Ultrasound-guided rectus sheath block: an anatomic study in dog cadavers

Description and Evaluation of Dye and Contrast Media Distribution of Ultrasound-Guided Rectus Sheath Block in Cat Cadavers

The rectus sheath block is an ultrasound-guided anaesthetic technique which aims to provide analgesia to the abdominal midline. This study aimed to assess the distribution of 0.4 mL kg-1 of a mixture of methylene blue and iopromide injected into each hemiabdomen in the internal rectus sheath in cat cadavers. We hypothesise that this technique would be feasible and would cover the rami ventrales of the last thoracic and the first lumbar spinal nerves. The study was divided into two phases. Phase 1 aimed to study the anatomical structures of the ventral abdominal wall (four cats were dissected). Phase 2 (ten cadavers) consisted of an ultrasound-guided injection of the mixture mentioned above and the assessment of its distribution by computed tomography and anatomical dissection. The results showed the staining of the cranioventral abdominal wall with a craniocaudal spread of four (three to eight) vertebral bodies. Methylene blue stained three (one to four) rami ventrales, affecting T10 (60%), T11 (100%), T12 (90%), T13 (50%) and L1 (5%). Based on these results, it could be stated that this technique could supply anaesthesia to the midline of the abdominal midline cranial to the umbilicus in clinical patients, but it may not be able to provide anaesthesia to the middle and caudal midline abdominal region.

Postsurgical Analgesic Effectiveness of Ultrasound-Guided Parasternal Block After Auricular Reconstruction Using Autologous Costal Cartilage in Pediatric Patients: A Randomized Controlled Trial

OBJECTIVE

To study the efficacy of ultrasound-guided parasternal block (US-PSI) in pediatric patients undergoing auricular reconstruction surgery.

METHODS

For this study, the authors recruited 60 children between the ages of 5 and 12 years who underwent auricular reconstruction with autologous costal cartilage (ACC) to correct microtia. They were randomized to receive either ultrasound-guided modified parasternal block or periprostatic local infiltration anesthesia (PLIA), with 30 cases in each group. Ultrasound-guided parasternal block was administered following anesthesia induction, whereas PLIA was administered after ACC harvest. Lastly, following surgery, all children were provided with patient-controlled intravenous analgesia with sufentanil, and the numeric pain rating scale (NRS) was used to assess the intensity of pain. Our primary outcomes were the resting NRS pain scores and the NRS scores upon coughing at 1, 6, 12, 24, and 48 hours postsurgery. Sufentanil consumption within the first 24 hours of surgery, the mean duration to first ambulation, and the usage of rescue analgesics were our secondary outcomes. The authors also recorded the occurrence of undesirable side effects as well as more serious side effects like pneumothorax.

RESULTS

Pediatric patients who were administered US-PSI showed significantly reduced NRS chest pain scores at 6 and 12 hours postsurgery compared to those who received PLIA (P<0.05). In addition, sufentanil consumption within the first 24 hours postsurgery, duration to first ambulation, and use of rescue analgesics were significantly lower among patients in the US-PSI group when compared to those in the PLIA group (P<0.05).

CONCLUSIONS

This study found that US-PSI was a highly efficacious and safe technique for postsurgical analgesia following auricular reconstruction with ACC in pediatric patients.

LEVEL OF EVIDENCE

Level II, therapeutic study.

The Spread Distance of Local Anesthetics in the Rectus Sheath Block in Children Aged 0-8 Years: A Retrospective Study

