Regional anaesthesia in the obese patient: lost landmarks and evolving ultrasound guidance

Artificial intelligence-assisted ultrasound-guided regional anaesthesia: An explorative scoping review

Purpose

The present study reviews the available scientific literature on artificial intelligence (AI)-assisted ultrasound-guided regional anaesthesia (UGRA) and evaluates the reported intraprocedural parameters and postprocedural outcomes.

Methods

A literature search was performed on 19 September 2023, using the Medline, EMBASE, CINAHL, Cochrane Library and Google Scholar databases by experts in electronic searching. All study designs were considered with no restrictions regarding patient characteristics or cohort size. Outcomes assessed included the accuracy of AI-model tracking, success at the first attempt, differences in outcomes between AI-assisted and unassisted UGRA, operator feedback and case-report data.

Results

A joint adaptive median binary pattern (JAMBP) has been applied to improve the tracking procedure, while a particle filter (PF) is involved in feature extraction. JAMBP combined with PF was most accurate on all images for landmark identification, with accuracy scores of 0.83, 0.93 and 0.93 on original, preprocessed and filtered images, respectively. Evaluation of first-attempt success of spinal needle insertion revealed first-attempt success in most patients. When comparing AI application versus UGRA alone, a significant statistical difference (p < 0.05) was found for correct block view, correct structure identification and decrease in mean injection time, needle track adjustments and bone encounters in favour of having AI assistance. Assessment of operator feedback revealed that expert and nonexpert operator feedback was overall positive.

Conclusion

AI appears promising to enhance UGRA as well as to positively influence operator training. AI application of UGRA may improve the identification of anatomical structures and provide guidance for needle placement, reducing the risk of complications and improving patient outcomes.

Level of Evidence

Level IV.

Ultrasound-Guided External Oblique Intercostal Plane Block for Postoperative Analgesia in Laparoscopic Sleeve Gastrectomy: A Prospective, Randomized, Controlled, Patient and Observer-Blinded Study

PURPOSE

The external oblique intercostal plane (EOI) block is a novel block technique for anterolateral upper abdominal wall analgesia. The superficial nature of the external oblique intercostal plane allows it to be easily identified even in patients with obesity. The aim of this study was to test the hypothesis that EOI block would reduce IV morphine consumption within 24 h after laparoscopic sleeve gastrectomy.

MATERIALS AND METHODS

Patients were randomly assigned to one of two groups: EOI block group and control group. The patients in the EOI block group received ultrasound-guided bilateral EOI block with a total of 40 ml 0.25% bupivacaine after anesthesia induction. The patients in the control group received no intervention. Postoperatively, all the patients were connected to an intravenous patient controlled analgesia (PCA) device containing morphine. The primary outcome of the study was IV morphine consumption in the first postoperative 24 h.

RESULTS

The median [interquartile range] morphine consumption at 24 h postoperatively was significantly lower in the EOI block group than in the control group (7.5 [3.5 to 8.5] mg vs 14 [12 to 20] mg, p = 0.0001, respectively). Numerical rating scale (NRS) scores at rest and during movement were lower in the EOI block group than in the control group at 2, 6, and 12 h but were similar at 24 h. No block-related complications were observed in any patients.

CONCLUSION

The results of the current study demonstrated that bilateral EOI block reduced postoperative opioid consumption and postoperative pain in patients with obesity undergoing laparoscopic sleeve gastrectomy.

TRIAL REGISTRATION

Clinicaltrials.gov identifier: NCT05663658.

Comparison of Performance Characteristics and Efficacy of Bilateral Thoracic Paravertebral Blocks in Obese and Non-Obese Patients Undergoing Reduction Mammaplasty Surgery: A Historical Cohort Study

BACKGROUND

Although ultrasound (US)-guided regional anesthesia techniques are advantageous in the management of obese patients; the procedures can still be associated with technical difficulties and greater failure rates. The aim of this study is to compare the performance properties and analgesic efficacy of US-guided bilateral thoracic paravertebral blocks (TPVBs) in obese and non-obese patients.

