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POCUS Screening in COVID-19

"Sit down before a fact as a little child, be prepared to give up every preconceived notion. Follow humbly wherever and to whatever abysses nature leads, or you shall learn nothing."

Professor Thomas Huxley, 1876

On February 16th, 2020 there were 56,312 new cases of COVID-19 diagnosed in the US. This signifies an 80% drop since our peak of 295,121 cases according to the Covid Tracking Project. For unclear reasons - growing herd immunity, seasonality, vaccinations, poorly understood viral behavior - maybe we are seeing the beginning of the end. With variants and vaccine delivery headaches and hiccups, COVID-19 is sure to be with us in some capacity for the coming months to years. Through the explosion of strong opinions, wrong predictions, questionable guidance, and enormous bodies of research from all over the world, we have learned a lot. Rarely mentioned in this public discussion is point of care ultrasound (POCUS) and the tremendous opportunity it offers for expediting and improving care of COVID-19 patients (and all patients!) going forward.

Understanding Disease Pathophysiology & Incidence

Before getting to POCUS, we must first review what we now know about COVID-19 pathophysiology to better understand how POCUS may help. Watching the news in March of 2020, seeing the daily case counts and insanely sad stories, it was hard not to be afraid. Then going into to work on what could only be analogous with the pre-antibiotic-era experience, seeing the real patients up close on the COVID wards as they linger on absurd amounts of oxygen as we hoped they improve was disconcerting to say the least. At the time we had no treatments, no idea how infectious it was, no confidence that we had enough protective equipment, and no guarantee that we would be safe at our job.

Now 1 year later, we have some treatments, 2+ vaccines, COVID19 sniffing dogs, a much better understanding of how SARS-CoV2 affects humans, and mountains of studies that will take years to fully understand.

We now know that risk is DRAMATICALLY affected by age. As researchers in December 2020 explain, there is "an exponential relationship between age and IFR for COVID-19. The estimated age-specific IFR is very low for children and younger adults (e.g., 0.002% at age 10 and 0.01% at age 25) but increases progressively to 0.4% at age 55, 1.4% at age 65, 4.6% at age 75, and 15% at age 85."

Therefore if 100,000 kids are infected with SARS-COV2, two will die. At a startling contrast to this, if 100,000 85 year olds are infected 15,000 will die, about a 7,500X increased risk.

For a 25 year old, it is about 1 in 10,000, for 55 year olds it hikes to 4 in 1,000. These numbers improve when you exclude enclosed, low resource settings such as nursing homes and prisons, as was seen in a study in Indiana. Using a stratified random sample of antibodies from Indiana residents taken in in April 2020 (excluding nursing home residents and those incarcerated), the overall IFR was estimated at 0.26%. People under 40 years old was similar to the previous study at 0.01%, and over 60 reduced to 1.71%.

Blackburn et al 2021

Now when you have an outbreak of over 27 million cases in the U.S., these amount to large numbers, especially in the over 50 population. There have been multiple seroprevalence studies that support these numbers, and a paper in Nature found a similar IFR of 0.001% for those aged 5-9, and improved IFR of 8.29% for those ages 80 or over. They estimate a mean increase of 0.59% in IFR for each 5-year increase of age.

We also now know from the largest study of medicare patients with COVID-19, out of 543,000 infections and 38,000 deaths, the biggest risk factors for dying from COVID-19 are: are 85 year old or older, male sex, and patients with sickle cell disease, chronic kidney disease, leukemia or lymphoma, heart failure and diabetes.

Of course, this does not include the morbidity that may be associated with the disease (not an inclusive list):

  • Anosmia (loss of smell) in 33-68% of cases, mostly in women. Symptoms last about 9 days and recovers 98% of the time

  • Long-COVID phenomenon - still poorly understood. But some estimates from UK suggest 10% of patients having symptoms 3 weeks out. Fatigue and SOB have been seen as far as 6 months out in hospitalized patients, however it is hard to say if this is due to SARS-CoV2 specifically, or just the fact that they are hospitalized with a respiratory illness, as there were similar reports from SARS in 2010.

  • Pulmonary fibrosis in severe COVID-19 infections seen in 10-30% on follow up CT scans in recovered patients from China, however this is true of any severe pneumonia.

  • Myocarditis was a big concern early on. No large studies we've seen have estimated incidence of myocarditis or pericarditis in patients infected with SARS-CoV2. A study of 100 recovered patients in Germany showed cardiac abnormalities on cardiac MRI in about 2/3 of patients, however in an examination of 277 autopsies of COVID-19 patients, there was only evidence of myocarditis in less than 2% of patients. This is consistent with a study of 60 athletes with COVID-19 compared to 60 controls that showed evidence of myocarditis on cardiac MRI in only 3% of athletes, which may be on par with coxsackievirus infections, for example, and incidence of myocarditis around 2%.

  • Multisystem Inflammatory Syndrome in Children (MIS-C) - According to the American Academy of Pediatrics, as of February 11th, 2021, 3,033,370 children were infected with SARS-CoV2, and as of February 8th, 2021, the CDC reports a total of 2,060 cases of MIS-C, which is 0.06% of all infected. MIS-C can be devastating for a young child and has long term complications, so fortunately it has turned out to be extremely rare.

  • For pregnant women there appears to be a 1.6x increased risk of ICU admission, a 1.8x increased risk of needing a ventilator, and about a 3x increased risk of pre-term birth with a SARS-CoV2 infection

  • Increased risk of deep vein thrombosis and pulmonary embolus, especially in ICU patients (more on that shortly).

Knowing these numbers, it makes sense to heavily prioritize resources and vaccines to the elderly. In addition it probably makes sense to encourage N95 masks for those at highest risk (or for all crowded public areas), keep them in separate rooms when possible, and perform frequent screening tests, but this is out of the scope of this post.

