COVID-19
Summary
COVID-19 is a systemic viral illness caused by the novel coronavirus SARS-CoV-2. First identified in Wuhan in 2019, it caused a global pandemic resulting in millions of deaths. The clinical spectrum ranges from asymptomatic infection to fulminant Acute Respiratory Distress Syndrome (ARDS) and multi-organ failure. Management has evolved rapidly; while early antivirals have a role, the cornerstone of survival in severe disease is immunomodulation (Steroids / IL-6 inhibitors) to dampen the cytokine storm, and aggressive respiratory support (CPAP/Proning). Vaccination has significantly reduced mortality. [1,2]
Key Facts
- Mechanism: The virus Spike (S) protein binds to ACE2 receptors, which are abundant in the lungs (type II pneumocytes), heart, kidneys, and endothelium.
- Microthrombi: COVID-19 causes a distinct "immunothrombosis" (endothelial inflammation + hypercoagulability), leading to a high rate of Pulmonary Embolism (PE) even in the absence of DVT.
- Evolution:
- Alpha/Delta: High virulence, severe pneumonia.
- Omicron: High transmissibility, immune escape, generally milder (upper airway tropism).
- Long COVID: Defined as symptoms persisting >12 weeks. Fatigue, brain fog, dyspnoea. Affects ~10% of cases.
Clinical Pearls
Happy Hypoxia: A unique feature where patients have profoundly low saturations (e.g., 70-80%) but appear comfortable and are not tachypnoeic. This is due to V/Q mismatch and preservation of lung compliance early on. Trust the oximeter, not the patient.
The Day 10 Crash: Patients often have a "biphasic" illness. Mild symptoms for a week, then sudden deterioration with fever and hypoxia around days 7-10. This signals the start of the hyper-inflammatory phase (Cytokine Storm).
Steroids Rule: Do NOT give steroids in the early viral phase (increases replication). Give Dexamethasone ONLY if the patient requires oxygen (RECOVERY trial).
Incidence
- Global Pandemic.
- Recurring waves driven by new variants and waning immunity.
Risk Factors for Mortality
- Age (Exponential risk >60).
- Obesity (BMI >30).
- Diabetes / Hypertension.
- Male sex.
- BAME ethnicity.
- Immunosuppression.
Stages of Disease
- Viral Response Phase (Days 0-7): Viral replication. Fever, dry cough, lymphopenia.
- Pulmonary Phase (Days 7-10): Pneumonia. Pneumocytes damaged. V/Q mismatch. Hypoxia.
- Hyperinflammatory Phase (Days 10+): Host immune system overreaction (Cytokine Storm - IL-6, TNF-alpha). ARDS. Shock. Coagulopathy.
Symptoms
Extra-Pulmonary
- Vitals: Pyrexia, Tachypnoea, Tachycardia.
- Saturations: Desaturation on exertion (sit-to-stand test) is an early sign.
- Chest: Often clear early on. Late: coarse crackles.
Microbiology
- PCR (Polymerase Chain Reaction): Gold standard. Deep nasopharyngeal swab.
- Lateral Flow Test (LFT): Antigen test. High specificity, lower sensitivity.
Bloods
- FBC: Lymphopenia is the hallmark. Neutrophilia implies secondary bacterial infection.
- CRP: Markers of inflammation. High CRP correlates with severity.
- D-Dimer: Elevated (Thrombosis risk).
- Ferritin: Elevated (Acute phase reactant).
Imaging
- CXR: Bilateral, peripheral, ground-glass opacities. "Crazy paving".
- CT Thorax: Ground glass -> Consolidation -> Fibrosis. Segmental PE?
Management Algorithm
CONFIRMED COVID-19
↓
OXYGEN SATURATION?
↓
┌─────────────┴─────────────┐
>94% (Room Air) less than 94% (Hypoxic)
↓ │
MILD/MODERATE SEVERE
Home care ADMIT HOSPITAL
(Pulse Ox monitoring) │
Consider antiviral ┌───┴───┐
(Paxlovid) if risk OXYGEN STEROIDS
(CPAP) (Dex)
+ ENOXAPARIN
1. Respiratory Support
- Oxygen: Target 94-98% (88-92% for COPD).
