Ultrasound-guided supra-inguinal fascia iliaca block: a cadaveric evaluation of a novel approach

Background

Regional anesthesia of the fascia iliaca is well-documented to be a successful way to control acute pain from hip fractures in the emergency department, particularly in those patients at high risk of complications from repeated doses of IV opioids. However, the majority of existing descriptions on technique for performing fascia iliaca blocks focus on approaching from inferior to the inguinal ligament, relying on supra-inguinal spread to block the lateral femoral cutaneous nerve in the iliac fossa. This study aims to investigate the utility in performing suprainguinal injection of anesthetic agents directly into the iliac fossa to provide regional anesthesia.

Ultrasound-guided supra-inguinal fascia iliaca block: a cadaveric evaluation of a novel approach

Clinical Question

Does injecting dye superior to the inguinal ligament provide significant uptake of dye in the femoral, LCFN, and ilioinguinal nerves in cadaveric models?

Methods & Study Design

• Design

This is an informational study made to illustrate the utility of an alternative supra-inguinal approach for providing regional anesthesia in those patients presenting with acute hip or knee pain.

• Population

Bilateral injections of 20 mL of 0.25% aniline blue dye were administered to six unembalmed cadavers, for a total of 12 injections available for analysis.

• Intervention

Bilateral injections of 20 mL of 0.25% aniline blue dye were administered to six unembalmed cadavers via an ultrasound guided approach, and dye uptake was analyzed in anatomic nerve distributions.

Steps of superior approach to fascia iliaca block:

Place sterile probe over the inguinal ligament, close to the anterior superior iliac spine
Orient linear probe in parasagittal oblique orientation (superior aspect facing medially)
Rock the probe so beam faces laterally to enhance fascia iliaca
Move probe infero-medially along the line of inguinal ligament until femoral artery is imaged
Moving probe supero-laterally helps identify anterior inferior iliac spine (site of rectus femoris attachment)
As you move laterally, you see “rising” of ilium towards transducer
Identify deep circumflex artery 1-2cm superficial to fascia iliaca
Needle introduced 2-4cm inferior to inguinal ligament, and advanced through the fascia iliaca at the level of inguinal ligament.
“pop” as needle passes through fascial iliaca and into the iliacus muscle
Needle withdrawn to the fascia, and position confirmed by 1cc of local anesthetic.
Injection of fluid produces a“lens”that appears. The fluid should then hydro-dissect as it migrates into the iliac fossa
End point is when local anesthetic passes freely superiorly over the iliacus muscle and into the iliac fossa.

• Outcomes

Dye uptake in the femoral, lateral femoral cutaneous nerve, and ilioninguinal nerves after supra-inguinal injection.

Results

- There was extensive spread of dye identified in the iliac fossa. (50 to 144mm of spread)
- 10 out of 12 injections also resulted in spread into the thigh along the femoral nerve
- The femoral nerve was surrounded by dye in all cases
- The LFCN was identified bilaterally in 5 cadavers, but one cadaver lacked both LFCN. LCFN was surrounded by dye in all cases in which it was present.
- It is important to realize that the ilioinguinal nerve has significant anatomic variation. The ilioinguinal nerve passed over iliac crest onto iliacus muscle and re-emerged into the abdominal wall anteriorly in 8 cases. In the other four cases it remained in the abdominal wall. It was stained blue 7 out of 8 times in this procedure as it passed over iliac crest.

Strength & Limitations

- There was no comparison group in this study (supra-inguinal approach was used in all cases).
- There were significant anatomic variations between cadavers. One cadaver was found to have no lateral femoral cutaneous nerve. There were also significant anatomic variations in positioning of the ilioinguinal nerve.
- Throughout the article, there were multiple references that the authors institution has performed over 150 supra-inguinal fascia iliata blocks without any short term complications, however no retrospective data was available in the article to confirm this.
- Low sample population (6 cadavers, 12 nerve blocks)

Authors Conclusion

“Our cadaveric dye-injection study confirms that the ultrasound-guided supra-inguinal approach result in significant spread of injectate with simultaneous involvement of both the femoral nerve and LFCN, in the iliac fossa, in the all the cadavers in which we identified theses nerves by dissection.”

