By: The Project Smackdown Team
Hi and welcome to Absite Smackdown.
Today on the podcast we're going to discuss the Coronavirus.
There's some key things to know about the Coronavirus that, even as surgeons, we're going to run into when we go to decide when to restart our elective cases.
It sure does help to know a little bit about this virus that has impacted us so much. So first let's talk about the biology...
Coronavirus is a 30 kilobase pair, single stranded RNA, enveloped virus.
We think it may be zoonotic. Whether it came from a bat or something else we're not sure, but...it came to people. And of course there are all these other theories about it originating in a lab.
What we do know is that it spreads primarily person to person and it can be spread by asymptomatic carriers. The asymptomatic phase is really pretty lengthy for this condition.
Viral particles enter the lungs via droplets. The WHO and CDC both recommend airborne precautions / airborne isolation techniques. There's a viral S spike that binds to ACE2 on type two pneumocytes. So that's one of the key portals of entry: type two pneumocytes.
The effects of ACE / ARB meds are unclear and it's generally not recommended to change medications out if a patient is on that. So ACE inhibitors and ARBs, angiotensin receptor blockers--we're not exactly sure about how or whether that affects things. And, currently there doesn't seem to be any strong recommendation to change meds at this time.
Now there are other portals of infection and lately there's been some evidence that infection can even occur via an ocular route. These are possible, but we're not sure just how significant these are in terms of means of spread.
Now in terms of epidemiology, the attack rate in China was substantial, 30 to 40%.
The R sub zero was approximately two to four, depending on which case series you read.
The case fatality rate was approximately 2.3%, again in China, and the incubation time was approximately three to 15 days. So you can have an asymptomatic carrier for up to two weeks. And that's part of the concern about this particular condition. And in part why it spreads.
So viral shedding has a median of about 20 days max of 37 days. And in our practice we've seen many patients come through who are PCR negative and we'll get to the PCR testing in a bit, but who are PCR negative who don't seem to be shedding COVID virus, but in fact you have obvious signs, obvious stigmata of having had the condition.
Next, let's break down disease severity. So epidemiology here is fairly clear, but 80% of the time it's not severe. It's just a mild pneumonia. About 15% of the time it is severe and there's hypoxia and respiratory distress and about 5% of the time the patient is critical.
And there are places where we see the disease cluster like our skilled nursing facilities, cruise ships, conferences...anywhere people come together in large groups. And there are several epidemiologic levels of prevention of transmission, including hand-washing, social distancing and quarantining.
You may have seen this social media #flattenthecurve and that's where we try to take the same area under the curve but distribute it over a longer time.
So there's the same area under the curve where that curve is a plot of time from onset of outbreak to number of hospitalized patients. And the goal is to make that curve even if it has the same area just flatter. And the reason being is not to exceed capacity for hospitals in terms of clinical presentation.
We see several symptoms recurrently. Those include cough, fever, dyspnea, and those are symptoms that are typically seen across the US. We've seen in our practice that about 50 to 80% have a cough, about 45% are febrile on presentation. Overall, it seems like more are febrile at some point during the illness up to about 85%. Twenty to 40% have dyspnea, 15% have upper respiratory symptoms and 10% have GI symptoms.
They are also key lab findings that we see which individually are not necessarily specific but can give you a good hint that this is COVID virus. And on CBC those include leukopenia. So a low white blood cell count and also lymphopenia, about 80% of patients or so tend to have that lymphopenia. On BMP there's an increased bun to creatinine ratio.
LFTs demonstrate increased transaminase values. So transaminitis, AST and ALT are increased and bilirubin is often increased. D-dimer is increased. C reactive protein is increased, LDH is increased, and ferritin is increased.
Typically procalcitonin is low, but it can also be high if there's an overlying infection such as a bacterial infection superimposed on significant viral disease. So the bottom line is, although the labs aren't specific, that's kind of the typical constellation we see with COVID virus.
Now, regarding imaging in COVID: it's not diagnostic. In fact, about 17% of patients who have COVID virus by PCR actually have a negative chest CT on presentation. The chest x-ray may demonstrate hazy bilateral infiltrates with peripheral opacities and CT of the chest demonstrates ground glass opacities.
And there are many other terms given to the findings around these COVID related areas, like a halo sign, crazy paving, consolidation, et cetera.
So the bottom line here is that CT is often not diagnostic.
Isolation is one strategy for these patients. Some people argue that this is a really great role for telemedicine and that we should be treating these patients via phone call.
Others include placing the patient in a mask, in a single room and limiting / restricting visitors. Also moving ventilator controls and IV pumps outside the room if at all possible is a good move. That allows us to conserve personal protective equipment, save time, and reduce exposure.
Note that there's airborne precautions for aerosolizing procedures like intubation or people who are on a positive pressure ventilation that's noninvasive, you know, BiPAP or CPAP and also droplet precautions for everything else.
So we think that improvised cloth masks are likely ineffective. Remember N 95 masks have to be fit tested. Also, we should be wearing eye protection. PPE should be donned and doffed with a trained observer--someone to watch to make sure we're doing it kind of in that right sequence.
For hand hygiene, there are lots of recommendations floating around. We do think that 20 seconds with soap and water is likely effective, but there are other options as well, including alcohol containing hand gel. Although there's some disagreement about what is most effective, whether that's a soap and water or alcohol based prep.
