BOMSS Guidelines on perioperative and postoperative biochemical monitoring and
micronutrient replacement for patients undergoing bariatric surgery September 2014
1
BOMSS Guidelines on peri-operative and postoperative biochemical monitoring and
micronutrient replacement for patients undergoing bariatric surgery
Authors
Ms Mary O’Kane, Consultant Dietitian, Leeds Teaching Hospitals NHS Trust
Professor Jonathan Pinkney, Professor of Endocrinology and Diabetes, Peninsula Schools of
Medicine and Dentistry, Honorary Consultant Plymouth Hospitals NHS Trust
Dr Erlend T Aasheim, NIHR Academic Clinical Fellow in Public Health Medicine, MRC
Epidemiology Unit, University of Cambridge School of Clinical Medicine
Dr Julian H Barth, Consultant in Chemical Pathology & Metabolic Medicine, Leeds Teaching
Hospitals NHS Trust
Dr Rachel L Batterham, Head of the UCLH Centre for Weight Loss, Metabolic & Endocrine
Surgery
Mr Richard Welbourn, Consultant Surgeon, Taunton and Somerset NHS Foundation Trust
Adopted by BOMSS Council September 2014
Review date September 2016
BOMSS Guidelines on perioperative and postoperative biochemical monitoring and
micronutrient replacement for patients undergoing bariatric surgery September 2014
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Summary
Bariatric surgery is now an essential option for the treatment of obesity and its associated
comorbidities. Many patients presenting for surgery will have pre-existing low blood vitamin
concentrations and all bariatric surgical procedures compromise nutrition to varying
extents, and have the potential to cause clinically significant micronutrient deficiencies.
Therefore, long term nutritional monitoring and follow-up are essential components of all
bariatric surgical services. However, there are no current standard guidelines in the UK for
the biochemical monitoring and replacement of essential micronutrients in patients
undergoing different forms of bariatric surgery. Furthermore, a survey of members of
BOMSS revealed a wide diversity of local guidelines and practices. This suggested a need for
standard guidelines. We undertook a review of existing guidelines and the associated
literature on micronutrient deficiencies following bariatric surgery. Our aim was to
summarise existing evidence for the monitoring and replacement of vitamins and minerals
prior to, and following bariatric surgery, and to make recommendations for safe practice in
the UK setting.
BOMSS Guidelines on perioperative and postoperative biochemical monitoring and
micronutrient replacement for patients undergoing bariatric surgery September 2014
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Contents
Introduction 4
Background 4
Methods 5
Recommendations for safe practice in the UK setting 6
1: Preoperative care 7
2: Postoperative care and biochemical monitoring 8
2.1: Urea and electrolytes, liver function tests 8
2.2: Full blood count, ferritin, folate and vitamin B12 8
2.3: Calcium, vitamin D and PTH 8
2.4: Fat soluble vitamins A, E and K 9
2.5: Trace minerals: zinc, copper, selenium and magnesium 9
2.6: Thiamine 9
2.7: Glucose, lipids, HbA1c 9
3: Vitamin and mineral supplementation 10
3.1 Complete multivitamin and mineral supplements 11
3.2 Iron 11
3.3 Folic acid 11
3.4 Vitamin B12 12
3.5 Calcium and vitamin D 12
3.6 Vitamins A, E and K 13
3.7 Zinc and copper 13
3.8 Selenium 13
3.9 Thiamine 14
4: Abnormal results / clinical problems 14
4.1 Protein malnutrition / protein energy malnutrition / oedema 14
4.2 Anaemia 14
4.2.1 Iron deficiency anaemia 14
4.2.2 Vitamin B12 and folate 14
4.2.3 Unexplained anaemia / fatigue 15
4.3 Low vitamin D levels 15
4.4 Vitamin A deficiency / disturbances in night vision / xerophthalmia 16
4.5 Vitamin E 16
4.6 Neurological symptoms / Wernicke encephalopathy 16
4.7 Prolonged vomiting 16
4.8 Pregnancy 17
Conclusion 17
Tables 18
Preoperative blood tests to be undertaken on patients undergoing all procedures 19
Postoperative blood tests following gastric balloon 19
Postoperative blood tests following gastric band 20
Postoperative blood tests following sleeve gastrectomy/gastric bypass/duodenal switch 21
Vitamin and mineral supplements following gastric balloon 23
Vitamin and mineral supplements following gastric band 23
Vitamin and mineral supplements following gastric bypass and sleeve gastrectomy 24
Vitamin and mineral supplements following duodenal switch 25
References 26
BOMSS Guidelines on perioperative and postoperative biochemical monitoring and
micronutrient replacement for patients undergoing bariatric surgery September 2014
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Introduction
The incidence of obesity and associated comorbidities continues to increase (1). Bariatric
surgery is an essential treatment option for patients with a Body Mass Index of 40 kg/m² or
more, or between 35 kg/m² and 40 kg/m² with co-morbidity. All bariatric surgery
procedures impact on nutrition to varying degrees. There are currently no UK guidelines for
the nutritional monitoring and replacement of micronutrients. These guidelines make
recommendations for the peri-operative and postoperative biochemical monitoring and
micronutrient replacement for bariatric surgery patients.
Non-nutritional (surgical) complications can also occur during follow-up after bariatric
surgery (e.g. internal herniation after gastric bypass surgery) but this falls outside the remit
of this report.
Background
The National Confidential Enquiry into Patient Outcome and Death (NCEPOD) report “Too
Lean a Service” recommended that all patients have a comprehensive pre-assessment, a
complete discharge summary and a long term follow up plan (2). Access to the appropriate
multidisciplinary healthcare professionals was emphasised. The American Association of
Clinical Endocrinologist, The North American Obesity Society, and American Society for
Metabolic and Bariatric Surgery (AACE/TOS/ASMBS) issued a comprehensive review of
bariatric surgery and guidelines for nutritional management in 2008 with an update in 2013
(3-4). These guidelines were a significant advance although there has been uncertainty as to
how well they can be applied to NHS practice in the UK.
