Does adding M-mode to B-mode improve accuracy in diagnosing pneumothorax?

Background

Ultrasound has been shown to be superior to supine chest x-ray in the diagnosis of pneumothorax, with one recent systematic review demonstrating 91% sensitivity using ultrasound compared to 50% using chest x-ray.1 CT scan remains the gold standard in diagnosis but is often not feasible in unstable trauma patients. Ultrasound is recommended by ATLS guidelines for use in trauma patients as part of the eFAST protocol. There are three main described ultrasound findings in pneumothorax: lung sliding, B-lines, and the lung point. While B-mode (2D mode) is commonly described, many resources also suggest the use of M-mode (motion mode).

This study evaluates whether the addition of M-mode to B-mode impacts the sensitivity, specificity, and accuracy of bedside ultrasound in the diagnosis of lung sliding. Previous studies have evaluated the accuracy of M-mode on cadaveric subjects2, but no previous studies have investigated the accuracy of M-mode + B-mode compared to B-mode alone in live human subjects.

Does adding M-mode to B-mode improve accuracy in diagnosing pneumothorax?

Avila, J et al. Does the Addition of M-Mode to B-Mode Ultrasound Increase the Accuracy of Identification of Lung Sliding in Traumatic Pneumothoraces?. J Ultrasound Med, 37: 2681-2687

Clinical Question

Does the addition of M-mode to B-mode improve accuracy in identifying lung sliding? Does this vary by ultrasound experience and level of training?

Methods & Study Design

Design:
Survey

Population:
Emergency Physicians including residents, fellows, and attending physicians

Intervention:
Hemithorax anterior lung field ultrasound scans were performed on 15 patients who had a unilateral pneumothorax confirmed by CT scan. B-mode and corresponding M-mode images were obtained for each patient, with one scan on each side, producing scans of 30 lungs. These images were incorporated into a 30-question quiz in which respondents were asked to identify the presence or absence of lung sliding. One version of the quiz contained B-mode clips alone and one version contained B-mode and M-mode clips for each lung. Respondents were randomized to one of the two quizzes. The quiz was sent to EM residency directors for distribution. One hundred forty physicians responded and were randomized.

Outcomes:
Sensitivity, specificity, and accuracy of the diagnosis of lung sliding, and association with respondent ultrasound experience and level of training.

Results

Overall, the addition of M-Mode to B-Mode resulted in unchanged sensitivity, 93.1% vs 93.2%, improved specificity from 89.8% to 96% (P < 0.0001), and improved accuracy from 91.5% to 94.5% (p=0.0091).

In subgroup analysis, there was no significant difference in accuracy, sensitivity, or specificity when adding M-mode for physicians with more than 250 ultrasound scans previously performed. For physicians with less than 250 total scans previously performed, use of B-mode + M-mode increased accuracy from 88.2% to 94.4% (P = 0.001) and increased specificity from 87.0% to 97.2% (P < 0.0001) compared with B-mode alone. For resident physicians, the addition of M-mode to B-mode significantly improved accuracy from 89.6% to 94.6% (P = 0.0016) and specificity from 87.9% to 95.9% (P < 0.001) for resident physicians. There was no significant improvement for fellows and attending physicians.

Strengths and Limitations

Strengths:

The authors describe methods in detail, including how the ultrasound scans were performed, number of sites scaned, and the type of machine, probe, and settings used. They also collected detailed information on level of ultrasound experience which helps generalize results among emergency physicians with varying levels of ultrasound experience. Ultrasound results were compared to the gold standard of CT scan.

Limitations:

The survey was sent out to residency program directors to distribute to residents, fellows, and attendings, which excludes the large number of practicing emergency physicians in the community. Community physicians may have different levels of experience and formal training with ultrasound and would be an important group to include in terms of study generalizability. Additionally, the sample size was relatively small (140 total participants) and included many more residents (92) than fellows/attendings (48). The images used also did not capture the absence or presence of B-lines, which could also impact interpretation and management. This study evaluated interpretation only and did not evaluate image acquisition, which could impact the outcomes measured and would be more helpful for practical application. Finally, there may be a difference in clinical significance between pneumothorax diagnosed with x-ray or bedside ultrasound versus CT scan– CT may identify more smaller and less clinically relevant pneumothoraces which may be missed on ultrasound.

Author's Conclusions

“The addition of M-mode images to B-mode clips aids in the accurate diagnosis of lung sliding by emergency physicians. The subgroup analysis showed that the benefit of M-mode US disappears after emergency physicians have performed more than 250 US examinations.”

Our Conclusions

The addition of M-mode to B-mode can improve accuracy in identifying lung sliding when evaluating for pneumothorax when performed by emergency physicians with less training or ultrasound experience. Given this benefit, more junior physicians could be encouraged to add M-mode to their evaluation for pneumothorax, especially as the additional image acquisition required is relatively quick.

The Bottom Line

Adding M-mode to B-mode when using ultrasound to evaluate for pneumothorax improved accuracy amongst emergency physicians with less US experience.

Authors

This post was written by Julie Westover, MS4 at UCSD School of Medicine, with editing by Ben Liotta, MD and Amir Aminlari, MD.

References

Avila, J., Smith, B., Mead, T., Jurma, D., Dawson, M., Mallin, M. and Dugan, A. (2018), Does the Addition of M-Mode to B-Mode Ultrasound Increase the Accuracy of Identification of Lung Sliding in Traumatic Pneumothoraces?. J Ultrasound Med, 37: 2681-2687. https://doi.org/10.1002/jum.14629

1. Alrajhi K, Woo MY, Vaillancourt C. Test characteristics of ultrasonography for the detection of pneumothorax: a systematic review and analysis. Chest 2012; 141:703–708.
2. Adhikari S, Zeger W, Wadman M, Walker R, Lomneth C. Assessment of a human cadaver model for training emergency medicine res- idents in the ultrasound diagnosis of pneumothorax. Biomed Res Int 2014; 2014:724050

September 28, 2021September 25, 2021

Can Junior EPs Use E-Point Septal Separation to Accurately Estimate Left Ventricular Function?

Background

Point-of-care echocardiography can provide a rapid and accurate assessment of left ventricular function, which is valuable in differentiating causes of hypotension and dyspnea at bedside. Visual estimation of LV function by experienced practitioners has been shown to correlate well with quantitative estimates. However, the number of examinations required before a practitioner is qualified to visually estimate LV function accurately is unknown. Although there are various comparable parameters for assessing LV function, mitral valve E-point septal separation (EPSS) is an easy-to-obtain measurement inversely correlated with LV function. EPSS is an M-mode measurement of the minimum distance between the anterior mitral valve leaflet and the interventricular septum during diastole. Despite its applicability, the reproducibility and accuracy of EPSS as a bedside tool for evaluating LV function in less experienced emergency physicians has yet to be established.

