Minimum Local Anesthetic Dose of Ropivacaine in Cesarean Section for Real-Time Ultrasound-Guided Spinal Anesthesia Using 24-Gauge versus 26-Gauge Needles Based on Fluid Simulation Technology: A Randomized Controlled Trial

Purpose

Previous research has demonstrated that real-time ultrasound-guided (UG) spinal anesthesia requires a higher minimum local anesthetic dose (MLAD) compared to traditional methods. However, the precise MLAD of ropivacaine for UG cesarean sections remains undetermined. In this study, we ascertained the MLAD of ropivacaine for cesarean section. We also investigated the mechanism underlying the diffusion of ropivacaine within the spinal canal using fluid simulation technology.

Patients and Methods

We randomly placed 60 healthy parturients undergoing elective cesarean section with real-time UG spinal anesthesia into Groups I (26-gauge spinal needle) and II (24-gauge spinal needle). For the first parturient in both groups, 15 mg of ropivacaine was administered intrathecally. Based on the effective or ineffective response of the previous parturient, the dose for the subsequent parturient was increased or decreased by 1 mg. Spinal anesthesia characteristics and side effects were recorded. A computer-generated spinal canal model was developed. Leveraging fluid dynamics simulation technology, we documented the diffusion of ropivacaine in the spinal canal using 26-and 24-gauge spinal needles.

Results

The MLADs in Groups I and II were 12.728 mg (12.339-13.130 mg) and 9.795 mg (9.491-10.110 mg), respectively. No significant difference was observed in the onset times and durations of sensory or motor blocks, incidence of complications, or neonatal Apgar scores between both groups. Fluid simulation modeling indicated that the 26-gauge spinal needle achieved a higher distribution level more quickly; however, its peak drug concentration was lower compared to the 24-gauge spinal needle.

Conclusion

For cesarean section anesthetization, the required MLAD of ropivacaine when using a real-time UG 26-gauge spinal needle is significantly greater than that with a 24-gauge needle. The spinal needle diameter influences ropivacaine's MLAD by markedly affecting its diffusion rate within the spinal canal.

Performance of the ratio of posterior complex length to depth measured by ultrasound as a predictor of difficult spinal anesthesia for elective cesarean delivery: a prospective cohort study

PURPOSE

Ultrasound view of the interlaminar structure is likely to be associated with difficult spinal anesthesia (DSA), and a poor ultrasound view which cannot show the anterior and posterior complex predicts a difficult spinal technique. As our target site is the posterior complex, this study aimed to assess whether the ratio of posterior complex length to depth measured by ultrasound can predict DSA in cesarean delivery.

METHODS

Four anesthesiologists with 1-2 years of experience located and marked the puncture interspace using a traditional surface landmark. Subsequently, the ultrasound examiner located and measured the marked interspace via an oblique parasagittal ultrasound scan. The anesthesiologists, who were blinded to the ultrasound results, performed spinal anesthesia using a 25-gauge Whitacre spinal needle. The total number of attempts, including skin punctures and needle passes, was recorded and the DSA was defined as 10 unsuccessful attempts. A multivariable logistic regression analysis was used to determine the independent predictors, and receiver operating characteristic curves were constructed to evaluate the performance of the ratio of posterior complex length to depth for predicting DSA.

RESULTS

A total of 397 cesarean delivery parturients with successfully measured posterior complex were included in the analysis. DSA occurred in 64 parturients (16.1%). Reduced length [odds ratio (OR) = 0.010, 95% confidence interval (CI), 0.002-0.062, P < 0.001] and increased depth [OR = 6.127, 95% CI, 2.671-14.056, P < 0.001] of the posterior complex were independently predictive of DSA compared with body mass index, abdominal circumference, and palpable surface landmarks. The ratio of posterior complex length to depth for predicting DSA had an area under the curve of 0.86 (95% CI, 0.82-0.90). The optimal cutoff was 0.23, with a sensitivity of 86% (95% CI, 74-93%) and specificity of 72% (95% CI, 67-77%).

