COVID-19 What Next
WORLDWIDE
WORLDWIDE CASES
WORLDWIDE DEATHS
CANADA
BRITISH COLUMBIA
VANCOUVER ISLAND • 117 total patients testing positive • 4 deaths • Assuming a mortality of 1%, approximately 400 people on VI have had COVID-19 • 400/850,000 = 0.05% of the population has had COVID and 70% have likely resolved • This contrast with New York or Northern Italy where up to 20% of people have had COVID- 19 • Everything points to a low prevalence on VI which is likely still falling; • Fewer positive tests • Fewer new hospital admissions • Few deaths
CLINICAL ISSUES
ASYMPTOMATIC TRANSMISSION • It is now clear that patients are infectious without having symptoms. • Pre-symptomatic • Minimally symptomatic • Truly asymptomatic • Pre symptomatic • Many patients are infectious and test positive 1-3 days before symptoms
ASYMPTOMATIC TRANSMISSION • Washington State Nursing Home know to have COVID-19 patients • Point prevalence study swabbed 76 patients and 48 were positive • 27 of the positives were asymptomatic at the time and 24 had developed symptoms at 7 days. • China: Recently reported that 80% of patients who tested positive at airports coming into China were asymptomatic. • Half of 700 US sailors who tested positive on a aircraft carrier were asymptomatic. • Asymptomatic transmission is the biggest reason why COVID-19 is so contagious and why it is so difficult to control – wholesale lockdown is required to slow spread instead of quarantining symptomatic patients only. • Up to half of cases are likely due to asymptomatic transmission.
ANTIBODY STUDIES • Antibody studies will be useful in many ways but they are not without problems; • Difficult to know if coronavirus antibodies are due to COVID-19 or to the other 4 coronaviruses that cause seasonal URTIs • Antibodies to many different antigens are being studied. We don’t know yet which ones confer immunity (which are neutralizing antibodies). • They can help determine the true infection and death rate. • In NYC, 3000 grocery shoppers were randomly selected for antibody tests and 20% were positive. • Slightly less were positive in other places in the State. • This information was used to estimate that 15% of all people in NY State at one point had COVID-19. • And using this number in the denominator to calculate the death rate revealed that the true case fatality rate would have been 0.8% and not 7.6% which is the figure if the number of swab positive patients is used for the denominator. • More recent data suggests 25% infection rate in NYC and a 0.5% mortality rate. This means the virus is very infectious.
IMMUNITY • It is not know how much immunity results from an infection • Antibodies have been found but it is unknown if they lead to immunity and if they do, how long it will last • It is know that the 4 seasonal coronavirus viruses do not impart long term immunity • There are cases in China and Korea where patients have been cleared of their infection and then get sick again and test positive again. It is not know if this is a new infection or reactivation of the virus. • Vaccine; • If an infection does not lead to immunity then a vaccine may be difficult to produce. • If convalescent plasma studies do not show benefit the vaccines may be problematic. • There are animal coronaviruses for which there are effective vaccines – Canine coronavirus vaccines are effective.
UPDATES IN MANAGEMENT
RESPIRATORY FAILURE • This is a unique disease in that patients often present as the “Happy Hypoxic” • Some have severe hypoxia (Sp02 in the 70s or low 80s) without feeling short of breath. This is not how conventional ARDS presents. • Gattinoni; Describes 2 phenotypes • L Type • Normal lung compliance and normal lung volumes - Interstitial edema • Vasoplegia leads severe hypoxia since hypoxic pulmonary vasoconstriction is reduced. • Patients are tachypneic and have large tidal volumes but because their lungs are not stiff they do not feel short of breath. • Lung is not recruitable and they are unresponsive to PEEP • H Type • More like conventional ARDS. • Reduced lung volumes and low lung compliance • PEEP and prone ventilation responsive • Present with dyspnea and increased WOB
RESPIRATORY FAILURE • Progression of L to H • The difference in types may be due to the severity of the lung injury or to the duration of the disease – in time L may progress to H as the lung injury worsens. • L may progress to H because of Self Induced Lung Injury P-SILI. The high respiratory drive due to hypoxia can lead to large tidal volumes and the generation of very negative intrapleural pressures that increase transpulmonary pressures .and precipitate P-SILI • Management of L T ype • Correct hypoxia with HFNO, NIV or CPAP . • Target SpO2 > 90% • Watch to ensure that the patient is not at risk of P-SILI • Intubate only if the patients has increased work of breathing • If ventilated use 8 ml/kg of TV and limit PEEP to 8-10
RESPIRATORY FAILURE • Management of H Type • Similar to management of conventional ARDS • Management • Lung protective ventilation with TV 6 ml/kg • Driving pressure < 15 • Pplat < 30 • Higher PEEP • Prone ventilation
TIMING OF INTUBATION • China • Intubate early (patient on 6 L/min of oxygen) • Prevents P-SILI and crash intubations which risk HCW contamination • Italy • An overwhelmed health care system made them manage patients with HFNO, NIV or CPAP . • Started awake proning • Intubated patients only if they were failing from increased WOB • New York • Patients once intubated were ventilated for weeks with little change in lung status. Some physicians decided to just extubate patients to HFNO even if they had not improved and found that patients were almost the same as they were before intubation. • Some physicians began to delay intubation
TIMING OF INTUBATION • Rapid progression over hours • Lack of improvement on >40 L/minute of high flow oxygen and a fraction of inspired oxygen (FiO 2 ) >0.6 • Evolving hypercapnia, increasing work of breathing, increasing tidal volume, worsening mental status. • Hemodynamic instability or multi-organ failure
THROMBOSIS • High incidence of arterial and venous thrombi • DVTs, Pulmonary emboli, strokes an Mis • Elevated D-dimer
THROMBOSIS The situation is fluid and new information comes out daily. There will be a Pharmacy SBAR out weekly to keep everyone up to date on this issue.
WHAT WILL HAPPEN? • Best Case Scenarios. • Public Health measures can limit the spread. • The rate of spread in China seems to be slowing with strict public health measures. There are now less than one hundred new cases a day in China while in January and early February there were a few thousand a day. • Onset of summer in the Northern Hemisphere will end the outbreak. • The rate of spread in China is slowing as winter eases. • There has been less spread to or in South America where it is now summer. • The Spanish Flu in 1918 dissipated with the onset of summer – although it returned with a vengeance the next winter. • There may turn out to be many sub-clinical cases so the CFR will not be as high as now thought.
WHAT WILL HAPPEN • Worst Case Scenarios • Containment will not be possible and the pandemic will end when 50-70% of the worlds population get the virus. This scenario is supported by many prominent epidemiologists and virologists – especially those who study influenza. However, many think the CFR will fall to 0.5% because there are more mild and sub-clinical cases than now thought. • Some virologists think that COVID-19 will act like influenza and return yearly and be a new and persistent zoonotic illness. The four strains of coronavirus causing colds mutate constantly and people do not become immune to further infections just like the common cold. In the future we may have to deal with the common cold, influenza, and COVID-19 infections.
WHAT WILL HAPPEN • It appears the only way to stop the spread is to limit peoples movement and have a strict quarantine. It worked for China. Now Italy is trying the same strategy. • This will cause significant economic disruption. • BC’s COVID - 19 pandemic response plan: “focuses on delaying, containing, and preparing the Province to minimize serious illness and economic disruption. “
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