Monday, December 26, 2011

The Anesthesia-Chicken Biscuit Quandary: Maybe Mom Was Right After All?

     Before leaving work on Friday, I glanced at the outpatient schedule for tomorrow, which will be my first day back at work following a wonderful, three day Christmas break. It's the typical end-of-the-year rush, where everyone is getting their elective procedures done before the insurance deductibles kick back in. I'm the "late" person, which means I'll be there till the last patient goes out the door tomorrow evening. We're running all six operating rooms, primarily orthopedic and gynecologic cases, most of which will be done with a combination of general and ultrasound-guided regional anesthesia (nerve blocks). It's going to be a crazy day, and because surgeons sometimes need to add cases that weren't scheduled, it may be even more hectic.
     From an anesthetic standpoint, your primary concern with add-on cases lies in whether or not the patient has had adequate NPO time. NPO stands for nil per os, which in Latin means "nothing by mouth." Regardless of whether a patient is having sedation or general anesthesia, the risk of aspirating stomach contents into the lungs is a serious concern. Both types of anesthesia can result in the loss of protective airway reflexes. For instance, you know how you cough violently when you accidentally inhale a cookie crumb or a swig of Coke, and it goes down the wrong way? Anesthesia wipes out that biological safety mechanism, making it easy to upchuck residual food and liquid from the stomach, up through the esophagus, down past the trachea, and smack dab into the lungs. The consequences of aspiration can be life-threatening, ranging from mild respiratory distress to devastating lung injury with multi-organ failure. The American Society of Anesthesiologists has published a set of guidelines for NPO times, some of which are listed below.

      It is important for patients, peri-operative physicians, and anesthesia providers to appreciate that the guidelines in this box provide only a "down and dirty" summary of NPO times. In order to fully understand the ASA recommendations for pre-operative fasting, you must read the entire monograph (1). These guidelines apply to healthy patients of all ages, who are having elective procedures. Healthy patients are those with an ASA I physical classification (2), and include those who are neither very young (newborns) nor very old (advanced age) with good exercise tolerance and no organic, physiologic, or psychiatric disturbances. (2) Unfortunately, this excludes the majority of our population here in the United States. An overwhelming majority of my patients are morbidly obese, who by definition have a body mass index (BMI) of greater than 40 kilograms per meter squared, or a BMI of 35 kg/m2 with concomitant obesity-related conditions, such as hypertension or diabetes. (3) To help put morbid obesity into perspective, a normal BMI is 20-25 kg/m2. Morbidly obese patients are NOT healthy, even if they haven't yet developed high blood pressure or diabetes yet, and they all warrant an ASA III physical class designation in my book. An ASA III is a person who is functionally limited by one or more severe systemic diseases, which is not immediately life-threatening.  These are patients with morbid obesity, a prior history of heart attack or chest pain that is stable, poorly controlled high blood pressure or diabetes without end organ failure, chronic renal failure, and controlled COPD or congestive heart failure. (2)
     Moving right along, these pre-operative fasting guidelines "are not intended for women in labor"; parturients are an entirely different breed of patient. When you have a laboring patient, there are two people you have to worry about: mom and baby. I assign most pregnant patients an ASA II physical status; if they have a pregnancy-related condition with severe systemic effects, such as pre-eclampsia, or if they abused tobacco, alcohol, or other drugs during the pregnancy, or were morbidly obese pre-pregnancy, they get a III. An ASA II is a patient with no functional limitations from a mild systemic disease, such as those who are overweight or mildly obese, smokers without COPD, controlled high blood pressure or diabetes, and pregnancy. (2) That's right, pregnancy IS a disease! Pregnancy is accompanied by a whole slew of physiologic derangements, not the least of which is altered gastric motility and delayed gastric emptying. Virtually every organ system, including the woman's airway anatomy, is affected by pregnancy. These patients represent a unique challenge to anesthesiologists and anesthesia providers because they are highly prone to aspiration under general anesthesia.This is why we use regional anesthesia, such as spinals and epidurals, for laboring patients who require C-sections.
     Now for the kicker, the part of the guidelines which is often conveniently ignored by both anesthesiologists and surgeons alike, the two considerations which, for some reason, are not listed in the box above. To reiterate, these NPO guidelines specify healthy patients, undergoing elective procedures. Common sense dictates that patients with co-morbidities, especially those known to be associated with neurological or mechanical delays in gastric emptying or altered sphincter tone, such as diabetes or a prior history of gastric or esophageal surgery, as well as patients who have difficulty swallowing or gastro-esophageal reflux disease or any patient where there is concern about a difficult airway, necessitate additional consideration. For patients affected by these conditions, the guidelines recommend longer NPO times, e.g. eight hours or more. (1) Additionally, the ASA consensus panel strongly agrees that meals consisting of solid foods which contain meat or are fried or fatty warrant eight hours or  more of pre-operative NPO time. (1)
     I cannot tell you how many times I have questioned patients about when they last ate, only to find that he or she consumed a piece of Grandma's fried chicken or a bacon-sausage-egg biscuit or a couple of doughnuts six hours or less before their scheduled procedures. For me, that's a deal-breaker, and the surgery will be postponed. The ASA guidelines were written by a panel of experts for a reason: to protect our patients from the risk of aspiration which is inherent in every anesthetic. Paying attention to the guidelines is more about doing what is right for our patients, and less so about covering our asses.
     In general, most of us adhere to these guidelines pretty tightly; others, not so much. For instance, I've heard of colleagues who are quoted as saying, "Down here in the South, a doughnut and a glass of milk are clear liquids." I certainly hope they are only joking. On the other end of the spectrum, I've been accused of being too rigid with these guidelines, despite the fact that, in almost 7 years of practice, I have rarely had to cancel a case for insufficient NPO status. Here's a scenario to consider. A two year old child has a lower-extremity abscess that needs to be drained. The child is playful, not acutely ill or toxic-looking, meaning that the surgery is semi-urgent, or closer to being elective than emergent. Because of the fact that the child is only two, and will not likely tolerate incision and drainage of the abscess at the bedside, he will need a general anesthetic. You learn that the child consumed a chicken biscuit 5 1/2 hours ago. As an anesthesiologist or anesthesia provider, what would you do? If you were the child's parent, would you rather hear your anesthesiologist tell you, "Oh, he'll be fine. We're close enough. Let's just proceed with the case." or "Why don't we give that chicken biscuit a couple more hours to fully digest before we put little Tommy 'to sleep'?" Judgment calls can be a bitch, and that's part of what makes being an anesthesiologist so stressful. Some of us are comfortable, flying by the seats of our pants. Through either the mystical power of clairvoyance or more probably, sheer dumb luck, there are those among us who seem able to "cut corners" without experiencing a bad anesthetic outcome. I'm not there yet, nor do I ever intend to be. I'm a big fan of the age-old, tried-and-true axiom: "An ounce of prevention is worth a pound of cure." Why would I want to play with fire where a human life is at stake? My Mom always told me, "It's better to be safe than sorry!"and although I hate to admit it, this is one piece of advice where I'm pretty darn sure she's right.
ASA Practice Guidelines for Preoperative Fasting
ASA Physical Classification System
What is Morbid Obesity?

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