Peri-op & Anaesthesia : DVT prevention and management

Question 1

When do pts admitted to hospital / having surgery get assessed for VTE risk?

Answer 1

on admission and re-assessed within 24 hours or if a change occurs in the clinical situation.

Question 2

Outline Virchows triad with an example for each cause

Answer 2

1. Abnormal flow- e.g. imbobility (flight / bed bound in hospital)
2. Abnormal blood components - e.g. smoking, sepsis, malignancy, Factor V Leiden
3. Vessel wall - atheroma formation, inflammatory response, trauma

Question 3

RF for VTE

Answer 3

• Increasing age
• Previous VTE
• Smoking
• Pregnancy or recently post-partum
• Recent surgery (especially abdominal surgery, pelvic surgery, or hip or knee replacements)
• Prolonged immobility (> 3 days)
• Hormone replacement therapy or the combined oral contraceptive pill
• Current active malignancy
• Obesity
• Known thrombophilia disorder (e.g. antiphospholipid syndrome or Factor V Leidin)

Question 4

Clinical features of DVT

Answer 4

• unilateral leg pain and swelling.
• low-grade pyrexia
• pitting oedema
• tenderness or prominent superficial veins.
• Importantly, 65% of DVTs are asymptomatic

Question 5

Inestigations for suspected DVT

Answer 5

DVT Wells’ Score should be calculated:

• Score < or equal to 1 – DVT is clinically unlikely, requires a further D-dimer test to exclude
• Score > than 1 – DVT is clinically likely and a DVT diagnosis should be confirmed with an ultrasound scan

Question 6

Explain why D-dimer needs to be interpreted with clinical picture, what else can cause it to be raised?

Answer 6

• A D-dimer test is sensitive but not specific
• a D-dimer may also be raised following recent surgery or trauma, with ongoing infection or inflammation, concurrent liver disease, or pregnancy, and indeed in any patient with a prolonged hospital stay.

Question 7

AR points on the Well’s Score for DVT

from NICE guideline 2023

Answer 7

Question 8

How do you manage a DVT?

NIce guidelines image and passmed

Answer 8

• DOAC apixaban or rivaroxaban as soon as suspect diagnosis
• if apixaban / rivaroxaban are NOT suitable then either LMWH followed by dabigatran or edoxaban OR LMWH (to cover until INR levels theraputic) followed by a vitamin K antagonist (VKA, i.e. warfarin)
• Provoked - 3 months
• unprovoked - 6 months
• in those with a proximal DVT and a persistent risk factor or high risk of DVT recurrence may require lifelong anticoagulation

Question 9

AR points well score for PE

Nice guidelines 2023

Answer 9

Question 10

What are thromboprophylaxis options used in hospital?

Answer 10

Mechanical
* Antiembolic stockings (AES)
* Intermittent pneumatic compression (IPC, more commonly used in theatre)

Pharmacological
* Low molecular weight heparin (LMWH), unless poor renal function (eGFR<30) then consider unfractionated heparin (UFH)

Question 11

Why are anticoagulants used in surgical patients?

Answer 11

Prevention of stroke, VTE embolism, PE, DVT, non-valvular AF

Question 12

With regard to warfarin, what measurements mean a patient is fit for surgery?

Answer 12

INR of 1.5 or below.

Question 13

Why might a surgical pt be on warfarin?

Answer 13

May have a mechanical heart valve. May have had a recent VTE?

Question 14

How is warfarin reversed in emergency surgery?

Answer 14

• IV Vit K if surgery can be delayed by 6-12hrs and INR is >1.5.
• If surgery can not be delayed, prothrombin complex (1 hr reversal).
• Fresh frozen plasma if PC not available. FFP- contraindicated in fluid overload

Question 15

A high risk pt usually on warfarin has had it reversed for surgery. What do you prescribe to ensure their blood does not clot?

Answer 15

LWMH for high risk pts. Can be stopped shortly before surgery then restarted after.

Question 16

A pt on rivaroxiban is due to have surgery soon. When should they stop taking it?

Answer 16

24-72hrs before surgery. This depends on their kidney function, half life and the surgical procedure

Question 17

What is the name of the antidote for dabigatran?

Answer 17

Idarucizumab - rapid reversal for emergency surgery or bleeding

Question 18

What is the name of the antidote for apixaban?

Answer 18

Andexanet alfa

Question 19

Why should you wait 4 hours after inserting an epidural anaesthetic before giving LWMH?

Answer 19

Risk of epidural haematoma - blood accumulates in the epidural space which mechanically compresses the spinal cord

Question 20

Which surgical procedures would need extended dalteparin/lwmh prophylaxis after surgery?

Answer 20

Major procedures such as orthopaedic (THR/TKR) as they have a higher risk of VTEs —> DVT/PE

Question 21

Specific RF for VTE in Surgical/trauma patients ?

Answer 21

• Surgical/trauma patients:
• hip/knee replacement
• hip fracture
• general anaesthetic and a surgical duration of over 90 minutes
• surgery of the pelvis or lower limb with a general anaesthetic and a surgical duration of over 60 minutes
• acute surgical admission with an inflammatory/intra-abdominal condition
• surgery with a significant reduction in mobility

Question 22

General RF for VTE in all pts

Answer 22

• active cancer/chemotherapy
• aged over 60
• known blood clotting disorder (e.g. thrombophilia)
• BMI > 35
• dehydration
• 1/+ comorbidities (e.g. heart disease; metabolic/endocrine pathologies; respiratory disease; acute infectious disease and inflammatory conditions)
• critical care admission
• HRT
• use of COCP
• varicose veins
• pregnant or less than 6 weeks post-partum

Question 23

Advice for pts post suregry to prevent VTE

Answer 23

Try to mobilise patients as soon as possible after surgery
Ensure the patient is hydrated

Question 24

compare how dabigatran and apixiban work

Answer 24