METHODS

Data of 82 patients, who underwent bilateral reduction mammaplasty under general anesthesia with adjunctive TPVB analgesia between December 2016 and February 2020, were reviewed. Patients were allocated into two groups with respect to their BMI scores (Group NO: BMI < 30 and Group O: BMI ≥ 30). Demographics, ideal US visualization time, total bilateral TPVB procedure time, needle tip visualization and performance difficulties, number of needle maneuvers, surgical, anesthetic and analgesic follow-up parameters, incidence of postoperative nausea and vomiting (PONV), sleep duration, length of postanesthesia care unit (PACU) and hospital stay, and patient/surgeon satisfaction scores were investigated.

RESULTS

Seventy-nine patients' data were complete. Ideal US visualization and total TPVB performance times were shorter, number of needle maneuvers were fewer and length of PACU stay was shorter in Group NO (p < 0.05). Postoperative pain scores were generally similar within first 24 h (p > 0.05). Time to postoperative pain, total analgesic requirements, incidence of PONV, sleep duration, length of hospital stay were comparable (p > 0.05). Satisfaction was slightly higher in Group NO (p < 0.05).

CONCLUSIONS

US-guided TPVB performances in obese patients might be more challenging and take longer time. However, it is still successful providing good acute pain control in patients undergoing reduction mammaplasty surgeries.

LEVEL OF EVIDENCE III

This journal requires that authors assign a level of evidence to each article. For a full description of these Evidence-Based Medicine ratings, please refer to the Table of Contents or the online Instructions to Authors www.springer.com/00266 .

TRIAL REGISTRATION

NCT04596787.

Analgesic Efficacy and Outcomes of Ultrasound-guided Erector Spinae Plane Block in Patients Undergoing Bariatric and Metabolic Surgeries: A Systematic Review

Erector spinae plane block (ESPB) has been used as an intervention for providing postoperative analgesia in patients undergoing bariatric and metabolic surgeries. After registering the protocol in PROSPERO, randomized controlled trials and nonrandomized observational studies were searched in various databases till July 2022. The primary outcome was 24-h opioid consumption; the secondary outcomes were intraoperative opioid use, pain scores, time to rescue analgesia, and complications. The risk of bias and Newcastle-Ottawa scale were used to assess the quality of evidence. From the 695 studies identified, 6 studies were selected for analysis. The 24-h opioid consumption was significantly lesser in ESPB group when compared to control (mean difference [MD]: -10.67; 95% confidence interval [CI]: -21.03, -0.31, I² = 99%). The intraoperative opioid consumption was significantly less in the ESPB group (MD: -17.75; 95% CI: -20.36, -15.13, I² = 31%). The time to rescue analgesia was significantly more in the ESPB group (MD: 114.36; CI: 90.42, 138.30, I² = 99%). Although pain scores were significantly less at 6 and 24 h in ESPB group (MD: -2.00, 95% CI: -2.49, -1.51; I² = 0% and MD: -0.48; 95% CI: -0.72, -0.24; I² = 48%), at zero and 12 h, the pain scores were comparable (MD: -1.53, 95% CI: -3.06, -0.00, I² = 97% and MD: -0.80; 95% CI: -1.80, 0.20, I² = 88%). Bilateral ESPB provides opioid-sparing analgesia and better pain scores when compared to control. These results should be interpreted with caution due to high heterogeneity among the included studies.

Does Point-of-Care Ultrasound Change the Needle Insertion Location During Routine Bedside Paracentesis?

BACKGROUND

Paracentesis is a bedside procedure to obtain ascitic fluid from the peritoneum. Point-of-care ultrasound (POCUS) improves the safety of some medical procedures. However, the evidence supporting its utility in paracentesis is limited.

OBJECTIVE

We aimed to assess if POCUS would yield a user-preferred site for needle insertion compared to conventional landmarking, defined as a ≥ 5 cm change in location.

DESIGN

This was a prospective non-randomized trial comparing a POCUS-guided site to the conventional anatomic site in the same patient.

