One of the important events during the preoperative phase of the surgical experience is the administration of preoperative medications. Not only are anesthetics administered during this time, but so as drugs that minimizes respiratory tract secretions. Medicating the client pre-procedure to reduce anxiety and promote relaxation may also be necessary.
Before discussing about the preoperative medications that are used the nurse should obtain a medication history. This eliminates the possible life-threatening effects of drug interactions and allergic reactions to certain medications. During a medication history the following are done:
- Document any medication the patient is using or has used in the past including over-the-counter (OTC) preparations and the frequency with which they are taken.
- The anesthesiologist evaluates the potential effects of prior medication therapy and considers the length of time the patient has used the medications, the patient himself and the nature of the proposed surgery.
Medications that cause particular concerns are the following:
- DO NOT discontinue these drugs abruptly before the surgery.
- If discontinued abruptly, the patient may suffer from cardiovascular collapse is he or she has been taking steroids for some time.
- Before and after the surgery, a bolus of steroid may be administered intravenously immediately.
During anesthesia administration, thiazide diuretics may cause excessive respiratory depression from an associated electrolyte imbalance.
These medications may increase the hypotensive action of anesthetics
Anesthetics have a hypotensive effect on the patient. Monoamine Oxidase inhibitors or MAOIs increase the hypotensive effects of anesthetics.
If medications such as diazepam, barbiturates and chlordiazapoxide are withdrawn suddenly anxiety, tension and even seizures may result.
When a patient undergoing a surgery is diabetic, interaction between anesthetics and insulin must be considered.
Neomycin, kanamycin and other “MYCIN” drugs may present problems when these medications are combined with a curariform muscle relaxation. Interruption of nerve transmission may occur and apnea due to respiratory paralysis may result when these drugs are combined.
Commonly Used Preoperative Medications
- Histamine H2 receptor Antagonist
Pharmakokinetics of Preanesthetic Medication
- Barbiturates or Tranquilizers/ Sedatives. These medications are commonly used for sedation. However, a visit to the client before the surgery has a more reassuring and calming effect than barbiturates. Hypnotics are usually prescribed the night before the surgery to allay insomnia. Drugs under this classification are:
- Pentobarbital (Nembutal)
- Secobarbital (Seconal Sodium)
- Benzodiazepines as hypnotics such as Flurazepam and Diazepam
- Opioids. To reduce the amount of general anesthetic required, opioid medications may be prescribed before an operation. Aside from that, these medications can also be given to produce analgesia in patients who have pain prior to surgery. However, it is important to know that doses of analgesic may depress the respiration and cough reflex not to mention the risk of respiratory acidosis and aspiration pneumonitis. Full doses of these medications may result to unpleasant effects such as hypotension, nausea and vomiting, constipation and abdominal distention. Some examples opioid drugs are the following:
- Morphine sulfate
- Meperidine (Demerol)
- Anticholinergics. To reduce the respiratory tract secretions and prevent or treat the severe reflex slowing of the heart during anesthesia, anticholinergic drugs should be given. Aside from that, these medications are also administered to counteract secretions that are anticipated with anesthetic induction and intubation. Examples of anticholinergic drugs are:
- Glycopyrrolate (Robinul) – often used because Atropine and Scopolamine and other belladonna alkaloids have varying effects on pulse rate. Robinul is a quarternay ammonium compound which is twice as potent as an anti-sialogogue, reducing secretions, and acts three times as long.
- M – Medications (preanesthetic) should be given from 45 minutes to 75 minutes before anesthesia is begun. Hence, the nurse should administer these medications accurately at the prescribed time. Otherwise, the effects of medications will be worn off or will not have begun to act when anesthesia is started.
- E – Encourage the patient to remain in bed with side rails up because the medication will cause lightheadedness and drowsiness.
- D – Directly observe the patient for untoward reactions to the medications.
- S – Surroundings are kept quiet to promote patient relaxation.