CONCLUSION

The ratio of posterior complex length to depth measured by ultrasound demonstrated a considerable accuracy in predicting DSA for inexperienced anesthesiologists. A higher ratio at ultrasound is an indication to evaluate the optimal puncture body position and interspace in the clinic practice.

CLINICAL TRIAL REGISTRATION

ChiCTR2200065171 https://www.chictr.org.cn/showproj.html?proj=180855.

Point-of-Care Ultrasound: A Vital Tool for Anesthesiologists in the Perioperative and Critical Care Settings

Point-of-care ultrasound (POCUS) is an essential skill in various specialties like anesthesiology, critical care, and emergency medicine. Anesthesiologists utilize POCUS for quick diagnosis and procedural guidance in perioperative and critical care settings. Key applications include vascular ultrasound for challenging venous and arterial catheter placements, gastric ultrasound for aspiration risk assessment, airway ultrasound, diaphragm ultrasound, and lung ultrasound for respiratory assessment. Additional utilities of POCUS can include multi-organ POCUS evaluation for undifferentiated shock or cardiac arrest, ultrasound-guided central neuraxial and peripheral nerve blocks, focused cardiac ultrasound, and novel applications such as venous excess ultrasound. This review highlights these POCUS applications in perioperative and intensive care and summarizes the latest evidence of their accuracy and limitations.

Comparative efficacy of ultrasound guidance or conventional anatomical landmarks for neuraxial puncture in adult patients: a systematic review and network meta-analysis

BACKGROUND

Preprocedural, real-time, and computer-aided three-dimensional ultrasound has been widely used for neuraxial puncture; however, the optimal guidance is unclear. We examined the comparative efficacy of three ultrasound guidance and anatomical landmarks for neuraxial puncture in adults.

METHODS

We searched for randomised controlled studies comparing the efficacy of ultrasound guidance and anatomical landmarks for neuraxial puncture in adults using electronic databases and unpublished studies. The primary outcomes were first-pass success and patient satisfaction. A random-effects network meta-analysis (NMA) was used.

RESULTS

We identified 74 eligible studies (7090 patients). Preprocedural ultrasound and real-time ultrasound-guided neuraxial puncture improved first-pass success compared with anatomical landmarks (risk ratio [RR] 1.6; 95% credible interval [CrI] 1.3-1.9; RR 1.9; 95% CrI 1.3-2.9, respectively, moderate confidence). Computer-aided ultrasound-guided neuraxial puncture also increased first-pass success (RR 1.8; 95% CrI 0.97-3.3, low confidence), although estimates were imprecise. However, real-time ultrasound-guided neuraxial puncture resulted in minimal difference in first-pass success compared with preprocedural ultrasound (RR 1.2; 95% CrI 0.8-1.8, moderate confidence). Preprocedural ultrasound improved patient satisfaction slightly compared with anatomical landmark use (standardised mean differences 0.28; 95% CrI 0.092-0.47, low confidence).

CONCLUSIONS

This NMA provides evidence supporting ultrasound-guided neuraxial puncture compared with use of anatomical landmarks, including indirect comparisons. Among the three ultrasound guidance methods, preprocedural ultrasound appears to be a better adjunctive option.

Comparison of ultrasound-guided and traditional localisation in intraspinal anesthesia: a systematic review and network meta-analysis

OBJECTIVES

The optimal puncture technique for neuraxial anaesthesia in different populations is unclear. We sought to obtain data from randomised controlled trials comparing the impact of ultrasound-guided technology and traditional positioning technology on the success rate of neuraxial anaesthesia.

DESIGN

Systematic review and network meta-analysis using study populations, interventions, intervention comparisons, outcome measures and study types.

DATA SOURCES

PubMed, Embase, Cochrane Library and Web of science were searched until 31 September 2022.

ELIGIBILITY CRITERIA

We included randomised controlled trials comparing three types of neuraxial anaesthesia: ultrasound-assisted, ultrasound real-time guidance and conventional positioning to describe which neuraxial anaesthesia modality is best for patients and to recommend the appropriate one for different populations.