PARTICIPANTS

Adult patients at Kingston Health Sciences Centre undergoing paracentesis were included.

INTERVENTIONS

Physicians landmarked using conventional technique and compared this to a POCUS-guided site. The paracentesis was performed at whatever site was deemed optimal, if safe to do so.

MAIN MEASURES

Data collected included the distance from the two sites, depth of fluid pockets, and anatomic considerations.

KEY RESULTS

Forty-five procedures were performed among 30 patients and by 24 physicians, who were primarily in their PGY 1 and 2 years of training (33% and 31% respectively). Patients' ascites was mostly due to cirrhosis (84%) predominantly due to alcohol (47%) and NAFLD (34%). Users preferred the POCUS-guided site which resulted in a change in needle insertion ≥ 5 cm from the conventional anatomic site in 69% of cases. The average depth of fluid was greater at the POCUS site vs. the anatomic site (5.4±2.8 cm vs. 3.0±2.5 cm, p < 0.005). POCUS deflected the needle insertion site superiorly and laterally to the anatomic site. The POCUS site was chosen (1) to avoid adjacent organs, (2) to optimize the fluid pocket, and (3) due to abdominal wall considerations, such as pannus. Six cases landmarked anatomically were aborted when POCUS revealed inadequate ascites.

CONCLUSIONS

POCUS changes the needle insertion site from the conventional anatomic site for most procedures, due to optimizing the fluid pocket and safety concerns, and helped avoid cases where an unsafe volume of ascites was present.

Dyspnea induced by hemidiaphragmatic paralysis after ultrasound-guided supraclavicular brachial plexus block in a morbidly obese patient

RATIONALE

Hemidiaphragmatic paralysis (HDP) is a frequent complication of the brachial plexus block, caused by unintentional blockade of ipsilateral phrenic nerve. HDP did not rise enough alarm and attention to most anesthesiologists, because most patients with no coexisting comorbid diseases are asymptomatic and able to tolerate it. However, it may cause severe respiratory complication for patients with preexisting compromised cardiorespiratory function.

PATIENT CONCERNS

A 67-year-old woman with morbidly obesity was planned to receive opening reduction and internal fixation of right humeral shaft fracture under regional anesthesia considering less respiratory and cardiovascular system interference compared with general anesthesia.

DIAGNOSES

After ultrasound guided supraclavicular brachial plexus block, the patient developed severe hypoxia and hypercapnia.Unintentional block of phrenic nerve and diaphragm paralysis was diagnosed by diaphragm ultrasound, which was considered as the main reason of severe hypoxia.

INTERVENTIONS

It led to a conversion from regional anesthesia to general anesthesia with endotracheal intubation for patient's safety and smooth operation.

OUTCOMES

The unintentional phrenic nerve block leads to a prolonged ventilation time, length of stay in intensive care unit and length of stay in hospital.

LESSONS

This case report highlights the risk of diaphragm paralysis in morbidly obese patients. Though new diaphragm sparing brachial plexus block (BPB) methods were developed intended to reduce the risk of HDP, no approaches could absolutely spare phrenic nerve involvement. Therefore, clinicians should always consider the risk of HDP associated with BPBs. For each individual, a detailed preoperative evaluation and sufficient preparation are paramount to avoid serious complications.

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.

Sonographic visibility of cannulas using convex ultrasound transducers

The key for safe ultrasound (US)-guided punctures is a good visibility of the cannula. When using convex transducers for deep punctures, the incident angle between US beam and cannula varies along the cannula leading to a complex visibility pattern. Here, we present a method to systematically investigate the visibility throughout the US image. For this, different objective criteria were defined and applied to measurement series with varying puncture angles and depths of the cannula. It is shown that the visibility not only depends on the puncture angle but also on the location of the cannula in the US image when using convex transducers. In some image regions, an unexpected good visibility was observed even for steep puncture angles. The systematic evaluation of the cannula visibility is of fundamental interest to sensitise physicians to the handling of convex transducers and to evaluate new techniques for further improvement.

