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 micronutrient replacement for patients undergoing bariatric surgery September 2014

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 (3941). 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 postoperative care for many patients undergoing bariatric surgery, since bariatric surgery is increasingly advocated to improve important obesity-related medical co-morbidity such as
BOMSS Guidelines on perioperative and postoperative biochemical monitoring and micronutrient replacement for patients undergoing bariatric surgery September 2014

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 4050% (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 comorbidity 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.
BOMSS Guidelines on perioperative and postoperative biochemical monitoring and micronutrient replacement for patients undergoing bariatric surgery September 2014

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.
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 micronutrient replacement for patients undergoing bariatric surgery September 2014

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
BOMSS Guidelines on perioperative and postoperative biochemical monitoring and micronutrient replacement for patients undergoing bariatric surgery September 2014

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 form1 (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
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. 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
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 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).

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