Diuretics carry a risk of volume depletion and electrolyte derangements, and should be stopped once a patient becomes NPO. Excess volume is managed with as-needed intravenous formulations.
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Drugs Acting on the Central Nervous System
The majority of central nervous system (CNS)-active drugs, including antiepileptics, antipsychotics, benzodiazepines, bupropion, gabapentin, lithium, mirtazapine, selective serotonin and norepinephrine reuptake inhibitors (SSRIs and SNRIs), tricyclic antidepressants (TCAs), and valproic acid, balance a low risk of perioperative complications against a significant potential for withdrawal and disease decompensation. Therefore, these medications should be continued.
Carbidopa/Levodopa should be continued because abrupt cessation can precipitate systemic withdrawal resembling serotonin syndrome and rapid deterioration of Parkinson’s symptoms.
Monoamine oxidase inhibitor (MAOI) therapy usually indicates refractory psychiatric illness, so these drugs should be continued to avoid decompensation. Importantly, MAOI-safe anesthesia without dextromethorphan, meperidine, epinephrine, or norepinephrine has to be used due to the risk of cardiovascular instability.7
Diabetic Drugs
Insulin therapy should be continued with adjustments. Glargine basal insulin has no peak and can be continued without changing the dose. Likewise, patients with insulin pumps can continue the usual basal rate. Short-acting insulin or such insulin mixes as 70/30 should be stopped four hours before surgery to avoid hypoglycemia. Intermediate-acting insulin (e.g., NPH) can be administered at half the usual dose the day of surgery with a perioperative 5% dextrose infusion. NPH should not be given the day of surgery if the dextrose infusion cannot be used.8
Incretins (exenatide, sitagliptin) rarely cause hypoglycemia in the absence of insulin and may be beneficial in controlling intraoperative hyperglycemia. Therefore, these medications can be continued.8
Thiazolidinediones (TZDs; pioglitazone, rosiglitazone) alter gene transcription with biological duration of action on the order of weeks and low risk of hypoglycemia, and should be continued.
Metformin carries an FDA black-box warning to discontinue therapy before any intravascular radiocontrast studies or surgical procedures due to the risk of severe lactic acidosis if renal failure develops. It should be stopped 24 hours before surgery and restarted at least 48-72 hours after. Normal renal function should be confirmed before restarting therapy.8
Sulfonylureas (glimepiride, glipizide, glyburide) carry a significant risk of hypoglycemia in a patient who is NPO; they should be stopped the night before surgery or before commencement of NPO status.
Hormones
Antithyroid drugs (methimazole, propylthiouracil) and levothyroxine should be continued, as they have no perioperative contraindications.
Oral contraceptives (OCPs), hormone replacement therapy (HRT), and raloxifene can increase the risk of DVT. The largest study on the topic was the HERS trial of postmenopausal women on estrogen/progesterone HRT. The authors reported a 4.9-fold increased risk of DVT for 90 days after surgery.9 Unfortunately, no information was provided on the types of surgery, or whether appropriate and consistent DVT prophylaxis was utilized. HERS authors also reported a 2.5-fold increased risk of DVT for at least 30 days after cessation of HRT.9
Given the data, it is reasonable to stop hormone therapy four weeks before surgery when prolonged immobilization is anticipated and patients are able to tolerate hormone withdrawal, especially if other DVT risk factors are present. If hormone therapy cannot be stopped, strong consideration should be given to higher-intensity DVT prophylaxis (e.g., chemoprophylaxis as opposed to mechanical measures) of longer duration—up to 28 days following general surgery and up to 35 days after orthopedic procedures.10
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Perioperative Corticosteroids
Corticosteroid therapy in excess of prednisone 5 mg/day or equivalent for more than five days in the 30 days preceding surgery might predispose patients to acute adrenal insufficiency in the perioperative period. Surgical procedures typically result in cortisol release of 50-150 mg/day, which returns to baseline within 48 hours.11 Therefore, the recommendation is to continue a patient’s baseline steroid dose and supplement it with stress-dose steroids tailored to the severity of operative stress (see Table 2, above).