Medicines management in the perioperative period

We assess patients on their arrival to hospital in many different ways, from their age to renal function and co-morbidities. However, when patients are admitted for surgery, either acute or elective, a key indicator of their general health and potential postoperative complications is the medicines that they take. It is known that at least 50%¹ of patients admitted for surgery are taking medicines unrelated to their need for surgery. Pharmacists, as a part of the wider multidisciplinary team, are the key healthcare professionals to reduce the risk of medication withdrawal in the perioperative period and reduce non-surgical complications associated with poor medicines management.

An observation study by Kennedy et al found that 5% of patients,- taking medicines unrelated to their surgery suffered postoperative complications that were attributable to the cessation and subsequent withdrawal of their long-term medication regimen.¹ Although evidence pertaining to the risk of withdrawal of a patient’s regular medication is limited, Kennedy’s work strongly identifies the need for the correct management of patients’ non-surgery related co-morbidities through management of their long-term medication.

Subsequently, the continuation of a patient’s regular medicines, where possible, is a priority. Many medicines can be taken up to two hours before surgery with a sip of water; however, owing to potential interactions with anaesthetic agents, adjustment of a dose according to the operative schedule must be considered. When not possible due to the nature of the procedure or an increased anaesthetic/surgical risk due to drug therapy, it is necessary to omit a patient’s regular medicine for the shortest time possible.

Certain surgical procedures may result in a patient being nil by mouth or render the enteral route impossible for the administration of medicines. In such cases, it is necessary to consider alternative formulations and routes of administration to allow ongoing treatment of the patients non-surgical co-morbidities. An example of this is a gastrectomy, where all, or part, of a patient’s stomach is removed. This can often prove challenging for drug administration and, as such, advanced planning regarding the patient’s medication management is a necessity.

To ensure appropriate review and cessation/continuation of patient’s medication during the perioperative period, it is first vital to have accurate documentation of all preoperative medication. This ought to include all prescribed, over the counter and complementary medicines taken both regularly and on an ad hoc basis.² The medication history should also include a list of any recently stopped medicines.

Such information ensures anaesthetic agents are tailored to the patients’ individual needs and the ongoing management of their co-morbidities during their period of hospitalisation.

Prior to admission, patients who smoke need to be identified to support education as to the risks of smoking during the perioperative period and offered access to smoking cessation therapies. Although tobacco is not always considered when reviewing a patient’s drug history, the inhalation of tobacco smoke not only reduces lung function (something to avoid perioperatively) but the inhalation of tobacco smoke also increases the biotransformation of drugs.

Tobacco smoke results in selectively induced metabolism of certain drugs.³ Subsequently not only should patients be educated as to the effects of smoking on their general health, but also on the changes to drug metabolism and ultimately drug effectiveness.

To enable patients to receive their regular medicines (where possible) and to reduce the risk of non-surgical complications, certain principles can be followed.

There are certain factors that are to be considered when deciding whether to omit or alter a patient’s medication regimen in the perioperative period:

The primary action of the stomach is digestion, although a degree of drug absorption does occur here, in particular weak acids, for example, aspirin and warfarin, and non-ionised drugs. Therefore, in patients whose regular regimen includes such medication, it is important to know if the stomach is still a possible site for drug absorption.

Surgical procedures that do not alter stomach pH, and where eating postoperatively is not contraindicated, have little effect on drug absorption. Whereas for procedures that alter stomach size, cause changes in pH, or that require an extended nil by mouth period, alternative routes of administration must be considered. This may include: intravenous, subcutaneous, intramuscular, transdermal, or via nasojejunal and percutaneous jejunostomy tubes if in situ.

When administering medicines via feeding tubes it is important to note that this is often outside of a medicinal product’s license; subsequently the prescriber is liable for any problems that occur as a result. There are several considerations required when using a feeding tube for medicine administration, including a review of the medicinal formulation to be administered. Regarding tablets, soluble preparations can be used whereas non-dispersible tablets may result in a blockage and require the tube to be changed or, where possible, cleared.

Modified-release tablets must not be crushed because this results in a loss of the coating responsible for a gradual release of the medicinal product causing an unpredictable alteration to absorption. Capsules may be opened but, as with modified-release preparations, the rate of absorption and time to peak plasma concentration may be altered. When using liquids, it is necessary to identify those requiring dilution before administration to prevent any blockage.

Some drugs can bind to feeding tubes (for example, phenytoin), and therefore require dilution and frequent flushing of the tube to prevent any loss of dosage. For more detailed information on the use of feeding tubes for drug administration, see the Handbook of Drug Administration via Enteral Feeding Tubes (Pharmaceutical Press) and the Summary of Product Characteristics for the individual drug(s).

Different indications of a drug are associated with different risks and implications to a patients quality of life when omitted.

