The administration of anesthesia, whether general, regional, or procedural sedation, requires careful preparation to maximize patient safety. Pre-operative instructions are designed to prevent complications such as pulmonary aspiration and adverse drug interactions that occur when the body is unprepared for the chemical and physiological changes induced by anesthetic agents. Aspiration, where stomach contents enter the lungs, is a significant risk when protective airway reflexes are suppressed during deep sedation or general anesthesia. Adherence to a medical team’s instructions minimizes these dangers, allowing for a smoother, more predictable surgical experience. These guidelines are general, and every patient must follow the specific directions provided by their anesthesiologist and surgical team.
Dietary and Fluid Restrictions (NPO Guidelines)
The most common pre-operative instruction is the “Nothing By Mouth” (NPO) rule, which directly addresses the risk of pulmonary aspiration. A full stomach increases the volume and acidity of material that can be regurgitated and subsequently inhaled if the airway is not protected. Inhaling stomach contents can lead to severe, life-threatening aspiration pneumonia.
Standard fasting guidelines recommend specific timing windows based on the type of ingestion. For adults and adolescents, solids, including fatty foods and meat, should be stopped at least eight hours before the scheduled arrival time for surgery. This extended period ensures the stomach is adequately emptied. Non-human milk or infant formula should be stopped at least six hours before the procedure.
Clear liquids are generally encouraged up to two hours before the procedure, as they pass through the stomach quickly. Clear liquids include water, black coffee or plain tea without cream or milk, and fruit juices without pulp, such as apple juice. Allowing clear liquids until two hours prior helps combat thirst without increasing the risk of aspiration. Patients with conditions that slow gastric emptying, like diabetes or obesity, may require longer fasting periods determined by the anesthesia provider.
Medications and Supplements That Must Be Adjusted
Many prescribed medications and over-the-counter supplements can interact dangerously with anesthetic agents or increase the risk of surgical complications. Patients must provide a complete list of all substances they consume to their medical team well in advance. Stopping any prescribed medication should only be done under the explicit instruction of a physician.
Blood Thinners
Blood thinners, including antiplatelet drugs like aspirin and anticoagulants like warfarin or apixaban, interfere with the body’s ability to form clots. This significantly increases the risk of excessive bleeding during the operation and recovery. Depending on the medication, these are often stopped between 24 hours and seven days before surgery. They are sometimes replaced with a short-acting injectable anticoagulant in a process called “bridging” to manage clot risk.
Diabetes Medications
Diabetes medications require careful management due to pre-operative fasting requirements. If a patient takes their usual dose of insulin or oral agents while fasting, their blood sugar could drop dangerously low, causing hypoglycemia. The plan for adjusting insulin and oral agents, such as metformin, is highly individualized and must be established with the prescribing doctor to maintain stable blood glucose levels.
Psychiatric Medications
Certain psychiatric medications, particularly Monoamine Oxidase Inhibitors (MAOIs), carry a high risk of adverse interactions with specific anesthetic agents. Combining MAOIs with certain opioids can lead to a severe reaction known as serotonin syndrome, characterized by high blood pressure, fever, and muscle rigidity. Selective Serotonin Reuptake Inhibitors (SSRIs) can also affect platelet function and increase the risk of serotonin syndrome when combined with other serotonergic agents.
Herbal and Dietary Supplements
Herbal and dietary supplements are often overlooked but pose serious risks due to their pharmacological activity.
- Garlic, ginkgo biloba, ginseng, and Vitamin E can inhibit platelet aggregation, increasing the risk of surgical bleeding.
- St. John’s Wort and Kava can affect the metabolism of anesthetic drugs, potentially prolonging sedation or interfering with the recovery process.
Most healthcare providers recommend discontinuing all herbal supplements at least two weeks before surgery to ensure they are fully cleared from the system.
Prohibiting Alcohol, Nicotine, and Recreational Drugs
Lifestyle substances must be strictly avoided before surgery due to their unpredictable effects on anesthetic requirements and recovery.
Chronic alcohol use can increase the amount of anesthetic medication necessary to achieve sedation because of altered liver enzyme activity. Alcohol consumption also strains the liver, which is responsible for metabolizing many anesthetic and pain-management drugs.
Nicotine and smoking negatively impact the respiratory system and wound healing. Smoking reduces the oxygen-carrying capacity of the blood by increasing carbon monoxide levels and causes irritation and swelling in the airways, making intubation and ventilation more difficult. Nicotine also constricts blood vessels, impairing circulation to the surgical site and delaying the healing process.
The use of recreational drugs, including cannabis and illicit substances, can lead to severe and unpredictable interactions with anesthetic agents. These substances affect the central nervous and cardiovascular systems, potentially causing dangerously high blood pressure, irregular heart rhythms, or stroke when combined with surgical stress and anesthesia. Patients must be honest with their medical team about all substance use to allow for appropriate adjustment of the anesthesia plan.
Physical Items to Remove Before Surgery
Removing certain physical items is a practical safety measure to prevent injury and ensure accurate physiological monitoring during the procedure.
All jewelry, including rings, necklaces, and body piercings, must be removed before entering the operating room. Metal items can conduct electricity if electrocautery devices are used near the patient. This electrical conduction can result in severe skin burns, even if the metal is not directly at the surgical site.
Cosmetics like makeup, nail polish, and artificial nails must also be removed. The anesthesia team monitors nail beds and lips for signs of poor circulation or low oxygen saturation. Nail enhancements and dark polish interfere with the function of the pulse oximeter, a device used to measure blood oxygen levels. Removable dental work, such as dentures or partial bridges, must be taken out to prevent them from becoming dislodged and obstructing the airway during intubation for general anesthesia.