Can Junior Emergency Physicians Use E-Point Septal Separation to Accurately Estimate Left Ventricular Function in Acutely Dyspneic Patients?

Clinical Question

This study aims to determine if novice emergency physicians (PGY 3 and PGY 4) are able to obtain EPSS measurements and determine if these measurements correlate to echocardiographic visual estimations of LV function by experienced emergency physicians.

Methods & Study Design

Design:
Prospective observational study of correlation between EPSS to visual estimation and LV function in patients who present to ED with chief complaint of acute dyspnea.

Population:
Convenience sampling of 70 subjects enrolled in the ED from July 2008 and July 2009. Criteria for enrollment included age > 18 years, chief complaint of dyspnea, ED length > 2 hours, no history of trauma, and normal mental status. Patients with known history of mitral valve repair or replacement, aortic insufficiency, or mitral stenosis were excluded.

Intervention:
12 senior residents (PGY 3 and PGY 4) in EM residency program with variable levels of ultrasound experiences (70 to 150 total ED ultrasound examinations; average of fewer than 25 cardiac examinations) performed transthoracic echocardiogram of patients with chief complaint of acute dyspnea. Ultrasound examination included subcostal, parasternal long axis (PLAX), parasternal short axis, and apical four chamber views. Six-second video clips in parasternal short and long axes were obtained. M-mode measurements of EPSS were recorded in PLAX orientation after all video clips were obtained and calculated during diastole. All examinations were performed without the presence of experienced emergency physicians (EPs).

Outcomes:
One of two experienced EPs reviewed stored video and visually estimated LVEF. Two board-certified cardiologists subsequently reviewed one-half of the video clips and estimated LVEF, blinded to both junior EPs’ EPSS measurements and visual estimations by experienced EPs.

Results

58 out of 70 enrolled subjects had complete echocardiographic studies recorded.

Concordance rates between EPSS measurements by EPs and cardiologist for LVEF were acceptable with kappa for visual LVEF estimation of 0.75 (95% CI = 0.48 to 1.00).

Spearman correlation analysis revealed significant correlation (p = -0.844, p< 0.001) between novice physicians’ measurements of EPSS and visual estimation of LVEF by experienced EPs.

Strengths and Limitations

This study compared EPSS measurement by junior EPs with visual assessment by experienced EPs showing a strong correlation. Experienced EPs were not blinded to results, which may have induced bias, but the authors find this less likely given what they interpret as good agreement on visual estimations between experienced EPs and blinded cardiologists. It is debatable whether the agreement between EPs and cardiologists with kappa of 0.75 represents good agreement. This study utilized a convenience sampling design due to logistical constraints, which may impact the generalizability of its results. Many subjects were excluded for incomplete ultrasound views, but authors note that junior EPs were actually able to assess EPSS for all subjects, further supporting the use of this measurement even when other views are difficult to obtain.

Authors Conclusions

PGY 3 and PGY 4 EM residents were able to obtain measurements of EPSS that correlated closely with visual assessments of LVEF by experienced emergency physicians with extensive point-of-care ultrasound and echocardiography experience. EPSS can serve as a quantitative alternative to visual estimation of LVEF in dyspneic ED patients.

Our Conclusions

Rapid assessment of LVEF with bedside echocardiography can provide useful clinical information in the acutely dyspneic patient. The level of expertise required to accurately visually assess a LVEF is unknown. This study supports EPSS as a useful quantitative addition to visual estimation of LVEF in patients with acute dyspnea for novice emergency physicians with less echocardiography experience. The level of correlation between EPSS and visual estimation was not perfect, suggesting use of EPSS as an addition to rather than replacement for standard visual estimation.

The Bottom Line

EPSS can serve as a quantitative addition to qualitative visual estimation of LVEF with bedside echocardiography, especially for less experienced EM practitioners.

Authors

This post was written by Eugene Han, MS4 at UCSD School of Medicine, with editing by Ben Liotta, MD and Amir Aminlari, MD.

References

1. Secko MA, Lazar JM, Salciccioli LA, Stone MB. Can junior emergency physicians use E-point septal separation to accurately estimate left ventricular function in acutely dyspneic patients? Acad Emerg Med. 2011 Nov;18(11):1223-6. doi: 10.1111/j.1553-2712.2011.01196.x. Epub 2011 Nov 1. PMID: 22044429.
2. McKaigney CJ, Krantz MJ, La Rocque CL, Hurst ND, Buchanan MS, Kendall JL. E-point septal separation: a bedside tool for emergency physician assessment of left ventricular ejection fraction. Am J Emerg Med. 2014 Jun;32(6):493-7. doi: 10.1016/j.ajem.2014.01.045. Epub 2014 Feb 3. PMID: 24630604.
3. Shahgaldi K, Gudmundsson P, Manouras A, Brodin LA, Winter R. Visually estimated ejection fraction by two dimensional and triplane echocardiography is closely correlated with quantitative ejection fraction by real-time three dimensional echocardiography. Cardiovasc Ultrasound. 2009 Aug 25;7:41. doi: 10.1186/1476-7120-7-41. PMID: 19706183; PMCID: PMC2747837.
4. McGowan JH, Cleland JG. Reliability of reporting left ventricular systolic function by echocardiography: a systematic review of 3 methods. Am Heart J. 2003 Sep;146(3):388-97. doi: 10.1016/S0002-8703(03)00248-5. PMID: 12947354.
5. Jacob M, Shokoohi H, Moideen F, Pousson A, Boniface K. An Echocardiography Training Program for Improving the Left Ventricular Function Interpretation in Emergency Department; a Brief Report. Emerg (Tehran). 2017;5(1):e70. Epub 2017 Jun 15. PMID: 29201952; PMCID: PMC5703747.

January 27, 2021May 4, 2021

Serratus Anterior Plane Block for Thoracic Wall Pain

Background

The serratus anterior plane block (SAPB) is a field block that provides analgesia from T2 to T9 dermatomes of the hemithorax by anesthetizing the lateral cutaneous branches of the intercostal nerves in that area. It was first described in a 2013 study demonstrating long-lasting thoracic-wall anesthesia with no significant adverse effects (1). It has since been utilized by anesthesia for prophylactic treatment of post-thoracotomy and post-mastectomy pain (2-4) and has demonstrated utility for treatment of rib fracture pain in the acute setting (5).

This case series describes its use in the Emergency Department (ED) for patients with thoracic wall pain from rib fractures, herpes zoster and chest tube placement.

Serratus Anterior Plane Block in the Emergency Department: A Case Series.

