Review Article :
Bariatric surgical treatments have increased in
recent history, largely due to the growing rates of obesity. In light of this,
correct nutritional management of these patients peri-operatively is as crucial
as ever. This articles describes the evidenced-based approach to the
nutritional management of patients in the setting of bariatric surgery in order
to achieve the best possible outcome post-operatively. Bariatric treatments
have sharply increased due to the rise in severe obesity that has been
ineffective against diet, exercise, and medical therapy [1]. This, in addition
to the introduction of laparoscopic procedures, is proposed to be the reason
behind the number of bariatric procedures doubling in number over the past
decade [2,3]. Furthermore, bariatric surgery is justifiable given its
documented impact on comorbidities associated with obesity, with a decrease in
post-operative weight known to improve features of metabolic syndrome [4,5].
However, it is also important to maintain this post-operative weight loss with
appropriate nutrition.
Furthermore, an equally important part of post-operative diet is pre-operative
nutrition in order to maximise the successful outcome of surgery. This review
focuses on the perioperative and post-operative long-term nutrition of patients
in the setting of bariatric surgery. In the 2-4 weeks
leading up to bariatricsurgery, surgeons tend to place their patient patients on a very-low
calorie diet (VLCD) [6]. VLCD aims to provide patients with low energy intake,
whilst also maintaining a high protein formula, the combination of which
results in rapid weight loss, adequate satiety for a few days, and minimises
loss of fat-free mass [7,8]. VLCD has been clinically proven to induce weight loss [9]. With
the intention of optimising safety of the procedure, pre-operative weight loss
is ideal. The primary reason for this is that it reduces liver volume, provides
greater surgical access, and reduce peri-operative complications [10,11]. The
role of VLCD in having these effects can be appreciated when considering the
fact that excessive intrahepatic deposition of fat has complicates the
technical aspects of surgery and increase operating time [12,13]. Furthermore,
an enlarged liver has been reported to be the most common cause for conversion
to an open procedure during laparoscopic gastric
bypass and gastric banding [14,15]. It is significant to
note that while some VLCD programs may extend for over 12 weeks, research has
demonstrated that 80% of the decrease in liver volume in response to VLCD is
achieved after the initial 2 weeks [16]. Furthermore, there is concern that an
aggressive or prolonged form of this diet may be associated with adverse
outcomes such as impaired immunity and poor wound healing [13,17].
For this reason, in order to reach a balance between maximizing weight loss,
and minimizing complications, the preference is to adhere to only 2 weeks of
VLCD as is practiced in most Australian centres, with a product such as
OptiFast. This evidence strongly
suggests that in the pre-operative setting, the patient should be commenced on
a 2 week very-low calorie diet pre-operatively, such as Optifast, and to then
be fasted from the day prior to the procedure. To specifically define Optifast,
it is a Nestle product that replaces the typical three meals per day, and
patients instead consume five shakes per day, which provides 1906 kJ, including
70 g of protein, 15 g of fat, and 100 g of carbohydrates, as well as the
recommended daily allowance of essential vitamins, minerals, and trace elements
[10]. In the early
post-operative period, the patient is to return from theatre to the recovery,
ward or high-dependency unit in a fasting state. It is important to note that
the priorities in this time period are assessing for leak, minimising nausea
and vomiting, as well as maintaining fluid balance [18]. It is also important
to note that the post-operative diet plans are generally surgeon- or
institution-specific, as well as the bariatric procedure-type specific.
Typically, on post-operative day one, if there is a negative gastrografin leak
test, patients are commenced on a clear fluid diet [18]. After this initial
period in which the absence of a potential leak is confirmed, and nausea is
minimal, it would be appropriate to upgrade the patients current intake, and
this is based on the texture and volume of food that the patient can tolerate.
The patients diet transitions from liquids to puree or blended foods, and then to solids [19].
Over the initial week, it is expected that most patients will be on fluids, and
the transition in upgrading to solids is a slow process. Solid foods are
commenced at approximately 10 to 14 days after surgery, once the
gastrointestinal tract has healed and patients are able to tolerate more
solid-textured foods. As described above, this is done whilst transition from a
soft diet to a normal diet. The goals of
nutritional management in the early period following bariatric surgery
patients is to promote intake of sufficient energy and nutrients to allow
healing and preservation of lean tissue during the period of rapid weight loss
after surgery and to consume foods that do not cause dumping syndrome, reflux
or early satiety, while also limiting calorie intake [20]. To improve
nutrition, it is also important to acknowledge the barriers to oral intake.
