119 CMAAO CORONA FACTS and MYTH BUSTER: Corona predictions
models
Dr K K Aggarwal
President CMAAO
943: Round Table Expert Zoom Meeting on “Corona
prediction models”
Formulas
in relation to COVID-19 pandemic for better understanding of data & risk
stratification
6th
June, 2020, 11am-12pm
Participants
Dr
KK Aggarwal
Dr
DR Rai
Dr
Suneela Garg
Dr
Girdhar Gyani
Dr
Narottam Puri
Prof
Mahesh Verma
Dr
Ashok Gupta
Dr
JA Jayalal
Mrs
Upasana Arora
Dr
Jayakrishnan Alapet
Dr
K Kalra
Mr
Anil Kumar, Director HCFI
Dr
Sanchita Sharma
Formulas in relation
to COVID-19 pandemic for better understanding of data
- Wuhan conducted
6.5 million tests (nasal swab, RT PCR) for coronavirus in 10 days, when 6
new cases were detected; 200 cases were found, mostly people who showed no
symptoms. The ratio of undocumented cases for each documented case in
Wuhan is 1:33 i.e. there were 33 asymptomatic cases for every one new
infection. This ratio in New York was found to be 1:10 i.e. there were 10
asymptomatic patients, for every positive patient.
- We need to know
realistic figures as many will be presymptomatic or asymptomatic.
Comparison of data should be between epicenter and epicenter, non-epicenter
and non-epicenter.
- Statistics help
in preparedness.
- Number of
expected deaths is 15%
of the number of serious patients 14 days back.
- Death rate is the number of deaths
today vs number of cases today.
- Corrected
death rate is the number of cases today vis a vis number of
cases 14 days back.
- Estimated number of deaths: For
every one death, there will be one unreported death. It is calculated as
number of reported deaths x 2.
- Deaths are not
labeled as due to Covid-19 because the primary cause of death is reported
as e.g. pulmonary embolism; covid-19 is reported as a secondary cause of
death.
- Number
of tests per million population: More the number
of tests, more will be the number of cases. Government guidelines advise
against screening of asymptomatic cases.
- Doubling
rate:
India (14 days), France (49 days); if there are 2.5 lakh cases in India
today, this number will double in about 15 days to 5 lakhs and so on.
- Seir
model: it talks about how many are susceptible, how many
are exposed, infected or recovered
- Non
pharmacological interventions should be taken into consideration; at least
50% of quarantine will be helpful.
- We need to
stratify the impact of Covid-19 on hospitalization, ICU admissions, and
fatality rate.
- Of those who
died, 67% had comorbidities, while 37% had no comorbidity. It is this
group, which should not be ignored.
- There is
similarity between dengue and Covid-19.
o
In dengue, when
fever resolves, then capillary leakage may occur and patient may become critical.
Administration of hydration at this point of time will reduce or prevent
mortality.
o
In
Covid-19,
after fever, silent hypoxia occurs – this gives 5 hour window. The time hypoxia
develops, if home oxygen is administered, first dose of LMWH is given and then
look for hospital – this will buy 5-6 extra hours and may prevent mortality. A
ventilator is not the answer. Early oxygen is the answer; early heparin is the
answer.
- It is important
to calculate the number of people who will require oxygen. This data will
help to reduce mortality.
o
Number of
oxygen requirement is 10% of new admissions today; this will happen
after 7 days. For example, if there are 1000 cases in Delhi today, 100 patients
will need oxygen therapy after 7 days. But actually, there may be 30,000
asymptomatic cases (if the ratio from Wuhan study is applied) and 3000 of these
will need oxygen after 7 days.
o
Number of
ventilator requirement is number of cases today x 3, which will
manifest on the 9th day.
- According to
ICMR guidelines for home discharge, mild, very mild and presymptomatic
cases need not be tested at the time of discharge. But, presymptomatic
cases cannot be diagnosed without testing.
Risk stratification –
“Am I at risk?”
- Male
or female: Females are protected till menopause because of
female sex hormones, then they are at similar risk as males.
- Children up
to 2 years are protected due to thymus gland. The hyperactive thymus
produces cytokines, which are protective. In children, mortality is seen
only in children with congenital heart disease, nephrotic syndrome
- Am
I in a high-risk group? The chances of healthcare workers are highest
in ICU and ER personnel, intensivists, ENT doctors, ophthalmologists and
dentists.
- What
are my chances of acquiring infection in OPD? Follow the
Singapore protocol.
o
If contact time is less than 10 minutes and
the patient and the doctor have both used a mask (simple surgical mask and N95,
respectively), the risk is very low.
o
If the contact time is less than 30 minutes,
the risk is mild
o
If the contact time is more than 30 minutes,
the risk is high and you need to undergo test
- Can
you tolerate hypoxia? If you have uncontrolled diabetes,
heart failure, COPD, asthma, you will not be able to tolerate hypoxia even
for 2 hours. You are at high risk.
- Are
you at risk of hypercoagulation? If you have
inflammatory disease such as Crohn’s, rheumatoid arthritis, SLE,
ulcerative colitis, Sjogren, you are vulnerable to hypercoagulable state
despite anticoagulant. Such cases, even if asymptomatic, will suddenly
develop embolism on Day 8/9, which may lead to death.
- Surgical
time:
Keep surgical time less than 30 minutes.
If
you take all these precautions, you are at controlled risk and can continue to
work.
Being
male and having any cardiac decompensated state increases your risk. A cardiac patient cannot tolerate anoxia,
tachycardia and irregular heart rate. All these three occur in Covid-19. Opt
for teleconsultations.
- All doctors
should carry a portable pulse oximeter to detect silent hypoxia, which
occurs on Day 7 even if you are asymptomatic.
- Keep an oxygen
concentrator in your office and at home. Monitor oxygen.
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