[Ultrasound-guided costoclavicular block as an alternative for upper limb anesthesia in obese patients]

BACKGROUND AND OBJECTIVES

Costoclavicular brachial plexus block is an anesthesia performed through the infraclavicular route described in the literature as a safe and effective route for upper limb anesthesia distal to the elbow. The following report describes the case of a patient whose traditional plexus blocking techniques presented ultrasound visualization difficulty, but the costoclavicular approach was easy to visualize for anesthetic blockade.

CASE REPORT

A grade 3 obese patient scheduled for repair of left elbow fracture and dislocation. Ultrasound examination revealed a distorted anatomy of the supraclavicular region and the axillary region with skin lesions, which made it impossible to perform the blockade in these regions. It was decided to perform an infraclavicular plexus block at the costoclavicular space, where the brachial plexus structures are more superficial and closer together, supported by a muscular structure, lateral to all adjacent vascular structures and with full view of the pleura. The anesthetic block was effective to perform the procedure with a single injection and uneventfully.

CONCLUSION

Costoclavicular brachial plexus block is a good alternative for upper limb anesthesia distal to the elbow, being a safe and effective option for patients who are obese or have other limitations to the use of other upper limb blocking techniques.

Ultrasound-guided costoclavicular block as an alternative for upper limb anesthesia in obese patients

Background and objectives

Costoclavicular brachial plexus block is an anesthesia performed through the infraclavicular route described in the literature as a safe and effective route for upper limb anesthesia distal to the elbow. The following report describes the case of a patient whose traditional plexus blocking techniques presented ultrasound visualization difficulty, but the costoclavicular approach was easy to visualize for anesthetic blockade.

Case report

A grade 3 obese patient scheduled for repair of left elbow fracture and dislocation. Ultrasound examination revealed a distorted anatomy of the supraclavicular region and the axillary region with skin lesions, which made it impossible to perform the blockade in these regions. It was decided to perform an infraclavicular plexus block at the costoclavicular space, where the brachial plexus structures are more superficial and closer together, supported by a muscular structure, lateral to all adjacent vascular structures and with full view of the pleura. The anesthetic block was effective to perform the procedure with a single injection and uneventfully.

Conclusion

Costoclavicular brachial plexus block is a good alternative for upper limb anesthesia distal to the elbow, being a safe and effective option for patients who are obese or have other limitations to the use of other upper limb blocking techniques.

Comparison of general versus isolated regional anesthesia in total shoulder arthroplasty: A retrospective propensity-matched cohort analysis

BACKGROUND

Intraoperative anesthetic typically consists of either general anesthesia (GA) or isolated regional anesthesia (RA).

METHODS

A retrospective propensity-matched cohort analysis on patients undergoing TSA was performed to determine differences between GA and RA in regard to patient population, complications, LOS and hospital readmission.

RESULTS

4158 patients underwent TSA with GA or isolated RA. Propensity-matching resulted in 912 patients in each cohort. RA had lower overall in-hospital complications and greater homebound discharge disposition with lower 90-day readmission rates than GA.

CONCLUSION

After TSA, isolated RA was associated with lower in-hospital complications, readmission rates and odds of hospital readmission than GA.

Morbid Obesity and Total Knee Arthroplasty: A Growing Problem

Obesity is an epidemic, with approximately 35% of the US population affected. This rate is unlikely to decline and may increase the demand for total knee arthroplasty (TKA). Data regarding the risks, benefits, and potential complications of TKA in this patient population are conflicting. Preoperative considerations are optimization of nutritional status, safe weight loss strategies, and bariatric surgery. Intraoperative concerns unique to this population include inadequate exposure, implant alignment, and durable implant fixation; postoperative issues include tibial loosening, wound complications, cardiovascular events, and respiratory complications. A thorough understanding of the medical and surgical complications associated with TKA in the obese patient will facilitate research efforts and improve outcomes.

