NEW YORK NURSE: June/July 2012
by Rona F. Levin, PhD, RN, Visiting Adjunct Professor; University of Medicine and Dentistry of New Jersey Adjunct Professor, New York University • email@example.com
How many of you work in agencies that are still requiring patients to remain NPO (have nothing by mouth) from midnight on the morning of surgery? Have you ever questioned this practice? Did you know that the latest evidence on the effect of different preoperative fasting regimens on perioperative complications and patient well-being does not support the traditional guideline of ‘NPO after midnight’? So, you might ask most appropriately, how do I know this? On what evidence is that statement based? This column answers those questions.
Brady, Kinn, Stuart, and Ness (2010) conducted a review “. . . to systematically identify, appraise and synthesize the evidence in relation to different preoperative fasting regimens (duration, type and volume of permitted intake) in terms of perioperative complications and patient well-being (including aspiration, regurgitation and related morbidity, thirst, hunger, pain, nausea, vomiting, anxiety) in different adult populations”(p. 3-4). The review focused on three primary outcome measures: rates of adverse events, volume and/or pH of gastric contents, and concentration of a marker dye, which was considered a measure of gastric emptying. Secondary outcomes included the following: thirst, hunger, pain, nausea, vomiting, and anxiety.
The population of patients included in the studies reviewed consisted of both male and female adults (18 years or above) undergoing general anesthesia. These studies included mainly healthy patients, but also included high risk anesthetic patients, i.e., those patients who were beyond the second trimester of pregnancy, postpartum, and/or obese. In addition, elderly patients and those with gastric disorders or disease were also considered high risk.
The authors followed the process for a systematic review developed and used by the Cochrane Collaboration, one internationally accepted standard for conducting these types of evidence reviews. This means that we can have confidence that the authors used sound methods for conducting their study. A systematic review is a rigorous, comprehensive, critical summary of evidence on a specific topic or question of interest. There are two major types of systematic reviews: narrative and quantitative. The former is often called an integrative review, and the latter a meta-analysis (Levin, 2009).
To begin, Brady et al. (2010) searched major electronic databases (MEDLINE from 1966 to August 2003, CINAHL from 1982 to August 2003, Cochrane Central Register of Controlled Trials 2nd Quarter 2003, and National Research Register (UK) as of August 2003) to find published articles on their topic. As mentioned in a 2010 Research News You Can Use column: “In addition they hand searched conference proceedings for unpublished works. Including unpublished works in systematic reviews is important because at times, only accessing published research may create a bias in the findings. The bias occurs because often published works support hypotheses and/or show results in support of an intervention. Publishing articles with non-significant results, for example, are not as desirable for many journals, but certainly are important sources of evidence to consider” (Levin, 2010).
Twenty-two randomized controlled trials with a total of 2,270 participants from many different countries (e.g., the United Kingdom, Japan, and Sweden) were included in the review. The fact that the studies included different geographic regions with participants of different cultures lends increased credibility to the results of this review, and allows generalizability across settings and populations. This is especially true given that the research methods across settings were very similar.
The trials reviewed compared various fasting regimens to a standard fast. The standard fast was defined as nothing by mouth from midnight before the morning of surgery; or, if the surgery was to take place in the afternoon, a small (undefined further) breakfast early in the morning on the day of surgery. The experimental comparisons across trials included duration of the fast, type of fluid intake allowed, and volume of fluid intake allowed. For each of these major categories, the specific type of fasting regimen was compared to the standard fast (see Table 1).
After agreeing on the studies to be included in the review, at least two authors independently assessed each of the ten studies for quality, using standardized criteria that included, among other things, how the participants were assigned to experimental and control groups in the randomized controlled trials and whether or not patients or practitioners were blind to the group to which patients were assigned.
The authors were able to combine the statistical results of the studies on the primary outcomes (see above) by conducting meta-analyses. Because the secondary outcomes of interest were measured so differently, meta-analyses were prohibited. The authors, however, did an integrative review (narrative) on these. Results of the comparisons presented in Table 1 on the above primary and secondary outcomes of interest in this review were presented in great detail. The bottom line, however, was that none of the comparisons showed evidence of significant differences on any of the outcome variables between the experimental fasting regimens and the standard fasting regimen.
The authors, therefore, concluded that, “There was no evidence to suggest that a shortened fluid fast results in an increased risk of aspiration, regurgitation or related morbidity compared with the standard ‘nil by mouth from midnight fasting policy” (Brady et al., p. 4). It is important to keep in mind that this conclusion can only be generalized to patients who are not at increased risk for these adverse events. The sample of high risk participants was too small to allow generalization to this population. Thus, additional research needs to be conducted with those at higher risk for complications of anesthesia. In the meantime, however, the evidence does provide a basis for moving away from the traditional practice of “NPO after midnight” for the general surgical population.
Brady, M. C., Kinn, S., Stuart, P., & Ness, V. (2010). Preoperative fasting for adults to perioperative complications. Cochrane Database of Systematic Reviews 2003, Issue 4. Art. No.: CD004423. DOI: 10.1002/14651858.CD004423.
Levin, R. F. (July/August 2010). Research news you can use: Massage for cancer pain. New York Nurse, 14.
Levin, R. F. (2009). Translating research evidence for WCET practice: Appraising a systematic review. World Council of Enterostomal Therapists Journal, 29(2), 39-39-40.