DATA EXTRACTION AND SYNTHESIS

Five independent reviewers retrieved, screened and edited included studies using standardised methods. Assess risk of bias using the Cochrane Collaboration and Evidence Project tools. Network meta-analysis was performed using STATA V.15 statistical software.

RESULTS

Twenty-two studies containing three different interventions were included. The SUCRA values of first-pass success rates for the three neuraxial anaesthesia methods were real-time guidance (82.8%), ultrasound-assisted (67.1%) and traditional positioning (0.1%). Both ultrasound techniques improved first-pass success rates compared with traditional localization, but there was no significant difference between the two. Subgroup analysis showed that the use of real-time ultrasound guidance for neuraxial anaesthesia in pregnant and patients with obesity improved first-pass success rates. Ultrasound-assisted technology can improve first-attempt success rates in older patients with abnormal lumbar spine anatomy.

CONCLUSION

Compared with conventional positioning, ultrasound guidance technology can improve the first-pass success rate of neuraxial anaesthesia, but there is no significant difference between ultrasound-assisted and real-time guidance technology. The results of subgroup analysis tell us that the most suitable neuraxial anaesthesia method is different for different groups of people.

PROSPERO REGISTRATION NUMBER

PROSPERO number: CRD42022376041.

Spinal sonography and central neuraxial blocks

Central neuraxial blocks (CNBs), which include spinal, epidural, and combined spinal epidural injections, are indispensable techniques in the anesthesiologist's armamentarium. Indeed, in scenarios such as when dealing with the obstetric population, patients with obesity, or patients having respiratory compromise (e.g., lung disease or scoliosis), CNBs are the mainstay for anesthesia and/or analgesia. Traditionally, CNBs are performed using anatomical landmarks, which are simple, easy to master, and exceptionally successful in most cases. Nevertheless, there are notable limitations with this approach, especially in scenarios where CNBs are considered mandatory and vital. Any limitation of an anatomic landmark-based approach is an opportunity for an ultrasound-guided (USG) technique. This has become particularly true for CNBs, where recent advances in ultrasound technology and research data have addressed many of the shortcomings of the traditional anatomic landmark-based approaches. This article reviews the ultrasound imaging of the lumbosacral spine and its application for CNBs.

Evaluation of Lumbar Sonography as a Learning Aid for Performing Subarachnoid Block Using the Paramedian Approach by Medical Junior Resident Anaesthesiologists: A Randomized Controlled Trial

BACKGROUND

Pre-procedural ultrasound can be used to identify the subarachnoid space in difficult spinal procedures. However, multiple punctures can result in numerous complications, including post-dural puncture headache, neural trauma, and spinal and epidural haematoma. Thus, the following hypothesis was proposed: in contrast to the conventional blind paramedian dural puncture, pre-procedural ultrasound results in a successful dural puncture on the first attempt.

METHODS

In this prospective, randomised controlled study, 150 consenting patients were randomly assigned to one of the two groups: ultrasound-guided paramedian (UG) and conventional blind paramedian (PG). In the UG paramedian group, pre-procedural ultrasound was performed to mark the insertion site, whereas, in the PG group, the landmark technique was used. A total of 22 different anaesthesiology residents performed all subarachnoid blocks.

RESULTS

The time taken to perform spinal anaesthesia in the UG group was 38-49.5 s, which is shorter than the time taken in the PG group, which was 38-55 s, with a p-value < 0.046, which is statistically significant. The primary outcome of a successful dural puncture on the first attempt was not significantly higher in the UG group (49.33%) than in the PG group (34.67%), with a p-value < 0.068. The number of attempts taken for a successful spinal tap in the UG group was a median of 2.0 (1 to 2), and the PG group had a median of 2 (1 to 2.5), with a p-value < 0.096, which is statistically non-significant.

CONCLUSION

Ultrasound guidance showed improvement in the success rate of paramedian anaesthesia. In addition, it improves the success rate of dural puncture and the rate of puncture on the first attempt. It also shortens the time required for a dural puncture. In the general population, the pre-procedural UG paramedian group did not outperform the PG paramedian group.

