PICO Paper
Charles J. Adler
NURS 612: PICO Paper
Prof. Pam Kallmerten RN, MSN, CNL
University of New Hampshire
March 27th, 2015
A traditional preoperative instruction given to patients is to remain NPO after midnight.
The rationale behind this is to prevent gastric aspiration and potential fatality in the OR. Though
this is a severe concern, the incidence of this event is quite rare. This recommended instruction
has been preserved by tradition and ritual as opposed to evidence. With support from up to date
reviews and clinical trials, a more “flexible” NPO alternative diet has been introduced in attempt
to address symptoms that clients have reported in the preoperative and postoperative periods.
The goal is to understand the difference between prolonged fasting and the intake of clear liquids
with carbohydrates before surgery. To determine the effectiveness of these interventions in
reducing incidence of aspiration and accompanying complications, evidence will be gathered,
synthesized, and appraised under the criteria of maintaining patient safety and striving for
optimal wellness in clients electing surgery.
Keywords: NPO after midnight, Clear Liquids/CHO, Gastric aspiration, Post Op
In adult preoperative patients scheduled for surgery in the OR, what are the effects of a
“strict” NPO diet after midnight to reduce incidence of intraoperative aspiration and
other pre and postoperative complications, compared to a “flexible” NPO diet consisting
of clear liquids and intake of carbohydrate rich solutions?
Compared to…
Preoperative adult patients scheduled for next day
“Strict” NPO after midnight before surgery
“Flexible” NPO with clear liquids and CHO
before next day surgery
Reduced incidence of intraoperative aspiration,
pre and postoperative complications
Background & Rationale
Patients who are scheduled for surgery will often be instructed to withhold the intake of
food or liquids the night before their elective procedure. Traditionally, surgeons will recommend
this instruction to begin after midnight the night before the surgery. This order is often seen in
expression as “NPO”, “Nothing by mouth”, or “nil per os”. Conventionally, this order was given
to patients to reduce the risk and incidence of gastric aspiration under the induction of anesthesia.
Mendelson’s syndrome, or aspiration pneumonitis, is an anesthesia related complication that is a
rare event in today’s hospitals (Webster & Osborne, 2014). Though its incidence is uncommon,
the regurgitation of stomach contents into the lung can be a fatal consequence. Mechanically,
the swallowing mechanisms including pharyngeal and laryngeal nerve reflexes are temporarily
seized due to anesthetic induction (Oshodi, 2004). While the patient is in a state of stupor, all
voluntary and involuntary swallowing capabilities are halted, placing the patient at a high risk for
gastric regurgitation and aspiration if stomach contents are present. Theoretically speaking, this
is why the order to maintain NPO after midnight is so important because it is believed that the
optimal approach to reducing aspiration risk is ensuring an empty stomach on the day of surgery
(Crenshaw, 2011).
To ensure maximum safety regarding the fatal risk of intraoperative aspiration, NPO
guidelines after midnight have been conservatively enforced. With such strict and prolonged
fasting times for patients, it is evident that many clients experience great discomfort with this
request, reporting symptoms such as hunger, dizziness, headaches, and irritability before surgery
(Reimer-Kent, 2010). In addition to subjective patient reports, excessive fasting can also extend
patient stay in the hospital and delay post-operative recovery (Romit & Mortel, 2011). Contrary
to the standard preoperative order of NPO after midnight, the American Society of
Anesthesiologists (ASA) established guidelines in 1999 that favor more flexible fasting options
before surgery. These options include the intake of clear liquids up to two hours before surgery
and the intake of a carbohydrate rich solution both to promote gastric emptying, assist in postoperative recovery, and overall reduce the incidence of gastric aspiration (Apfelbaum, 2011).
Operative interventions such as differing preanesthesia fasting instructions are important
to implement with support from evidence and clinical significance. Evidenced based practice is
the backbone of most nursing interventions that are instilled in the clinical setting. A paradigm
such as this exemplifies the importance of patient safety and achieving optimal client outcomes
based on empirical data and literature reviews. It is here that differing preoperative fasting
interventions will be compared and assessed using evidence, clinically significant appraisals, and
client trials to conclude the most appropriate fasting intervention that will ensure intraoperative
safety, optimal wellness, and quickened post-operative recovery in patients electing surgery.