Our Conclusion

This article outlines an interesting alternative approach to providing regional anesthesia for acute pain control of the hip or knee. The majority of existing descriptions on technique for performing fascia iliaca blocks focus on approaching from inferior to the inguinal ligament, relying on supra-inguinal spread to block the lateral femoral cutaneous nerve in the iliac fossa. This study demonstrates consistent bathing of the LFCN and femoral nerve with dye in cadaveric subjects with a supra-inguinal approach. However, this study does not directly demonstrate superior efficacy of the suprainguinal approach when compared to infrainguinal fascia iliaca block. Further patient-oriented studies would be needed to make such a suggestion.

The Bottom Line

Ultrasound guided suprainguinal fascia iliaca injection of dye in cadaveric subjects shows consistent and significant uptake of injectate of the femoral nerve and LFCN in the iliac fossa. Further studies are needed to show if this provides improved analgesia as compared to the conventional infrainguinal approach.

Authors

This post was written by Casey Smith, MD. Review and further commentary was provided by Danika Brodak, MD, Emergency Ultrasound Fellow at UCSD and Amir Aminlari, MD, Ultrasound Faculty at UCSD.

References

Hebbard P, Ivanusic J, Sha S. Ultrasound-guided supra-inguinal fascia iliaca block: a cadaveric evaluation of a novel approach. Anaesthesia. 2011;66(4):300‐305. doi:10.1111/j.1365-2044.2011.06628.x

April 24, 2020July 21, 2020

Case # 18: Respiratory Distress: It’s not all COVID.

During the COVID-19 pandemic, a 67 year old woman is brought to the ER by family for respiratory distress and altered mental status. She was alert but not oriented and unable to answer questions on arrival with moderate respiratory distress. Family stated that she had a history of asthma and takes "other" medications, but where otherwise unaware of her past medical history. She had been using her inhaler without relief and has not had any sick contacts, cough or fever.

Vitals: T: 98.7, HR: 112, BP: 190/110, RR: 40, SpO2 80 on RA

She was in moderate respiratory distress, crackles on exam, no pitting edema. She was placed on a non-breather (avoiding NIPPV) and a thoracic plus cardiac ECHO was preformed.

After reviewing the images, what would you do next?

Answer and Learning Points

Answer

The images would suggest that this patient is most likely suffering from heart failure with an acute exacerbation. There are diffuse B-lines, obvious decrease contractility and a dilated IVC. These images are not typical of COVID-19 infections, which have pleural thickening and scattered b-lines (see COVID section). This patient was put on a nitro drip and given diuretics, with a significant improvement in her respiratory status in the ER. She ultimately tested COVID negative and was discharged from the hospital after aggressive diuresis.

During the same shift, numerous COVID-19 positive patients were seen. Below are images of COVID-19 cases for comparison and more can be found at The POCUS Atlas.

While the sensitivity and specificity of ultrasound to diagnosis COVID-19 has yet to be determined, this case illustrates how alternative findings can still impact clinical care and potentially avoid intubation.

COVID +

On the same shift, numerous COVID-19 patients were also seen, with variable pre-test probability. ECHO for these patients would not reveal an alternative diagnosis (such as our CHF case). There were however some classic findings on ultrasound. Note below two patients with thoracic scans. There are scattered B-lines (unlike our CHF patient, who had diffuse B-lines). There is also pleural thickening and at times an irregular pleural border.

Author

Sukhdeep Singh, MD. Clinical Faculty, UCSD Department of Emergency Medicine. Director of POCUS, El Centro Regional Medical Center.