Background The spread distance of local anesthetic (LA) in the rectus sheath block (RSB) should cover the planned surgical incision. However, there is limited data regarding the spread distance that can be covered by a certain volume in children. In this study, we aimed to investigate the spread distance of a particular volume of LA from a single injection point. Methodology This study included children aged 0-8 years (n = 41) who underwent umbilical or epigastric hernia repair, laparoscopic surgery, and surgeries via small midline incisions. The spread distances, which were measured via ultrasound guidance immediately after the block to ensure coverage of the entire planned surgical incision, were obtained from prospectively collected data about RSB. The spread distances in the craniocaudal direction on the right and left sides were compared and assessed for correlations with age, weight, LA volume, and sex. The need for a supplemental dose of LA in case of an incision exceeding the spread distance was also obtained from the records. Results The spread distances in the cranial and caudal directions from the injection point were 3.28 ± 1.04 cm and 3.74 ± 1.35 cm on the right (p = 0.066) and 3.44 ± 1.02 cm and 3.44 ± 1.33 cm on the left (p > 0.999), respectively. The total spread distances in the craniocaudal direction on the right and left were 5.55 ± 0.95 cm and 5.72 ± 1.28 cm in patients aged 0-2 years and 7.25 ± 1.92 cm and 7.39 ± 1.81 cm in patients aged at 2-8 years, respectively. The increase in the spread distance correlated with age, weight, and LA volume. None of the patients required a supplemental dose of LA, as the single-point injections covered the planned surgical incisions in all patients. Conclusions Similar spread distances in the cranial and caudal directions from a single injection point can be obtained with 0.5 mL/kg of the LA in 0-8-year-old children. The total spread distance in the craniocaudal direction was approximately 5 cm and 7 cm in children aged 0-2 years and 2-8 years, respectively.

Antinociceptive effects of bupivacaine injected within the internal abdominis rectus sheath in standing healthy horses

OBJECTIVE

To evaluate a regional anesthetic technique for blocking the abdominal midline in horses.

STUDY DESIGN

Anatomical description and prospective, crossover, placebo-controlled, blinded study.

ANIMALS

Adult horses; two cadavers, six healthy animals.

METHODS

In stage 1, 0.5% methylene blue with 0.25% bupivacaine (0.5 mL kg-1) was injected using ultrasonography into the internal rectus abdominis sheath (RAS) of two cadavers with a one-point or two-point technique. The dye spread was described after the dissection of the abdomens. In stage 2, each horse was injected with 1 mL kg-1 of 0.9% NaCl (treatment PT) or 0.2% bupivacaine (treatment BT) using a two-point technique. The abdominal midline mechanical nociceptive threshold (MNT) was measured with a 1 mm blunted probe tip and results analyzed with mixed-effect anova. Signs of pelvic limb weakness were recorded.

RESULTS

The cadaver dissections showed staining of the ventral branches from the eleventh thoracic (T11) to the second lumbar (L2) nerve with the one-point technique and T9-L2 with the two-point technique. Baseline MNTs were, mean ± standard deviation, 12.6 ± 1.6 N and 12.4 ± 2.4 N in treatments PT and BT, respectively. MNT increased to 18.9 ± 5.8 N (p = 0.010) at 30 minutes, and MNT was between 9.4 ± 2.0 and 15.3 ± 3.4 N from 1 to 8 hours (p > 0.521) in treatment PT. MNTs in treatment BT were 21.1 ± 5.9 to 25.0 ± 0.1 N from 30 minutes to 8 hours (p < 0.001). MNTs after the RAS injections were higher in treatment BT than PT (p = 0.007). No pelvic limb weakness was observed.

CONCLUSIONS AND CLINICAL RELEVANCE

Antinociception of at least 8 hours without pelvic limb weakness was observed in the abdominal midline in standing horses after the RAS block. Further investigations are necessary to evaluate suitability for ventral celiotomies.

Clinical efficacy of an ultrasound-guided bilateral rectus sheath block for umbilical hernia repair in calves: A prospective randomized trial

Introduction

Surgical umbilical hernia repair is a frequent procedure in newborn calves, requiring mandatory pain management. This study aimed to develop an ultrasound-guided rectus sheath block (RSB) and to evaluate its clinical efficacy in calves undergoing umbilical herniorrhaphy under general field anesthesia.

Methods

Gross and ultrasound anatomy of the ventral abdomen and the diffusion of a new methylene blue solution after injection within the rectus sheath were described in seven fresh calf cadavers. Then, fourteen calves undergoing elective herniorrhaphy were randomly assigned to receive either bilateral ultrasound-guided RSB with 0.3 mL/kg of bupivacaine 0.25% and 0.15 µg/kg of dexmedetomidine or 0.3 mL/kg of 0.9% NaCl (control). Intraoperative data included cardiopulmonary variables and anesthetic requirements. Postoperative data included pain scores, sedation scores and peri-incisional mechanical threshold assessed by force algometry at specific time points after anesthetic recovery. Treatments were compared using Wilcoxon rank-sum, Student's t-test, and Cox proportional hazard model as appropriate. Mixed effect linear models on rank, with random effect calf; fixed effects time, treatment, and their interaction were used to compare pain scores and mechanical thresholds over time. Significance was set at p = 0.05.

