Premedication of the Surgical Patient
An extremely anxious 17-year-old woman presents for dilation and curettage. She demands to be asleep before going to the operating room and does not want to remember anything.
What are the goals of administering preoperative medication?
Anxiety is a normal response to impending surgery. Diminishing anxiety is usually the major goal of preoperative medication. For many patients, the preoperative interview with the anesthesiologist allays fears more effectively than sedative drugs. Preoperative medication may also provide relief of preoperative pain or perioperative amnesia.
There may also be specific medical indications for preoperative medication: prophylaxis against postoperative nausea and vomiting (5-HT3s) and against aspiration pneumonia (eg, antacids), prevention of allergic reactions (eg, antihistamines), or decreasing upper airway secretions (eg, anticholinergics). The goals of preoperative medication depend on many factors, including the health and emotional status of the patient, the proposed surgical procedure, and the anesthetic plan. For this reason, the choice of anesthetic premedication must be individualized and must follow a thorough preoperative evaluation.
Do all patients require preoperative medication?
No—customary levels of preoperative anxiety do not harm most patients. Some patients dread intramuscular injections, and others find altered states of consciousness more unpleasant than nervousness. If the surgical procedure is brief, the effects of some sedatives may extend into the postoperative period and prolong recovery time. This is particularly troublesome for patients undergoing ambulatory surgery. Specific contraindications for sedative premedication include severe lung disease, hypovolemia, impending airway obstruction, increased intracranial pressure, and depressed baseline mental status. Premedication with sedative drugs should never be given before informed consent has been obtained.
Which patients are most likely to benefit from preoperative medication?
Some patients are quite anxious despite the preoperative interview. Separation of young children from their parents is often a traumatic ordeal, particularly if they have endured multiple prior surgeries. Medical conditions such as coronary artery disease or hypertension may be aggravated by psychological stress.
How does preoperative medication influence the induction of general anesthesia?
Some medications often given preoperatively (eg, opioids) decrease anesthetic requirements and can smooth induction. However, intravenous administration of these medications just prior to induction is a more reliable method of achieving the same benefits.
What governs the choice among the preoperative medications commonly administered?
After the goals of premedication have been determined, the clinical effects of the agents dictate choice. For instance, in a patient experiencing preoperative pain from a femoral fracture, the analgesic effects of an opioid (eg, fentanyl, morphine, hydromorphone) will decrease the discomfort associated with transportation to the operating room and positioning on the operating room table. On the other hand, respiratory depression, orthostatic hypotension, and nausea and vomiting may result from opioid premedication.
Benzodiazepines relieve anxiety, often provide amnesia, and are relatively free of side effects; however, they are not analgesics. Diazepam and lorazepam are available orally. Intramuscular midazolam has a rapid onset (30 min) and short duration (90 min), but intravenous midazolam has an even better pharmacokinetic profile.
Which factors must be considered in selecting the anesthetic premedication for this patient?
First, it must be made clear to the patient that in most centers, lack of necessary equipment and concern for patient safety preclude anesthesia being induced in the preoperative holding room. Long-acting agents such as morphine or lorazepam are poor choices for an outpatient procedure. Diazepam can also affect mental function for several hours. One alternative is to establish an intravenous line in the preoperative holding area and titrate small doses of midazolam using slurred speech as an end point. At that time, the patient can be taken to the operating room. Vital signs—particularly respiratory rate—must be continuously monitored.