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Benzodiazepines are the class of drugs most frequently used preoperatively to achieve sedation, relief of anxiety, and amnesia. Diazepam (5 -10 mg po) may be given with sips of water 1½ - 2 hr preoperatively. Lorazepam (0.5 - 2 mg) may be given either by the sublingual or oral route. Lorazepam provides excellent amnesia and sedation, but occasionally, patients remain excessively drowsy after the surgery.

Oral midazolam may be used for pediatric patients or developmentally delayed adults 30 min preoperatively in a dose of 0.25 - 0.5 mg∙kg^-1. To enhance acceptance, a flavored suspension of acetaminophen, in a dose appropriate to the patient’s age, is frequently used as a base to which the midazolam is added. To prevent a fall or injury after the administration of midazolam, the patient should be watched closely and, in the case of a child, the patient may be held in the parent’s arms.

Melatonin is a naturally occurring hormone found in the pineal gland and is involved in the regulation of circadian rhythms. Exogenous administration facilitates both the onset and quality of sleep and does not suppress rapid eye movement (REM) sleep. In contrast, benzodiazepines impair sleep quality and reduce the duration of REM sleep. Unlike benzodiazepines, melatonin is not associated with a “hang over” effect.¹ A single dose of melatonin 5 mg resulted in a reduction in anxiety comparable with sublingual midazolam 15 mg when administered 100 min prior to surgery.² Melatonin 0.25 mg∙kg^-1 was comparable with midazolam 0.5 mg∙kg^-1 in reducing preoperative anxiety in children.³ In this study, children given melatonin preoperatively experienced a faster recovery, a lower incidence of postoperative excitement, and less sleep disturbance postoperatively compared with children given midazolam. A recent review highlighted the role of melatonin in the perioperative period for its sedative, analgesic, and antioxidant properties.⁴ Despite the theoretical advantages of melatonin compared with a benzodiazepine, its use has not been widely adopted as a preoperative sedative.

Opioids, such as hydromorphone, morphine, and meperidine, provide both sedation and analgesia. They are appropriate for patients experiencing pain prior to their surgery (e.g., fractured extremity awaiting surgery). Troublesome side effects of opioids may occur, including nausea, vomiting, biliary spasm, respiratory depression, bradycardia, hypotension, and true allergic reactions. Consider ordering supplemental oxygen for patients requiring an opioid medication.

An anticholinergic agent may also be used if an “awake” fibreoptic-assisted tracheal intubation is planned. The use of an anticholinergic in these patients causes decreased secretions from oral salivary glands, thereby facilitating both absorption of topical anesthetics and visualization of the airway when using a fiberoptic scope. Glycopyrrolate (0.2 - 0.4 mg im) is a good drying agent. It does not cross the blood brain barrier and causes less tachycardia than atropine.

Medications may be prescribed to decrease the gastric volume and acidity preoperatively, which, in turn, may decrease both the risk and severity of perioperative aspiration of gastric contents (see Chapter 25 Unusual Anesthetic Complications: Aspiration). A non-particulate antacid, such as 0.3 M sodium citrate 30 mL po, may be used to neutralize the gastric acid. A prokinetic drug, such as metochlorpropamide 10 mg intravenously, may be administered to facilitate gastric emptying. Medications, such as an H2 blocker, may be given by mouth 1 hr prior to surgery (e.g., ranitidine 150 mg). Alternatively, patients may be asked to take their own usual medications (e.g., omeprazole or pantoprazole) prior to surgery.

Gabapentin and pregabalin are gabapentinoid compounds with sedative, analgesic, and anticonvulsant properties, and they are commonly prescribed in patients with neuropathic pain (see Chapters 17 & 18). Surgical injury initiates a cascade of effects on both the peripheral and central pain pathways, which may result in a “pathological” mode of processing afferent pain information in the postoperative period. Promising results have arisen from studies using gabapentin and pregabalin for the postoperative management of pain. Pregabalin has also been used prior to surgery (off-label indication) with the hope of improving postoperative pain management.

A recent study using pregabalin 75 – 300 mg po prior to surgery failed to show any benefit with respect to a reduction in preoperative anxiety, improvements in postoperative pain, or improvements in postoperative recovery following minor elective surgery. In this study, the patients who received pregabalin 300 mg preoperatively experienced more sedation prior to surgery as well as 90 and 120 min after surgery.⁵ In another study of a single dose of pregabalin 150 mg administered preoperatively in patients undergoing laparoscopic cholecystectomy, results showed an improvement in postoperative pain at rest and with activity, a reduction in opioid consumption, and no increased side effects.⁶ A systematic review showed that preoperative administration of gabapentin and pregabalin reduced postoperative pain, opioid use, and opioid-related adverse effects without major risks.⁷ Conclusions about the optimal dose and duration of the treatment could not be determined due to the heterogeneity of the studies. The role of these medications in the preoperative period continues to be studied.

Acetaminophen and a nonsteroidal anti-inflammatory drug (NSAID) may be prescribed preoperatively in an attempt to establish a foundation of analgesia for postoperative pain management (see Chapter 17 Acute Pain Management). A recent meta-analysis found that acetaminophen reduced postoperative morphine requirements significantly, but it had no effect on the incidence of morphine-related adverse side effects.⁸ A cochrane review in 2008 found that a single dose of acetaminophen (adults) significantly reduced postoperative pain.⁹ In adults, acetaminophen 975 mg may be prescribed with sips of water on call to the operating room.

In meta-analysis, preoperative NSAIDs were found to decrease postoperative nausea, vomiting, and sedation by 30%.¹⁰ NSAIDs have a 30 – 50% sparing effect on morphine consumption. In this review, morphine consumption was found to correlate with the incidence of nausea and vomiting, and pruritus, urinary retention, and respiratory depression were not significantly decreased by NSAIDs. A systematic review in children undergoing tonsillectomy found no significant increase in bleeding associated with the perioperative use of NSAIDs and a significant reduction in nausea and vomiting with the preoperative use of NSAIDs (odds ratio 0.49; 95% CI 0.29 to 0.83).¹¹ Provided there is no contraindication to its use, a NSAID (e.g., celecoxib 200 - 400 mg for an adult) may be given at the same time as acetaminophen.

Other special premedications may include: supplemental oxygen, antibiotics, steroids, antihistamines, beta-blockers, bronchodilators, antacids, insulin. Students should ask their staff anesthesiologists when and why they would prescribe these medications.