Search Methods
To retrieve information regarding preoperative fasting and diet alternatives, the primary
database used was the Cumulative Index to Nursing & Allied Health Literature (CINAHL). The
following are key words that were inputted into CINAHL database: “NPO”, “surgery”, “NPO
after midnight”, “preoperative fasting”, and “Mendelson’s syndrome”. In combination, these
terms yielded over 50 results, including analyses, reviews, and academic journals. To narrow
this list, limit conditions were placed on the search, only allowing for full text reviews, imbedded
references, publication 2000 to 2015, and English language. The new search with limits yielded
roughly 20 results that were relevant and applicable to the nursing interventions.
When gathering citations, it is important to collect only those that adhere to inclusion
criteria that is established by the searcher. For this compilation, citations were gathered only if
they acknowledged the legitimacies of ASA preoperative fasting guidelines, which included
fasting for 2 hours after ingesting clear liquids, 4 hours after breastmilk, 6 hours for infant
formula, nonhuman milk, and or a light meal, and 8 hours for a “dense” meal containing fried or
fatty foods (Apfelbaum, 2011). In addition to fasting criteria, the citations used must also have
strictly featured adults in its trials electing surgery as opposed to an emergent procedure. The
trials searched must also have contained data regarding the evaluation and comparison of
preoperative fasting alternatives, such as clear liquids and carbohydrate solutions, which would
promote client safety and compliance. Furthermore, only evidence based reviews and clinically
significant appraisals were accepted regarding the incidence of intraoperative gastric aspiration
and potential postoperative complications. (Exclusion criteria included studies involving
pediatric surgeries, emergent procedures, unsourced appraisals, and unreferenced reviews.)
Search engines such as Google Scholar and “UpToDate” were utilized to assist in a
pathophysiological understanding of gastric aspiration and recognizing NPO guidelines.
Between search engines and databases, the estimated number of included citations range from
12-15. Few citations highlighted clinically controlled trials, while others presented evidence to
promote the elimination of NPO after midnight. With each satisfying the inclusion criteria,
citations were analyzed and appraised in relevance to the posed PICO question of determining
the most appropriate nursing intervention to achieve the stated desired outcome.
Critical Appraisal of Evidence
The first citation to be appraised originates from Spain’s Hospital Nutrition Magazine,
presented as a scientific journal of health science. The research journal was accessible in
English, meeting the necessary inclusion criteria. As reflected in the subtitle, this “double-blind,
controlled, and randomized clinical trial” targets preoperative fasting to include the ingestion of a
carbohydrate rich solution with glutamine components up to 2 hours before anesthetic induction
of elective laparoscopic cholecystectomies (Borges Dock-Nascimento et al., 2011). To
determine the safety of this “abbreviated” fasting ritual, a nasogastric tube is inserted to measure
the residual gastric volume (RGV) of stomach contents after being anesthetized. RGV is
ultimately determined by the predicted evacuation of the stomach and the emptying rates in
which fluids are guided to the small intestine via peristalsis (Crowley, 2014). 56 women
participated in randomized control trials. Women were randomly assigned to either adhere to a
traditional fasting of 8 hours before surgery (n=12), drink a placebo of water the evening before
and 2 hours prior to surgery (n=12), drink a carbohydrate solution (n=12), or drink a glutamine
mixture (n=14) both following the same fluid guidelines as the placebo. After a few surgery
cancellations and participant refusals, 50 women completed the trial. Results suggest that no
participants had suffered from intraoperative gastric regurgitation or significant postoperative
complications. With the determined RGV in the varying fasting alternatives, it was found that
each intervention produced a similar volume of gastric contents with a median range between 080mL of fluid. No one intervention consistently produced a RGV of 0mL, nor did an
intervention consistently exceed 80mL. It is concluded that the ingestion of clear liquids,
carbohydrate solutions, and glutamine mixtures (when concentrated and measured according to
this trial) 2 hours before surgery will not increase RGV, nor will it rise the incidence of gastric
aspiration when under anesthesia, deeming it a safe practice.