Results and Discussion

Calves receiving RSB recorded lower pain scores between 45 - 120 minutes (p < 0.05) and at 240 min after recovery (p = 0.02). And they recorded higher mechanical thresholds between 45 and 120 min after surgery (p < 0.05). Ultrasound-guided RSB provided effective perioperative analgesia in calves undergoing herniorrhaphy under field conditions.

Analgesic efficacy of an ultrasound-guided transversus abdominis plane block with bupivacaine in cats: a randomised, prospective, masked, placebo-controlled clinical trial

OBJECTIVES

This randomised, prospective, masked clinical trial evaluated the postoperative analgesic efficacy of an ultrasound-guided transversus abdominis plane block (TAPB) with bupivacaine in cats undergoing ovariohysterectomy.

METHODS

Thirty-two healthy adult female cats undergoing elective ovariohysterectomy were randomised to undergo TAPB with bupivacaine (treatment group [TG], n = 16) vs placebo (control group [CG], n = 16) in addition to preoperative analgesia with buprenorphine (0.02 mg/kg IM). All patients received a general anaesthetic and, before surgical incision, a bilateral two-point (subcostal and lateral-longitudinal) TAPB was performed using 1 ml/kg bupivacaine 0.25% (0.25 ml/kg/point) or saline. Each cat was assessed by a blinded investigator before premedication (0 h) and at 1, 2, 3, 4, 8, 10 and 24 h postoperatively using the UNESP-Botucatu Feline Pain Scale - short form. Buprenorphine (0.02 mg/kg IV) and meloxicam (0.2 mg/kg SC) were administered when pain scores were ⩾4/12. Ten hours postoperatively, meloxicam was administered to cats that did not receive rescue analgesia. Statistical analysis included Student's t-tests, Wilcoxon tests and χ2 tests, and a linear mixed model with Bonferroni corrections (P <0.05).

RESULTS

Of the 32 cats enrolled, three in the CG were excluded from the analysis. The prevalence of rescue analgesia was significantly higher in the CG (n = 13/13) than in the TG (n = 3/16; P <0.001). Only one cat in the CG required rescue analgesia twice. Pain scores were significantly higher in the CG compared with the TG at 2, 4 and 8 h postoperatively. Mean ± SD pain scores were significantly higher in the CG, but not in the TG, at 2 (2.1 ± 1.9), 3 (1.9 ± 1.6), 4 (3.0 ± 1.4) and 8 h postoperatively (4.7 ± 0.6) than at 0 h (0.1 ± 0.3).

CONCLUSIONS AND RELEVANCE

A bilateral ultrasound-guided two-point TAPB with bupivacaine in combination with systemic buprenorphine provided superior postoperative analgesia than buprenorphine alone in cats undergoing ovariohysterectomy.

Evaluating Patterns of Injectate Spread After Rectus Sheath Block: A Cadaveric Dissection Study

INTRODUCTION

This cadaveric dye study assesses the effect of volume and number of injections on the spread of solution after ultrasound-guided rectus sheath injections. In addition, this study evaluates the impact of the arcuate line on solution spread.

MATERIALS AND METHODS

Ultrasound-guided rectus sheath injections were performed on seven cadavers on both sides of the abdomen, for a total of 14 injections. Three cadavers received one injection of 30 mL of a solution consisting of bupivacaine and methylene blue at the level of the umbilicus. Four cadavers received two injections of 15 mL of the same solution, one midway between the xiphoid process and umbilicus and one midway between the umbilicus and pubis.

RESULTS

Six cadavers were successfully dissected and analyzed for a total of 12 injections, while one cadaver was excluded due to poor tissue quality that was inadequate for dissection and analysis. There was a significant spread of solution with all injections caudally to the pubis without limitation by the arcuate line. However, a single 30 mL injection showed inconsistent spread to the subcostal margin in four of six injections, including in a cadaver with an ostomy. A double injection of 15 mL showed consistent spread from xiphoid to pubis in five of six injections, except in a cadaver with a hernia.