A BOMSS survey of current practice with respect to nutritional assessment and monitoring
was undertaken in 2012 which suggested areas of good practice but also considerable
variation. Although most respondents were involved in assessment and preparation, almost
one third had no standard protocols for preoperative nutritional screening and less than one
half had no standard protocols for preoperative vitamin and mineral measurement and
replacement. Only 55-60% of respondents routinely requested measurement of ferritin,
vitamin B12, folate, calcium and vitamin D levels prior to surgery. Approximately two thirds
of respondents involved in the aftercare of patients following a gastric balloon, and one
third involved in the aftercare of patients with a gastric band, reported that they never
undertook any routine blood tests. 37% of respondents did not recommend any
multivitamins and minerals following the gastric balloon and 12% did not recommend any
after the gastric band. The majority of respondents reported measurement of urea and
electrolytes, liver function tests and vitamin B12 levels following the gastric bypass, sleeve
gastrectomy and bilio-pancreatic diversion / duodenal switch (BPD/DS); however there was
wide diversity regarding other blood tests and frequency of monitoring. Over 98% of
BOMSS Guidelines on perioperative and postoperative biochemical monitoring and
micronutrient replacement for patients undergoing bariatric surgery September 2014
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respondents recommended multivitamins or multivitamin and mineral supplements
following the gastric bypass, sleeve gastrectomy and bilio-pancreatic diversion / duodenal
switch (BPD/DS) but there was variation in recommendations around vitamin B12, calcium
and vitamin D supplementation. These data have been summarised in a Master’s
dissertation at Leeds Metropolitan University (5)
The BOMSS Council recognised the need for UK guidelines. Therefore, it was agreed that the
authors would undertake a review of existing guidelines and associated literature on
micronutrient deficiencies following bariatric surgery. Our aim was to summarise existing
evidence for the monitoring and replacement of vitamins and minerals prior to, and
following bariatric surgery, and to make recommendations for safe practice in the UK
setting.
Methods
Key bariatric surgery guidelines were identified through electronic searches and discussions
with experts in the field. Key guidelines included American Association of Clinical
Endocrinologists, The Obesity Society, and American Society for Metabolic and Bariatric
Surgery (AACE/ASMBS/TOS) “Medical Guidelines for Clinical Practice for the Peri-operative
Nutritional, Metabolic, and Non-surgical Support of the Bariatric Surgery Patient”(3) ;
ASMBS Allied Health “Nutritional Guidelines for the Surgical Weight Loss Patient” (6);
AACE/TOS/ASMBS “Clinical Practice Guidelines for the Peri-operative Nutritional, Metabolic,
and Non-surgical Support of the Bariatric Surgery Patient- 2013 Update” (4); “Endocrine and
Nutritional Management of the Post-Bariatric Surgery Patient: An Endocrine Society Clinical
Practice Guideline” (7); ASMBS “Position Statement, Metabolic Bone Changes After Bariatric
Surgery” (8); Canadian Agency for Drugs and Technologies in Health: “Bariatric Surgery for
Severe Obesity: Systematic Review and Economic Evaluation”(9); “Interdisciplinary
European Guidelines on Surgery of Severe Obesity 2007” (10) and “Interdisciplinary
European Guidelines on Metabolic and Bariatric Surgery 2014” (11).
The Obesity Surgery Society for Australia and New Zealand web pages referred to the
AACE/ASMBS/TOS 2008 guidelines and the Dietitians Association of Australia (DAA)
“Dietetic Practice Recommendations for obesity surgery”. The DAA were contacted. They
advised that the Dietetic Practice Recommendations were published in 2005 and the DAA
was considering a review.
All the guidelines were reviewed. The AACE/ASMBS/TOS (3), ASMBS Allied Health (6) and
AACE/TOS/ASMBS (4) gave the most comprehensive recommendations on peri-operative
and postoperative nutritional management of patients. These were considered alongside
the current practices identified by the respondents to the BOMSS survey. None of the
guidelines included recommendations for patients with gastric balloons. The sleeve
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micronutrient replacement for patients undergoing bariatric surgery September 2014
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gastrectomy was included in the AACE/TOS/ASMBS 2013 guidelines (4) but was considered
investigational in the Interdisciplinary European Guidelines 2014 (11). The authors
considered that it was essential to include recommendations for both the gastric balloon
and sleeve gastrectomy as both of these procedures are commonly undertaken in the UK.
Other associated guidelines were reviewed. These included “Evaluation, Treatment, and
Prevention of Vitamin D Deficiency: an Endocrine Society Clinical Practice Guideline” (12);
“Guidelines for Preventing and Treating Vitamin D Deficiency and Insufficiency
Revisited”(13); the National Osteoporosis Society “Vitamin D and Bone Health: A practical
clinical guideline for patient management” (14) and the Centre for Maternal and Child
Enquiries /Royal College of Obstetricians and Gynaecologist (CMACE/RCOG) “Joint Guideline
on Management of Women with Obesity in Pregnancy” (15).
The guidelines were reviewed with respect to recommendations on peri-operative
nutritional assessment, postoperative nutritional monitoring and micronutrients. A limited
literature search was carried out using Medline and EMBASE to identify additional recent
publications especially where more clarity was needed or there was a difference in
recommendations. The journals “Obesity Surgery” and “Surgery for Obesity and Related
Diseases” were also searched for relevant articles in press. The authors reached a
consensus on key areas of focus and to include the management of abnormal results and
clinical nutritional problems as part of the recommendations.
Recommendations for safe practice in the UK setting
Micronutrient deficiencies have been found in morbidly obese patients prior to bariatric
surgery (16-19). These include low levels of ferritin, haemoglobin, vitamin B12 and others.
Vitamin D insufficiency or deficiency is prevalent and Grace et al. reported that almost 90%
of their patients considering bariatric surgery had an inadequate vitamin D status (20).
All bariatric procedures will affect nutritional intake and/or absorption to varying degrees.
Most procedures require a phased approach to the introduction of foods beginning with
liquids followed by a blended diet and progressing to a soft diet and then more solid foods.
Food portions are significantly reduced. Patients must learn to eat slowly and chew their
food well. Some patients may struggle to comply with the dietary recommendations and so
the surgery itself may not necessarily result in a nutritionally improved diet (21-23).
Although the gastric balloon and gastric band have no impact on absorption of nutrients,
patients may still experience vomiting or regurgitation and develop food intolerances. The
gastric bypass impacts on the absorption of iron, vitamin B12, calcium and vitamin D (3-4).