References

DeRose et al, How to Perform Pediatric Lung Ultrasound Examinations in the Time of COVID‐19. Journal of Ultrasound in Medicine. 22 April 2020.
The POCUS Atlas. http://www.thepocusatlas.com/covid19

November 9, 2018July 21, 2020

Point-of-Care Ultrasonography for Evaluation of Acute Dyspnea in the ED

Background

Dyspnea is a common presenting symptom in the emergency department, and early diagnosis of underlying disease pathology is crucial in rapid intervention and treatment. Laboratory and radiological tests aid in the diagnosis, but often these results take time.^1-3 Additionally, chest radiographs and chest CTs, the most common radiological tests in the evaluation of dyspnea, have several disadvantages including radiation risks and high costs. Unlike these modalities, point-of-care ultrasound (PoCUS) is cheap with no radiation risk, highly accurate, and has better sensitivity in detecting pneumothorax, pneumonia, and pleural effusions than CXR.^4-7 In addition to being accurate and reliable, PoCUS can be performed rapidly to aid in early diagnosis and treatment of patients.

Point-of-Care Ultrasonography for Evaluation of Acute Dyspnea in the ED

Clinical Question

What is the feasibility and diagnostic accuracy of PoCUS for the management of acute dyspnea in the ED?

Methods & Study Design

Design:

Prospective, blinded, observational study

Population:

This study was conducted at Careggi University Hospital, a university-affiliated teaching hospital.

Inclusion Criteria:

Patients over the age of 18 with acute dyspnea of any degree.

Exclusion Criteria:

Patients with dyspnea of traumatic origin, and those that were discharged from the emergency department after evaluation.

Intervention:

All patients were primarily assessed by 2 separate emergency physicians with vital signs, history, physical exam, and EKG.

One physician performed a Lung, Cardiac, and IVC PoCUS.

One physician performed a standard workup using any combination of Chest X-Ray, Chest CT, Echocardiogram, labs, or Arterial Blood Gas.

Both physicians were asked to make up to 2 diagnoses based on their results.

Possible diagnoses: Heart Failure, Acute Coronary Syndrome, Pneumonia, Pleural Effusion, Pericardial Effusion, COPD/asthma, Pulmonary Embolism, Pneumothorax, ARDS/ALI, Other.

Outcomes

Primary:

Accuracy of diagnosis:

Follow-up chart review determined the reference diagnosis. Results were compared to the diagnosis obtained from the ultrasound group and the standard workup group.

Secondary:

Time to final diagnosis for both groups was recorded.

Time for Ultrasound completion was recorded.

Results

3,487 total patients → 2,683 included in study

Average time to complete US: 7±2 min

Average time to Diagnosis:

Ultrasound: 24 ± 10 minutes

ED: 186 ± 72 minutes

Variable	Sensitivity - Ultrasound	Sensitivity - Standard
Heart Failure	88 (85.1-90.6)	77.3 (73.7 – 80.6)
COPD/asthma	86.6 (84.2-89.2)	92.2 (90.1-94)
Pulmonary Embolism	40 (30.1-50.6)	90.5 (82.8-95.6)

Point-of-care ultrasound had an increased sensitivity in detecting heart failure compared to standard workup.
Point-of-care ultrasound had a decreased sensitivity in diagnosing COPD/asthma and pulmonary embolism compared to standard workup.

There were no differences in the sensitivity or specificity of ultrasound vs. standard workup in all other diagnoses.

Strength & Limitations

Strengths

Adequate sample size obtained for most diagnoses.

Gold standard diagnosis was reviewed by two separate emergency medicine physicians.

Limitations

Ultrasound sonographers focused only on those patients with dyspnea, while the treating physicians were responsible for other patients in the ED.

This likely increased the time to diagnosis for emergency physicians in the standard workup group.

Patients discharged from the hospital were not included in study.

Average age of patient population was 71, but patients 18 and over were accepted.

ARDS patient studies were underpowered.

Authors Conclusion

“Integrated ultrasound methods could replace the current first diagnostic approach to patients presenting with dyspnea, allowing a drastic reduction in costs and diagnostic times.”

