Most Recent Articles 3/30/20
Please take a listen to this 20 min podcast from Phillipe Rola - Intensivist out of Montreal and Cameron Kyle-Sidell, EM-Intensivist out of NY discussing some of the bizarre, yet uniform features of severe hypoxemia seen in COVID19. Their discussion is certainly consistent with what we have been seeing at our hospitals.
Why do many of these patients present with hypoxemia, but often without tachypnea, dyspnea, or distress?
Why do they experience SEVERE desaturations during intubation (down to single digits) without compensatory tachycardia, reflex bradycardia or cardiac arrest?
They compare clinical features of COVID19 to Pulmonary decompression sickness (the Bends).
They differentiate some features of COVID19 from ARDS which appear to be two different clinical conditions. Suspected that COVID19 is some combination of alveolar/capillary destruction, pulmonary hypertension and some unknown hemoglobinopathy.
Discussion re: timing of intubation, use of NIV and HFNC
Butterfly Network COVID19 Page (Focused on Ultrasound)
Full article found on the button below (104 pages)
Important Notes we noticed
surgical mask okay if on vent from SSC perspective (unless doing an AGP)
perform AGPs in a negative pressure room if possible
LRTI samples considered higher yield; if intubated use endotracheal aspirate (considered lower risk of aerosolization); if not intubated still do nasopharyngeal swab to minimize bronchoscopies
conservative fluid strategy as opposed to liberal (due to risk of ARDS)
Buffered balanced crystalloids recommended over unbalanced or colloids
vasopressors similar to normal
HFNC recommended? (contradicts other guidelines; pulm leaders discussing)
early intubation
ARDSnet vent strategy; higher PEEP table recommended
in mod-severe ARDS proning recommended
boluses of paralytics if needed and continues if vent pressures or dyssynchrony are issues
-podcast and website from Pulmcrit. Basics of COVID19. Pretty comprehensive. Great starting point if your wanting to learn more.
signs & symptoms
COVID-19 may cause constitutional symptoms, upper respiratory symptoms, lower respiratory symptoms, and, less commonly, gastrointestinal symptoms. Most patients will present with constitutional symptoms and lower respiratory symptoms (e.g. fever and cough).
Fever:
The frequency of fever is variable between studies (ranging from 43% to 98% as shown in the table above). This may relate to exact methodology used in various studies, different levels of illness severity between various cohorts, or different strains of the virus present in various locations. Additionally, some studies defined fever as a temperature >37.3 C (Zhou et al. 3/9/20).
Regardless of the exact numbers – absence of a fever does not exclude COVID-19.
Gastrointestinal presentations: up to 10% of patients can present initially with gastrointestinal symptoms (e.g. diarrhea, nausea), which precede the development of fever and dyspnea (Wang et al. 2/7/20).
“Silent hypoxemia” – some patients may develop hypoxemia and respiratory failure without dyspnea (especially elderly)(Xie et al. 2020).
Physical examination is generally nonspecific. About 2% of patients may have pharyngitis or tonsil enlargement (Guan et al 2/28).
typical disease course
Incubation is a median of ~4 days (interquartile range of 2-7 days), with a range up to 14 days (Carlos del Rio 2/28).
Typical evolution of severe disease (based on analysis of multiple studies by Arnold Forest)
Dyspnea ~ 6 days post exposure.
Admission after ~8 days post exposure.
ICU admission/intubation after ~10 days post exposure. However, this timing may be variable (some patients are stable for several days after admission, but subsequently deteriorate rapidly).
Labs
complete blood count
WBC count tends to be normal.
Lymphopenia is common, seen in ~80% of patients (Guan et al 2/28, Yang et al 2/21).
Mild thrombocytopenia is common (but platelets are rarely <100). Lower platelet count is a poor prognostic sign (Ruan et al 3/3).
coagulation studies
Coagulation labs are generally fairly normal upon admission, although elevated D-dimer is commonly seen (table above).
Disseminated intravascular coagulation may evolve over time, correlating with poor prognosis (figure below)(Tang et al. 2020).
Procalcitonin
COVID-19 does not appear to increase the procalcitonin. For example, the largest series found that procalcitonin levels were <0.5 in 95% of patients (Guan et al 2/28).
Elevated procalcitonin may suggest an alternative diagnosis (e.g. pure bacterial pneumonia). For patients who have been admitted with COVID-19, procalcitonin elevation may suggest a superimposed bacterial infection.
C-reactive protein (CRP)
COVID-19 increases CRP. This seems to track with disease severity and prognosis. In a patient with severe respiratory failure and a normal CRP, consider non-COVID etiologies (such as heart failure).
Young et al. 3/3 found low CRP levels in patients not requiring oxygen (mean 11 mg/L, interquartile range 1-20 mg/L) compared to patients who became hypoxemic (mean 66 mg/L, interquartile range 48-98 mg/L).
Ruan et al 3/3 found CRP levels to track with mortality risk (surviving patients had a median CRP of ~40 mg/L with an interquartile range of ~10-60 mg/L, whereas patients who died had a median of 125 mg/L with an interquartile range of ~60-160 mg/L)(figure below in the section on prognosis).
Testing
specimens
(1) Nasopharyngeal swab should be sent.(2) If intubated, tracheal aspirate should be performed.(3) Bronchoalveolar lavage or induced sputum are other options for a patient who isn't intubated. However, obtaining these specimens may pose substantial risk of transmission.It's dubious whether these tests are beneficial if done for the sole purpose of evaluating for coronavirus (see the section below on bronchoscopy).
Bronchoscopy (Should we doing it?)
Risks of bronchoscopy:
May cause some deterioration in clinical condition (due to instillation of saline and sedation).
Enormous risk of transmission to providers.
Considerable resource allocation (requires N95 respirators, physicians, respiratory therapists) – all resources which will be in slim supply during an epidemic.
Benefits of bronchoscopy:
Benefit of diagnosing COVID-19 is dubious at this point (given that treatment is primarily supportive).
Bottom line on bronchoscopy?
Bronchoscopy might be considered in situations where it would otherwise be performed (e.g. patient with immunosuppression with concerns for Pneumocystis pneumonia or fungal pneumonia).
Bronchoscopy should not be done for the purpose of ruling COVID-19 in or out (as this entails risk with no definite benefits)(Bouadma et al.).
Youtube Style Easier Explanation Videos
Airway Mgmt (see more on pulmcast covid airway page)
Airway
Emcrit Podcast Episodes
COVID19 Airway Management
Additional thoughts on Airway Mgmt