The BPD/DS has the greatest impact on malabsorption affecting the absorption of protein,
fat soluble vitamins and zinc in addition (3-4). The longer term impact of the sleeve
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gastrectomy on nutrition is less well known but there are reports of low vitamin B12 levels
and iron deficiency anaemia (24-25).
All patients should have a comprehensive assessment, including their nutritional status,
prior to bariatric surgery. For patients with deficiencies identified early in assessment, it
may be appropriate to inform and advise the general practitioner to treat. Any nutritional
deficiencies should be corrected prior to surgery and the multidisciplinary team has a
responsibility to ensure that patients are able to meet nutritional requirements following
surgery.
These recommendations for bariatric surgery patients cover the gastric balloon, gastric
band, gastric bypass, sleeve gastrectomy and BPD/DS procedures. They cover preoperative
care, postoperative care and biochemical monitoring, vitamin and mineral supplements and
the management of abnormal results / clinical problems. Although the matter of pregnancy
in women who have undergone bariatric surgery was considered beyond the scope of this
document a brief mention is included in section 4.
1. Preoperative care
All patients should have a comprehensive nutritional assessment prior to bariatric surgery.
This should include a detailed dietary assessment by a trained dietitian with specific
experience of bariatric nutrition, screening for eating disorders, and psychosocial
assessment. Essential preoperative blood tests include screening for diabetes,
dyslipidaemia, renal function and nutritional deficiencies (See Table 1) (3-4, 7, 11).
Additional discretionary tests should be considered if clinically indicated. The NCEPOD
report “Too Lean a Service” (2) emphasised the importance of the multidisciplinary
assessment, so that patients have access to all the appropriate healthcare professionals.
Nutritional deficiencies identified at this stage should be investigated and corrected as
clinically indicated prior to surgery (7). This may take place as part of the preoperative
preparation by multidisciplinary obesity teams (26-27) (See section 4).
Many centres recommend a low calorie / low carbohydrate diet immediately prior to
surgery to shrink the size of the liver (28). A multivitamin and mineral supplement may be
needed as these diets are not always nutritionally complete (29).
Where patients are being considered for BPD/DS procedure, additional investigations such
as baseline DEXA scans for bone mineral density (BMD) should be considered in specific
patient groups (8). These groups include younger postmenopausal women and men aged 50
to 69 with clinical risk factors for fracture.
BOMSS Guidelines on perioperative and postoperative biochemical monitoring and
micronutrient replacement for patients undergoing bariatric surgery September 2014
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2. Postoperative care and biochemical monitoring
It is essential that patients are monitored following bariatric surgery to ensure that they are
both meeting their nutritional requirements and to mitigate risks of developing nutritional
deficiencies as a result of the surgical procedure. The type and frequency of monitoring
should reflect the bariatric procedure, but also the needs of individual patients. There is
therefore recognition that nutritional monitoring may need to be individualised. There
should be full access to appropriate members of the MDT including the physician if required.
Details of the suggested biochemical monitoring by procedure are shown in Tables 2-4.
2.1 Urea and electrolytes, liver function tests
It is recommended that urea and electrolytes (U&E) and liver function tests (LFT) are
monitored for all procedures. The frequency of monitoring depends on the procedure.
Dehydration can occur in the early stages following surgery with patients finding it difficult
to maintain an adequate fluid intake. Abnormal liver function tests due to non-alcoholic
fatty liver disease are common or may relate to other conditions and require further
investigation. Changes such as low albumin may be a sign of dietary non-compliance or
malabsorption especially following the BPD/DS (30-32). However, low albumin levels are not
only an indicator of malnutrition but may also indicate underlying inflammation and
infection.
2.2 Full blood count, ferritin, folate and vitamin B12
Anaemia is a common long term problem and so it is appropriate that all patients are
monitored. In particular, iron deficiency anaemia can occur after gastric bypass surgery due
to a combination of factors including low intake of iron (e.g. due to meat intolerance),
reduced intestinal absorption of iron, and (in women) loss of iron through menstruation
(33). The types of tests and frequency of monitoring should reflect the bariatric procedure.
It should be noted that the megaloblastic and macrocytic anaemia associated with vitamin
B12 deficiency can be masked by deficiency of either folic acid or iron and so it is essential
to routinely assess all haematinics (folate, vitamin B12 and ferritin) before recommending
additional folic acid supplements.
2.3 Calcium, vitamin D and PTH
All patients should have their levels of calcium, vitamin D and PTH levels monitored
following the sleeve gastrectomy, gastric bypass and BPD/DS. If vitamin D supplementation
BOMSS Guidelines on perioperative and postoperative biochemical monitoring and
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is adjusted, the serum 25-hydroxy vitamin D (25OHD) levels should be rechecked after a
minimum of three months (14).
2.4 Fat soluble vitamins A, E and K
Vitamin A deficiencies has been reported following the BPD/DS (30, 32, 34-35). Following
the BPD/DS procedures, patients should have their vitamin A levels routinely monitored at
baseline and then at 6, 12, 18 and 24 months. Following this they should be measured at
least annually. Vitamin A deficiency can be encountered after a gastric bypass although
clinic problems appear rare so consideration should be given to monitoring vitamin A levels
if there are any concerns (36-37). Routine monitoring of vitamins E and K is not
recommended, but they may be measured in situations where this is clinically indicated (4).
This includes unexplained anaemia, neuropathy and nutritional deficiencies.
2.5 Trace minerals: zinc, copper, selenium and magnesium
Zinc and copper levels should be monitored routinely following the gastric bypass and
BPD/DS (4, 38). High dose zinc supplementation over time can cause copper deficiency (39-
41). Selenium levels should also be monitored after these procedures if there is chronic
diarrhoea, metabolic bone disease or unexplained cardiomyopathy (4). Routine monitoring
of magnesium is not recommended, however patients with hypocalcaemia should be
investigated for hypomagnesaemia and treated prior to calcium supplementation (42).
2.6 Thiamine
Although routine monitoring of thiamine is not recommended the possibility of deficiency
should be seriously considered if there is rapid weight loss, poor dietary intake, vomiting,
alcohol abuse, oedema or symptoms of neuropathy. All clinicians involved in the aftercare
of bariatric surgery patients should be aware of the potential risk for severe thiamine
deficiency (see Section 4.6). If thiamine deficiency is suspected, intravenous treatment
should not be delayed pending tests results but initiated immediately.
