The instruction to be “nil per os,” commonly shortened to NPO, is a standard and often confusing directive given to patients preparing for medical procedures. Derived from Latin, the phrase translates to “nothing by mouth,” signifying a complete restriction on oral intake. This requirement is especially common before any procedure involving anesthesia or deep sedation. The most frequent question patients ask about this strict rule is whether or not water is included in the restriction.
Defining NPO and the Standard Water Restriction
Under a standard, traditional NPO order, water is strictly prohibited for a designated period before a procedure. The medical instruction of “nothing by mouth” is historically interpreted literally, encompassing all liquids, including seemingly harmless sips of water. The purpose is to ensure the stomach is as empty as possible before the administration of sedatives or anesthetics.
Even a small volume of water can violate this order and potentially lead to a delay or cancellation of a scheduled procedure. While fasting from solid food is often eight hours, the restriction on liquids, including water, typically extends up to four to eight hours, depending on the specific protocol and procedure type.
The Critical Medical Reason Behind NPO Orders
The NPO rule prevents pulmonary aspiration, a life-threatening complication. Aspiration occurs when stomach contents, whether solid food or liquid, are regurgitated and accidentally enter the lungs instead of the esophagus. This risk is much higher when a patient is under general anesthesia or deep sedation.
Anesthesia medications suppress the body’s protective reflexes, most notably the gag reflex and the ability to cough effectively. If stomach contents are present and regurgitation occurs, the absence of these reflexes allows the material to easily enter the airway and lungs. This can cause aspiration pneumonitis, a severe chemical injury to the lung tissue due to stomach acid, or aspiration pneumonia, a serious infection.
While water itself is not acidic, consuming any liquid adds to the total volume of contents in the stomach. Even clear fluids can increase the risk of regurgitation and subsequent aspiration into the lungs when the protective reflexes are suppressed. Minimizing this volume is paramount for the anesthesiologist to ensure a safe procedure.
Situations Where NPO Orders May Be Modified
NPO guidelines are not always absolute, and modern medical practice uses more flexible, evidence-based protocols. Current guidelines from groups like the American Society of Anesthesiologists (ASA) recommend that healthy patients undergoing elective procedures may consume clear liquids up to two hours before anesthesia. Clear liquids include water, black coffee, clear tea, and pulp-free juices.
This modification recognizes that prolonged fasting can cause patient discomfort, dehydration, and increased insulin resistance, potentially hindering recovery. However, any deviation from the standard NPO instruction must be explicitly approved and directed by the care team, typically the anesthesiologist or surgeon. Patients with certain conditions, such as diabetes, delayed gastric emptying, or those taking specific medications, may require longer fasting times.
In specific circumstances, a small sip of water may be permitted to take necessary oral medications on the morning of surgery. The medical team will provide precise instructions on the exact amount allowed. Patients must never unilaterally decide to modify their NPO status, as doing so can lead to a procedure being postponed or canceled for safety reasons.
Practical Application: Other Items Excluded Under NPO
The “nothing by mouth” rule extends beyond food and water to include several other items that patients frequently overlook. Chewing gum and hard candies are strictly excluded because the act of chewing and sucking stimulates the production of stomach acid and saliva. This increased volume and acidity in the stomach elevates the risk of pulmonary aspiration during the procedure.
Lozenges, mints, and smokeless tobacco products also violate the NPO order. Even simple activities like brushing teeth must be done carefully, with patients instructed to spit out any water and avoid swallowing it. The overall goal is to ensure the stomach remains entirely quiescent, with no stimulation or addition of any substance before anesthesia is administered.