Our Conclusion

Point-of-Care Ultrasound in patients with dyspnea provides us with quick information to begin treatment before other laboratory and radiological tests become available. While this study showed that ultrasound was superior to the standard workup in detecting heart failure, it was slightly inferior to the standard workup in detecting COPD/asthma, and significantly inferior to standard workup in detecting pulmonary embolism. The authors speculated that with the inclusion of a DVT ultrasound study would improve the sensitivity for detecting PEs greatly.

There have been other studies demonstrating increased sensitivity using ultrasound in patients to diagnose pneumonia and pleural effusions compared to chest x-ray. This study contributed to our knowledge of the accuracy of ultrasound in undifferentiated dyspnea by demonstrating its accuracy in these other important diagnoses. The study shows that PoCUS can guide and the emergency physician’s workup, help risk-stratify, can help us to begin treatment quickly, and improveflow and efficiency in the ED.

The Bottom Line

Although PoCUS won’t replace a standard workup in many cases, PoCUS can rapidly and accurately aid in determining the underlying diagnosis in patients presenting to the ED with undifferentiated dyspnea and may lead to quicker treatment times and improved flow in the emergency department.

Authors

This post was written by Marissa Wolfe, MS4 at Stony Brook University. Review and further commentary was provided by Amir Aminlari, MD, Ultrasound Faculty at UCSD.

References

Mulrow CD, Lucey CR, Farnett LE. Discriminating causes of dyspnea through clinical examination. J Gen Intern Med. 1993;8(7):383-392.
Schmitt BP, Kushner MS, Wiener SL. The diagnostic usefulness of the history of the patient with dyspnea. J Gen Intern Med. 1986;1(6):386-393.
Nielsen LS, Svanegaard J, Wiggers P, Egeblad H. The yield of a diagnostic hospital dyspnoea clinic for the primary health care section. J Intern Med. 2001;250(5):422-428.
Lichtenstein D, Mezière G. Relevance of lung ultrasound in the diagnosis of acute respiratory failure: the BLUE protocol. Chest. 2008;134(1):117-125.
Reissig A, Copetti R, Mathis G, et al. Lung ultrasound in the diagnosis and follow-up of community-acquired pneumonia: a prospective, multicenter, diagnostic accuracy study. Chest. 2012;142(4): 965-972.
Zanobetti M, Poggioni C, Pini R. Can chest ultrasonography replace standard chest radiography for evaluation of acute dyspnea in the ED? Chest. 2011;139(5): 1140-1147.
Nazerian P, Volpicelli G, Vanni S, et al. Accuracy of lung ultrasound for the diagnosis of consolidations when compared to chest computed tomography. Am J Emerg Med. 2015;33(5):620-625.

July 28, 2017July 22, 2020

Comparison of Four Views to Single-View Ultrasound Protocols to Identify Clinically Significant Pneumothorax

Background

Ultrasound has become a key adjunct for the initial evaluation of trauma patients in the emergency department (ED), with the eFAST, or extended focused assessment with sonography in trauma examination, including lung evaluation for the presence of a pneumothorax (PTX) or hemothorax. While prior research has shown ultrasound (US) to be very effective at identifying a PTX [1], there is no standardized imaging protocol that has been shown be superior to others. The two most common approaches are a single view of each hemithorax and four views of each hemithorax [2] —this paper sets out to determine if the single view strategy is sufficient to identify a clinically significant PTX.

Comparison of Four Views to Single-view Ultrasound Protocols to Identify Clinically Significant Pneumothorax

Clinical Question

Does the single-view or four-view lung US technique have a higher diagnostic accuracy for the identification of clinically significant PTX in trauma patients?