2.7 Glucose, lipids, HbA1c
While this survey did not specifically address the preoperative medical assessment of
diabetes, biochemical monitoring related to diabetes is an important part of pre and post-
operative care for many patients undergoing bariatric surgery, since bariatric surgery is
increasingly advocated to improve important obesity-related medical co-morbidity such as
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type 2 diabetes (43). If bariatric surgery is being undertaken for this reason a detailed
diabetes review is appropriate. Therefore, patients with known, pre-existing diabetes should
have an up to date preoperative evaluation of the adequacy of current glycaemic control,
treatment requirements, presence and extent of diabetes complications, and measurement
of HbA1c as a baseline from which to assess the subsequent impact of bariatric surgery. An
assessment of diabetes aetiology and expected impact of bariatric surgery is also
appropriate. For example, patients with type 1 diabetes and other forms of diabetes that
are characterised by absolute insulin deficiency will not be expected to achieve a remission
of diabetes following bariatric surgery. This assessment is essential in planning the
postoperative diabetes management, especially if withdrawal of insulin is contemplated.
Patients without known diabetes who are undergoing preoperative bariatric assessment are
at high risk of having undiagnosed diabetes and should routinely undergo screening.
Appropriate tests include HbA1c and FPG and/or a discretionary oral glucose tolerance test.
Diabetes is diagnosed according to published criteria (44). Patients with known preoperative
diabetes require appropriate peri-operative and postoperative diabetes management (45).
Since there are currently no agreed guidelines for the postoperative medical management
of diabetes following bariatric surgery, treatment monitoring, adjustment or attempted
withdrawal of medications should be individualised under the supervision of a physician
specialising in diabetes management. It is unknown whether patients with type 2 diabetes
who enter glycaemic remission after bariatric surgery should continue to take metformin to
prevent recurrence of hyperglycaemia, although this is a common practice. Glycaemic
control may be monitored in the short term by regular capillary blood glucose
measurements, and this is important if treatments such as insulin are being reduced or
discontinued. In the longer term, repeat measurements of HbA1c are the basis for glycaemic
monitoring. It is important to note that diabetes does not enter glycaemic remission after
bariatric surgery in all cases, and the cumulative late relapse rate may be in the region of 40-
50% (46-47) and therefore monitoring for diabetes relapse is essential. Even if patients
become euglycaemic, they should remain on the diabetes register and annual diabetes
screening with HbA1c, FPG or a discretionary glucose tolerance test are all appropriate
approaches.
Patients with pre-existing treated dyslipidaemia should undergo a preoperative assessment
with a fasting lipid profile, as a baseline from which to assess the subsequent effect of
bariatric surgery during follow-up. The identification of all relevant preoperative medical co-
morbidity is important, including dyslipidaemia. Therefore, a fasting lipid profile is usually
appropriate in the medical work up for bariatric surgery. Currently there are no generally
agreed medical guidelines for the postoperative monitoring and treatment of
dyslipidaemias, especially continuation or withdrawal of medication, and so these should be
assessed on an individual basis. Similar considerations apply to the management of
hypertension.
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3. Vitamin and mineral supplementation
Tables 5-8 contain details of the recommended vitamin and mineral supplements. As
patients’ requirements and adherence may vary over time, these should be reviewed
regularly.
3.1 Complete multivitamin and mineral supplements
A complete multivitamin and mineral supplement (containing iron, selenium, zinc and
copper) is recommended after all bariatric procedures (4). It is important to note that some
multivitamin supplements that are routinely available may not contain sufficient amounts of
certain vitamins, depending on the recommended doses, to counter the malabsorptive
effects of bariatric surgery, and some do not contain additional or insufficient amounts of
minerals and trace elements. A minimum of 2 mg of copper per day is advised (see section
3.7). Although Forceval contains 2 mg copper, many over the counter preparations contain 1
mg; therefore it may be necessary to recommend that patients take two multivitamin and
mineral supplements (4). The ratio of 8-15 mg of zinc for each 1 mg copper should be
maintained (4).
3.2 Iron
For patients undergoing the insertion of a gastric balloon or gastric band, it should be
possible for patients to meet their iron requirements by oral diet and a complete
multivitamin and mineral supplement containing the recommended daily allowance of iron.
An iron intake of between 45-60 mg from multivitamin and mineral supplements and
additional iron is recommended following the sleeve gastrectomy, gastric bypass and
BPD/DS (4). This may be achieved with 200 mg ferrous sulphate, 210 mg ferrous fumarate or
300 mg ferrous gluconate daily in addition to the multivitamin and mineral supplement.
Women of reproductive age who are menstruating have additional requirements of at least
100 mg elemental iron daily (two ferrous sulphate or ferrous fumarate daily) (48).
Supplements containing iron should be taken alongside citrus fruits / drinks or vitamin C to
aid absorption. Iron and calcium supplements should not be taken at the same time and
preferably two hours apart.
3.3 Folic acid
For the majority of patients, the folic acid contained within standard multivitamin and
mineral supplement is likely to be sufficient in addition to dietary sources of folic acid.
BOMSS Guidelines on perioperative and postoperative biochemical monitoring and
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3.4 Vitamin B12
As patients who have had a gastric bypass often malabsorb vitamin B12 and have low levels
(33, 50-51) routine supplementation with three monthly intramuscular vitamin B12
injections is recommended (52). In view of the mixed findings of reported vitamin B12
depletion after sleeve gastrectomy (24-25, 53) and BPD/DS (30-31), it is also recommended
that these patients receive vitamin B12 supplements (52). In the absence of high doses of
oral vitamin B12 being available on prescription, it is recommended that these patients also
receive intramuscular injections of vitamin B12. Further research is needed as to whether
oral supplementation with over the counter preparations is sufficient for patients who have
a sleeve gastrectomy or BPD/DS or whether their needs are best met with intramuscular
injections.
Untreated vitamin B12 deficiency may result in irreversible neuropathy, which may occur in
the absence of megaloblastic anaemia.