Clinical Question

Is the SAPB feasible, safe and efficacious when used for a variety of thoracic wall pain syndromes in the ED?

Methods & Study Design

Case series in which six patients (age 60-94) underwent SAPB for treatment of thoracic pain. Exclusion criteria were not specified; however, patients were included regardless of pre-procedural, multimodal analgesic use. The authors recorded extent of injury and indication for SAPB. Outcomes of interest included efficacy of the nerve block and adverse events due to SABP during hospital stay.

SAPB was performed as follows: 25-30 mL of anesthetic (0.25% bupivacaine) was injected under ultrasound-guidance into the serratus anterior plane, either superficial (n=4) or deep (n=2) to the serratus anterior muscle. Sonographic landmarks for identification of the injection site included the lateral borders of the latissimus dorsi muscle and pectoralis muscle.

Image 1: Serratus anterior plane block sono-anatomy. Yellow line, target plane; purple-dotted line, needle; blue line, pleura. SCT, subcutaneous tissue; SAM, serratus anterior muscle; LDM, latissimus dorsi muscle; ICM, intercostal muscle (Lin et al 2020).

Results

SAPB was most commonly performed for pain related to anterior or posterior rib fractures (n=4), that was inadequately controlled with parenteral opioids. SAPB provided complete or near-complete pain relief in these patients. Additionally, SAPB resulted in significant pain relief for acute herpes zoster pain (n=1) and pre-procedural analgesia prior to tube thoracostomy (n=1). Both superficial and deep injection locations resulted in effective analgesia. No adverse events were noted.

Strength & Limitations

This is the first study to demonstrate efficacy of the SAPB for acute herpes zoster pain and procedural pain, and it adds to the growing body of literature supporting the use of SAPB for rib fracture pain.

Limitations of this study include small sample size and lack of systematic data collection. The authors note there is a possibility that physicians may not have documented all side effects. Additionally, patients received non-standardized dosing of parenteral pain medication prior to SABP, therefore underdosing may have exaggerated the impact of the nerve block on pain relief. Generalizability is limited as nerve blocks were performed by ultrasound fellowship-trained emergency physicians.

Authors Conclusion

“SAPB can be an effective analgesic modality for thoracic diseases and injuries including rib fractures, herpes zoster, and thoracostomy placement.”

Our Conclusion

SAPB was an effective adjunct to parenteral opioids in this case series. Though limited, early data suggests that this is a safe and effective procedure. Additional prospective studies are needed to compare SAPB to traditional techniques for the treatment of pain related to acute herpes zoster, thoracostomy, and rib fracture.

The Bottom Line

Serratus anterior plane block, when performed by appropriately-trained physicians, is an effective and safe alternative to parenteral opioids and can provide significant, long-lasting analgesia for a variety of painful thoracic conditions.

For more on the serratus anterior plane block see here:

Highland Ultrasound

Authors

This post was written by Greta Davis, MS4 at UCSD School of Medicine, Charles Murchison, MD and Amir Aminlari MD.

References

Lin J, Hoffman T, Badashova K, Motov S, Haines L. Serratus Anterior Plane Block in the Emergency Department: A Case Series. Clin Prac Cases Emerg Med. 2020 Feb;4(1):21-25.

1. Blanco R, Parras T, McDonnell JG, et al. Serratus plane block: a novel ultrasound-guided thoracic wall nerve block. Anaesthesia. 2013;68:1107-13.

2. Khalil AE, Abdallah NM, Bashandy GM, et al. Ultrasound-guided serratus anterior plane block versus thoracic epidural analgesia for thoracotomy pain. J Cardiothorac Vasc Anesth. 2017;31(1):152-8.

3. Rahimzadeh P, Imani F, Faiz SHR, et al. Impact of the ultrasound-guided serratus anterior plane block on post-mastectomy pain: a randomized clinical study. Turk J Anaesthesiol Reanim. 2018;46(5):388-92.

4. Madabushi R, Tewari S, Gautam SKS, et al. Serratus anterior plane block: a new analgesic technique for post-thoracotomy pain. Pain Physician. 2015;18(3):E421-4.

5. Durant E, Dixon B, Luftig J, et al. Ultrasound-guided serratus plane block for ED rib fracture pain control. Am J Emerg Med. 2017;35(1):197.e3-6.

December 30, 2020May 4, 2021

Erector Spinae Nerve Block for Abdominal Pain – A Case for Better Analgesia

Background

In the age of the opioid epidemic, there is a need for multi-modal pain control techniques, and nerve blocks will likely be an increasingly important piece of the puzzle, particularly in the Emergency Department. Ultrasound-guided nerve blocks for musculoskeletal complaints are now standard practice for many emergency physicians, so it is a reasonable next step to utilize this modality in lieu of opioids for abdominal complaints as well.

The erector spinae plane (ESP) block has been shown to improve pain control for rib fractures in the emergency department, and a more inferior approach has demonstrated success in the perioperative period for abdominal surgeries (1,2). However, this type of block has not been studied for the management of abdominal pain in the emergency department.

This study examined the efficacy of the ESP block on patients with acute appendicitis to see if it could reduce opioid use.

A Novel Technique to Reduce Reliance on Opioids for Analgesia from Acute Appendicitis: The Ultrasound-guided Erector Spinae Plane Block

Clinical Question

Can an inferiorly located, ultrasound-guided erector spinae plane block successfully manage the pain of acute appendicitis in the emergency department setting?

Methods & Study Design

Case report in which ultrasound guidance was used to perform an ESP block at the L1 level.

The patient was a 24-year-old male with uncomplicated appendicitis as diagnosed on CT. The location for needle insertion was identified by palpating the L1 spinous process and placing a linear probe 3 cm lateral, at the transverse process. A Touhy needle was advanced under ultrasound guidance to the level of the transverse process, and saline hydrodissection was used to confirm the needle tip in the fascial plane. Then, 20mL of 1% lidocaine was injected.

Results

Initially, the patient was reporting 7/10 pain following analgesia with 0.5 mg IV hydromorphone, 30 mg IV ketorolac, and 1 g IV acetaminophen. Thirty minutes following placement of the erector spinae plane block, the patient reported 0/10 pain without palpation, and 3/10 pain with deep palpation. Testing to cold revealed loss of sensation between the T10-L2 dermatomes. The patient did not require additional analgesia during the rest of his 5.5-hour emergency department stay.

Strength & Limitations

While this is a case study of only one patient, it provides explicit guidance on performing an erector spinae plane block in the emergency department setting. However, the primary method of assessing pain control is inherently subjective and may be limited by the patient’s perception of the efficacy of the block. Further, the patient had already received analgesia, which may have impacted the efficacy of the block over the course of the ED stay.

