Perioperative management of bariatric surgery patients: Focus on metabolic bone disease
ABSTRACTChronic vitamin D deficiency, inadequate calcium intake, and secondary hyperparathyroidism are common in obese individuals, placing them at risk for low bone mass and metabolic bone disease. After bariatric surgery, they are at even higher risk, owing to malabsorption and decreased oral intake. Meticulous preoperative screening, judicious use of vitamin and mineral supplements, addressing modifiable risk factors, and monitoring the absorption of key nutrients postoperatively are essential in preventing metabolic bone disease in bariatric surgery patients.
KEY POINTS
- Metabolic bone disease in obese patients is multifactorial: causes include sequestration of vitamin D in the adipocytes, inadequate nutrition due to chronic dieting, and lack of physical activity.
- Before bariatric surgery, one must look for and treat preexisting nutritional deficiencies.
- In the immediate postoperative period, aggressive strategies (ie, giving multivitamins and minerals intravenously and orally) can prevent nutritional deficiencies and secondary bone disease.
- Postoperatively, many bariatric patients require chewable or liquid supplements to facilitate adequate absorption.
- Clinical suspicion, timely interventions, and lifelong monitoring can prevent metabolic bone disease in bariatric surgery patients.
Preoperative assessment
We recommend obtaining baseline biochemical indices, including albumin, 25-hydroxy-vitamin D, calcium, magnesium, phosphorus, alkaline phosphatase, folate, vitamin B12, thyroid-stimulating hormone, and PTH levels, and DXA in all bariatric surgery candidates. These indices should be used to assess for primary and secondary metabolic bone disease, to enable prompt presurgical interventions, and to guide the clinician in selecting appropriate postoperative interventions and surveillance.
We recommend starting a multivitamin with minerals at the first preoperative visit. A calcium supplement that provides calcium and vitamin D appropriate to the patient’s age and sex is also recommended until surgery. After surgery, and while rapid weight loss is occurring, a minimum of 1,800 mg of calcium and 800 to 1,000 IU of vitamin D is recommended, keeping in mind that the required level of supplemental vitamin D during periods of rapid weight loss remains unclear.68,69
However, before prescribing supplementation, one should thoroughly review the patient’s nutrition history, including the use of homeopathic medications, herbal preparations, and supplements. Many over-the-counter and over-the-Internet supplements are touted as being good for bone health, and some may indeed be beneficial, but others can be detrimental and need to be discontinued.27,47 Furthermore, in a patient with a severely restricted stomach capacity, it is important to ensure that less efficacious supplements do not compromise the intake of essential fluids, protein, and prescribed medications.
Immediate postoperative period
Hospitalization and surgery result in nutrient deficiencies. In bariatric surgery patients, particularly those who have preoperative nutritional deficiencies, repletion in the immediate postoperative period is believed to be of benefit. Therefore, in the immediate postoperative period we recommend infusing a standard-dose multivitamin with minerals daily along with adequate intravenous hydration until the patient can resume oral feeding. Once the patient can tolerate liquids, presurgical supplementation needs to be resumed, preferably in a liquid or chewable form to facilitate tolerance and absorption.
Short-term and long-term follow-up
Follow-up visits with a bariatric specialist should start 4 weeks after surgery and should be repeated every 3 to 4 months for the first year. If the patient continues to do well, annual visits may be sufficient thereafter. Compliance with supplements should be checked as indicated, as should nutritional indices. DXA should be repeated every 1 to 2 years, depending on the patient’s risk profile.
WHAT SHOULD BE DONE FOR OUR PATIENT?
Initial treatment for the patient described at the beginning of this article should include vitamin D repletion with cholecalciferol 50,000 IU, calcium supplements of at least 1,200 mg daily, and addressing of modifiable risk factors for fracture, including the risk of falling due to her proximal weakness. Her laboratory studies should be repeated in 6 to 12 weeks, with calcium and vitamin D supplement dosages adjusted on the basis of her response. Once the serum calcium level has normalized, we would consider the use of a bisphosphonate. DXA should be repeated in 1 to 2 years to monitor the effectiveness of the prescribed interventions.
