Extravascular Blood loss or block of Intravascular blood flow
Vessel wall damage due to injury or disease causes haemorrhage, the breach is easily sealed with a localized primary hemostatic plug of platelets reinforced by a sturdier secondary plug with fibrin derived from the activated coagulation cascade. In larger structural damage, with significant volume loss, emergency treatment is required to prevent shock, with a potentially fatal outcome. Inside intact vasculature, blood flow is smooth and steady ensuring delivery of nutrition, oxygen, immune-mediating cells and soluble factors, and fluid to tissues. Activation of the coagulation cascade generates solid masses, thrombi, localized or generalized, static or dislodged as emboli with devastating consequences in distant organs. The Virchow’s triad of blood stasis or turbulence; endothelial disruption, hypercoagulability, whichdefines the classical pathophysiologic mechanisms that mediate the formation of thrombi due to a variety of triggers, has stood the test of time. The list of etiologies, that stimulate one or more of the three mechanistic pathways, is long – many find mention in the poetic summary below. Acute or chronic, management of bleeding, thrombosis and embolism is critical and challenging.
Insights and Impact
- Clinical history, be it age of occurrence, family history, lifestyle diseases, occupation, habituations, drug intake, pregnancy, co-morbidities, recent illnesses etc. is the foundation of focused investigation towards etiology.
- Clinical signs complement history and lead to rational, targeted investigations.
- Thromboembolism may be the first sinister sign of an occult malignancy in organs like the pancreas
- Severe infections causing septicaemia pose the greatest challenge, triggering DIC.
- Of note, in the recent COVID pandemic, survival from ARDS improved dramatically when the treatment pivoted towards adding anticoagulation respiratory support measures in critically ill patients. This was possible because early autopsies revealed the coexistence of microthrombi in the microvasculature which prevented adequate ventilation-perfusion to restore oxygenation.
- Restoration of the delicate balance of procoagulant and anticoagulant factors requires expert therapeutic options supported by careful laboratory monitoring.
- In many pre-existing conditions a high level of suspicion for thrombotic complications enables early diagnosis and lifesaving therapy.
Rhythm ’n rhyme
Between Scylla and Charybdis: bleeding – clotting a therapeutic dilemma
The smooth flow of blood ensures tissues are nourished and alive
With a pin-prick vessels ooze; with a cut blood flows - life can quickly dive;
After trauma to blood vessels, platelets rush to aggregate and plug
Activated coagulation factors reinforce these sticky particles, the clot is now well dug;
Clinical signs – petechiae, purpura, ecchymoses – measure dimensions to define
Help in filtering specific etiologies, choosing precise tests to diagnosis refine;
Bleeding disorders originate from weak vessels or platelet insufficiency
Inherited or acquired causes, quantitative or qualitative deficiency;
Ehlers Danlos, Marfan’s, HHF, haemophilia: syndromic, vascular or coagulation etiologies are rare
Acquired structural defects – scurvy, vasculitis – diagnose easily and treat with care;
Glanzmann’s thrombasthenia, Bernard Soulier syndrome, affect platelet quality
ITP, leukemias, hypersplenism, bone marrow failure, dramatically reduce their quantity;
Virchow’s triad the golden mantra: to outline coagulation pathophysiology:
Blood stasis or turbulence - endothelial damage – hypercoagulability;
Malignancy, nephrotic syndrome, oral contraceptives can activate coagulation
Early preventive action, rapid therapy, can prevent such non-physiological animation;
Atrial fibrillation and valvular disease create whirlpools, promoting thrombi
Anti-coagulation therapy in Covid infections spared many a patient the last sigh…
Old age and recumbency allow leg veins to develop a clot
Ominous their silent wait, for pulmonary embolism may be their lot;
Slowed circulation is the culprit in heart failure and shock
Pregnancy and postpartum thrombi, if not suspected, may run amok;
Clotting and bleeding delicately balanced in DIC, when sepsis underlies
“Diagnosis and management is a challenge” the internist often cries.
Deep Dive
A. Bleeding disorders – clinical signs by size
Acknowledgement of Image:
https://www.verywellhealth.com/petechiae-vs-purpura-5194291
Q. At what level of thrombocytopenia (platelet counts) is a patient most likely to bleed?
B. Virchow’s triad – pathophysiologic mechanisms of thrombosis
Acknowledgement of Image:
https://www.medicinehack.com/2011/07/virchows-triad.html
Q. List two therapeutic procedures that can lead to iatrogenic thrombosis.
Read on:
https://en.wikipedia.org/wiki/Between_Scylla_and_Charybdis
Kushner A, West WP, Khan Suheb MZ, et al. Virchow Triad. [Updated 2024 Jun 7]. In: StatPearls [Internet]. Treasure Island (FL): StatPearls Publishing; 2025 Jan-. Available from: https://www.ncbi.nlm.nih.gov/books/NBK539697/
Bukhari, Syed et al. Venous thromboembolism during pregnancy and postpartum period. European Journal of Internal Medicine, 2022: Volume 97, 8 – 17
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