically lower vomiting rate in the QIPB group despite lower opioid consumption likely reflects the low absolute event rate and limited sample size. No local anesthetic systemic toxicity, block-site hematoma, or visceral injury occurred. Real-time ultrasound guidance was used throughout, and the iliac crest provides a bony backstop for the QIPB[10]; nonetheless, vigilance for local anesthetic systemic toxicity remains mandatory with bilateral fascial plane blocks.

Comparison with existing literature

To our knowledge, this is the first prospective randomized head-to-head comparison of the QIPB and TAP block in the obstetric population. The QIPB remains a novel technique; the systematic review by Shakeri and Alinejadfard[10] identified only two RCTs and 17 observational studies totaling 164 patients, none comparing it with the TAP block in obstetric patients. Our findings are directionally consistent with the broader QL-type block literature,[12,17,18] in which posterior fascial plane blocks targeting anatomy proximal to the quadratus lumborum provide superior analgesia to the TAP block. Borys et al.,[25] in a three-arm trial, additionally observed lower persistent pain scores in the QLB group at 1 and 6 months, although the QLB and TAP groups were not directly compared for that outcome.

Strengths and limitations

Strengths include the prospective randomized design, single-operator block administration ensuring technical consistency, blinded outcome assessment, and standardized anesthetic and rescue protocols. The principal limitation is the small sample size, which constrains the precision of secondary endpoint estimates and limits power to detect differences in infrequent outcomes. The single-center design limits generalizability. All patients received spinal anesthesia without intrathecal morphine; whether the QIPB confers incremental benefits when intrathecal morphine is used is unknown, and these results should not be extrapolated to that context.[20] The 24-hour observation window precludes assessment of chronic postsurgical pain, which is relevant given evidence that higher acute pain predicts persistent pain after cesarean delivery.[26] Finally, dermatomal sensory mapping was not performed, and VAS was recorded as a single composite score rather than disaggregated into rest, movement, and coughing components, limiting mechanistic inference.

Clinical implications and future directions

Within the constraints of a small single-center trial, the QIPB was associated with reduced opioid consumption and prolonged analgesia compared with the TAP block, supporting its further evaluation as a component of multimodal Enhanced Recovery After Cesarean pathways, particularly where intrathecal opioid is not used.[27] Whether superior acute analgesia translates into a reduction in chronic postsurgical pain remains an open question.[26] Larger multicenter trials with extended follow-up, dermatomal mapping, disaggregated dynamic pain scores, and comparison against intrathecal morphine and other fascial plane techniques are needed before the role of the QIPB in routine practice can be established.

Conclusion

In this small randomized controlled trial, the ultrasound-guided QIPB was associated with greater opioid-sparing efficacy compared with the TAP block in parturients undergoing elective cesarean delivery under spinal anesthesia. The QIPB reduced 24-hour nalbuphine consumption by 45%, prolonged the time to first rescue analgesic request by nearly 3 hours, and produced significantly lower pain scores at the 6- and 12-hour assessments—the window in which fascial plane block analgesia bears the greatest clinical weight following spinal offset. No clinically relevant hemodynamic differences were observed between groups, and adverse event profiles were comparable. Within the limitations of a small single-center trial, these findings support the QIPB as a promising opioid-sparing technique that merits further evaluation as a component of multimodal ERAC protocols, particularly where intrathecal opioid is not used. Larger multicenter trials with extended follow-up and assessment of chronic postsurgical pain are needed before its role in routine practice can be established.

Conflicts of interest

There are no conflicts of interest to declare.

Funding Statement

Nil.