CONCLUSIONS

Injections deep to the rectus abdominis muscle, using the same technique as an ultrasound-guided rectus sheath block, achieve spread along a large and continuous fascial plane without limitation by the arcuate line and may provide coverage of the entire anterior abdomen. A large volume is necessary for complete coverage and spread is improved with multiple injections. We suggest that two injections with a total volume of at least 30 mL per side may be needed to achieve adequate coverage in the absence of preexisting abdominal abnormalities.

Description of an ultrasound-guided rectus sheath block injection technique and the spread of dye in calf cadavers

OBJECTIVES

To describe an ultrasound-guided rectus sheath (RS) block technique in calves with injections of methylene blue and assess the extent of injectate spread and nerve staining in calf cadavers.

STUDY DESIGN

Prospective, experimental, blinded cadaveric study.

ANIMALS

A total of 16 calf cadavers weighing 30.7 ± 7.1 kg.

METHODS

Using an ultrasound-guided, in-plane technique, each cadaver was injected with both a low (LV; 0.25 mL kg-1) and high (HV; 0.5 mL kg-1) volume of methylene blue dye. Volumes were randomly assigned to the left or right hemiabdomen. Ultrasound imaging was scored based on landmarks and needle visualization, and duration to perform injections were assessed. Dissections were performed immediately after injections. Staining of ventral branches of spinal nerves and the extent of dye spread were recorded by an anatomist unaware of treatment allocation.

RESULTS

The number of nerves stained in treatments LV and HV were 2.3 ± 1.7 and 4.4 ± 1.3, respectively (p = 0.0001). Branches of thoracic nerves T7-13 and lumbar nerves L1-2 were completely stained 6.3%, 6.3%, 31.3%, 62.5%, 56.3%, 37.5%, 31.3%, 6.3% and 0%, respectively, in treatment LV and 0%, 12.5%, 50%, 93.8%, 100%, 93.8%, 62.5%, 25% and 6.3%, respectively, in treatment HV. Ultrasound imaging was scored excellent in most cadavers and needle visualization deemed excellent in all injections. The mean duration to perform RS injections in both treatments was 2 (range, 1-6) minutes.

CONCLUSIONS AND CLINICAL RELEVANCE

Nerve staining results from treatment HV suggest that this RS injection technique could be clinically useful in ventral midline surgical procedures, including umbilical procedures, in calves. This study supports future clinical trials in calves.

Open approach to the ventral transversus abdominis plane in the dog: evaluation and injectate dispersion in cadavers

OBJECTIVE

To evaluate a direct intra-abdominal approach to injection of the ventral transversus abdominis plane (TAP) and compare the dispersion of two volumes of injectate.

STUDY DESIGN

Prospective anatomic and feasibility study.

ANIMALS

A total of 10 canine cadavers weighing 9 ± 4 kg.

METHODS

A ventral incision was made extending through the linea alba, from the umbilicus and extending 5 cm caudally. A single injection of an isovolumic mixture of iopamidol and new methylene blue was performed with a hypodermic needle placed within the TAP of each hemiabdomen, alternating between 0.5 mL kg^-1 in low-volume group (LV) and 1 mL kg^-1 in high-volume group (HV). Surgical staples marked the incision. Computed tomography and three-dimensional reconstruction of the tomographic images evaluated the dimensions, cranial and caudal spread beyond the incision and the total area of the injectate. Dissection determined the extent of nerve staining within the TAP adjacent to the abdominal incision. Wilcoxon signed rank (stain) or paired t test was used to compare variables between groups. Data are reported as mean ± standard deviation or median (range).

RESULTS

Injectate spread was within the ventral TAP. Length of spread was 2.5 ± 1.6 cm greater in group HV than in group LV. There was a strong positive correlation between the surface area (p = 0.02, r = 0.71) and cranial-caudal spread of injectate (p = 0.041, r = 0.65) with volume. All but two LV injections were associated with staining of all nerves adjacent to the incision. Additional nerves caudal to the incision were stained in group HV (p = 0.02).

CONCLUSIONS

This approach to the TAP was easily performed, with volume of injectate positively influencing distribution.

CLINICAL RELEVANCE

This technique is easily applied and future prospective studies are warranted to determine its analgesic efficacy.