Strengths of this trial include its physiological focus on gastric emptying and its direct
relationship with RGV. It also emphasizes the importance of varying evacuation rates based on
fluid consistency. In the discussion analysis section of the article text, it announces the potential
benefits of ingesting a carbohydrate/glutamine solution in regards to postoperative recovery and
complications. Though it is solid in its experimental trials, the study is restricted in its surgical
criteria, meaning it lacks experimentation in more diverse surgeries beyond gall bladder removal.
Additionally, this clinical trial only targets women undergoing this surgery. This gender bias is
considered a weakness in its product, excluding the male population with potentially differing
RGV and incidence of complication. The weaknesses of the trial may or may not have been
responsible for such uniform results among trial groups. Statistically, a 5% significance level
was accepted with a corresponding p value of 0.29, proving results to be statistically
insignificant, allowing for a retained null hypothesis (all interventions are equal in outcome or
difference happened by chance).
A second citation found addresses preoperative fasting and carbohydrate loading before
surgery. As acknowledged in the article’s title, the evidence which has been gathered for
decades regarding preoperative fasting has yet to be implemented in today’s practice. It is
understood that a prolonged fasting time for a pre-surgical patient could consequent a variety of
discomforts including hunger, thirst, dizziness, drowsiness, and anxiety (Crenshaw, 2011).
These symptoms would manifest before surgery, only exacerbating the patient’s own anxieties
regarding the procedure. To measure these somatic reports and the incidence of other
complications such as insulin resistance, dehydration, muscle wasting, hyperglycemia, and
impaired immune function, a qualitative study was performed in Sweden, targeting patients
scheduled for abdominal surgery. A double blind, randomized control trial incorporated 252
Swedish adult patients, each assigned to either a traditional 8 hour fast, a placebo group to ingest
water, or a group told to ingest a carbohydrate rich clear beverage the night and 2 hours before
surgery. After about an hour into anesthesia, stomach contents were aspirated and analyzed. No
significant difference in RGV was found between participants and their corresponding
preoperative diet. Results show that clients who ingested the carbohydrate rich solution reported
significantly less symptomatic distress before induction. Those participants in the placebo and
NPO after midnight groups reported higher incidences of thirst, hunger, and anxiety before going
under anesthesia. According to Borges Dock-Nascimento et al. (2011), a carbohydrate rich
beverage in the preoperative period may also decrease the body’s catabolic stress response to
surgery, promoting a speedy recovery in the postoperative setting.
This trial is strong by targeting preoperative symptoms and postoperative recovery after
the intake of a preoperative diet. It is important to address discomforts going into surgery for
they could ultimately affect the patient’s recovery. The research, however, failed to provide
details in the methods in which qualitative data was recorded and whether surveys were
conducted to ask clients to describe their anxiety, etc.
Evidence Synthesis
Each appraised citation offered valuable insight regarding preoperative fasting rituals and
their repercussive effects on the body. After weighing the evidence and analyzing clinical
significance, it can be confidently concluded that preoperative dieting should include a clear
liquid carbohydrate solution two hours before the scheduled procedure as opposed to remaining
NPO after midnight. Prolonged fasting is a detriment to the patient’s preoperative period,
causing increased anxiety and agitation that is essentially caused by a lack of oral intake. With
such strict NPO guidelines based on the traditional 8 hour fast, it is likely for patients to become
noncompliant with the order, creating a very serious safety risk that surgeons must be aware of
(Kramer, 2000). In addition to preventing optimal wellness, breaking strict NPO instruction can
also delay a patient’s surgery, potentially causing added harm to the patient if not operated on
when originally scheduled.
In the intraoperative period, it is of vital importance that the client’s stomach is nearly
empty of all contents in order to prevent Mendelson’s syndrome associated with anesthesia.
