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COVID-19 infection

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Updated 2024 ISTH guidelines for antithrombotic therapy in COVID-19 infection.



COVID-19 is a severe acute respiratory infection caused by SARS-CoV-2, a positive sense, single-strand enveloped RNA virus belonging to the family Coronaviridae.
Person-to-person transmission primarily occurs through droplets generated during coughing and sneezing. Droplets can be transmitted directly through close contact, or via contaminated surfaces, where the virus may remain active for hours to days. Coughing and some airway management procedures can generate aerosols containing suspended viral particles, which can travel greater distances and be inhaled.
The inaugural COVID-19 outbreak was labelled a pandemic by the WHO on March 11, 2020.
Disease course
The clinical spectrum of SARS-CoV-2 infection appears to be wide, encompassing asymptomatic infection, mild upper respiratory tract illness, and severe viral pneumonia with respiratory failure. Cardiomyopathy has been described in a significant proportion of critically ill patients. Anosmia has been reported in association with presumed neuroinvasive disease.
Prognosis and risk of recurrence
Mortality remains high in patients requiring intensive care.


Key sources

The following summarized guidelines for the evaluation and management of COVID-19 infection are prepared by our editorial team based on guidelines from the Infectious Diseases Society of America (IDSA 2024,2023,2021), the International Society on Thrombosis and Haemostasis (ISTH 2024), the American College of Chest Physicians (ACCP 2023,2020), the European Society of Anaesthesiology and Intensive Care (ESAIC 2023), the World Health ...
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Screening and diagnosis

Indications for screening: as per WHO 2023 guidelines, screen all persons at the first point of contact with the health system in order to identify patients having suspected or confirmed COVID-19 and allow for early recognition followed by rapid implementation of source control measures.
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Classification and risk stratification

As per WHO 2023 guidelines:
Triage patients with suspected COVID-19 at a health facility, after screening and isolation, using a standardized triage tool (such as the WHO/IFRC Interagency Integrated Triage Tool), and evaluate for disease severity.
Based on triage:
initiate timely care for the acutely ill using a systematic approach, as described in WHO/ICRC Basic emergency care
refer patients to appropriate COVID-19 care destination after initial assessment, management and stabilization: within the health facility (critical care unit or ward); to a different health facility; community facility; or home, according to patient medical needs and established COVID-19 care pathways

Diagnostic investigations

Specimen collection
As per IDSA 2023 guidelines:
Consider collecting and testing swab specimens for SARS-CoV-2 NAAT from either the nasopharynx, anterior nares, oropharynx, mid-turbinate regions, saliva, or mouth gargle.
Consider collecting anterior nasal and mid-turbinate swab specimens for SARS-CoV-2 RNA testing by either patients or healthcare providers.

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  • PCR

  • Antigen testing (indications)

  • Antigen testing (setting)

  • Serology

  • Coagulation studies

  • Evaluation for thromboembolism (asymptomatic)

  • Evaluation for thromboembolism (symptomatic)

  • Evaluation for other etiologies

Respiratory support

Awake prone positioning: as per WHO 2023 guidelines, consider awake prone positioning of severely ill patients hospitalized with COVID-19 requiring supplemental oxygen (includes high-flow nasal cannula) or noninvasive ventilation.

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  • Conventional oxygen therapy

  • High-flow nasal cannula

  • Noninvasive ventilation

  • Face mask ventilation

  • Supraglottic airways

  • Endotracheal intubation

  • Mechanical ventilation

  • Recruitment maneuvers

  • Multiple persons per ventilator

  • ECMO

Medical management

General principles
As per WHO 2023 guidelines:
Use clinical judgment, including consideration of patients' values and preferences and local and national policy if available, to guide management decisions in patients with COVID-19 of any severity assessed in a clinic or hospital, including admission to hospital and to the ICU, rather than currently available prediction models for prognosis.
Identify, in all patients with COVID-19, if they have an advance care plan for COVID-19 (such as desires for intensive care support) and respect their priorities and preferences to tailor the care plan and provide the best care irrespective of treatment choice.