Methods & Study Design

Population
- The study was conducted at a single urban academic ED with an annual volume of 130,000 patients and a dedicated Level I trauma service staffed by trauma surgeons and EM physicians. Adult patients with acute traumatic injury who were undergoing a CT scan of the chest as part of their clinical care were eligible for enrollment.
Intervention
- Patients were assigned to one of two imaging protocols, a single view of each hemithorax or four views of each hemithorax prior to any CT imaging being done, with US images obtained by emergency physicians or the attending trauma surgeon using a 7.5-Mhz (5- to 10-MHz) linear array transducer. US exams were performed by both residents and attending physicians who had been credentialed in both US protocols.
Outcomes
- Researchers looked for the ability of US to identify clinically significant PTX requiring chest tube placement; a PTX was considered clinically insignificant if the radiologist, who was blinded to the US interpretation, read the CT scan as a thin collection of air up to 1 cm thick in the greatest slice or seen on fewer than five contiguous slices.
Design
- This was a randomized, prospective trial on trauma patients.
Excluded
- The study excluded any patient who was too unstable and required clinical care that prevented performing a chest wall US, patients with a chest tube in place prior to arrival, children, pregnant women, and prisoners.

Results

- For clinically significant PTX, CXR showed a sensitivity of 48.0% and specificity of 100%, a single view US showed a sensitivity of 93.0% and a specificity of 99.2%, and four views showed a sensitivity of 93.3% and specificity of 98.0%. There was no statistically significant difference in either sensitivity or specificity when comparing single view and four-view for clinically significant or any PTX.

Strengths & Limitations

Strengths
- Randomized, prospective trial
- 100% agreement between the initial US read by the performing provider and the study author, for a Cohen’s kappa of 1
Limitations
- Study was conducted at a single center with a limited number of US operators
- Standard prehospital approach to spinal immobilization that results in placement of patients supine on a long board - in areas where this approach may differ (e.g., patients arrive semirecumbent or upright), the positioning of a PTX in the chest may be altered, rendering a single view of the anterior chest wall less accurate
- As this study was a convenience sample that required the treating physician to remember to enroll the patient and randomize them prior to performing the US, there is a possibility of selection bias

Author's Conclusions

"The sensitivities are equivalent for both a single view and four views of each hemithorax when using point-of-care ultrasound to evaluate for a clinically significant pneumothorax in the trauma population. The additional time required for additional views should be weighed against the lack of additional diagnostic accuracy when evaluating critically ill and time-sensitive trauma patients in the ED."

Our Conclusions

Although not all PTXs are located anteriorly and multiple views of each hemithorax may be thought to maximize sensitivity and/or allow the physician to be able to attempt to quantify the size of the PTX, performing eight views instead of two views during the eFAST requires extra time while adding no diagnostic value. From this study, it appears that a single view on each side of the thorax is sufficient to detect clinically significant PTXs on trauma patients.

As with any diagnostic tool, it is important to remember its limitations. Specifically, the US exams in this study were done in supine patients, who were brought in by EMS in a supine position, allowing the pneumothorax to move to the most anterior portion of the chest. Caution should be taken when applying the test characteristics of this study to patients that are not in the supine position. There was also one patient who had a significant PTX that was missed by US and required a chest tube. This patient had received a needle decompression by prehospital providers and was randomized to a single anterior US chest view that was performed just lateral to the needle insertion site which may have led to false negative US exam. It appears this specific group of patients may benefit from a more comprehensive four-view lung examination.

The Bottom Line

A single anterior view on each side of the chest in a supine patient is sufficient to detect clinically significant pneumothoraces.

Authors

This post was written by Ben Foorman, MS4 at UCSF. It was edited by Michael Macias, MD.

References

1. Lichtenstein DA, e. (2017). Ultrasound diagnosis of occult pneumothorax. - PubMed - NCBI . Ncbi.nlm.nih.gov. Retrieved 28 July 2017, from https://www.ncbi.nlm.nih.gov/pubmed/15942336
2. Blaivas M, e. (2017). A prospective comparison of supine chest radiography and bedside ultrasound for the diagnosis of traumatic pneumothorax. - PubMed - NCBI . Ncbi.nlm.nih.gov. Retrieved 28 July 2017, from https://www.ncbi.nlm.nih.gov/pubmed/16141018
3. Helland G, e. (2017). Comparison of Four Views to Single-view Ultrasound Protocols to Identify Clinically Significant Pneumothorax. - PubMed - NCBI . Ncbi.nlm.nih.gov. Retrieved 28 July 2017, from https://www.ncbi.nlm.nih.gov/pubmed/27428394