Better Screening for Shortness of Breath

Shortness of breath is one of the most common presentations to the hospital and reasons for admission during the pandemic. It is also one of the most gratifying symptoms to apply POCUS to, since you can accurately diagnose, or at least definitively rule out likely causes in most cases. Something that cannot be said for the stethoscope.

With the earliest reports coming out of China regarding characteristic lung ultrasound (LUS) findings in COVID-19, we learned that peripheral, patchy focal B-lines are commonly seen in COVID-19 pneumonias. These findings are neither sensitive or specific to COVID-19, however in the right clinical context (i.e. a global pandemic ripping through the population and overwhelming hospitals), in patients presenting with shortness of breath with patchy B-lines, COVID-19 is the likely diagnosis. This screening test takes a couple minutes and can triage patients prior to diagnosis. This method will not discover infections that aren't involving the lung parenchyma, so this is a complementary triage method to antigen and PCR testing. We've had multiple anecdotal experiences where a patient was PCR negative however had classic symptoms and patchy areas of B-lines seen on POCUS, and PCR test was repeated and returned positive.

Above is an example of a focal B-line pattern seen in a patient with COVID-19 pneumonia. In addition to the spotlight projections, the pleural line is often jagged and irregular.

LUS is more accurate than chest x-ray in diagnosing lung pathology and likely more sensitive than chest x-ray in detecting COVID-19. In a study of 43 patients who presented to the ED during the peak pandemic, focal B-lines were 89% sensitive for detecting patients who were shortly after confirmed to be PCR-positive, compared to only 50% with chest x-ray.

Focal irregularities seen in COVID-19 Pneumonia

As we've discussed before, there are many clinical scenarios in which POCUS may provide additional benefit over a stethoscope, and COVID-19 pneumonia is definitely one of them.

DVT Screening

While the Chest guidelines do not formally recommend DVT screening for all COVID-19 patients, we feel strongly that it can make a huge difference in the management of patients infected with SARS-CoV2 due the thrombotic nature of the disease, the increased incidence of venous thromboembolism (VTE) and the ability of POCUS to quickly rule in or out a DVT.

In an early study of 48 ICU patients in China, a striking 85% had distal or proximal DVT despite prophylactic anticoagulation. Another multi-center ICU study found that among 150 ICU patients, 64 had clinically relevant thrombotic complications, 16% of which were pulmonary emboli. In the Netherlands, a study of ICU and hospital ward patients found that DVT incidence in COVID-19 patients was 20%, despite chemical DVT prophylaxis. The majority of these were ICU patients, however 5.8% of patients on the wards also had DVT, compared to normal hospital rates of about 1.7% with Lovenox prophylaxis. A meta-analysis of DVT and PE studies in ICU and wards also found increased incidence of DVT despite anticoagulation in COVID-19 patients. "Overall, approximately 24% developed VTE (12% developed PE and 12% developed DVT) despite anticoagulation with at least prophylactic dosing. The risks of VTE and PE were both higher in the ICU setting (30% and 16%) than in the ward setting (13% and 6%). In contrast, the risk of DVT was similar in the two settings."

Meta-analysis from Chi et al on DVT/PE Risk

With this increased risk of DVT, at least one expedited screening of the lower extremities should be considered as standard of care for COVID patients.

In a sub study of the PREVENT trial (Pneumatic Compression for Preventing Venous Thromboembolism) comparing pneumatic compression to Lovenox in ICU patients, they compared twice weekly lower extremity dopplers in one group of patients to the control group with no surveilance. Researchers found that in the group getting twice weekly surveillance dopplers, DVT was diagnosed 16 days earlier and pulmonary emboli were diagnosed earlier at 4 days, compared to 7.5 days in the control group. There was a slight significant benefit of 90 day mortality, however this was not a strong effect.

Popliteal vein DVT seen on bedside POCUS compression exam. Note the lack of collapse of the popliteal vein (on top of the smaller popliteal artery) with tissue compression. For more on how to perform DVT exam go here.

Using well documented simplified protocols, clinicians can perform a 100% sensitive and 96% specific DVT exam in under 2 minutes, as was shown in the brilliantly acronym-ed HOCUS-POCUS study looking at Hospitalist-performed compression of only three spots: common femoral vein, superficial femoral vein and popliteal vein.These impressive findings were confirmed in multiple other studies with emergency room physicians, suggesting that with an ultrasound probe and 30 seconds per leg, you can diagnose or rule out DVT with superb accuracy. This would dramatically change management in COVID-19 patients with VTE, triggering therapeutic anticoagulation early on.

No POCUS leads to delays in care

Using basic POCUS protocols to evaluate lungs and legs, with about 3-4 minutes of extra exposure we can get a much earlier, more precise diagnosis. Patients presumed to have COVID-19 are isolated and tested with PCR, usually in the Emergency department. However this takes at least 24 hours for results and delays other important studies that may be needed to come up with the diagnosis, like echocardiograms or radiology performed lower extremity dopplers.

These studies are often postponed until the COVID-19 test returns if they are deemed non-urgent, and can delay care up to 48 hours. Two days worth of delay that may not be a luxury these patients have. A patient with new systolic heart failure for example, may go 48 hours before receiving appropriate care if they were presumed to have COVID-19 and no one performed a focused cardiac/lung/leg POCUS exam. The chest x-rays are often not sensitive or specific enough to see small pleural effusions or differentiate focal B-lines from diffuse B-lines seen in pulmonary edema.

So should POCUS be included in COVID-19 care of hospitalized patients?

Of course we think so, but maybe we are biased.

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