Authors Conclusion

“A single injection, ultrasound-guided erector spinae plane block can provide complete analgesia for appendicitis.”

Our Conclusion

Performing an erector spinae plane block at the L1 level was an effective adjunct to opioid analgesia in this case. Because of the relative safety of this block and efficacy in this case, it warrants further investigation as to the ideal level for pain control, particularly in a larger sample of patients.

The Bottom Line

When performed in a more inferior position, an ultrasound-guided erector spinae plane block may be an effective form of analgesia for appendicitis in the emergency department setting.

For excellent guides on how to perform erector spinae blocks see here:

EMRA

Highland Ultrasound

Authors

This post was written by Kaley Waring, MS4 at UCSD School of Medicine, Charles Murchison MD and Amir Aminlari MD.

References

Mantuani et al. A Novel Technique to Reduce Reliance on Opioids for Analgesia from Acute Appendicitis: The Ultrasound-guided Erector Spinae Plane Block. Clin Pract Cases Emerg Med. 2019 Aug; 3(3): 248–251.

1. Luftig J, Mantuani D, Herring AA, et al. Successful emergency pain control for posterior rib fractures with ultrasound-guided erector spinae plane block. Am J Emerg Med. 2018;36(8):1391–6

2. Chin KJ, Adhikary S, Sarwani N, et al. The analgesic efficacy of pre-operative bilateral erector spinae plane (ESP) blocks in patients having ventral hernia repair. Anaesthesia. 2017;72(4):452–60

November 25, 2020May 4, 2021

A Practical Guide to Placing Ultrasound-Guided Peripheral IVs

Background

Peripheral IV placement is one of the most common procedures performed in hospitals, with hundreds of millions performed each year. For the most part, IVs are successfully placed in the traditional way - using landmarks and visualization/palpation of the vessels. But as we all know, there are several patient factors that can make peripheral IV placement more difficult, including obesity, edema, a history of IV drug use, sickle cell disease, lupus, diabetes, etc.

Ultrasound-guided IV placement is increasingly used in the emergency room, medicine floors and ICUs in patients with difficult IV access, but the research is clear that there is a higher premature failure rate with ultrasound-guided IVs (1).

This practical guideline details several considerations that may help reduce the premature failure rate of ultrasound-guided IV catheter placement.

Ultrasound-Guided Peripheral Venous Cannulation in Critically Ill Patients: a Practical Guideline

Clinical Question

What are key concepts to help reduce ultrasound guided peripheral IV catheter complications, prolong life of catheters, and increase rate of successful placement?

Methods & Study Design

• Design

Review paper

Results

There are six key concepts to help minimize complications and increase duration of ultrasound-guided peripheral IV catheter placement.

Strength & Limitations

Potential limits to these guidelines include ultrasound experience level of a person placing IV catheters, whether the necessary equipment is routinely available at lower resource centers, and the setting in which IV cannulation takes place (e.g. trauma or non-trauma). The access and cost of ultra-long peripheral and midline catheters may limit use given potential for high utilization.

Authors Conclusion

“Practitioners should consider several issues when inserting intravenous peripheral catheters under ultrasound guidance, aiming to improve success rate, avoid complications and lengthen the survival of the catheter. Based on available data and everyday practice, all indicate that catheters longer than standard size are needed for US-guided peripheral venous cannulation, with the purpose of minimizing premature catheter failure. This is a call for attention to catheter manufacturers, since a more affordable solution at hand is expected from them shortly.”

Our Conclusion

For placement of ultrasound-guided peripheral IVs consider these rules:

- Always use a long IV catheter, preferably 6 cm or longer
- Choose veins that are:
  - At least 4 mm in diameter
  - At most 1.5 cm deep
  - As distal as possible, preferably distal to the antecubital fossa
- At last 2.75 cm of the catheter should be in the vein
- Check IV placement by flushing saline and use the ultrasound to watch a proximal vessel for turbulent flow

The Bottom Line

When identifying an appropriate vein for ultrasound guided IV access, choose a superficial, patent, large, distal vein to minimize distance needed for the catheter to travel. Ensure adequate catheter length and confirm catheter position after placement to decrease failure rate.

Authors

This post was written by Tori Speck, MS4 at UCSD School of Medicine, Charles Murchison, MD and Amir Aminlari, MD.

References

Blanco, Pablo. “Ultrasound-Guided Peripheral Venous Cannulation in Critically Ill Patients: a Practical Guideline.” The Ultrasound Journal, Springer Milan, 17 Oct. 2019, www.ncbi.nlm.nih.gov/pubmed/31624927.

1. Bahl, Amit, et al. “Ultralong Versus Standard Long Peripheral Intravenous Catheters: A Randomized Controlled Trial of Ultrasonographically Guided Catheter Survival.” Annals of Emergency Medicine, Mosby, 16 Jan. 2020, www.sciencedirect.com/science/article/pii/S0196064419313836.

2. Gottlieb, Michael et al. “Comparison of Short- vs Long-axis Technique for Ultrasound-guided Peripheral Line Placement: A Systematic Review and Meta-analysis.” Cureus vol. 10,5 e2718. 31 May. 2018, doi:10.7759/cureus.2718

3. Presley, Brad. “Ultrasound Guided Intravenous Access.” StatPearls [Internet]., U.S. National Library of Medicine, 31 July 2020, www.ncbi.nlm.nih.gov/books/NBK525988/.

November 18, 2020May 4, 2021

Will Ultrasound Help Your Success with Arterial Lines?

Background

Traditionally, we are taught to place radial artery catheters - A lines - using anatomy and pulse palpation. First-time success rate varies in the literature from as low as 15% to about 70%, with complications including hemorrhage or hematoma. Patients with particularly challenging insertions include small children, as well as adults with hypotension, obesity, or peripheral edema.

Improved procedural success rates, safety and cost effectiveness using ultrasound guidance has been demonstrated extensively in central venous catheterization, however, this has not yet been established for arterial catheterization, as literature for US guided radial artery catheterization has been both limited and presents conflicting results.

Efficacy of ultrasound-guided radial artery catheterization: a systematic review and meta-analysis of randomized controlled trials.

Clinical Question

Is US guidance of radial artery catheterizations effective compared to standard methods of palpation/Doppler in either adult or pediatric patients?

Methods & Study Design

• Design

Systematic review and meta-analysis

• Population

Adult or pediatric patients requiring radial artery catheterization, inclusion criteria varied by study.

• Intervention

Ultrasound-guided radial artery catheterization compared to doppler-assisted or landmark technique.

• Outcomes

First attempt success rate and complications from attempts at radial artery catheterization.