Prophylactically charting pharmacologic treatment before the development of
post-operative nausea
and vomiting
significantly reduces its incidence [21,22]. Based on this evidence,nutrition in the
early post-operative period would be based on excluding a leak on radiology,
and then slowly commencing fluids over the first two weeks, before upgrading to
a soft diet and then eventually a full diet if the patient is able to tolerate
doing so. A number of adverse
effects or deficiencies have been noted following bariatric surgery, and
because of this, the patients diet needs to be adjusted to prevent against
these. Guidelines from the American Society for Metabolic & Bariatric
Surgery recommend nutrient assessments every three to six months in the first
year after bariatric surgery, and annually thereafter with laboratory testing
[19,23]. In order to account for the malabsorptive component of bariatric
surgery, and prevent against these nutrient deficiencies, it is important for
patients to comply with nutrition and lifestyle modifications, as recommended
by the American Association of Clinical Endocrinologists [19]. It is
significant to note that these malabsorptive effects following bariatric
surgery are more frequent in procedures such as roux-en-Y gastric bypass and
biliary pancreatic diversion [24]. Protein is the most
significant component of the macronutrients that needs to be considered in
long-term management of bariatric nutrition. 18-25% of patients suffer protein
deficiencies after malabsorptive bariatric procedures, compared with only 2% of
patients after restrictive bariatric surgery [25,26]. Protein malnutrition has
potential to occur in bariatric surgery due to malabsorption from bypassing a
segment of small bowel, or less frequently, from dietary restriction [24]. It
is recommended that 1.1-1.5 g/kg ideal body weight/day of protein supply is
needed for patients after bariatric surgery [19]. The recommended daily intake
of protein is 56 grams/day for men and 46 grams/day for women. When considering
how this is adjusted after a bariatric procedure, protein requirement during
the post-operative weight loss phase should be calculated as 1.2 grams/kg body
weight for preservation of fat-free mass. [27]. The only exception to this rule
is for patients who have undergone biliopancreatic diversion with duodenal
switch, as this results in significant malabsorption, and therefore a higher
protein intake of 1.5 to 2.0 g of protein/kg body weight per day [28]. Various vitamin deficiencies are also common
after bariatric surgery. Fat soluble vitamins (A, D, E, K) are also a common
deficiency following bariatric surgery, particularly in malabsorptive-type
procedures such as roux-en-Y gastric bypass and biliopancreatic diversion [24,
29, 30]. Following any type of bariatric procedure, it is crucial that patients
continue to meet the recommended daily allowance for fat-soluble vitamins in
the general population. With regards to those following significant
malabsorptive surgery, if there are no other complications, these patients
should be commenced on supplements for all four of the fat-soluble vitamins as
there is a high incidence of their associated deficiencies occurring [31]. When
considering water-soluble vitamins of clinical significance, note that vitamin
B12 deficiency is uncommon in the initial 12 months post-operatively due to
existing reserves within the liver [32]. However, it is known to occur as time
progresses, and therefore, should be monitored at regular intervals, and
treated with supplements if necessary [29,31]. The most critical
mineral deficiency occurring post-operatively with bariatric patients is that
of iron [33]. Its pathogenesis is underpinned by the impaired ability of the
intestinal tract to secrete adequate acid to reduce ferrous to ferric iron, as
well as the reduced absorption of iron in the setting of a bypass [24]. The
literature surrounding this is somewhat controversial despite several studies
supporting the long-standing notion that bariatric surgery, particularly
malabsorptive bariatric surgery, is linked with depletion of iron stores
[34-37]. Another school of thought, based on recent cohort studies, is that the
role of surgery has been over-estimated, or that bariatric procedures may
exacerbate an already pre-existing iron deficiency, but do not serve as an
initiating factor [29,32]. Regardless, there is an obvious need to monitor
serum ferritin and iron levels in the body, and consider further iron
supplementation if necessary. Also part of nutritional
management in these patients is avoiding the potential complication of dumping
syndrome. Dumping syndrome refers to the rapid gastric emptying that occurs
after bariatric surgery. Its underlying pathogenesis is related to the delivery
of energy-concentrated food to the small intestine, which exerts local osmotic
effects and delayed hypoglycaemic
events [38,39]. The resulting clinical symptoms are uncomfortable, of which
include vomiting, nausea,
abdominal pain, diarrhoea,
lethargy, and manifestations of post-prandial hypoglycaemia [40]. This is more
prevalent with malabsorptive surgery, as with most complications, however, it
is also treatable or preventable with appropriate nutritional modifications.
These include consuming smaller and more frequent meals, as well as avoiding
carbohydrate–dense foods, and separating solids from liquid intake by 30
minutes [24]. A second line therapy to consider when symptoms are refractory to
lifestyle changes are administration of somatostatin analogues, such as octreotide
50 mg subcutaneously given 30 minutes prior to the meal [41]. The long-term
management of nutrition following bariatric surgery is clearly quite complex,
and best results are achieved with the assistance of a dietician. In terms of
vitamin and mineral supplementation in the long-term, guidelines are available
for prescribers [19,42]. These supplemental recommendations are very much
procedure-specific depending on whether a malasborptive or restrictive
operation was performed. Bariatric surgery is an
effective method of weight loss in obese patients, but is not the end of
treatment. Ongoing careful nutrition is also of significance in ensuring
patients both keep their weight low, whilst also consuming the necessary
nutrients. The pre-operative diet is also important, but more so from an
operative approach perspective. The nutritional management of malabsorptive
procedures, such as roux-en-Y gastric bypass is much more complex due to the
decreased bioavailability, and these patients are likely to benefit from
stricter monitoring of deficiencies and ongoing dietetics input. Clinical Guidelines on the Identification,
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Shannon
C, A Gervasoni, T Williams. The bariatric surgery patient--nutrition
considerations (2013) Aust Fam Physician 42: 547-552. Citation: Sivakumar
J. Nutritional Management of Bariatric Surgical Patients in the Peri-Operative
Setting (2018) Journal of Obesity and Diabetes 1: 18-20Nutritional Management of Bariatric Surgical Patients in the Peri-Operative Setting
Jonathan Sivakumar
Abstract
Full-Text
Introduction
Pre-Operative Nutrition
Post-Operative Nutrition: Short-Term Setting
Post-Operative Nutrition: Long-Term Setting
Conclusion
References