In the case of combined oral contraceptives (COCs), these should be to stopped a minimum of four weeks prior to surgery to ensure a reduced risk of surgical venous thromboembolism.⁴ For patients using these agents for contraception, alternative methods are available.

However, for a patient using COCs as a means to manage the symptoms of endometriosis, the absence of therapy might have such an impact on their life (for example, reduced ability to work, increased pain and bleeding) that they are not willing to stop taking for four weeks.

This is becoming of greater importance as we use medicines for a greater number of indications than their original licensed indication. To ensure decisions are made in collaboration with the patient, discussions need to be had at the earliest opportunity regarding why a patient is taking a medicine, it may not always be for what we as health professionals expect.

Once the indication is known, the impact of its omission can be discussed with the patient, and pending risk of continued therapy, the operating surgeon and anaesthetist.

Simply put, we must ask: what time is the medication due and at what time is surgery planned?

This is most important when planning the perioperative medicine management of patients with diabetes. Updated guidance from NHS Diabetes states that the majority of diabetic patients missing more than one meal (as a result of starvation for surgery) will require variable rate insulin.⁵

This allows surgeons to plan (where possible) when to operate according to a patients co-morbidities and so reduce the number of interventions required owing to missed medication doses resulting in greater perioperative complications.

For elective surgical patients, it is much easier to plan whether they are more suited to a morning or afternoon surgical list and to rearrange their medication doses around the time of surgery. An awareness that oral medicines can be taken up to two hours prior to anaesthetic induction will support such changes.

In acute settings, this can be near impossible and often results in patients missing multiple medication doses, because the time of surgery is unknown (when waiting on an acute list). However, steps can be taken to reduce the number of missed doses through discussion with the anaesthetist and operating surgeon, who, although will not be able to provide a specific time, will be able to advise if the wait is liable to be greater than two hours and confirm they are happy for a medication to be taken with a sip of water.

As previously mentioned, surgery affecting the gastrointestinal tract has greater impact on a patient’s medication regimen than orthopaedic surgery. However, factors such a interactions with anaesthetic agents and analgesia, bleeding risk and postoperative complications must still be considered before any changes are made.

There are many procedures for which it is safe to continue a patients regular aspirin (with the operating surgeons knowledge) including colonoscopies and cystoscopies (in the absence of biopsy). However, to do this may require the operating surgeon to take a different approach, for example, the use of diathermy. Subsequently the safe and appropriate continuation of a patient’s regular medicines is dependent upon collaboration between the operating surgeon, pharmacist and anaesthetist. Each professional has their specialist knowledge and, as the expert in medicines, the pharmacist is ideally placed to ask questions relating to a procedure’s bleeding risk and advise on the risk of continued therapies.

Although discussed last, this is by no means the least of the considerations. Individuals take medicines for a reason, whether to treat a heart condition, control pain or manage a long-term condition.

Any change to a patient’s medication regimen should always be discussed with the patient; for some, and certain medicines, a temporary change can be managed with minimal changes to their outward symptoms. Although many caution the abrupt withdrawal of any medicine, it is also widely known that problems related to withdrawal only begin after two or more days of stopping drug therapy. Therefore, for many procedures it is possible for patients to miss their dose the morning of surgery and to restart the following day without any obvious adverse effects.

This does require a common sense approach, surgery increases the stress on an individual’s body and this can be seen as an increase in cortisol secretion. Consequently those patients taking medication to reduce their frailty and manage the ever day stresses to their body (for example, cardiovascular drugs), will be at increased risk of postoperative complications. If these medicines are stopped, the patient may not be able to withstand the stresses of the operation and the postoperative recovery.

To ensure patients are holistically assessed and their current co-morbidities managed in the perioperative period, collaborative working between all members of the surgical multidisciplinary team is essential. The approach that a surgical procedure would be impossible without the surgeon is reasonable.

However, it needs also to be reasonable for patients to expect little or no impact on their non-surgical long-term conditions during the perioperative period, and to do this we need to better manage their chronic medication regimen. Without a multidisciplinary approach, aspects of patient care are incomplete.

It is with this thought that national guidance for the perioperative management of medicines will be launched in September 2016. However, even with this, it is paramount that every patient and their surgery is assessed on an individual basis.

1. Kennedy JM et al. Polypharmacy in a general surgical unit and consequences of drug withdrawal. Br J Clin Pharmacol 2000;49(4):353–62.
2. Rahman MH, Beattie J. Medication in the peri-operative period. Pharm J 2008;272:287.
3. Gibson G, Skett P. Introduction to Drug Metabolism. Third Edition. 2001. Nelson Thornes.
4. Vandenbroucke JP et al. Oral contraceptives and the risk of venous thrombosis. N Engl J Med 2001;344:1527.
5. NHS Diabetes. Management of adults with diabetes undergoing surgery and elective procedures: improving standards, 2011. www.diabetes.org.uk/Documents/Professionals/Reports%20and%20statistics/M… (Last accessed April 2016).