Results

7 RCTs were used to calculate a pooled estimate of first-attempt success

- Rate of first-attempt success in US group: 48.5%
- Rate of first-attempt success in control group: 30.7%
- US-guided radial arterial catheterization was associated with increased first-attempt success (RR 1.55, 95% CI, 1.02 to 2.35, P = 0.04)
- US-guided radial arterial catheterization significantly reduced mean attempts to success (WMD −1.13, 95% CI −1.58 to −0.69, P <0.001), mean time to success (WMD −72.97 seconds, 95% CI −134.41 to −11.52, P = 0.02), and incidence of hematoma (RR 0.17, 95% CI 0.07 to 0.41, P <0.001)

Subgroup Analyses

- No difference in primary outcome between elective insertion (five trials, RR 1.91, 95% CI, 1.45 to 2.53) and emergency insertion (two trials, RR 1.05, 95% CI, 0.38 to 2.83)
- US-guided radial arterial catheterization was associated with significantly increased first-attempt success in small children/infants (RR 1.94, 95% CI, 1.31 to 2.88, P = 0.001)

Strength & Limitations

Strengths:

Well-performed systematic review and meta-analysis with a clear primary outcome and relevant secondary outcomes.

Limitations:

- There were major differences in ultrasound experience of operators, ranging from those without any experience and only an observational training period to expert operators.
- Overall, the studies had small sample sizes and only a small number of studies met inclusion criteria for the review.
- Not enough samples to conduct additional subgroup analyses of patients who might be characterized as difficult-to-insert, including hypotension, obesity, edematous, and pulseless.
- Lack of inclusion of other potential factors including patient pain or patient/operator satisfaction.
- Lack of comment and description on specific US-guidance techniques

Authors Conclusion

"US guidance is an effective and safe technique for radial artery catheterization, even in small children and infants. However, results should be interpreted cautiously due to the heterogeneity among studies."

Our Conclusion

Though data from RCTs is limited, with proper operator training US-guidance can be an effective method of improving radial artery catheterization accuracy, especially in small children/infants with smaller and more difficult-to-palpate anatomy.

Conflicting results in previously conducted RCTs may be attributed to differences in operator training or lack of a proper observational training period and thus careful consideration of the operator should be conducted in future RCTs. A physician who has performed dozens of A-lines using the palpation technique, who is unfamiliar with bedside ultrasonography, is unlikely to benefit significantly from adding this modality to their procedure, while residents who are trained with ultrasounds in their hands will likely benefit more.

Future RCTs should focus on patient populations that have been characterized as difficult-to-insert including hypotension which is in particular significant to emergency medicine, as well as edematous or obese patients.

The Bottom Line

Ultrasound-guided placement of radial artery catheters is effective compared to standard palpation techniques, and should be taught to current Emergency Medicine residents. Further studies are needed to elucidate the effect of US on difficult-to-cath patients, as the effect is hypothesized to be magnified in patients who are hypotensive or edematous.

Authors

This post was written by Jessica Wen, MS4 at UCSD School of Medicine, Charles Murchison, MD and Amir Aminlari, MD.

References

Gu W, Tie H, Zeng X. Efficacy of ultrasound-guided radial artery catheterization: a systematic review and meta-analysis of randomized controlled trials. Critical Care. 2014; 18(3): R93 doi:10.1186/cc13862

October 21, 2020May 4, 2021

Can ED physicians use TAPSE to rule out PE?

Background

Pulmonary embolism (PE) often makes it on the differential of emergency department (ED) patients with any sort of cardiac or pulmonary complaint, and it can be a diagnostic challenge to know how far into the work up of PE is necessary for each patient. Any bedside tool that can increase or decrease the likelihood ratio for PE could be beneficial. Bedside echocardiography is one of the key tools in an ED physicians belt to narrow down differentials or potentially rule out certain diseases.

Research shows that 30 to 70% of emergency department patients with a PE will exhibit signs of right ventricular dysfunction (RVD), and a focused transthoracic cardiac ultrasound (FOCUS) is effective at detecting RVD (1). However, common measures of RVD, such as right heart enlargement, can be challenging to assess and often are dependent on the operator (2,3). A different measure, tricuspid annular plane systolic excursion (TAPSE), has been shown to accurately detect RVD while also providing prognostic information and is the least user dependent measure (4-9).

To date, there is little research on the utility of TAPSE in diagnosing PE, this study aimed to assess the diagnostic characteristics of TAPSE for PE and to optimize the measurement cutoff of TAPSE in diagnosing a PE.

Emergency physician performed tricuspid annular plane systolic excursion in the evaluation of suspected pulmonary embolism

Clinical Question

- How accurate is TAPSE in diagnosing a PE?
- What is the optimal measurement cutoff of TAPSE in diagnosing a PE ?
- How good is the inter-rater reliability of TAPSE
- How good are physicians at visually estimating TAPSE?

Methods & Study Design

• Design

Prospective, observational convenience sample of FOCUS in ED patients undergoing evaluation for suspected PE from April 2015 to April 2016.

• Population

Subjects were eligible if they were 18 years or older and undergoing computed tomographic angiography (CTA) for evaluation of possible PE in the ED. Prisoners, wards of the state, and non–English-speaking patients were excluded.

• Intervention

Patients underwent a FOCUS in the ED either prior to undergoing CTA or the operator was blinded to the results if the FOCUS was done after the CTA. The operators were ultrasound trained emergency physicians, fellow, or residents with one medical student participating who was trained in measuring TAPSE.

• Outcomes

The primary outcome was both describing the diagnostic test characteristics of TAPSE in diagnosing PE and optimizing the measurement cutoff of TAPSE in diagnosing a PE. The secondary outcomes were assessing inter-rater reliability, quantitative visual estimate of TAPSE, and to describe the diagnostic test characteristics of other measures of RVD.

Results

The study found that TAPSE was 72% sensitive and 66% specific when the cutoff was 2.0 cm. When using the pre-established TAPSE cut off of 1.7, TAPSE was 56% sensitive and 79% specific.

They noted that in the sub-group of patients who were either tachycardic or hypotensive, TAPSE became 94% specific and the FOCUS was 100% specific.

Additionally, TAPSE had high inter-rater reliability, physicians were able to qualitatively assess TAPSE as normal or abnormal, and the test characteristics of TAPSE were much more sensitive and specific for a PE than other measures on the FOCUS.

Strength & Limitations

Strengths:

This study was well designed for the question it sought to answer and did a good job limiting bias by blinding the participants. They asked clinically relevant questions.

Limitations:

This study was limited in that it was a convenience sample of patients making it susceptible to selection bias. Additionally, the ultrasound operators in this study had extensive ultrasound training and TAPSE training, thus it may not be generalizable to the standard population of emergency physicians.

