Perioperative medication Flashcards
What medicines should be continued prior to surgery?
- Parkinson’s medication (omission may reduce mobility and impede recovery)
- Beta-blockers (may help suppress the tachycardia and increased blood pressure provoked by anaesthesia and surgery)
- Most cardiac drugs such as anti-anginals and antihypertensives (excluding those that affect the RAAS (Tracheal intubation and surgical incision can increase heart rate and blood pressure so important to continue most antihypertensives)
What are the different surgery grades?
Grade 1 is minor and grade 4 is major complex surgery
What are some high risk medicines which may need to be stopped prior to surgery?
Cytokine modulators (glucocorticoids, ciclosporin, tacrolimus, myophenolate)
- Could increase risk of infection and delay wound healing
- Consider stopping two to four weeks before surgery depending on risk (higher risk includes grade 3+ surgery and patients with diabetes)
Lithium
- Electrolyte disturbances and reduced renal function can precipitate lithium toxicity
- In grade 1 or 2 surgery, the drug can be continued with close monitoring of U+Es
- In grade 3 or 4 surgery, it should be omitted 24 hours before the procedure
Antipsychotics
- Can potentiate arrhythmias and enhance hypotension due to a1 receptor blockade
- May be continued except for clozapine, the decision is influenced by the brand. Zaponex can be continued but Clozaril should be discontinued 12 hours before surgery where possible. Where stopped, clozapine should be restarted within 48 hours, at normal dose.
Why should drugs that affect RAAS be stopped prior to surgery?
Give some examples and when they should be stopped.
General anaesthetics cause vasodilation and drugs that affect the RAAS can exacerbate the resulting hypotension.
This is more of a problem in major surgery (these patients are more likely to experience fluid losses) and in patients with an epidural in situ because this also causes vasodilation
Examples: ACE inhibitors, ARBs and aliskerin.
Doses should be omitted on the morning of
the operation or from the evening before the operation if taken in the evening.
- If taken twice daily, both evening and morning doses should be omitted.
- If a patient takes both an ACEI and ARB and is to undergo grade 1 or 2 surgery, the ACEI should be omitted as above. Those undergoing grade 3 or 4 surgery should omit both the ACEI and the ARB
Why should anticholinesterases be stopped prior to surgery?
Examples: galantamine, rivastigmine, donepezil
Neuromuscular blocking agents used for anaesthesia work by interfering with acetylcholine (ACh) at the neuromuscular junction. Neuromuscular blockade results in muscle relaxation and short-term paralysis
Anticholinesterases prolong the action of depolarising neuromuscular blocker agents such as suxamethonium by increasing levels of ACh at the neuromuscular junction. The increased ACh competes with the
suxamethonium. At the same time the duration of action of suxamethonium is prolonged because it is also normally broken down by cholinesterase.
Those used to treat dementia (eg, galantamine and rivastigmine) should be stopped the day before surgery
- Both prolong the effects of suxamethonium and patients would need to be kept anaesthetised for longer
- Rivastigmine also antagonises the effects of non-depolarising muscle relaxants (such as atracurium) so their
muscle relaxant effects are reversed and the patient is difficult to paralyse.
Which anticholinergic drugs can be continued prior to surgery?
Donepezil
- Enhances the effects of suxamethonium and may antagonise the effects of non-depolarising muscle relaxants.
- However, it is continued because it would need to be stopped two to three weeks before an operation (due to its long half life) and if the drug is discontinued for 3-6 weeks patients will not obtain the original level of function that they had with initial treatment when it is restarted.
Anticholinesterases used in myasthenia
gravis (eg, pyridostigmine and neostigmine)
- Usually continued to prevent paralysis of the muscles involved in respiration but the anaesthetist should be informed.
- Sometimes the anaesthetist may request that they are omitted on the day of the procedure.
- Avoid suxamethonium in these patients.
What antidepressants should be stopped prior to surgery?
Monoamine oxidase inhibitors (MAOIs)
Hypertensive crisis can occur when MAOIs are used with sympathomimetics (eg, noradrenaline)
- Irreversible MAOIs should be
stopped two weeks before an operation but this must be discussed with the anaesthetist
and patient’s psychiatrist.
- Moclobemide, being a reversible MAOI,
can be stopped 24 hours before an operation. Its short elimination half-life, means activity returns to normal within 24 hours of stopping
Why should herbal remedies be stopped prior to surgery?
Ephedra
- Increases risk of myocardial infarction and stroke from tachycardia and hypertension
Echinacea
- May increase risk of infection and poor wound healing
Valerian
- May increase sedation
Garlic
- Can increase bleeding risk.
The following should also be stopped a week before an operation: cat’s claw, ginseng, omega fish oils and saw palmetto
Why and when should anticoagulants be stopped prior to surgery?
Heparin/low molecular weight heparin
- The last TREATMENT dose should be given no less than 24 hours before the operation
- The last PROPHYLACTIC dose should be given no less than 12 hours beofre
The bleeding risk of surgery depends on the type. For example, major abdominal surgery presents a greater risk than arthroscopy.
Why and when should antiplatelets be stopped prior to surgery?
Aspirin
- Usually continued unless there is a specific risk of excessive bleeding with a
procedure.
- However, may still be continued if there is a significant cardiovascular risk (e.g. coronary artery stent or recent or multiple myocardial infarction or stroke)
- It is generally considered safe to stop aspirin where it is used for primary prevention. This should be stopped seven days before a procedure to allow for
new platelets to generate.
Clopidogrel
- When used as a single agent, it should be
stopped seven days before an operation where there is potential for the patient to have an epidural or spinal anaesthesia. This is because of a possibility of increased risk of haematoma, which could compress the spinal cord.
- For patients who are not allergic to aspirin, it may be possible to switch to aspirin 75mg daily for seven days.
How are patients on DAPT managed prior to surgery?
Surgery is delayed until it was safe to stop the clopidogrel. However, it may not always be feasible to delay surgery
In these cases the pharmacist discusses
the best plan of action with a consultant anaesthetist and the patient’s consultant surgeon.
Aspirin is continued but the clopidogrel is stopped five days pre-operatively and tirofiban (short-acting) is used as a bridging agent in these patients
Should dipyridamole be stopped prior to surgery?
No, can be continued if used as single agent
Dipyridamole does not alter bleeding times or platelet aggregation.
However, when other antiplatelet agents are continued pre-operatively, dipyridamole is stopped 24 hours pre-operatively.
Should PPIs be stopped prior to surgery?
No, can be continued.
Patients who have acid reflux are at risk of acid aspiration under general anaesthesia.
Proton pump inhibitors and H2 antagonists help to increase gastric pH and lower gastric acid volume, and reduce the risk of acid aspiration