Based on the research provided, it is concluded that gastric aspiration has an extremely low
incidence in today’s operating rooms. Specifically, 1 out of every 2,000-3,000 operations result
in some degree of gastric regurgitation (Brown & Heuberger, 2014). Though rare, gastric
aspiration is a fatal complication that is believed to be related to RGV. Additionally, research
shows that NPO after midnight and clear liquids 2 hours before result in very similar residual
gastric volumes, suggesting that one preoperative diet method is just as effective as the other in
relation to intraoperative incidence of aspiration.
In the post anesthesia period, the body begins to adjust back to its normal functioning
which includes regaining the ability to swallow, consciously breathe, etc. Research has shown
that the intake of clear liquids and carbohydrates 2 hours before surgery can improve the body’s
stress response by decreasing insulin resistance. Clear liquids also produce an anabolic state of
metabolism which will help “rebuild” and energize the body after surgery by using up the CHO
reserves ingested during preop (Brown & Heuberger, 2014). Understandably so, patients are
more likely to have a shorter hospital stay as their postoperative recovery advances (Crenshaw,
2011). In conclusion, it is suggested to adhere to a preoperative diet of a carbohydrate/clear
liquid solution 2 hours before surgery in order to promote optimal healing and allow for an
efficient and productive postoperative recovery.
In adult preoperative patients scheduled for surgery in the OR, what are the effects of a
“strict” NPO diet after midnight to reduce incidence of intraoperative aspiration and
other pre and postoperative complications, compared to a “flexible” NPO diet consisting
of clear liquids and intake of carbohydrate rich solutions (CHO)?
In relevance, all evidence and reviews have been appraised in regards to the question…
The presented evidence has addressed the effects of a “strict” NPO diet in all three realms of
surgery: preoperative, intraoperative, and postoperative. In synthesis, the data was compared to
a “flexible” NPO diet consisting of clear liquids and carbohydrate solutions. In regards to
intraoperative aspiration, the overall incidence is rare so it is concluded that either diet is
favorable in that respect. In the preoperative stage, clear liquids and CHO is the recommended
diet, for this intervention is likely to reduce symptoms such as anxiety, agitation, hunger, and
thirst before induction. Prolonged fasting with NPO after midnight can also cause unnecessary
complications such as hypovolemia and confusion (Oshodi, 2004). Finally, in the postoperative
period, clear liquids with CHO promote healing and quickened recovery.
Clinical & Research Recommendations
The evidence suggesting that clear liquids and carbohydrates 2 hours before surgery is
safe and a more comfortable preoperative diet is overwhelmingly supported by articles, clinical
trials, and blind studies. It is my clinical recommendation that this research is distributed to all
surgeons, OR nurses, CRNA’s, anesthesiologists, etc. In doing so, it is my hope that healthcare
professionals will guide their practice through streamlined and up to date nursing evidence. It is
evidence based practice that governs nursing interventions as the most important outcome
remains to be patient safety. Educational seminars are also important in the clinical setting for it
would provide valuable knowledge about preoperative teaching and potentially change the way
in which patients are instructed to prepare for surgery.
Additional research is necessary to solidify this intervention and begin to implement it
into clinical practice. For example, research regarding emergent procedures are important to
assess because the patient obviously does not have the time to adhere to an NPO restriction of
any kind. Could this alter the incidence of gastric aspiration? Additionally, it would be helpful
to understand a patient’s comorbidities and how they may affect the risk of complications in any
of the three stages of surgery. In the evidence provided, the included surgeries were only
abdominal. It would be wise to trial other types of surgeries, such as bariatric or pediatric, in
regards to incidence of aspiration. Finally, I believe that studies must be conducted containing
larger populations. With an increase in participants, it is more likely to produce evidence that is
statistically significant, meaning the difference in outcomes did not occur by chance. It is my
hope that with increased populations in trials and further evidence validity, operating rooms
around the country will begin to fade out NPO after midnight instructions and elevate orders to
include the intake of clear liquids and carbohydrate solutions 2 hours before surgery.
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