Authors Conclusion

"The optimal cutoff for diagnosis of PE using TAPSE was determined to be 2.0 cm. The diagnostic test characteristics of TAPSE for PE are comparable to other measures of RVD, although TAPSE appears to be somewhat more sensitive and less specific. The incorporation of TAPSE into the evaluation of the right heart may increase the accuracy and reliability of beside echocardiography for the detection of PE, although our data suggest that FOCUS is of limited utility in all patients presenting with concern for PE.

However, FOCUS and TAPSE appear to be highly sensitive for PE in patients with tachycardia or hypotension. Additionally, emergency physicians with advanced training in emergency ultrasound are capable of measuring TAPSE with precision comparable to that reported in the cardiology literature. Emergency physicians are able to accurately visually estimate TAPSE as either normal or abnormal, based on an a prior cutoff of 1.7 cm. As a more reliable measure of RVD, TAPSE may also help EPs to determine the severity and prognosis of a patient diagnosed as having a PE."

Our Conclusion

TAPSE is only a moderately sensitive and specific test in diagnosing a PE. However, TAPSE can be a useful tool in patients who are hemodynamically unstable with a suspected PE. In this case, the sensitivity of TAPSE in diagnosing a PE increases dramatically and in the setting of a hemodynamically unstable patient with a normal TAPSE, PE is unlikely the etiology. This can be beneficial if a patient is too unstable to go for a CTA, to help with diagnostic clarification and decision making.

The Bottom Line

TAPSE is not sensitive or specific enough to rule in or rule out PE, but the sensitivity dramatically improves in hemodynamically unstable patients. TAPSE has high inter-rater reliability.

Authors

This post was written by Allie Frankel, MS4 at UCSD School of Medicine, Charles Murchison, MD and Amir Aminlari, MD.

References

Daley J, Grotberg J, Pare J, Medoro A, Liu R, Hall MK, Taylor A, Moore CL. Emergency physician performed tricuspid annular plane systolic excursion in the evaluation of suspected pulmonary embolism. Am J Emerg Med. 2017 Jan;35(1):106-111. doi: 10.1016/j.ajem.2016.10.018. Epub 2016 Oct 11. PMID: 27793505.

1. Matthews JC, Mclaughlin V. Acute Right Ventricular Failure in the Setting of Acute Pulmonary Embolism or Chronic Pulmonary Hypertension: A Detailed Review of the Pathophysiology, Diagnosis, and Management. Curr Cardiol Rev 2008;4:49–59.
2. Pruszczyk P, Goliszek S, Lichodziejewska B, Kostrubiec M, Kurnicka K, Dzikowska- Diduch O, et al. Prognostic value of echocardiography in normotensive patients with acute pulmonary embolism. JACC Cardiovasc Imaging 2014;7(6):553–60.
3. Zanobetti M, Converti C, Conti A, Viviani G, Guerriniti E, Boni V, et al. Prognostic Value of Emergency Physician Performed Echcardiography in Patients with Acute Pulmonary Embolism. West J Emerg Med 2013;14(5):509–17.
4. Kline JA, Steuerwald MT, Marchick MR, Hernandez-Nino J, Rose GA. Prospective evaluation of right ventricular function and functional status 6 months after acute submassive pulmonary embolism: frequency of persistent or subsequent elevation in estimated pulmonary artery pressure. Chest 2009;136(5):1202–10.
5. Jackson RE, Rudoni RR, Hauser AM, Pascual RG, Hussey ME. Prospective evaluation of two-dimensional transthoracic echocardiography in emergency department pa- tients with suspected pulmonary embolism. Acad Emerg Med 2000;7(9):994–8.
6. Rudoni RR, Jackson RE, Godfrey GW, Bonfiglio AX, Hussey ME, Hauser AM. Use of Two-Dimensional Echocardiography for the Diagnosis of Pulmonary Embolus. J Emerg Med 1998;16(1):5–8.
7. Bova C, Greco F, Misuraca G, Serafini O, Crocco F, Greco A, et al. Diagnostic utility of echocardiography in patients with suspected pulmonary embolism. Am J Emerg Med 2003;21(3):180–3.
8. Kopecna D, Briongos S, Castillo H, Moreno C, Recio M, Navas P, et al. Interobserver reliability of echocardiography for prognostication of normotensive patients with pulmonary embolism. Cardiovasc Ultrasound 2014;12:29–38.
9. Taylor RA, Moore CL. Accuracy of emergency physician-performed limited echocar- diography for right ventricular strain. Am J Emerg Med 2014;32(4):371–4.

October 21, 2020May 4, 2021

Identifying regional wall motion abnormalities on ultrasound

Background

Traditionally, the focus of emergency point-of-care echocardiography has been threefold: to assess left ventricular systolic function, to identify the presence of right ventricular enlargement and to evaluate for pericardial effusion. Assessing for regional wall motion abnormalities has been left to formal echocardiography and Cardiology (1). However, structural abnormalities can appear within seconds from the onset of myocardial ischemia (2), so identifying wall motion abnormalities in patients with chest pain or suspected acute coronary syndrome (ACS) in the Emergency Department may be clinically beneficial for emergency providers, leading to more prompt and appropriate diagnostic or therapeutic measures.

We evaluate the following article that looks at whether ED physicians can accurately identify regional wall motion abnormalities.

WAMAMI: emergency physicians can accurately identify wall motion abnormalities in acute myocardial infarction

Clinical Question

Can emergency physicians with basic training in emergency echocardiography accurately identify regional wall motion abnormalities (RWMA) in patients admitted with STEMI?

Methods & Study Design

• Design

Observational report – one group of residents trained and tested in an ultrasound procedure.

• Population

75 patients admitted with STEMI. 6 were excluded from the analysis due to withdrawal, leaving AMA or inability to obtain interpretable images.

• Intervention

Nine residents viewed 2 video instructional modules to provide an introduction to identifying RWMA, and completed an online test evaluating echocardiographic clips for RWMA. They then performed a bedside echocardiogram on patients with known STEMI, though they were blinded to any clinical data about the patient, including the EKG. This was performed within 24 hours of the formal comprehensive echocardiogram.

• Outcomes

The primary outcome was agreement between resident performed echo and formal comprehensive echo on the presence and localization of RWMA.

Results

62% of subjects enrolled had a wall motion abnormality identified by the reference standard. Study investigators identified the presence of RWMA with good sensitivity and specificity (Table 2).

Inter-rater agreement between the point-of-care echocardiogram and the formal echocardiogram for the presence of RWMA was K = 0.79 (95% CI: 0.64–0.94).

Strength & Limitations

Strengths:

Promising results suggest that emergency medicine physicians can be taught to accurately identify RWMA in STEMI with little training. Though the patients in this study were already known to have STEMI on EKG, the application of this procedure may be helpful when patients arrive with NSTEMI or elevated cardiac markers to help in the clinical decision making.

