Understanding Premedication: Preparing for Anaesthesia

Many people associate "premedication" with a tablet or injection to induce calmness. However, the term encompasses all medications prescribed before anaesthesia and surgery. These medications serve multiple purposes, including reducing anxiety, managing pain, minimising the risk of aspiration (inhaling stomach contents into the lungs), preventing postoperative nausea and vomiting, and reducing the potential for infection. While historically administered via injection, most premedications are now available in tablet or liquid form, offering greater flexibility and patient comfort.

Sedatives: Managing Anxiety and Promoting Relaxation

If you experience significant anxiety, discuss options with your anaesthesiologist or surgeon. Historically, a variety of drugs were used to alleviate preoperative anxiety, including barbiturates and antihistamines. Today, benzodiazepines like midazolam, temazepam, or diazepam are commonly prescribed. This may involve a single tablet the night before, a prescription for home use, or administration upon arrival at the hospital. However, some patients may not receive sedation, allowing them to remain in control for as long as possible. Studies suggest that patients without sedation often recover from anaesthesia more quickly. Older patients and those with memory concerns may experience prolonged sleepiness and cognitive impairment with sedation, making it less desirable. Your preferences will be carefully considered.

Pain Management: Preoperative and Intraoperative Relief

Historically, pain relievers like pethidine were often administered via injection to reduce anxiety and supplement anaesthesia. Some procedures, particularly open-heart surgery, may involve a combination of sedative and pain-relieving injections to ensure calmness and minimise cardiac stress. Contemporary practice generally reserves pain medication administration for the operating room, unless significant pain is already present. If you are taking opioid pain medications, it's crucial to inform your anaesthesiologist, as this information will guide their medication choices during and after surgery. (See also ‘Postoperative pain relief’.)

Antacids: Preventing Aspiration

A critical aspect of premedication involves preventing aspiration of gastric acid, a potentially life-threatening complication. Aspiration can lead to immediate suffocation from undigested food particles and delayed pneumonia from acid damage to the lungs. Several drug classes are employed to mitigate this risk:

• Acid Production Inhibitors: Medications like cimetidine or ranitidine (H2 receptor-blocking agents) reduce acid production in the stomach.
• Acid Neutralisers: Sodium citrate, taken orally, neutralises stomach acid, increasing the pH. Its clear liquid form minimises the risk of lung damage if aspirated.
• Gastric Emptying Accelerators: Metoclopramide increases the rate at which the stomach empties into the small intestine, reducing the volume of fluid in the stomach.

The use of these medications is individualised. For example, a caesarian section may warrant sodium citrate, while patients with a hiatus hernia or heartburn may benefit from H2 receptor blockers. Obese individuals, who often have larger volumes of highly acidic stomach contents, may receive all three types of medication.

Antiemetics: Reducing Postoperative Nausea and Vomiting

Antiemetics are now routinely administered to prevent postoperative nausea and vomiting, particularly for patients with a history of these complications. These medications can be administered intravenously or orally, with ondansetron being a common example.

Antibiotics: Prophylactic Infection Prevention

Your surgeon may prescribe prophylactic antibiotics to reduce the risk of infection. This is common for major procedures like hip replacements and even some minor procedures like hernia repairs, and when implanting devices like pacemakers. While the anaesthesiologist may not typically order these antibiotics, they may prescribe them if you have heart valve problems. The timing of antibiotic administration varies, with some given in the hour before surgery and others administered by the anaesthesiologist at the start of anaesthesia.

Important Considerations

Your anaesthesiologist will carefully assess your individual needs and medical history to determine the most appropriate premedication regimen. Open communication about your concerns and preferences is essential for a safe and comfortable surgical experience.