Anorexia Nervosa Flashcards
What is anorexia nervosa and how does it present?
Key features:
Weight loss, typically via restriction of caloric intake (‘restricting type’). Can also be of a binge/purge type, involving behaviours such as vomiting, intense exercise, or laxative use.
Results in weight less than 85% of that expected, or BMI <17.5. BMI <14 is severe, 14-17 is moderate, and >17 is mild.
Fear of weight gain.
Feeling fat when thin.
Endocrine dysfunction: amenorrhea for 3 months, or ↓libido in men.
Other features:
Mental state: fatigue, impaired cognition due to cerebral atrophy, altered sleep.
Sensations: cold sensitive, dizzy.
CV: arrhythmias due to hypokalaemia, heart failure. Hypokalaemia is usually a consequence of purging behaviour.
Sexual: psychosexual problems, ↓fertility.
GI: constipation.
Skin: dry skin, fine body hair (lanugo).
Bone: osteoporosis, dental caries.
Obs: ↓temperature, ↓BP, ↓HR.
What are the risk factors for developing anorexia nervosa?
Demographic: 4 times commoner in women, and commonest in teens and 20s.
Family history of anorexia.
Co-morbid depression, anxiety, OCD, or substance abuse.
Personality: ↓self-esteem, perfectionism.
Social pressures: TV watching, image-aware work.
Adverse life events.
Which differentials should be considered in someone presenting with symptoms of anorexia nervosa?
Psychiatric: eating disorders, depression, OCD.
GI disease: IBD, coeliac.
Endocrine: thyrotoxicosis, hypothalamic tumour.
Which investigations should be done in anorexia nervosa?
Use the SCOFF screening tool in those whom you suspect of an eating disorder.
Measure weight and height.
Bloods:
TFT and ESR to exclude other causes of weight loss. T3 may be low due to AN itself, though TSH and T4 should be normal.
FBC may show ↓Hb, ↓WBC, and/or ↓platelets.
LFT: may be mild enzyme elevations.
Sex hormones: ↓E2 in females, ↓testosterone in males.
Other investigations:
ECG: ↑QT interval.
DEXA if amenorrheic: osteopenia and osteoporosis.
Metabolic effects:
↓K+ from vomiting or laxatives.
Alkalosis from vomiting, or acidosis from laxatives.
↑Urea and ↑creatinine due to hypovolaemia.
↓Glucose.
Also: ↓Mg2+, ↓PO43-, ↓Ca2+.
Albumin is a poor marker of nutritional status and is usually normal in anorexia.
How can anorexia nervosa be managed?
Overview:
Most patient care should be delivered in the outpatient setting. Mild anorexia (BMI >17), can be managed in primary care if stable.
Patients are often resistant to treatment, which creates particular challenges.
Weight gain is a key aim in underweight patients. Aim for 0.5 kg/week in the outpatient setting, corresponding to around 5000 extra calories.
See bulimia nervosa page for information on the management of purging behaviours.
Biopsychosocial approach
Biological:
Physical health should be monitored regularly, primarily by weighing, either in secondary care or annually by the GP when stable.
Drug treatment does not work for AN itself, but it may be used for co-morbid depression or OCD. Fluoxetine is the most commonly used drug. Beware effects on cardiac function, and avoid if there are electrolyte imbalances or bradycardia.
Psychological:
Psychoeducation for patients and family.
Structured eating plan with input from a dietician.
Enhanced CBT (CBT-E) is specifically designed for eating disorders. Weekly sessions for 20 weeks, or 40 weeks if BMI <17.5. Aims to establish regular eating habits, then to identify and address harmful ideas about body size and eating, as well as triggers and stressors. Usually delivered individually, but for inpatients it might also involve group sessions.
Family therapy should be used in children, and can be considered in adults if CBT-E fails.
Other options are cognitive analytic therapy, interpersonal therapy, and psychodynamic therapy.
In mild anorexia, self-help treatment might be sufficient.
Social:
Self-help and support groups for families.
When should admission for anorexia nervosa be considered?
Admission:
As with any mental illness, this is required when there is a serious risk to the individual’s health. This typically involves rapid or severe weight loss (BMI <14), severe electrolyte imbalances, cardiac problems, or high suicide risk.
Treatment can also be given on a day patient basis.
Wherever possible, treatment should be voluntary, but compulsory treatment may be needed.
Restore weight:
Refeed with dietician input. Start on current intake and increase by 200 calories every 2 days, eventually aiming to gain 0.5-1.0 kg/week. Ensure adequate fluid intake, around 2 L/day.
Oral feeding if possible, otherwise NG tube. Avoid TPN, unless there is GI dysfunction.
Bed and chair rest with 1 to 1 obs to prevent microexercise (e.g. fidgeting). Use wheelchair if they need to go outside the ward. Monitor during meals to ensure food is not hidden.
Electrolyte replacement – most commonly K+ – and multivitamins.
Try and avoid laxatives, but if constipated, use stool softeners.
Getting the weight back prevents short-term compilations, but remember that this doesn’t fix the underlying problem.
Inpatient monitoring:
Important to check for treatment efficacy and complications such as re-feeding syndrome.
Daily weighing to calculate BMI: same scales, same clothing, with jewellery etc. removed. Ensure there is no prior fluid loading.
Basic obs, glucose, and fluid balance.
Daily bloods: FBC, LFT, U&E, PO43-, Ca2+, Mg2+, CK, TSH.
Daily ECG.
Sepsis screen if indicated, due to infection risk.
Legal framework for compulsory treatment:
Can be done under Sections 2 or 3 of the Mental Health Act, or under the Mental Capacity Act.
When BMI is very low e.g. <12.5, patients are generally thought to lack capacity so can be treated in their best interests. However, once their weight increases above that level, the legal framework for treatment needs to be reviewed and they may need to be sectioned.
What does the prognosis look like in anorexia nervosa?
Most recover to some extent.
Around 30% have a chronic or relapsing course.
10% mortality: usually suicide, ↓K+, or long QT.
What is refeeding syndrome?
Pathophysiology
Caused by re-feeding for anorexia treatment, malnutrition, or GI disease or surgery. Can be due to oral, enteral, or parenteral feeding.
Typically presents in first 5 days.
↓PO43- and fluid shifts lead to multiorgan problems.
Signs and symptoms
↓PO43-:
Rhabdomyolysis
Respiratory or cardiovascular failure, ↓BP.
Delirium, seizures, and coma.
Also signs of hypokalaemia and hypomagnesaemia.
How can the risk of refeeding syndrome be minimised?
Monitoring and prevention
Regular obs, and regular bloods, looking for ↓PO43- (checking Ca2+ too), ↓Mg2+, ↓K+.
Minimized through gradual refeeding and correction of electrolyte imbalances.
What is the SCOFF screening tool?
SCOFF screening tool
Score 1 for each, with ≥2 indicating possible anorexia or bulimia:
Make yourself Sick because you feel full?
Worry you have lost Control over how much you eat?
Recently lost One stone in 3 months?
Believe you’re Fat when others say thin?
Food dominates your life?
