2.6 Operational definitions
According to the provisional guidelines of the NIH
Pakistan,14 following definitions were employed in the
study.
Moderate Disease: Patients diagnosed with COVID-19 infection with any
one of the following features:
- Respiratory rate ≥ 30/min at rest.
- Oxygen saturation (SpO2) ≤ 93% on room air.
- Arterial oxygen partial pressure (PaO2) /oxygen uptake concentration
(FiO2) ≤ 300.
Severe Disease: Patients with moderate disease criteria plus any one of
the following:
- Oxygen requirement of more than 10 liters for 90% saturation.
- 50% of lung involvement on either chest X-ray or HRCT.
- CRP > 10 mg/L, D-dimer > 1000 mg/mL, serum
ferritin > 1000 ng/mL.
- Secondary infection (diagnosed by blood culture and sensitivity test
or raised procalcitonin).
- Arterial oxygen partial pressure (PaO2)/oxygen uptake concentration
(FiO2) [PaO2/FiO2] (PF ratio) < 118 mmHg.
Critical Disease: Patients with severe disease and any one of the
following were labeled as having critical disease:
- Shock
- Acute Respiratory Distress Syndrome (ARDS)
- Cardiac injury
- Multi-organ dysfunction
Shock: Persistent hypotension despite volume resuscitation, requiring
vasopressor to maintain mean arterial pressure (MAP) ± 65 mmHg and serum
lactate level > 2 mmol/L.15
ARDS: As per the Berlin Definition of ARDS:16
- Onset: Within one week of a known clinical consultation.
- Respiratory failure not fully explained by cardiac failure or fluid
overload.
- Bilateral opacities not fully explained by fluid overload, lobar or
lung collapse or nodules.
- Oxygen impairment with PF ratio < 300 mmHg.
Cardiac Injury: Cardiac injury is diagnosed if the serum level of a
cardiac marker (such as high-sensitivity troponin I) is higher than the
99th percentile upper reference limit, or the ECG and
echocardiogram show new abnormalities.17
Multi-organ Dysfunction: Acute life-threatening organ dysfunction with
any of the following signs:
- Altered mental status
- Reduced urine output
- Shortness of breath or increased respiratory failure
- Signs of impending shock or circulatory failure
- Decrease oxygen saturation
- Lab evidence of coagulopathy
- Thrombocytopenia
- Acidosis
- Raised lactate level
- Deranged liver function and renal function