Limitations:

Study was conducted using just 9 residents, and 2 of the residents did the vast majority of the scans. It is possible that these residents are already skilled in ultrasound, so to truly gauge whether this method is broadly teachable, many more residents (with varying levels of baseline ultrasound experience) would need to be evaluated.

Authors Conclusion

The ability to diagnose a RWMA offers emergency clinicians another tool to help manage patients with chest pain and suspected ACS. These data support the introduction of focused training in RWMA identification and expansion of the clinical use of emergency and critical care echocardiography.

Our Conclusion

This is an interesting concept that emergency medicine residents can be trained to successfully identify RWMA using echocardiography. If, and how, this should be implemented in clinical practice is still yet to be explored. Perhaps this could be used in cases of NSTEMI or elevated cardiac markers to help inform clinical decision making, but this study does not answer the question of whether this skill will be clinically useful for ED physicians.

The Bottom Line

It is possible to train emergency medicine physicians to identify regional wall motion abnormalities using echocardiography.

Authors

This post was written by Allison Auchter, MS4 at UCSD School of Medicine, Charles Murchison, MD and Amir Aminlari, MD.

References

P.E. Croft, T.D. Strout, R.M. Kring, et al., WAMAMI: emergency physicians can accurately identify wall motion abnormalities in acute myocardial infarction, American Journal of Emergency Medicine.

1. Cheitlin MD, Armstrong WF, Aurigemma GP, et al. ACC/AHA/ASE 2003 guideline update for the clinical application of echocardiography: summary article: a report of the American College of Cardiology/American Heart Association Task Force on Practice Guidelines (ACC/AHA/ASE Committee to Update the 1997 Guidelines of the Clinical Application of Echocardiography). Circulation 2003;108(9):1146–62.
2. Wholgelernter D, Cleman M, Highman HA, et al. Regional myocardial dysfunction during coronary angioplasty: evaluation by two-dimensional echocardiography and 12 lead electrocardiography. J Am Coll Cardiol 1986;7(6):1245.

October 14, 2020May 4, 2021

How accurate is EPSS in estimating ejection fraction?

Background

Bedside echocardiography has an established role in the time-sensitive assessment for pericardial effusion, relative chamber size, and global cardiac function of emergency department (ED) patients. Most ED physicians use visual estimation to gauge left ventricular ejection fraction (LVEF), a method that may be subject to inter-observer variability and inaccuracy (1). E-point septal separation (EPSS), the minimum separation between the anterior mitral valve leaflet and the interventricular septum, may offer a more objective measure of LVEF.

epss echo

EPSS was first studied in the 1970s as a quantitative, easily measured, and reproducible index of left ventricular function (2). In healthy individuals, the mitral valve leaflet reaches its maximum excursion near or at the septum during early diastole. EPSS increases as left ventricular ejection fraction (LVEF) decreases, and an EPSS of greater than 7mm predicts poor LVEF (3,4).

The gold standard for evaluating LVEF is a quantitative, calculated value obtained from comprehensive transthoracic echocardiography, which is impractical in the emergency department, thus EPSS offers a simple to learn and easy to obtain alternative, requiring only one view in the parasternal long axis. EPSS measurement is a technique feasible for the ED physician to perform at the bedside that can provide a convenient and reliable estimate of LVEF.

E-point septal separation: a bedside tool for emergency physician assessment of left ventricular ejection fraction

Clinical Question

Does EPSS measurements obtained by ED physicians correlate with calculated LVEF from comprehensive transthoracic echocardiography (TTE)?

Can certain EPSS cutoff values be used to predict systolic dysfunction?

What is the relationship between bedside visual estimates of global cardiac function (GCF) and the calculated LVEF measurements?

Methods & Study Design

• Design

This was a prospective observational trial.

• Population

A convenience sample of 80 hospitalized patients undergoing comprehensive TTE for any indication. Subjects were recruited between February and April 2012 from an academic level I trauma center. Exclusion criteria were known pregnancy or age less than 18 years.

• Intervention

Three emergency ultrasound fellows performed bedside 4-view basic echocardiographic examinations consisting of subxiphoid, parasternal long, and parasternal short and apical views and made estimates of GCF. The fellows then obtained separate parasternal long-axis views and performed M-mode measurements of the EPSS. Comprehensive TTE was separately performed by cardiac sonographers and LVEF was calculated via the Teichholz method.

• Outcomes

- Subjective estimates of GCF categorized as normal systolic function (LVEF > 55%), moderate systolic dysfunction (30% > LVEF > 55%), or severe systolic dysfunction (LVEF < 30%)
- EPSS measurements
- Calculated LVEFs also categorized as normal/moderate/severe as above

Results

Calculated LVEF ranged from 13%-86%. EPSS ranged from 0.50-29.70 mm.

Men had higher EPSS scores and higher calculated estimates of LVEF. No other demographic or clinical variables were identified as potential covariates.

The linear regression model revealed that EPSS is a statistically significant predictor (P < .001) of calculated LVEF.

An EPSS measurement of greater than 7 mm was 100% sensitive and 51.6% specific for severely reduced LVEF. An EPSS measurement of greater than 8 mm was 83.3% sensitive and 50.0% specific for any systolic dysfunction.

Estimated GCF and calculated LVEF were in agreement in 49 (69.0%) of subjects with a weighted Cohen κ of 0.58, with strongest agreement for subjects with severe systolic dysfunction.

epss echo

Strength & Limitations

Strengths:

This study is the first to demonstrate that EPSS can provide a quantitative prediction of LVEF. One strength of this study is the generalizability of the findings given that all indications for TTE were included. Another strength is that the ED ultrasound fellows and cardiac sonographers performed their studies independently, unlike a prior study that utilized the same scans performed by residents to obtain both EPSS and LVEF.

Limitations:

There were possible misestimations of EPSS in certain pathologic states, such as overestimation of EPSS in mitral stenosis. Additionally, this paper describes the Teichholz method, which is subject to inaccuracies, especially in states of dyskinesis. Of note, the Teichholz method has since been supplanted by the modified Simpson’s rule and is no longer used clinically. On average, time from EPSS measurement to comprehensive echocardiogram was 6 hours with the possibility that systolic function changed during that window of time. Finally, the study size was fairly small with 71 subjects included in the final analysis.

Authors Conclusion

ED physicians can assess left ventricular systolic function using the EPSS, and EPSS is strongly correlated with calculated LVEF. An EPSS greater than 7 mm may be used to predict patients with severely reduced LVEF. ED physician visual estimation was less effective and less consistent than EPSS measurement for predicting systolic function.

