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Chapter: Essential Anesthesia From Science to Practice : Clinical management : Pre operative evaluation

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NPO status - Anesthesia Clinical management

During induction of general anesthesia, the gag reflex is necessarily abol-ished. Should the patient “choose” that most inopportune time to suffer gastro-esophageal reflux (or worse yet, emesis), there is a high likelihood the stomach contents could end up in the lung, causing a chemical pneumonitis or even acute suffocation from the lodging of solid particles in the bronchial tree.

NPO status

During induction of general anesthesia, the gag reflex is necessarily abol-ished. Should the patient “choose” that most inopportune time to suffer gastro-esophageal reflux (or worse yet, emesis), there is a high likelihood the stomach contents could end up in the lung, causing a chemical pneumonitis or even acute suffocation from the lodging of solid particles in the bronchial tree. In addition to pharmacologic means (see Pharmacology), we minimize this risk by having the patient report for surgery with an empty stomach. Patients are asked to refrain from eating solid foods for 6–8 hours prior to elective surgery. While there is evi-dence that clear liquid ingestion is cleared rapidly and not dangerous in those patients with normal digestion (it may even raise the pH of the stomach con-tents above the pH 2.5 danger zone), it remains customary to tell patients who are scheduled for an elective operation in the morning not to eat or drink any-thing for at least 6 hours (for infants about 2 to 3 hours) before the operation. If the patient is already in the hospital, we write the order “NPO after midnight”3 to achieve the same results. Here, we can also order “maintenance i.v. fluids” overnight to keep the patient hydrated. Therefore, on the day of surgery we ask every patient about their most recent intake of food and liquids. Avoid asking: “When did you have your last meal?” If the patient’s history identifies risk factors for aspiration, e.g., gastroesophageal reflex disease (GERD), diabetes, increased intra-abdominal pressure, hiatal hernia, and requires general anesthesia, we use a rapid sequence induction (see General anesthesia). Pre-operatively, we also con-sider pharmacologic means to reduce stomach volume and strengthen the lower esophageal sphincter with a prokinetic agent and/or raise gastric pH with H2 blockers or a proton pump inhibitor.

Many patients have not been fasting for several hours, or their stomach did not have time to empty. Labor pains, narcotics, or trauma can stop gastric peristalsis for hours on end. Of course, in the presence of an ileus, we assume the stomach not to be empty even if the patient had nothing by mouth for many hours or even days.


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