Surgery - Pre-op Drug Therapy Considerations Flashcards
Warfarin
Should be stopped around 5 days (6 days according to RUH) before surgery
INR less than 1.5 for surgery to proceed
If emergency surgery
- Vit K (reversal within 4-24 hours)
- Beriplex (reversal within 1 hour)
Consider risk of thrombo-embolism on stopping
With reference to the CHADSVASc score, when is LMWH required after stopping warfarin pre-surgery?
Low Risk of VTE (Score 0-2 and no prior stroke/TIA or single VTE more than 12 months ago with no risk factors)
- No LMWH required
Moderate Risk of VTE (Score 3-4, Recurrent VTE, VTE in past 3-12 months, Active cancer)
- Start therapeutic dose of LMWH two days after stopping warfarin
High Risk of VTE (Score 5-6 with prior stroke/TIA, Mitral valve/Starr Edwards disc valce prostesis or VTE in last 3 months)
- LMWH as with moderate or admit for unfractionate heparin infusion once INR less than 2 or 3
What are the bridging guidelines with warfarin pre-surgery?
Take last dose of warfarin SIX days before surgery
Start LMWH at 8am 2 days after stopping the warfarin
OMIT the LMWH on the morning of surgery and stop unfractionated heparin 6 hours before surgery
What doses of LMWH are usually prescribed depending on (clot and bleed risk)?
Prophylactic LMWH (low clot risk)
- Low bleed risk = evening post op (12 hours)
- High bleed risk = 24-48 hours post op
Treatment LMWH (moderate/high clot risk)
- Low bleed risk = prophylactic evening post op then therapeutic dose 24-48 hours post op
- High bleed risk = prophylactic dose 24-48 hours post op then therapeutic dose 48-72 hours post op
IV UFH if very high risk (e.g. mechanical heart valves)
NOACs
Minor Surgery: Stop 1 day before
Major Surgery: Stop 2-3 days before
Anti-platelets
Aspirin - continue unless very high bleeding risk (then stop for 7 days pre-op)
Clopidogrel, prasugrel, ticagrelor - stop 7 days pre-op. Substitute with aspirin if possible. Do NOT stop if high risk of coronary stent clot.
Dipyridamole - continue if used alone, stop the day before surgery if used in combination with aspirin.
When do you normally restart NOACs after surgery?
24-72 hours post op.
Cover with LMWH until started but there is no need to overlap
When do you normally restart Antiplatelets after surgery?
Morning after surgery, but consider if patient has an epidural
Long-term steroid therapy
Stress of surgery causes plasma ACTH hormone and cortisol levels to rise
ALL OF THIS BELOW IS IN THE BNF
Patients on more than 10mg/day prednisolone within 3 moths of surgery may need IV hydrocortisone during surgery
Minor surgery
- Usual steroid dose in the morning OR 25-50mg hydrocortisone IV on induction
- Then recommence usual oral dose
Moderate or Major surgery
- Usual steroid dose in the morning AND 25-50mg hydrocortisone on induction.
- 25-50mg hydrocortisone IV TDS for 24 hours post-op (moderate surgery) or 48-72 hours post-op (major surgery)
- Recommence usual oral dose
Insulin and Oral Hypoglycaemics
Minimise starvation time by placing first on list
- Diabetics should not miss more than one meal
Pre-op
- Tend to OMIT oral hypoglycaemics on morning of surgery
- Continue long acting insulin? Reduce dose
- Halve am dose of biphasic insulin or intermediate insulin
- OMIT am and lunch doses of short/rapid acting insulin
- Close monitoring of BG levels
- Reintroduce normal regime when oral intake resumed
Peri-op management
- VRIII indicated if more than one missed meal (major surgery) or uncontrollable hyperglycaemia
- 2 lines through one venflon
- Line 1: 50units/50ml actrapid insulin
- Line 2: 500ml 5% dextrose over 5 hours
- Insulin rate adjusted to blood glucose monitoring (aim for 6-10 mmol/L)
Oral Contraceptives
STOP COCP 4-6 weeks before major elective surgery, leg surgery or surgery causing prolonged immobility
GIVE progesterone only pills (POPs)
Consider risks of stopping
Emergency surgery - Give thrombopropylaxis
Tamoxifen
Increased risk of VTE
Consider if risk of VTE outweighs risk of stopping treatment
- Stop 3 weeks before and after major surgery
MAOIs
Potential fatal drug interactions
- Analgesics (tramadole, increased serotonerigc activity leading to CNS toxicity or increased convulsion risk)
- Sympthaomimetics (risk of hypertensive crisis)
Consult with prescriber before deciding to stop (if possible)
- REDUCE down to STOP 2 weeks before surgery
Caution with anaesthesia if not stopped
Lithium
Narrow therapeutic range, renally excreted
Fluid imbalance can precipitate toxicity
STOP 1-2 days before major surgery
IF continue:
- Monitor lithium levels
- Monitor fluid balance
- Avoid NSAIDs
Anti-convulsants & Anti-Parkinson’s medication
CONTINUE treatment as it is essential
- Ensure it is taken morning of surgery
Consider alternative routs of admin if NBM or not absorbing