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  • Systemic corticosteroids

  • ICSs

  • Remdesivir

  • JAK inhibitors

  • Monoclonal antibodies

  • Tocilizumab

  • Convalescent plasma

  • Other immunomodulators (interferons)

  • Other immunomodulators (BTK inhibitors)

  • Other immunomodulators (IL-1R antagonists)

  • Other immunomodulators (IVIG)

  • Other immunomodulators (specific immunoglobulins)

  • Other immunomodulators (GM-CSF inhibitors)

  • Nirmatrelvir/ritonavir

  • Molnupiravir

  • Other antivirals (chloroquine/hydroxychloroquine)

  • Other antivirals (lopinavir/ritonavir)

  • Other antivirals (ivermectin)

  • Other antivirals (nitazoxanide)

  • Antibiotics

  • Antipyretics

  • Thromboprophylaxis, nonhospitalized patients (indications)

  • Thromboprophylaxis, nonhospitalized patients (choice of agent)

  • Thromboprophylaxis, hospitalized patients (indications)

  • Thromboprophylaxis, hospitalized patients (choice of agent)

  • Thromboprophylaxis, critically ill patients (indications)

  • Thromboprophylaxis, critically ill patients (choice of agent)

  • Antithrombotic therapy (thromboembolism)

  • Antithrombotic therapy (preexisting indications)

  • Antithrombotic therapy (acute coronary syndrome)

  • Antithrombotic therapy (AF)

  • Antithrombotic therapy (AIS)

  • Antithrombotic therapy (PAD)

  • Antithrombotic therapy (ECMO/CRRT)

  • Thrombolytic therapy

  • Intravenous fluids

  • Intravenous vasopressors

  • Other medications (general principles)

  • Other medications (RAAS inhibitors)

  • Other medications (statins)

  • Other medications (colchicine)

  • Other medications (famotidine)

  • Other medications (fluvoxamine)

  • Other medications (concomitant drugs)

  • Management of neuropsychiatric and neurological complications

  • Management of anxiety and depressive symptoms

  • Management of preexisting non-communicable diseases

Nonpharmacologic interventions

Nutrition: as per WHO 2023 guidelines, advise adequate nutrition and appropriate rehydration for patients with mild COVID-19.

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  • Psychosocial support

  • Rehabilitation

Therapeutic procedures

Intermittent pneumatic compression
As per ACCP 2020 guidelines:
Avoid adding mechanical prophylaxis routinely to pharmacological thromboprophylaxis in critically ill patients with COVID-19.
Consider performing mechanical thromboprophylaxis in critically ill patients with COVID-19 with a contraindication to pharmacological thromboprophylaxis.

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Perioperative care

Management of perioperative bleeding: as per ESAIC 2023 guidelines, do not perform major elective surgery in patients with COVID-19 coagulopathy.
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Specific circumstances

Pediatric patients: as per NIH 2021 guidelines, recognize that most pediatric patients with mild or moderate disease can be managed with supportive care alone.
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  • Older patients

  • Pregnant and breastfeeding patients

  • Patients with HIV

  • Patients with cancer

  • Transplant recipients and donors

Patient education

Patient education
As per WHO 2023 guidelines:
Counsel patients with mild COVID-19 about signs and symptoms of complications that should prompt urgent care.
Educate and provide support to patients with COVID-19 for the self-management of breathlessness and resumption of activities, both in a hospitalized and a nonhospitalized setting caring for COVID-19.

Preventative measures

Vaccination, COVID-19: as per NIH 2021 guidelines, offer COVID-19 vaccination for everyone eligible according to the Advisory Committee on Immunization Practices.

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  • Vaccination (influenza)

  • Pre-exposure prophylaxis

  • Post-exposure prophylaxis

  • Mask use

  • Personal protective equipment (routine care)

  • Personal protective equipment (aerosol-generating procedures)

  • Environment for airway management

  • Standard transmission precautions

  • Isolation

Follow-up and surveillance

Monitoring for disease progression: as per WHO 2023 guidelines, consider obtaining pulse oximetry monitoring at home as part of a package of care in patients with COVID-19, including patient and provider education and appropriate follow-up, in symptomatic patients with COVID-19 and risk factors for progression to severe disease who are not hospitalized.
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  • Monitoring for adverse effects of medications

  • Monitoring for thromboembolism

Quality improvement

COVID-19 care pathways
As per WHO 2023 guidelines:
Establish COVID-19 care pathways for patients with suspected or confirmed COVID-19 at local, regional and national levels.
Ensure that community health workers continue to follow usual protocols for recognition and treatment of other common illnesses and danger signs while activating the COVID-19 care pathway (including for referral as needed) for suspect cases. Refer to WHO/IFRC/UNICEF guidance on community-based healthcare, including outreach and campaigns, in the context of the COVID-19 pandemic.

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