There are a host of relevant curriculum items to choose from, although perhaps the most all-encompassing is knowledge of 'thromboprophylaxis in the perioperative period'.
A CRQ in 2021 (44% pass rate) saw candidates score well on risk factors and pathophysiology, but fall down on 'safe practice of central neuraxial block'.
A repeat CRQ in 2023 (49% pass rate) saw similar failings; timing with respect to neuraxial anaesthesia and 'contraindications to TEDs'.
Venous thromboembolism remains a major source of perioperative and peripartum morbidity and mortality
Approximately 25% of hospitalised patients who possess ≥1 risk factor will develop subclinical DVT; this may be higher in certain cohorts (e.g. 40-60% in hip surgery patients)
Of those with an identified DVT, approximately a third will go on to develop pulmonary embolism, and another third will develop chronic post-thrombotic leg syndrome
Much of this is preventable with implementation of appropriate VTE risk reduction strategies
Venous thrombi are predominantly composed of accumulated RBC's and fibrin, with lesser contributions from WBCs and platelets
The risk factors above all cause one or more elements of Virchow's triad, which is the underpinning pathophysiological trifecta behind venous thrombus generation:
Altered blood flow e.g. stasis or turbulence
Vascular endothelial injury
Increased coagulability due to alterations in blood components
Altered blood flow
Prolonged stasis lowers oxygen tension within the vein
This induces a pro-inflammatory state within the endothelium
This stimluates local:
Recruitment of WBCs, platelets, other microparticles
Activation of coagulation pathways
Causes of venous stasis include surgery, trauma, venous cannulas/catheters, bedrest, immobilisation, pregnancy and obesity
Sites of venous stasis include pelvic and calf venous sinuses, valve cusps, SVC, upper limb veins, portal venous system and right atrium/ventricle
Platelet activation occurs, with platelets contributing to thrombin and fibrin production (although more relevant in arterial than venous thrombus)
Sub-micron particles are shed from endothelial cells, WBCs and platelets, and provide a membrane surface for assembly of clotting cascade components
Activation of innate and acquired immune responses due to acute (perioperative) inflammation/infection or chronic inflammatory states e.g. inflammatory bowel disease, rheumatoid arthritis
Microparticles bearing tissue factor are present in high numbers in patients with malignant disease
Altered coagulability
Changes in the proportions of coagulation factors can occur due to congenital thrombophilias or acquired states:
Congenital e.g. deficiencies of protein C, protein S and anti-thrombin III
Acquired e.g. pregnancy | OCP | HRT - all cause hypercoagulability by increasing procoagulant activity and reducing both fibrinolysis and anticoagulant activity
Perioperative risk-reduction strategies for venous thromboembolism
Consider stopping oestrogen-containing oral contraceptives or HRT 4 weeks before elective surgery
If stopped, offer advice on alternative contraception
All patients should undergo risk assessment to identify the risk of VTE and bleeding
Assessment should take place on admission to hospital and use validated assessment tools
Balance risk of bleeding vs. VTE when deciding on prophylaxis
Minimise pre-operative fasting period, using IV fluids if prolonged periods of 'nil by mouth' are anticipated
Manage modifiable risk factors where possible e.g. smoking cessation, weight loss
Maintain adequate hydration although avoid fluid overload which may contribute to venous stasis e.g. due to cardiac failure
Anti-embolism stockings exert graded, circumferential pressure from distal to proximal regions of the leg
They should conform to the Sigel profile (a graduated compression profile which increases deep venous flow velocities):
Site
Pressure
Ankle
18mmhg
Mid-calf
14-15mmHg
Knee (popliteal break)
8mmHg
Lower thigh
10mmHg
Upper thigh
8mmHg
Should be worn day and night, but removed daily for hygiene
Thigh-length stockings are deemed preferable but no robust evidence they're superior to knee-length stockings
Doubts about their efficacy, particular in medical patients or as the sole treatment in high-risk patients
Contraindications to TEDs
Suspected or peripheral arterial disease
Peripheral arterial bypass grafting
Peripheral neuropathy or other cause of sensory impairment
Allergy to material
Severe leg oedema
Major limb deformity or size/shape that precludes correct fit
Local conditions that may be damaged; 'tissue paper' skin, dermatitis, gangrene, skin grafts
Intermittent pneumatic compression devices ('ICDs') and foot pumps
Periodically compress the foot, or the calf and/or thigh muscles
Inflation pressures up to 35-40mmHg
Mimic the muscle pump effect of walking
Promote fibrinolysis
ICDs reduce risk of VTE; foot pumps may reduce risk of subclinical DVT but not symptomatic DVT
Early mobilisation, facilitated by suitable analgesia
Return to oral intake, facilitated by suitable PONV prophylaxis
Patients should be provided with written and verbal information on VTE prophylaxis on discharge
Chemical prophylaxis (see below)
Chemical thromboprophylaxis
Should be started within 14hrs of admission to hospital (NICE guidance) unless contraindication
Typically uses LMWH, although heparin may be preferred (e.g. renal failure, need for rapid reversal)
Patients with pre-existing risk of thromboemobolic disease may need bespoke 'bridging' strategies to balance risk and benefit of prophylaxis in the perioperative period
Typiclly ceases after discharge but some patients may require prolonged courses e.g.:
Parturients with at least two risk factors should receive post-partum LMWH for at least 10 days
Post-elective hip arthroplasty; 28 days' LMWH (or 10 days' LMWH + 28 days aspirin)
Post-elective knee arthroplasty; 14 days' LMWH or aspirin
Receiving antiplatelet or anticoagulant therapy prior to admission
Suffered VTE so require long-term anticoagulation e.g. DOAC, warfarin