3.5 Calcium and vitamin D
Patients who were found to be vitamin D insufficient prior to surgery are likely to remain on
supplements following surgery however additional vitamin D supplements may be required
to maintain serum 25OHD levels greater than 50 nmol/L after the gastric bypass, sleeve
gastrectomy and BPD/DS (4, 7). Generally, following the gastric bypass or sleeve
gastrectomy, usual practice is in the region of a minimum of 800-1200 mg calcium and 20
mcg (800 IU) vitamin D per day. For some patients, this may be sufficient but for the
majority it will not be. Additional vitamin D supplementation will also be needed following
the BPD/DS (30, 32, 35). Guidance for the treatment of vitamin D deficiency is given in
Appendix 1 of The National Osteoporosis Society Vitamin D and Bone Health: Practical
Guideline for Patient Management (14). Oral vitamin D3 is the preferred treatment for
vitamin D deficiency (14). The guidance recommends loading regimes for the treatment of
deficiency up to a total of approximately 300,000 IU given either as weekly or daily split
doses. Preparations may be given as:
50,000 IU capsules, one given weekly for 6 weeks (300,000 IU)
20,000 IU capsules, two given weekly for 7 weeks (280,000 IU)
800 IU capsules, five a day given for 10 weeks (280,000 IU).
This may then be followed by maintenance regimens 1 month after loading with doses
equivalent to 800 to 2000 IU daily (occasionally up to 4,000 IU daily), given either daily or
intermittently at a higher equivalent dose. Serum calcium levels should be checked one
month after the last loading dose. Full details can be found in Appendix 1: Guidance for
treatment of Vitamin D deficiency. Alternatively many areas may have their own local
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guidance for management of vitamin D deficiency in primary care. Patients who are unable
to maintain vitamin D levels should be referred to a specialist in secondary care.
Patients should be encouraged to have dietary sources of calcium and vitamin D and
increase weight bearing activity (6). Calcium and iron supplements should not be taken at
the same time. It is recognised that calcium citrate is more bioavailable than calcium
carbonate, however, it is not readily available in the UK (6, 8).
3.6 Vitamins A, E and K
For the majority of patients who have a gastric band, sleeve gastrectomy or gastric bypass,
requirements for vitamins A, E and K can usually be met by oral diet and a “complete”
multivitamin and mineral supplement. Patients who have undergone BPD/DS are more likely
to have additional requirements for vitamin A and potentially also for E and K. Mechanik et
al. suggest that these are best supplied in a water soluble form
1
(3) however continued
monitoring is essential as this may still not be sufficient.
3.7 Zinc and copper
Multivitamin and mineral supplements should contain both sufficient zinc and copper. A
minimum of 2 mg of copper per day is advised (4). If additional zinc supplements are
required, the ratio of 8-15 mg of zinc for each 1 mg copper should be maintained (4).
Patients who have had gastric bypass or BPD/DS may have additional requirements for zinc
and copper. Forceval contains 2 mg copper and 15 mg zinc and doubling up on the dosage of
Forceval may be sufficient in some cases to meet the additional requirements (54).
3.8 Selenium
A complete multivitamin and mineral supplement, which contains selenium, should be
sufficient to meet needs after bariatric surgery. Additional selenium may be needed in some
patients following gastric bypass, BPD or DS (32, 55). Patients may prefer to eat two to three
Brazil nuts a day as these are a rich source of selenium. Over the counter preparations may
also be used to supplement selenium.
1
AquADEKs Softgels are water soluble however only available in the UK on a named patient basis
BOMSS Guidelines on perioperative and postoperative biochemical monitoring and
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3.9 Thiamine
The multivitamin and mineral supplement should contain sufficient thiamine. Additional
thiamine supplementation should be administered to patients at risk of Wernicke
encephalopathy, such as those with prolonged vomiting, poor nutritional intake, high
alcohol intake or fast weight loss. Consideration should be given to admission and
immediate parenteral replacement with thiamine in patients where thiamine deficiency is
suspected. See sections 4.6 and 4.7.
4. Abnormal test results and clinical problems
4.1 Protein malnutrition / protein energy malnutrition / oedema
This can present several years following bariatric surgery. Causes include poor dietary
protein intake as well as malabsorption. Oedema is an important indicator of protein energy
malnutrition, and may mask weight loss and muscle wasting. Whilst it is necessary to
exclude the many other causes of oedema, the patient should also be referred back to the
bariatric centre for further investigation.
4.2 Anaemia
4.2.1 Iron deficiency anaemia
Iron deficiency anaemia may be dietary in origin, with oral diet and iron supplements being
insufficient to meet the needs of the patient. Sources of blood loss, both related and
unrelated to bariatric surgery should also be considered, investigated and excluded. For
patients who have iron deficiency anaemia, Malone et al. suggest an 8 week course of oral
iron (325 mg ferrous sulphate b.d.) (56). For those patients who are unable to tolerate or
are non-compliant with oral iron or whose levels did not respond, the authors recommend
referral for intravenous iron infusions. Following this, full blood count and ferritin stores
should continue to be monitored to ensure ferritin stores remain within the reference
range.
4.2.2 Vitamin B12 and folate
If a patient presents with megaloblastic, macrocytic anaemia, vitamin B12 levels should be
checked before giving additional folic acid, as folic acid supplementation in severe vitamin
B12 depletion may lead to neurological complications. Vitamin B12 deficiency should be
treated with intramuscular injections and levels maintained with three monthly vitamin B12
injections.
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Folic acid deficiency may indicate non-compliance with the daily multivitamin and mineral
supplement or malabsorption. Additional folic acid supplementation is recommended and
further investigations if suspicion of malabsorption. Serum folate levels should be rechecked
after four months. High folate levels can reflect supplementation or, in some cases, bacterial
overgrowth in the small intestine.
4.2.3 Unexplained anaemia / fatigue
If anaemia or fatigue is unexplained, it may be a symptom of other nutritional deficiencies
including protein, zinc, copper and selenium so it is suggested that the levels of these are
investigated.
4.3 Low vitamin D levels
Whilst low vitamin D levels are not a barrier to bariatric surgery, if the patient presents with
low vitamin D levels prior to surgery, treatment with vitamin D should begin preoperatively
especially where the surgical procedure is likely to result in vitamin D malabsorption (7.)