Comparative evaluation of three techniques for paramedian subarachnoid block: Point-of-care preprocedural ultrasound assisted, real-time ultrasound guided and landmark based

Background and Aims

Preprocedural ultrasound (US) assisted and real-time US-guided subarachnoid block (SAB) are useful adjuncts for successful SAB. This study compared the feasibility and efficacy of real-time US-guided SAB with preprocedural US-assisted and landmark-based SAB using paramedian approach.

Methods

The study enroled 150 American Society of Anesthesiologists I and II patients, aged 20-65 years, scheduled for lower limb orthopaedic surgery under SAB. In group L (n = 50), the patients underwent landmark-guided SAB utilising paramedian approach. In group P (n = 50), preprocedural US-assisted SAB was instituted and in group M (n = 50) real-time US-guided SAB was administered. The number of needle attempts for a successful SAB was the primary outcome. The secondary outcomes included successful SAB in first attempt, time taken to perform SAB and patients' satisfaction.

Results

The number of attempts for SAB were (mean ± standard deviation = 1.05 ± 0.35, 1.00 ± 0.28, 1.03 ± 0.26) in groups L, P and M, respectively (P = 0.436). The SAB was successful in the first attempt in 82%, 82% and 80% in groups L, P and M, respectively (P = 0.207). The time taken for the successful SAB was more in group M as compared to groups L and P (groups L and M, P = 0.045 and groups P and M, P = 0.004). The patients' satisfaction score was comparable.

Conclusion

Real-time US guidance for spinal anaesthesia resulted in needle attempts comparable to landmark and preprocedural US-assisted SAB in patients with a normal spine. The time required for the completion of the block was more in real-time US-guided SAB.

Real-Time Ultrasound-Guided Versus Ultrasound-Assisted Spinal Anesthesia in Elderly Patients With Hip Fractures: A Randomized Controlled Trial

BACKGROUND

Traditional landmark-guided spinal anesthesia can be challenging in elderly patients with hip fractures. Ultrasound assistance (USAS) and real-time ultrasound guidance (USRTG) techniques can facilitate lumbar neuraxial blocks. However, it remains undetermined which method is optimal for use in elderly patients. This study aimed to evaluate which technique was associated with a higher success rate of spinal anesthesia in elderly patients with hip fractures: USAS or USRTG technique.

METHODS

A total of 114 elderly patients (≥70 years of age) with hip fractures were randomly assigned to receive spinal anesthesia using either the USAS or USRTG technique. The primary outcome was the first-attempt success rate, analyzed using the χ2 test. Secondary outcomes included first-pass success rate, the number of needle attempts and passes, locating time, procedure time, total time, adverse reactions and complications, patient satisfaction, and procedural difficulty score.

RESULTS

The first-attempt success rate (80.7% vs 52.6%; 95% confidence interval [CI], for the difference, 11.6-44.6) and first-pass success rate (63.2% vs 31.6%; 95% CI for the difference, 14.2-49) were both significantly higher in the USAS compared with the USRTG group (both P = .001). The number of attempts (1 [1-1] vs 1 [1-3]; P = .001) and median passes (1 vs 3; P < .001) were both significantly lower in the USAS group than in the USRTG group. The USRTG group had a shorter locating time (175 seconds [129-234 seconds] vs 315 seconds [250-390 seconds]; P < .001) but a longer procedure time (488 seconds [260-972 seconds] vs 200 seconds [127-328 seconds]; P < .001) and total time (694 seconds [421-1133 seconds] vs 540 seconds [432-641 seconds]; P = .036). There were no significant differences between the 2 groups with regard to the adverse reactions and complications. More patients in the USAS group had a high satisfaction score of 3 to 5 (P = .008). Overall, anesthesiologists rated the USRTG group procedure as "more difficult" (P = .008).

CONCLUSIONS

In elderly patients with hip fractures, spinal anesthesia with the USRTG technique is not superior to the USAS technique since it has a lower success rate, longer procedure time, lower satisfaction score, and is more difficult to perform. So USAS technique may be more suitable for elderly patients.

