While preparing for my recent knee surgery I was given a lot of instructions. Where to park, how to dress, when to arrive, what to bring and even what (not) to eat and drink. Like many surgical patients, I was given a time after which I was no longer allowed to eat and a different time after which I was not allowed to drink clear fluids.
Being a Diet Coke lover, I immediately wondered what it is about brown, opaque Diet Coke that makes it not OK to consume close to surgery. What is it about clear, colourless Sprite that makes it fine? As a more direct comparison, why would white grape juice be OK but not purple grape juice? I wondered if somehow the dyes in the drinks could interfere with surgical imaging or complicate emergency procedures I could need like intubation. Maybe the colourings could affect my mouth, stomach or urine in a way that made surgery more difficult somehow.
If you鈥檝e already spotted the folly in my logic, you鈥檙e several hours faster than me. What I eventually realized is that I, and likely many patients put on a clear liquid diet, was fundamentally misinterpreting the word 鈥渃lear.鈥� While I heard 鈥渃lear鈥� as in colourless, what the doctor meant was clear as in transparent or free of small particles.
Once you realize the reasoning behind clear-fluid diets for surgical patients, it becomes obvious that non-cloudy is what doctors mean. But I, like most patients, wasn鈥檛 given the reasoning, only the instruction. So, allow me to explain to you what wasn鈥檛 explained to me: why food matter in the stomach during surgery can lead to pulmonary aspiration, and why clear fluids help prevent this.
In 1946 Curtis Mendelson published paper examining the details surrounding 66 women who, while giving birth, had some of their stomach contents travel into their lungs. Mendelson d that this aspiration was occurring while patients were under general anesthesia. While sedated their throat reflexes were inhibited, which allowed food matter from the stomach to travel up the esophagus and enter the trachea and lungs. In some cases, this resulted in the patient asphyxiating or choking to death, whereas in others it went undetected until after labour had been completed when it caused infections, pneumonia, and other pulmonary complications.
Thus, to help avoid pulmonary aspiration he several things, including that women in labour not be allowed to eat, as they might need to be unexpectedly placed under general anesthesia. These recommendations have been adjusted and refined in the last 74 years, but Mendelson鈥檚 main direction, that those preparing to be sedated should fast, has stuck.
The reason clear, particulate-free liquids are allowed when eating聽isn't has to do with how quickly foods and drinks of different compositions leave the stomach. While food, especially fat- or protein-rich food, can take up to to leave your stomach, like coffee, water or pulp-free orange juice are or faster. Therefore, clear fluids can be safely consumed up until two hours before surgery. This is true for almost all patients, including those who are , , or .
Thus, patients should be allowed to freely consume clear fluids like apple juice, coffee, Gatorade, tea (with no or ), or , up to two hours before surgery. This practice has some obvious benefits. For one, patients are less thirsty. I was given the traditional 鈥渘il par os鈥� after midnight order (NPO, Latin for 鈥渘othing by mouth鈥�) but because my operation took place in the early morning, I only went about three hours without water. Nonetheless, I still felt quite parched. When I woke up after my surgery the very first thing I asked was if I could have a drink.
However, if a patient is scheduled for afternoon surgery and given an NPO order, they could be going 12 hours or more without drinking. That鈥檚 not fun for anyone, but for the elderly or those with medical conditions, it could be quite harmful. For children or infants, going several hours without fluids can increase their discomfort and make them grumpy or upset, making the lives of parents, and the jobs of nurses, surgeons, and anesthesiologists more difficult.
Beyond patient comfort, allowing clear fluids, and specifically giving patients a carbohydrate-rich beverage preoperatively, can avoid developing insulin resistance and possibly lead to . There鈥檚 also evidence that unrestricted access to clear fluids preoperatively can of nausea after surgery. Plus, as article points out, given that saliva production and gastrointestinal secretions lead to about 2 milliliters of liquid entering your stomach per minute anyways, small sips of water will hardly make a large difference in the gastric volume of a patient.
So, there鈥檚 a good reason that you can鈥檛 eat before surgery, namely, pulmonary and . But if there鈥檚 no good reason to avoid drinking until two hours before surgery, why do so many hospitals still prevent patients from drinking for more hours than necessary?
Well, doctors likely believe that simpler instructions such as 鈥渟top eating and drinking at midnight鈥� are easier to follow for patients than 鈥渟top eating and drinking non-clear fluids at midnight and stop drinking clear fluids at 6 a.m.鈥� They may have never questioned the standard NPO order or have seen by organizations like the 锘緾anadian Anesthesiologists鈥� Society.
But perhaps most importantly, because doctors are being needlessly cautious. Even though an abundance of evidence tells us that clear fluids are gone from the stomach within two hours, they鈥檇 rather leave a bigger window just in case. However, the negative consequences of leaving this window have to be considered too. When they are, and when the research is examined critically by experts, the are two-hour that all hospitals .
Next time I have surgery, if there is a next time, I will definitely be questioning any NPO orders I get, and I鈥檇 encourage any medical professionals reading to inquire into the fasting protocols at their hospitals. Maybe there鈥檚 a good reason that a doctor wants a patient to fast for longer than recommended, but it should not be standard practice.
To read about how, in the end, I didn't need to be fasting at all, click here!