In terms of treatment, probably one of the key things is to isolate patients who are suspected of having COVID virus. Another key is testing with PCR early. There should be a triage discussion amongst either a healthcare team, or the group doing triage.
It's typically recommended to do a fluid sparing resuscitation. Again, this is a primary pulmonary disease with most issues that seem to put the patient in danger related to the lung sequelae. For that reason, although fluid resuscitation is important, it should really be done judiciously. So the lungs don't become worse with over fluid resuscitation.
Antibiotics may have a role and there's some staff who do start empiric antibiotics, and there are some who do not.
The recommendation is to intubate early under controlled conditions, with rapid sequence intubation, no bagging, have suction and capnography available and be prepared to have a plan B.
So many advocate early intubation, and some say to avoid noninvasive positive pressure ventilation unless an individualized reason exists. And if that does happen, consider helmet mask, and avoid things like nebulizers and bronchoscopy unless they're really necessary for that patient.
Remember to utilize mechanical ventilation strategies similar to patients with ARDS. The critically ill COVID patients typically do manifest very low PF ratios. If they're sick enough to come to intubation, you would basically use a lung protective protocol.
Make sure there's the ability to use a pressure regulated mode like APRV or bivent, whatever you call it, depending on the vent you have or somehow otherwise a lung protective strategy.
Inhaled prostacyclins have a role as do both proning and paralytics in less typical circumstances. These may become necessary. And there may be a role for ECMO.
Again, if there's a challenge improving the PF ratio and if there's a challenge oxygenating with maximal settings consider ECMO.
Consider screening for cardiomyopathy. Point of care ultrasound can help with this and it may be part of your imaging routine. Cardiomyopathy is a sequellum that is seen at times.
And there are certain investigational therapies going on via clinical trials that the CDC is putting out there. There are different drugs which are used at different centers. We're not sure how well they work.
Remdesivir is not approved but some believe it may be useful.
Chloroquine and hydroxychloroquine: may have a role but that's very controversial.
Remember there's a QT interval issue that may occur there.
Tocilizumab is available. That's investigational, mostly for patients in shock.
Lopinavir and retonovir are available. However, this just in...there've been some negative randomized clinical data.
Oseltamivir: we're not sure about that one either.
Corticosteroids are typically not recommended. They may be given to patients with significant, late stage ARDS type pictures. But again, these are often not recommended for most patients.
Prognosis? It's useful when a patient comes in to have a sense of prognosis and age. And comorbidities are key here. Patients who are older do tend to have higher morbidity and mortality from this condition and, partly, associated co-morbidities drive that.
There are certain comorbidities that seem to up mortality risk like diabetes, chronic obstructive pulmonary disease, hypertension, cerebrovascular disease and cancer.
And whether that's true, true and unrelated or an independent risk factor it's hard to tell. The literature is currently kind of teasing that out, but those are markers. Whether it's for patients who are just more sick overall or whether they drive it independently we just don't know. It seems like those really do help prognose worsening outcome.
Also an admission SOFA score predicts mortality fairly well.
There's a high mortality in intubated patients with comorbidities. It can be as high as 50 to 80%. I would not take that necessarily as a reason not to intubate. Again, that may mean those patients need earlier and more aggressive care and they are at high risk. But I wouldn't read backwards on that and say that somehow intubation causes that. It just is a lesson that if they're sick enough to require intubation, they typically have a significant potential for mortality.
Other lab findings predict mortality like an increased D-dimer, troponin, cardiac myoglobin, ferritin, and there's some thought that COVID really does somehow yield a hypercoagulable state driving that D-dimer.
So another consideration is screening for PE, even if there's chemoprophylaxis on board and the SCDs, et cetera. Should the patient have a symptom consistent with that and if they can travel around the hospital, just keep in mind PEs do happen in these patients. And we think it may be due to a hypercoagulable effect from COVID.
In general, do expect prolonged mechanical ventilation if it becomes necessary. And of course there are complications related to that. Like hospital acquired pneumonia and ventilator associated pneumonias.
Remember cardiomyopathy has a pretty significant incidence in these people and there's about a 33% risk.
So the headlines here are that COVID is a disease that we are tracking and improving our understanding of every day. As one of the people who treats COVID, I'll share with you that many things are not ironed out, but the overall takeaway is that a lung supportive approach, a regimen where we use lung protective strategies, is probably the mainstay.
Again, be careful with fluid resuscitation. You can over-resuscitate these patients who have really pulmonary sequellae as the driving reason for them to be sick.
So, again, although fluid resuscitation is important, just keep in mind: do it judiciously.
As far as medications, we're not really sure which if any have a an effect on improving or shortening the course of disease. But there are lots of candidates and we listed some of those here.
So the bottom line is I hope you enjoy and find useful this podcast on some of what's currently known about COVID.
Again, this is an academic review. I don't make any specific therapeutic recommendations and of course I'm not making any that apply directly (or easily) to your patient.
But from the standpoint of understanding what we currently know about the virus and what may come up in your practice and on the ABSITE, the #ProjectSmackdown team just wanted to share with you some of the current thinking so you have it for your drive to work or when you have downtime.
Best of luck taking care of these interesting patients!