Our Conclusion

We agree that EPSS is a feasible and useful tool for assessing systolic function at the bedside. This study establishes that a 7 mm EPSS cutoff is highly sensitive for detecting severe systolic dysfunction. The clinical utility of an EPSS cutoff of 8 mm for any systolic dysfunction is less clear. Employing EPSS measurement with the 7 mm cutoff in mind, in conjunction with visual estimation by an experienced ED sonographer, is likely to provide a more complete picture of a patient’s systolic function at the bedside prior to obtaining a formal echocardiogram.

The Bottom Line

EPSS measured on bedside ultrasound the ED is an easily obtainable, quantitative predictor of systolic dysfunction. A cutoff of 7mm is sensitive in identifying systolic dysfunction.

Authors

This post was written by Jennie Xu, MS4 at UCSD School of Medicine, Charles Murchison, MD and Amir Aminlari, MD.

References

McKaigney CJ, Krantz MJ, La Rocque CL, Hurst ND, Buchanan MS, Kendall JL. E-point septal separation: a bedside tool for emergency physician assessment of left ventricular ejection fraction. The American Journal of Emergency Medicine. 2014 Jun 1;32(6):493-7.

1. Labovitz AJ, Noble VE, Bierig M, Goldstein SA, Jones R, Kort S, Porter TR, Spencer KT, Tayal VS, Wei K. Focused cardiac ultrasound in the emergent setting: a consensus statement of the American Society of Echocardiography and American College of Emergency Physicians. Journal of the American Society of Echocardiography. 2010 Dec 1;23(12):1225-30.
2. Massie BM, Schiller NB, Ratshin RA, Parmley WW. Mitral-septal separation: new echocardiographic index of left ventricular function. The American journal of cardiology. 1977 Jun 1;39(7):1008-16.
3. Lew W, Henning H, Schelbert H, Karliner JS. Assessment of mitral valve E point-septal separation as an index of left ventricular performance in patients with acute and previous myocardial infarction. The American journal of cardiology. 1978 May 1;41(5):836-45.
4. Massie BM, Schiller NB, Ratshin RA, Parmley WW. Mitral-septal separation: new echocardiographic index of left ventricular function. The American journal of cardiology. 1977 Jun 1;39(7):1008-16.

August 26, 2020May 4, 2021

Can IVC collapsibility predict fluid responsiveness in non-ventilated patients?

Background

Fluid responsiveness is key in guiding the resuscitation of critically ill patients, and both under and over resuscitation can lead to poor clinical outcomes. Vitals and physical exam are not always reliable in determining fluid responsiveness. The search for a quick, easy and accurate diagnostic test to determine fluid responsiveness is ongoing. IVC collapsibility (cIVC) has been proposed as a helpful measure, and in ventilated patients this measurement has been validated. However, spontaneously breathing patients have different physiology, so it is unclear if cIVC is an accurate predictor of fluid responsiveness in this cohort. Previous studies have recommended a cIVC cutoff of 40-42% as a reliable predictor of fluid responsiveness in spontaneously breathing patients (1,2). This study sought to validate those findings.

Inferior vena cava collapsibility detects fluid responsiveness among spontaneously breathing critically-ill patients

Clinical Question

Can the collapsibility of the inferior vena cava differentiate between fluid responders and fluid non-responders in non-ventilated critically ill patients?

Methods & Study Design

• Design

This was a prospective observational trial.

• Population

Inclusion: spontaneously breathing patients with signs of acute circulatory failure in the ED and ICU of 2 academic hospitals in the US.

Exclusion: primary traumatic, cardiogenic, obstructive, or neurogenic shock; age < 18 years old; incarceration; pregnancy; and/or hospitalization for >36 h; NIPPV; if the clinical team felt that they had active pulmonary edema; or that believed that further IVFs might pose a clinical risk.

• Intervention

A NICOM device monitored cardiac index at 1 minute intervals for the duration of the study. Patients had initial cardiac index measurements and IVC videos recorded. Then, after a 3 minute passive leg raise, an additional IVC video was recorded. Lastly, patients received a 500ml normal saline bolus and immediately had a final IVC video recorded. Images were reviewed after the study to determine the cIVC.

• Outcomes

The primary outcome was fluid responsiveness, defined as a ≥ 10% increase in cardiac index.

Results

A cIVC of 25% provided maximum sensitivity (87%) and specificity (81%) in identifying fluid responders. However, as you can see in the figure below, there were several patients with cIVC below 25% who were fluid responders, and several patients with cIVC above 25% who were not fluid responders.

Strength & Limitations

Strengths: The prospective study design reduces bias and confounding factors. Few studies have examined fluid responsiveness in non-ventilated patients, and this adds to the growing body of evidence in this population.

Limitations: This study primarily included patients with severe sepsis/septic shock and DKA/HHS. This limits the generalizability of the findings to other forms of acute circulatory failure. Furthermore, fluid responsiveness was measured once immediately following the bolus. Monitoring the patients’ clinical status over several hours or for the duration of the ICU admission may have provided additional, clinically relevant data regarding fluid resuscitation.

Authors Conclusion

“cIVC, as measured by POCUS, is able to detect fluid responsiveness and may be used to guide IVF resuscitation among spontaneously breathing critically-ill patients.”

Our Conclusion

In spontaneously breathing patients with distributive shock, cIVC can be a useful tool in identifying fluid responsiveness, with the caveat that a minority of patients with minimal IVC collapsibility may still be fluid responders and those with significant IVC collapsibility may not be fluid responders. There is certainly a trend toward a collapsible IVC identifying fluid responders, but the outliers in this study should be taken into account. IVC, along with history, exam and bedside echo, can be used to identify which patients may need more IV fluid resuscitation.

The Bottom Line

IVC collapsibility >25% predicts fluid responsiveness in spontaneously breathing patients with distributive shock most of the time, but should not be solely relied upon.

Authors

This post was written by Aaser Ali, MS4 at UCSD School of Medicine, Charles Murchison, MD and Amir Aminlari, MD.

References

Corl KA, George NR, Romanoff J, et al. Inferior vena cava collapsibility detects fluid responsiveness among spontaneously breathing critically-ill patients. J Crit Care. 2017;41:130-137.
Machare-Delgado E, Decaro M, Marik PE. Inferior vena cava variation compared to
pulse contour analysis as predictors of fluid responsiveness: a prospective cohort
study. Intensive Care Med 2011;26(2):116–24.
Muller L, Bobbia X, Toumi M, et al. Respiratory variations of inferior vena cava diam-
eter to predict fluid responsiveness in spontaneously breathing patients with acute
circulatory failure: need for a cautious use. Crit Care 2012;16(5):R188.