The majority of patients undergoing surgery take one or more prescription or over-the-counter medications, and this number increases with age. Clinicians must decide whether or not to continue each medication in the perioperative period. Unfortunately, there are no randomized controlled trials for perioperative management of most medications, and as a result, there is significant variation in clinical practice. The recommendations in this chapter are based on information from literature reviews, theoretical considerations, expert opinion, and our clinical experience.
PREOPERATIVE EVALUATION – GENERAL PRINCIPLES (SEE ALGORITHM IN FIGURE 4-1)
Obtain a complete medication history from the patient including prescription and over-the-counter medications, supplements, and substance use. Confirm the dose, frequency, and compliance with the regimen. In deciding whether or not to continue a medication preoperatively, consider the following issues: 1) indication for the drug; 2) effect on the primary disease if the drug is stopped (clinical deterioration, withdrawal symptoms, rebound effect); 3) drug pharmacokinetics (half-life, metabolism, and elimination) and potential changes in the perioperative setting (absorption, route of administration); 4) potential adverse effects on perioperative risk (bleeding, hypoglycemia) or drug interaction with anesthetic agents. Using these principles in a risk-benefit analysis, decide whether to continue, discontinue, or modify the current regimen for each medication.
Certain medications are essential and need to be continued. Many other medications can be safely continued but may not be necessary and are therefore considered optional. Finally, a few medications are potentially harmful and therefore should be discontinued or have the dose adjusted. Medications taken orally that must be continued should be given with a small amount of water on the morning of surgery. For hospitalized patients who may be “NPO” (nil per os) before surgery, it is important to add “except for medications.” Additionally, for medications that would normally be administered later in the morning, it is important to specify that the patient receive them on call to the operating room if the procedure is scheduled earlier.
It is beyond the scope of this chapter to discuss all medications, so we have chosen the medications and drug classes that are most common or important in our opinion. For additional information, the reader is referred to other online sources (UpToDate.com, preopevalguide.com, Dynamed.com).
PERIOPERATIVE MANAGEMENT – RECOMMENDATIONS BY DRUG CATEGORY (SEE TABLE)
Most cardiovascular drugs should be continued on the morning of surgery with the possible exceptions of diuretics, angiotensin converting enzyme inhibitors (ACEIs), angiotensin receptor blockers (ARBs), anticoagulants, and antiplatelet drugs. The latter two classes will be discussed separately.
Diuretics can cause hypovolemia and hypokalemia. However, with chronic administration, a steady state is achieved so that giving a single dose on the morning of surgery should not cause hypokalemia or significant volume depletion. A small RCT of patients on chronic furosemide found ...