Following surgery, if the patient presents with vitamin D deficiency, compliance with the
recommended supplements should be checked. For some patients, despite good
compliance, additional supplementation with vitamin D is needed.
For bariatric surgery patients, their vitamin D levels may be affected not only by exposure to
sunlight but also by the bariatric procedure. The National Osteoporosis Society Vitamin D
and Bone Health: A Practical Clinical Guideline for Patient Management (14) recommends
that serum 25OHD levels less than 50 nmol/L may be inadequate and need treatment. The
recommended treatment regimen is explained fully and involves a loading dose of vitamin
D3 over several weeks followed by a maintenance phase. For those patients who remain
vitamin D deficient or need a more aggressive approach, they recommend a referral to a
secondary care specialist.
4.4 Vitamin A deficiency / disturbances in night vision / xerophthalmia
Vitamin A deficiency can lead to eye problems such as loss of night vision (57) and
xerophthalmia and may also result in foetal abnormalities. Vitamin A levels should be
measured if there are concerns and if appropriate a referral to an ophthalmologist should
be considered. For treatment of vitamin A deficiency, oral supplementation with vitamin A,
5000-10,000 IU/day is recommended however more may be needed if the patient is
experiencing night blindness (3). The levels should be rechecked after two to three months
(3).
BOMSS Guidelines on perioperative and postoperative biochemical monitoring and
micronutrient replacement for patients undergoing bariatric surgery September 2014
16
4.5 Vitamin E
Mechanik et al. recommend that vitamin E (800-1200 IU/day) should be used when there is
documented deficiency and should be continued until serum levels reach the normal range
(3).
Vitamin E is normally assessed by serum α-tocopherol, which does not have a specific
plasma carrier protein and is transported non-specifically in lipoproteins. When considering
vitamin E nutritional status, adjustment should therefore be made for serum lipids (58).
Vitamin E in large doses can exacerbate vitamin K deficiency and therefore affect blood
coagulation (59) so over-replacement should be avoided. Aills et al. suggest 500 mg vitamin
E daily is sufficient to correct deficiency (6). Furthermore, assessment of vitamin K should be
performed when there is established fat-soluble vitamin deficiency with hepatopathy,
coagulopathy or osteoporosis (3).
4.6 Neurological symptoms / Wernicke encephalopathy
Wernicke encephalopathy secondary to thiamine deficiency and myeloneuropathy (which
includes spinal cord changes and peripheral neuropathy) secondary to deficiencies of
vitamin B12 or copper are severe complications which can sometimes occur after bariatric
surgery.
A literature review found 104 cases of Wernicke encephalopathy syndrome after bariatric
surgery, with an incidence of around 1 in 500 cases after BPD, suggesting that this
preventable complication is not rare (60). In patients at risk of thiamine deficiency,
additional thiamine and vitamin B co strong should be given immediately (thiamine 200–300
mg daily, vitamin B co strong 1 or 2 tablets, three times a day) (61). For those unable to
tolerate thiamine orally or with clinical suspicion of acute deficiency intravenous thiamine
should be given (62). Oral or IV glucose must not be given to patients at risk of or with
suspected thiamine deficiency as it can precipitate Wernicke-Korsakoff syndrome.
Vitamin B12 and copper levels should be assessed and any deficiencies corrected. With
severe copper deficiency, an inpatient admission may be required for administration of
intravenous copper. Patients with neurological symptoms should be referred to a
neurologist.
4.7 Prolonged vomiting
While patients may occasionally experience regurgitation of food after bariatric surgery,
prolonged vomiting is not normal and should always be investigated. A referral back to the
BOMSS Guidelines on perioperative and postoperative biochemical monitoring and
micronutrient replacement for patients undergoing bariatric surgery September 2014
17
bariatric centre is advisable. Prolonged vomiting may lead to severe thiamine deficiency.
Thiamine and vitamin B co strong should be given immediately as above in section 4.6 (59).
Those unable to tolerate oral thiamine, intravenous thiamine should be administered. Oral
or IV glucose must not be given (63).
4.8 Pregnancy
Women are often advised to avoid pregnancy for the first twelve to eighteen months
following surgery (4). The evidence base for this recommendation is limited, but it helps to
ensure that the patient has reached a stable weight and facilitates appropriate planning of
pregnancy and associated care.
Healthy women, planning for pregnancy, should take an additional 400 mcg/day folic acid
prior to conception until the 12th week of pregnancy however in women with obesity or
diabetes, the recommendation is 5 mg folic acid until the 12th week of pregnancy as there
may be an increased risk of neural tube defect affected pregnancy (15, 59, 64-65). The
strength of the evidence base underlying this recommended dose (5 mg) is debated.
Women, as part of preconception care, are advised to avoid vitamin and mineral
preparations which contain vitamin A in the retinol form in the first 12 weeks of pregnancy.
Supplements containing retinol may increase the teratogenic risk especially in the first
trimester (59). There are vitamin and mineral supplements containing no vitamin A which
are specifically aimed at preconception and pregnancy e.g. Pregnacare, Seven Seas
Pregnancy and Centrum Pregnancy Care; however avoidance of supplements containing
vitamin A may place women more at risk of low vitamin A levels especially if they have had a
distal bypass or BPD/DS. The health care professional should check that any supplements
contain vitamin A in the beta carotene and not retinol form.
Patients who become pregnant following bariatric surgery should undergo nutritional
screening every trimester. This should include ferritin, folate, vitamin B12, calcium and fat
soluble vitamins (4). Pregnant patients, especially those who have had distal bypass or
BPD/DS procedures, may be at risk of low vitamin A levels and possibly vitamins E and K.
Vitamin A levels (and possibly vitamin E and K levels) should be monitored during
pregnancy. A more frequent review with the specialist bariatric dietitian may be required.
Conclusion
There is a wide variation in practice with respect to preoperative assessment, postoperative
biochemical monitoring and vitamin and mineral supplements for patients undergoing
bariatric surgery. This could result in suboptimal care and result in nutritional problems
being unidentified. The literature review provides some of the evidence base that is
BOMSS Guidelines on perioperative and postoperative biochemical monitoring and
micronutrient replacement for patients undergoing bariatric surgery September 2014
18
required for the development of consensus guidelines which have the potential to improve
clinical practice and safety for patients undergoing bariatric surgery. Further research is
needed to further develop the evidence base and these guidelines need to be reviewed as
new evidence emerges.