- CPAP: Continuous Positive Airway Pressure reduces need for intubation.
- Proning: Lie patient on front (improves V/Q match in dorsal lung segments).
- Intubation: For refractory hypoxia / fatigue.
2. Pharmacotherapy
Based on RECOVERY Trial data:
- Corticosteroids: Dexamethasone 6mg OD for 10 days. Reduces mortality in hypoxic patients.
- IL-6 Inhibitors: Tocilizumab / Sarilumab. For patients deteriorating despite steroids with high CRP.
- Anticoagulation: Prophylactic LMWH (Enoxaparin) for ALL admitted patients. Treatment dose if D-Dimer very high or suspected PE.
- Antivirals:
- Remdesivir: Marginal benefit.
- Paxlovid (Nirmatrelvir/Ritonavir): Highly effective in community to prevent admission in high-risk groups.
- Molnupiravir.
- ARDS: Acute Respiratory Distress Syndrome. Stiff, wet lungs.
- Pulmonary Embolism: Pulmonary thrombosis.
- Secondary Infection: Bacterial pneumonia (treat with Doxycycline/Co-amoxiclav if Procalcitonin high).
- Long COVID: Fatigue, palpitations (POTS), breathlessness, cognitive dysfunction.
- Mortality: Roughly 1% overall (pre-vaccine), much lower now. 20-30% in ICU patients.
- Recovery: Lung fibrosis occurs in severe ARDS survivors.
Key Guidelines
| Guideline | Organisation | Key Recommendations |
|---|---|---|
| NG191 | NICE | Use Dexamethasone for hypoxia. Don't use antibiotics unless bacterial coinfection suspect. |
| Living Guideline | WHO | Strong recommendation for Steroids and IL-6 blockers in severe disease. |
Landmark Trials
1. RECOVERY Trial (UK)
- Design: Massive adaptive RCT.
- Findings:
- Dexamethasone: Reduced death by 1/3 in ventilated patients. The single most important finding of the pandemic.
- Hydroxychloroquine: No benefit.
- Azithromycin: No benefit.
- Tocilizumab: Benefit in hypoxic patients with inflammation.
2. COM-COV: Supported mixing vaccines.
What is the new treatment?
We now know that in severe COVID, it's not the virus killing you, it's your own immune system overreacting. We use Dexamethasone (a steroid) to calm the immune system down. It saves lives.
Why do I need to lie on my stomach?
"Proning" helps open up the back parts of your lungs, which are squashed when you lie on your back. It gets more oxygen into your blood without needing a ventilator.
What is Long Covid?
Some people have symptoms for months. It is a genuine condition. It can cause extreme tiredness and brain fog. We don't have a cure yet, but pacing yourself is key.
Primary Sources
- NICE Guideline NG191. COVID-19 rapid guideline: managing COVID-19.
- The RECOVERY Collaborative Group. Dexamethasone in Hospitalized Patients with Covid-19. N Engl J Med. 2021;384:693-704. PMID: 32678530.
- Horby PW, et al. Tocilizumab in patients admitted to hospital with COVID-19 (RECOVERY). Lancet. 2021.
Common Exam Questions
- Medicine: "Patient admitted with COVID. O2 90%. CRP 150. Treatment?"
- Answer: Oxygen + Dexamethasone + LMWH.
- Pharmacology: "Mechanism of Tocilizumab?"
- Answer: IL-6 Receptor Antagonist.
- Pathology: "Lung findings in fatal COVID?"
- Answer: Diffuse Alveolar Damage (DAD) + Microthrombi.
- Radiology: "Typical CXR?"
- Answer: Bilateral peripheral patchy airspace opacification.
Viva Points
- Vaccine Types:
- mRNA (Pfizer): Genetic code for Spike protein in lipid nanoparticle.
- Vector (AstraZeneca): Chimpanzee adenovirus modified to express Spike.
- PIMS-TS: Paediatric Inflammatory Multisystem Syndrome. Kawasaki-like shock syndrome in kids weeks after mild covid.
Medical Disclaimer: MedVellum content is for educational purposes and clinical reference. Clinical decisions should account for individual patient circumstances. Always consult appropriate specialists.