Real-time ultrasound-guided spinal anaesthesia vs pre- procedural ultrasound-guided spinal anaesthesia in obese patients

BACKGROUND AND AIMS

Spinal anaesthesia is conventionally performed using a landmark-guided midline approach. These surface landmarks may be absent, indistinct or distorted in the presence of obesity, previous spinal surgeries, deformities, or degenerative changes associated with ageing. In the present study, we compared the efficacy of real-time ultrasound (RUS)-guided paramedian approach, and pre-procedure ultrasound (PUS) landmark-guided paramedian approach in obese patients.

METHODS

Eighty patients with body mass index (BMI) >30 kg/m2 were included in the study. The participants were randomly assigned to two intervention groups, i.e., RUS and PUS approach. The primary end point was to attain a successful lumbar puncture. Variables like the number of attempts, the number of passes, the time taken for identifying landmark(s), and time for a successful lumbar puncture(s) were secondary end points and were recorded in both the groups.

RESULTS

The median number of attempts were 4 (IQR 2-4) and 2 (IQR 1-2), respectively, in the PUS and RUS group (P-value < 0.001). The median number of passes, the median time for identifying space, and the time for successful lumbar puncture was statistically significantly less in the RUS group, than the PUS group.

CONCLUSION

The time taken for the identification of the space, the number of attempts, number of passes, and the time taken for successful lumbar puncture was more in the PUS group as compared to the RUS group.

Dry spinal tap during real-time ultrasound-guided paramedian spinal injection with patient in the lateral decubitus position: A single-centre retrospective study

BACKGROUND

Real-time ultrasound-guided (USG) spinal injection is generally performed via the paramedian sagittal oblique (PMSO) ultrasound window.

OBJECTIVE

The aim of this retrospective study was to draw attention to the occurrence of 'dry tap' during real-time USG spinal injection.

DESIGN

Single-centre retrospective study.

SETTING

University teaching hospital, Hong Kong, China.

PATIENTS

Data from 113 patients (aged 69.2 ± 18.0 years and BMI 22.3 ± 3.6 kg m-2) of American Society of Anesthesiologists physical status 1 to 3 scheduled for surgery under neuraxial blockade between 2007 to 2017 were reviewed.

INTERVENTIONS

Real-time USG spinal injections or combined spinal-epidural (CSE) using the PMSO ultrasound window with the patient in the lateral decubitus position and the spinal needle inserted from the nondependent side were studied.

MAIN OUTCOME MEASURES

'Dry tap' was defined as a failure of cerebrospinal fluid (CSF) to efflux from the hub of the needle, within 3 min, with the spinal needle visualised sonographically within the thecal sac. 'Slow CSF efflux' was defined as efflux of CSF within 1 to 3 min. Irrespective of whether it was a 'dry tap' or 'slow CSF efflux', the planned dose of local anaesthetic was injected through the spinal needle.

RESULTS

The combined incidence of 'dry tap' and 'slow CSF efflux' was 23.8% (27/113) with an individual incidence for each event of 9.7% (11/113) and 14.2% (16/113), respectively. Under the conditions of this study, successful spinal anaesthesia developed in all patients.

CONCLUSION

'Dry tap' occurs in 9.7% of cases during real-time USG spinal injection using the PMSO ultrasound window, with the patient in the lateral decubitus position and the spinal needle inserted from the nondependent side.

TRIAL REGISTRATION

ChiCTR-IOR-1800019011, Chinese Clinical Trials Registry (www.chictr.org.cn).

Ultrasonography for lumbar neuraxial block

Ultrasonography can be useful to perform a lumbar neuraxial block. It aids in understanding the anatomy of the lumbar spine before the procedure. Pre-procedural ultrasound imaging provides information about the accurate intervertebral level for puncture, optimal needle insertion point, and depth of needle advancement for a successful neuraxial block. The key ultrasonographic views for lumbar neuraxial block include the transverse midline interlaminar and parasagittal oblique views. Ultrasonography can facilitate lumbar neuraxial block in difficult cases, such as the elderly, obese patients, and patients with anatomical abnormality of the lumbar spine. This review elucidates the basics of spinal ultrasonography for lumbar neuraxial block and the current evidence regarding ultrasound-guided neuraxial block in adults.

