DVT prophylaxis

VTE risk factors

Strong VTE risk (odds ratio >10)	Moderate VTE risk (odds ratio 2–9)	Weak VTE risk (odds ratio <2)
Fracture (hip or leg)	Arthroscopic knee surgery	Bed rest >3 days
Hip or knee replacement	Central venous lines	Immobility due to sitting (e.g. prolonged car or air travel)
Major general surgery	Malignancy and/or chemotherapy	Increasing age (e.g. >60)
Major trauma	HRT and oral contraceptives	Laparoscopic surgery (e.g. cholecystectomy)
Spinal cord injury	Congestive heart/respiratory failure	Obesity
ㅤ	Paralytic stroke	Varicose veins
ㅤ	Pregnancy (post‑partum)	Pregnancy (antepartum)
ㅤ	Previous VTE	ㅤ
ㅤ	Thrombophilia	ㅤ

Preop

Women to consider stopping estrogen-containing oral contraception or HRT 4 weeks before surgery,

Assess the risks and benefits of stopping antiplatelet therapy 1 week before surgery.

Indication of pharmacological prophylaxis

In the absence of normal VTE risk factors,

If total anesthetic + surgical time > 90 min in patient for

Surgery
Post trauma are high risk

Surgery involves pelvis or lower limb and total anesthetic + surgical time > 60 min;

If acute surgical admission with inflammatory or intra-abdominal condition.

Mechanical VTE prophylaxis options

Anti-embolism stockings (thigh or knee length),

Foot impulse devices,

Intermittent pneumatic compression devices (thigh or knee length).

Pharmacological VTE prophylaxis options

Fondaparinux sodium

Synthetic pentasaccharide factor Xa inhibitor

Low molecular weight heparin (LMWH)

Mechanism of action

LMWH activates antithrombin III → Antithrombin III binds to and inhibits factor Xa → prevents activation of the final common path; Xa inactivation means that prothrombin is not activated to thrombin, thereby not converting fibrinogen into fibrin for the formation of a clot.

Absorption

Peak effect of enoxaparin is observed approximately 4 hours after administration.
Anti-Factor Xa activity is detected in plasma for about 12 hours

Unfractionated heparin (UFH) (for patients with renal failure).

Heparin

Mechanism	Activates antithrombin, which decreases activity of factors IIa (thrombin) and Xa; short half‑life.
Clinical use	Immediate anticoagulation for pulmonary embolism (PE), acute coronary syndrome, MI, deep venous thrombosis (DVT); used during pregnancy (does not cross placenta); monitor PTT.
Adverse effects	Bleeding (reversible with protamine sulfate); heparin‑induced thrombocytopenia (HIT); osteoporosis (with long‑term use); drug interactions; type 4 renal tubular acidosis. - HIT type 1: mild (platelets > 100,000/mm³), transient, nonimmunologic drop in platelet count that typically occurs within the first 2 days of heparin administration; not clinically significant. - HIT type 2: development of IgG antibodies against heparin–bound platelet factor 4 (PF4) that typically occurs 5-10 days after heparin administration. Antibody-heparin-PF4 complex binds and activates platelets → removal by splenic macrophages and thrombosis → reduces platelet count. Highest risk with unfractionated heparin. Treatment: discontinue heparin, start alternative anticoagulant (eg, argatroban). Fondaparinux safe to use (does not interact with PF4).
Notes	Low-molecular-weight heparins (eg, enoxaparin, dalteparin) mainly act on Xa; fondaparinux acts only on Xa; both are not easily reversible; unfractionated heparin used in patients with renal insufficiency (low-molecular-weight heparins should be used with caution because they undergo renal clearance).

Anticoagulation reversal

Anticoagulant	Reversal agent	Notes
Heparin	Protamine sulfate	Positively charged peptide that binds negatively charged heparin
Warfarin	Vitamin K (slow) ± FFP or PCC (rapid)	ㅤ
Dabigatran	Idarucizumab	Monoclonal antibody Fab fragments
Direct factor Xa inhibitors	Andexanet alfa	Recombinant modified factor Xa (inactive)

Contraindication

Severe peripheral arterial occlusive disease (PAOD) with

Ankle brachial pressure index (ABPI) <0.6,
Ankle pressure <60 mm Hg,
Toe pressure <30 mm Hg, or transcutaneous oxygen pressure < 20 mm Hg;

Suspected compression of an existing epifascial arterial bypass;

Severe cardiac insufficiency (New York Heart Association [NYHA] class IV);

Routine application of MC in NYHA III without strict indication, and clinical and hemodynamic monitoring;

Confirmed allergy to compression material; and

Severe diabetic neuropathy with sensory loss or microangiopathy with the risk of skin necrosis

Peripheral neuropathy

Outcome

Anticoagulation is proven to reduce both symptomatic and asymptomatic VTE events in screened patients in a number of trials, but given the risk of intracranial haemorrhage in neurosurgical patients significant debate surrounds the potential harm associated with active screening and treatment of asymptomatic VTE (which may or may not become symptomatic): is the risk of harm from an untreated asymptomatic VTE greater than the risk of harm due to haemorrhage from treating it?

Rates of haemorrhage in neurosurgery patients have been cited as 2.1% in those receiving low-molecular-weight heparin and 1.1% in those without anticoagulation.

Venous thromboembolism (VTE) events and mortality rate

Group	Total patients (%)	30‑day mortality rate (%)
Overall cohort	10 447	4.8
No VTE	10 114	4.6
VTE	333 (3.2)	9.6
DVT	246 (2.4)	10.2
PE	131 (1.3)	10.7

DVT, deep vein thrombosis; PE, pulmonary embolism

PE

Clinical presentation

Only 10% of patients present with the triad of

Pleuritic chest pain,
Dyspnea
Hemoptysis

PIOPED study in 2007

Most common clinical signs in PE to be (in order)

RR > 18,
Chest crackles,
HR > 100 bpm
Fever > 37.8 °C.

Management in a stable patient suspected of PE

Sinus tachycardia, RBBB and right axis deviation,

20% ot pt has classic (S1Q3T3)

Large S wave in lead I,
Large Q wave in lead III
Inverted T wave in lead III

Hypoxemia
Hypocapnea
(Respiratory alkalosis) due to hyperventilation
May show a normal PO2 in up to 20%.

An SpO2 < 95% on room air is predictive for increased mortality and morbidity.

Wells score for PE should be performed.

If the score is 5 or more a PE is likely,

Treatment

CTPA should be arranged and if there is any delay then LMWH should be started.

Pregnant women (RCOG guidelines)

Have a USS Doppler of both legs as if a DVT is found they can be started on anticoagulation without any radiation exposure.
If the USS is negative and CXR normal they should then be offered the informed choice of V/Q scan or CTPA.

Risk of childhood cancer

Scanning methods	Risk of childhood cancer
V/Q scanning	1/280,000
CTPA	< 1/1,000,000

Maternal breast cancer

Breast tissue particularly sensitive to the effects of radiation during pregnancy.
CTPA slightly increases the lifetime risk of maternal breast cancer (increased by up to 13.6%, background risk of 1/200 for study population)

If Wells PE score is 4 or less, d-dimer is advised in those without intercurrent illness or pregnancy (where it is often raised), whereas an individual decision whether to perform CTPA will need to be made for those in whom d-dimer cannot further risk stratify.
Clexane is safe during pregnancy