Severe and morbid obesity (BMI ≥ 35 kg/m(2)) does not increase surgical time and length of hospital stay in total knee arthroplasty surgery

PURPOSE

Certain aspects of total knee arthroplasty (TKA) in severely and morbidly obese (SMO) patients (BMI ≥ 35 kg/m(2)) remain controversial. This study aimed to assess the duration of TKA surgery and hospital stay in relation to patients' BMI.

METHODS

Three operative times during TKA surgery were recorded: tourniquet time, to determine surgical difficulty, total surgical time, to assess the difficulty of achieving anaesthesia, and time in the surgical area, to assess patient management in the surgical area. Length of hospital stay was also calculated. Data were collected prospectively from consecutive patients and were recorded in a database for retrospective analysis.

RESULTS

Data were obtained from 922 consecutive patients undergoing TKA. The non-obese group comprised 418 patients (45.3%), obese group Class I 331 (36%), and the SMO group (Class II-III) 173 (18.7%). Mean tourniquet time was 53 min, mean total surgical time was 84 min, and mean time in the surgical area was 132 min. There were no differences according to BMI group. Median length hospital stay (LHS) was 6 days in all patients regardless of BMI. Factors that significantly prolonged LHS were ASA III-IV and pre-operative haemoglobin between 12 and 13 g/dl.

CONCLUSION

Severely and morbidly obese (SMO) patients (BMI ≥ 35 kg/m(2)) undergoing TKA surgery do not require longer operative time or hospital stay than non-obese or obese Class I patients. The fact that surgical time was not significantly different could be due to greater specialisation in the treatment of these patients, which may favour a lower incidence of post-operative complications.

LEVEL OF EVIDENCE

Retrospective comparative study, Level IV.

A randomized clinical trial comparing the effectiveness of ultrasound guidance versus nerve stimulation for lateral popliteal-sciatic nerve blocks in obese patients

OBJECTIVES

Ultrasound guidance may decrease the procedural time for many peripheral nerve blocks compared to nerve stimulation, but these studies have generally excluded obese patients. This single-blinded randomized clinical trial was designed to compare procedural times and related outcomes for ultrasound- versus nerve stimulation-guided lateral popliteal-sciatic nerve blockade specifically in obese patients.

METHODS

With Institutional Review Board approval and informed consent, patients with a body mass index greater than 30 kg/m(2) who were scheduled for foot/ankle surgery and desiring a peripheral nerve block were offered enrollment. Study patients were randomly assigned to receive a lateral popliteal-sciatic nerve block under either ultrasound or nerve stimulation guidance. The patient and assessor were blinded to group assignment. The primary outcome was procedural time in seconds. Secondary outcomes included number of needle redirections, procedure-related pain, patient satisfaction with the block, success rate, sensory and motor onset times, block duration, and complication rates.

RESULTS

Twenty-four patients were enrolled and completed the study. All patients had successful nerve blocks. The mean procedural times (SD) were 577 (57) seconds under nerve stimulation and 206 (40) seconds with ultrasound guidance (P< .001; 95% confidence interval for difference, 329-412 seconds). Patients in the ultrasound group had fewer needle redirections and less procedure-related pain, required less opioids, and were more satisfied with their block procedures. There were no statistically significant differences in other outcomes.

CONCLUSIONS

The results of this study show that, for obese patients undergoing lateral popliteal-sciatic nerve blocks, ultrasound guidance reduces the procedural time and procedure-related pain and increases patient satisfaction compared to nerve stimulation while providing similar block characteristics.

Anesthetic challenges in the obese patient

Obesity seems to be the modern concern to society. An increasing number of obese patients present annually to surgical wards to undergo surgical procedures. As morbid obesity affects most of the vital organs, the anesthesiologist must be prepared to deal with several challenges. These include the preoperative evaluation of the consequences of obesity, particularly on cardiac, respiratory, and metabolic systems; airway management; different pharmacokinetic and pharmacodynamic drug regimen; and perioperative management (i.e., hemodynamic, respiratory, and hyperglycemic). This paper reviews and assesses the most important anesthetic issues in managing obese patients.