BOMSS Guidelines on perioperative and postoperative biochemical monitoring and
micronutrient replacement for patients undergoing bariatric surgery September 2014
19
5. Tables
Table 1 Preoperative blood tests to be undertaken on patients undergoing all bariatric procedures
General and nutritional
Full blood count
Ferritin
Folate
Vitamin B12
25 hydroxy-vitamin D
Calcium
Parathyroid hormone
Liver function test
Urea and electrolytes
Comorbidities
Fasting Glucose
HbA1c
Lipid profile
Table 2 Postoperative blood tests following gastric balloon
Blood test
Frequency
U+E, LFT, FBC
Monitor if any concerns regarding nutritional intake
HbA1c and/or FBG in patients
with preoperative diabetes
Monitor as appropriate
BOMSS Guidelines on perioperative and postoperative biochemical monitoring and
micronutrient replacement for patients undergoing bariatric surgery September 2014
20
Table 3 Postoperative blood tests following gastric band
Blood test
Frequency
U+E, LFT, FBC
Monitor annually and more frequently if any concerns regarding nutritional
intake
HbA1c and/or FBG in
patients with preoperative
diabetes
Monitor as appropriate
Lipid profile
Monitor in those with dyslipidaemia
Serum 25 hydroxy Vitamin D
Routine monitoring is usually not required unless the patient has symptomatic
vitamin D deficiency
BOMSS Guidelines on perioperative and postoperative biochemical monitoring and
micronutrient replacement for patients undergoing bariatric surgery September 2014
21
Table 4 Postoperative blood tests following sleeve gastrectomy / gastric bypass /duodenal switch. Key
Duodenal switch - DS
Blood test / Procedure
Frequency
HbA1c and/or FBG in patients with preoperative diabetes
Sleeve Gastrectomy/ Gastric Bypass / DS
Monitor as appropriate
Lipid profile
Sleeve Gastrectomy / Gastric Bypass / DS
Monitor in those with dyslipidaemia
U+E, LFT, FBC, ferritin, folate, calcium, vitamin D, PTH
Sleeve Gastrectomy/ Gastric Bypass / DS
3, 6 and 12 months in first year.
Annually
Thiamine
Sleeve Gastrectomy/ Gastric Bypass / DS
Routine blood monitoring of thiamine is not required but clinicians
should be aware that patients with prolonged vomiting can develop
acute thiamine deficiency, which requires urgent treatment (see
elsewhere).
Vitamin B12
Sleeve Gastrectomy/ Gastric Bypass / DS
6 and 12 months in first year.
Annually
No need to monitor if patient has intramuscular vitamin B12 injections
Zinc, copper
Gastric bypass / DS
Annually.
Monitor zinc if unexplained anaemia, hair loss or changes in taste
acuity.
Monitor copper if unexplained anaemia or poor wound healing. Note
the zinc levels affect copper levels and vice versa
Vitamin A
Gastric Bypass
DS
Measure if concerns regarding steattorrhoea or symptoms of vitamin
A deficiency e.g. night blindness
Annually
May need to monitor more frequently in pregnancy
Vitamin E, K
Gastric Bypass / DS
Measure vitamin E if unexplained anaemia, neuropathy.
Consider measuring INR if excessive bruising / coagulopathy as may
indicate vitamin K deficiency
Selenium
Gastric Bypass / DS
Monitor if unexplained fatigue, anaemia, metabolic bone disease,
chronic diarrhoea or heart failure
BOMSS Guidelines on perioperative and postoperative biochemical monitoring and
micronutrient replacement for patients undergoing bariatric surgery September 2014
22
Vitamin and mineral supplements following bariatric surgery
This assumes:
• Patients have received a comprehensive preoperative assessment and any nutritional deficiencies
have been treated
• Patients have biochemical monitoring as stated in the guidelines and have deficiencies investigated
and corrected
• Patients are taking the minimum supplements required
BOMSS Guidelines on perioperative and postoperative biochemical monitoring and
micronutrient replacement for patients undergoing bariatric surgery September 2014
23
Table 5 Vitamin and mineral supplements following gastric balloon
Vitamin and minerals recommended
Multivitamin and mineral supplement
Forceval or over the counter “complete” multivitamin and mineral
supplement, one daily
Thiamine
If patient experiences prolonged vomiting always prescribe
additional thiamine (thiamine 200–300 mg daily, vitamin B co
strong 1 or 2 tablets, three times a day) and urgent referral to
bariatric centre. Those patients who are symptomatic or where
there is clinical suspicion of acute deficiency should be admitted
immediately for administration of IV thiamine
Vitamin D, Iron
Continue with maintenance doses if required
Table 6 Vitamin and mineral supplements following gastric band
Vitamin and minerals recommended
Multivitamin and mineral supplement
Preconception and pregnancy
Forceval or over the counter “complete” multivitamin and mineral
supplement, one daily
Additional folic acid (5 mg) preconception and first 12 weeks of
pregnancy. Safe to continue with Forceval as vitamin A is in beta
carotene form or consider pregnancy multivitamin and mineral e.g.
Seven Seas Pregnancy, Pregnacare, Boots Pregnancy Support
Thiamine
If patient experiences prolonged vomiting always prescribe
additional thiamine (thiamine 200–300 mg daily, vitamin B co strong
1 or 2 tablets, three times a day) and urgent referral to bariatric
centre. Those patients who are symptomatic or where there is
clinical suspicion of acute deficiency should be admitted immediately
for administration of IV thiamine
Vitamin D, Iron
Continue with maintenance doses if required.