Ultrasound-Guided Neuraxial Anesthesia

PURPOSE OF REVIEW

There has been a recent surge of interest in clinical applications of ultrasound, which has revolutionized acute pain management. This review is to summarize the current status of ultrasound utilization in neuraxial anesthesia, the most common type of regional anesthesia.

RECENT FINDINGS

Ultrasound-assisted and ultrasound-guided neuraxial anesthesia has improved clinical accuracy and patient safety through landmark identification including proper vertebral level and midline, as well as via measurements on neuraxial space. Direct needle or catheter visualization during the entire procedure has not yet been achieved consistently. The recent introduction of ultrasound into neural anesthesia has clinical performance benefits and patient safety implications, with documented improvement on overall efficacy with higher first attempt success rate as well as less needle pass. More controlled studies are needed for the overall impact of ultrasonography in neuraxial anesthesia in obstetric and non-obstetric patients.

Could preprocedural ultrasound increase the first-pass success rate of neuraxial anesthesia in obstetrics? A systematic review and meta-analysis of randomized controlled trials

Neuraxial anesthesia is a common practice in obstetrics. Evidence suggests that preprocedural ultrasound versus the conventional landmark location method accurately identifies a given intervertebral space and predicts the needle insertion depth required to reach the spinal canal. However, whether the preprocedural ultrasound examination improves the first-pass success (FPS) rate remains elusive. Major databases were systematically searched for all relevant studies published in English up to June 2019. Eighteen randomized controlled trials including 1844 patients were enrolled. The quality of eligible studies was assessed, and predefined outcomes were synthesized by meta-analysis. The primary results showed that preprocedural ultrasound increased the FPS rate in patients with predicted puncture difficulty but not in patients who were easily punctured. Preprocedural ultrasound reduced the number of redirections and punctures and decreased the incidence of vascular puncture and backache. There was no evidence of a reduction in failed punctures. We also noted that preprocedural ultrasound prolonged the identification time but not the procedure time. Thus, this systematic review provides evidence that preprocedural ultrasound does not improve the FPS rate of neuraxial anesthesia in patients who are easily palpated, although it increases the FPS rate in patients who are difficult to palpate.

Recommendations on the Use of Ultrasound Guidance for Adult Lumbar Puncture: A Position Statement of the Society of Hospital Medicine

EXECUTIVE SUMMARY

When ultrasound equipment is available, along with providers who are appropriately trained to use it, we recommend that ultrasound guidance should be used for site selection of lumbar puncture to reduce the number of needle insertion attempts and needle redirections and increase the overall procedure success rates, especially in patients who are obese or have difficult-to-palpate landmarks. We recommend that ultrasound should be used to more accurately identify the lumbar spine level than physical examination in both obese and nonobese patients. We suggest using ultrasound for selecting and marking a needle insertion site just before performing lumbar puncture in either a lateral decubitus or sitting position. The patient should remain in the same position after marking the needle insertion site. We recommend that a low-frequency transducer, preferably a curvilinear array transducer, should be used to evaluate the lumbar spine and mark a needle insertion site. A high-frequency linear array transducer may be used in nonobese patients. We recommend that ultrasound should be used to map the lumbar spine, starting at the level of the sacrum and sliding the transducer cephalad, sequentially identifying the lumbar spine interspaces. We recommend that ultrasound should be used in a transverse plane to mark the midline of the lumbar spine and in a longitudinal plane to mark the interspinous spaces. The intersection of these two lines marks the needle insertion site. We recommend that ultrasound should be used during a preprocedural evaluation to measure the distance from the skin surface to the ligamentum flavum from a longitudinal paramedian view to estimate the needle insertion depth and ensure that a spinal needle of adequate length is used. We recommend that novices should undergo simulation-based training, where available, before attempting ultrasound-guided lumbar puncture on actual patients. We recommend that training in ultrasound-guided lumbar puncture should be adapted based on prior ultrasound experience, as learning curves will vary. We recommend that novice providers should be supervised when performing ultrasound-guided lumbar puncture before performing the procedure independently on patients.