Anesthesia refers to the use of medications to induce a temporary state of controlled unconsciousness, lack of sensation, or muscle relaxation. Preparing the body for this process requires following specific instructions from healthcare providers. These pre-operative restrictions are carefully designed safety measures intended to minimize the potential for complications during the surgery and recovery phase.
Restrictions on Eating and Drinking
The most universally applied pre-operative instruction is the concept of “Nil per os” (NPO), which translates from Latin to “nothing by mouth.” This restriction exists to prevent a potentially life-threatening complication known as pulmonary aspiration. When a person is under general anesthesia, the protective reflexes that normally prevent stomach contents from entering the lungs are temporarily suppressed.
If the stomach contains food or liquids, stomach acid can be regurgitated and inhaled into the lungs during the induction of anesthesia. This can cause aspiration pneumonia, a severe form of chemical pneumonitis that leads to serious respiratory distress or death. Even small amounts of aspirated material pose a significant risk to lung function and gas exchange.
The required fasting period varies depending on the type of ingestion, reflecting how quickly different substances clear the stomach. For solid foods and fatty liquids, such as milk or orange juice with pulp, the required withholding period is typically eight hours before the scheduled procedure. This duration accounts for the slower gastric emptying time associated with complex nutritional intake.
The risk of aspiration is highest during the induction and emergence phases of general anesthesia when the airway is manipulated or protective reflexes are returning. Therefore, adhering to the eight-hour window for solids is a standard practice designed to minimize the volume and acidity of any potential gastric contents.
Clear liquids, which include water, plain black coffee, or apple juice without pulp, are generally cleared from the stomach much faster. Current guidelines often permit the consumption of these clear fluids up to two hours before the planned time of anesthesia induction. The allowance for a small volume of clear fluid helps maintain patient comfort and hydration without significantly increasing the risk of aspiration. However, patients should always confirm the exact timing with their anesthesiologist, as individual health conditions, such as gastroparesis or pregnancy, or specific surgical plans may necessitate longer fasting windows.
Medications and Supplements to Halt
Certain prescription and over-the-counter substances must be carefully managed before surgery because they can interact unpredictably with anesthetic agents or increase procedural risks. Blood-thinning medications, including antiplatelet drugs like clopidogrel and anticoagulants like warfarin, present a significant concern regarding the potential for excessive bleeding. These agents inhibit the body’s ability to form clots, which is a necessary function to control blood loss during the surgical incision and throughout the operation.
Patients taking these medications are typically instructed to pause them for a specific period, often several days, before the procedure, depending on the drug’s half-life and the type of surgery planned. This temporary cessation allows the body’s coagulation system to return to a safer, more functional level, which is particularly important for procedures involving significant tissue manipulation.
Diabetes medications, including insulin and oral hypoglycemic agents, also require careful adjustment to prevent metabolic complications while fasting. Since patients are not eating, continuing the usual dose of these medications can cause severe hypoglycemia, or dangerously low blood sugar, which can lead to seizures or brain injury. Maintaining adequate, but not excessive, blood sugar levels is a delicate balance during the pre-operative period.
The management plan usually involves reducing or omitting the dose of the diabetes medication and frequently monitoring blood glucose levels in the days leading up to and during the procedure. Conversely, high blood sugar, or hyperglycemia, can impair wound healing and increase infection risk, so treatment protocols are designed to keep glucose within a narrow, safe range.
Beyond prescription drugs, many herbal supplements, vitamins, and common over-the-counter pain relievers can also pose risks. Non-steroidal anti-inflammatory drugs (NSAIDs) like ibuprofen, along with high-dose Vitamin E and certain herbal products like ginkgo biloba, can inhibit platelet function and increase the risk of bleeding. Other supplements, such as St. John’s Wort, can interfere with the metabolism of anesthetic drugs, potentially altering their required dosage or duration of effect. Patients must provide a comprehensive list of everything they consume so the provider can determine which substances should be temporarily discontinued.
Substance Use: Alcohol, Nicotine, and Recreational Drugs
The habitual use of substances like alcohol, nicotine, and recreational drugs can significantly alter the body’s physiological response to anesthesia and surgery. Chronic, heavy alcohol consumption can lead to cross-tolerance with certain anesthetic agents, requiring the anesthesiologist to administer higher doses to achieve the desired effect. Furthermore, abruptly stopping alcohol intake before surgery can precipitate dangerous withdrawal symptoms in the post-operative period, complicating recovery.
Nicotine use poses direct risks to the respiratory and vascular systems. Smoking reduces the oxygen-carrying capacity of the blood and increases the likelihood of airway complications, such as laryngospasm, during the procedure. It also compromises circulation, which severely impairs wound healing and increases the risk of surgical site infections after the operation.
The use of recreational drugs, including cannabis, opioids, and stimulants, must be fully disclosed to the medical team. These substances can have profound, often unpredictable, interactions with anesthetic agents, potentially causing dangerous fluctuations in heart rate and blood pressure. For example, stimulants can increase the risk of cardiac arrhythmias, while chronic opioid use may necessitate higher pain medication doses post-surgery, requiring careful pre-operative planning.
Immediate Pre-Surgical Personal Restrictions
Certain personal items and applications must be removed immediately before the procedure to ensure patient safety and proper monitoring. All jewelry and body piercings should be taken off because metal can conduct electricity and cause skin burns if electrocautery devices are used. Metal objects can also interfere with clear imaging results if X-rays or magnetic resonance imaging (MRI) are required.
The application of nail polish, artificial nails, or heavy makeup can interfere with the function of monitoring equipment. Pulse oximeters, which measure the oxygen saturation in the blood, rely on a light signal passing through the fingertip, and polish can distort this reading. Similarly, heavy makeup can prevent EKG pads from adhering properly to the skin, compromising cardiac monitoring.
Items like dentures, contact lenses, and eyeglasses must be removed for security and safety reasons. Dentures can become dislodged and obstruct the airway during the process of placing a breathing tube for general anesthesia. Contact lenses and glasses are removed to protect the eyes and prevent damage, as patients will be unable to protect them while unconscious.