BOMSS Guidelines on perioperative and postoperative biochemical monitoring and
micronutrient replacement for patients undergoing bariatric surgery September 2014
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Table 7 Vitamin and mineral supplements following gastric bypass and sleeve gastrectomy
Vitamin and minerals recommended
Multivitamin and mineral supplement should
include;
iron
selenium
2 mg copper (minimum)
zinc (ratio of 8-15 mg zinc for each 1
mg copper
Preconception and pregnancy
The following meet these requirements (August 2014):
• one daily Forceval (soluble and capsule)
• “Over The Counter” complete multivitamin and mineral supplement,
two daily e.g. Sanatogen A-Z Complete, Superdrug A-Z multivitamins and
minerals, Tesco Complete multivitamins and minerals, Lloydspharmacy A-Z
multivitamins and minerals
Safe to continue with Forceval as vitamin A is in beta carotene form or consider
pregnancy multivitamin and mineral e.g. Seven Seas Pregnancy, Pregnacare,
Boots Pregnancy Support
Iron
45 to 60 mg daily
100 mg daily for menstruating women
200 mg ferrous sulphate, 210 mg ferrous fumarate or 300 mg ferrous gluconate
daily
200 mg ferrous sulphate or 210 mg ferrous fumarate twice daily
Folic acid
Contained within multivitamin and mineral
supplement
Pregnancy and preconception.
Encourage consumption of folate rich foods
If deficient, check compliance with multivitamin and mineral supplement. If
compliant, check for vitamin B12 deficiency before recommending additional
folic acid supplements. Additional folic acid (prescribed or over the counter) if
deficient. Recheck folate levels after 4 months.
Additional folic acid (5 mg, but see text) preconception and first 12 weeks of
pregnancy
Vitamin B12
Intramuscular injections of 1mg vitamin B12 three monthly
N.B. sleeve gastrectomy patients may need less frequent injections
Calcium and Vitamin D
Ensure good oral intake of calcium and vitamin D rich foods
Continue with maintenance doses of calcium and vitamin D as identified
preoperatively
Treat and adjust vitamin D supplementation in line with National Osteoporosis
Society Guidelines. Patients are likely to be on at least 800 mg calcium and 20
mcg vitamin D e.g. Adcal D3, Calceos, Cacit D3, however many patients will
require additional vitamin D
Fat soluble vitamins A, E and K
Sufficient contained within vitamin and mineral supplement
Additional fat soluble vitamins may be needed if patient has steatorrhoea
Zinc and copper
Sufficient contained within multivitamin and mineral supplement
If additional zinc is needed, ratio of 8 to 15 mg zinc per 1 mg copper must be
maintained
Selenium
Sufficient contained within multivitamin and mineral supplement.
If required, additional selenium may be provided by two to three Brazil nuts a
day or by over the counter preparations including Selenium ACE, Holland and
Barrett Selenium, Boots Selenium with Vitamins A, C and E
Thiamine
Sufficient contained within multivitamin and mineral supplement.
If patient experiences prolonged vomiting always prescribe additional thiamine
(thiamine 200–300 mg daily, vitamin B co strong 1 or 2 tablets, three times a
day) and urgent referral to bariatric centre. Those patients who are
symptomatic or where there is clinical suspicion of acute deficiency should be
admitted immediately for administration of IV thiamine
BOMSS Guidelines on perioperative and postoperative biochemical monitoring and
micronutrient replacement for patients undergoing bariatric surgery September 2014
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Table 8 Vitamin and mineral supplements following duodenal switch
Vitamin and minerals recommended
Multivitamin and mineral supplement
should include;
• iron
• selenium
• 2 mg copper (minimum)
• zinc (ratio of 8-15 mg zinc for
each 1 mg copper)
Preconception and pregnancy
The following meet these requirements (August 2014):
• one daily Forceval (soluble and capsule)
• “Over The Counter” complete multivitamin and mineral supplement, two daily
e.g. Sanatogen A-Z Complete, Superdrug A-Z multivitamins and minerals, Tesco Complete
multivitamins and minerals, Lloydspharmacy A-Z multivitamins and Minerals
Safe to continue with Forceval as vitamin A is in beta carotene form or consider
pregnancy multivitamin and mineral e.g. Seven Seas Pregnancy, Pregnacare,
Boots Pregnancy Support
Iron
45 to 60 mg daily
100 mg daily for menstruating women
200 mg ferrous sulphate, 210 mg ferrous fumarate or 300 mg ferrous gluconate daily
200 mg ferrous sulphate or 210 mg ferrous fumarate twice daily
Folic acid
Contained within multivitamin and mineral
supplement
Preconception and pregnancy.
Encourage consumption of folate rich foods
If deficient, check compliance with multivitamin and mineral supplement. If compliant,
check for vitamin B12 deficiency before recommending additional folic acid supplements.
Additional folic acid (prescribed or over the counter) if deficient. Recheck folate levels
after 4 months.
Additional folic acid (5 mg, but see text) preconception and first 12 weeks of pregnancy
Vitamin B12
Intramuscular injections of 1mg vitamin B12 three monthly
Calcium and Vitamin D
Ensure good oral intake of calcium and vitamin D rich foods
Continue with maintenance doses of calcium and vitamin D as identified preoperatively
Treat and adjust vitamin D supplementation in line with National Osteoporosis Society
Guidelines. Patients are likely to be on at least 800 mg calcium and 20 mcg vitamin D
e.g. Adcal D3, Calceos, Cacit D3, however most patients will require additional vitamin D
Fat soluble vitamins A, E and K
Additional fat soluble vitamins are needed
AquADEKs Softgels provide additional high doses of fat soluble vitamins A, D, E and K and
other vitamins and minerals. Recommend one to two daily. Alternatively supplement
with additional vitamins A, E and K as required
Zinc and copper
Sufficient contained within multivitamin and mineral supplement
If additional zinc is needed, ratio of 8 to 15 mg zinc per 1 mg copper must be maintained
Selenium
Sufficient contained within multivitamin and mineral supplement
If required, additional selenium may be provided by two to three Brazil nuts a day or by
over the counter preparations including Selenium ACE, Holland and Barrett Selenium,
Boots Selenium with Vitamins A, C and E
Thiamine
Sufficient contained within multivitamin and mineral supplement
If patient experiences prolonged vomiting always prescribe additional thiamine (thiamine
200–300 mg daily, vitamin B co strong 1 or 2 tablets, three times a day) and urgent
referral to bariatric centre. Those patients who are symptomatic or where there is
clinical suspicion of acute deficiency should be admitted immediately for administration
of IV thiamine.
BOMSS Guidelines on perioperative and postoperative biochemical monitoring and
micronutrient replacement for patients undergoing bariatric surgery September 2014
26
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